Specialist Products - Soya
The soya bean is a pulse which has an unusually high content of protein in a usable proportion.
By itself it is not very appetising and takes hours to cook (approximately 1½ hours) but a variety of products are made from soya:
Tofu is a curd made from soya beans. For many years it has been a staple food of the Chinese and Japanese diet.
Soya Beans are a complete protein, containing all of the essential amino acids, but are low in the sulphur-containing amino acids, methionine and cysteine. Grain products are rich in these amino acids and are excellent complements to soya beans, creating a cheap, digestible and highly nutritious food.
Tofu is a useful low-fibre source of protein. and is low in calories with 8 oz having only 147 calories, thus making it a suitable food for people on calorie-controlled diets.
In East Asia tofu is recommended by doctors to people who are on a starch-reduced diet.
As well as being low in calories and easily digested, it contains very few saturated fats and no cholesterol.
The mineral content of tofu is interesting as it is high in minerals. Magnesium chloride (nigari) or calcium sulphate are used to solidify soya milk thus giving tofu 50% more calcium weight-for-weight than cows’ milk. If utilising tofu in the vegan diet to benefit bone health, tofu with at least 200mg calcium per 100g should be selected.
Other minerals present in tofu are iron, phosphorous, potassium and sodium. Fat-soluble vitamin E, B vitamins and choline are present in tofu.
In the process of making tofu, the ground-down soya beans (GO) are boiled to kill any trypsin inhibitors that are present in soya beans and this process helps to minimise the flatulence that can be caused by eating beans.
The fibre is also removed, thus making tofu an easy to digest food. The digestible rate of soya beans is 68%, but the digestible rate of tofu is 90%. It is usually available in firm and silken consistencies. Silken tofu has been pressed only lightly and has a soft creamy texture. Firm tofu is more like cheese and is available in plain, smoked and marinated varieties.
Tofu becomes chewy if frozen and if put in layers with vegetables will hold water in pockets.
Buying and storing tofu
It is best to buy tofu as fresh as possible (tofu tastes better the fresher it is). The most popular variety is a chilled product with a shelf life of approximately one month. There are plans to reintroduce an ambient silken tofu which would not need refrigeration and would have a shelf life of approximately 6 months.
Tempeh is a soya product made from dehulled soya beans and inoculated with a spore called Rhizopus Oligosporus. The soya beans are soaked and cooked, after which they are dehulled. Once the soya beans have been dehulled they are inoculated with Rhizopus Oligosporus, packed in containers and incubated. With the spore forming on the soya beans it makes the tempeh into a solid cake-type food. Tempeh can be made on any medium e.g. chick peas, wheat, etc., but soya tempeh has a higher nutritional value.
Nutritional value of tempeh
Tempeh is very rich in protein (20%).
Tempeh has no cholesterol and is high in polyunsaturated fats.
TVP (textured vegetable protein)
TVP is basically dried foam made from soya flour. The flour which is left behind after the oil has been extracted is mixed with water to form a dough, heated under pressure and then forced through a small nozzle. It expands as it is extruded due to a fall in pressure and has a texture rather like a sponge. It is then cut into chunks or ground into mince. Flavoured and plain varieties are available.
TVP is low in fat with a high protein content - fortified versions are available. (It is recommended that the ingredients label is checked for this information).
Tamari, Miso and Shoyu
Miso is made by fermenting soya beans and rice, barley and wheat together under pressure for a couple of years until a thick paste has been formed. It is rich in good quality protein, B vitamins and minerals and very strongly flavoured.
Tamari and Shoyu are liquids formed during the production of miso and they are the true soya sauces, Tamari being a stronger version of Shoyu.
Soya Milk and Soya Yoghurts
A range of soya milks is available. They are naturally lower in calcium, Vitamin D and B12 than cows milk, so it is important to ensure that only fortified brands are used.
Note: 3.5 litres of fortified soya milk (400 ml per day) containing at least 120mg calcium per 100ml is sufficient to ensure the calcium reference nutrient intake (700mg per day) is met taking account of calcium from other sources and to ensure a good protein intake.
Calcium is essential in the assimilation of B12 and in turn calcium requires a source of magnesium. Note: Both calcium and magnesium, will be adequate if the guidelines in this pack are followed.
Magnesium sources: cashew nuts, almonds, broccoli, wholegrains, wheatgerm, prunes and bananas.
The main contents of this information were obtained from a course at Bradford University arranged by HMPS - Corby, courtesy Ms. V. Owen, Kitchen Department HMP Bullwood Hall.