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

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 16th 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 2nd 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

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.

Malvaceae: Gomphothere.001

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.

img_0699.jpg

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.

Malvaceae: hibiscus cocoa truffles

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

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 meant to bulk up a brimming 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

The Chestnut Song

“The Christmas Song” tops the charts every December, but there’s lots more to know about those chestnuts roasting on an open fire. We peel back the layers in this essay, which is one of our two contributions to this year’s Advent Botany holiday collection.

I first tried chestnuts when I was a student in Paris. The holiday season was peaceful that year, as it should be, and I’ve cherished my memories of it all the more as intense protests are spreading through France, and violence has shattered a Christmas market in Strasbourg. In that long-ago December, though, my most consuming emotion was a kind of double nostalgia. I missed home, and yet I wasn’t quite ready to leave that beautiful city behind. As I walked for hours and hours gathering last looks, it was thrilling to get caught up in the sudden early darkness of winter and the elaborate holiday windows of the grand old department stores. During one evening promenade, I saw a street merchant who had anchored himself in the middle of the streaming agitated crowd and was patiently tending a pan of marrons grillés, freshly roasted chestnuts. The scene was so sepia toned, so achingly 19th century, that I had to have some, just to glut my sentimentality. I bought a newspaper cone of the hot aromatic nuts and managed to peel one with my cold fingers right there on the sidewalk. Continue reading

The Ballad of Farro Salad

We botanists in the kitchen are busy preparing for Thanksgiving, as you probably are too. Please enjoy this quick song about a grain salad. And if you still need ideas for vegetarian side, consider this a recipe.

To the tune of Darcy Farrow.  (See this version by John Denver if you don’t know the tune.)

The Ballad of Farro Salad

Where the water runs down to the Nile River plain,
There came a kernel, emmer farro was its name.
A wheat of four-fold ploidy, and a fair one to see,
The sweetest texture e’er found in a grain.

It goes well with tomatoes, cherries red and gold.
The larger ones we halve; the littlest we leave whole.
Add goat cheese crumbled in, with parsley julienned.
Serve at room temp or maybe even cold.

Oh they sing of emmer farro where the Hudson runs through.
They sing of its beauty out in San Francisco too.
At dusky sundown, to its name they drink a round,
and to its golden hearty chew.

Botany lab/rant of the month: that’s a magic beanstalk, not a soybean

In chaotic times, there are moments when you just have to take comfort in order anywhere you can find it. Katherine reviews some basic plant growth rules and takes a major company to task for undermining botanical literacy.

Would you buy milk from a dairy whose smiling cow mascot had an udder perched on top of her head? Would it bother you to see waiving teats where her ears should be? What if the unsettling image were wrapped in a lyrical ode to ungulates and to the steadfast farmers who rise before dawn to tap into “all that mammalian goodness”? Would a Holstein hagiography be enough to distract you, or would the contrast between carefully crafted ad copy and a negligent disregard for bovine biology trip your bullshit meter?

I think about this every time I buy soy milk made by one particular giant of the non-dairy milk industry. Normally I make my own soy milk – it’s cheap and fast and delicious – but sometimes life intervenes and I have to go with convenience. At my favorite local grocer, that means buying this brand. You might think it’s the gellan gum and the “natural flavors” that offend me, but really I just can’t get over the carton.

Have you ever really thought about the magic of plants?” the carton beckons. Well, yes! Yes I have! Like me, these producers have “been rooted in plant power for over 20 years.” Wow, we have so much in common! I am invited to enjoy “all that leafy goodness” and call them “plant-based, plant biased or just plain plant-prejudiced.” No plant blindness here, right? 

Except for this, the botanical version of a cow with an udder on her head and a tail growing out of her chin:

Someone's wildly inaccuarate idea of a soybean plant. the brand name has been obscured to protect its reputation.

Someone’s wildly inaccurate idea of a soybean plant. The brand name has been obscured to protect its reputation. Click to enlarge.

