The Agriculture Department is making a major change in current law: for the first time in 31 years, it is revising its standards for grading fruit jelly.

The rewritten standards -- adopted, the department noted, at the request of the Technical Committee of the International Jelly and Preserves Association -- were thickly spread across four pages of the Federal Register Aug. 3.

Consumers may not even notice the new rules, but to jelly manufacturers, they are -- well -- berry, berry important.

The government for years has had a system for grading what are called standardized fruit jellies. There are 28 of these, ranging from the familiar -- strawberry, grape and the like -- to such exotic varieties as dewberry and prickly pear.

But, as the department explained in the Register, "In recent years there has been a significant change in consumer preferences. Today, there are many kinds and types of jellies marketed that were strictly 'home recipe' items 20 years ago."

To accommodate these, the department is adding two jelly categories: "Non-standardized fruit" and "non-standardized non-fruit."

The first is for fruits even rarer than dewberries. The second, the spokeswoman for the jelly and preserves association says, is to cover such flavors, if that is the right word, as cactus, corncob and green pepper.

Ever vigilant in protecting buyers of food, the government maintains standards of cleanliness and purity. It also maintains some fairly strict truth-in-labeling rules.

These latter fall into two categories. One is supervised by the Food and Drug Administration and governs "standards of identity," or what ingredients are allowed: how much grape and how little sugar a jelly must have before it can legally be called grape jelly.

The second set is the Department of Agriculture's grading system for quality. Unlike those of identity, these standards are voluntary. They were originally set up around 1917 to protect distant trandesmen -- to make sure that if you bought Grade A jelly sight unseen it would be about what you expected, and not some lesser product. Of course, Grade A food usually costs a bit more.

Manufacturers pay USDA inspectors to check their wares and grade them, A, B, or "substandard." A scorecard for grading jelly for color, flavor and consistency is supplied in the Federal Register. Standards for giving points in the three areas are spelled out to a "t," and the language is often lyrical.

For instance, for a high score of 20 points, jelly under inspection must have a "bright, typical color," meaning that "the color is characteristic of the juice ingredients and that the jelly has a sparkling luster or may be not more than slightly cloudy, and is fee from any dullness of color."

For high points in consistency, jelly must have a "tender to slightly firm texture and retain a compact shape without excessive syneriesis ['weeping'].

The law makes short shrift of jelly lacking luster or the dignity not to "weep". Such jelly, along with that having a bitter or "caramelized" flavor or cloudy appearnace, it warns, will rank as "substandard."

These issues of consistency, color and flavor are a little difficult to determine in the case of non-standardized non-fruits. For these, a special phrase: "The finished product shall . . . have organoleptic properties typical of the name of the product."

That means that only if it looks like a duck, quacks like a duck and walks like a duck, can you call it duck jelly.