The chemistry of flavors, it’s all about the solvent

This post is for B, who wanted to cover more about different techniques to maximize flavors in cooking.

When you say a word like “solvent” most people think cleaning solutions, but more precisely a solvent is anything that holds solutes to make a “solution.” As every chemist knows, if you aren’t part of the solution you are part of the precipitate (thank you I’ll be here all night, be sure to tip your waitress).

There are two types of solvents or at least two broad ends to the spectrum of the liquids we call solvents. They are polar and non-polar. What does this mean? Well without getting too deep into the chemistry, polar solvents have areas that are positively and negatively charged because of unequal electron density across the molecule. I’ll give some examples without getting too deep into the weeds by starting with the two extremes found in cooking, oil and water. And we’ll cover the basic wisdom of “like dissolves like.”

Water, good old H2O is polar because the oxygen atom is more “electronegative” than the hydrogen atoms, which makes the oxygen area have two more negative areas, and the hydrogen atoms each have a positive area. Polar solvents will easily dissolve ionic substances like table salt. A lot of minerals in food are water soluble (because they are in their ionic form) and some vitamins.

Cooking oils, have a much more even distribution of electrons so there aren’t obviously charged areas of the molecule, and this means they won’t dissolve salt as easily. Cooking oils have long chains of carbon and hydrogen which allow them to interact with the carbon hydrogen structures of complex flavor molecules like cinnimanaldehyde (cinnamon flavor) or capsaicin (hot pepper flavor). Some vitamins are very fat soluble, like vitamins E and A.

In between these two extremes exists alcohol and vinegar. Both alcohol and vinegar are more polar than oils, but less polar than water. This is because they have an oxygen atom hanging out on one end of the molecule, but enough of a carbon structure on the other end to insulate the hydrogen atoms from being too positive from the pull of the oxygen. This is why vanilla extracts are done in alcohol, the vanillin molecule has eight carbon and three oxygen atoms, so it is dissolved better by alcohol than either oil or water. This is also why many hot sauces use a vinegar base, it pulls the capsaicin nicely without getting as hot as something like “Mongolian Fire Oil” which uses oil as the solvent.

There is obviously way more to learn about food chemistry than what I’m writing here. But that is a basic background on using solvents to dissolve something. In cooking, you want to dissolve flavor molecules so they can interact with your senses of taste and smell.

And speaking of taste and smell. The olfactory sensors, over 300 different ones, smell different things. Your mouth has two families of taste receptors, that are are generally broken down into sweet, sour, bitter, savory, salty, hot, and cold (yes hot and cold exist as flavor receptors, which is why mint seems cool and pepper seem hot). How your brain interprets that is a synthesis of the two. If you eat with your nose plugged, you’ll have a different taste experience than with your nose open. This is one of the reasons why chefs add freshly chopped aromatic herbs to a dish just before serving, it doesn’t change the taste profile of the dish, but adds more “kick” to the aroma as the food heats the herbs releasing the aromatic compounds. Please note I’m using the word “aromatic” to mean things that are easily smelled, not the chemistry definition of “aromatic” which has to do with the structure of the molecule.

Remember that “like dissolves like” so you’ll want to dissolve polar compounds with a polar solvent, and non-polar compounds with a non-polar solvent. As an illustration, which has more impact on your nose, mint tea or mint extract in oil? The menthol (solid mint oil) is very non-polar aromatic molecule but has one oxygen atom which means it can be dissolved a little in water to make a pleasant tea or dissolved in cocoa butter to make strong mint candies. When in doubt about the flavor you are looking to extract, alcohol is generally a good middle ground, and alcohol cooks out very quickly. Alcohol has a lower boiling point than water, which means that it phase changes from liquid to a gas more readily and at a lower temperature, so pretty much no matter your cooking technique, there will be very little residual alcohol in your final dish (unless you add it right at the end because you want alcohol there).

But what does this mean to you as a cook? Well it means that you should experiment with different flavor extraction techniques in your cooking. Say you are trying to make a French “pot a feu” and the bouquet garni (bundle of herbs) just didn’t give you the flavor profile you were really looking for (maybe you didn’t use enough herbs). Maybe you’ll remember what I wrote here and bring a small amount of water to boil, steep a fresh bundle of herbs (or even loose dried herbs from your pantry) and then throw in a couple shots of vodka (cheap vodka is a great cooking tool for flavor extraction) to up extraction properties of the solvent. Then you can strain the loose herbs through a coffee filter and put the liquid back into your dish.

And so there it is, you want to use liquids that extract the most of the flavor you are looking for in your foods so you can get the most impact on the mouth and nose.

Feel free to ask questions, or point out something I didn’t cover.

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One Response to The chemistry of flavors, it’s all about the solvent

  1. B says:

    Makes sense. That’s what the magic in angostura bitters is. Reading this blog has opened my inner chemist. I guess I’ll stick around and pepper (pun intended) you with my comments. No thanks necessary 😀

    Like

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