Judging by the edamame pod randomly stuck onto a stem, this altered photo is supposed to represent a soy bean plant (Glycine max). The words below (“Discover the power of plants at [redacted].com”) almost promise botanical accuracy. Yet, for comparison, here is an actual soybean plant, with its trifoliate leaves and bushy growth habit:

Soybeans in Warren County, Indiana

A soybean plant growing in Indiana.

Not only is the image on the soy milk carton clearly not a soybean plant, but the chimeric little sprout violates basic patterns of plant construction. When I showed the carton to my class this spring, the students were all over it with fervor and a sharpie.

Why it matters

There are many extremely important and urgent challenges facing humans and other organisms all over the planet right now, including some negative social and ecological impacts of soy and the potential for new tariffs on U.S. soybeans to make these worse. So why direct righteous ire against the photo on a carton of soy milk? First of all, what biology teacher (or parent or anyone) wants to see inaccurate or misleading images, especially if they appear every single morning on breakfast tables across the country? Second, at the risk of overstating my case, I believe that someone made deliberate choices about both the text and the image on this carton in order to evoke health and sustainability, but that these choices actually expose indifference toward the plants, the farmers, and the natural world. Similar indifference has gotten our species into a lot of trouble. We all get things wrong, but it’s important to try not to.

How a plant body is supposed to look

The green world is full of gigantic trees and tiny floating plants and delicate vines and cacti and orchids and palms and titan arums. Even if we leave aside mosses and ferns to focus on seed plants, it’s obvious that natural selection has taken a very simple basic developmental program and pushed it in almost every conceivable morphological direction. A common set of plant growth rules accommodates the varied forms of a quarter million or more species – which is astonishing – and yet the graphic designer for this soy beverage company somehow managed to stitch together an oddly improbable plant.

Under the basic developmental program, the set of stem cells (the meristem) at the apex of a growing shoot spins off a series of appendages (e.g. leaves) at regular intervals, arranged along the stem in a regular pattern. Most often, appendages spiral around the stem or occur in opposite pairs. The resulting basic vegetative unit is a leaf (or leaf homolog such as a bract, scale, or spine), the span of stem below it (the internode), and a bud at the place where the leaf meets the stem (the axil). A shoot grows by adding these units in sequence. New leaves continue to expand and internodes continue to elongate for a little while, so leaves near the tip of a shoot tend to be smaller and closer together than they eventually will be. Buds in the axils of the appendages may themselves grow out as branches that reiterate the basic body plan. The result is a modular and potentially nested structure composed of repeated subunits.

Basic flowering plant body plan

Flowering plants (and other seed plants) are built from a series of basic vegetative units, consisting of a leaf and an associated axillary bud and the internode below it. Axillary buds may develop into branches that are similarly built of a series of vegetative units. When plants begin to flower, bracts often develop in place of leaves, and flowers emerge from buds in their axils. Note that this generic plant is not meant to represent any particular species.

When a plant starts to flower, this regular organization does not go away, even if it is modified somewhat. For example, flower clusters (inflorescences) are generally produced at branch tips and along shoot axes where leafy branches would have emerged. And while leafy branches are associated with (subtended by) leaves, inflorescences are subtended by leaf-like appendages called bracts. Inflorescences themselves might transition to a complex branching architecture that differs from the rest of the vegetative plant body, but they still produce flowers in a regular pattern. Because individual flowers are conceptually (and evolutionarily) a bit like branches, they also are usually associated with bracts (Rudall & Bateman, 2010). A notable exception is plants in the mustard family (Brassicaceae); one of the genes that tells a meristem to switch gears and make a flower also suppresses formation of a subtending bract (see summary in Krizek, 2009).

Practically, what this means is that any branch, flower, or inflorescence should be associated with a subtending leaf (or bract, scale, or spine) and that any leaf (or bract, scale, or spine) potentially has a bud, branch, inflorescence, or flower associated with it. The regularity and simplicity of this fundamental pattern of seed plant development gives you a powerful framework for interpreting plants. You no longer have to ask what kohlrabi is; the leaf arrangement gives it away. You can use a combination of clues to distinguish a single compound leaf from a branch. It’s fun.

