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Question: What are yeast extracts and why are they added to some processed foods?

Answer: Yeast extracts are simply concentrates of the soluble part of yeast cells. Because they have what food technologists call "meaty" flavor and are quite economical, they are widely used as flavor enhancers by the food industry.The major source of the raw material is the so-called "spent" brewer's yeast from the beer industry. Spent brewer's yeast has a strong and robust flavor, but also a bitter and beerlike quality. Yeast grown for use exclusively as flavoring, called "primary grown yeast," is considerably more expensive. Its milder flavor makes it more desirable for some purposes. Currently about 35,000 metric tons of yeast extracts a year are used worldwide. Representing as little as 0.1 percent to 0.5 percent of the weight of foods in which they are used, they add up to a $190 million a year industry.

Yeast extracts, which are commercially available as pastes or powders, are produced in several different ways. The method most widely used in this country, autolysis, is a carefully controlled process in which components within the cell are made soluble by activating enzymes that are also present in the cell.

Question: My son brought home a picture of the new Food Guide Pyramid that the government is using to help teach us how to eat. In looking at it, I was curious about why beans were in the section with meat. Shouldn't they be with the grains?

Answer: It is possible to argue, quite logically, that beans fit in either spot. They are an excellent source of protein, which is of a relatively high quality. A single cup provides about the same amount of protein as 2 ounces of meat, fish or poultry. The protein is not of quite the same quality, but when eaten with proteins from other sources, the total "pool" of essential amino acids is comparable to what you would get from eating animal protein.

At the same time, beans provide considerable amounts of carbohydrate. A single cup of beans provides the carbohydrate in 21/2 slices of bread, and beans are rich in fiber. So they could appropriately fit into the base of the Pyramid along with pasta, rice and other cereals.

Besides protein and carbohydrate, beans provide B vitamins and considerable iron. The most important point is that beans are an excellent, economical food. Regardless of where they belong in the Pyramid, it is a good idea to eat them often.

For many people, the major obstacle is that they are perceived as tedious to prepare. That is not really so. Preparing them to soak overnight takes no more than a minute. Draining, adding water, an onion, clove, pepper, bay leaf, garlic and a bit of salt and turning on the burner takes, at most another minute and a half. Then they simply cook for an hour or two. Cooked dried beans can be frozen for later use, cutting the preparation time still further. Once prepared, a good Mediterranean cookbook can provide a wealth of simple ideas about excellent ways to serve them.

Question: Is it true that breast-fed babies are leaner than bottle-fed babies?

Answer: Studies of that question over the past two decades have provided mixed results, but the most recent investigation suggests that they are leaner.

Early studies also found breast-fed babies to be leaner, but formulas have changed and so, too, have parents' attitudes, with much less of a tendency to overfeeding. So the results of the early studies may not be relevant to today's babies. Later investigations produced mixed results, although most did not show a difference. And when researchers studied children between ages 3 and 8, they found that differences in weight were unrelated to the type of infant feeding. But in these studies, the duration of breast-feeding was short and problems with the way the studies were designed may have masked differences.

The DARLING (Davis Area Research on Lactation, Infant Nutrition and Growth) Study was designed to assess differences. It included one group of infants breast-fed for at least 12 months and a second group who were formula-fed for the same period. None of the infants received solid food until they were at least 4 months. By the time the two groups were 7 months and up to their second birthdays, the formula-fed infants were significantly fatter; the gap was widest between 9 and 15 months of age. The difference was attributed to higher caloric intake, with breast-fed infants apparently self-regulating their caloric intake. The key question of whether less body fat during infancy affects adult weight remains to be answered.

Washington Post Writers Group