Pre-Test Botanical Research – Palo Santo
I was recently asked by Leslie what flavors we would get if we distilled with palo santo. Having never used palo santo or knowingly consumed a spirit in which it was used, I could not say from experience or point to reliable example. The next best option was to conduct some research into its composition and come up with an educated prediction of its qualities. Below is a summary of the results. Using palo santo in spirits production is expected to be feasible, so the next step is to do some test distillations in our lab, which will be documented in a follow-up post.
Palo santo (Bursera graveolens) is part of the Burseraceae family so a relative of frankincense and myrrh. Having used both of these in distillation, I would expect palo santo to share some of their sweet, resinous, pungency and woodiness. Based on the two papers uploaded below, its aroma compounds are overwhelmingly terpenes (class of organic molecules primarily responsible for floral, pine and citrus notes). The most prevalent by mass is the D-isomer of limonene (key aroma compound in oil of lemon and orange zest. By contrast, the piney L-isomer is common in juniper), followed by alpha-terpineol (piney, resinous, floral, woody). It also contains menthofuran (musty, pungent, nutty) and pulegone (minty, camphoreous), which are both toxic at elevated levels, but not at the levels we would expect from use as a botanical in gin. Other notable compounds are Germacrene D (woody spice) and carvone (fennel, mint, caraway).
All of these compounds are naturally present in the palo santo and are available for extraction from the wood. This is in contrast to many of the aroma compounds you smell when burning the sticks, because many of these are products of pyrolysis reactions, which would not occur in the still. Burning the wood before use would likely not produce the same effect as most of the aroma compounds would be lost in the burning process. However, there are ways that we could lightly smoke the spirit or infuse it with palo santo smoke if we were determined to capture these pyrolysis compounds.
Crowley, K.J. 1964. "Some terpenic constituents of Bursera graveolens(H. B. K.) Tr. et Pl. var. villosula Cuatr." Journal of the Chemical Society (0): 4254-4256.
The Good Scents Company. n.d. The Good Scents Company Information System. Accessed May 26, 2018. http://www.thegoodscentscompany.com.
Young, D.G., S. Chao, H. Casablanca, M.C. Bertrand, and D. Minga. 2007. "Essential Oil of Bursera graveolens (Kunth) Triana et Planch from Ecuador." Journal of Essential Oil Research 19 (6): 525-526.