MOVE OVER, honey, the nutrition-conscious have a new sweetie. Prior preferences aside, the latest word in natural sugar substitutes is frozen undiluted apple juice concentrate.

Minute Maid publishes a recipe booklet that uses the frozen juice; Lotte Wolfe, director of the local Slender Shore diet spa, spikes bran muffins and orange souffle' with it; Nathan Pritikin preaches the stuff at his Pritikin Centers and in his books. "People are following fads. Frozen apple juice concentrate is a new fad," says Wolfe.

It certainly appears so. Whether for sweetening or drinking, according to Food Engineering, a periodical that covers the food industry, the "frozen apple juice category was one of the fastest growing categories in supermarkets during the year." Retail sales in 1981 surpassed $100 million, a 58 percent increase over 1980.

Local supermarkets are feeling the effect of frozen apple juice awareness, too. Giant initiated a private-label brand of the frozen juice in 1981 and spokeswoman Sue Portney said the chain "saw sales increase even more so since that went in the stores ." Ernie Moore, a spokesman for Safeway, said the chain's frozen apple juice concentrate sales have increased 30 percent since last year.

Business at Seneca Foods Corp., the largest manufacturer of the frozen juice, has been "explosive," said Eric Jaeckel, director of marketing there. There has been a "trend toward consumers drinking natural juices," he said, although he hadn't heard of the concentrate being used as a sweetener.

People seem to think it's more "natural."

"People are anti-chemical," said Slender Shore's Wolfe. At her spa, she used to sweeten muffins with Sweet 'N Low. Then people started refusing them.

One cup of the juice undiluted is about 464 calories; one cup of sugar is 770 calories, one cup of honey is 1,031 calories. (One cup of Sweet 'N Low has 550 calories and the sweetening equivalency of 5 pounds of sugar, say the company's dietary consultants.)

Compositionally, apple juice concentrate is less sweet than sugar. According to Dr. Gary Reineccius, a flavor chemist at the University of Minnesota, the undiluted juice contains 33.4 percent sugars. For comparable sweetness, then, it would seem three times as much apple juice as sugar would be needed, making the juice no caloric bargain.

But apple juice concentrate is primarily composed of fructose, or fruit sugar, which "for the most part, is perceived as being sweeter" than table sugar, or sucrose, said Reineccius. So even for non-dieters, using the concentrate in smaller doses than regular sugar is not difficult. It frequently leaves that impression of greater sweetness, and when used in excess it flavors foods with a strong fruitiness that may be inappropriate.

It's a psychological gimmick, said Dr. Aaron Altschul, director of the Georgetown University Diet Management Program. "People ought to use less sugar. If they can do it this way, fine."

Doctors Altschul and Reineccius don't put much stock in the preference of the concentrate over sugar for "natural" reasons. "Sugar is natural anyway," said Reineccius. "It comes from sugar cane and sugar beets."

The concentrate does contain some trace minerals not found in sugar, but the "nutrition values are the same," said Altschul. And, he said, the sugar in the juice can still decay teeth like table sugar.

As a sweetener, the concentrate is most often used undiluted. In dishes like apple gelatin or apple sherbet, where the juice is used more as a flavoring, it may be reconstituted. In small quantities, it works well against vinegar, and in sweet-and-sour sauces, salad dressings, and pickled vegetables. It is effective in reducing tartness--in recipes with plain yogurt, for example, or in fruit desserts that need a shot of sweetness. Because it defrosts into liquid, frozen apple juice concentrate wouldn't be a suitable replacement for a cup of sugar in a cake, but one to two tablespoons works in such baked goods as muffins.

Robin Rifkin, who cooks at the Pritikin Center in Downingtown, Pa., and who uses the juice religiously, said it can be substituted in any recipe that calls for sugar. "No, I wouldn't put it in a cup of coffee," said Rifkin, but she has used it as a sweetener in hot cereal or in Perrier (1 tablespoon per glass--they call it "Pritikin Beer").

