Fast food is invading the supermarket and slow-cooking food is moving onto the fast track. Snack foods are changing shapes and sizes -- but not content -- and every other product -- including Jell-O -- is going upscale.

At least that's the word from the Food Marketing Institute's annual convention, held recently at Chicago's McCormick Place, where more than 700 exhibitors presented a preview of their newest wares to an audience of about 28,000 supermarket, food company and media representatives.

As for fast food and supermarkets, Tim Hammonds, senior vice president of research and education for FMI, said the notion of eating away from home is being broadened to the notion of not cooking. In that respect, supermarkets have a tremendous growth opportunity and we may be seeing the grocery store taking more and more of carryout food sales from restaurants.

In FMI's "1986 Trends" survey, 43 percent of respondents said they purchase their carryout food from fast-food restaurants, 38 percent said they take out from carryout sections of restaurants, 10 percent carry out food from the supermarket and the remainder of those surveyed either get food from other sources or don't carry out. What's needed to increase the supermarkets' percentage are more suitable products, Hammonds said.

As witness to this market, the convention floor was filled with purveyors of prepared salads, in-store bakery items and deli cases (the new style these days in deli cases is the European case, which can be opened from the front and has greater "visual appeal," said Kevin Falvey of Warren Sherer Co., which sells such products).

In addition to the more appealing deli case, another boost to supermarket carryout sales could come from slow-cooking foods -- like roasts and turkeys -- that are getting faster. Kroger Co. previewed a half dozen or so fully cooked meat products the supermarket chain is selling, including a chicken from Perdue, turkey breasts, roasts, pork loins and ribs. Not only does this new food category cater to busy cooks, but the meat industry gets another crack at increasing declining sales of beef.

The meats are vacuum packed, and can be microwaved or reheated in a conventional oven in about 30 minutes. Many of the products are packed with salt and monosodium glutamate, however, resulting in a product that may be too salty for many tastes. Caramel color is also listed on the ingredient label of several of the products.

Instead of going to your neighborhood gyro parlor, now you can assemble your own with Grecian Delight's or Corfu Gyros' ready-to-eat gyro kits, which come with sliced meat, pita bread and cucumber sauce. And Frieda's Finest, the Los Angeles specialty produce firm, has just introduced fresh and ready-to-eat crepes.

Snack foods are changing shape and size, but not much else. Frito-Lay, which plans to introduce 100 new snack products this year, has recently released Delta Gold Potato Chips, Chilada Flavor Tostitos and Jalapeno and Cheddar Potato Chips. Another snack company was pushing its new Cinnamon Crunchies; Bacon Krisps!, made by a West German company, were touted as containing "pure vegetable shortening" -- in this case "palm oil and/or soybean oil," the palm being a highly saturated vegetable oil.

Surimi -- that imitation crab product made of underutilized fish extruded and topped with red food coloring -- was in abundance at the convention, both in salads and in stick form. Second-generation surimi is taking shape in entrees like seafood wrapped in pasta and topped with cheese.

One purveyor of real crab meat -- Ken Hirtle of Conners Brunswick Inc. -- commented that at the same time that the United States is importing surimi from Japan, we export 50 percent of our real crab meat to the Japanese.

As for the upscale -- or comparatively upscale -- Jell-O is coming out with a mousse dessert, Kraft is coming out with an imported cheese product, the Betty Crocker line now includes a Cake Lover's Collection cake mix that sells for about three times as much as its standard mix, Weight Watchers has a Candle Lite frozen dinner, and every other company seems to have the word "classic" on its label. There are even "gourmet" croutons and gummy bears.

As for products aimed at the nutrition-minded, there were few displays of fresh, unprocessed foods. And the terms "natural" and "lite" seemed to be deemphasized at the show, too.

William Aufricht, marketing coordinator for Arrowhead Mills Inc., said the food industry is "waiting to see which way to turn" now that the craze for health and nutrition has reached a plateau. FMI spokeswoman Karen Brown said nutrition awareness is less trendy now, but that's because nutrition-minded eating habits are more engrained as part of people's everyday lives.

If whole-wheat bread and lowfat cottage cheese are being integrated more in consumers' daily eating regimens, so are rich ice creams. And expect to see lots of new ones this summer.

Since 1985 was the year of the fruit and juice bar, 1986 had to be the year of the DoveBar copycat. And now, the makers of the DoveBar have come out with a new product called Dove Delight, a cookie wafer topped with ice cream, then a fruit pure'e, then a chocolate coating.

Even Popsicles are changing face. In a historic move by the company, the sugary ice pop is moving from two sticks onto one. According to Paul Kadin of the company, the original Popsicle was one stick, but went to two during the Depression, when the notion was to buy one pop for five cents and share it with a friend. The return of the one-stick Popsicle was test-marketed for about three years, said Kadin, to make sure that the public was ready for a change in this American institution.

Wine coolers haven't peaked yet. And what's going on with New Coke these days? It's "certainly not our lead brand," said Mike Wilson of Coca-Cola U.S.A. Bad news, too, for the newer beverage, as McDonald's and Kentucky Fried Chicken both switched to Classic Coke in their stores. Now Coke is test-marketing a plastic can.

Exhibitors used a range of tactics to attract conventioneers to their booths. Marineland Aquarium Products did it with a 20-pound, 100-year-old lobster. "I'll take my coat off and wrestle with him for 50 bucks," quipped one participant as he passed by the enormous creature.

The Frito-Lay company had a money machine, a see-through booth that looked like something out of a game show. Conventioneers entered the booth one at a time, grabbing for what they could, as electric fans circulated $350 in dollar bills in a wild, windy fashion.

A deli company lured passers-by with a 10-foot cowboy, Famous Amos was Famous Amos, and the 25th Elsie the Cow was available for photo opportunities. Various furry creatures roamed the convention floor, as did the Heinz Ketchup robot and the Stroh's Strohbot, which told conventioneers who were drinking free Stroh's beer how to reduce liability costs with the company's alcohol management program.

The men from Scott Paper all wore blue blazers; the women from Turtle Wax wore white shorts. A Playboy bunny representing Warner Communications signed her autograph and racing car driver Ken Schrader signed his next to his Red Baron Frozen Pizza Thunderbird.

And in case conventioneers forgot the name Beatrice, with which the huge corporation has tried so avidly to acquaint the American public, the company had exhibits of its nonfood items adjacent to its multiple food booths of La Choy, Wesson, Mountain High and so on. Did you know? Beatrice also owns Playtex, Round the Clock Pantyhose, Danskin and Samsonite luggage.

Exhibits covering the 750,000 square feet of convention floor space were testament to the diversity of services and support products needed to run a supermarket. Computer technology is coming on strong, for both consumers and supermarket operators. And somebody has to manufacture automatic sliding doors, sneeze guards and checkers' outfits. Then there is the issue of bags -- and there were plenty of them. Now that low-density plastic bags have infiltrated the supermarket, the next hot receptacle is the high-density polyethylene bag, the type that feels like a combination of tissue paper and plastic wrap.

Regular plastic bags take four to five seconds for the checker to adjust onto the rack, said R. Leon Phelps of Sonoco Co., as firm representatives demonstrated how the newer high-density bag can be fitted onto a rack in only one to two seconds.

Over at the Sack Corp. of America, however, Jay Fein and Jonathan Gilman were touting the low-density plastic bag. The high-density bag, they proclaimed, has a tendency to rip and run. Besides, said Fein, it makes a "crinkly sound."