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How Soy Bean Milk and Tofu is made?

Here is a brief flow chart of the process in making tofu. Over 3,000 years ago, wild Soy beans were discovered on the plains of eastern China. The Chinese people quickly recognized the tremendous value of this plant and named it one of their five sacred crops. Today Soy beans are often referred to us as the "Cow of China", as they provide nourishing "meat" (tofu) and "milk" Soy Bean Milk) to millions of people. Soy foods slowly found their way to North American tables, and are now staples for many nutrition conscious families. The great rise in the use of tofu and Soy milk in North America can be attributed to their convenience, good taste, but above all, their potential to promote health and prevent certain kinds of diseases.

SETTING THE THEME CONCERNING THE TECHNIQUES OF SOY-MILK AND TOFU PRODUCTION AT HOME BY - FRED HERZFELD

email:herzfeld@bigfoot.com
78 Glynn, Marsh Drive #59, Brunswick, Ga. 31525

TEN STEPS OF Soy Bean Milk AND TOFU PRODUCTION

Posted with permission from the author
MAKING TOFU (AND Soy Bean Milk) AT HOME
copyright 1997 Fred Herzfeld, Brunswick, Ga. 31520 USA

There are many grades of tofu from a very soft type called water-tofu (kinogoshi tofu in Japanese and suey-tofu in Chinese) to a very hard type. These different types are used in different ways and for different foods, but all of them are made in essentially the same way. One kilogram (2 pounds 3 ounces) of store bought soybeans will make about 2 kilograms (4 pounds 6 ounces) of medium tofu. The same amount of soybeans will produce up to 10 kilograms (22 pounds) of kinogoshi tofu. In commercial production with soybeans of a known cultivator and by exactly controlling the extraction of the soybean protein the ration can be much larger.

1. SELECTING THE (SOY) BEANS

The best beans are fresh, dry, and from the current harvest year. They should all be whole (no splits) and should not contain other seeds, dirt, stones or other materials. As the beans get older they make less tofu. This is because some of the protein of which the tofu is made becomes non-water Soluble so that the milk that is made will be thinner and therefore yield less tofu. The color of the outside skin (testa) of the soybeans should be a very light tan to almost white. If the color is yellow or gray or if it has a "black-eye" (hilum), the color of the tofu will be either yellow or gray or both and will not be considered the best quality tofu. The coloring due to the testa or hilum can be prevented by removing the testa before the boiling stage. This is best performed just after soaking.

2. CLEANING THE SEEDS (SOY BEANS)

Weigh out 1 kilogram (2.2 pounds=2 pounds 3 ounces) of beans. Put them in a 5 liter (5 quart) container with 3 to 4 liters (quarts) of water. With good clean seeds the water will stay clear and no debris will rise to the surface of the water. Pour the water off slowly or pour into a large strainer and repeat if necessary until the water remains clear and no debris floats to the top. Check that there are no stones or other foreign materials which are heavier than water and which has collected at the bottom. If necessary remove these foreign materials.

3. SOAKING (THE SOY BEANS)

After draining the last time in step 2, add 3 to 4 liters (quarts) of warm water at about 37 degrees C (98 degrees F) and let stand for 8 to 10 hours. During this time the temperature will drop to room temperature (about 20 degrees C or 68 degrees F) and the seeds will take up about an equal amount of water, and some bubbles will be seen at the surface. If drained and weighed at this time they should weigh in at about 2 kilograms (4 pounds 6 ounces) or more.

4. REMOVING THE TESTA (FROM THE SOY BEANS)

If the seed were of a good color and the hilum was not too dark this step can be skipped. Of course it can be skipped anyway. If the seed coats are to be removed place both hands in the pot and gently rub the seeds between the palms of your hands, lifting your hands out of the water and letting the seeds drop back into the pot as you rub them. The seed coats will split and separate from the seed (cotyledons). When it looks like all the seed coats have separated, run water into the pot and the seed coats will flow over the top leaving the heavier cotyledons on the bottom. In this way almost all the seed coats will be removed and will not be able to discolor the tofu.

5. MAKING Soy Bean Milk (THE MOST IMPORTANT PART)

Heat 6 liters (6 quarts) of water to about 70 degrees C (160 degrees F) and mix with the drained soybeans (2.2 lbs.) from either step 3 or step 4. To some extent the temperature of the water which is used in this extraction step can control the hardness of the tofu. This is because the various proteins in the soybean have different best temperatures at which they are most Soluble. The temperature given here is best for home or cottage production of tofu. In addition it is very important to know the hardness of the water you are using. Most municipal water supplies will give no problems, but occasionally water can be so hard (contains a large amount of calcium or magnesium) that the step of curdling the milk with a magnesium salt (step 8) will occur by itself in step 6. This makes it impossible to make tofu. If your water is this hard you must use a good quality water from somewhere else. If your blender cannot hold at least a 10 liter (quart), you must do the grinding or blending piecemeal. Place some seed and water in your blender and blend for a minute or so at a medium speed until the liquid feel as if it has a very very fine grit in it. If you blend too long and you cannot feel any grit between your fingers you are blending too long and may have trouble removing the fibers from the milk. After all the seeds and the water has been processed in the blender, it must be pressed. If you do not have a press, spread a cheesecloth in a large sieve or colander and place on top of an empty pot. Pour some of the ground beans into the open cheesecloth and then pick up the edges of the cheesecloth and squeeze the milk out of the mass. The milk should flow into the pot. If the liquid is too hot to handle use thick rubber gloves to protect your hands or let the ground beans cool enough so that you can handle them sagely. Repeat this pressing step as often as necessary until all the ground mass has had the milk squeezed out. I like to filter it again at this point using a clean cheesecloth. If you did not get 6 liters (quarts) of milk add some hot water to make it to 6 liters (quarts).

