Putting Food By - Janet Greene [17]
It is used most often with apples, apricots, nectarines, peaches, and pears; in a strong solution, it is a coating for cut fruit waiting to be processed or packed.
Generally speaking, the ascorbic-acid solution is strongest for drying fruits (Chapter 21), less for freezing them (Chapter 14), and least strong when they’re canned (Chapter 7).
The crystals also may be added to the canning syrup or to the Wet packs of frozen fruit.
Citric acid is known to kosher cooks as “sour salt” and to Greek cooks as “lemon salt”. It is sold in specialty or ethnic food stores, in the gourmet sections of some metropolitan supermarkets, in drugstores, and on the internet. Except at drugstores, where it is often finely granulated, it comes as coarse crystals. The large crystals are easily pulverized between the nested bowls of two spoons or with a mortar and pestle. (See also Acids to Add for Safety later in this chapter.)
Volume for volume, it’s about one-third as effective as ascorbic acid for controlling oxidation (darkening), and therefore enough to achieve the same result could mask delicate flavors of some fruits.
Lemon juice contains both ascorbic and citric acids. Average acid-strength of fresh lemons is about 5 percent (also the labeled strength of reconstituted bottled lemon juice; some strains of California lemons are less strongly acidic, however).
Being in solution naturally, it’s about one-sixth as effective volume for volume as ascorbic acid for preventing darkening. Even more of a flavor-masker than citric acid, it also adds a distinctive lemony taste to the food. It is used primarily to augment a food’s natural acidity.
Mild acid-brine holding bath is one of the choices for treating apples particularly, but also apricots, nectarines, peaches, and pears while they wait to be packed in containers and processed. It’s a solution in the proportions of 2 tablespoons salt and 2 tablespoons white (distilled) vinegar to each 1 gallon of water. Cut fruit is held for no longer than 20 minutes in the acid-brine (which does leach nutrients), then is well rinsed (to remove salt taste), drained, and packed.
A similar treatment before freezing these fruits, particularly apples, omits the vinegar. We recommend against using any such holding bath before drying because it adds some liquid to fruit you’re trying to take the moisture out of.
Never use the regular cider vinegar or a wine vinegar. Either could add its own color and, perhaps, sediment to the fruit.
Steam-blanching is sometimes used before freezing fruits (especially apples) likely to darken when cut, and always before drying (even though sulfuring is recommended standard treatment in addition to blanching for fruit that is to be open-air/sun dried). Blanch in a single layer held in strong steam over briskly boiling water, 3 to 5 minutes depending on the size of pieces. (See Chapters 14 and 21.)
Microwave-oven blanching. Each make or model comes with particular instructions for its use, so do read the directions that came with your oven. A rule of thumb would be, however: (1) of course use only an appropriate vessel to hold the food in the oven; (2) blanch only in 1-pound batches, with very little water; (3) rearrange the food once during the blanching process; and (4) depending on the density of the food’s tissues, blanch for 2½ to 6 minutes.
If the food is to be frozen, dunk it immediately in ice water to stop the cooking action and to chill it; pat it dry; package and freeze.
Syrup-blanching is again a pre-drying treatment to hold color, but the syrup is so heavy—1 cup sugar or equivalent natural substitute to each 1 cup water—and the fruit is in it so long (about 30 minutes all told) that you end up with a crystallized (or “candied”) confection.