Beware of overusing the concentrate; it suitably emphasizes the apple flavor in recipes that call for apples, but in recipes that don't, the apple taste may overwhelm. Two tablespoons in a 2-quart vegetable casserole may be indistinguishable; a half-cup in an oriental shrimp recipe will taste like apple juice and shrimp. Since sweetness sensitivities differ, it's important to taste and test. Here are some recipes for starters. LOTTE WOLFE'S BRAN MUFFINS (Makes 24 small muffins) 2 cups raw bran 3/4 cup skim milk 4 teaspoons frozen undiluted apple juice concentrate 1/2 teaspoon nutmeg 1/2 teaspoon cinnamon 1 teaspoon vanilla 1 egg yolk 1/4 cup unsalted sunflower seeds 3 egg whites, beaten 1 cup blueberries or apples, chopped

Grease miniature cupcake tins with vegetable cooking spray such as Pam. Combine all ingredients, adding beaten egg whites and fruit at the end. Bake at 350 degrees for 20 minutes. LOTTE WOLFE'S ORANGE SOUFFLE (6 servings) 6 oranges 1/2 orange rind, grated 1/2 packet unflavored gelatin 1/2 cup orange juice 1/4 cup evaporated skim milk 1 to 2 tablespoons frozen undiluted apple juice concentrate 3 egg whites

Peel oranges (reserving 1/2 rind) and pure'e whole oranges plus 1/2 rind through a food processor. In a small saucepan, soften gelatin in orange juice and heat until gelatin melts. Add dissolved gelatin to pure'ed oranges and allow to thicken, about 5 or 10 minutes. Whip evaporated skim milk until fluffy. Add apple juice to milk and fold into orange mixture.

Beat egg whites until they reach stiff peaks. Fold into orange mixture. Pour into parfait glasses and refrigerate. Or place in freezer and serve as sherbet. PICKLED BEETS (4 servings) 2 teaspoons frozen undiluted apple juice concentrate Pinch salt 8 whole cloves 1 clove garlic, peeled and chopped 3 1/2 tablespoons vinegar 2 tablespoons water 1 cup sliced cooked fresh beets or drained, sliced canned beets 1 small red onion, sliced into rings

Combine apple juice concentrate, salt, cloves, garlic, vinegar and water in a saucepan and bring to a boil. Pour over beets and onion rings. Cover and chill overnight. YOGURT SAUCE (Makes 1 cup) 1 cup low-fat plain yogurt 3 tablespoons frozen undiluted apple juice concentrate 1 teaspoon vanilla

Combine all ingredients and stir until smooth. Serve over baked fresh fruit. Adapted from "The Revolutionary 7-Unit Low Fat Diet" APPLE COLESLAW (4 servings) 2 1/2 tablespoons sour cream 2 1/2 tablespoons low-fat plain yogurt 1 teaspoon frozen undiluted apple juice concentrate 1 1/2 teaspoons lemon juice 1/4 teaspoon freshly ground black pepper 3 cups shredded cabbage 1 red apple, peeled and diced

In a bowl, mix together the sour cream, yogurt, apple and lemon juices and pepper. Add the cabbage, mix lightly, and chill. Just before serving add the diced apples and toss. Adapted from "Entertaining the Slim Way" MIDDLE EASTERN PORK CHOPS (4 servings) 1 medium onion, sliced 1 teaspoon chopped, peeled fresh ginger root 1/2 teaspoon cumin 1/4 teaspoon allspice 1 small stick cinnamon 1 clove garlic, minced 1 teaspoon butter 4 pork loin chops 4 teaspoons frozen undiluted apple juice concentrate 2 tablespoons lime juice 2 tablespoons chopped pistachios and quartered lime wedges for garnish

Using a large frying pan with a lid, saute' the onion, ginger, cumin, allspice, cinnamon and garlic in butter for 2 to 3 minutes, or until onion is well coated. Add the pork chops and brown lightly on both sides. Cover and cook on low heat for 30 to 40 minutes, or until tender. Remove chops to keep warm. Add the apple juice concentrate and lime juice to the pan drippings and onions and stir to coat over low heat. Place a chop on each plate and spoon onions over each. Sprinkle with nuts and garnish with lime wedges. CUCUMBER ONION SALAD (4 servings) 1 large cucumber, peeled and thinly sliced 1 large onion, thinly sliced 1/2 cup white vinegar 1/4 cup water 1 tablespoon chopped fresh dill or 1 teaspoon dried 1 tablespoon undiluted frozen apple juice concentrate, thawed 1/4 teaspoon black pepper

Combine the cucumber and the onion in a small, deep bowl. Combine the vinegar, water, dill, apple juice and pepper; mix well and pour over the cucumbers. Cover and store in the refrigerator for at least 1 day, stirring occasionally. From "The Pritikin Program for Diet and Exercise