6. SIMMERING THE (SOY) MILK

The six liters (quarts) of soymilk must now be heated to about 95 degrees C (200 degrees F) and held there for about 6 to 8 minutes. Do not bring to a boil. Use a thermometer to check on the temperature. Boiling Soy Bean Milk will very easily boil over and make lots of suds because the milk contains plant saponins. These plant saponins act just like soap or detergents. Stir constantly or the milk will burn at the bottom of the pot. It does not hurt the process of making tofu but the pot will be harder to clean and some burnt taste may transfer to the hot milk and then to the tofu. The few minutes at 95 degrees C (200 degrees F) are necessary to deactivate a trypsin inhibitor which is present in raw soybeans. If it is not deactivated humans and most animals using the trypsin enzyme will not be able to digest the soybean proteins (or any other protein eaten at the same time). You now have soymilk which can be consumed as such especially if thinned with an equal amount of water along with the addition of some sugar. This soymilk drink is consumed in most oriental countries.
 

7. SOY BEAN MILK SKIN

The milk should now be allowed to cool to about 80 degrees C (180 degrees F). Use a thermometer! As the milk cools a skin will form on the top of the milk. When the temperature of the milk has cooled to 80 degrees C (180 degrees F) cut the skin away from the sides of the pot with a sharp knife and lift the skin out by placing a chop-stick under it and lifting it out. To get a flat sheet of skin place it on a sheet of plastic and let it air dry for about 24 hours. The skin is used in many ways, and in its dry form represents protein which can be stored for a long time. One way I enjoy the skin is to use it as a wrapping for spring rolls. A spring roll made this way thus has an extremely thin covering.
 

8. CURDLING THE MILK (MAKING TOFU CURDS)

When the milk has almost cooled to 80 degrees C (180 degrees F) heat a cup (250 ml.) of water to boiling and add 30 grams of Nagari (Magnesium Chloride) buy the correct Japanesse food grade material. Stir to disperse the powder. It will not disSolve. When the milk has cooled to 80 degrees C (180 degrees F) pour the plaster into the hot milk very slowly while constantly stirring. It should take about 1 to 2; minutes to pour and stir the plaster into the milk. This timing is important. If you take much longer the milk will gel before all the nagari is in the milk and the resulting tofu will be much softer and less cohesive. On the other hand if you dump the Nagari all at once it may curdle too fast and become very grainy and hard. Usually after about two minutes at the temperature specified the milk will start to gel. Even if you have a little plaster left over, STOP. If at this point you continue to stir you will break the gel which is forming and once broken it will not recover. Cover the pot and let it stand for about 20 minutes. The cover is necessary so that the tofu which is forming does not form a hard skin on the top surface.
 

9. PRESSING THE CURD (TOFU)

To test if the tofu is ready either for consumption as water-tofu (Chinese-suey tofu; Japanese-kinogoshi tofu) take the thermometer and stick it into the tofu about 6 to 10 centimeters (about 2.5 to 4 inches) deep, then remove it If the yellowish liquid (the whey) that then fills the hole where the thermometer had been is clear (not cloudy) the tofu is ready for pressing. The temperature of the tofu at this point should be about 65 to 70 degrees C (about 150 to 160 degrees F). If you want water-tofu let it continue to cool to room temperature without disturbing it. It is then ready to serve. For regular tofu the curd is ladled into a tofu forming box. For 1 kilogram of dry seeds which yield about 2 kilograms of normal tofu the box should be about 16 cm. by 26 cm. by about 11 cm./ high (6 to 12; by 10 to 12; by 5 inches deep). It should have holes about 5 or 6 mm in diameter (about 14; inch in diameter) on the sides and bottom so that the whey can bleed away, The box is lined with cheese cloth in both directions so the tofu curds will not squeeze through the holes. Once all of the curd has been transferred the remaining cloth is folded over the curds and a small board just smaller than the box opening is placed on top of the covered curds. A weight of about 3 kilograms (about 6 to 12; pounds) is placed on the board to help press the curds. The tofu is then left to cool and bleed a clear yellowish liquid (whey) for about 2 to 3 hours. The longer it is pressed the harder it will be and the less tofu you will get. But there are limits on the hardness as determined by the amount of Nagari which was used in the curdling step. This is one reason why tofu is always stored in water.

10. DEBOXING THE FINISHED TOFU

When the tofu has been pressed for about 2 hours place the box containing the tofu in a large clean container filled with water, and under water remove the box and unwrap the cheese cloth from the tofu. Cut the tofu into about 4 pieces and store them in the refrigerator until well chilled - usually about 2 hours. But do not freeze the tofu. Frozen tofu which is defrosted will release all of the water held by the gel and form a open celled sponge made entirely of edible protein. This form can be dried and also (like soymilk skin) stored for a very long time without refrigeration (remember the Chinese did not have refrigerators). Tofu kept under water, with the water changed every day, will keep almost 2 weeks but it is best consumed in the first 4 to 5 days. In the orient it is usually consumed within the first day or so.


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