Let's make Soy Milk

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First mentioned on a stone slab of the Eastern Han dynasty in ancient China, soy milk has survived centuries and spread from Asia to Global consumption due to the rising popularity of plant-based alternatives. To produce soymilk, raw materials must be harvested, prepared, and blended with water and desired ingredients, such as flavors and vitamins, in soymilk processing equipment.

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The first steps in soymilk production: from soybeans to okara and jun

Soy is a fairly simple plant to grow; it can thrive in a variety of climates and soils. Once harvested, soybeans are brought to the production plant, cleaned in a grain elevator and dehulled by steaming the hull.

The grain elevator also measures the moisture content of the soybeans, which is typically from 45% to 55%. The clean beans must be soaked or cooked in the enzyme invalidator using high pressure and temperature to eradicate a specific enzyme indigestible for humans.

Ready soybeans are then transferred to grinders for two types of grinding – rough and finer grinding. It is firstly roughly ground with water, however, it requires further grinding as soybeans are still coarse, regardless of being cooked previously. This results in a white slurry that is passed through a large centrifuge pressing the slurry against the surface of a drum that extracts waste (fibers), known as okara, which remains on the outside of the drum, from the liquid forced inside the drum, which, at this point of production, is called jun.

Final production processes and soymilk processing equipment – Jun’s journey

Once okara is extracted from jun, the liquid is boiled in a soymilk cooking machine. The beverage-in-making is then stored in a soymilk storage tank, a mechanism ensuring production quality management. For commercial soymilk, the next step is the addition of sugars, flavors, and vitamins.

In order to disperse flavors properly, all the ingredients are blended, adding them from a smaller tank to raw soymilk in a larger tank. Once sterilized, jun is passed to a homogenizer to break down fat particles and prevent them from separating from the liquid. The temperature then must be decreased to room temperature in the cooling tanks. The final step is aseptic packaging without exposing the product to air.

Soy milk quality: food safety and foam reduction

The quality of soy milk starts with choosing the perfect raw materials: the ideal soybean has a white or colorless hilum. Furthermore, due to the low acid medium, which is the ideal environment for the development of bacteria and germs, the product must be meticulously controlled during the whole production, which in many factories means over 206 quality control checkpoints which entail controlling the temperature of water, steam, and pressure. Additionally, samples are taken every 10 minutes and checked for pH, temperature, and bacterial growth.

Another critical characteristic of high-quality soy milk is the absence of foam. Namely, soy contains a substance called saponin, which tends to foam in addition to protein. A practical solution is the use of defoamers, chemical additives that curb the formation of foam. The most effective defoamers for soy products are based on glycerin fatty acid ester, although defoamers can also be silicone-, water- or oil-based, etc.

Zero waste production – what to do with okara?

As a soybean byproduct, okara is associated with environmental problems due to large quantities of insoluble fiber. However, the industry has found ways to use the waste. Namely, it is used in agriculture as food for cattle and manure. Okara can also be used as a non-gluten flour alternative in baking goods.

In Singapore, scientists found a way to ferment okara and transform it into a tasty, nutritious food ingredient by adding natural microorganisms and enzymes. Furthermore, scientists have recently tried to produce novel biodegradable plastics from soya beans (Glycine max L.) with improved elasticity and plasticity.

The currently available soy plastic is mainly used as disposable food packaging, which is safe for temperatures below zero but sensitive to high temperatures. All in all, the production of soy plastic is less hazardous to the environment and animals than traditional types of plastic.

Methods for elimination of disagreeable soy odor

Soymilk has a specific “beany” odor resulting from the oxidation of specific unsaturated fatty acids by the enzyme lipoxygenase during the seed grinding process. This odor is repulsive for many consumers; therefore, manufacturers are trying to eliminate it as much as possible.

There are several ways to go about it, such as disabling the LOX enzyme with heat by boiling or blanching the beans in hot water. Nevertheless, it is possible to eliminate the odor without a heat treatment by blending soybeans in water free of dissolved oxygen. It is achieved by adding glucose and glucose oxidase to water to consume oxygen.

An environmentally friendly alternative to dairy

It is well-known that plant-based milk alternatives are not consumed exclusively by vegan and lactose-intolerant individuals but also by those aware of the dairy industry’s environmental impact. Making plant-based milk generates about one-third of the greenhouse gases compared to dairy milk, in addition to using far less land and water.

Soymilk especially stands out in this regard as it uses the least amount of water among all plant-based milk alternatives. Namely, 1L of produced soymilk requires 27.7L of water, which is nearly half compared to oat milk and more than 20 times less than dairy. In addition, soymilk performs well in the metric of eutrophication – the pollution of ecosystems with excess nutrients, resulting in the least pollution with 1,06 grams of waste per produced liter.