Spectrofluorometric Method for the Determination of Sulfhydryl and Disulfide Groups in Milk Proteins

A spectrofluorometric method has been applied to the determination of sulfhydryl (-SH) and disulfide (-SS-) groups of milk proteins.The method is based on the decrease (quenching) of the fluorescence of fluorescein mercuric acetate (FMA) by -SH, at neutral or basic pH's and by -SSat highly alkaline pit's, which is proportional to the concentration of these groups.FMA produces fluorescence when subjected to excitation by light at 499 mtz which can be measured at 520 m~ by the use of a spectrofluorometer.The method has been tested on model systems consisting of mixtures of reduced (GSH) and oxidized (GSSG) glutathione as well as milk protein systems with and without added known amounts of GSH and GSSG.A high degree of accuracy in the recovery of known ~mounts of -SIt and -SS-was attained from these systems~ proving that the method is highly dependable.