Preserving Nutrient Value of Vegetables

New Zealand Journal of Agriculture, Volume 85, Issue 3, 15 September 1952, Page 263

Preserving Nutrient Value of Vegetables

PROBABLY the greatest amount of unnecessary waste in the preparation of food takes place in the cooking of vegetables. As much of this waste is invisible, it is hard to realise that vegetables prepared correctly may contain so many more nutrients than those subjected to careless methods. Many people who tend their gardens and grow their vegetables with loving care thoughtlessly pour many of the nutrients down the dram. For those who buy their vegetables from shop or market it is even more important to preserve nutrient qualities of vegetables during cooking, because bought green vegetables particularly have already lost some value during the period between gathering and preparation. In this article Eleanor Couston, Field Officer in Rural Sociology, Department of Agriculture, Timaru, gives simple instructions for conserving the maximum value of vegetables.

THE home gardener has the satisfaction of producing food of high quality and is independent of the vagaries of the market. However, to derive the full benefit of homeproduced food, the housewife must follow the rules or much of the labour expended will be in vain. The greatest value of vegetables lies in their mineral and vitamin content, but they also provide cellulose or roughage and variable amounts of protein and carbohydrate. As many of the nutrients are soluble in water or destructible by heat or on exposure to air, the best methods of preparation and cookery should be known and followed. To provide a daily menu containing adequate quantities of the most important nutrients vegetables should be chosen to include the following:— Generous serving of potato; One or more servings of green vegetables, cauliflower, or swede;

One other vegetable. The most important feature in the selection of vegetables is their freshness. This applies particularly to green vegetables; which, from the time of gathering, gradually lose their vitamin C. Dr. Faith Fenton, Professor of Food and Nutrition, Cornell University, has stated, “Vitamin C may be taken as the criterion of quality and nutritive value of vegetables. If it is retained, so also are other attributes. . . . The challenge is to see that the maximum amount of vitamin C is retained in vegetables up to the time they are actually consumed.”

Maturity, Price, and Cleanliness Other points to look for are maturity, price, and cleanliness. Although it is uneconomical to gather vegetables before they have reached maturity, there is a tendency to err in the other direction and to allow them to remain ungathered until they have become woody and tough. The French are renowned for their “petit pois”, young green peas which melt in the mouth; although use of peas at this stage is extravagant, they are preferable to the overmatured products sometimes served in this country. Price also is important, and best use of vegetables in season and at reasonable cost should be made. Bought vegetables should be reasonably free from soil and sand.

Storage The experienced home gardener will know when to gather root vegetables for storage; that is, at the stage where they are still tender but mature enough to be full flavoured and ripe. Root vegetables for current use should be kept in well-ventilated racks in a

cool, dry place, and those for winter use in layers of sand or dry soil. Onions, marrows, and pumpkins require circulation of air for good keeping. Green vegetables should never be stored unless they are quick frozen. Maximum value is obtained from green vegetables when the

least possible time elapses between gathering and consuming. If a short time lag is unavoidable, less loss will occur if the vegetables are kept in a covered dish in a refrigerator or, failing this, in a cool, dry place. For those fortunate < enough to possess a home freezer the storing of surplus

green vegetables is simple, and provided the process is'carried out in the approved way, there will be little loss of nutrients or flavour. Vegetables which are not cooked before serving are not suitable for deep freezing. Preparation Alil , ~ , „ ■ Although different methods of pre?Stables^ e themSe fundamental principles which should be observed. The best method of preserving the nutritive value of such vegetables as potatoes,. kumaras, and beetroot is to cook them with the skin on. When it is necessary to peel vegetables care must be taken to pare them as thinly as possible. This can be accomplished in most cases much more satisfactorily with a special potato peeler than with an ordinary knife. With a little practies the housewife will soon acquire skill in using this utensil ana save nSatirn b °A Reeled in 20 mtaSesl an example ol what aS be done Vegetables require thorough washing, but they should not be soaked. A small brush kept for the purpose is invaluable for cleaning such vegetables. as young carrots, potatoes, and celery, The soaking of vegetables, especially when they are cut in small portions, may lead to considerable losses in nutritive value. Less loss will occur if the vegetable is covered with a damp cloth or wrapped in aluminium foil and placed in the refrigerator. As vegetables contain a substance which on exposure to air will quickly cause destruction of vitamin C, they should be cut or sliced just before they are cooked. Cutting with a sharp knife will cause little loss, but grating, which exposes a large surface to the air, may lead to considerable loss. Less loss

