Over at the Times website, Harold McGee takes a question on salt and baking:
Q: Is there any truth to the old cook’s adage that adding a pinch of salt brings out the sweetness in sugars? If so, can you please explain the science behind it?
Harold McGee replies: I’m not sure that salt makes sugar taste sweeter, but it fills out the flavor of foods, sweets included. It’s an important component of taste in our foods, so if it’s missing in a given dish, the dish will taste less complete or balanced. Salt also increase the volatility of some aromatic substances in food, and it enhances our perception of some aromas, so it can make the overall flavor of a food seem more intense.
I don’t want to quibble with Harold McGee, as I’m such a big fan, but I think there’s a better explanation for why salt makes sweet things taste a little bit sweeter. Although the sweet taste receptor seems to be a G-protein coupled receptor, there’s also evidence that applying a sodium-channel blocker (TTX) can dramatically inhibit the activity of all taste receptors, suggesting that sodium plays a key role in the cellular detection of every taste (and not just the taste of salty things). Perhaps, and this is a pretty big perhaps, the extra concentration of salt when added to a dark chocolate souffle or a slightly bitter caramel makes it easier for the sweet taste receptors to fire an action-potential, since there are more sodium ions floating around the apical membrane. If so, that would explain why pastry chefs always add a pinch of salt to bring out the fullness of the other flavors. Just a thought.