IN EFFORTS to tempt consumers with low prices, some area supermarkets have reached into their bags of tricks and pulled out one called "ungraded meat."

Its price-per-pound is attractive. But consumers may suspect sleight-of-hand when faced with ungraded products. They are accustomed to buying meat that's labeled "USDA Choice." If they buy the ungraded, they wonder, what are they actually getting?

They are getting beef that is safe to eat, that is clean and wholesome. They are not getting a guarantee of "palatability."

"Grading and inspection are not the same," says Tom McDermott of the National Live Stock and Meat Board. "I can't emphasize that strongly enough. Grading is a measurement of eating quality in terms of juiciness and tenderness."

All beef must be inspected, and there are government inspectors stationed at packing houses around the country to make sure the meat is suitable for eating.

Grading is a little different. Meat packers may opt for having their meat graded, but they must pay separately for the service, which guarantees the consumer is getting a piece of meat with a certain "palatability."

Meat grades are determined by how old the carcass is (judged on bone calcification) and how well marbled it is.

Younger animals yield a more tender product and will help bring the grade higher. In addition, if needle-thin strands of fat are laced throughout the meat (marbling), graders assume the meat will be tender and flavorful and therefore give it a higher grade.

Choice beef, second next to prime, is the grade usually sold in grocery stores. Around Washington, however, supermarkets are learning there's a profit to be made in ungraded meat.

Grading costs the meat packers, who must hire government graders to come to the plant and judge the meat. The packers can save a little money by refusing the service, and these savings can, in theory, be passed on to the consumer.

Second, the cattlemen can save money when raising their beef animals. To qualify for the choice grade, animals must have muscle generously riddled with thin strands of fat. Cattle must be corn fed to develop this desirable type of muscle, and that's an expensive process. Packers who decide to sell ungraded carcasses pay cheaper prices to buy cattle that have not spent a long time on special feed. Again, savings could, ostensibly, be passed along to the consumer.

That's good and bad news. Cheaper beef is welcome. But this meat could cover a wide spectrum of palatability. It could be the very leanest of the "good" grade (the grade below choice) or the very top choice (which is almost prime). With ungraded meat, there's no guarantee.

And it's impossible, says Tom McDermott, for anyone to determine beef grade by looking at the beef at the meat counter. "Even a PhD food scientist couldn't do that. You can't tell the age without seeing the carcass," although marbling is clear enough.

So the consumer takes a chance when buying the beef, even though he can see the marbling. Supermarkets selling ungraded beef in this area point to their "house policies" of a full guarantee if the shopper is unsatisfied. But ungraded meat can be expected to be leaner and tougher, with a slight difference in flavor (an abundance of connective tissue may add flavor in the absence of fat).

Palatability differences between choice and ungraded meat will be most noticeable in steaks and loin cuts. People pay a lot of money for steaks because they are tender, juicy and flavorful. Scrimping on the grade would be more obvious in these cuts, which usually are served unembellished. In that instance, says McDermott, the shopper should stick with USDA choice meat (or prime, if you can get it).

But steak is a rare visitor to many dinner tables; what of other cuts?

For less tender cuts of beef -- the chuck or the round, for example -- McDermott insists that the difference in choice and ungraded would be negligible. These tougher cuts are braised, often with flavorful liquid (broth or wine), vegetables and herbs. The long cooking tenderizes the meat and causes the tough connective tissue to disintegrate into a tasty broth.

In fact, testing by The Washington Post staff found choice meat (a top round steak) was far less tender and juicy than a sample of ungraded. It is a game of chance in a way, but, so far, consumers seem willing to play. A spokesman for Safeway, which carries only ungraded meat in most of its stores, says meat sales are up. At Giant, which sells both choice and ungraded, the latter accounts for about half the beef sales.

When a supermarket sells a USDA graded product, it is, without noticeable exception, labeled as such, both in advertisements and at the meat counter. If it isn't graded, there might be a Giant "lean" label or a Safeway "quality" label.