Soy milk

A glass of soy milk.

Soy milk (also called soya milk, soymilk, soybean milk, or soy juice and sometimes referred to as soy drink/beverage) is a beverage made from soybeans. A traditional staple of Asian cuisine, it is a stable emulsion of oil, water, and protein. It is produced by soaking dry soybeans and grinding them with water. Soy milk contains about the same proportion of protein as cow's milk: around 3.5%; also 2% fat, 2.9% carbohydrate, and 0.5% ash. Soy milk can be made at home with traditional kitchen tools or with a soy milk machine. Despite the terminology used by consumers, it is illegal to sell soy milk under that name in the European Union, where - with certain exceptions - EC Regulation (1898/87) has restricted the term 'milk' to mammary secretions since 1987; in such countries the term 'soy drink' is commonly used.

The coagulated protein from soy milk can be made into tofu, just as dairy milk can be made into cheese.

Origins

The oldest evidence of soy milk production is from China where a kitchen scene proving use of soy milk is incised on a stone slab dated around AD 25–220. It also appeared in a chapter called Four Taboos (Szu-Hui) in the AD 82 book called Lunheng by Wang Chong, possibly the first written record of soy milk. Evidence of soy milk is rare prior to the 20th century and widespread usage before then is unlikely.

According to popular tradition in China, soy milk was developed by Liu An for medicinal purposes, although there is no historical evidence for this legend. This legend first appeared in the 12th century and was not clearly stated until late 15th century in Bencao Gangmu, where the development of tofu was attributed to Liu with no mention of soy milk. Later writers in Asia and the West additionally attributed development of soy milk to Liu An, assuming that he could not have made tofu without making soy milk. This may be incorrect. In addition, some recent writers claim Liu An developed tofu in 164 BC.

Prevalence

Greek Café Frappé prepared with soy milk, topped with additional cinnamon

A packet of Melon-flavored soy drinks.

Plain soy milk is unsweetened, although some soy milk products are sweetened. Salted soy milk is also consumed in China.

The drink is very popular in the hawker culture of Malaysia and many other Southeast Asian countries, with it being a standard offering accompanying meals at Malaysian Chinese stalls. In Malaysia, soybean milk is usually flavoured with either white or brown sugar syrup. The consumer also has the option to add grass jelly, known as leong fan or "cincau" (in the Malay language, adopted from the Chinese equivalents) to the beverage. Sellers of soybean milk in Penang usually also offer bean curd, a related custard-like dessert, known to the locals as tau hua which is flavored with the same syrup as the soybean milk. In Indonesian it is known as "susu kedele". In Vietnam, the soymilk as well as the soy custard may be flavored with ginger or pandan, a grassy herb with a mild coconut-like flavor. More recently (since 2008), other optional additions to soymilk have become popular among street vendors and drink stalls around Southeast Asia, including tapioca pearl, sweetened red bean, honey, and black tea.

Yeo's, a drink manufacturer in Singapore and Malaysia, markets a commercialized tinned or boxed version of soybean milk.

The drink is slowly becoming popular in India as well, where it widely sold in Tetrapaks by various brands like Staeta.

In the West, soymilk has become a popular alternative to cow's milk, with a roughly similar protein and fat content. Soy milk is commonly available in vanilla and chocolate flavors as well as its original unflavored form. In some Western countries where veganism has made inroads, it is available upon request at cafés and coffee franchises as a cow's milk substitute.

Health and nutrition

Soymilk, original, unfortified

Nutritional value per 100 g (3.5 oz)
Energy	226 kJ (54 kcal)
Carbohydrates	6.28 g
- Sugars	3.99 g
- Dietary fiber	0.6 g
Fat	1.75 g
- saturated	0.205 g
- monounsaturated	0.401 g
- polyunsaturated	0.961 g
Protein	3.27 g
- Tryptophan	0.038 g
- Threonine	0.108 g
- Isoleucine	0.114 g
- Leucine	0.186 g
- Lysine	0.131 g
- Methionine	0.027 g
- Cystine	0.000 g
- Phenylalanine	0.113 g
- Tyrosine	0.089 g
- Valine	0.117 g
- Arginine	0.187 g
- Histidine	0.061 g
- Alanine	0.104 g
- Aspartic acid	0.288 g
- Glutamic acid	0.487 g
- Glycine	0.193 g
- Proline	0.147 g
- Serine	0.149 g
Water	88.05 g
Thiamine (vit. B1)	0.060 mg (5%)
Riboflavin (vit. B2)	0.069 mg (6%)
Niacin (vit. B3)	0.513 mg (3%)
Pantothenic acid (B5)	0.373 mg (7%)
Vitamin B6	0.077 mg (6%)
Folate (vit. B9)	18 μg (5%)
Vitamin E	0.11 mg (1%)
Calcium	25 mg (3%)
Iron	0.64 mg (5%)
Magnesium	25 mg (7%)
Manganese	0.223 mg (11%)
Phosphorus	52 mg (7%)
Potassium	118 mg (3%)
Sodium	51 mg (3%)
Zinc	0.12 mg (1%)
Percentages are relative to US recommendations for adults. Source: USDA Nutrient Database

