Advantages of Soymilk Products

Soymilk Acceptance Problems

Improved Soymilk Processes

INTSOY Home and Village Processing

New Commercial Process

Making Dairy Analogs

Soy Yogurt

Soy Ice Cream

Developing Commercial Products

Benefits

Advantages of Soymilk Products

One of the simplest methods for converting soybeans to a high-quality food is to produce a beverage known as soymilk. This product contains virtually the same amount of protein as cow’s milk and is free of cholesterol and lactose. Soymilk is especially important for people who are allergic to the lactose in cow’s milk.

Although less serious in the United States or Europe, the inability to digest the milk sugar lactose widely occurs in developing nations. Rates from 50 to almost 100 percent have been recorded among population groups in Asia, Africa and Latin America.

Because soymilk contains no lactose and is relatively inexpensive, it offers an attractive alternative to cow’s milk for hundreds of millions of people in developing countries, as well as many people in developed countries.

Soymilk Acceptance Problems

Soymilk has been a staple in the Orient for many centuries. Traditionally, it is made by soaking the beans, grinding them with water, cooking the slurry, and then filtering to remove the sludge.

Unfortunately, the traditional soymilk has a distinctive beany flavor which is unacceptable to most consumers outside the Orient. This objectionable flavor results from the action of an enzyme when raw soybeans are ground and exposed to moisture.

The acceptability of soymilk further has been complicated by the unjustified tendency to compare it with cow’s milk. Thus, in producing a widely acceptable soymilk, it is essential to carefully cotrol a range of factors including flavor, color, viscosity and freshness.

Improved Soymilk Processes

Several of the problems associated with soymilk were solved as early as 1970 with a beverage developed by food scientists at the University of Illinois. The product is made by cooking and grinding the beans in a way that inactivates the enzyme responsible for causing the objectionable beany flavor.

The Illinois process used the whole soybean and produced a soy beverage with bland flavor, excellent suspension stability and good taste characteristics. Serious acceptance problems ensued, because the product tended to leave a chalky feeling in the mouth. Patent restrictions further limited the used of this process in many less developed areas.

INTSOY Home and Village Processing

Recently, INTSOY developed a new, inexpensive method to prepare soymilk at the home and village level. The following is a simplified form of this small-scale preparation process:

• Drop whole, raw soybeans directly into boiling water containing a small amount of sodium bicarbonate and blanch for five minutes.
• Drain the water, add the partially blanched beans to fresh boiling water containing sodium bicarbonate, and cook for five additional minutes.
• Drain the blanch water and grind the beans along with the additional boiling water in an electric blender or hand grinder.
• Stir the slurry well and filter with a finely woven, moist cheesecloth. Squeeze out as much milk as possible.
• Simmer the filtrate for 20 minutes.
• Add sugar and flavoring and pour into holding containers.

Heat treatment is the most important step. It is absolutely necessary to hydrate and thoroughly heat the raw soybeans before grinding into a slurry to prevent development of the typical beany flavor. This process adequately destroys the antinutritional Trypsin inhibitor.

Boiling times longer than recommended will reduce the amount of protein in the final product. The concentration of solids easily can be adjusted according to the final use of the soymilk.

New Commercial Process

Commercial soymilk processing equipment with an average capacity of 2,000 liters per hour is available for purchase with aseptic packaging from several sources at a cost of several million dollars. At present, there is a lack of available equipment and proven processing techniques for producing sterile product in volumes larger than the home level and less than 600 to 800 liters per hour.

A major focus of INTSOY research is on scaling up the improved soymilk processing techniques from the laboratory to the medium commercial scale. In simplified form, the process is as follows:

• Clean and size whole soybeans.
• Dry the beans by forced air in an oven.
• Split the hot beans in a dehuller roller.
• Separate the hulls and the cotyledons using an air blower.
• Blanch the dehulled soybeans in a steam kettle.
• Grind blanched beans on a continuous basis along with boiling water in a hammer mill.
• Continuously extract the soymilk from the ground slurry using the roller extractor from an accepted tofu machine.
• Pasteurize and homogenize the soymilk.

Long blanching times lower the recovery of nutrients. Very short cooking times are inadequate to destroy the enzyme that causes the beany flavor.

Making Dairy Analogs

The soymilk from this process is a bland product suitable for making a number of dairy analogs:

Soy Yogurt

Yogurt is a tasty and nutritious product made by fermenting cow’s milk to form an acidic gel. Soy yogurt is less acidic than regular yogurt and should have widespread consumer appeal. The steps for making soy yogurt are as follows:

• Manufacture the soymilk.
• Formulate the soymilk with sucrose and dextrose.
• Pasteurize and homogenize.
• Inoculate and incubate.

The culture must be carefully maintained. The temperature and time of incubation should be carefully controlled. The soymilk must be properly pasteurized to prevent contamination. A small amount of added sugar promotes the fermentation. The use of different sugars or sugar mixtures produce somewhat different flavors in the final product.

Soy Ice Cream

This product is prepared from the soymilk and added vegetable oil. It is formulated and manufactured as in the conventional dairy ice cream process. The soy ice cream stores well and has good melt-down characteristics.

Developing Commercial Products

An excellent soymilk containing more than five percent protein can be prepared using this scaled-up method. At that concentration, about 10 kilograms of dehulled soybeans are needed to produce about 50 kilograms of soymilk.

This product contains about 10 percent total solids. That compares to cow’s milk which has 10 to 12 percent solids, including about four percent protein. This soymilk should be nearly ideal as a base for commercial soft-serve ice cream products.

The okara or residue from the commercial process can be used immediately in baking or dried for later use as a high-fiber flour. The okara contains about eight percent protein on a wet basis or about 40 percent on a dry basis.

Benefits

The equipment used in this research is relatively inexpensive and widely available. It easily could be linked to a commercial soymilk operation with a volume of 100 to 200 liters per hour. With a larger roller extractor, the capacity could be expanded to as much as 600 to 800 liters per hour.

The new commercial-scale process being developed by INTSOY represents a major step towards effectively meeting the huge worldwide need for soymilk. The benefits should include the following:

• A soymilk plant producing 100 to 800 liters per hour would be much less expensive than the available turn-key operations.
• Smaller processing plants that prepare pasteurized products for local rather than nationwide distribution would not need costly aseptic packaging equipment.
• The moderate cost for this type of operation could be particularly important for promoting soymilk in areas where there is a strong need for a high-protein beverage with only a limited of investment capital.