occurs when vegetables such as cabbage are shredded with a sharp knife before cooking than if chopped hot after cooking. Destruction of vitamin r enntimieq anirklv after the vegetable has be?n cooked and for- this reason nas oeen cooxea ana ror mis reason it must be served as soon as possible. Although it is advisable to include some raw fruit or vegetable in each Jay’s diet, there are many reasons for the inclusion of well-cooked vegetables S - This applies particularly in the - case of young children and older persons whose digestive systems are not capable of dealing with large quantities of unsoftened cellulose, Cooking also converts starch into a more easily digestible substance and j n many cases improves palatability. Flavour - Flavour as well as nutritive value mus be retained, and to do this short co° kin S periods are better, because =°° kin S will either destroy the flavour or make it too strong. The comparison between cabbage cooked for 10 minutes and that cooked for j hour is a good example. Apart from spoiling the flavour, long cooking will affect the colour, particularly of green vegetables. It is important to add the right amount of salt during cooking an d other suitable flavourings for different vegetables. Pepper is added after cooking, and butter, parsley, chives, mace, or paprika may all be used to give colour and variety. • Colour . . Vegetables are sometimes classified according to colour into green, yellow, white, and red, and some knowledge of the effects of heat, acid, and alkali on these pigments is useful as a guide to their cookery.

Green vegetables: The colouring matter is slightly soluble in water, but when they are cooked quickly in boilng salted water this colour is well preserved. Alkali, such as soda, will „ this colour, though acid turns o i lve green. However, the practice of adding soda to green vegetables to intensify colour is not advisable, as it destroys some of the vitamins and pro - duces an unpleasant texture. Yellow vegetables: The colouring matter is stable to heat, acid, and alkali, and therefore cooking has little effect on it. White vegetables: The colouring matter s soluble in water, colourless j n a(dd and ye ii ow n alkali and heat will produce a greyish brown. To preserve their whiteness these vegetables should be cooked in a small amount of water without the addition q-p alkali for the shortest nossible time Iron also affects white vegetables, giving them a green or brown tinge, so that they should not be cooked in Ton or clapped enamel saucepans, Red colouring, present in red cabbage and beetroot, is readily soluble in water, hence the advisability of cooking beetroot with its skin on. Alkali will change this red to a purplish colour; acid will produce a more , intense red. When vinegar is added to beetroot a rich colour develops. As the objects in cooking vegetables are:— 1. To preserve maximum nutritive value; „ , , . .... , 2 ' TP. + . l J? l Pf ove palatability and digestibility; 3 To preserve flavour and colour; and n variptv 4 - To Provide variety, it is necessary to review cookery methods and to find the most efficient, Some methods are suited to all types

of vegetables and others to specific varieties. Pressure Cooking As length of time of cooking is very important in conserving nutrients in vegetables, the pressure cooker ensures a minimum loss. Only a small amount of water is necessary and this . helps to prevent loss through leaching. Care must be exercised to prevent overcooking, but if the manufacturer’s directions are followed carefully, pressure cooking will result in considerable saving not only in fuel but in the nutritive value of the vegetable. This method is suitable for all types of vegetables. Baking Another good method for preventing loss of nutrient is by baking vegetables in their skins. Potatoes and kumaras may be cooked this way. After careful washing and scrubbing they are brushed with melted butter or salad oil and placed in a hot oven at 400 degrees F. The skin should be kept whole during cooking, as this retains the steam and produces a floury product. To test for “doneness” they are pressed between the fingers. When cooked they are pricked with a fork to form a cross on top so that some ot the floury interior is forced through the skin. Butter is added and a garnish of paprika or chopped parsley.

