Esters: The Secrets Behind the Sweet Aromas of Cannabis

Cannabis Cups in the past year have seen a wave of banana and strawberry aromas that leave all the judges in awe. Common terpene profiles don’t do these strains justice, so what are these tasty strains hiding? Dabbers and vapers beware; these volatiles require extra low temps for full flavor.

Most cannabis labs these days test for a variety of terpenoids including beta-myrcene (herbal, spicy, sweet), terpinolene (fresh, sweet, lemon), beta-caryophyllene (woody, spice, dry), caryophyllene oxide (sweet, spicy woody), beta-pinene (pine, woody, hay), alpha-pinene (fresh, camphor, pine), linalool (floral, citrus, rosewood), d-limonene (orange, lemon), etc. Seems like a long enough list, right? Frankly, not even close. A comprehensive analysis from 1995 of the volatile components of cannabis from the University of Mississippi found 68 terpenes and volatile constituents. The aforementioned terpenes certainly make up the majority of the volatile oil by mass, but the rest of complexity of cannabis’ aroma lies in the minor terpenes, ketones, esters, alcohols and ethers.

What makes fruit smell like it does in the wild? For bananas, the main chemicals responsible are isoamyl acetate, 2-pentanol acetate, 2-methyl-1-propanol and hexyl acetate. In the case of strawberries, the main volatiles include methyl butyrate, ethyl butyrate and methyl hexenoate. For pineapples, volatile compounds such as ethyl-2-methylbutyrate, methyl-2-methylbutyrate, 3-(methylthio)propanoic acid ethyl ester, ethyl hexenoate, etc, make up their characteristic smell. While a lot of those words will sound like complete gibberish to most, thinking back to high school chemistry might help to remember what the odor profiles of those three fruits have in common: esters. (Hint: the suffix “-ate” means ester).

If these esters are essential to producing banana, strawberry and pineapple aromas that make the market’s most popular strains smell so great, why don’t they show up on the radar of most cannabis labs? Banana volatiles like 2-methyl-4-heptanone and hexyl acetate are not very abundant in the fresh or dry cannabis flowers, sometimes at levels 200 times less than the most abundant terpene in cannabis, beta-myrcene. It takes a sensitive and expensive analysis to detect these chemicals, but most importantly, the labs need to know what compounds to look for.

Check out the list on page two; of the 68 terpenes listed, only 2-methyl-4-heptanone, 2-methyl-3-heptanone and hexyl acetate can account for truly fruity aromas, how could cannabis elicit so many different aromas without seemingly producing all the terpenes required to smell like pineapple, banana, strawberry or blueberry? Our sense of smell is more complicated than what meets the nose.

When an odorant molecule enters the nose, it binds to a variety of different olfactory receptors at different strengths creating a “combinatorial code” that defines a given scent. The combinations are almost limitless, making it almost impossible to predict with certainty how a given molecule will smell by simply looking at the structure. For example, according to research from the University of Nice in France, the combinatorial code that “unlocks” a fruity smell is: OR1A1, OR1A2, OR1G1, OR1L3, OR2AG1, OR2G2, OR2J2, OR2J3, OR2M4, OR2T10, OR2T34, OR2W1, OR4E2, OR4Q3, OR52D1, OR5AC2, and OR5K1. If a molecule activates these receptors it will smell like fruit, and a different grouping of receptors corresponds to the “green” smell, different one for the “floral” smell, etc. Our knowledge on the sense of smell is growing but a lot of complex relationships still exist we have not fully uncovered.

It’s feasible that a certain mixture of several compounds could elicit a strawberry, pineapple or blueberry aroma without actually containing any of the chemicals present in the fruit itself. Like the puppet master of olfaction, cannabis puts on an elaborate display of aromas playing the part of the most delicious fruits and spices nature has to offer.

How does one take full advantage of the delicious fruity esters? The two banana compounds that scientists have detected in cannabis for sure, 2-methyl-4-heptanone and hexyl acetate, occur at low levels, and have low boiling points. 2-methyl-4-heptanone boils at around 311 °F, and hexyl acetate boil at 340 °F. Compared to beta-caryophyllene (510 °F) and linalool (388 °F), the banana terpenes not only volatilize more quickly, but high temps make them decompose into give nasty, acrid flavors completely unlike the fresh product.

The best way to conserve those fruity flavors is to turn the vape way down to around 340 °F or less. For dabbers, this means putting waiting longer than normal for the nail to cool down, enough so that a puddle of oil always remains without vaporizing. Smoking banana and pineapple flowers will denaturize most of the fruity flavor, but you won’t be disappointed. If you keep your nose peeled for those intoxicating banana and pineapple scents, you’ll be sure to find some great flower or dabs, just remember to keep the temperature down for the fullest flavor.

Photo Credit: Strawberry Cough by Danny Danko





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