By Robert L. Wolke
Wednesday, October 11, 2006
Years ago, when my mother was teaching me to deep-fry potatoes, she told me the fat should always be hot enough to cause the potatoes to bubble instantly. That would keep them from becoming greasy, because grease can't seep into the potatoes while air is being expelled. Nowadays, to reduce fat and calories, I use the "oven fry" method of spraying the potatoes with oil and then roasting them. But it would seem that either method results in potatoes coated with oil.
Coated, yes. But without a lot of fat inside the potatoes.
The idea behind the oven method is that you are in complete control of how much fat you'll be eating, whereas deep-frying is a crapshoot, because so many factors are involved. The most important factor, however, is indeed the temperature of the fat. (Always listen to your mother.)
When food is put into hot fat for deep-frying, the water in the surface layers quickly reaches its boiling point and produces steam. The steam (not air; sorry, Mom) surges out of the food and prevents fat from getting in, like the boor who tries to enter an elevator before people can exit. If the fat is not hot enough, the ejected steam won't be forceful enough to keep the fat out. When the steam ejection is weak or begins to tapers off, two things happen: (1) Some fat can enter the channels left by the escaping steam, and (2) the fat can get the food's surface hot enough to dehydrate and brown it. So the less time spent at this stage, the less fat in the food.
One popular, effective method of frying starchy foods such as french fries involves cooking the potatoes for 8 to 10 minutes in lower-temperature fat (300 to 325 degrees), then letting them stand at room temperature until it's time to fry again at a higher temperature and serve. The lower temperature of the first round causes the starch granules to absorb water and burst, spilling their gummy starch, which then glues the potatoes' surface cells together into a crisp crust. Many restaurants buy pre-cooked potatoes and fry them off just before serving.
The oil for that final frying should be maintained between 350 and 380 degrees (bearing in mind that adding food drops the fat's temperature precipitously). The food should not be left in the fat more than a minute or two after it stops steaming. The finished food should be blotted on paper towels, not drip-dried. If those measures are observed, there should be no more fat in french-fried potatoes than in oil-coated, oven-roasted spuds.
I have a PhD in natural products chemistry and have worked with food chemistry and development for many years. As a flavor chemist, I believe you are quite right that vodka adds no flavor whatsoever to a food dish [Food 101, Sept. 27]. However, if used properly, vodka can create flavor components from food ingredients before the cooking of a dish is actually completed.
Vodka's popularity is such that when I write a column about it, I can expect a flood of e-mails from aficionados, especially if the column denigrates their revered nectar, as my last one did by doubting that it can add any noticeable kick to a pasta sauce. According to Barbara Kafka in "Food for Friends" (HarperCollins,1989), pasta with vodka sauce was invented during Italy's nuova cucina (new cuisine) movement of the 1970s and became trendy in the United States in the mid-1980s. Recipes for Penne Alla Vodka are still being pitched by Mario, Emeril, Lidia and Rachael, among others.
But to address the comment: Yes, that's quite possible. When an alcohol-containing tomato sauce is simmered, the alcohol can react with the tomato's acids to produce compounds called esters, which add fruity flavor notes. Some of the alcohol may also be oxidized to form traces of aldehydes, which have potent flavors as well.
Thus, adding the vodka before the sauce is simmered can well develop flavors beyond the (negligible) flavor of the vodka itself. In many recipes, however, the vodka is added near the end of cooking, in which case I still maintain that its contribution to flavor would be nil. Long heating is what makes these chemical reactions happen.
From another reader:
Cooking the tomatoes and other items in vodka breaks them down more completely, resulting in a sauce with a smoother texture. A thicker, smoother texture is more desirable because it clings to pasta better. The next time I make vodka sauce, I'll take you up on your challenge of making it with and without vodka and see which one tasters like better!
Whoa! We're not cooking them in vodka. A few tablespoons of vodka in a couple quarts of sauce makes a mixture containing only about 1 percent alcohol. I can't believe that such a minute concentration of alcohol could soften the texture of tomatoes or other solids (even if pure alcohol did that, which is unlikely at best).
But as a scientist, I cannot accept or reject a hypothesis without some convincing evidence one way or the other. So here's my deal: I'll keep my mind open and await the results of the Great Vodka Sauce Taste-off. Then, if it is found that the vodka really does make a difference in texture, I'll buckle down and try to find out why that happens. Fair enough?
Labelingo: A prominent red blaze on the front of a package of Nature's Path Organic Instant Hot Oatmeal boasts that it contains "50 grams per serving!" (their exclamation point). Not 50 grams of anything in particular, just "50 grams."
Gosh! Grams must be really good for me. I'm gonna eat a lot of that stuff.
Have you noticed any silly things on food labels or in food advertising? Send your Labelingo contributions, along with your name and town, to Food 101, Food Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071, or to the e-mail address below.
Robert L. Wolke (www.robertwolke.com) is professor emeritus of chemistry at the University of Pittsburgh. His latest book is "What Einstein Told His Cook 2, the Sequel: Further Adventures in Kitchen Science" (W.W. Norton, 2005). He can be reached at email@example.com.