Most of the 10 tasters liked the flavor of the chocolate milk--at least slightly. But they turned up their noses at the other flavored milks, likening one to "liquid bubble gum" and another to "medicine." Regular whole milk got the lowest marks of all, with one taster dismissing it as "undiluted paste."

These were the results of an informal taste test last week of UHT milk--milk that has been processed at a ultra-high temperature of 280 degrees and packaged in five-layer containers, consisting of three layers of plastic, one of aluminum and one of paper.

UHT milk has been available in Europe for years but is just now being introduced in Washington-area supermarkets under the names Farmbest and Sip Ups.

Because of the special processing and packaging, UHT milk will keep unopened on your kitchen shelf for up to three months. Once opened, it will keep in the refrigerator for 15 to 21 days.

When it comes time to drink the shelf milk, you chill it just as you'd chill beer or soda. Then you can toss the packages into a cooler for trips in the car, picnics in the park, even children's lunches--all without fear of spoilage. You can keep it in the kitchen as just another staple so that you never run out of a supply of fresh milk for cooking or drinking.

That convenience is the good news about shelf milk, which is processed by Dairymen Inc., a dairy cooperative that processes the milk at a special plant in Savannah, Ga., and markets it along the East Coast.

The bad news is that UHT milk costs more than fresh milk, typically contains more calories than fresh milk and may not taste as good.

In the Post taste test, 10 reporters and editors were invited to try unlabeled cups containing samples of regular fresh milk and UHT milk. Both kinds of milk were chilled in advance. The first half of the test was to see if they could distinguish between the two types.

In comparing regular whole fresh milk with regular whole UHT milk, seven of the 10 tasters were able to pick out the one that was different. Three other tasters could not distinguish the difference.

After tasting the low-fat milk and the chocolate milk, six people were able to tell the milk sample that was different; four were not.

In the second part of the test, participants were asked to sip seven types of UHT milk and rate them on a scale of 1 to 7. A score of 1 represented "disliked very much," a score of 2 meant "disliked moderately," a score of 3 meant "disliked slightly," a score of 4 meant "neither liked or disliked," a score of 5 meant "liked slightly," a score of 6 meant "liked moderately" and a score of 7 meant "liked very much."

Scores for each type of milk then were added up and divided by 10 to obtain a group rating. Here are the results:

* Chocolate scored 5.1, meaning the group liked it slightly.

* Vanilla scored 3.4, disliked slightly.

* Low-fat scored 3.3, disliked slightly.

* Fruit punch scored 2.6, disliked slightly.

* Banana scored 2.2, disliked moderately.

* Regular and strawberry scored 2.0, disliked moderately.

Individual opinions of the products varied widely, however. Low-fat milk was described by one taster as "fine" and by another taster as "normal." But a third described it as "watery."

Several of the flavored milks were characterized as too sweet while the regular whole milk was said to have a boiled taste.

The chocolate was rated as okay to satisfactory. The bad news about the chocolate, however, is that it has more than 180 calories per one cup serving--30 more than fresh chocolate milk.

Only the regular whole UHT milk has the same calorie count as its fresh milk counterpart, 150 per cup.