Elderhostel cooking classes for more 'seasoned' students.

Charlotte Weinstein, Betty Sprung, and Lillian Machlin have just broken for lunch after a three-hour cooking demonstration here at Johnson & Wales College. Caesar Salad, Scaloppine alla Marsala, Steak au Poivre, Fruits de Mer, Banana Flambe, and Cafe Diable had all been deftly prepared by Chef John Aukstolis and eaten with pleasure by the audience.

''Too much food,'' they complain in jest. ''And it isn't even noon yet!'' Mrs. Sprung moans.

They, and 36 others in the class, belong to Elderhostel, a program of week-long summer courses for senior citizens.

More than 600 institutions in the program here and abroad offer classes in everything from Transcendental Meditation to Canoeing to The Courage to Believe in a Skeptical World.

This week in Rhode Island it's food.

Monday began with a demonstration on American cooking; Tuesday was Italian; Wednesday Oriental; and this morning was tableside cooking.

Friday it will be vegetable carving and on Saturday hot and cold desserts.

''What brought you to Johnson & Wales?'' I asked Charlotte Weinstein.

''The air conditioning. I'm being honest. Plus there are two pools. An indoor and an outdoor. I've taken Elderhostels courses other places, but the accommodations here are just too gorgeous.''

It obviously wasn't any great interest in cooking that brought her here. ''For the holidays'' she continued, ''I'll make a little chicken soup with matza balls and maybe potato pudding and schmaltz herring. But I live alone and don't want to fuss. I still can't sleep if I'm having company the next day.''

Still, she enjoys the classes as well as the side trips to Newport, and it's a chance to escape the heat of New York to be with some of her friends.

After four days of cooking demonstrations, Mrs. Weinstein's friend Betty Sprung has been inspired.

''When I go back to New York, I'm going to make julienne vegetables - to make the plate look nice. I think I'll even sign up for a course in cooking techniques.''

Mrs. Machlin, too, has caught the spirit.

''Sesame oil. After yesterday's class on Oriental, I'm putting sesame oil on my egg noodles. Just a little. Maybe I'll sprinkle with slivered almonds. I'll serve it with my pot roast.''

''The way the chef taught us to bone a chicken! You wouldn't believe,'' Mrs. Weinstein adds.''Wonderful. Never again will I pay $3 a pound for boneless chicken breasts. Now I'll do it myself.''

Chef John Aukstolis - member of the faculty at Johnson & Wales, has been giving these cooking demonstrations for Elderhostelers here for the past three years. He is trying, he says, to restore the joy of cooking that may have been lost over the years.

''After all,'' he says, ''some of these people have been cooking for 40 years and it's become a job. I try to teach them not to cook because of tradition. That's when it gets boring. I tell them, 'Don't just do something because your mother did it that way.' ''

What's the greatest challenge in teaching these classes?

''Discipline,'' Mr. Aukstolis responds without hesitation. ''After all, these folks aren't used to getting discipline, they're used to giving it. Most of them have been cooking longer than I've been on this planet, and some of them think they wrote the book. I tell them the first day, 'This class in not a democracy.' But they love it and so do I.''

Mr. Aukstolis combines his demonstrations with a dash of wit and a heavy layer of show biz. The crowd loves it. Every time he flambed a dish, instamatics would flash like fireflies.

Although most of what Chef Aukstolis prepared was eaten without hesitation, the steak with peppercorns and squid in the seafood dish were looked on with some speculation.

Another just flatly refused to touch the squid. ''I've lived 64 years without squid,''she said. '' So why should I start now? Besides, John is teaching us desserts later and I want to save room.''

''He's a great teacher,'' says Herman Kurlander, who has come with his wife Flora. ''I know. I taught school 35 years.

''I just hope my wife is learning something. She likes everything overcooked and I like things undercooked. But after what the chef has been saying about overcooked food being tasteless, I think Flora will change her mind. I hope!''

''All you need is a white glove with sequins to make it on Broadway. You know , like Michael Jackson,'' said a lady in the front row as she stood up to take another picture.

What about Chef Aukstolis? Is he learning along with them?

''Every day,'' he says. ''Of course, they all want to give me their favorite recipes. I'll teach Elderhostel for the next 20 years if I'm here. The only thing I don't like is the name. Elderhostel sounds 'old,' and the one thing I learn over and over again is that age is nothing but a number.''

Here is a hearty soup based on the more traditional corn chowder, from the American cooking class.

Chicken and Corn Chowder

1/2 pound boned and skinned breasts of chicken

Flour for dredging

4 tablespoons butter

4 tablespoons vegetable oil

1/2 cup fresh or frozen corn

1/4 cup salt pork, diced

1 large onion, chopped

2 stalks celery, chopped

1 large potato, diced

2 quarts chicken stock

1/4 cup heavy cream

Salt and white pepper, to taste

Parsley, chopped for garnish

Dredge chicken in flour and saute in butter and oil until firm but not brown. Cool and dice.

Heat corn in a little water, drain, and puree in blender. (Some whole kernels may be saved and added to chowder before serving.)

Render salt pork in pot large enough to hold finished chowder. Add onions and celery. Saute until golden.

Add potatoes and chicken stock and bring to a boil. Add pureed corn and cook until potatoes are tender.

Stir heavy cream into soup and simmer 5 minutes.

Add corn kernels if reserved. Season with salt and pepper and top with parsley. Serves 5.

Courses at Elderhostel cost $150 per person double occupancy. For information write: Elderhostel Inc., 100 Boylston Street, Boston, Mass. 02116m