When Brussels spouts rules such as on fizzy water, Europe winces

In the future, the millions of Europeans who drink oceans of mineral water each year will have a better idea of the quality of the product they are consuming.

In the latest of a lengthening list of food and drink regulations, the European Commission in Brussels has laid down descriptive guidelines for the huge variety of mineral waters available.

Throughout the 10 member states of the European Community (EC), water carrying the appellation ''mineral'' will have to include a detailed list of the substances it contains. And the purchaser must be told how the bubbles got into the bottle.

If the bubbles were in the water as it came out of the well, the bottle will say ''naturally carbonated natural mineral water.'' If carbon dioxide was added later by an industrial process, the label will say ''carbonated natural mineral water.''

The thinking behind the water policy has already been applied to a wide variety of foods, not always to the unmitigated delight of the European consuming public.

One EC regulation that has won almost universal approval requires restaurants to post a bill of fare outside the establishment, stating the exact price of the dishes that may be purchased inside, including value-added tax (15 percent).

This requirement has made it possible for diners to work out in advance what a meal will cost, rather than receive a nasty shock after dessert.

Other rules have not been so popular, notably in Britain. A few years ago the bureaucrats of Brussels attempted to compile a list of ''allowable'' varieties of apples.

The list omitted some of the most famous ancient English varieties, and apple farmers here were up in arms. They accused the perfidious French of inspiring Brussels to drown Bramleys and Cox Orange Pippins in a flood of Gallic Golden Delicious.

Later, the bureaucrats turned their attention to the green pea, declaring that to pass as Grade 1, a pod had to contain five peas. English growers exploded, arguing that some of their best crops contained pods with six or even seven peas.

Similar sentiments were expressed in Wales when the European Commission offered a judgment on cauliflowers. No cauliflower should be sold, it asserted, unless it had at least two leaves attached.

By no means are all of Europe's regulations seen as niggling. Brussels laid down grading guidelines for hens' eggs, insisting that the size of eggs for sale had to be inscribed on the container.

Nor have the Eurocrats limited their regulations to food. All clothing sold in EC countries must give details of the fabric or fabric mix. Laundry and ironing instructions appear on the label.

But it is in food that some of the most sensitive British nerves have been touched.

Ice cream manufacturers were aghast when Brussels told them their product must indeed contain cream. A lot of the so-called ice cream sold in Britain is made from vegetable oil.

But it is vegetable growers who win the prize for British ingenuity in the face of Eurocratic zeal.

When Brussels took certain varieties of vegetables off the list of approved seeds, home growers retaliated by establishing seed libraries.

Some ancient types of parsnips, pumpkins, and the rest may no longer be sold by seed shops. But they can be borrowed from a seed library.

If you want a rare but proscribed variety of runner bean, you can write to a library in Essex. It will lend you the seeds. The following season the borrower sends back seeds from his own crop.

Like the vegetables, this English dodge is thriving.