Q. I took a course in Chinese cooking, and enjoy preparing all sorts of new dishes. But I try to watch my salt intake, and it seems to me that many of the seasonings I am using are pretty salty. Can you give me information about the sodium content of some of the more common prepared sauces used in Chinese cooking?
A. A couple of years ago, analyses of the sodium content of Chinese sauces revealed a few surprises. Some sauces contained less sodium than expected. But one of the problems with the findings is that there is considerable variation from brand to brand. And in some cases, even samples of the same brand were different from each other. Despite their limitations, these figures provide some useful guidelines.
Soy sauce is probably the most popular. Analyses of six brands of dark sauce (sodium content is unrelated to the color) found a range of between 299 and 493 milligrams (mg.) per teaspoon. Three brands of light sauce contained anywhere from 318 to 525 mg. And one brand of soy sauce with reduced sodium which we checked contained just 200 mg. per teaspoon. As a point of comparison, a teaspoon of salt contains 2,100 mg. of sodium.
Only one brand of brown bean sauce was tested. At 426 mg. per teaspoon it provided one of the more generous amounts of sodium. How this figure might vary from one brand to another we do not know. Oyster sauce, another popular seasoning, contained between 213 and 328 mg. of sodium per teaspoon. Average values for two brands of hot bean sauce were similar. The single brand of hoisin sauce and the two brands of sweet bean sauce contained about 160 mg. per teaspoon. Satay sauce had the least, only between 51 and 78 mg. per teaspoon.
These figures suggest that by using generous amounts of garlic, onion and other condiments that are low in sodium, it should be possible to control the amounts of the saltier seasonings, create fine Chinese dishes and at the same time keep your sodium intake within reasonable limits.
Q. Are cantaloupe and honeydew melons nutritionally equivalent?
A. Not entirely. The clue to the major difference between them is color. The orange hue of cantaloupe indicates that it is an excellent source of beta carotene, which the body converts to vitamin A. A single cup of the melon more than meets the entire Recommended Dietary Allowance (RDA) for the nutrient. Honeydew, on the other hand, does not contain appreciable amounts of beta carotene.
Beyond that difference, the two are similar. A cup of either provides about 60 calories and meets the RDA for vitamin C. They also contain as much potassium as you would get from a cup of orange juice. And both provide small amounts of other vitamins and minerals.
Incidentally, 90 percent of the weight of both these fruits is water.
Q. I have noticed calcium chloride on the ingredients list of canned tomatoes. What purpose does it serve?
A. As they occur in growing plants, pectic substances -- components of fiber that help plant cells to adhere to one another -- are insoluble. With heat, they are converted to water-soluble pectin. This produces some separation of the cells and contributes to tenderness.
But in the case of tomatoes and certain other fruits and vegetables, it is important to maintain a degree of firmness. This is where calcium salts come in. They can combine with the pectin to form an insoluble compound called calcium pectate. When produced in the tissues of the tomatoes, this compound increases structural rigidity, thereby helping to maintain the desired texture.
Q. Do breast-fed babies need iron supplements?
A. It appears that normal babies who get all of their nutrients from breast milk do not need an iron supplement until the second six months of life. It is true that human milk, like that from other mammals, is a poor source of iron. Moreover, the iron content of the milk if variable. Apparently, it is not related to the mother's iron status and tends to decline during the course of lactation. Yet about 50 percent of the iron it does contain is absorbed, making it the most available form of the nutrient. And normal infants are born with stores that can provide the remainder of what they need.
In the most recent evaluation of iron status in 33 exclusively breast-fed infants, investigators from the University of Arizona Health Sciences Center found no evidence of iron-deficiency anemia, and just two cases in which there were indications of depleted iron stores.
Solid foods can adversely affect the absorption of iron from human milk. This may explain why the results of some studies have suggested a need for iron-fortified cereals or iron supplements at an earlier age in breast-fed infants. Incidentally, it has also been conjectured that giving iron supplements earlier may interfere with some of the anti-infective benefits of human milk.
Q. As we were preparing to leave on an extended trip, I discovered a dozen eggs in the refrigerator. None of my neighbors was home, and as it was a warm day I didn't want to leave them sitting on a doorstep. I ended up throwing the eggs out. Could I have frozen them?
A. Yes. Removed from their shells, eggs can be frozen whole, or separated and then frozen. Specific directions will depend on which option you choose.
Whole eggs can be frozen without adding anything, but will retain their cooking properties better if beaten with either a tablespoon of sugar or corn syrup, or one-half teaspoon of salt per cup of eggs. Which you choose will depend on how you plan to use the eggs.
Egg yolks must be frozen with a stabilizer, or they will be viscous and gummy when thawed. Again, use either sugar, corn syrup or salt in the same amount you would use for whole eggs. When thawed, one tablespoon is equivalent to the amount in a large egg.
The whites can be frozen "as is" and, when thawed, can be expected to whip to the same volume as if they were fresh. Two tablespoons are equivalent to the white of a large egg. Like other frozen foods, eggs should be thawed in the refrigerator.