Astringency in Cacao & Chocolate
The molecular basis of astringency in cacao and how to tame astringent chocolate.
We work hard to mitigate bitterness and astringency by fully fermenting cacao seeds. In experimenting with the unfermented style of cacao, I’ve become curious about astringency and other ways to reduce this quality in cacao. Join me as I start to make sense of astringency in chocolate, informed by scientific studies.
Astringency
As always, we need to be careful to define our terms. Astringency is commonly confused with bitterness, which is sometimes confused with sour. Confused? Let’s straighten it out. From a 2024 review on the role of bitterness and astringency in foods:
“Astringency is a taste that is specific to polyphenols… Astringency is a sensory attribute that is often described as a drying, roughening and puckering sensation in the mouth. Astringency is a common characteristic of anthocyanins, flavanols (including catechins, gallated catechins and procyanidins) and hydrolyzed tannins. Furthermore, it is a crucial factor in determining the quality of foods and drinks such as berries, red wine and chocolate. However, the mechanisms by which astringent polyphenol stimuli are recognized remain unclear.”
Astringency can be easily recognized as an unripe banana. It feels gritty and makes your mouth dry. When people taste wine, they pay attention to the feel of the wine. Does it feel rough and take away all of your saliva? That amount of astringency may be called “chalky” or “grippy.” Yet when well-balanced, astringency in wine is described as “velvety” or “structured.”
Just like in wine, astringency in chocolate isn’t inherently bad and even can be important to the “structure” of the experience. But it must be balanced. While sometimes out of proportion in properly fermented beans, high astringency is common in unfermented and partially fermented cacao beans.
Just as some people are more sensitive to bitter flavors, others are more sensitive to astringent sensations. While I enjoy bitter flavors quite a bit, I may be a super-astringent-sensor. Just like people can acclimate to bitter flavors, people can also learn to experience astringency as pleasurable. So there’s hope for me and people like me. But in the meantime, understanding astringency can help us find ways to smooth its rough edges.
Chemistry
Astringency in foods comes from different types of polyphenol molecules, some are more astringent than others. Cacao is one of the foods most rich in polyphenols, which is both a superpower and a super bummer, as we’ll see. Some of the familiar molecular subcategories of polyphenols are tannins, anthocyanins, and catechins. Tannins are well known as the drying molecules of red wine and black tea, and anthocyanins are famous as the molecules that give berries their deep color. Cacao has some anthocyanins, as seen in the deep purple color of some cacao seeds, but its polyphenols are mostly in the form of catechins, aka flavanols.
Green tea is also high in catechins, so the people thinking about astringency in tea may have insight for us in cacao. I enjoyed reading this tea masterclass. (Note the fundamental difference between extracting molecules out of tea leaves, which are then not consumed, and consuming the whole molecular party of molecules in cacao beans with nothing discarded.)
This paper determined that the molecules in chocolate most associated with astringency are: (-)-epicatechin, procyanidin B, procyanidin C1, and 2-phenolethan-1-ol. Interestingly, the study found that astringency was associated with floral notes, meaning they often come together.
Astringency is a sensation not a taste. This somatic signal has different receptors and travels different nerve paths to the brain. According to a 2024 review, the details of the mechanism of by which we detect astringency is unknown. The leading theory includes polyphenol molecules in our food binding to proteins in our saliva. However, recent evidence suggests that astringency can be perceived even without saliva. So, hmm.
Processing
The familiar stages of cacao processing breaks down polyphenol molecules. This 2022 review is summarized here:
Harvesting perfectly ripe pods maximizes the bioactive molecules, including polyphenols. This seems to suggest that over or under ripe seeds will be less astringent. Hmmm… not sure I would recommend that approach.
Pod storage after harvesting and before cracking may lead to changes in fermentation which reduce astringency and increase chocolate flavor.
Fermentation causes large decreases in polyphenols due to oxidation by enzymes in the seed and by diffusion out of the seed. The change in color from purple to brown is due to enzymes’ oxidation of anthocyanins into anthocyanidins.
Drying allows oxidation processes to continue, breaking down and transforming polyphenols, including into quinones, which are important for browning and flavor. I couldn’t find out if quinones are astringent, but they seem to be temporary.
Roasting breaks down polyphenols and can change the ones present. Higher heat and longer roasts decrease total polyphenols.
Grinding is not known to change the polyphenols. The authors of the review say more research is needed.
Conching has mixed results on whether it decreases polyphenol content. Some studies have found that the lighter (aromatic) polyphenols are vaporized, while others found little difference in polyphenol amount due to conching.
Tempering is not known to affect polyphenols.
It strikes me that the majority of processes affecting the polyphenol molecules in cacao seeds during processing are enzymatic. High-temperature fermentation and drying time are important to allow the enzymes to do this job. Cultures with a tradition of processing unfermented or lightly fermented beans always, or almost always, roast heavily. This dark roast will help reduce polyphenols at this step, although the reduction through high-temper fermentation will be more efficient.
Health
Polyphenols, with all their astringency, are healthy for our cardiovascular systems. But more is not necessarily better: Polyphenols need to be at a certain amount to effectively trigger the stress response known as hormesis. What is that amount? Ugg, who knows: It’s biology and thus “it depends.” Interesting to note, though, by taming the wild flavors in cacao, we might also be decreasing the health benefits.
Let’s Play
Now the fun part! When creating a drink or a chocolate confection, we can use a variety of flavors and techniques to mitigate, cover, or complement strong astringent sensations. Below are some time tested favorites and some new ideas for decreasing or balancing astringency in chocolate. Some will work for both eating and drinking chocolate, while some are just applicable to drinking chocolate. I hope you will try some of these for yourself by dividing a sample of chocolate into two, treating them differently, then comparing the astringency through a taste test. Please report your results below, so we can all learn!
