The pH-shifting process, i.e., unfolding at extreme pH conditions followed by refolding at pH 7, has been used to produce molten globule polypeptides with improved functionality. In the present study, soy protein isolate (SPI) and its components �-conglycinin (7S) and glycinin (11S) were subjected to acid (pH 1.5�3.5) or alkali (pH 10�12) treatments. Preliminary results showed that pH-shifting could induce  substantial increases in protein surface hydrophobicity and complete dissociation of SPI subunits without significant disruption of the secondary structure. These physicochemical changes led to pronounced enhancements in emulsifying activityand solubility. The pH-shifting, notably at pH 12.0, produced soluble, disulfide-linked polymers from 11S which seemed to contribute to emulsion droplet stability. Alkaline pH-shifting treated SPI also spontaneously formed elastic films without heating and had a reduced antagonism with myofibrillar proteins in a composite meat gel system when compared with native SPI.

Formation of stable O/W emulsions and cold-set films by pH-shifting-treated soy proteins is attributed to the dissociation and unfolding of β-conglycinin and glycinin

241st National Meeting (2011)

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