Grape Juice

Although pressing the juice from grapes involves several steps, the canning process is rather easy. Grapes are one of the higher acid fruits and the hot grape juice only needs to be processed 5 minutes in a boiling water bath when canned in pint or quart jars.

The pronounced flavor of Concord grapes makes their juice desirable for grape jelly as well as for a beverage. The Niagara variety is suitable for making white grape juice.

Select grapes that are plump, well-formed and firmly attached to green, pliable stems. Fully ripe grapes are soft and tender. Avoid grapes showing signs of mold, decay, shriveling, stickiness or dry brittle stems. Unlike some fruits, grapes will not improve or ripen after they have been harvested.

Green grapes are the sweetest and best flavored when they are yellow-green in color, red varieties when the grapes are predominately red, and the blue-black varieties when the berries have a full rich color. The bloom or whitish coating found on grapes prevents moisture loss and decay.

An average of 3-1/2 pounds of grapes will yield a quart of juice. It will take 24 pounds to prepare a canner load of 7 quarts.

Before starting preparation, wash hands for 20 seconds. To prepare the juice, wash the grapes and remove the stems which contain large amounts of tannins that will make the juice bitter. Place grapes in a large stainless steel saucepan and add boiling water to cover the grapes.

Heat and simmer slowly until grape skins are soft — about 30 minutes. Strain through a damp jelly bag or double layers of cheesecloth.

You may have seen little white crystals in the bottom of a jar of grape juice. These are tartrate crystals and are harmless. You can prevent tartrate crystals by allowing the prepared juice to stand 24 to 48 hours in the refrigerator.

Without mixing, pour off the top of the grape juice, being careful not to disturb the crystals in the bottom of the container. Discard the sediment. Straining the juice through a coffee filter yields a clear juice.

Sweeten the juice to taste before the final heating. Sugar is not needed to preserve the grape juice but may be added for flavor. Reheat the strained grape juice until the juice begins to boil before pouring into hot sterilized jars. Leave 1/4-inch headspace.

Process pints or quarts for 5 minutes in a boiling water bath or atmospheric steam canner. Increase process time to 10 minutes for altitudes between 1,001 and 6,000 feet and to 15 minutes at altitudes above 6,000 feet.

Grape juice and apple juice are the only products approved for canning in half-gallon jars. Make sure your canner is tall enough to cover the jars with at least 1-inch of boiling water. Half-gallon jars of grape juice are processed for 10 minutes; make adjustments for higher altitudes.

Note that pint and quart jars need to be sterilized because they are processed less than 10 minutes. To sterilize jars, cover jars with water and boil them for 10 minutes. If you live at an altitude above 1,000 feet, boil the jars an additional minute for each 1,000 feet of additional altitude.

Occasionally grape juice will ferment. This is likely the result of yeasts that were not killed during heating and processing. When grapes are harvested, there are yeasts present; the skin is not removed as in some fruit. The processing of grape juice is only killing organisms in the headspace and providing a firm seal. Heating the juice adequately before pouring it into the jar is essential for destroying microorganisms.

Grape juice can also be frozen. Prepare juice as above. After straining the juice and removing tartrate crystals, pour off the clear juice. Pour juice into freezer containers, leaving adequate head space — 1/2 inch per pint and 1 inch per quart in containers with wide top openings and 1-1/2 inches for pints or quart jars with narrow top openings. The reason for the high headspace in that the liquid will expand when frozen. Seal, label and freeze. If more tartrate crystals form in the frozen juice, remove them by straining the juice after it thaws.

To freeze juice for jelly, add 1 cup water per gallon of washed, stemmed, and crushed grapes. Simmer for 10 minutes. The shorter simmering time is to preserve the natural pectin in the grapes. Strain as above. Do not add sugar to juice being canned or frozen for jelly. Pour prepared juice into containers, leaving 1/2- to 1-inch headspace.

If you have food preservation questions, a home economist is available to answer questions on Wednesdays 10 a.m.-2 p.m. Call 717-394-6851 or write Penn State Extension, Lancaster County, 1383 Arcadia Road, Room 140, Lancaster PA, 17601.

The Well Preserved news column is prepared by Penn State Extension.

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