Category Archives: Flavor

Botany lab of the month – August edition: Rocky Top Corn Soup

It’s August, and everyone from the American Midwest knows that late summer means fresh sweet corn, and a lot of it. When I was growing up in Indiana, every few days during corn season we would pick up a dozen ears from my family’s favorite roadside stand, just hours after harvest, and cook them right away, before the kernels could start converting their sugar into starch.

Corn season typically peaked the final week of the Indiana State Fair, which always fell between my sister’s birthday and mine. We felt like the whole world was celebrating with us since the Indiana State Fair really is just a giant party, with rides and games and food and music and anatomically impressive hogs. So every year we went to revel in the indulgent atmosphere of the fair alongside thousands of unbridled Hoosiers from all over the state sweating in tank tops and showing off their best pickles. But I most looked forward to the corn. The fair was littered with vendors serving huge ears of fresh-picked local corn straight from a grate set up over a large open flame. As soon as the charred husks were cool enough to peel back into a handle, we sidled up next to our fellow Hoosiers at a trough (literally a trough) of hot melted butter and plunged the roasted ears into it, right up to the hilt. Then we gave them a generous coating of salt from oversized aluminum shakers, passed from hand to greasy hand around the trough and down the line to us. Best birthdays ever.

For this month’s botany lab, I have created a cold summer soup that is as much a celebration of decadent State Fair food as an homage to the millennia of cultivation and adaptation that makes that food possible. The soup features corn four ways, and its various ingredients are available to us only because people have been growing corn (more accurately, maize) and creating distinct varieties for a very long time over an unusually wide geographical area. Maize as a crop goes back to Mesoamerica about 9 thousand years ago, and it had become a substantial part of people’s diets there by about 4500 years ago (Kennet et al. 2020). The spread of maize throughout much of North America was slow because the right mutations had to arise before Native Americans could select for genotypes that were well suited to the local day length, season length, and altitude (Doebley 1990). In the process, people created the varieties we know now, including those in the soup: sugary sweet corn, eaten while immature; dent corn, with soft starchy kernels good for grinding into fine cornmeal, masa, and grits; and flint, with hard round starchy kernels that can be popped or ground into polenta.

Photo of a bowl of cold corn soup with bourbon-infused grits croutons and popcorn — Cold corn soup with bourbon-infused grits croutons and popcorn

The Indiana State Fair and its unabashed celebration of big agriculture most probably sits atop ancient hand-tended corn fields. It is important to recognize that the Fairgrounds occupy land that was traditionally held by the Miami Tribe of Native Americans and lost through a series of coercive treaties in the 19th century. Many members were forced to relocate, but not all, and the Miami Nation of Indiana maintains a cultural presence in the state. The many indigenous tribes throughout the region have a long tradition of agriculture, and as far back as a thousand years ago people would have made corn (Zea mays) the main staple of their diet (Emerson et al. 2020).

Now that corn is big business in the US, dent corn is the most widely grown type because it is used for animal feed, corn oil, high fructose corn syrup, and the many processed foods that have become modern dietary staples. The luckiest dent corn, however, ends up as mash to be fermented into bourbon, which brings me to the name of the soup.

photo of the horse Rocky Top. Credit Sara Baggett Preston — Good old Rocky Top. Photo: Sara Baggett-Preston

When I was about to turn 13, my mother, who grew up riding, brought a horse into the family. He was a big palomino named Rocky Top, with a mane the color of corn silk and some Tennessee Walker genes that occasionally showed themselves. Naturally, the Osborne Brothers’ song “Rocky Top” was a favorite in our house, especially since my father was, as he described himself, a “tolerable” bluegrass musician who could sometimes be coaxed into singing it.

Corn won’t grow at all on Rocky Top,
Dirt’s too rocky by far.
That’s why all the folks on Rocky Top
Get their corn from a jar

In the song, Rocky Top is an idyl somewhere down in the Tennessee hills. Personally, when I drink corn from a jar, I choose a nice aged bourbon from Kentucky, but that’s beside the point. As long as it’s mostly corn, with just a bit of rye and barley, I’m happy.

This cold late-summer soup features corn four ways, with different flavors and botanical properties that will be obvious as you prepare it. Observation notes are included in the recipe. Like vendors at the Indiana State Fair, this soup plays around in the corners of midwestern and southern food traditions and comes up with something new and delicious. The fresh raw corn base is almost dessert like while croutons of bourbon-soaked grits add intense corn flavor infused with smoke and caramel, and a scattering of buttered popcorn balances the sweet creamy texture of the soup with salty crunch. The soup’s name, of course, honors the inimitable Rocky Top, who was a beloved equine member of our family for over thirty years. The croutons and popcorn might even remind you of rocky outcrops in the Tennessee hills.

Rocky Top soup with corn four ways

Serves 4-6

The preparation is simple, but leave ample time to cook the stock and grits and to chill the ingredients at various stages.

Ingredients

6 large or 8 medium ears of fresh sweet corn in the husk, preferably from a local farm stand or farmers market and as recently picked as possible

1/2 cup of uncooked grits, stone-milled if available, but definitely not “quick”

1/2 cup bourbon (corn in a jar)

1/4 cup unpopped popcorn

Salt (both regular and smoked, if you’ve got it)

Black pepper

White pepper (optional)

1 stick of butter (or olive oil for a vegan version)

Cold soup base

This part of the recipe is quick; my observation notes are long.

1. Before removing the husks, use a large knife to cut the top inch or two from each ear. If insect larvae have gotten into the ears, this is where they will be, and you may prefer not to see them.

2. Remove the husks, which are leaves enclosing the bud of a giant flowering stalk. Notice their shape and the arrangement of their veins, then take a look at the short bit of stem at the base of the ear to see its scattered vascular bundles. Corn (Zea mays) is typical of monocots in having long narrow leaves with parallel veins and vascular bundles scattered throughout its stems (not in a clear ring). Wash and save the tender inner layer of husks for the stock.

3. Look closely at the corn silk and notice that the strands seem to originate from between the kernels. That is because each one is (or was) attached to the top side (the side facing the tip end) of a single kernel. Amazingly, a strand of silk is the extremely long stigma and style through which germinated pollen grains traveled to fertilize the cells inside what is now a kernel. Sometimes you can see that the silk strand is rough or slightly hairy on one side, the better to capture pollen with. (For more details, see Jeanne’s terrific essay, Super Styled.)

Close up of corn silk, showing pollen-catching hairs. Click to enlarge.

4. Rub the ear under water to remove as much silk as possible. Their race is run, and their job is done.

5. Take a moment to appreciate that each kernel of corn on a cob was once a flower, embedded alongside other flowers in a thick flowering axis. The flowers never had functioning sepals or petals or stamens. (Separate stamen-bearing flowers make the pollen and are found in a tassel on top of the plant). Each flower was essentially a single pistil: an ovary with a style and stigma (those silks!) long enough to protrude beyond the husks where it pollen could find it. The mature product of an ovary is a fruit, so it follows that a kernel of corn is a fruit, not a seed. The fruit functions as a seed, however, because it is essentially just a thin wall fused tightly to the single large seed inside. This type of fruit is called a caryopsis (or, simply, a grain). Fresh corn on the cob is immature, and the fruits are soft, but they would become hard if allowed to mature.

The attachment points of the corn silks (super long styles and stigmas!) are clearest where kernels are uncrowded, near unpollinated flowers. Click to enlarge

6. Cut the kernels off the cobs and into a bowl. First, cut the cobs in half, then stand them on their cut ends and run a large knife down the sides to remove the kernels. When all kernels have been removed, pull the knife blade across the cobs over the bowl to pull out any residual “milk” (actually endosperm, described below).

kernels cut from a cob to show embryo — The corn embryo is embedded in sweet soft endosperm. The kernel is surrounded by a fringe of paleas, lemmas, and glumes.

7. Notice the very small opaque flattened round structures that pop out of the cut kernels and milked juice. These are embryos. The milky juice is endosperm, the tissue that would supply the embryo with energy and nutrients during germination. At this stage, most of the endosperm is soft and some is still liquid. The liquid portion contains many nuclei because it has not yet been divided into walled cells. Refrigerate the bowl of kernels until the stock has been made and cooled.

8. Look closely at one of the empty cobs. Notice that the sockets that once held kernels are ringed with short papery ruffles. These structures – paleas, lemmas, and glumes– are evidence that the corn cob is much more complicated than it seems. Those empty sockets held not one but two corn flowers, one of which simply never developed. The flower pairs were borne on a very tiny branch with two short glumes at its base. Each flower, in turn, was enclosed by a pair of thin structures, one palea and one lemma. The raggedy ruffles are glumes and paleas and lemmas and are left behind when you eat corn off the cob or shave off the kernels with a knife.

9. Place the cobs and the reserved tender husks into a saucepan, add water to barely cover them, and simmer for about 30 minutes to make a stock. Remove the cobs and husks and allow the stock to cool to room temperature.

10. Move the kernels and milky endosperm from the bowl into a blender and add about 1/4 cup of the stock. Blend very well until the soup is a fine silky purée. Add small amounts of the stock as needed to ease the blending and achieve the consistency you prefer. Salt very sparingly; you want to retain the grassy sweetness of the raw fresh corn. Chill thoroughly.

This soup should be made no more than a day ahead for peak flavor. It is raw and may start to ferment after several days.

Grits croutons

In a pinch, you can use polenta, but the texture will be less interesting and the cuisine will be less American.

1. Place the grits and the bourbon in a heavy-bottomed saucepan, and allow the grits to soak for 30 minutes.

2. Notice that grits, especially traditional stone milled grits, vary much more in particle size than polenta does. Could that be why most people treat “grits” as plural and “polenta” as a singular mass noun? It won’t be obvious, but grits are generally made of dent corn and polenta is made of harder flint corn.

