Soy milk

Soy milk

Origin
Alternative name(s)	Soya milk 豆漿 or 豆奶 (Chinese: bean thick liquid, or bean milk) 豆乳 (Japanese) 두유 or 豆乳 (Korean) Sua Dau Nanh (Vietnam)
Place of origin	China
Details
Approximate calories per serving	33

Soy milk, also referred to as soymilk or soya milk, is a plant milk produced by soaking dried soybeans and grinding them in water.

A traditional staple of East Asian cuisine, soy milk is a stable emulsion of oil, water and protein. Soy milk can be produced at home using a soy milk machine.

History

Soymilk (豆浆, doujiang) originated in China, probably during the early Han dynasty (202 BCE to 9 CE), after the rotary millstone was introduced and became widely used to grind wheat. It did not become widely used in China until the 1800s, when it was discovered that extended heating made it taste better and easier to digest.

Soymilk was introduced to the US market by Vitasoy in 1979; the first domestic manufacturer of soymilk was Sunrich Food Group, which introduced its products in 1985.

Name variations

There is a certain amount of confusion prevalent when it comes to beverages named soy beverage, soy drink or soy milk respectively. This is caused by several factors:

• The agricultural traditions or laws in many countries require that only milks sourced from certain lactating animals are legally allowed to be named milk when sold commercially, often only cow's milk is allowed to be named milk on the packaging, and any other milks must state the name of the respective animal (goat milk, sheep milk etc.). This leads the manufacturers of plant milks to name their products beverage or drink instead, invent fantasy based names, or omit the name entirely in favor of descriptive packaging.
• In some countries soy milk has been named soy bean beverage or soy drink for centuries, and the native population may not respond well to Western influence over the naming of their own traditional heritage foods. Therefore, a preference or competition of soy drinks versus soy milks may exist.
• In countries where traditional soy based beverages have existed for a long time, and are named beverage or drink, and yet also new, often more expensive and seemingly higher quality, and therefore sought after, types of foreign soy beverages named milk are imported, the manufacturers of the suddenly less popular drinks may claim that their products would be the only ones with certain nutritional or dietetic benefits, to increase their marketability (lower in fat, higher in nutrients etc.). However both types are just the same milky type soy bean based beverages, only produced, filtered and packaged in slightly different ways (as all of them have a milky look and taste, and are made almost entirely of soy beans and water), so each type can have the same benefits or disadvantages. It depends on the preferences of the customer to choose the favorite type, after comparing the pricing, reading the nutritional information on the packaging, and tasting of samples, as any type of well made soy beverage, soy drink or soy milk can be very healthy, nutritious and delicious.
• Due to worldwide market globalisation different types of soy beverages, soy drinks and soy milks may be available to consumers in a country, without enough background information being available at the same time, or lower educational levels of the population leading to misunderstandings, which can contribute to confusion, and different urban legends or popular word of mouth tales replacing the actual facts and information.

Health and nutrition

Latte macchiato prepared with soy milk, topped with additional cinnamon

File:Melon-flavored soy drink.jpg

A packet of Melon-flavored soy drinks.

Soy milk in a can

Nutritional content of cows', soy and almond milk
	Cows' milk (whole, vitamin D added)	Soy milk (unsweetened; calcium, vitamins A and D added)	Almond milk (unsweetened)
Calories (cup, 243 g)	149	80	40
Protein (g)	7.69	6.95	1
Fat (g)	7.93	3.91	2.5
Saturated fat (g)	4.55	0.5	0
Carbohydrate (g)	11.71	4.23	2
Fibre (g)	0	1.2	1
Sugars (g)	12.32	1	0
Calcium (mg)	276	301	n/a
Potassium (mg)	322	292	170
Sodium (mg)	105	90	180
Vitamin B12 (µg)	1.10	2.70	n/a
Vitamin A (IU)	395	503	n/a
Vitamin D (IU)	124	119	n/a
Cholesterol (mg)	24	0	0

Soy milk is a complete protein and has about the same amount of protein as cow's milk; it can replace animal protein and other sources of dietary fiber, vitamins and minerals. Soy milk contains little digestible calcium because calcium is bound to the bean's pulp, which is indigestible by humans. To counter this, manufacturers enrich their products with calcium carbonate. Unlike cow's milk, soy milk has little saturated fat and no cholesterol.

