Okara (food)

Okara

Filtering okara from a fresh batch of homemade soymilk.
Chinese name
Chinese 豆渣 / 豆腐渣
Japanese name
Kanji 雪花菜 / 御殻
Kana おから
Korean name
Hangul 비지 / 콩비지

Okara, soy pulp, or tofu dregs is a pulp consisting of insoluble parts of the soybean which remains after pureed soybeans are filtered in the production of soy milk and tofu. It is generally white or yellowish in color. It is part of the traditional cuisines of Japan, Korea, and China, and since the 20th century has also been used in the vegetarian cuisines of Western nations.

It is called dòuzhā or dòufuzhā in Chinese, okara in Japanese, and biji or kongbiji in Korean.

Okara is the oldest of three basic types of soy fiber. The other two are soy bran (finely ground soybean hulls), and soy cotyledon/isolate fiber (the fiber that remains after making isolated soy protein, also called "soy protein isolate").

Production

Okara is a food by-product from tofu and soy milk production.[1]:9 In 1983 it was estimated that the annual yield for okara in Japan was approximately 70,000 metric tons.[2]:380

Due to its high moisture and nutrient content, okara is highly prone to putrefaction,[2]:380 and this has limited its commercial use.[3]:5

Composition

Okara that is firmly packed consists of 3.5 to 4.0% protein, 76 to 80% moisture and 20 to 24% of solids. When moisture free, the gritty okara contains 8 to 15% fats, 12 to 14.5% crude fiber and 24% protein, and contains 17% of the protein from the source soybeans. It also contains potassium, calcium, niacin.[1]:151[4]:168 Most of the soybean isoflavones are left in okara, as well as vitamin B and the fat-soluble nutritional factors, which include soy lecithin, linoleic acid, linolenic acid, phytosterols, tocopherol, and vitamin D.[5] Okara contains some antinutritional factors: trypsin inhibitors (mostly destroyed by cooking), saponins, and hemagglutinin, which cannot be easily digested. Fermentation (by proper species of bacteria) of okara is not only conducive to digestion and absorption of okara nutrients, but also further improves the nutritional value. It can eliminate the bean’s sense of smell, increase the amount of edible fiber, free amino acids, sugars, fatty acids, vitamin B12, vitamin B2, and flavoprotein.[5]

Uses

Most okara worldwide is used as feed for livestock - especially hogs and dairy cows. Most of the rest is used as a natural fertilizer or compost, which is fairly rich in nitrogen. A small amount is used in cookery.[3]:3–4

Human consumption

While relatively flavourless when eaten on its own, it can be used in stews such as the Korean biji-jjigae or in porridges.[6] It's also used as an addition to baked goods such as breads, cookies and muffins, and can serve to create a crumbly texture in these foods.[4]:168

In Japan it is used in a side dish called unohana which consists of okara cooked with soy sauce, mirin, sliced carrots, burdock root and shiitake mushrooms.[7]

Okara can be used to make tempeh, by fermenting with the fungus Rhizopus oligosporus,[4]:168 using a tempeh starter,[8] or to make presscake tempehs that use ingredients such as brown rice, bulgur wheat, soybeans and other legume and grain combinations.[9]

Okara is also eaten in the Shandong cuisine of eastern China by steaming a wet mixture of okara that has been formed into blocks of zha doufu also known as xiao doufu or cai doufu.[10]:172

The product is sometimes used as an ingredient in vegetarian burger patties. Additional uses include processing into a granola product, as an ingredient in soysage and as an ingredient in pâtés.[4]:168

Livestock consumption

Most okara is used as animal feed, especially for farms in vicinity of soy milk or tofu factories.[3][4]:168

In pet food

The product is also used as an ingredient in pet foods.[4]:168

As fertilizer or compost

Okara is sometimes spread on fields as a natural nitrogen fertilizer. It also adds tilth to the soil. Likewise, it can be added to compost to add organic nutrients and nitrogen.[4]:168

Waste/Environment

When not considered foodstuff, it may be deemed soybean curd residue (SCR). Some 800,000 tons of soybean curd residue is disposed annually as tofu production byproducts, just in Japan. As mass waste, it is a potential environmental problem because it is highly susceptible to putrefaction.[5] The protein in SCR is of better quality than from other soy products; for example, the protein efficiency ratio of SCR is 2.71 compared with 2.11 for soymilk, but the ratio of essential amino acids to total amino acids is similar to tofu and soymilk.[5] Nevertheless, it remains a challenge to current processes to commercially extract the proteins and nutrients from SCR waste.

See also

References

  1. 1 2 David B. Haytowitz and Ruth H. Matthews for the USDA Human Nutrition Information Service December 1986 Agriculture Handbook No. 8-16. Composition of Foods: Lugumes and Legume Products.
  2. 1 2 Applewhite, Thomas H. (editor) (1989). Proceedings of the World Congress on Vegetable Protein Utilization in Human Food and Animal Foodstuffs. The American Oil Chemists Society. ISBN 093531525X
  3. 1 2 3 Soy20/20. Spring 2005 Okara: Overview of Current Utilization
  4. 1 2 3 4 5 6 7 Shurtleff, William; Aoyagi, Akiko (1979). Tofu & Soymilk Production. Volume 2: The Book of Tofu. ISBN 1928914047
  5. 1 2 3 4 Li, Shuhong; Zhu, Dan; Li, Kejuan; Yang, Yingnan; Lei, Zhongfang; Zhang, Zhenya (8 September 2013). "Soybean Curd Residue: Composition, Utilization, and Related Limiting Factors". ISRN Industrial Engineering. 2013: 1–8. doi:10.1155/2013/423590.
  6. ↑ Claire Lee for the Star (Malaysia) 24 December 2013 Revisiting the mystique of Silla in Gyeongju
  7. ↑ Robbie Seinnerton for Japan Times. 20 October 2002 The garden of heavenly tofu delights
  8. ↑ (staff editors) (September–October 1977). "How We Make and Eat Tempeh Down on The Farm". Mother Earth News. p. 4. Retrieved March 11, 2013.
  9. ↑ Shurtleff, William; Aoyagi, Akiko (1979) The Book of Tempeh. Soyinfo Center. p. 114. ISBN 0060140097
  10. ↑ KeShun Liu. "Oriental Soyfoods". Chapter 6 in Asian Foods: Science and Technology, eds. Catharina Y.W. Ang, et al. CRC Press (April 5, 1999) ISBN 978-1566767361
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