4. Add a tablespoon of butter, a teaspoon of salt, and several grinds of white pepper (about 1/4 teaspoon). If you have smoked salt available, use it here.

3. Cook according to the directions for your particular grits. If you have leftover corn cob stock, use it, supplementing with water if needed.

4. Continue to cook and stir the grits until they are thoroughly done and very thick, like mashed potatoes. You may need to cook longer than directed to get the grits thick enough.

5. Spread the grits into a couple of buttered loaf pans or a square cake pan and chill them for at least an hour, until they are well set. The grits should be about half an inch thick in the pan.

6. Use a table knife to cut the chilled grits into one-inch squares and turn them out into a roasting pan. Toss them with soft butter or olive oil and bake them at 350º for 20 minutes or until crispy on the outside. (It is also possible to fry them in a pan, but they tend to fall apart because they are more fragile than polenta squares.)

7. Croutons should be room temperature or warm but not hot when you serve the soup. You want to keep the soup cool. Croutons may be reheated if needed.

Popcorn topping

1. Notice that popcorn is hard because it has been allowed to mature before harvest, and the once liquid endosperm has been divided into separate cells containing the previously free floating nuclei. Popcorn is a variety of flint corn, so it has a round end without the depressed center seen in dent corn. The nutritive endosperm of popping corn is much starchier than sweet corn would ever get. Although popcorn seems very dry, there is some residual water inside. When heated, that water becomes steam and swells the starch until it bursts the kernel open.

2. Pop the popcorn using your favorite method. Admire the fluffy white expanded endosperm.

2. Butter and salt the popcorn generously, using about 4 tablespoons of melted butter.

Assembling the soup

1. Pour the chilled soup into bowls

2. Scatter several grits croutons over the soup. Most will sink

3. Top generously with popcorn and grind some black pepper over the top

4. Serve immediately to maintain the contrasts in temperature and texture

References and resources

My favorite sources of stone-milled grits are Anson Mills and Nora Mills. Anson Mills also sells popcorn and their website has several interesting pages about the history and botany of the foods they mill.

Doebley, J. (1990). Molecular evidence and the evolution of maize. Economic Botany, 44(3), 6-27.

Doebley, J. F., Goodman, O. M., & Stuber, C. W. (1986). Exceptional genetic divergence of northern flint corn. American Journal of Botany, 73(1), 64-69.

Emerson, T. E., Hedman, K. M., Simon, M. L., Fort, M. A., & Witt, K. E. (2020). Isotopic confirmation of the timing and intensity of maize consumption in greater Cahokia. American Antiquity, 85(2), 241-262.

Kennett, D. J., Prufer, K. M., Culleton, B. J., George, R. J., Robinson, M., Trask, W. R., … & Gutierrez, S. M. (2020). Early isotopic evidence for maize as a staple grain in the Americas. Science Advances, 6(23), eaba3245.

Nickerson, N. H. (1954). Morphological analysis of the maize ear. American Journal of Botany, 87-92.

Weatherwax, P. (1916). Morphology of the flowers of Zea mays. Bulletin of the Torrey Botanical Club, 43(3), 127-144.

Mberkery1, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

The adoration of the pine nut

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It’s the winter holiday season, when halls are bedecked with garlands of evergreens, sprigs of holly, and bunches of mistletoe to remind us that there is life in the darkness and love to be shared. This year, Katherine has added another symbolic plant to her own holiday list – pine nuts. They are more precious this year than ever.

I first started using pine nuts in holiday baking for the simple reason that they taste like pine and thus add a Christmas-tree note that almonds do not. A deeper significance was not on my mind. But pine nuts are so interesting botanically that I always slice some of them open to look for tiny pine embryos inside, and that triggers some nostalgia for conifer week in the botany lab I taught as a graduate student (along with the best co-TA ever). Specifically, I think about an odd conversation with one of the students, which for years was nothing but another funny story. Only now, decades later, do I understand that this student’s observations have something to teach us about the true meaning of pine nuts.

The remarkably unfiltered conversation happened after our student, while dissecting a pine nut, had experienced a double epiphany: he finally understood the details of sexual reproduction in pines, and he therein discovered a pathetically apt metaphor for his love life. I can still see the way he dropped his shoulders as dejection slid across his face. His exact words are lost after so many years, but he basically confided to us that, like a pine seed, he always invested a little too much and a little too early in the promise of love (or at least sex) which might never be fulfilled.

Lessons from pine sex

Both pines and flowering plants make seeds, however they don’t feed their embryos the same way. Pines (and other gymnosperms) pack a fat lunch in anticipation of an embryo, whereas flowering plants typically wait for successful fertilization and only then build up a food reserve for the embryo. Pines invest in an uncertain future, while flowering plants hold back and hedge their bets. Our student thought that his was a losing strategy, and that he should behave more like a flowering plant, but I’m not sure. I like to imagine that someone found his earnest vulnerability charming, and that he has found the loving partnership he was looking for. No matter what happened in his case, however, this I now know for certain: sometimes in life you have to muster the courage to invest fully, even recklessly, in hope. I think that’s a pretty good message for the short days of winter.

The full story of pine reproduction starts with the story of seeds, which is very complicated and still not fully resolved, but here it is in a nutshell. Seeds were an incredibly successful evolutionary innovation because they took a process that depended on wet soil or water pooling on bark or in sidewalk cracks and brought it inside a protective shell that remained on the parent plant and could function without free water. The ancestors of seed plants were similar to today’s ferns, in that they shed spores that germinated in moisture and grew into tiny plants that made eggs and swimming sperm. There are variations on this basic system throughout the plant kingdom, but ferns are a familiar example. In ferns, the large frondy generation is called the sporophyte (“spore plant”) because it makes spores. (Spores result from meiosis, so they contain half as many chromosomes per cell as the sporophyte does). Spores germinate and grow into flat green plants about the size of a lentil. These are called gametophytes because they make gametes (eggs and sperm). Under the right conditions, eggs and sperm meet, and the result is a new sporophyte.

A flat-topped Italian Stone Pine (Pinus pinea) on the Stanford campus — The tree in the center is a flat-topped Italian Stone Pine (*Pinus* *pinea*) on the Stanford campus

Pine trees are also sporophytes, but they hold onto their female spores, which develop into egg-producing female gametophytes* inside the seeds on the scales of their cones. The male spores are shed as pollen grains, with sperm-producing cells inside. Whereas free-swimming fern sperm cells get nowhere without a film of water between themselves and some eggs, pine sperm packaged into pollen grains can float through the air towards more distant eggs. Although non-seed plants have done well evolutionarily – mosses and ferns are especially diverse, widespread, and abundant – the seed habit has freed gymnosperms and angiosperms from some ecological constraints and has undoubtedly contributed to their success in a range of habitats.

What is a pine nut?

For all its oily goodness, botanically a pine nut is not a nut at all. It is a seed, and without its shell (the seed coat), a pine nut is essentially nothing but female gametophyte, often with a cute little embryo inside bearing tiny pine needles. Long before it gets to that point, however, the gametophyte has to do what its name calls for – it makes eggs, two of them – and it also accumulates a lot of nutrients for a potential embryo. A typical commercial pine nut is about two-thirds fat by weight and one-third protein and carbohydrates. A tree invests in making hundreds or thousands of those energy-rich structures each season, even though only some of the eggs will be fertilized. I don’t know what proportion of the ovules (immature seeds) are actually fertilized on a typical tree, but in a bag of pine nuts it is sometimes hard to find any with an embryo inside. Other times, most of the seeds I open up do contain baby pines.

Pine nuts are worth dissecting in your kitchen because they give you a rare glimpse into the evolutionary history outlined above. By contrast, you will never see the female gametophyte of a walnut, pecan, almond, hazelnut, peanut, or cashew, at least not in your kitchen. In flowering plants, the female gametophyte has evolved to be just a handful of cells, and when we eat an angiosperm seed, we are eating some combination of embryo and that special made-just-in-time tissue called the endosperm.

Conifer week in your kitchen

Just for auld lang syne, I gathered and photographed some of the materials we might have used during conifer week in botany lab so that you can follow along at home. If you have your own pine nuts, that’s even better. Epiphanies are encouraged but not required.

Commercial pine nuts are harvested from natural stands of a few large-seeded species. European pine nuts come from the Italian stone pine, Pinus pinea, which is planted as an ornamental in other Mediterranean type climates, including, fortunately, the campus of Stanford University where I teach. Squirrels are also a conspicuous part of the flora and fauna at Stanford, and they had already taken most of the seeds out of the cones that I picked up. In fact, pine nut processors usually harvest cones directly from the tree before their scales have opened up, and the cones are allowed to dry at a safe distance from seed predators. Unfortunately, the remaining seeds I found, stuck inside their cones and spurned by the squirrels, had become moldy, so all the photos here of gametophytes and embryos are from pine nuts I bought. Those were harvested in China and came from a different species, the Korean pine (Pinus koraiensis).

Seed poking out from between cone scales

For most of their development – between pollination and seed release – pine cones keep their scales tightly closed. You can usually find cones in various stages of development on a tree because the whole process can take two or three years. When seeds are mature, the scales of most species open up, and the seeds can be seen peeking out from between them.

In pine species with small seeds, there is a prominent wing on each seed, and seeds flutter out away from the parent plant. Italian stone pines have very large seeds whose useless vestigial wings detach from the seeds easily.

The “shell” of a pine nut is nothing but a hard thick seed coat, its only protection against the outside world. This is what it means to be a gymnosperm — a naked seed. By contrast, the shells of other “nuts,” like pecans, almonds, or pistachios are part of the angiosperm fruit wall that surrounds the seeds, and their seed coats are very thin.

