Although the highest
quality protein is found in animal products (meat, milk, eggs and fish),
these products are expensive and often exceed the financial capacity of
people in the developing world. The soya bean is high in nutritional
value and provides a satisfactory alternative to animal products. It
belongs to the grain legumes (also called pulses) and contains good
quality protein, oil, vitamins (from the B-group) and minerals (iron and
calcium).
The production of tofu
consists of two main steps:
• the preparation of
soymilk;
• the coagulation of soymilk to form curds which are pressed to form
tofu cakes.
Soaking the soya beans
Soya beans are soaked
in cold water overnight or in very hot water for 2 to 3 hours, using 3
to 4 cups of water for each cup of dry soya beans. When the beans split
open easily and are flat on the inside, they are ready to be drained.
After the water is discarded, they should be washed in clean water.
Grinding and cooking the soya beans
A grinding rock, hand
mill or meat grinder can be used to grind the beans into flour. When all
the beans have been ground, boiling water (for each cup of dry soya
beans about 8 cups of cooking water are used) is gradually mixed to the
pulp and then it is left to simmer on the fire for 20 minutes. The
soymilk is stirred regularly to avoid burning.
Straining the soymilk
The cooked milk is now
sieved to extract the soymilk from the pulp using a filtering cloth. It
is placed into a sieve which is positioned over a pot, lined with a
filtering cloth. The cloth should be made from nylon or porous material
- either a flour or sugar bag can be used. The sides of the cloth are
held in each hand and moved up and down to roll the pulp back and forth
so it forms a ball. The cloth is twisted tightly and held over a clean
container while pressure is exerted onto it to extract the milk.
Soymilk
Soymilk is easily
digestible and one pint of it can provide over one half of a young
child’s daily protein requirement. It can be sweetened with sugar or
flavoured with chocolate, cinnamon or vanilla. Salt may also be added.
Coagulating soymilk
Soymilk is heated over
a fire and boiled for 3 to 5 minutes with continuous stirring. The pot
is removed from the heat and a 4% acetic acid solution is added to the
soymilk and stirred constantly until a good coagulum is formed. Vinegar
usually contains 4% acetic acid solution and for every litre of soymilk,
2 tablespoons of vinegar are used.
Straining the curds
When large white curds
can be seen floating in a clear yellow liquid, called whey, the soymilk
is completely curded and ready to be filtered through a clean cloth into
a suitable mould. The same method is used here as used in straining the
soymilk.
To form a block of
tofu, press the cloth lined tofu with a weight for about 20 minutes
which will reduce its water content by approximately 60%. This can be
sliced and fried or eaten plain with salt. Alternatively, the loose
curds can be scrambled in a pan with onion, tomatoes and salt and served
on bread.
Preservation of soymilk and tofu
Soymilk can be stored
in a bottle placed in a container of cold water. However, even in cool
weather, soymilk can only be kept for a day using this method.
Unseasoned block tofu
should be stored under water to prevent drying out and can be kept for 2
days in moderate temperatures.
When refrigeration is
available, soymilk can be kept for up to 5 days and tofu for about 10
days.
Soymilk that sours will
form into curds by natural fermentation. Providing the curds are solid
and not discoloured or slimy, they can be boiled for 30 to 40 minutes to
kill the bacteria and made into cheese. Tofu that becomes slightly sour
can also be eaten if boiled for 20 to 30 minutes.
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