Soy products contain sucrose as the basic disaccharide, which breaks down into glucose and fructose. Since soy does not contain galactose, a product of lactose breakdown, soy-based infant formulas can safely replace breast milk in children with galactosemia. Like lactose-free cow's milk, soymilk contains no lactose, which makes it an alternative for those who are lactose-intolerant.

It has been suggested that soy consumption is associated with a reduction in low-density lipoprotein ("bad cholesterol") and triglycerides. Research has refuted claims that soy affects bone mineral density. Research has found no link between soy and increased estrogen levels in men, although studies thus far have been limited in duration.

For people who suffer from gout, moderate consumption of soy, which is rich in purine, is not associated with the development of gout, but high levels should be avoided.

Preparation

Soy milk can be made from whole soybeans or full-fat soy flour. The dry beans are soaked in water overnight or for a minimum of 3 hours or more depending on the temperature of the water. The rehydrated beans then undergo wet grinding with enough added water to give the desired solids content to the final product. The ratio of water to beans on a weight basis should be about 10:1. The resulting slurry or purée is brought to a boil in order to improve its nutritional value by heat inactivating soybean trypsin inhibitor, improve its flavor and to sterilize the product. Heating at or near the boiling point is continued for a period of time, 15–20 minutes, followed by the removal of an insoluble residue (soy pulp fiber or okara) by filtration.

There is a simple yet important difference between traditional Chinese and Japanese soy milk processing: the Chinese method boils the filtrate (soy milk) after a cold filtration, while the Japanese method boils the slurry first, followed by hot filtration of the slurry. The latter method results in a higher yield of soy milk but requires the use of an anti-foaming agent or natural defoamer during the boiling step. Bringing filtered soy milk to a boil avoids the problem of foaming. It is generally opaque, white or off-white in color, and approximately the same consistency as cow's milk.

For all raw soybean protein products, heat is necessary to destroy the activity of the protease inhibitors naturally present in the soybean.

When soybeans absorb water, the endogenous enzyme, Lipoxygenase (LOX), EC 1.13.11.12 linoleate:oxidoreductase, catalyzes a reaction between polyunsaturated fatty acids and oxygen {hydroperoxidation}. LOX initiates the formation of free radicals, which can then attack other cell components. Soybean seeds are the richest known sources of LOXs, which are thought to be a defensive mechanism by the soybean against fungal invasion.

In 1967, experiments at Cornell University and the New York State Agricultural Experiment Station at Geneva, New York led to the discovery that paint-like, off-flavors of traditional soy milk can be prevented by a rapid hydration and grinding process of dehulled beans at temperatures above 80 °C. The quick moist heat treatment inactivates the LOX enzyme before it can have a significant negative effect on flavor. All modern soy milks have been heat treated in this manner to destroy LOX.

In 1969, Mattick and Hand at Cornell University discovered that most of the so-called beany flavor in soybeans was not inherent in the beans themselves but was produced by the enzyme lipoxygenase when the split beans came in contact with water. Lipoxygenase could be inactivated and most of the beany flavor removed by either dropping unsoaked soybeans directly into boiling water or by removing any cracked or split beans prior to soaking, then carefully dropping the soaked beans into boiling water.

Normal mature soybeans actually contain three LOX isozymes (SBL-1, SBL-2, and SBL-3) that influence undesirable flavor development. One or more of these isozymes have recently (1998) been removed genetically from soybeans yielding soy milk with less cooked beany aroma and flavor and less astringency.

The University of Illinois has developed a soy milk that makes use of the entire soybean. What would normally constitute "insolubles" are ground so small by homogenization as to be in permanent suspension.

