Gamma Irradiation Effect on the Sulfhydryls Content of Skimmilk Powder

Abstract

Abstract The effect of gamma-irradiation of skimmilk powder on the sulfur-containing constituents that may contribute to flavor defects when the powder is recombined with water, was investigated. Before irradiation no free –SH groups were detected in the laboratory prepared powders but they were present (18.5 mm/ lOOg) in the commercial high heat powder studied. After the application of irradiation doses of 0.4, 0.8, 1.2 and 1.6 Mrads the percentage increase in the –SH groups of the laboratory produced powder was 15.3 to 69.2 for free, 6.4 to 9.3 for masked and 6.4 to 29.3 for total sulfhydryl groups. The corresponding results for the commercial powder were 2 to 20 for free, 7.3 to 9.4 for masked and 12.8 to 32.3 for total –SH groups. The addition of ascorbic acid to the liquid skimmilk which after drying, amounted to 2.7 to 23.8 mm/100 of powder was reflected in a 2.4 to 16.5% decrease in total –SH groups when an irradiation dose of 0.4 Mrads was applied. Ascorbyl palmitate added under the same conditions and concentrations decreased the total –SH groups by 3.5 to 29.9%. Similar protection of the powder was obtained when the irradiation dose was 1.6 Mrads. The irradiation of skimmilk powder containing labelled 14 Ci-ascorbic acid revealed degradation products which could be recovered as carbonyls.