Spectrophotometric Method for Determination of Heat-Activated Sulfhydryl Groups of Skimmilk

Abstract

By suitable modification, adaptation was made of the 5,5′-dithiobis (2-nitrobenzoic acid) reagent method for the spectrophotometric determination of activated sulfhydryl (-SH) groups of heated skimmilk. The modifications consisted of using a nitrogen-purged system, controlling pH, adding ammonium sulfate, filtering, and determining absorbance of the filtrate at 412 mμ. A standard cysteine-HCl curve was prepared in a similar manner. The modified procedure yielded results consistent with other currently used methods. The activation of –SH groups in heated skimmilk, as determined by the modified procedure, followed the kinetics of a first order reaction with reaction rate constants (kmin-1) of 0.078, 0.142, 0.384, and 0.805 for 75, 80, 85, and 90 C, respectively. © 1968, American Dairy Science Association. All rights reserved.