Pan Cooking

Pan cooking is suitable for such vegetables as cabbage, spinach, shredded french beans, and mushrooms. After the vegetables are washed and prepared they are placed in a heavy-base shallow pan containing a small amount of melted butter. They are then sprinkled with salt, covered with a tightly fitting lid, and cooked over modefate heat. The pan is shaken occasionally to prevent the vegetables from sticking. The vegetables are cooked in their own steam; they cook quickly, and there is no “leaching”, with the result that a high proportion of nutrients is retained. Flavour also is particularly good. Young root vegetables may also be cooked this way provided they are covered with wet lettuce leaves, which will provide sufficient moisture for conversion to steam.

A somewhat similar principle is involved in the use of a “waterless cooker”, which will cook a whole meal over one burner. When vegetables are to be cooked by this method they should be moist from washing or have 2 or 3 tablespoons of water added to provide the necessary steam. Cooking by this means is not quicker than other steaming methods, but the cooker may be of use where limited top space is available. It is suitable only for root vegetables.

Boiling

Boiling is probably the most commonly used method of vegetable cookery and the one where faulty procedures lead to greatest nutritive losses. The majority of vegetables may be cooked by boiling, and if correct procedures are adopted, the losses can be reduced considerably. The prepared vegetables are added to a small quantity of boiling, salted water, the pan covered tightly with a lid, and the water brought back to boiling as quickly as possible. They

are then cooked at a moderate rate until tender, and drained, seasoned, and served immediately. The vegetable water should be concentrated and used for soup, sauce, or gravy. If it is necessary to replenish the water during cooking, it must be boiling. If butter is plentiful, a small piece added to the water will help to prevent sticking and improve the flavour. Roasting Careful methods must be used in roasting; otherwise a fatty, indigestible product will result. Roasting increases the energy value of the vegetable by the absorption of fat, but there are greater losses of vitamin C than in boiling. However, roast vegetables, if crisp and golden brown, are a popular addition to a meal, and as they generally accompany a green vegetable, can be included for variety. Carrots, marrow, pumpkin, onions, parsnips, potatoes, and kumaras may all be roasted. To avoid a fatty product and to reduce the cooking time the fat used must be hot. The vegetables should be wiped with a cloth to remove moisture and to prevent spattering. If desired, potatoes and kumaras may be rolled in seasoned flour. The prepared vegetables can be placed either round the roast or in a roasting pan containing hot fat to the depth of about Jin. They are then cooked in a moderate oven, with occasional basting and turning to ensure even browning. The fat is then poured off and, if necessary, the vegetable may be returned to the oven for further browning. Frying ■ Frying has its uses in providing texture contrasts, but vegetables cooked in this way are generally cut in small portions and so tend to lose nutrients readily. However, as an accompaniment to a meal such foods as French-fried potatoes, Saratoga chips,

or sprigs of cauliflower dipped in egg and crumbs and fried can be very appetising. Tomatoes, too, can be fried, and in these little loss occurs, as the vitamin C of tomatoes is comparatively stable to heat. When foods are fried in deep fat it is necessary to have the fat at the correct temperature. The bread tests which were given in the article Deep-fat Frying” in the July 1949 issue of the “Journal of Agriculture” are a simple means of gauging temperature. Braising Further variations can be introduced by braising, and carrots and other root vegetables, celery, peas, onions, leeks, etc., may be cooked by this method either alone or in combination. The vegetables are prepared, sauted in a little fat or butter, placed in a casserole, and seasoned. A small amount of stock is added and the casserole covered with a lid and placed in a moderate oven to cook. Any remaining stock should be used as a sauce. Whatever the method used, the following points should be observed: 1 Use the vegetable as soon as possible after gathering it from the garden. 2. Cook it without paring when possible. 3. Cook it in a minimum amount of water. See that the water is boiling. 4. Cover the saucepan tightly. Cook for the shortest possible time. 5. Use the water for sauce, soup, or gravy. 6. Avoid the use of soda. 7. Use as soon as possible after cooking is completed; “keeping hot is destructive of nutrient values and flavour. An exception is sometimes made to point 4 in the case of strong-flavoured vegetables, such as cabbage, onions,

