Half-gallon canning jars are available from at least one canning jar manufacturer. That manufacturer indicates that half-gallon jars should only be used for highly acidic foods in a boiling water canner. Their recommended choices are grape juice and apple juice.
The USDA, Clemson Extension and the University of Georgia’s National Center for Home Food Preservation recommend process times only for very acidic fruit juices in half-gallon jars (and for only juice, not fruit). These process times should not be used for tomato juice or other juices.
No other research-tested processes for half-gallon jars exist. Boiling water processes published for foods canned in pints and/or quarts cannot be extended to a larger jar by any formula. There are historical recommendations for canning foods in half-gallon jars; however, they are not currently accepted or endorsed by the USDA, by the Cooperative Extension System or by home canning jar manufacturers in the USA. Recommended canning processes for apple juice and grape juice follow.
Quality: Good quality apple juice is made from a blend of varieties. For best results, buy fresh juice from a local cider maker within 24 hours after it has been pressed.
Procedure: Refrigerate juice for 24 to 48 hours. Carefully pour off clear liquid without mixing; discard sediment. Strain clear liquid through a paper coffee filter or multiple layers of damp cheesecloth.
Heat juice quickly, stirring occasionally, until it begins to boil. Fill immediately into sterile pint or quart jars or fill into clean half-gallon jars. Leave ¼-inch headspace. Pre-sterilize pints or quarts by boiling clean jars covered with water for 10 minutes (at altitudes of less than 1,000 ft).
Adjust lids to fingertip tight and process according to recommendations below.
Quantity: An average of 24½ pounds of grapes is needed per canner load of 7 quarts; an average of 16 pounds per canner load of 9 pints. A bushel weighs 48 pounds and yields 10 to 12 quarts of juice – averaging 4 to 5 pounds per quart.
Quality: Select sweet, well-colored, firm, mature fruit of ideal quality for eating fresh or cooking.
Procedure: Wash and stem grapes. Place grapes in saucepan and add boiling water to cover grapes. Heat and simmer slowly until skin is soft. Strain through a damp jelly bag or multiple layers of cheesecloth. Refrigerate juice for 24 to 48 hours. Without mixing, carefully pour off clear liquid and save; discard sediment. If desired, strain through a paper coffee filter for a clearer juice. Add juice to saucepan and sweeten to taste. Heat and stir until sugar is dissolved. Continue heating with occasional stirring until juice begins to boil. Fill into jars immediately, leaving ¼-inch headspace. Pre-sterilize pints or quarts by boiling clean jars covered with water for 10 minutes (at altitudes of less than 1,000 ft).
Adjust lids to fingertip tight and process according to the recommendations below.
Hot-packed pints or quarts should be processed in a boiling-water canner for 5 minutes at altitudes of 0 to 1,000 feet (or for 10 minutes at altitudes of 1,001 to 6,000 feet).
Hot-packed half-gallons should be processed in a boiling-water canner for 10 minutes at altitudes of 0 to 1,000 feet (or for 15 minutes at altitudes of 1,001 to 6,000 feet).
Ask first-time canners to read HGIC 3040 Canning Foods at Home before beginning to can juice.
"Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA, revised 2009.
How Do I …. Selecting, Preparing and Canning Fruit - Apple Juice. University of Georgia, National Center for Home Food Preservation. http://nchfp.uga.edu/how/can_02/apple_juice.html
How Do I …. Selecting, Preparing and Canning Fruit - Grape Juice. University of Georgia, National Center for Home Food Preservation. http://nchfp.uga.edu/how/can_02/grape_juice.html