Most pine nuts are sold as bare gametophytes, without their seed coats. If you look at their pointed tips you can see a small opening where the pollen grains would have settled in to germinate and send out their pollen tubes. Pine gametophytes make two eggs in special chambers (archegonia), but usually the first egg to be fertilized is the only one that ultimately develops. I have never found twin embryos inside a pine nut, but it does happen. Twinning can also result when one embryo splits lengthwise early in development.

If you have any pine nuts to dissect, it’s best to use a razor blade because kitchen knife blades are a little too thick to do the job without mangling the embryo. A longitudinal section starting at the pointed tip reveals the embryo inside.

Above: row of pine gametophytes with embryos; below: embryos removed from the gametophytes

Here’s where it gets really interesting. Recall that one of the main functions of the female gametophyte, besides making the eggs, is to nourish the embryo. In other words, once the embryo starts to grow, it basically eats the gametophyte. It does this with the help of the suspensor, a column of disposable embryonic cells that push the main part of the new plant forward, into the gametophyte, so that it can absorb its nutrients. Once the embryo has established a distinct leafy end and root end, the root starts to grow back towards the suspensor and it crushes it. You can usually find the stringy dried up suspensor in the mature pine nut.

One of the things that makes pine nut embryos so adorable is the set of tiny needle leaves at their tips. When the embryo becomes a seedling, these will emerge to photosynthesize and take over the job of feeding the young plant.

Pine nuts at Christmas

Italian stone pines (Pinus pinea) are native to the European side of the Mediterranean coast. In Italy they occur on the northern half of both sides of the peninsula and in the heel of the boot. The range continues westward along the southern coast of France and into Spain and Portugal where native stands are scattered throughout the interior (Viñas et al., 2016). Pine nuts were never domesticated and are generally not even cultivated in orchards. They are usually harvested from natural stands, as they have been for tens of thousands of years in Southern Europe. There is even evidence from a Spanish cave that Neanderthals collected and presumably ate P. pinea seeds (Finlayson et al., 2006). Modern humans kept up the practice and many traditional foods from the region feature pine nuts.

Pine nuts have a distinctive conifer flavor dominated by pinene, limonene, hexanal, camphene, and careen (McGee, 2020), and they work well in both savory and sweet dishes where they hold their own against strong herbs and spices. There is of course pesto from Genoa in the heart of pine nut country, but also Italian cakes (pinolata) and Christmas cookies (pignoli). A specialty in parts of Provence is the sweet tarte aux pignons . In Catalonia, All Saints Day (November 1) is celebrated with pine nut confections called panellets. None of these traditional recipes includes chocolate — likely because they predate its arrival into Europe — but I really like to bake with a combination of chocolate, orange, and pine nuts, especially at Christmas.

Puff pastry tart with leeks, bleu cheese, arugula, and pine nuts

Investing in pine nuts

For a pine tree, the substantial energy allocated to female gametophytes is an investment in potential offspring with no guarantee of success. For us, it can be a substantial financial investment that may be increasingly costly for people and the planet as well. Pine nuts have always been more expensive than peanuts or almonds, but their price jumped this year for a variety of reasons (Produce Report). Most pine nuts for sale in the United States come from stands of Korean pine growing in China. There, as everywhere, pine nut processing is unusually labor intensive and even dangerous, as rough heavy cones must be harvested by hand by skilled pickers who can navigate among the branches high above the ground. Seeds are then separated from the awkwardly knobby cones and the seed coats are removed from the female gametophytes. Pandemic-related safety measures and labor shortages have limited production, and the supply chain has been throttled, driving prices even higher. Meanwhile, a warming climate and a damaging insect pest have reduced yields (El Khoury et al., 2021). I’ll confess that I balked at the cost and used local pistachios in place of pine nuts in much of my baking this year.

The more I read about pine nut production the more concerned I became about worker protections and whether pine nut harvesting in natural stands could be sustained in the face of rising global demand. A conservation biologist working in Korean pine forests in Russia has written movingly about these highly diverse and fragile ecosystems, home to rare Amur tigers and other animals, and called for protections (Slaght, 2015).

Since a few western North American species produce large edible seeds, I looked for local harvesters who intentionally support both human and ecological communities. There are at least a couple of them, but neither had any product to sell this year. The future doesn’t look good for these businesses either, given the west’s megadrought and competition from lower-cost Chinese producers. Theirs is an investment against the odds and in favor of conserving an important cultural and ecological heritage.

The message of the pine nut

Besides their piney flavor and rich texture, what can we take from the precious little naked gametophytes that are now on my list of holiday plants? What message do I send to friends and colleagues along with my chocolate orange pine nut cake?

Pines have been around for about 150 million years, and conifers for twice that long (Rothwell et al., 2012, Jin et al., 2021), so their reproductive strategy can’t be that foolish. Their lineage persisted even when an asteroid slammed into our planet, causing the fifth mass extinction. If they don’t survive the Anthropocene, it won’t be because of their sex life. If anything, we should take their lesson to heart now more than ever. We can’t afford to wait until the last minute, like angiosperms do, to invest in future generations. It is time — past time, actually — to muster the courage and the will to dedicate all the resources we can to the preservation of the planet and our place in it. Otherwise, what hope do we have?

*note: Female gametophytes are more accurately called megagametophytes, and they derive from megaspores produced in megasporangia. Male gametophytes are really microgametophytes, pollen grains are microspores, and they are shed from microsporangia. In flowering plants, microsporangia are inside the anthers.

References and further reading

von Arnold, S., Clapham, D., & Abrahamsson, M. (2019). Embryology in conifers. Advances in Botanical Research, 89, 157-184.

El Khoury, Y., Noujeim, E., Bubici, G., Tarasco, E., Al Khoury, C., & Nemer, N. (2021). Potential Factors behind the Decline of Pinus pinea Nut Production in Mediterranean Pine Forests. Forests, 12(9), 1167.

Finlayson, C., Pacheco, F. G., Rodríguez-Vidal, J., Fa, D. A., López, J. M. G., Pérez, A. S., … & Sakamoto, T. (2006). Late survival of Neanderthals at the southernmost extreme of Europe. Nature, 443(7113), 850-853

Jin, W. T., Gernandt, D. S., Wehenkel, C., Xia, X. M., Wei, X. X., & Wang, X. Q. (2021). Phylogenomic and ecological analyses reveal the spatiotemporal evolution of global pines. Proceedings of the National Academy of Sciences, 118(20).

McGee, H. (2020). Nose dive: A field guide to the world’s smells. New York, NY: Penguin Press.

Meade, L. E., Plackett, A. R., & Hilton, J. (2021). Reconstructing development of the earliest seed integuments raises a new hypothesis for the evolution of ancestral seed‐bearing structures. New Phytologist, 229(3), 1782-1794.

Pine Nut prices reach record high. Produce Report. (2022, April 5). Retrieved December 15, 2021, from https://www.producereport.com/article/pine-nut-prices-reach-record-high

Rothwell, G. W., Mapes, G., Stockey, R. A., & Hilton, J. (2012). The seed cone Eathiestrobus gen. nov.: fossil evidence for a Jurassic origin of Pinaceae. American Journal of Botany, 99(4), 708-720.

Rudall, P. J. (2021). Evolution and patterning of the ovule in seed plants. Biological Reviews, 96(3), 943-960.

Slaght, J. C. (2015, October 19). Opinion | Making Pesto? Hold the Pine Nuts. The New York Times. https://www.nytimes.com/2015/10/19/opinion/making-pesto-hold-the-pine-nuts.html

Viñas, R. A., Caudullo, G., Oliveira, S., & de Rigo, D. (2016). Pinus pinea in Europe: distribution, habitat, usage and threats. European Atlas of Forest Tree Species; European Commission: Brussels, Belgium, 204.

The leftovers of 2020

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Do you still have a bunch of celery leftover from Thanksgiving in the back of your fridge? With no holiday parties this year, you won’t be able to sneak it onto a holiday crudités platter. You could assemble silly little peanut butter and celery reindeer snacks, but that would just generate messier leftovers. Katherine tells you why you should put it all into a very elegant silky soup for the grownups.

Some of my happiest teaching days begin when I drag a rattling cartload of vegetables and razor blades over the paving stones and across the quad to my classroom. Then, for a couple of hours, edible roots and stems and leaves are handled, poked, hacked at, licked, bitten into, and passed between lab partners. Some of them become projectiles. Most become snacks right there. Potatoes fall into backpacks to be cooked later in the dorm. By the time we clean up, the scant inedible scraps fit into one small bag that I can tip inconspicuously into a campus compost bin.

It’s hard to imagine those days now. Before the pandemic, the only real potential hazards of these labs were food allergies and dissecting tool injuries. While I did provide hand wipes, nobody used them. Now after nine months of pandemic protocols, even just describing the labs triggers aversion.

Trying to teach botany during a pandemic is exactly why I ended up with leftover celery, and much too much of it. The week before Thanksgiving, Jeanne and I taught a virtual botany lab by video conference with some of the volunteers for the Friends of Edgewood Park. We imagined a plant-based Thanksgiving dinner and walked the volunteers through each of the main plant ingredients, while they dissected their own samples at home. The participants were good sports, and it was fun, even if nobody started a Brussels sprouts fight.

Celery (left) with close relative fennel (right)

After the event, it was a boon to have the remaining potatoes, sweet potatoes, herbs, leeks, oranges, green beans, and cranberries I had gathered for the demonstration. They were mostly still intact and free from community spittle, and I had plans for each of them. But then there were also those two imposing bundles of celery – stringy, strong tasting, and too long for the fridge. There was nobody I could send them home with. I certainly did not want to eat that much raw celery. Braising it à la Julia Child was no more appealing as I have always hated cooked celery.

