Soya
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
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
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
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.
Soya 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
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
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.
Further Information
·
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 provamel@vdmuk-rs.co.uk
· 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.