When to harvest grapes depends on how they will be used. Grapes for wine making need to be picked when the pH levels reach a certain point. Grapes that are to be eaten fresh are picked when they look good and taste sweet. In my area of the northwest, grapes for jellies and juices are typically picked after the first frost when the sugar content is at its peak.
The problem with waiting until first frost to harvest grapes is that a home canner is faced with the enormous task of putting up 100 pounds or so of fruit in less than a couple of days. One easier and certainly less complicated way of preserving those grapes is to freeze them until you can get around to turning them into juices and jams.
There’s several ways in which you can freeze grapes. Each of these methods calls for ripened grapes and freezer containers. Because the fruit will be packed in liquid, it’s recommend to use either freezer safe canning jars or rigid plastic freezer containers. Both of these can be purchased in the food storage section of any grocery store.
How to freeze grapes
To prepare grapes for freezing, they should first be checked for signs of mildew or damage. Discard the damaged grapes, and select only those grapes that are ripe and firm. Wash in a colander, drain, remove stems and freeze using one of these two methods:
Puree: The easiest way I’ve found to freeze grapes for future use is to puree them. The cleaned fruit is thrown into a large stock kettle with just enough water to prevent sticking, brought to a boil and then carefully mashed with a potato masher. After the mixture has cooled, the puree is strained through a colander to remove pits and peels. The prepared puree can then be packed into a freezer container allowing for about an inch of head space. (Head space is the “air” space left in the container which gives the contents room for expansion as they freeze.) Be sure to seal and label the contents so you’ll know what you’ve packaged.
When it comes time to make up the your homemade grape jellies or juice, the thawed grapes can be strained through a jelly bag or clean pillowcase to remove sediment. The clear juice will then be ready for processing.
Packed in syrup: Certain grapes, such as Thompson seedless are fantastic to eat right off the vine. For a bumper crop of Thompsons or other varieties of “eating” grapes, the extras can be frozen in syrup and enjoyed later as chilled compote.
Syrup helps preserve the quality of the grapes, and adds extra sweetness. To make freezer syrup, combine 3-1/4 cup of sugar with 5 cups of water which will yield about 7 cups of medium syrup.
Pack the clean grapes into the freezer container, and pour the syrup over the grapes to cover, leaving one inch of head space. Snap on the lid, label, and freeze. To enjoy the grapes at a future meal, the container should be allowed to partially thaw, and the grapes served up semi frozen for a grape compote dessert that tastes fantastic.
Sources:
Unversity of Idaho Extension Office
Ball Blue Book of Preserving, published 2008 by Jarden home brands