True, the pattern is not always obvious. Leaves and bracts fall off (although they often leave evident scars), and axillary buds can be extremely small or obscured. Leaves can also be reduced to tiny scales, such as those on a potato tuber. Flowers and fruits of the chocolate tree (Theobroma cacao) appear to emerge directly from an old branch, but in fact they are associated with long-gone leaf axils. And woody plants can produce new shoots adventitiously at their bases or when they are damaged. But we were talking about soybeans, not redwoods.

A magic beanstalk

Returning to the image that set off this screed, I might be able to see it as a harmless, fanciful botanical embellishment if it weren’t for the soybean pod deliberately pasted onto the stem. Surely these plant-prejudiced people could have paused their musings on the magic of plants and simply observed an actual soybean plant. They might have noticed that soybeans have compound leaves with three leaflets and that they grow more like bushes than vines. With a good photo, the artist could have gotten this image right without knowing anything at all about how plants develop. However, the text strongly implies that the central values of the company are rooted in a genuine understanding of plant biology, so I think it’s fair to hold them to a higher standard.

Now that I’ve said my piece, it’s time to take a virtual sharpie to that carton and make it botanically correct. Here’s my version.

Making soy milk at home

Homemade soy milk has many advantages. The beans for a half gallon of soy milk cost about a quarter of what you would pay for a carton at a store. Making your own is also more sustainable: bulk dried beans are less resource-intensive to ship than packaged liquid, you can often choose the source of your beans and how they are grown (e.g. organic from the U.S.), and you can control waste from the process. For example, I mix the solids strained from the liquid milk with salt, nutritional yeast, and whatever spices are handy and pack them for lunch. To the milk, I can add vanilla or not as I like. I can throw some oats or nuts or soy lecithin into the boil if I like.

  • 1 cup dried soybeans
  • water for soaking
  • 8 cups of water
  • dash of salt
  • 1/4 cup of rolled or steel-cut oats or almonds or cashews
  • immersion blender
  • fine strainer or cloth strainer bag

Soak soybeans in a medium saucepan (1.5 qt) for at least 6 hours. If you are using steel-cut oats, almonds, or cashews, soak them too.

Bring 8 cups of water to the boil in a large stock pot. The larger the better to reduce the chance that the mixture will boil over.

Drain and rinse the soybeans and return them to the sauce pan. If you are using rolled oats, add them here.

Pour some of the boiling water over the beans to cover them by about an inch, and immediately puree them with the immersion blender. Using boiling water denatures some enzymes that can cause off flavors, and an immersion blender is much safer than a regular blender for hot liquids.

Pour the blended beans into the large stock pot with the rest of the boiling water. Turn the heat to the lowest setting possible. After about 5 or 10 mins, put a lid on the pot and let it cook for another 45 mins. Add a dash of salt about midway through.

Do not leave the pot alone until it has been simmering without trouble for a while. The mixture has a tendency to boil over and make a huge mess within the first 5-10 mins.

Allow the mixture to cool for an hour or so and strain it. Refrigerate the milk right away.

The remaining solids can be flavored and eaten as they are, stirred into breakfast oatmeal or grits, baked into muffins, etc.

References

Krizek, B. A. (2009). Arabidopsis: flower development and patterning. eLS, 1-11.

Rudall, P. J., & Bateman, R. M. (2010). Defining the limits of flowers: the challenge of distinguishing between the evolutionary products of simple versus compound strobili. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 365(1539), 397-409.

Spruce tips

It’s nearing the end of the spring spruce tip season here in southcentral Alaska.

chopped spruce tips

Continue reading

Kiwifruit 2: Why are they green?

Why are some kiwifruits green when they are ripe? Or avocados or honeydew melons? The answer involves genetic accidents, photosynthesis, hidden pigments, and the words “monkey peach.”