Or so I thought. After consulting with Jeanne, a genius with umbel-bearing species, I improvised a basic celery and potato soup and added a little bit of the leftover rosemary. Slow cooking and a whirl in the blender transformed it into something silky and rich and delicious, without any of the strong overcooked green flavor I associate with celery chunks in soup. The recipe is below. But how did this simple treatment completely change the celery flavor?

base of a bunch of celery, showing leaf arrangement

Base of a bunch of celery, trimmed to show leaf arrangement

Fortunately for us all, the amazing Harold McGee has just published an instant classic, Nose Dive: a Field Guide to the World’s Smells. For his book, McGee has compiled table after table of the dominant smells (and their source molecules) for a wide array of vegetables and herbs, including celery. His painstaking work helped me understand why I should stop omitting this complicated species from my mirepoix.

From heavy scented to heaven scented

Raw celery has a fresh green scent to match its crisp texture, but it’s not bland, and it won’t hide behind the rest of the crudités on the platter. Its scientific name is Apium graveolens, and while the genus name has something to do with bees, the species name means “heavy-scented.” Its distinct celery smell comes largely from a volatile molecule called sedanenolide, which is a type of phthalide (McGee 2020). As assertive as it can be, this molecule affects our perception even at concentrations below what we can detect. One study found that a small amount of sedanenolide added to chicken broth raised all eleven measured positive flavor qualities relative to plain broth, as rated by a panel of tasters (Kurobayashi et al. 2008). So in addition to contributing a bit of its own flavor, the sedanenolide in celery boosts our sense that a dish is thick, savory, and complex.

Sedanenolide is not altered chemically by boiling, although it is volatile so some of it probably evaporates when celery is cooked. But cooking celery also transforms some of its chemical components to generate a completely different flavor arising from my new favorite molecule, sotolon.

Sotolon is described as tasting like fenugreek, which may not be helpful information if you have never tasted fenugreek by itself. Fenugreek seeds taste like maple syrup, but with a funky edge that veers into what some authors describe as “curry” at higher concentrations. It reminds me of the faint onion scent that lingers in the wood grain of a well used cutting board.

Fenugreek seeds. Click to enlarge.

Sotolon also contributes warm maple-like flavors to sherry and Madeira wines. I sometimes add it to oatmeal along with cinnamon, cloves, nutmeg, and ginger. You have to be careful with ground fenugreek, though, because the scent remains on your fingers all day, and you don’t want your oatmeal tasting faintly of onions. Reading about sotolon made me crave it, so I spiked some tea with fenugreek, and alongside the maple flavor, I caught occasional hints of celery seed in the steam.

Rosemary

Thanks to McGee’s masterful book, with an incredible index, I learned about some of my soup’s other scents as well. For example, cooked potatoes develop a nutty and earthy flavor because of pyrazines. Of course they also carry some sweetness from the carbohydrates stored in their flesh. Rosemary contains several interesting molecules that give it a resinous camphor scent, but in the soup, the rosemary notes mainly reflected its more woodsy compounds, borneol and peppery rotundone.

Borneol is a monoterpenoid that contributes to the scent of some pines and cypress, as well as ginger and citrus peels (McGee 2020). Rotundone is the sesquiterpenoid molecule that imparts a characteristic black-pepper aroma to Australian shiraz wines, and that’s where it was first discovered in 2008. It has since been identified in (of course) French syrah, some other wine varietals, black pepper, rosemary, basil, and even apple and mango (Geffroy et al. 2020). A substantial proportion of unlucky humans cannot smell rotundone at all. In one panel of French wine professionals and connoisseurs, 31% failed to detect it (Geffroy et al. 2017). Sadly, in COVID times we have all learned the term for this: anosmia.

With all that maple pepper woodsy pine aroma wafting from the bowl, no wonder my simple little three-plant soup turned out to taste like a walk in the woods on a sunny early winter’s day. Not bad for leftovers.

Portion of an advertisement from 1951 for Campbells soup

Portion of a 1952 advertisement from Better Homes and Gardens for Campbells soup. Click to enlarge.

Leftover celery and potato soup

Celery stalks (petioles, the part of the leaf below the flat compound blade)
Unpeeled chopped potatoes, at twice the volume of the celery. I used several small waxy types and a baking potato because they were left over from the virtual lab demonstration. The type may not matter that much
Several tablespoons of butter (1-2 tablespoons per bunch of celery)
Olive oil
Fresh sprig of rosemary, 2-3 inches long
Salt and pepper to taste

Chop celery petioles (“stalks”) and take note of their raw volume. Put the celery and the sprig of rosemary into a large stock pot and cook them slowly and gently in a generous dollop of butter, about one mounded tablespoon for each bunch of celery.

When the celery is very soft and translucent, but not brown, add chopped potatoes. The volume of potato should be about twice that of the raw celery. Add a dash of olive oil and stir for a few minutes but do not brown the vegetables.

Add water to twice the depth of the vegetables and simmer until the potatoes are completely soft. Add salt and pepper.

Remove the rosemary sprig, but leave any leaves that have fallen off of the stem. Let the soup cool and purée it. Reheat to serve and add water to thin if necessary.

I was lucky enough to have some fresh goat cheese flavored with fennel pollen and black pepper from Pennyroyal Farm. I put a quenelle rustique (a plop) of cheese in the bottom of each bowl and poured the soup around it. Fennel is in the same family as celery, but its florets and pollen produce their own lovely set of volatile scents (Ferioli et al. 2017) that complement the celery without replicating it.

References

Ferioli, F., Giambanelli, E., & D’Antuono, L. F. (2017). Fennel (Foeniculum vulgare Mill. subsp. piperitum) florets, a traditional culinary spice in Italy: evaluation of phenolics and volatiles in local populations, and comparison with the composition of other plant parts. Journal of the Science of Food and Agriculture, 97(15), 5369-5380.

Geffroy, O, Descôtes, J., Serrano, E., Calzi, M.L., Dagan, L., & Schneider, R. (2018). Can a certain concentration of rotundone be undesirable in Duras red wine? A study to estimate a consumer rejection threshold for the pepper aroma compound. Australian Journal of Grape and Wine Research 24: 88-95.

Geffroy, O., Kleiber, D., & Jacques, A. (2020). May peppery wines be the spice of life? A review of research on the ‘pepper’aroma and the sesquiterpenoid rotundone. OENO One, 54(2), 245-262.

Kurobayashi, Y., Katsumi, Y., Fujita, A., Morimitsu, Y., & Kubota, K. (2008). Flavor enhancement of chicken broth from boiled celery constituents. Journal of Agricultural and Food Chemistry, 56(2), 512-516.

McGee, H. (2020). Nose dive: A field guide to the world’s smells. New York, NY: Penguin Press.

Sage, rosemary, and chia: three gifts from the wisest genus (Salvia)

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This essay is our annual contribution to the Advent Botany essay collection curated by Alastair Cullham at the University of Reading. We highlight three charismatic species in the large genus Salvia (in the mint family, Lamiaceae): rosemary, sage, and chia.

Two Christmases ago we pointed out the current fad in decorating pineapples for Christmas. This year, some of our gentle readers may come across potted rosemary bushes that are trimmed into a cone to resemble a conifer. These are pleasant and ostensibly can be kept alive after the holiday season.

A rosemary shrub trimmed into a conifer shape. Photo from Pottery Barn.

A perhaps less pleasant holiday botanical encounter may include a Christmas tree-shaped Chia Pet.

Christmas tree Chia Pet. Photo from Amazon.

As far as Chia Pets go, this one is fairly innocuous. In my view, however, its only saving grace is that the chia plant itself is a fabulous taxon (Salvia hispanica), as is the rest of its large genus, Salvia, which also happens to include rosemary (Salvia rosmarinus). Rosemary of course is much more likely to make a holiday appearance as a culinary ingredient than a decoration, lovely as it is. In the kitchen it is frequently joined with its congener Salvia officinalis, usually just called garden sage. That the genus Salvia is responsible for half the taxa in the title of a Simon & Garfunkel album (Parsley, Sage, Rosemary and Thyme), notwithstanding that Art Garfunkel looks like a Chia Pet on the cover, could provide enough taxonomic joy to justify leaving this examination of these plants here. The name “sage”, however, implies wisdom, and so like the wise men of old, I shall persevere.

Parsley, Sage, Rosemary and Thyme album cover by Simon & Garfunkel (1966)

We’ll start by addressing the taxonomic elephant in the room that might otherwise distract learned readers: rosemary was only brought into the Salvia fold in 2017. Before then it was in its own small genus: Rosmarinus. The reason Rosmarinus is now Salvia is that the speciose Salvia was found to be paraphyletic: the pre-2017 conscription of the nearly 1000 species in the genus did not include all of the descendants of their most recent common ancestor. When the relationships between all the Salvia species and their closest relatives were plotted on a single phylogenetic tree, it was obvious that Rosmarinus and a few other genera should more naturally be considered Salvia, and Salvia was revised accordingly.

Rosemary (Salvia rosmarinus)

Another taxonomic bookkeeping item is to clarify that the sages in Salvia are only distant relatives of the sagebrushes and sageworts in the genus Artemisia, which is in the sunflower family Asteraceae (please see our Artemisia essay for more information about that genus, which includes the herb tarragon). The phylogenetic relationships of the major groups in Salvia from the most recent revision (Drew et al., 2017) is shown below.

Figure 2 from Drew et al. (2017): “(A) Composite chronogram of subtribe Salviinae (which contains Salvia and related taxa) based on chloroplast DNA sequences from previous molecular phylogenetic analyses. Asterisks denote nodes with low support and/or conflicting resolution among previous analyses. Salvia nomenclature follows subgeneric clades described here, including three tentatively named clades that await proper circumscription. Calibrations based on Drew & Sytsma (2012; See supplementary figure S4) (B) Circle cladogram framed on larger chronogram with weakly supported nodes collapsed, depicting species diversity and generalized staminal types within each clade of Salvia; modified after Walker & Sytsma (2007) and Walker et al. (2015).” S. elegans (pineapple sage), S. sclarea (clary sage), and S. hispanica (chia) are in the American subgenus Calosphace. Rosemary is in its own subgenus, Rosmarinus.