Soy milk has about the same amount of protein as cow's milk, though the amino acid profile differs. Natural soy milk contains little digestible calcium as it is bound to the bean's pulp, which is indigestible by humans. To counter this, many manufacturers enrich their products with calcium carbonate available to human digestion. Unlike cow's milk, it has little saturated fat and no cholesterol.

Soy products contain sucrose as the basic disaccharide, which breaks down into glucose and fructose. Since soy doesn't 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 a good alternative for lactose-intolerant people. For patients without conditions that limit which sugars they can consume, there is no evidence to support any sugar-related health benefit or detriment to consuming soy milk instead of cow's milk.

The American Academy of Pediatrics considers soy milk a suitable alternative for children who cannot tolerate human or cow's milk, or whose parents opt for a vegan diet.

Soy milk, like cow's milk, varies in fat content, but the most commonly sold varieties have less fat than whole milk, similar fat content to 2% milk, and more fat than skim/nonfat milk.

Though it has been suggested that soy consumption is associated with a reduction in low-density lipoprotein ("bad cholesterol") and triglycerides, a 2006 study of a decade of soy protein consumption found no association between soy intake and health benefits such as cardiovascular health or cancer rates, and no benefit for women undergoing menopause. Soy was able to replace animal protein, foods high in saturated fats, and other sources of dietary fiber, vitamins and minerals. However, much of the mineral content in soy milk is unassimilable because of high content of phytic acid in soy milk. If soy milk is made into tempeh, the phytic acid content is cut in half.

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, purine in soy can make the condition worse. The U.S. National Institutes of Health (NIH) recommends gout sufferers limit consumption of soy products (although also suggesting that soy may have health benefits by reducing the risk for heart disease).

Preparation

Package and glass of Malaysian soy milk

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 profound 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. The pancreas naturally secretes proteases to digest a protein meal. Eating raw soybeans on a regular basis causes the pancreas to hypersecrete, leading to benign tumors of the pancreas.

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. It is 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, NY led to the discovery that paint-like, off-flavors of traditional soy milk can be prevented from forming by a rapid hydration 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 bland soy milks have been heat treated in this manner to destroy LOX.

In 1969, Mattick and Hand at Cornell University made the important discovery 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) important for 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. An example of a triple LOX-free soybean is the American soybean named "Laura".

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 milk 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 pounds) of food in dry matter (DM) basis and 90 to 180 litres (25 to 50 gallons) 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.

In Brazil, the explosion of soybean cultivation has led to losing large tracts of forest land leading to ecological damage. These particular cleared forests are planted with soy intended for animal agricultural enterprises (especially beef and pork production), not for human consumption.

The American soil scientist Dr. Andrew McClung was the first to devise a method to grow soybeans in the Cerrado region of Brazil (tropical savanna). He was awarded with the 2006 World Food Prize.

See also

• Hemp milk
• Chinese cuisine
• Dairy (animal) milk
• Douzhi
• Plant milk
• Soy milk maker
• Tofu (soy milk curd)

References

• 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. "Soy Milk". Soya.be. Soya. Retrieved August 17, 2005. 
• 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 (1979). Tofu & Soymilk Production. Lafayette, California: New-Age Foods Study Center.
• 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: Detailed information on 3,120 published documents (extensively annotated bibliography), 968 commercial soymilk products, 506 original interviews (many full text) and overviews, 462 unpublished archival documents. 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

• Cornell University Food and Brand Lab
• Soy Allergy Information Page Asthma and Allergy Foundation of America