Molecular Gastronomy for Brewing

I recently finished up a free molecular gastronomy course (basically, the science of delicious things) offered by the University of Hong Kong through the website  The focus was on food, but some of the things were applicable to beer as well.  Here, I would like to share some useful things you might want to consider for your next brewing or tasting session.

humulone alpha acid

The humulone alpha acid carbon backbone structure with the side groups replaced by hop cones… just for giggles.

I tried to organize this post as best as possible, but it is by nature scattered bits of information I was able to glean from the class that I could relate to brewing.

Sensory Perception: Aroma is enormously important.  Of all the things we can taste, we do so by putting together just five (yes five, not four!) kinds of tastes: sweet, sour, bitter, salty, and umami (literally Japanese for “yummy,” but we know it better as savory, the taste of amino acids and proteins like meats and cheeses).  Additionally, there are pain sensors that can sense the capsaicin of spicy foods and temperature sensors that also play a role, though these aren’t flavor receptors per se.  Compare this to the whopping 374 different types of aromatic detectors in the human nose.

Enhancing Perception: Exhale briskly after swallowing your food or drink to force the volatilized aromatics into the nasal cavity to enhance your perception of what you are consuming.  It is estimated that about 80% of what you taste is actually perceived through the nose.

Strawberry Beers: For anyone who has tried to make a strawberry beer before, you probably know its devilishly hard.  As it turns out, strawberries don’t have any flavor- absolutely everything you perceive about them is in the aroma and mouthfeel.  For some reason, my wife found this fact to be completely unacceptable when I informed her.  These substances, like ethylbutyrate among many (many) others, are extremely volatile by nature, and do not lend themselves to being preserved during the brewing process.  Any addition of strawberries to beer or mead (if you absolutely feel like you must), should be done in a manner to preserve these volatile compounds.

Sensory Congruence: Sensory congruence happens when your brain associates certain tastes and smells with others.  Many smells, such as fruity or vanilla, cause a perception of greater sweetness even if there is no extra sugar, because things that are fruity or have vanilla are usually sweet.  There can also be a “non-congruence”, where a smell associated with sweetness can decrease the perception of sourness or bitterness (vanilla aroma makes cocoa seem less bitter- that’s why it is frequently added to chocolate).  So, adding vanilla extract to a dry stout can make it seem sweeter, and fruity aroma from yeast or the hops themselves will decrease the perception of bitterness in an IPA (a perfect example is my 100% brett IPA).  This principle should also be considered when pairing food with beer for tastings or beer dinners.

Volatilizing Aromatic Molecules: Salts and acids both decrease the solubility of aromatic molecules, forcing them to come out of solution more easily so you can perceive them.  This is why both increase the intensity of flavors in food and drinks (think adding salt to a dull unsalted chicken breast).  Stepping into the realm of speculation, I wonder if the different salts used in water treatment for brewing help to volatilize different aromatics- some for hops and some for malt.

In general, thicker solutions also decrease the intensity of flavors.  In terms of food, this can mean a less flavorful sauce when more thickening agent (flour, corn starch) is added, but with beer the “thickening agent” (grain) is also highly flavorful, so a balance is generally maintained.  The only potential issue is aromatic compounds (from the malt, yeast, or hops) will be released more slowly to your nose in a higher final gravity beer.  This is probably one of the reasons Vinnie Cilurzo of Russian River Brewing insists on adding sugar to his hoppy beers like Pliny to ensure they finish dry and thin them out a little, whether he knows it or not.

Clove Flavor in Beer: The clove flavor prized in wheat and some Belgian beers comes from the breakdown of ferulic acid to 2-Methoxy-4-vinylphenol through a process called decarboxylation (which is a fancy term for CO2 being released) as such: C10H10O4→C9H10O2.  This will happen thermally during the boil and enzymatically during fermentation.  Even after a three hour boil there isn’t quite enough 2-Methoxy-4-vinylphenol to taste, and only some yeast produce the proper enzyme.  This is why a true hefe-style wheat beer must use a hefe yeast.

Some plants contain ferulic acid, a compound that keeps certain plants rigid even after periods of extending boiling by binding together their cell walls.  This is why Chinese water chestnuts remain crunchy while spinach wilts.  It is contained in small quantities in wheat husks and barley husks.  Perhaps by adding certain plants with high levels of this compound to the mash or boil, one could increase the ferulic acid content of the wort and the resultant clove flavors?  According to wikipedia, flax seed has an especially high concentration.  As it turns out, basically all wine yeasts will break down ferulic acid, but ferulic acid is not present in grapes, so wine doesn’t taste like cloves.

Solubility of Spices: Different flavors are soluble in different compounds- some flavors are more soluble in water (hydrophilic), while some are more soluble in oil (hydrophobic).  As far as herbs and spices go, leafy things like basil tend to have compounds which are water soluble.  On the other hand, bark, twig, and seed items like anise or vanilla typically contain compounds which are more soluble in fats and oils.  In this case, it can be very beneficial to create an extract of the flavor using a common solvent like ethanol (common meaning it will dissolve in both water/wort and the spice); any of your cheap clear liquors will do the job, the higher the proof the better.  So, don’t just throw something into your beer- research the ingredient first to determine how best to add it.

– Dennis,
Life, Fermented


About Dennis
Home brewer, home chef, garage tinkerer. Author of Life Fermented blog.

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