The phylogenetic diagram above (from Drew et al., 2017) shows locations where the flower anther structure evolved into a lever-like mechanism that aids in bee pollination by physically moving the two stamens into contact with the bee’s back when a bee enters the flower (see illustration below from Walker, Sytsma, Treutlein, & Wink, 2004).

Figure 2 from Walker et al 2004: “Flower and pollination of Salvia pratensis (Salvia clade I). A flower without the lever mechanism activated (A). As the pollinator enters the flower (B), the pollen is deposited on the back of the pollinator. As the pollinator enters an older flower (stamens removed from sketch, but remain present in flower) pollen is transferred (C). The posterior anther thecae forming the lever can be fused or free and in the subg. Leonia, produce fertile pollen”

The lever mechanism independently evolved three times within Salvia. Each of these evolutionary events was followed by rapid and prolific speciation driven by this innovation in pollination biology (Drew et al., 2017): the advent of the lever mechanism led to the radiation of around 500 species in the subgenus Calosphace in Central and South America; around 250 species evolved soon after the advent of the lever mechanism in the Salvia officinalis clade in the Mediterranean and Western Asia; and around 100 species radiated following the lever in Far East Asia in the Salvia glutinosa clade.

Sage (Salvia officinalis) flowering on my deck this summer

The bee-pollinated Salvia flowers are distinct from those pollinated by hummingbirds, which are more elongate and often red, like the flowers of pineapple sage (S. elegans), and have either evolutionarily lost the staminal lever mechanism or never had it in the first place.

Pineapple sage (Salvia elegans)

The parsley, sage, rosemary, and thyme made famous by Simon & Garfunkel started their culinary careers in Europe. All but parsley are in the mint family (Lamiaceae; see our carrot top essay for a discussion of fun chemical relationships between the flavor compounds in the mint family and the parsley family, Apiaceae). This points to the profusion of aromatic mint family species common to the rocky shrublands covering much of Europe and western Asia (Rundel et al., 2016; Vargas, Fernández-Mazuecos, & Heleno, 2018).

Called “tomillar” in spanish, literally a field of wild thyme (Thymus vulgaris) and associated species growing in the Orusco de Tajuña hills (near Madrid. Spain). Other edible Lamiaceae can be found in this plant community, including Salvia rosmarinus, and Lavandula latifolia (a lavendar). Photo by Julia Chacón-Labella.

That broad area is one of the centers of Salvia species diversity, but the genus is globally widespread. The genus probably originated and dispersed first from African and then the Mediterranean (see the figure of Salvia distribution and putative dispersal history below from Will & Claßen-Bockhoff, 2017), but the full story of dispersal and species radiation within the genus requires more elucidation. Numerous species of Salvia are utilized as culinary or medicinal herbs or garden ornamentals throughout its range.

Fig. 8 from Will et al. 2017: “Salvia s.l. in time and space. A: Distribution of Salvia s.l., putative migration routes and fossil sites; BLB = Bering Land Bridge; D = Dorystaechas; M= Meriandra; NALB = North Atlantic Land Bridge; P = Perovskia; R = Rosmarinus; Z = Zhumeria; white arrows indicate repeated colonization of S Africa and dispersal from the Eastern Cape to Madagascar; hatched arrows (dark grey) indicate the repeated colonization of the Canary Islands from two different mainland sources; red arrow illustrate the dispersal from East Asia to Eurasia reflected by S. glutinosa; black arrows correspond to dispersal events from the OW to America reflected by two distinct lineages; ? = route uncertain; template of the map provided by the German earth science portal (www.mygeo.info). B: Simplified phylogenetic tree; nodes discussed in the text are indicated by capital letters; colors reflect distribution areas. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)”

The phylogeny above shows the large number of American taxa in subgenera Calosphace and Audibertia. While many of these species have also been used as aromatic herbs and traditional medicines, the most famous of the American Salvias, chia, is known for its nutritious seeds (Jenks & Kim, 2013a). Chia is a name given to two species of Salvia: S. columbariae and S. hispanica. S. columbariae ranges from southern California to central Mexico, at which point the range of S. hispanica begins and extends to Guatemala. Indigenous groups throughout that range historically used both species of chia as a pre-Columbian staple food source. The Aztecs cultivated it, and 16^th century Spanish codices indicate it may have been as widely utilized as maize (Cahill, 2003).

Chia nutlets (S. hispanica) and a dried sage (S. officinalis) leaf for scale

Technically, the chia “seeds” you can buy in the store (or harvest yourself) are fruits. The Salvia fruit, like those of all mint family species, is called a schizocarp. The ovary inside the flower has four chambers, called locules. Each locule matures into an independent, indehiscent nutlet. The shell (pericarp) of the nutlet is stratified into the same categories of outer fruit layers as are more familiar fleshy fruits (cuticle, epicarp, mesocarp, endocarp; see our pomegranate or apple essay for more details about fruit structure), but in the Salvia nutlet the outer fruit layers are dry and compressed and inseparable from the single seed inside the fruit (Capitani, Ixtaina, Nolasco, & Tomás, 2013). Salvia nutlets mature inside of papery fused calyces (see the photo below of sage nutlets and their cup-like persistent calyces).

Sage (Salvia officinalis) leaves and nutlets inside of papery, fused persistent calyces.

The word “chia” is derived from the Aztec language Nahuatl word for “oily,” a name bestowed because chia seeds do have a high oil content (Cahill, 2003). Chia oil is rich in the omega-3 fatty acid alpha-linolenic acid, which has contributed to its recent fame as a modern health food. High alpha-linolenic acid content may be a general feature of the genus: other Salvia species, including S. officinalis, garden sage, have been shown to have high alpha-linolenic acid content in their seeds (Ben Farhat, Chaouch -Hamada, & Landoulsi, 2015).

Chia nutlets are also known for the gooey mucilage they exude when wet. This polysaccharide matrix is used as a food binder and thickener (Google “vegan egg replacement”). The production of mucilaginous diaspores (the dispersing agent, a fruit or a seed) is called myxocarpy. As Katherine discusses in her essay on okra, the flagship mucilaginous food plant, the purpose of the mucilage is likely water retention in the arid regions where these plants tend to come from. The mucilage might also act as a glue to bind the nutlet to the soil or to a dispersing animal’s fur—or to the terracotta substrate of a Chia Pet. Myxocarpy is most common in plants with small seeds growing in dry, arid areas, like those where Salvia species have radiated (Ryding, 1992).

Sage growing in coastal California, a Mediterranean-type ecosystem

Within the mint family, myxocarpy only occurs in the subfamily Nepetoideae. The subfamily, incidentally, gets its name from the catnip genus, Nepeta. Most if not all of the familiar edible herbs from the mint family are in this subfamily. Katherine has taken advantage of myxocarpy in this clade by serving soaked black basil (Ocimum basilicum) nutlets as a basil-scented vegan “caviar.”

Cat in the catnip (Nepeta cataria)

Salvia aroma and flavor–and I think the psychoactive properties of catnip for cats and known hallucinogen Salvia divinorum–comes from the terpenoids and phenolics that comprise their essential oils. The terpenoids are synthesized and stored in special glandular trichomes on the leaf surface (Schuurink & Tissier, 2019). Trichomes are hair-like extensions of the epidermis, although the glandular trichomes full of essential oil look more like water balloons than hair. Salvia species have other types of trichomes in addition to the glandular trichomes that are indeed much more hair-like and give the leaves of some Salvia a downy or prickly appearance (Kamatou et al., 2006).

Scanning electron micrograph (SEM) of a rosemary leaf. Spherical oil-filled glandular trichomes are found amongst the branched hair-like trichomes covering the lower surface of the leaf, which has a greater profusion of hairs and glands than the upper surface. When the glands are damaged or broken the aromatic essential oil is released. Magnification: x1550 (x381 at 10cm wide). Photo from https://psmicrographs.com/sems/flowers-plants/

We discussed trichome function extensively in one of our kiwi essays. The hair-like trichomes may serve the leaf by protecting it from excess solar radiation and wind and otherwise creating a more mild microclimate at the leaf surface to help it retain water.

Rosemary

Terpenoid biosynthesis requires numerous steps in which intermediate chemical products are modified by a series of specific enzymes and other proteins. Small changes in the genes responsible for those proteins can lead to big qualitative changes in the final terpenoid mix in the essential oil of a given taxon. We mammals are adept at discerning aroma differences between chemically similar terpenoids. For example, in on our carrot top essay we discussed the case of spearmint and caraway. The respective versions of the terpenoid carvone that characterize the essential oils of those plants differ only in the physical configuration of the same chemical elements, but they smell radically differently to us.

Clary sage (S. sclarea)

The function of the essential oil in the glandular trichomes, however, is not to improve human well being. Plants synthesize those lovely terpenoids as chemical defense against insect herbivores and microbial pathogens. When the hair-like trichomes fail to stop the intruders, the glandular trichomes will explode on contact, drenching the would-be attackers in a caustic-but-fragrant deluge.

rosemary

The pharmacopeia of terpenoid aromas present in the mint family—bring to mind the scents of sages, rosemary, lavender, peppermint, spearmint, savory, thyme, oregano, marjoram, shiso, basil—owes its evolutionary origins certainly in part at least to the various selection pressures imposed on those herbal taxa by their pests. Within even commonly grown domesticated Salvia species, essential oil constituent variation leads to dramatic differences in aroma. For example, consider the differences among rosemary, garden sage, clary sage (S. sclarea), and pineapple sage (Salvia elegans), which has a notably fruity smell. The fruitiness is due in part to the presence of the terpenoids charcteristic of citrus, which are widespread across plants.