In our kiwifruit fuzziness essay we described how the type and density of trichomes—the hairlike projections from the fruit’s skin that create the fuzziness—in the Actinidia chinensis species complex is correlated with the habitat in China to which a particular population is adapted and the ploidy level of its genome. Only polyploid (having multiple genome copies) Actinidia chinensis occupy the harshest environments—the high, arid reaches of western China—and have the highest trichome density and the longest trichomes. And those fuzzy, resilient, polyploid kiwifruits are all green on the inside (1). They are the plant kingdom’s version of an unshaved vegan after backcountry skiing for a week. The hardy plant had no trouble growing outside its plateau of origin and became the most common commercial kiwifruit in the world (A. chinensis var. deliciosa), followed closely by yellow-fleshed (“golden”), less fuzzy variants of the same species (A. chinensis var. chinensis).

An expanded view of the dozens of Actinidia species reveals orange, red, and purplish pigments that color fruits in the genus. While beautiful, this warm palette strikes me as noteworthy only in contrast to the bright green displayed by the fuzzy A. chinensis var. deliciosa that initially grabbed my attention, and, later, in green kiwiberries (A. arguta). A non-green (for lack of better terminology, “colorful”) ripe fruit, after all, is a common end point for species with fleshy fruit.

Fig. 1 from Crowhurst et al. (2008) of some fruit diversity in the kiwifruit genus Actinidia. We describe the botany and anatomy of kiwifruits in our kiwifruit fuzziness essay.

It is not difficult, however, to bring to mind other examples of species with green-ripe fruit: avocado, green grapes, some citrus, honeydew melon (I’m specifically thinking here of the pericarp or mesocarp tissue under the skin and exclude from this discussion immature fruits that lose their greenness when fully ripe, like green beans and olives). Green ripe fruit, then, in Actinidia and other taxa, seems to me to be something to explain. What, if any, function might it serve, and what are the mechanisms responsible?

While the literature on the subject is far from exhaustive, there is a fairly pedestrian explanation at least for the mechanism, if not any adaptive function, of unusually green fruit flesh outside of Actinidia: fruits start green, and straightforward mutations in a few key genes cause them to remain so. Like that intrepid, hirsute montane vegan, though, Actinidia performs the task a little differently, and it is a bit of a mystery. To understand why that is, we need some backstory on pigments in fruit and how and why they change as fruit ripens, with a focus on Actinidia. Continue reading

Kiwifruit 1: Why are they so fuzzy?

Kiwifruit is not covered in hairs. It’s covered in trichomes. And only if you’re talking about green Actinidia chinensis var. deliciosa. But, why? One answer is: pretty much to keep it from drying out. Another is: because it’s a polyploid from western China and was kind of chosen at random to be the most commonly grown kiwifruit, and they’re not all fuzzy. Those aren’t mutually exclusive answers. Put on your ecophysiology hats and grab a paring knife.

Think of fruit growth as a balancing act between ingoing and outgoing fluxes. When the balance is positive, fruits grow. When it is negative, they shrink—or shrivel. The main fluxes in question are carbon and water, which enter the fruit from the xylem and phloem of the plant vascular system. Water is lost mainly to the atmosphere via transpiration (evaporative water lost through stomata and other pores and from the skin surface). Keeping the ledger positive isn’t an easy job for a fruit. Hot, dry, and windy weather encourages transpiration and thereby increases the odds that a fruit will experience water stress. Excessive sunlight may cause sunburn. Fruits also need to avoid attack from pathogens and herbivores before the seeds within mature. A fruit’s skin—its cuticle and epidermis—is its first line of defense against abiotic and biotic threats. Some fruits resort to creative coverings to get the job done.

Here I’ll take a close look at the skin of kiwifruits. Why, exactly, are they so fuzzy?

A heart-shaped green kiwifruit (Actinidia chinensis var. deliciosa), covered in fuzzy trichomes

Continue reading

Pirates of the Carob Bean

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. CarobPiratesIf 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