SOYA PREPARATIONS
The Soya bean is the seed of the leguminous soya bean plant. Soya foods have been a staple of the Chinese diet for over 4000 years but have only been widely consumed in Western countries since the 1960s. Soya foods include tofu, tempeh, textured vegetable protein (chunks, mince etc.), miso, soya sauces, oil and margarine, and soya dairy alternatives.
Soya is an excellent source of high-quality protein, low in saturated fats, and 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 increased consumption of soya. Soya diets have also been shown to reduce levels of serum cholesterol.
TEXTURED VEGETABLE PROTEIN
Textured vegetable protein is defatted soya flour which has been processed and dried to give a substance with a sponge-like texture that may be flavoured to resemble meat. Soya beans are dehulled, and their oil is extracted before being ground into flour. This flour is then mixed with water to remove soluble carbohydrates, and the residue is textured by spinning or extrusion. Extrusion involves passing heated soya residue from a high-pressure area to a reduced-pressure place through a nozzle, which expands the soya protein. The soya protein is then dehydrated and may be cut into small chunks or ground into granules. Textured vegetable protein may be purchased either unflavoured or flavoured to resemble meat. It is prepared simply by mixing it with water or stock and leaving it to stand for a few minutes, after which it may be incorporated into recipes as a meat substitute. Soya protein is also incorporated into various vegetarian burgers, sausages, canned foods, etc. As well as being a good source of fibre and high-quality protein, textured vegetable protein is fortified with vitamin B12.
TOFU
Tofu is a 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 more forceful kind may also be purchased smoked or marinated. Tofu tends to be pretty bland tasting and is best used in recipes where other ingredients impart flavour. 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 contains calcium, iron, and vitamins B1, B2 and B3.
TEMPEH
Tempeh is a fermented soya bean paste made by inoculating cooked beans with the mould Rhizopus oligos porous. 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
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 gives taste to soups, stews, casseroles, and sauces.
SOYA SAUCES
Authentic soya sauce, called Shoyu, is made by fermenting beans with cracked roasted wheat, salt and water. Tamari is similar but slightly more robust 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 the market is not authentic. Still, it 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. 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 whole-fat cow’s milk, soya milk has a lower fat content, a lower proportion of saturated fat, and no cholesterol. It is common in carbohydrates and provides a good source of protein. Some brands may be fortified with calcium, vitamin D2, B12, and vitamin B2. Soya milk offers 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 milk is available for babies. Other soya milk is not suitable as the sole food for young infants.
Previously, the media linked soya milk with high aluminium content. However, the aluminium content of soya milk is generally lower than cow’s milk and falls well within acceptable limits dictated by the World Health Organisation.
OTHER SOYA PRODUCTS
Soya oil and margarine are widely used and are high in polyunsaturated and low in saturated fats. Other less readily 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
Mycoprotein is a food made by continuous fermentation of the fungus, Fusarium gramineous. 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 as 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.
WHEAT PROTEIN
Wheat protein is derived from wheat gluten. It is sometimes called Seitan. 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 is more similar to the core than textured vegetables or mycoproteins and is used as a meat substitute in various foods. It is available in some health food stores.