They might not be buying a lot of these products now, but by the year 2000 most Americans will be filling their shopping carts with items like bug spray, drain cleaners and English muffins - and leaving currently popular items like beer, baby products and barbecue supplies on the shelves.

Those are among the findings in a recent consumer product projection conducted by Supermarket Business, a New York-based trade publication, which set out to determine how demographic changes in the next decade will alter the profile of the supermarket customer.The biggest factor in the demographic shift will be the aging of the 82 million Americans born between 1946 and 1965, known as the baby boomers. They have been the target of retailers through infancy, childhood, adolescence and into adulthood. By the year 2000, according to Supermarket Business, "even the youngest will be over 35, so they will have slowed their buying of products that younger adults (18-34) favor and switched their purchasing power to products that middle-aged (35-54) adults covet."

Using different age groups and information about what those people buy, the magazine in its March issue forecast the likely demand for 364 different items, from adhesive bandages to yogurt.

For example, consumers aged 45 to 54 buy twice as many English muffins as those under 35, according to current consumer product research. So as baby boomers age, they will stop eating as much garlic bread and start buying more English muffins, according to the predictions.

Whipped toppings, gelatin and artificial sweeteners also are categories that get relatively little attention from the under-35 crowd, but are favorites of those from 45 to 64.

An older and more health-conscious population is also likely to mean more sales of diet soft drinks.

At the same time, the forecast for candy, chewing gum and pizza mixes is not good. As the boomers mature, sales of beer, wine and spirits coolers and champagne will drop while sales of vermouth and dessert-type wines will increase.

Outside the home, "the apparent laissez-faire attitude of younger homemakers regarding insect control appears to change as they enter middle age," concluded the magazine. "With this middle-aged group forecast to grow fastest in the 1990s, bug-bombing will increase in intensity."

But another popular outdoor activity - barbecuing - is a cooking style that draws less enthusiasm as people get older. Result: little growth in charcoal sales.

Not all of the sales predictions fit into neat demographic explanations. Take the projection that many household cleaning products are likely to be among the hottest products by 2000.

"There's going to be more individual households," said Supermarket Business senior editor David Litwak. "I guess every house needs a bottle of Lysol."