The so-called Pritikin diet does not differ substantially from diets of other cultures where meat, sugar and salt are scarce but there are plenty of grains, fruits and vegetables. It carries the recommendations of the Senate Nutrition Committee's "Dietary Goals for the United States" several steps further.

The diet at the Longevity Research Institute is more restrictive than the maintenance diet. A 600-recipe cookbook, "The Live Longer Now Cookbook," by Jon Leonard and Elaine Taylor (Grosset & Dunlap, $12.95) outlines the maintenance diet. Its many don'ts will seem alien to most Americans.

Along with the recipes for soups and salad, main dishes, breads and desserts, a chapter is devoted to making low-fat cheeses and other substitutes for foods not available on the commerical market.

There are five commandments that form the basis of the diet:

Don't use fats or oils and avoid fatty meats such as bacon and sausage.

Don't use sugar or any simple carbohydrates such as molasses, corn syrup or honey. This includes the foods in which they found: pies, cakes, pastries, sugared cereals, breads.

Don't use salt or salty products such as salted crackers or salted herrings.

Don't use cholesterol, which means limiting total meat and fish intake to 1/4 pound a day and eliminating animal organ meats and skin, as well as shellfish and egg yolks.

Don't use coffee or tea. Drink decaffeinated coffee or herb teas.

Some recipes from the book follow. BEEF AND TOMATO LOAF (6 servings) 1 pound leanest ground beef 1 1/2 cups soft bread crumbs 1 small onion, chopped 1 small green pepper, chopped 1/2 cup skim milk 2 egg whites 1 teaspoon horseradish 1/2 teaspoon pepper 1 can (16 ounces) tomatoes, chopped into quarters

Mix together all ingredients except tomatoes. Gently stir in tomatoes. Pack in loaf pan and bake 1 1/2 hours at 300 degrees. Drain off any rendered fat. ORANGE SHERBET (Makes 1 1/2 pints) 6-ounce can frosen orange juice concentrate 1 1/2 cups skim milk 2/3 cup non-fat dry milk 3 drops vanilla

Combine all ingredients in blender and blend until well mixed. Place in freezer until firm. Serve topped with frest fruit and Grape Nuts for crunch. FRENCH TOAST (Makes 6 slices) 6 egg whites 1/2 cup evaporated skim milk Cinnamon 6 slices bread

Combine egg whites and skim milk. SPrinkle with cinnamon. Soak bread slices on each side in egg mixture, then cook in nonstick pan over low heat on both sides. Serve plain or topped with a fruit sauce. MOCK PORK SAUSAGE (16 one-ounce patties) 1 cup ground chicken breast 1 cup leanest ground beef 1/4 cup cold water 1/4 teaspoon pepper 1/3 teaspoon garlic powder 1/3 teaspoon sage 1&3 teaspoon savory 10 needles of dried rosemary, crumbled

Combine all ingredients. Shape into 16 patties and store in freezer until needed. Each patty will contain about one ounce of meat, making meat consumption easy to keep track of. When ready to use. Fry frozen patties in non-stick pan under pot lid at low to moderate heat until cooked through. SOUR CREAM (Makes 2 cups) 1/3 gallon skim milk 1/4 cup commercial cultured nonfat butter-milk

Combine ingredients and heat slowly to 95 degrees, stirring constantly. Cover, remove from heat, and let stand in a warm place until coagulated (one to two days). Turn curd into colander lined with four lavers of cheesecloth. Let drain 20 minutes. Then place colander into large pot, supported up off the bottom of the pot by a good four inches. (This four-inch clearance will insure that as the curd continues to drain, the waterline of the draining whey will not rise so high as to soak the curd and prevent further draining.) Place this whole draining assembly into a plastic bag, tie bag closed and pot in refrigerator for one to two days. Turn curd into a bowl and stir until smooth.