Michigan State University Extension
Preserving Food Safely - 01600943
* While preparing a canner load of jars, keep peeled, halved, quartered, sliced or diced apples, apri- cots, nectarines, peaches and pears in a solution of 3 grams (3000 milligrams) ascorbic acid to 1 gallon of cold water. This procedure is also useful in maintaining the natural color of mushrooms and potatoes, and for preventing stem-end discoloration in cherries and grapes. You can get ascorbic acid in several forms:
Pure Powdered Form--seasonally available among canners' supplies in supermarkets. One level teaspoon of pure powder weighs about 3 grams. Use 1 teaspoon per gallon of water as a treatment solution.
Vitamin C Tablets--economical and available year-round in many stores. Buy 500-milligram tablets; crush and dissolve six tablets per gallon of water as a treatment solution.
Commercially Prepared Mixes of Ascorbic and Citric Acid--seasonally available among canners' supplies in supermarkets. Sometimes citric acid powder is sold in supermarkets, but it is less effective in controlling discoloration. If you choose to use these products, follow the manufacturer's directions.
* Fill hot foods into jars and adjust headspace as specified in recipes. * Tighten screw bands securely, but if you are especially strong, not as tightly as possible. * Process and cool jars. * Store the jars in a relatively cool, dark, dry place, preferably between 50 and 70 degrees Fahrenheit. * Can no more food than you will use within a year.