Sulfhydryl analysis: I. Determination of free sulfhydryls in wheat-flour doughs

Methodology was developed for the determination of free sulfhydryls in wheat flours and doughs using NBD-Cl (7-chloro-4-nitrobenzo-2-oxa-1,3-diazole). The solubilization of protein by sonication in sodium dodecyl sulfate (SDS) was compared to proteolysis with Proteinase K in SDS. Oxidation during proteolysis and disulfide cleavage during sonication are the likely reasons for observed differences between the two solubilization methods. The sulfhydryl determination and both extraction procedures work effectively on model doughs and full bread formula.