The soya bean is the seed of the leguminous soya bean plant. Soya foods have been a staple part of the Chinese diet for over 4000 years but have only been widely consumed in Western countries since the 1960's. Soya foods include tofu, tempeh, textured vegetable protein (TVP), miso, soya sauces, soya oil and margarine, and soya dairy alternatives.
Soya is an excellent source of high quality protein, is low in saturated fats and is cholesterol free. Recent research has indicated soya has several beneficial effects on health in addition to its nutritional benefits. Soya beans contain high concentrations of several compounds which have demonstrated anti-carcinogenic activity. These include isoflavonoids, protease inhibitors and phytic acid. The low incidence of breast and colon cancer in China and Japan has been partially attributed to the high consumption of soya products. The low incidence of menopausal symptoms in Japanese women has also been attributed to high consumption of soya. Soya diets have also been shown to reduce levels of serum cholesterol.
Textured Vegetable Protein
Textured vegetable protein (TVP) is basically defatted soya flour which has been processed and dried to give a substance with a sponge-like texture which may be flavoured to resemble meat. Soya beans are dehulled and their oil extracted before being ground into flour. This flour is then mixed with water to remove soluble carbohydrate and the residue is textured by either spinning or extrusion. Extrusion involves passing heated soya residue from a high pressure area to a reduced pressure area through a nozzle resulting in the soya protein expanding. The soya protein is then dehydrated and may be either cut into small chunks or ground into granules. TVP may be purchased either unflavoured or flavoured to resemble meat. It is prepared simply by mixing with water or stock and leaving to stand for a few minutes, after which it may be incorporated into recipes as a meat substitute. Soya protein is also available incorporated into various vegetarian burgers, sausages, canned foods etc. As well as being a good source of fibre and high quality protein, TVP is fortified with vitamin-B12.
Tofu is soya bean curd made from coagulated soya milk. Soya beans are soaked, crushed and heated to produce soya milk to which a coagulating agent such as calcium sulphate or calcium chloride is added. The resulting soya curd is then pressed to give tofu. Tofu is sometimes known as soya cheese, and is sold as blocks packaged in water. It can be bought as silken tofu, which is soft and creamy in texture, or as a denser, firmer version. The firmer kind may also be purchased smoked or marinated. Tofu tends be fairly bland tasting and is best used in recipes where flavour is imparted by other ingredients. Firm tofu may be marinated, fried, stir-fried, deep-fried, sauteed, diced and added to salads or casseroles. Silken tofu can be used for dips, spreads, sauces and sweet dishes. As well as having a high protein content, tofu also contains calcium, iron, and vitamins B1, B2 and B3. (see Tofu Recipes)
Tempeh is a fermented soya bean paste made by inoculating cooked soya beans with the mould Rhizopus oligosporous. This mould forms a mycelium holding the soya beans together and is responsible for the black specks in tempeh. Tempeh has a chewy texture and distinctive flavour and can be used as a meat substitute in recipes. It may be deep-fried, shallow-fried, baked or steamed.
Miso is a fermented condiment made from soya beans, grain (rice or barley), salt and water. Miso production involves steaming polished rice which is then inoculated with the fungus Aspergillus oryzae and left to ferment to give an end product called koji. Koji is then mixed with soya beans which have been heated and extruded to form strands, together with salt and water. This is then left to ferment in large vats. Miso varies widely in flavour, colour, texture and aroma. It is used to give flavour to soups, stews, casseroles, and sauces.
True soya sauce, called shoyu, is made by fermenting soya beans with cracked roasted wheat, salt and water. Tamari is similar but slightly stronger and made without wheat (and so is gluten-free). Fermentation for shoyu and tamari takes about one year. Much of the soya sauce available in supermarkets is not true soya sauce but is made by chemical hydrolysis from defatted soya flour, caramel colouring, and corn syrup without any fermentation process.