Cooking

A bowl of soy milk soup seasoned with salt and vinegar, with vegetables and wonton dumplings.

Bottled soy milk as sold in Thailand

Soy milk is found in many vegan and vegetarian food products and can be used as a replacement for cow's milk in many recipes.

"Sweet" and "salty" soy milk are both traditional Chinese breakfast foods, served either hot or cold, usually accompanied by breads like mantou (steamed rolls), youtiao (deep-fried dough), and shaobing (sesame flatbread). The soy beverage is typically sweetened by adding cane sugar or, sometimes, simple syrup. "Salty" soy milk is made with a combination of chopped pickled mustard greens, dried shrimp and, for curdling, vinegar, garnished with youtiao croutons, chopped scallion (spring onions), cilantro (coriander), meat floss (肉鬆; ròusōng), or shallot as well as sesame oil, soy sauce, chili oil or salt to taste.

Soy milk is used in many kinds of Japanese cuisine, such as in making yuba as well as sometimes a base soup for nabemono.

In Korean cuisine, soy milk is used as a soup for making kongguksu, cold noodle soup eaten mostly in summer.

Tofu is produced from soy milk by further steps of curdling and then draining.

Soy milk is also used in making soy yogurt, soy cream, soy kefir and soy based cheese analogues.

Ecological impact

Using soybeans to make milk instead of raising cows may be ecologically advantageous, because the amount of soy that could be grown using the same amount of land would feed more people than if used to raise cows. Cows require much more energy in order to produce milk, since the farmer must feed the animal, which can consume up to 24 kilograms (53 lb) of food in dry matter (DM) basis and 90 to 180 litres (24 to 48 US gal) of water a day, producing an average of 40 kilograms of milk a day. Because the soybean plant is a legume, it also replenishes the nitrogen content of the soil in which it is grown.

The cultivation of soybeans in South America has been cited as a cause of deforestation and a range of other large-scale, negative, environmental effects. However the majority of soybean crops worldwide are used as animal feed, especially in South America where cattle farming is widely prevalent, and were thus never intended for soy milk production, but from the start meant to be sold as the more lucrative livestock fodder.

See also

• List of soy-based foods
• Milk substitute
• Plant milk
• Soy milk maker
• Soy yogurt
• Tofu (soy milk curd)
• Tofu skin

Further reading

• Rahab Waweru, M.A., et al. 1967. Effect of processing methods on oxidative off-flavors of soybean milk. Cereal and Food Sciences North Nairobi State University, Ministry of Agriculture.
• Torres-Penaranda, A.V., et al.1998. Sensory characteristics of soymilk and tofu made from Lipoxygenase-Free and Normal soybeans. Journal of Food Science 63 (6): 1084-1087.
• Smith, A.K. and Circle, S.J. 1972. Soybeans: Chemistry and Technology. AVI publishing.
• Calvert, John (2000). Soymilk Microenterprise: A Treatise on Small-Scale Soymilk Production
• William Shurtleff and Akiko Aoyagi (2000). Tofu & Soymilk Production. 3rd edition. Lafayette, California: Soyfoods Center. ISBN 0-933332-72-6.
• William Shurtleff and Akiko Aoyagi (1994). Soymilk and soymilk products - Bibliography and sourcebook, 1500 to 1993: Lafayette, California: Soyfoods Center. ISBN 0-933332-84-X.
• Liu, KeShun.1997. Soybeans: Chemistry, Technology, and Utilization. Chapman & Hall.
• Ang, Catharina Y. W., KeShun Liu, and Yao-Wen Huang, eds. (1999). Asian Foods: Science & Technology. Lancaster, Pennsylvania: Technomic Publishing Co.
• Berk, Zeki. Technology of production of edible flours and protein products from soybeans. FAO (UN). 1992.
• Frank M. Sacks MD, et a. (2006) Soy Protein, Isoflavones, and Cardiovascular Health. An American Heart Association Science Advisory for Professionals From the Nutrition Committee in Circulation.

External links

• Soy Allergy Information Page Asthma and Allergy Foundation of America