Sore feet and heartburn. Heartburn and sore feet.

That's what lies at the end of the 39 carpeted aisles flanked by booths and exhibits at the Food Marketing Institute convention in Dallas and the annual Restaurant, Hotel-Motel Show sponsored by the National Restaurant Association in Chicago. The booths number more than a thousand. The browsing is measured in miles.

No wonder. Those who want to sell to the people who sell food to the public have large, captive audiences. The Dallas show is for supermarket operators. The one in Chicago is for restaurateurs. At both more equipment and accessories are displayed than food itself, but all the ingredients necessary for a giant national stomachache are there nonetheless.

The Dallas convention came first, early in the month. The supermarket men (very few among the 15,000 executives are women) appear to take the work aspect more seriously than do the restaurateurs. Meetings and work sessions are jammed. There are large displays of greeting cards and magazines, and many of the companies selling deli equipment - deep fat friers, steam table systems and the like - will reappear at the restaurant show, as will the cash register companies.

Several trends were in evidence:

Whatever the energy crunch, highly processed foods are what industry wants to sell your grocer. For example, this from Beehive Machinery, Inc.: "Beehive's 'Extrusion' systems recombine separated fat and lean meat into eye-appealing, mouth-watering steaks that are virtually indistinguishable from the natural cuts. And not just beef steaks, but pork steaks, poultry steaks, bacon-like breakfast strips, from any meat species, any cut, and any size or shape." Other companies are promoting energy-management systems, computer systems, alarm systems.

If the national diet is in transition, it is consumers, not producers, who are sounding the trumpet of change. Baked goods, frozen foods (and frozen baked goods) are everywhere. The bad tooth fairy might have sprinkled the hall with sugar. The program lists 21 companies displaying "snack items." Only eight are listed under the produce category.

This will be the year of the pina colata, or at least so industry hopes. Three or four different booths are offering samples. Coco Lopez, a coconut mix from Puerto Rico, stood out and would reappear at the restaurant show.

Pizza is still big. So are hot dogs and beer. One brand of pizza, Totino, has a "revolutionary crisp crust" that won a patent. Another, Tony's, is the freshest-tasting and has top-quality ingredients. (It is sold in Washington, but not at Safeway, where Celeste reigns supreme."

The lines were long for nationalbrand hot dogs made with traditional ingredients. It was comparatively easy, however, to get samples of chicken or turkey hot dogs. One hot dog came stuffed with cheese. Ugh!

Despite the spate of processers, fresh foods are making some headway. Almonds, strawberries and lettuce (with an olive-oil manufacturer's dressing) were represented. Quality-conscious companies such as Entenmann's (baked goods), Haagen Dazs (ice cream), Usinger's (superb sausage and meat products from Milwaukee) and Manchester Farms (quail and quail eggs from South Carolina) were represented.

Gebhardt, the producer of an excellent chili powder, has introduced a 17-item line of Mexican foods. If one firm was trying to simulate black walnuts and pecans with peanuts (unsuccessfully, to my taste buds), another - Morrison's - has packaged stone-ground mixes from yellow and white corn that make delicious muffins.

The move to providing smaller portions for single or two-person families was reflected by an experimental "tri-pack" of bacon, with the package divided into three separate air-tight containers, and Morton's "Great Little Desserts," small frozen cheesecakes, cream pies and fruit pies that retail for about 89 cents.

At the Chicago restaurant show last week, many of the Dallas participants were again on the scene. There were complaints that too little new and energy-saving equipment was on view. And the number of fast-food restaurant companies seeking new franchises was down sharply from previous years.

But there were still plenty of encouraging innovations for merchants:

One new "fad" that may be developing is sausageburgers. A salesman for the Odom company, which packages both raw and pre-cooked patties, said demand for its product has been growing as beef prices continue to go up while pork prices decline somewhat.

Another may be "oyster chips," a crispy snack item made from "30 percent oysters." A third is the "firedog," a very hot, peppery hotdog manufactured by the Vienna Beef Company. "It'll increase your beverage sales by 70 percent," promised the salesman. A Canadian firm, Applied Hydroponics of Montreal, was pushing "The Herb Market," trays of fresh herbs that grow year - round indoors.

There were odd machines. The Chauguette (an electrically powered wheel with spikes) is intended to penetrate and toast the inside of hot dog rolls. There was a "ketchup saver" that links one bottle to another so that left-over ketchup can be transferred between them. And another company offered lobster-tail cutters in several sizes.

A stroll down a random aisle led past displays for Perrier, Mother's Chessecake led past displays for Perrier, Mother's Cheesecakeressings, Holland House drink mixes, Manchester Farms (the quail people), a display of popcorn cups, Johnson & Wales (the Rhode Island chef-training school), cash registers, cigarette machines, Everclear (a product intended to keep glasses from fogging up), steam tables, Wear-Ever cookware, candy decoration and hanging dried plants.

The people roaming the aisles were, according to one exhibitor, somewhat boisterous, and bowls and blenders were hawked by men who could have been carnival sideshow barkers. There were convection ovens, uniforms, ashtrays, guest checks in a multitude of sizes and designs, chairs, china and lots of bar equipment (but less free alcohol than at the FMI convention). Three dozen schools and "educational services" had booths.

There was Swift's bacon, stored in a vacuum can (300 slices to the can) without refrigeration for an indefinite length of time, that tasted fine. Also making positive impressions on the palate were a trio of authentic, deliciously spicy Mexican-style sauces from La Preferida, several fresh citrus juice displays, delicious waffles made from the F.S. Carlon Company's "malted pancake flour," Tulkoff's Tiger Sauce. Black Diamond cheddar cheeses and some freshly fried potatoes that were doing an excellent selling job for the Idaho potato people.

On the negative side were some portion-controlled veal steaks, watery breaded frozen mushrooms, hopelessly gluey potato pancakes, Wong Wing's line of "real" frozen Chinese food, fried candied yams, peanut-butter pie and most of the frozen baked products.

Two overall impressions remain. First, there were a number of excellent foods being offered to the restaurateurs. The door isn't closed on products that offer freshness or quality, even at higher prices.

Second, though, was a feeling that the consumer-inspired drive for "truth-in-menu" detailed listings is justified and will benefit the conscientious restaurateur.

It seems logical with such skillful imitations available that customers should know whether their "veal birds" were being cut, stuffed and wrapped fresh by a chef or bought frozen and deep fried by a cook. "Steak Tonight," a heavily advertised processed meat product does look like steak. But when you chew it, the texture is that of ground beef. Should the customer pay the price of steak, or of ground beef? Knorr-Swiss presented portions of a light, fluffy mousse that is made with a mix and milk. It comes in four flavors and costs, the salesman said, "approximately 10 cents a serving." And, as mousse maison , probably it will be sold for $3.50 a portion.

The restaurant industry prefers the term "accuracy-in-menu" to "truth-in-menu." Leaders of the industry, including the Restaurant Association of Metropolitan Washington, have supported the concept. But only an estimated 100 restaurateurs at the show attended a briefing on the subject. CAPTION: Illustration, no caption, By Susan Davis for The Washington Post