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IRRADIATION-INDUCED CHANGES IN MILK FAT

Journal Article · · Journal of Dairy Science (U.S.)
Milk fat irradiated under reduced pressure exhibits a flavor atypical of that encountered through autoxidation, with a candle-like flavor component predominant. Apparently, this flavor is attributable to hydroperoxides. Investigations were undertaken to describe this flavor and other changes effected by irradiation. When milk fat under reduced ntmospheric pressure was exposed to 1.5 to 4.5 Mrad Co/sup 60/ gamma irradiation, free monocarbonyls were produced at a rate proportional to dose. The 2-thiobarbituric acid number and total carbonyls increased, but not at a linear rate. Small quantities of hydroperoxides were produced; radiation dosages higher than 1.5 Mrad decreased the concentration. The flavor of the irradiated fat appeared to have three components: hydrolytic rancidity, oxidized, and candle-like. The monocarbonyls of irradiated fat were isolated and analyzed by gas chromatography and as 2,4- dinitrophenylhydrazine derivatives. Alkanals predominated and their order of decreasing concentration in the irradiated fat was: C/sub 16/, C/sub 15/, C/sub 14/, C/sub 12/ , C/sub 10/, C/sub 6/, C/sub 8/, C/sub 7/, C/sub 4/, iso-C/sub 4/, C/sub 9/, C/sub 5/, C/sub 3/, C/sub 2/, C/sub 1/. Methyl ketones also were produced by irradiation and the following compounds were found: C/sub 15/, C/sub 11/, C/sub 9/, C/sub 7/, C/sub 5/, C/sub 4/. Evidence is presented indicating that the long-chain aldehydes are responsible for the candle-like defect. It is suggested that the long-chain aldehydes and methyl ketones are produced via hydrolytic rather than oxidative mechanisms. At a dose of 3.0 Mrad, most of the carotenoids in the fat were destroyed, as evidenced by the bleached appearance of the fat. Although the fat was sealed under reduced pressure, irradiation caused production of gaseous materials, as seen by bulging of the cans. (BBB)
Research Organization:
Oregon State Univ., Corvallis
Sponsoring Organization:
USDOE
NSA Number:
NSA-18-015848
OSTI ID:
4073113
Journal Information:
Journal of Dairy Science (U.S.), Journal Name: Journal of Dairy Science (U.S.) Vol. Vol: 46; ISSN JDSCA
Country of Publication:
Country unknown/Code not available
Language:
English