The Effect of Holder and Flash Pasteurization on some Flavors of Milk. I. The Effect on Miscellaneous Flavors Common to Commercial Raw Milk

Abstract

Summary Samples of milk from each of ten producers were secured weekly over a six-month period, divided into lots, were holder pasteurized with and without aeration at 143° F. for 30 minutes and flash pasteurized at 160° F. for 15 seconds. The samples were scored and rescored “blind” at the first and third days of storage by two judges working independently. The predominating off flavor in the day-old, raw control samples was feed, the percentage frequency of which was materially decreased by pasteurization. The predominating off flavor of unaerated and aerated holder pasteurized day-old milk was heated. Less heated flavors were noted in the flash pasteurized samples than in the holder pasteurized samples. Flash pasteurized milk showed not only a higher percentage of observations of excellent flavor milk, score of 23, than were noted in the raw control or in the holder pasteurized samples but greater stability of excellent flavor upon storage as well. No significant difference was found between the mean scores of milk holder pasteurized with aeration or similar pasteurization without aeration and that of the raw samples at the first day of storage. However, the increase in score of the pasteurized samples over the raw samples at three days of storage was significant. Storing the milk for three days at 40° F. resulted in a significant decrease in the score over that noted at one day of storage. Raw milk scores decreased a mean of 0.91 points as a result of storage, whereas, the decrease in score of the pasteurized milk ranged from 0.43 to 0.55 points. The pasteurization processes increased the frequency of heated, oxidized, cooked, and old flavors and decreased the frequency of feed, high acid, flat, salty, cowy, rancid, unclean, and off but unidentified flavors. Storage of the milk at 40° F. for three days increased the frequency of high acid, old, oxidized, unclean, and rancid flavors in the raw samples and the oxidized and old flavors in the pasteurized samples, whereas, similar storage decreased the percentage incidence of feed, cowy, flat, heated, cooked, and off but unidentified flavors. The mean score of the raw milk of all patrons decreased steadily from January through June. A gradual increase in the incidence of feed flavors was found in the raw samples from January to June. During the same period of time there was noted a rather constant frequency of oxidized flavors in the samples of the pasteurized milk, until May when the per cent frequency decreased markedly. As the frequency of feed flavors increased a very similar decrease in the occurrence of the oxidized flavors was noted. The two judges varied slightly in rescoring ability, the one judge rescoring 42.0 per cent of the samples identically with the first score, whereas, the other judge rescored 54.3 per cent of the samples identically with the first score. Both judges, working independently, scored 39 per cent of all the samples with the same score.