Garden sage (Salvia officinalis)

The Roman historian and natural scientist Pliny the Elder coined the name Salvia, which is derived from the Latin salvare, meaning to heal and save, and salvus, meaning uninjured or whole. The common English name “sage” of these plants ultimately comes from this same Latin root. In Pliny the Elder’s time, the Mediterranean Salvia species were considered healing herbs, good for treating colds and a variety of ailments. Salvia feature prominently in the ethnomedicine of every region in which it is found (South Africa: (Kamatou et al., 2006); Central and South America: (Jenks & Kim, 2013b)). There is a Chinese proverb that asks “How can a man grow old who has sage in his garden?” I do not know which Salvia species would have been responsible for this proverb. There are over a hundred species of Salvia species native to China, and the Mediterranean import Salvia officinalis is grown throughout the country.

Bundle of dried sage, recently, recently, in Alaska

The health and wellness meaning of “sage” is etymologically independent from its other definition as a wise thing or wise person. This second meaning ultimately comes from the Latin sapere, to know or taste. I personally enjoy conflating these meanings, tying wisdom and well-being to the plant. I like that the Salvia officinalis that grew on a pot on my deck this summer and that will season comfort food this winter is a descendent from the plants that healer contemporaries of Pliny the Elder would have searched for amidst sun-drenched rocks in the Mediterranean hills.

Salvia in macarons at my local bakery (Fire Island) this week: blackberry-sage and rosemary-merlot.

Simon & Garfunkel close the Parsley, Sage, Rosemary and Thyme album with the song “7 O’Clock News/Silent Night,” in which they juxtapose jarring newscasts from the Nixon and Johnson era with the Christmas carol. This holiday season has felt a bit like that song to me, like concerted effort is required to prevent awful, omnipresent news from drowning out the joy and solemnity of marking the darkest time of the year. But perhaps honoring traditions always involves this element of deliberately carving out the space in which to do so. Perhaps sprinkling rosemary and sage into a holiday stew or stuffing can be a radical act, a defiant embrace of old wisdom to fortify ourselves to stand with each other and create something beautiful in the cold. Regardless, insane amounts of butter will be involved, at least at my house. And when the January 2^nd resolutions to “eat better” come around, chia will be there.

References

Ben Farhat, M., Chaouch -Hamada, R., & Landoulsi, A. (2015). Oil yield and fatty acid profile of seeds of three Salvia species. A comparative study. Herba Polonica, 61(2), 14–29. doi:10.1515/hepo-2015-0012

Cahill, J. P. (2003). Ethnobotany of Chia, Salvia hispanica L. (Lamiaceae). Economic Botany, 57(4), 604–618. doi:10.1663/0013-0001(2003)057[0604:EOCSHL]2.0.CO;2

Capitani, M. I., Ixtaina, V. Y., Nolasco, S. M., & Tomás, M. C. (2013). Microstructure, chemical composition and mucilage exudation of chia ( Salvia hispanica L.) nutlets from Argentina. Journal of the Science of Food and Agriculture, 93(15), 3856–3862. doi:10.1002/jsfa.6327

Drew, B. T., González-Gallegos, J. G., Xiang, C. L., Kriebel, R., Drummond, C. P., Walker, J. B., & Sytsma, K. J. (2017). Salvia united: The greatest good for the greatest number. Taxon, 66(1), 133–145. doi:10.12705/661.7

Jenks, A. A., & Kim, S. C. (2013a). Medicinal plant complexes of Salvia subgenus Calosphace: An ethnobotanical study of new world sages. Journal of Ethnopharmacology, 146(1), 214–224. doi:10.1016/j.jep.2012.12.035

Jenks, A. A., & Kim, S. C. (2013b). Medicinal plant complexes of Salvia subgenus Calosphace: An ethnobotanical study of new world sages. Journal of Ethnopharmacology, 146(1), 214–224. doi:10.1016/j.jep.2012.12.035

Kamatou, G. P., van Zyl, R. L., van Vuuren, S. F., Viljoen, A., Figueiredo, A. C., Barroso, J. G., … Tilney, P. M. (2006). Chemical composition, leaf trichome types and biological activities of the essential oils of four related Salvia Species indigenous to Southern Africa Analysis of plant volatile using 2D gas chromatography View project Chemometrics View project. Journal of Essential Oil Research. Retrieved from https://www.researchgate.net/publication/236850867

Rundel, P. W., Arroyo, M. T. K., Cowling, R. M., Keeley, J. E., Lamont, B. B., & Vargas, P. (2016). Mediterranean Biomes: Evolution of Their Vegetation, Floras, and Climate. Annual Review of Ecology, Evolution, and Systematics, 47, 383–407. doi:10.1146/annurev-ecolsys-121415-032330

Ryding, O. (1992). Pericarp structure and phylogeny within Lamiaceae subfamily Nepetoideae tribe Ocimeae. Nordic Journal of Botany, 12(3), 273–298. doi:10.1111/j.1756-1051.1992.tb01304.x

Schuurink, R., & Tissier, A. (2019). Glandular trichomes: micro-organs with model status? The New Phytologist, nph.16283. doi:10.1111/nph.16283

Vargas, P., Fernández-Mazuecos, M., & Heleno, R. (2018). Phylogenetic evidence for a Miocene origin of Mediterranean lineages: species diversity, reproductive traits and geographical isolation. Plant Biology, 20, 157–165. doi:10.1111/plb.12626

Walker, J. B., Sytsma, K. J., Treutlein, J., & Wink, M. (2004). Salvia (Lamiaceae) is not monophyletic: implications for the systematics, radiation, and ecological specializations of Salvia and tribe Mentheae. American Journal of Botany, 91(7), 1115–1125. doi:10.3732/ajb.91.7.1115

Will, M., & Claßen-Bockhoff, R. (2017). Time to split Salvia s.l. (Lamiaceae) – New insights from Old World Salvia phylogeny. Molecular Phylogenetics and Evolution, 109, 33–58. doi:10.1016/j.ympev.2016.12.041

Dreaming of white cocoa, hibiscus, and a happy Gomphothere

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Katherine’s search for delicious white chocolate (it exists) leads to a holiday twist on truffles. And whatever your festivities proclivities may be, we Botanists in the Kitchen wish you a very merry Hibiscus and a happy Gomphothere!

White chocolate
’Tis the season to sound the trumpets and pronounce judgment upon the holy or evil nature of traditional holiday foods. Try mentioning fruit cake or egg nog in mixed company and see what happens. If you are among this season’s many vociferous critics of recently trendy white chocolate, you’ve probably been complaining that white “chocolate” is not even chocolate (uncontroversial) and that it tastes like overly sweet vanilla-flavored gummy paste dominated by an odd powdered-milk flavor, and that it exists only to cover over pretzels or perfectly good dark chocolate or to glue peppermint flakes to candy. You might even jump on the white chocolate hot cocoa trend, which has become a social media flash point now that pumpkin spice season is finally over.

It’s true that white chocolate is not technically chocolate; it lacks the cocoa solids that give genuine chocolate its rich complex flavor borne of hundreds of aromatic compounds balanced by just a touch of sour and bitter. However, proper white chocolate is made from cocoa butter, the purified fat component of the Theobroma cacao seeds from which true dark chocolate is also made. Raw cocoa butter has its own subtle scent and creamy texture, and I thought I could use it to make a version of white chocolate more to my liking, with less sugar and no stale milk flavor.

It turns out that working with cocoa butter is tricky, but it gave me the chance to learn a lot more about the nature of this finicky fat. It also turns out that sugar and some kind of milk powder are essential ingredients in all the homemade white chocolate recipes I found, because they seem to make the fat easier to work with. My plan was to make white truffles, which would showcase homemade white chocolate as an ingredient but allow me to balance its unavoidable sweetness with another flavor.

Because it can be fun and instructive to find a culinary match within the same botanical family, I searched for a balancing flavor from the list of common edible members of the Malvaceae. Baobab? Too hard to find locally. Durian? Too risky. Linden tea? Too subtle. Okra? No. Just no. Hibiscus? Bright red and tangy and perfect. Although hibiscus and Theobroma are rarely united in cooking – and they took divergent evolutionary paths about 90 million years ago – I found that these plants work extremely well together. Unlike traditional dark rich chocolate truffles, white cocoa truffles rolled in crimson hibiscus powder melt in your mouth like cool and fluffy snowballs, followed by a refreshing sour kick. Instead of being just one more rich December indulgence, these play up the bright white clear and cold elements of the season. Even better, the most widely available culinary hibiscus flowers come from the African species Hibiscus sabdariffa, sometimes called roselle, which has its own connection to the winter holidays: it stars as the main ingredient in a spicy punch served at Christmastime in the Caribbean.

Cocoa butter
Melting and molding dark chocolate into candies is notoriously difficult because the chocolate can lose its temper and become grainy or develop white oily streaks as it cools. The trouble lies in the cocoa butter, and like many chocolate dilettantes, I became interested in cocoa butter behavior when I tried to learn how to keep my dark chocolate in temper.

Cocoa butter is the fat that Theobroma cacao stores in its seeds to fuel the growth of its seedlings. Like many of the large edible seeds we casually call nuts, cacao seeds are about half fat by weight, but their fat composition is very different from the fat found in almonds, walnuts, or even the ecologically similar Brazil nuts (Chunhieng et al., 2008). In plants and animals, all naturally occurring fat is composed almost entirely of triglycerides, which are based on a glycerol backbone with three fatty acid tails. Those fatty acids can be long or short, and straight (saturated) or kinked (unsaturated). The nature of the tails determines how the individual triglyceride molecules interact to form crystals and whether the fat will be liquid or soft or firm at room temperature (Thomas et al., 2000). Very generally, the more straight tails there are, the more closely and stably the triglyceride molecules can be packed together, and the firmer the fat will be. (Manning and Dimick have a clear description of this in the case of cocoa butter, and their paper is available open source).

