Q: A friend of mine bought a juice machine and started making all types of vegetable drinks. After a while her skin took on a peculiar orange hue. The doctor said that she had consumed too much beta carotene, and that if she stopped drinking the vegetable juice, her skin would return to normal. I am worried that she might have damaged her body in some way. What do you think?

A: The doctor gave your friend good advice. The body converts beta carotenes, which are abundant in carrots, to Vitamin A. Excess beta carotene may produce an unsightly color but, unlike Vitamin A, it is not toxic in large amounts. With the elimination of the surplus dietary carotene, skin color will gradually return to normal.

There are two reasons why carotene is not toxic. First, the rate of conversion to Vitamin A in the body is a relatively slow process. Second, as the amount of carotene consumed increases, the efficiency with which it is absorbed decreases rapidly.

The high visibility of the carotenes, which turns the skin a bright yellow hue, is explained by the fact that they are stored in fatty tissue just underneath the skin.

Q: Can you tell me how tofu is made and provide information about its nutritional value?

A: Tofu, which is most commonly available in oriental groceries, is a curd made from dried soybean and water. After the beans are soaked, they are ground to a milky, cottage cheese-like curd and cooked under pressure to extract the whey. Next a solidifying agent is added, along with lemon juice, vinegar or calcium sulfate, and the mixture thickens. The thickened curd is then layered in special colanders, pressed and cut into cakes.

Nutritionally, an eight-ounce cake provides about 170 calories and about the same amount of protein as 2 1/2 ounces of lean meat. The protein is not of equivalent quality to that found in meat, but if combined with other protein foods it is used with equal efficiency by the body.

Finally, tofu contains some B vitamin and some iron. If calcium sulfate is used in preparing it, 8 ounces of tofu would provide as much calcium as a cup of milk. Tofu can be stored in the refrigerator for about 10 days. It is best kept under water, and to preserve freshness, the water should be changed daily.

Q: I have begun to prepare a garden and plan to freeze vegetables for the first time. Since I am unfamiliar with freezing fresh foods, I decided to do some checking. I was surprised to learn that vegatables must be blanched before they are frozen. Why?

A: Blanching, which can be done with boiling water or steam, or even in a microwave oven, inactivates enzymes which were necessary in order for the vegetables to grow and mature, but which cause undesirable changes in texture, color and flavor in the harvested produce. From a practical point of view, blanching also shrinks and softens the vegetables, saving space and making them easier to package.

To minimize nutrient losses and protect quality, it is important to complete the scalding process as quickly as possible and then chill the vegetables rapidly and thoroughly. This prevents spoilage that may occur if the vegetables are not well cooled before freezing. Before you are ready to harvest, you might want to contact your nearest Cooperative Extension Service Office for specific details about the home freezing of vegetables.

Q: I have a friend who goes from one outrageous quick-weight-loss diet to the next with equally unsatisfactory results. I would like to provide him with some sensible reading in hopes that he will take a more reasoned approach toward conquering his weight problem. Can you recommend a good book?

A: We suggest "Getting Thin" by Dr. Gabe Mirkin. It is a highly readable and comprehensive book, providing up-to-date information about the physiology of obesity. It discusses both the health and the social consequences of weighing too much and gives excellent suggestions. The diet plan allows for the flexibility out of which success is born. And there is an explanation of behavior-modification techniques to both realize weight-loss goals and maintain good eating habits.

Mirkin's particular interest lies in sports medicine. One of the real strengths of this book is the practical approach to developing a sensible exercise program crucial to maintaining weight. The book is published by Little, Brown in hardcover for $18.95 or in paperback for $8.95.