Soya Dairy Alternatives
Soya milk is an alternative to dairy milk and is widely available in supermarkets and health food stores. It is most commonly made by soaking soya beans in water which are then strained to remove the fibre. It can also be made from soya protein isolate or soya flour. Compared to full fat cow's milk, soya milk has a lower fat content, a lower proportion of saturated fat, and no cholesterol. It is low in carbohydrate and provides a good source of protein. Some brands may be fortified with calcium, vitamin-D2, vitamin-B12 and vitamin-B2. Soya milk provides an alternative to cow's milk for people with cow's milk protein and lactose intolerance. Cow's milk allergy is most common in infants, and specially formulated soya milks are available for babies. Other soya milks are not suitable as sole foods for young infants.
Previously, the media has linked soya milk with having a high aluminium content. However, the aluminium content of soya milks is generally lower than cow's milk, and falls well within acceptable limits dictated by the World Health Organisation. Aluminium in soya milks can be regarded as negligible. Certain infant formulas (both cow's milk and soya milk based) produced from concentrates have been reported as having high levels of aluminium and their suitability for infants has been questioned.
A number of different brands of soya milk may be purchased. These may be sweetened or unsweetened and vary in flavour. Market leaders are Provamel, Granose and Plamil. Some supermarkets also sell own-brand soya milk. In addition to soya milk, a range of flavoured soya desert and soya yoghurt products are available.
Other Soya Products
Soya oil and margarine are widely used and are high in polyunsaturated fats and low in saturated fats. Other less easily available soya foods include soya sprouts, soya nuts (roasted and seasoned soya beans), natto (fermented soya beans made with a bacteria, Bacillus subtilis), yuba (the skin formed on heated soya milk), soya flakes, soya flour, and high protein soya isolates and concentrates.
Mycoprotein is a food made by continuous fermentation of the fungus, Fusarium gramineurum. The fungus is grown in a large fermentation tower to which oxygen, nitrogen, glucose, minerals, and vitamins are continually added. After harvesting, the fungus is heat treated to reduce its RNA content to World Health Organisation recommended levels before being filtered and drained. The resulting sheet of fungal mycelia is mixed with egg albumen which acts a binder. Flavouring and colouring may also be added. The mycoprotein is then textured to resemble meat, before being sliced, diced or shredded. Mycoprotein is a source of protein, fibre, biotin, iron and zinc, and is low in saturated fat.
Mycoprotein has been developed by Rank Hovis McDougall, and is marketed under the name of Quorn by Marlow Foods Ltd (owned by Astra Zeneca ). A wide range of Quorn ready meals are available including curries, pies, and casseroles, and it may also be purchased as chilled Quorn chunks. These may be grilled, sauteed, baked or casseroled.
Mycoprotein is potentially a very useful food item for vegetarians. Since early 2000 the Quorn deli and ingredients ranges have been approved by the Vegetarian Society since the albumin used as a binder in its manufacture has been changed in those ranges from a non free range to a free range egg source. However at present the ranges of ready meals, burgers, sausages etc still use eggs from a non free range source
Wheat protein is derived from wheat gluten. Gluten is extracted from wheat and then processed to resemble meat. Wheat protein is marketed under the name of Wheatpro by Lucas Ingredients of Bristol. It has a greater similarity to meat than TVP or mycoprotein and is used as a meat substitute in a range of foods. It is available in some health food stores.
Soya Information Service, PO Box 4, Stourbridge, West Midlands, DY9 8DQ.
· SoyaFoods, 27a Santos Road, London, SW18 1NT. SoyaFoods is the newsletter published by the American Soybean Association, 20-22 Rue du Commerce, 1040 Brussels, Belgium.
· The Soya Milk Information Bureau, (run by Provamel) PO Box 169, Banbury, Oxon, 0X16 9XE. Tel: 01295 277777 - We are now in a position to accept requests for general information with regard to Soya Milk at our email address firstname.lastname@example.org
· British Soya Milk Advisory Service, (run by Plamil) Bowles Well Gardens, Dover Road, Folkestone, Kent, CT19 6PQ
· Vegetable Protein Association, Food & Drink Federation, 6 Catherine Street, London, WC2B 5JJ.