turnips, and cauliflower, which contain sulphur compounds. These compounds are volatile and will pass off in steam. After the cooking water has returned to boiling point the lid may be removed for a few minutes to release these vapours and then replaced and cooking carried out as before. With fresh vegetables, however, this should not be necessary. Infinite variety can be added to the menu by clever use of all types of vegetables. Recipe books abound with suggestions and there is no reason to cling to stereotyped service. Recipes may also be found in back numbers of the “Journal of Agriculture”: “Variety in Salads” (February 1947), “Savoury Vegetable Dishes” (April 1949), and “Hot Tea Dishes are Important for Cold Days” (October 1950). The home gardener can introduce a great selection of both vegetables and herbs from which salads and vegetable dishes can be made artistic and satisfying. Most gardens have a supply of parsley, mint, and chives and, perhaps, of sage and thyme, but few possess watercress, endive, mustard and cress, tarragon, horse-radish, or rosemary. To try to improve a faulty dietary habit New Zealanders should eat more vegetables both raw and cooked and serve them as a main dish frequently. A cheese sauce, a milky basis to a soup, or the addition of pea meal, dried peas, beans, or lentils will supplement the protein in a vegetable dish and provide a nutritious meal. Combination Vegetable Plate For a luncheon or tea dish, combination vegetable plate will provide a welcome change from meat or fish. It is a good method of using left-over vegetables. All kinds of vegetables can be used, but a contrast in colour and texture is desirable. The following are suggestions for each season of the year: — Spring Creamed potatoes (cubed cooked potatoes, reheated in thin white sauce) Spinach with egg garnish Buttered carrots Summer New potatoes, parsley butter Green peas and beans Grilled tomato with cheese Autumn French-fried potatoes Cauliflower with cheese sauce Mixed diced vegetables Winter ( Baked stuffed potato (with chopped parsley or chives, minced ham, or grated cheese added) Brussels sprouts Celery and white sauce Serve with grilled bacon if desired Vegetable Chowder (Serves 4) 1 onion sliced i cup of diced bacon 1 cup of diced carrot 1 tablespoon of 1 cup of diced potato chopped parsley 1 cup of diced swede 1 teaspoon of salt 1 cup of vegetable Few grains of pepper stock or water 4 cracker biscuits 1 cup of milk Cook the bacon in an aluminium saucepan over low heat. Add the onion and cook till golden yellow. Add remaining vegetables, salt, pepper, and stock and cook till tender. Add the milk and reheat. Taste and season if necessary. Add chopped parsley and pour over crumbled crackers and, serve.

