Pretreating Vegetables

Susan Reynolds, M.S.

Blanching is a necessary step in preparing vegetables for drying. By definition, blanching is the process of heating vegetables to a temperature high enough to destroy enzymes present in the tissue. It stops the enzyme action which causes loss of color and flavor during drying and storage. It also sets the color and shortens the drying and rehydration time by relaxing the tissue walls so moisture can escape or re-enter more rapidly In water blanching, the vegetables are submerged in boiling water. In steam blanching, the vegetables are suspended above the boiling water and heated only by the steam. Water blanching usually results in a greater loss of nutrients, but it takes less time than steam blanching. (See Table 1 on "Drying Vegetables at Home".)

Not all vegetables require blanching. Onions, green peppers and mushrooms can be dried without blanching.

Water Blanching

Fill a large pot two-thirds full of water, cover and bring to a rolling boil. Place the vegetables in a wire basket or a colander and submerge them in the water. Cover and blanch according to directions for each vegetable (see Table 1 on "Drying Vegetables at Home). If it takes longer than one minute for the water to come back to boiling, too many vegetables were added. Reduce the amount in the next batch.

Steam Blanching

Use a deep pot with a close-fitting lid and a wire basket, colander or sieve placed so the steam will circulate freely around the vegetables. Add water to the pot and bring to a rolling boil. Loosely place the vegetables in the basket no more than 2 inches deep. Place the basket of vegetables in the pot. Make sure the water does not come in contact with the vegetables. Cover and steam according to the directions for each vegetable (see Table 1 on "Drying Vegetables at Home).
Table 1. Drying Vegetables At Home
Vegetable Preparation Blanching Time Drying Time Dehydrator(*)(hours)
Steam (minutes) Water (minutes)
Artichokes, globe Cut hearts into 1/8-inch strips. Heat in boiling solution of ¾ cups water and 1 tablespoon lemon juice. 6-8 4-6
Asparagus Wash thoroughly. Cut large tips in half. 4-5 3«-4« 4-6
Beans, green Wash thoroughly. Cut in short pieces or lengthwise. (May freeze for 30 to 40 minutes after blanching for better texture.) 2-2½ 2 8-14
Beets Cook as usual. Cool; peel. Cut into shoestring strips 1/8-inch thick. Already cooked no further blanching required. 10-12
Broccoli Trim, cut as for serving. Wash thoroughly. Quarter stalks lengthwise. 3-3½ 2 12-15
Brussels sprouts Cut in half lengthwise through stem. 6-7 4½-5½ 12-18
Cabbage Remove outer leaves; quarter and core. Cut into strips 1/8-inch thick. 2½-3(**) 1½-2 10-12
Carrots Use only crisp, tender carrots. Wash thoroughly. Cut off roots and tops; preferably peel, cut in slices or strips 1/8-inch thick. 3-3½ 3½ 110-12
Cauliflower Prepare as for serving. 4-5 3-4 12-15
Celery Trim stalks. Wash stalks and leaves thoroughly. Slice stalks. 2 2 10-16
Corn, cut Select tender, mature sweet corn. Husk and trim. Cut the kernels from the cob after blanching. 5-6 4-5 6-10
Eggplant Use the directions for summer squash. 3½ 3 12-14
Garlic (chard, kale, turnips, spinach) Peel and finely chop garlic bulbs. No other pretreatment is needed. Odor is pungent. No blanching needed. 6-8
Greens (chard, kale, turnips, spinach) Use only young tender leaves. Wash and trim very thoroughly. 2-2½ 1½ 8-10
Horseradish Wash; remove small rootlets and stubs. Peel or scrape roots. Grate. None 4-10
Mushrooms (WARNING, see footnote(***)) Scrub thoroughly. Discard any tough, woody stalks. Cut tender stalks into short sections. Do not peel small mushrooms. Peel large mushrooms, slice. None 8-10
Okra Wash, trim, slice crosswise in 1/8 to ¼-inch disks. None 8-10
Onions Wash, remove outer "paper shell." Remove tops and root ends, slice 1/8-to ¼-inch thick. None 3-9
Parsley Wash thoroughly. Separate cluster. Discard long or tough stems. None 1-2
Peas, green Shell. 3 2 8-10
Peppers and Pimientos Wash, stem, core. Remove "partitions." Cut into disks about 3/8- by 3/8-inch. None 8-12
Potatoes Wash, peel. Cut into shoestring strips ¼-inch thick, or cut in slices 1/8-inch thick. 6-8 5-6 8-12
Pumpkin and hubbard squash Cut or break into pieces. Remove seeds and cavity pulp. Cut into 1-inch strips. Peel rind. Cut strips crosswise into pieces about 1/8-inch thick. 2½-3 1 10-16
Squash, summer Wash, trim, cut into ¼-inch slices. 2½-3 1½ 10-12
Tomatoes, for stewing Steam or dip in boiling water to loosen skins. Chill in cold water. Peel. Cut into sections about ¾-inch wide, or slice. Cut small pear or plum tomatoes in half. 3 1 10-18
(*) Drying times in a conventional oven could be up to twice as long, depending on air circulation.
(**) Steam until wilted.
(***) WARNING: The toxins of poisonous varieties of mushrooms are not destroyed by drying or by cooking. Only an expert can differentiate between poisonous and edible varieties.

This document was extracted from Bulletin 989, "So Easy to Preserve," produced by the Cooperative Extension Service, the University of Georgia, College of Agricultural and Environmental Sciences. Third Edition published in 1993.

Susan Reynolds, M.S., former Extension Foods Specialist, University of Georgia; revised by Judy Harrison, Ph.D., Extension Food Specialist, Cooperative Extension Service, University of Georgia, College of Agricultural and Environmental Sciences, Athens. For more information contact your local Extension Service agent.

(This document is also available as an Adobe Acrobat file)