Cereal Chem 47:687 - 695.  |  VIEW ARTICLE
Mechanisms of Protein Insolubilization During the Drying of Soy Milk. Role of Disulfide and Hydrophobic Bonds.

D. Fukushima and J. Van Buren. Copyright 1970 by the American Association of Cereal Chemists, Inc. 

Quantitative studies of the insolubilization of soy milk (SM) during drying showed that polymerization took place through disulfide bonds, as indicated by the effects of sulfhydryl-blocking agents, and through hydrophobic bonds, as indicated by the effect of sodium dodecyl sulfate. SM (7% solids) had 2 to 3 x 10(- 4)M active free sulfhydryl (SH) groups exposed on the surface of the molecules after a short heating time, and these took part in polymerizations during the drying set leading to insolubilization of 35% of the total SM proteins. However, these exposed active SH groups could be inactivated by prolonged heating before drying, perhaps by the oxygen dissolved in the soy milk. On the other hand, the amounts of the proteins insolubilized through hydrophobic bonds increased evenly with the heating time before drying and reached a plateau where 40 to 50% of the total proteins were insolubilized through the hydrophobic bonds. Most of the experimental findings concerning the redispersibility of dried SM proteins could be reasonably explained through these mechanisms.