Vegetable Method j Time (minutes) Artichokes (Jerusalem) Scrub well; steam or boil; remove skins after cooking or peel thinly before cooking; drain. Serve with butter, chopped parsley, or with white sauce. Or peel and roast in a little hot fat. Boil 15-20 Roast 40-50 Asparagus. Wash well, scrape thick ends, and trim; tie in bundles with fine string; boil in deep saucepan with heads up; drain. Serve with melted butter or Hollandaise sauce. Boil 20-30 Beans, broad Young beans. Wash; leave whole or slice. Older beans: Wash, shell, and boil; drain. Serve with melted butterBoil 10-15 or white or parsley sauce. Boil 30-40 Beans, broad Young beans. Wash; leave whole or slice. Older beans: Wash, shell, and boil; drain. Serve with melted butterBoil 10-15 or white or parsley sauce. Boil 30-40 Beans, french . Wash, cut off tops and tails, and string. Cut into Jin. or lin. pieces or slice diagonally; boil; drain. Serve with melted butter. Or pan cook. Boil 20-30 ■ Pan cook 8-10 shredded Beans, haricot (dried) Pour boiling water over beans and soak for 4 to 6 hours; simmer till tender; drain. Serve with melted butter and chopped parsley. Simmer 3 to 4 hours Beetroot Cut off tops, leaving about lin. of stalk to prevent “bleeding”. Wash without breaking the skin. Boil with skin on in water to cover. Drain, slice, and add to seasoned vinegar or cut in cubes and serve hot in a suitable sauce. Boil 14-2 hours Brussels sprouts Remove wilted leaves; cut off stalks; wash well; boil, drain, and serve with melted butter. Boil 10-15 Cabbage Remove coarse outer leaves, cut in quarters., and remove core if woody; shred with sharp knife; boil, drain, add pepper (if desired), and butter. Or pan cook. Boil 10-15 Pan cook 8-10 Carrots Scrub and leave whole if young; boil or steam. Wash and scrape old carrots; slice, dice, or cut lengthwise; boil, steam, or roast. . Serve with butter and chopped parsley or with white sauce if boiled or steamed. They may also be mashed and served alone or with mashed parsnips. Boil 15-20 Steam 20-30 Boil 20-30 Steam 30-40 Roast 50-60 Cauliflower Remove coarse outer leaves and hard core; break into sprigs or leave whole; boil with heads up. Drain and serve with butter or well-seasoned sauce. Boil 25-30 (whole) Boil 10-15 (sprigs) Boil 15-20 Celery Remove root, outer stalks, and most of green top. Separate the • stalks and wash well with vegetable brush. Cut into 1J to 2in. strips; boil; drain. Serve with white sauce or variation. Kumaras As for potatoes. — Leeks Remove the roots and coarse leaves, and, if necessary, part of the green top. If muddy, cut in halves lengthwise. Wash well; cut into 3in. lengths. Boil, drain, and serveBoil 15-20 Leeks Remove the roots and coarse leaves, and, if necessary, part of the green top. If muddy, cut in halves lengthwise. Wash well; cut into 3in. lengths. Boil, drain, and serve with melted butter or white sauce. Boil 15-20 Marrow Wash; cut through centre lengthwise; remove seeds and pith with sharp-edged cooking spoon; cut in suitable portions. If young, cook with skin on; otherwise peel. Boil and drain well, or steam. Serve with melted butter and chopped parsley or white sauce or variation, or remove skin and roast. Boil 10-15 Steam 20-25 Roast 35-45 Mushrooms Rinse in cold, salted water and drain on a cloth; trim the stalks, and peel; pan cook, saute, or cook in milk and thicken before serving. Pan cook 10-15 Saute 10-15 Onions Peel and remove tough outer layers if large, cut in halves; boil; drain well. Serve with butter, white sauce, or variation. Or roast or saute. Boil 20-35 Roast 45-60 Parsnips Scrub, peel (if old), or scrape. Remove the hard centre if necessary. Cut in suitable sizes; boil or steam; drain, Boil 20-30 and serve with butter, salt and pepper; or mash. Steam 30-40 Or roast. Roast 50-60 Parsnips Scrub, peel (if old), or scrape. Remove the hard if necessary. Cut in suitable sizes; boil or steam; Boil 20-30 and serve with butter, salt and pepper; or mash.Steam 30-40 Or roast. Roast 50-60 centre drain. Peas Shell and rinse in cold water; boil; add a sprig of mint and, if desired, a small quantity of sugar; drain; serve with butter. Boil 10-20 Potatoes (new) Scrub or scrape boil drain; serve with parsley and butter. Boil 15-20 Potatoes (old) Wash and scrub if cooking with skins on; or wash and peel; boil and drain, or steam. Serve with melted butter and chopped parsley, or seasoned and mashed. Or roast, bake, or deep-fat fry at 395 degrees. Boil 25-40 Steam 30-45 Roast 60-75 Bake 45-60 Pumpkin Treat as for marrow. Boil 20-30 Steam 35-40 Roast 50-60 Silver beet Remove the roots; wash and separate the green and white portions. These may be cooked separately or together. Cut the white portions into 11 to 2in. lengths and shred the green portions. If the portions are to be cooked together, start cooking the white portion while shredding the green. Serve the green or mixed green and white with butter, or the white separately with white sauce or variation. Boil stems 10-15 Boil green 5-10 Spinach Remove the roots and stalks; wash thoroughly in several waters. Pan cook, or cook without the addition of water. Drain and serve plain, or chop slightly and add butter. A pinch of nutmeg will improve the flavour. Boil 8-10 Pan cook 8-10 Swedes Wash and peel; cut into medium pieces; boil or steam. Drain and serve mashed with pepper and butter. Boil 20-30 Steam 30-40 Sweet corn Remove the husks and silk; wash; boil in water 1 to cover. Serve with butter. Boil 10-15 Turnips (white) Wash and peel. If small, leave whole; otherwise cut into portions. Boil and drain, or steam. Serve with butter and parsley or white sauce. Boil 15-20 Steam 25-30