So why are acids so important in cooking? First of all, all our animal and vegetable foods are inherently either slightly acidic or neutral (neither acidic nor alkaline). That's just the way it is. So food chemistry, including the chemistry of cooking, is very sensitive to even slight changes in acidity. That's why the degree of acidity (expressed as a pH between 0 and 7) is critical to many of the chemical transformations that take place in cooking.
On the other hand, alkalinity (a pH between 7 and 14), the antithesis of acidity, plays virtually no role in cooking. Alkaline chemicals, being mostly unnatural in our foods, have generally deleterious effects on them and are rarely used in cooking. Nature has set the stage for that by making alkaline substances taste disagreeably bitter and soapy. All acids, on the other hand, add sourness -- a very useful tool in our arsenal of flavors.
Sure, ceviche is sour, but muy sabroso, no?
Robert L. Wolke (www.professorscience.com) is professor emeritus of chemistry at the University of Pittsburgh and the author, most recently, of "What Einstein Told His Cook: Kitchen Science Explained" (W.W. Norton). He can be reached at email@example.com.
Perspicacious reader Gretchen North of Bronx, N.Y., points out that Diet Sprite Zero trumpets on its label that it contains "0 carbs" and "0 sugar."
So what's new? Absolutely nothing, if you compare the lists of ingredients on Zero and on the "old" Diet Sprite. Sweetened as they are with aspartame and acesulfame-K, they never did contain any sugar or other carbohydrates. Why don't they tell us it contains zero saturated fats?
Have you noticed any silly things on food labels? Send your Labelingo contributions, along with your name and town, to Food 101, Food Section, The Washington Post, 1150 15th Street, NW, Washington, D.C., 20071 or to the e-mail address at the end of the column.