Whereas milk fat includes about 400 different kinds of fatty acids (Metin & Hartel, 2012), cocoa butter is dominated by only three (Griffiths & Harwood, 1991). That simple chemical profile isn’t unusual for seeds, but the types and proportions are. Cocoa butter triglycerides mostly contain two long, straight fatty acids (palmitic and stearic) and one long kinked one (oleic), in fairly equal proportions (Griffiths & Harwood, 1991). The high percentage of stearic acid is especially unusual and contributes to the solid state of cocoa butter at room temperature, while the equal combination of these three particular fatty acids causes cocoa butter to melt quickly on our skin or in our mouth.

Another unusual property of cocoa butter is that it actually cools your mouth when it melts. A piece of chocolate on your tongue gradually warms, and at first you feel it approaching your body temperature. However, precisely at its melting point – just below body temperature – it abruptly stops getting warmer, even as it continues to remove heat from your mouth, thereby cooling it. This pause in warming is due to the high latent heat of fusion of the triglyceride molecules. Because it happens just below body temperature, you feel a cooling sensation.

Interestingly, the exact proportions of the three fatty acids varies slightly with genotype and environmental conditions during the growing season (Mustiga et al., 2019). Cocoa butter is, ultimately, food for cacao tree seedlings, and so the precise fatty acid composition of the seeds certainly reflects the species’ seed ecology. To my knowledge, the details have not yet been investigated, but I assume that the fat properties influence both seed longevity under hot tropical temperatures and the ability of seedlings to metabolize the fats as they draw on them for energy during germination. In any case, because the exact proportions of the three fatty acids determines the melting point of cocoa butter, its source and genotype will also affect its behavior in our kitchens or in a factory.

A miniature sleigh and one giant Gomphothere
Speaking of ecology, all that lovely fat and protein and carbohydrate in a cacao seed is great for humans and our chocolate habits, but it doesn’t help T. cacao as a species if at least some of their seeds don’t eventually become trees. Actually, our chocolate habits over the last few millennia have done a lot to spread cacao seeds (Zarrillo et al., 2018), but for the millions of years that cacao existed before humans spread into neotropical cacao territory, other animals must have carried away the cocoa pods.

Given the hefty size of a cacao fruit (about a pound, or 500 grams), its relatively large seeds, and its yellow-orange color, the species appears adapted for dispersal by a correspondingly large animal. But no such animal candidates coexist now with Theobroma cacao or with several other similar neotropical tree species. One long-standing hypothesis has been that tropical fruits with this suite of traits are anachronisms that coevolved with now-extinct megafauna, such as gomphotheres – relatives of American mastodons – or giant ground sloths (Guimarães et al., 2008). At least one genus of gomphothere did co-occur with cacao (Lucas et al. 2013), so it is possible that they spread the seeds, but we need more complete information about their diets to be sure.

We wish you a red hibiscus and a happy gomphothere

Merry Hibiscus

The genus I chose to balance white cocoa’s sweetness and add a bit of festive color was Hibiscus, which includes hundreds of species, but Hibiscus sabdariffa is the one used most often in herbal infusions or as natural coloring or flavor. Because of its global popularity its flowers can sometimes be bought dried and in bulk at co-ops or international markets. The petals are relatively short and so a whorl of fleshy sepals makes up most of the flower, as is obvious after they have been plumped back up by a soak in hot water.

To make the hibiscus powder truffle coating, it is necessary to grind dried flowers to the finest possible powder and sieve out any remaining gritty pieces. I pulverized about half a dozen flowers in a retired coffee grinder, but you can use a mini food processor or a spice grinder. I quickly learned to let the powder settle before opening the grinder, to avoid getting a Gomphothere-sized dose of astringent dust in my human-sized nose.

After grinding, the powder must be sifted through the finest sieve you can manage. I use a gold filter like those designed to filter coffee. It takes time and patience but this step is important for the look and the mouthfeel of the truffles. The sieve full of leftover grit makes a nice cup of tangy tea.

Dried (bottom) and reconstituted calyces (ring of sepals) of Hibiscus sabdariffa, sometimes called roselle

Truffles
Traditional dark chocolate truffles are pretty simple to make: Simmer some cream and let it cool to the point where you might consider taking a very hot bath in it. Herbs or spices may be steeped in the cream during the simmer. Measure the volume of the hot cream in ounces and add twice as many ounces by weight of finely chopped chocolate. Stir gently to melt all the pieces and then allow the mixture (called ganache) to cool at room temperature. Overheating the chocolate initially or cooling the ganache too fast takes the chocolate out of temper. When the ganache is firm, roll it into lumpy balls, coat with cocoa powder, lick your fingers, et voilà.

It turns out that dark chocolate is much more forgiving than pure cocoa butter when it comes to truffles. The first time I tried to make white cocoa truffles, I followed my usual recipe, using chopped cocoa butter in place of dark chocolate and adding some sugar with the cream. Although I was extremely careful not to overheat the cocoa butter, my ganache separated anyway. Whereas dark chocolate contains cocoa solids that support the desired type of crystal formation in solidifying chocolate (Svanberg et al., 2011), cocoa butter does not. In my various experiments with the gentle melting of cocoa butter, I went so far as to sit for an hour on a plastic bag full of grated cocoa butter. Although it should have melted at body temperature, it never got quite soft enough. I finally got the texture right when I accepted a century of professional wisdom and introduced the dreaded milk powder as well as a lot of sugar into the recipe.

Malvaceae: cocoa truffles rolled in hibiscus powder

Cocoa truffles in hibiscus powder

Below is my current working recipe, subject to additional experimentation:

3 oz food grade pure cocoa butter, chopped
1/2 cup powdered sugar
1 1/2 teaspoons powdered milk
1/4 cup cream
1/4 cup sugar
hibiscus powder from 5 or 6 dried hibiscus flowers

In a small food processor, pulverize the cocoa butter, powdered sugar, and powdered milk. The result should be coarse dry crumbs. Place the crumbs in a small heatproof bowl or the top of a double boiler.

Bring the cream to a simmer and dissolve the sugar in it. (For one version I steeped a couple of hibiscus flowers in the cream, which tasted good but made the truffles pink all the way through. Extra cream was needed to account for some of it clinging to the flowers.)

When the cream is the temperature of a hot bath, pour it into the cocoa butter mixture. Remember, cocoa butter melts below body temperature so the cream doesn’t have to be very hot. The crumbs will cool the cream as you stir, and you want the mixture to be just above body temperature as the centers of the crumbs are melting. Those last bits to melt will seed the mixture with the desired type of crystals and favor their formation as the mixture cools.

It will take several hours for the mixture to be firm enough to roll into balls. I usually leave it at room temperature overnight. Do not rush the process by chilling it! Fast cooling favors unstable crystals and your truffles will be grainy.

Roll the mixture into balls and roll them in the hibiscus powder.

Note that you can buy white “chocolate” chips and use them in place of dark chocolate in the usual truffle recipe described above. I tried this and it worked when I increased the chips-to-cream ratio to slightly above 2-to-1. However, do read the ingredient list because many white chocolate chips (especially those labeled “white morsels”) contain no cocoa butter at all. The Gomphotheres would not approve.

White cocoa truffles with hibiscus dust and whole dried hibiscus flowers

References and further reading

Chunhieng, T., Hafidi, A., Pioch, D., Brochier, J., & Didier, M. (2008). Detailed study of Brazil nut (Bertholletia excelsa) oil micro-compounds: phospholipids, tocopherols and sterols. Journal of the Brazilian Chemical Society, 19(7), 1374-1380.

Gouveia, J. R., de Lira Lixandrão, K. C., Tavares, L. B., Fernando, L., Henrique, P., Garcia, G. E. S., & dos Santos, D. J. (2019). Thermal Transitions of Cocoa Butter: A Novel Characterization Method by Temperature Modulation. Foods, 8(10), 449.

Griffiths, G., & Harwood, J. L. (1991). The regulation of triacylglycerol biosynthesis in cocoa (Theobroma cacao) L. Planta, 184(2), 279-284.

Guimarães Jr, P. R., Galetti, M., & Jordano, P. (2008). Seed dispersal anachronisms: rethinking the fruits extinct megafauna ate. PloS one, 3(3), e1745.

Hernandez-Gutierrez, R., & Magallon, S. (2019). The timing of Malvales evolution: Incorporating its extensive fossil record to inform about lineage diversification. Molecular phylogenetics and evolution, 140, 106606. https://doi.org/10.1016/j.ympev.2019.106606

Lucas, S. G., Yuan, W., & Min, L. (2013). The palaeobiogeography of South American gomphotheres. Journal of Palaeogeography, 2(1), 19-40.

Manning, D. M. & Dimick, P. S. (1985) “Crystal Morphology of Cocoa Butter,” Food Structure: Vol. 4 : No. 2 , Article 9. Available at: https://digitalcommons.usu.edu/foodmicrostructure/vol4/iss2/9

McGee, H. (2007). On food and cooking: the science and lore of the kitchen. Simon and Schuster.

Metin, S., & Hartel, R. W. (2012). Milk fat and cocoa butter. In Cocoa butter and related compounds (pp. 365-392). AOCS Press.

Mustiga, G. M., Morrissey, J., Stack, J. C., DuVal, A., Royaert, S., Jansen, J., … & Seguine, E. (2019). Identification of climate and genetic factors that control fat content and fatty acid composition of Theobroma cacao L. beans. Frontiers in plant science, 10, 1159.

