Putting Food By - Janet Greene [19]
White (distilled) vinegar may be used too, but it might contribute a slight flavor of its own.
Ascorbic acid can be used for freezing fatty fish: a 20-second dip in a cold solution of 2 teaspoons crystalline ascorbic acid dissolved in 1 quart of water will lessen the chance of rancidity during freezer storage. The fish to be treated include mackerel, pink and chum salmon, lake trout, tuna, and eel, plus all fish roe.
Acids to Add for Safety
Two acids—citric acid in dry form or in lemon juice, and acetic acid in vinegar—are added to foods in this book for reasons that have little to do with the cosmetic purpose of helping to control oxidation or color changes in put-by food (see Anti-discoloration Treatments, above).
Adding Acids to Preserves and Pickles
We add acid to enhance flavor, making it brighter or more tangy, in condiments like ketchup or chili sauce or chutney. We add it to help create the balance that makes a gel in combination with pectin and sugar, in cooked jellies and jams. And we add it much more lavishly to aid preservation of a number of pickles served as garnishes. How much of which particular acid is added to all these foods is given in the specific instructions in Chapters 18 and 19.
Adding Acids to Natural Foods
The relationship between a food’s natural acidity (pH rating) and its ability to provide hospitable growing conditions for spoilage micro-organisms is discussed at some length in the first part of Chapter 2. In Chapters 7 and 9, small amounts of acid are added for canning specific foods: figs, berry juices, the nectars and purées of apricots, peaches, and pears; sweet green bell peppers and pimientos; and in canning tomatoes (Chapter 8).
Acid is added only to the foods cited immediately above before canning them by the method specified and for the specified processing time. The added acid does not allow any short cut for any step in safe canning procedure, and it does not permit any fiddling with canning methods.
Citric acid. Pure crystalline citric acid, USP (meaning “United States Pharmacopoeia” and therefore of uniform stability and quality), is the acid added in canning tomatoes when bottled lemon juice is not used. If you buy it as “sour salt” or “lemon salt,” that is, as coarse crystals, crush it to the consistency of finely granulated sugar (as described on page 36) before measuring. It is not expensive—especially when you consider that 4 ounces will do about 45 quarts, or slightly more than 90 pints of tomatoes.
Citric acid is preferred for increasing acid-strength of foods because it does not contribute flavor of its own to food (unlike lemon juice and vinegars, which can alter flavor if used in large enough amounts).
Fine citric acid may be substituted for a 5-percent acid solution (the average for store-bought vinegar or for the juice of most lemons) whenever the called-for measurements of the solutions are by the spoonful, in this general proportion: ¼ teaspoon citric-acid powder = a generous 1 tablespoon of 5-percent lemon juice/vinegar; ½ teaspoon citric-acid powder = a generous 2 tablespoons of the vinegar or lemon juice. (The equivalents actually are ¼ = 4 teaspoons, and ½ = 8 teaspoons, but 1 and 2 tablespoons are easier measurements to make in the usual household’s kitchen.)
To reverse the coin and make a 5-percent solution of citric acid, use the rule of thumb for making salt brines: dissolve 1 part fine citric acid in 19 parts of boiled (and cooled) water. Translated into measurements used in the average kitchen, this means dissolving 2 tablespoons fine citric acid in 1 pint (2 cups) of boiled water; or, if you want to be metric, dissolving 30 mL of fine citric acid crystals in ½ liter (500 mL) of boiled water. Either translation will produce a solution around 6 percent instead of 5—but the result will serve the purpose we’re after.
Lemon juice. This is recommended over the other acids for use in canning fruit juice in