Milk/Cream/Nuts
Milk and cream are time-tested ways to decrease astringency, used extensively in tea, coffee, and chocolate. This seems to work by molecules in the milk binding the astringent polyphenols so they are not available to be detected. A recent study showed that plant-based milks (oat and almond) worked as well as milk to decrease the friction, and thus the felt astringency, of molecules in tea. I’ve also seen references to fat molecules coating the mouth.
Almonds and milk are often added to unfermented chocolate drinks in Mexico. Two of my favorite additions to help with astringency in drinking chocolate are coconut milk and macadamia nut butter. I often grind macadamia nuts into eating chocolate, too.
Sweet Flavor and Scent
Sugar and sweet flavors can mask astringency. No shock there. What can’t sugar make delicious?
In Mexico unfermented drinking chocolate tablets are often half sugar (and also include spices). Unfermented Koko Sāmoa is usually served around that ratio, too.
What may be news for you, as it was for me, is sweet scents may decrease the perception of astringency, without a glucose spike. In this 2025 paper, the authors found that adding the sweet-smelling, aromatic molecules isoamyl acetate or whisky lactone reduced perceived astringency caused by tannins. That a sensation in your mouth can be altered by a scent is just very cool.
Heat & Water
We know heat applied during roasting decreases astringency, so try a darker roast for your astringent beans. For already roasted beans and finished chocolate, could simmering cacao in water for longer times have an effect? It’s interesting that some traditional drinking chocolate traditions call for the drink to be simmered quite a while before drinking. Koko Sāmoa is a good example: recipes often include simmering for hours. Caribbean cocoa tea is often simmered long, too.
In support of this is a 2023 study showing that incubating cacao powder in warm water changes its flavor. It’s too bad they didn’t try whole cocoa paste, but this is something we can try ourselves.
Viscosity & Polysaccharides (Starch)
Increasing viscosity and polysaccharide content decreases perceived astringency (reference). People often prefer viscous chocolate drinks, reduced astringency is likely not the only reason but could play a part. Corn thickens champurrado in Mexico, rice is combined with chocolate in the Philippines, and corn starch thickens the chocolate pudding dip for churros in Spain.
While I was at first surprised to read about he viscosity connection, I realize that I currently use this technique. Adding poi to thicken astringent chocolate does make it “smoother” and less astringent. I also put marshmallow root powder in drinking chocolate, which has a similar effect.
Flavorings
Herbs, spices, and other flavorings can diminish astringent harshness. The internet suggests cooling flavors like mint or spicy flavors like ginger, cardamom, and cinnamon. Chili pepper can help redirect your attention. Fruity flavors as flavoring or pieces of dried fruit in eating chocolate can help sooth astringency.
I have found that different chocolate batches match differently to inclusions, so some experimentation is required. If I taste a chocolate I think needs a paired flavor,I ask myself, “hmm… what would I want to take a bite of next?” Cherry? Almond? Cinnamon? That helps point me in a direction for experimentation.
Smoke
Unfermented cacao beans are often dark-roasted over a fire. The roasting helps break down some of the polyphenols, while the smoke flavor covers or complements the astringency.
Minerals: Clay & Water
For mineral impact on astringency, let’s take a look at the experiences of tea enthusiasts and experts. Tea drinkers are told that clay pots can reduce astringency in green tea. As I learned this, I immediately thought of the beautiful unglazed black clay pitcher I bought from Columbia. While clay pots have largely been replaced by metal, it is intriguing to suppose that this most ancient cookware may also have impacted the flavor.
Digging into this more, we find that tea aficionados can be particular about the pot they use for specific teas. Some types of clay can make fine teas taste more or less astringent. There’s theory is that minerals in the clay interact with molecules in the tea. I’m not going to be able to untangle this plethora of tea drinker experiences, but I think it is important to report that brewing vessel can make a difference, as shown in this research article.
Even more basic to tea drinking, we know that water choice will change tea flavor due to mineral content. Some minerals give an astringent sensation, and the interaction of minerals with polyphenols will also alter astringency. I didn’t find a resource that could simply explain these interactions, and I assume this is another complicated case where “it depends.” Water minerals must also affect astringency in cacao drinks. Perhaps the effect is not as pronounced since chocolate is more robust in flavor than delicate green teas. To test this, try the same chocolate made with different waters to gauge any change in flavor or astringency.
Aeration
One suggestion for reducing astringency in tea is aeration by pouring tea between two bowls for a couple of minutes. Sound familiar? Perhaps the ancient people of Mesoamerica were not just making copious foam by pouring chocolate, they were decreasing astringency.
I tried this myself with some very astringent unfermented cacao. I took half of the liquid and poured it between two bowls 30 times then tasted the samples side by side. While the astringency did not disappear, it did decrease. The change was not enough to entice me to repeat the effort.
Time
Of course, time can mellow, meld, and mix flavor of chocolate. Many tree to bar chocolate makers purposely leave their dried beans to sit months before roasting, and some chocolate makers will all chocolate to rest before tempering into bars. I’ve noticed this myself, but not specifically for astringency. It will be something I make sure to note in future batches.
What am I missing?
I hope this astringency primer is inspiring (or interesting). I’m still (always) on the learning path, so please do let me know what I’ve missed.
What is your experience with astringency in cacao and chocolate? Are you sensitive to it like me? Do you appreciate it as an important part of the chocolate experience?
What a super interesting and thorough article, thank you for these insights!