Flavor and Odor Defects of Gamma-Irradiated Skimmilk. I. Preliminary Observations and the Role of Volatile Carbonyl Compounds

Open Access
Publisher Website
Google Scholar
Abstract
Studies of skimmilk and its''fractions after gamma irradiation at 2x106 and 5 x 106 rep. revealed fragmentation and aggregation of proteins, activation of sulphydryl groups, lowering of pH, increases in titratable acidity, browning, flavor and odor defects. All changes were intensified at the 5 x 106 rep. dosage. Irradiated skimmilk was described organoleptically as malty and caramel-like at the 2 x 106 rep. dosage whereas a putrid, burnt-protein type odor was detectable at the 5 x 106 rep. dosage. Studies of irradiated skimmilk fractions revealed the serum fraction as the source of the malty, caramel-like defect; the protein fraction as the putrid, burnt-protein defect while irradiated lactose solutions were sour but had no odor. The odor of irradiated sodium caseinate sols were practically identical to that of irradiated skimmilk proteins indicating casein as a major precursor. Volatile carbonyls of irradiated skim milk were identified as 2,4-dinitrophenylhydrazone derivatives by paper chromatography, melting points, and UV spectra. Formaldehyde, acetaldehyde, n-hexanal, acetone, and butanone were identified, acetalde-hyde, n-hexanal, acetone, and butanone were identified. Acetaldehyde was considered of significance to the malty defect.