There is no conception in man's mind
which hath not at first, totally or in parts,
been begotten upon by the organs of sense.
---Thomas Hobbes, Leviathan, 1651

Monday, August 24, 2009

Suppress me and call me sweet

A loyal reader sent in a question that well illustrates a common sensory effect we encounter just about every day in one way or another. She noted that coffee makes chocolate taste better, and wondered why?

This effect is known as adaption and suppression. But that's getting ahead of ourselves. First, lets talk about basic tastes (sic) in chocolate and coffee. Chocolate primarily has bitter and sweet tastes (taste being what you perceive on the tongue). Black coffee has a strong bitter taste, and hardly any sweet. As an aside, the other compounds in both chocolate and coffee that give them the great flavors we all know and love are mostly "volatile" compounds that are perceived by the olfactory bulb in the upper reaches of the cavernous nasal cavity, which are unimportant for the illustration of this effect.

Adaptation occurs when we repeatedly perceive something over a short period of time. When this happens, our ability to perceive that particular thing becomes lessened. For example, how many of you notice right now that your saliva is salty? None of you, right. However, if we were to completely dry the saliva off of your tongue for a few minutes and then let it replenish, you could perceive the saltiness for a few seconds or minutes before you become "adapted." Another illustration - how many of you feel the texture of your clothes against your skin? Or hear the hum of the air conditioner? Adaptation is the body's way of filtering out sensory information so that we can pay attention to new events, which tend to be the most interesting or important.

Lets look at some (fake) data that illustrate adaptation and suppression with chocolate and coffee. Assume that on separate occasions you taste both pure coffee and chocolate and rate their bitter and sweet tastes on some scale. On the third tasting session, you take a big sip of coffee and swish it around in your mouth, and then immediately taste the chocolate. You've used the coffee to adapt your palate to the bitterness, thus suppressing the bitter level of the chocolate. The chocolate will taste sweeter, and most people like this.

This type of effect happens all of the time during meals, and chefs have to pay particular attention to it from one course to the next lest some adaptation effect causes a perfectly balanced dessert to taste extremely bitter because it was preceded by a too-sweet sorbet. Regular wines aren't paired with desserts because the overwhelming sweetness in most desserts would adapt your palate to sweet flavor, thus making the wine become bitter. Sweet dessert wines don't get overpowered as much. And the biggest challenge to chewing gum lasting forever is your palate becoming adapted to the constant flavor stimulus, not gum itself being unable to release flavor for a long period of time.

The dessert above is the "Chocolate and Coffee Sampler" from the Fall 2005 menu in the American Bounty Restaurant.

If you have any questions about sensory effects during meals or otherwise please feel free to email me and I'll do my best to address it in an upcoming entry!

1 comment:

  1. This reminds me of the old anecdote about the frog in boiling water - remember? Put a frog in boiling water and it will hop out; put him in cold water and slowly turn up the heat and he will be cooked to death. Adaptation is a pretty strong effect in many instances. Although I don't think the frog story would really work.