Electrochemical Coagulation of Soybean Protein; Tofu (Soybean Curd) Production by an Electro-Reaction

Abstract

Effect of direct current on soymilk coagulation was studied to establish a new processing method for food. Soymilk was treated with direct electric current (60 mA) in an anode chamber. The treated soymilk gave tofu-like gel only by simple heating. The obtained tofu-like gel showed appearance and texture similar to a commercial kinu-tofu. Sodium dodecyl sulfate gel electrophoresis showed that the electric treatment did not change the state of covalent cross linkage including disulfide bridges among the soybean protein molecules. Therefore, non-covalent intermolecular interactions may play an important role in the gel network formation. Though the oxidation of the soymilk in the anode chamber cannot be ruled out, the treated soymilk caused almost no change on peroxide value of the oil component, the active chloride content or the oxidationreduction potential. Nor was any mutagenicity observed for the treated soymilk. Therefore, the electric treatment with direct current is considered a safe technique for food processing.

A review of okara (soybean curd residue) utilization as animal feed: Nutritive value and animal performance aspects

“…Soybeans can be processed by these steps: (1) washing; (2) dipping; (3) milling; (4) boiling; (5) filtration; and (6) residue from filtration treated with hot water gives soybean milk and okara. Coagulant is then added to the soybean milk to give tofu and waste water (liquid waste) (Amaha et al, 1996); thus, okara is generated along the process.…”

“…It is a white or yellowish pulp consisting insoluble portion (shell, hull, or husk) of soybean. Furthermore, it has many synonyms, depending on the usage or context, such as soya waste, draff, tofukasu, soy pulp, soybean curd residue, ampas tahu (Malaysian/Indonesian), douzha (Chinese), bejee (Korean), soybean‐curd lees, sapal (Filipino), tempe gembus, or tofu cake (Amaha et al, 1996; Faisal et al, 2016; O'Toole, 1999).…”

“…Grizotto et al (2010) estimated that about 7 metric tons of soymilk and 2 metric tons of okara are generated from 1 metric ton of soybeans. A significant amount of water is needed for tofu processing which results in a greater amount of okara and liquid waste (Amaha et al, 1996). As a result, okara contains a significant amount of water (77.7%), as well as water‐insoluble components (protein, fiber, fat and mineral), which makes it susceptible to spoilage (Harthan & Cherney, 2017; Rahman et al, 2015; Vong & Liu, 2016).…”

Effect of Heat Treatment on Dispersion Stability of Soymilk and Heat Denaturation of Soymilk Protein

“…In particular, soymilk, the emulsion and dispersion consisting mainly of soybean proteins and lipids, is popular not only as a beverage, but also as the main ingredient in tofu (soybean curd) or yuba (sheets of dried soymilk skin). Recently, some soymilk gelation processes not using coagulants have been reported, and further possibilities have been shown for new food materials (Shimoyamada et al, 1999a(Shimoyamada et al, , 1999b(Shimoyamada et al, , 2000(Shimoyamada et al, , 2002Kawase et al, 2000;Kamata et al, 2004). Soybeans contain high levels of proteins and oils, which have excellent nutritional and functional properties.…”

Characterization of Soymilk Prepared from Non-imbibed Soybean Seeds

“…Research on soymilk has been extensive, especially with regard to the effect of heat treatment (Ono et al, 1991;Guo et al, 1997;Shimoyamada et al, 2008), tofu processing (Tezuka et al, 2004;Onodera et al, 2009), yuba processing (Chen et al, 2009), and novel soymilk-derived gel formation (Shimoyamada et al, 1999a(Shimoyamada et al, , 1999bKamata et al, 2004). Soymilk is prepared from imbibed soybean seeds usually soaked in tap water overnight.…”