Svanberg, L., Ahrné, L., Lorén, N., & Windhab, E. (2011). Effect of sugar, cocoa particles and lecithin on cocoa butter crystallisation in seeded and non-seeded chocolate model systems. Journal of Food Engineering, 104(1), 70-80.

Thomas, A., Matthäus, B., & Fiebig, H. J. (2000). Fats and fatty oils. Ullmann’s Encyclopedia of Industrial Chemistry, 1-84.

Zarrillo, S., Gaikwad, N., Lanaud, C. et al. (2018) The use and domestication of Theobroma cacao during the mid-Holocene in the upper Amazon. Nat Ecol Evol 2, 1879–1888 doi:10.1038/s41559-018-0697-x

The Beet Goes On

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In this Valentine’s Day edition, Katherine brings you a love song with a beet. Sweet and red, sort of heart-shaped, bearing rings, and definitely divisive – beets should be the unofficial vegetable of the holiday. And if you don’t feel like celebrating, then you can just sit alone and eat dirt.

Throughout two years of dating and our first six months of marriage, my husband and I had never discussed our feelings about beets. Then again, I had never made beets for him before. When I did, they were a cheap but healthy way to bulk up a vat of stew that would feed us every night for a week. In my husband’s version of the story, it lasted for three weeks. “I hope you like beets,” I announced that evening. “I may have added too many.”

Whether you love or hate beets, it is probably because they taste like dirt. Some people (my husband) can’t get over the flavor, and others can’t get enough of it. Some people experience beeturia, the appearance of bright red or hot pink urine after they eat red beets. Maybe this sight unsettles you. Or maybe you embrace the opportunity to track the transit of beet pigments through your body. You may admire their lovely rings and be inspired by the rich and brilliant colors that beets bring to salads. Or you might have picked up a lifelong aversion after too many canned pickled beets on a school lunch tray. Beets are a pretty polarizing vegetable. If you are among the haters, I’m going to do my best to turn the beet around for you.

Red and white beets

Why beets taste like dirt

Beets taste like dirt because they contain a compound called geosmin (meaning “dirt smell”). Geosmin is produced in abundance by several organisms that live in the soil, including fungi and some bacterial species in the genus Streptomyces. Humans are extremely sensitive to low concentrations of geosmin – so much so that we can smell it floating in the air after rain has stirred it up from the soil (Maher & Goldman, 2017). While people generally like that rain-fresh scent in the air, it’s less welcome elsewhere. For example, we perceive it as an off taste in water drawn from reservoirs with a lot of geosmin-producing cyanobacteria. In wines, geosmin contributes to cork taint. Continue reading →

Pirates of the Carob Bean

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Maybe the name takes you back to gentler days of Moosewood Cookbook and the dusty spicy local co-op. Or maybe you were a kid back then and fell for a chocolate bait-and-switch. Whether you are sweetly nostalgic or wary and resentful, it’s worth giving carob another chance. Katherine argues that it’s time to pull this earthy crunchy 70’s food into the superfood age. She offers foraging tips and recipes to help you get to know carob on its own terms.

From November through January, the carob trees in my neighborhood dangle hard, lumpy, dark brown fruits resembling lacquered cat turds. They are delicious and nutritious and of course I collect them. I am, without apology, a pod plundering, legume looting, pirate of the carob bean. If you seek adventure and happen to live in California, Arizona, or on the Mediterranean coast, you can probably pilfer some carob fruits yourself and play with them in your kitchen. If you lack local trees or the pirate spirit, you can order carob powder and even whole carob beans with one simple click.

Although plundering season begins just as the year is ending, I always wait until January to gather carob fruits for two reasons. First, carob functions mainly as a healthful chocolate substitute, and during the holiday season, fake chocolate just seems sad. In January, however, eating locally foraged carob feels virtuous and resourceful. Second, November and December are when my local carobs make the flowers that will produce the next year’s crop, and those flowers smell like a pirate’s nether parts after a shore leave. Or so I imagine, and not without precedent. A man who should have been inured to such salty smells, Pliny the Elder, natural historian and commander in the Roman Imperial Navy, described the flowers as having “a very powerful odor.” It’s not clear why these flowers have a sort of seaman scent, since the main volatiles wafting from the flowers – linalools and farnesene – smell like lilies and gardenias (Custódio et al., 2006). In any case, I keep my distance until the flowers have finished mating season.

Carob trees

Despite their stinky flowers, carobs make great street trees and produce a valuable crop in many Mediterranean-type climates. They are beautiful, tolerant of dry and poor soils, pest resistant, and tidy. Carobs are legumes – like familiar peas and beans – but they belong to a different branch of the legume family (Caesalpinioideae), one that contains mostly trees and woody shrubs with tough inedible fruit (Legume Phylogeny Working Group, 2017). Carob pods look about as edible as Jack Sparrow’s boots, and the species’ scientific name, Ceratonia siliqua, means “horny long pod,” which well captures the intimidating nature of their leathery fruit. But as you will see below, the fruits are easy to harvest and process, and their sweet pulp is worth seeking out. Continue reading →

#Celery

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It’s hard to get too excited about eating celery, but if you can manage to see a dip-drenched celery stick as a dynamically loaded cantilevered beam, then its stringy bits suddenly start to look like incredible feats of bioengineering. The mildest mannered member of the crudité platter turns out to be a misunderstood superhero.

If you are about to celebrate Thanksgiving, chances are good that you have a lot of celery in your immediate future. It shows up in dressing and cranberry relish and especially in leftovers, like turkey salad sandwiches. When I was growing up, my sister and I were tasked with picking the carcass for turkey hash, which, in our family, was basically turkey soup stretched with lots of celery and potatoes and never enough salt. Although frugal and nutritious, this one-pot crusade against food waste did not inspire a lifelong love of cooked celery. But you don’t have to like celery the food to admire its alter ego, celery the plant.

Leaves, not stems

Celery the food may not excite you, but celery the plant – the bundle of dynamically loaded cantilevered beams – is a biomechanical superhero worth exploring in the kitchen. Celery (Apium graveolens) is one of the clearest examples of how a plant’s life in the wild over tens of millions of years yielded anatomical adaptations that determine how we use it now. Because of its evolutionary responses to biomechanical challenges, it is now perfectly built to hold peanut butter or scoop dip, and when sliced, its crescent moon shapes are pretty in soup and chopped salads. On the other hand, its tough strings catch between teeth and are not easy to digest.

Celery stalks are the petioles (“stalks”) of compound leaves. They are not stems, in spite of widespread misrepresentation in elementary school lesson plans. They may look like stems to some people because they are thick and fleshy and have prominent veins running lengthwise through them. But there are several morphological clues to their leafy identity, including these: Continue reading →

Carrot top pesto through the looking glass

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Isomers are molecules that have the same chemical constituents in different physical arrangements. Some terpenoid isomers have very different aromas and are important food seasonings. A batch of carrot top pesto led to an exploration of intriguing terpenoid isomers in the mint, carrot, and lemon families.

“Oh, c’mon. Try it,” my husband admonished me with a smile. “If anyone would be excited about doing something with them, I should think it would be you.”

The “them” in question were carrot tops, the prolific pile of lacy greens still attached to the carrots we bought at the farmer’s market. I have known for years that carrot tops are edible and have occasionally investigated recipes for them, but that was the extent of my efforts to turn them into food. My excuse is that I harbored niggling doubts that carrot tops would taste good. Edible does not, after all, imply delicious. My husband had thrown down the gauntlet, though, by challenging my integrity as a vegetable enthusiast. I took a long look at the beautiful foliage on the counter.

“Fine,” I responded, sounding, I am sure, resigned. “I’ll make a pesto with them.”

Carrot tops, it turns out, make a superb pesto. I have the passion of a convert about it, and not just because my carrot tops will forevermore meet a fate suitable to their bountiful vitality. The pesto I made combined botanical ingredients from two plant families whose flavors highlight the fascinating chemistry of structural and stereo isomers. Continue reading →

Preserving diversity with some peach-mint jam

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We are knee deep in peach season, and now is the time to gather the most diverse array of peaches you can find and unite them in jam. Katherine reports on some new discoveries about the genetics behind peach diversity and argues for minting up your peach jam.

Jam inspiration

Fresh peaches at their peak are fuzzy little miracles, glorious just as they are. But their buttery mouthfeel and dripping juice are lost when peaches are processed into jam and spread across rough toast. To compensate for textural changes, cooked peaches need a bit more adornment to heighten their flavor, even if it’s only a sprinkling of sugar. Normally I am not tempted to meddle with perfection by adding ginger or lavender or other flavors to peach jam. This year, however, as I plotted my jam strategy, the unusual juxtaposition of peach and mint found its way into my imagination over and over again, like the insistent echo of radio news playing in the background. Peach and mint, peach and mint, peach and mint – almost becoming a single word. To quiet the voice in my head I had to make some peach-mint jam. The odd combination turned out to be wonderful, and I’m now ready to submit the recipe to a candid world. As we will see below, it’s not without precedent. Mmmmmmpeachmint jam. Continue reading →

The Botanist in the Kitchen

where botany meets the cutting board

Category Archives: Flavor

Botany lab of the month – August edition: Rocky Top Corn Soup

The adoration of the pine nut

Lessons from pine sex

What is a pine nut?

Conifer week in your kitchen

Pine nuts at Christmas

Investing in pine nuts

The message of the pine nut

References and further reading

The leftovers of 2020

Sage, rosemary, and chia: three gifts from the wisest genus (Salvia)

Dreaming of white cocoa, hibiscus, and a happy Gomphothere

The Beet Goes On

Pirates of the Carob Bean

#Celery

Carrot top pesto through the looking glass

Preserving diversity with some peach-mint jam

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Lessons from pine sex

What is a pine nut?

Conifer week in your kitchen

Pine nuts at Christmas

Investing in pine nuts

The message of the pine nut

References and further reading

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