title: Proposal of mechanism of the freeze-thaw fractionation of 7S and 11S globulins in soymilk.
abstract: The mechanism underlying the freeze-thaw fractionation of 7S and 11S globulins in soymilk was investigated. Freeze-thawed soymilk demonstrated an increased particle size compared with raw soymilk. Further, when defatted raw soymilk was freeze-thawed, it was fractionated into 7S (supernatant) and 11S (precipitate) globulins, similar to what is found with freeze-thaw of raw soymilk. When raw soymilk samples with different ratios of 11S/7S were freeze-thawed, the 11S-deficient variety showed no precipitate. The addition of sodium sulphite or sodium dodecyl sulphate also inhibited precipitate formation after freeze-thawing, resulting in no fractionation. These results suggest that the fractionation is due to selective precipitation of aggregates of 11S globulins and/or 11S globulins and lipid complexes, in which the protein molecules interact through disulphide bonds and/or hydrophobic interactions.
authors.affiliation: Food Research Institute, Toyama Prefectural Agricultural, Forestry and Fisheries Research Center, Yoshioka 360, Toyama 939-8153, Japan. kazuhiro.morita@pref.toyama.lg.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Morita
authors.forename: Makoto
authors.initials: M
authors.lastname: Shimoyamada
mesh_terms: D005590:Fractional Precipitation; D005615:Freezing; D005916:Globulins / Q000737:chemistry* / Q000302:isolation & purification; D010316:Particle Size; D041942:Soy Milk / Q000737:chemistry; D030262:Soybean Proteins / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D005916:Globulins; D030262:Soybean Proteins