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Michigan Agricultural Experiment Station, East Lansing, Michigan
ABSTRACT
Thirty gallons of cream, averaging throughout the year 52.5 per cent fat, were processed and stored at –10° F. monthly for a 12-month period. Flavor examinations were made at 3-, 6-, 12-, and 24-months' storage. Possible flavor-affecting factors studied were: temperature of pasteurization, copper contamination, homogenization, addition of sucrose, type of container, season of the year, length of storage, initial titratable acidity and hydrogen-ion concentration. The studies involved approximately 3,700 flavor examinations and judgments by each of two experienced judges.
Fresh, high-quality cream, pasteurized at 165° F. for 15 minutes or at 185° F. for 5 minutes withstood –10° F. storage for 3, 6, or 12 months without appreciable development of the oxidized flavor. The temperature of 185° F. for 5 minutes resulted in a slightly superior keeping quality of the cream, particularly at 24 months' storage, than did the temperature of 165° F. for 15 minutes. The pasteurization temperature of 150° F. for 30 minutes was inadequate for stabilizing the flavor of the cream upon storage.
When 1 ppm. copper was added to the cream following pasteurization, the cream invariably became oxidized even upon 3-months' storage regardless of the temperature of pasteurization. Homogenization, at 3,000 pounds pressure, although slightly beneficial, did not prevent the development of copper-induced oxidation upon storage when 1 ppm. copper was added to the cream. Homogenization, however, was beneficial in retarding spontaneous oxidation when the cream was pasteurized at 150° F. for 30 minutes. When high-quality cream, produced and handled away from copper contamination was adequately pasteurized, further advantage so far as stability of flavor upon storage was concerned was not secured by homogenization.
The addition of 10 per cent sucrose appeared to have little effect upon the flavor of stored cream. When 1 ppm. copper and 10-per cent sugar were both present in the cream the oxidized flavor developed was less intense than when copper only was present. However, this was attributed to the masking effect of the sugar.
The type of container, glass, paper, or tin had little influence upon the flavor of the cream during storage, particularly when the cream was pasteurized at 165° F. for 15 minutes or at 185° F. for 5 minutes.
Despite a wide range in the seasonal carotenoid content of cream, cream produced during one season of the year was stored as satisfactorily as that produced at another season.
The length of the storage period of cream assumes less importance when the cream stored is of high quality, free of copper contamination and is pasteurized at sufficiently high temperatures to yield anti-oxidizing properties. If the cream were susceptible to off-flavor development, the off-flavors were most generally present at 3 months of storage.
The initial titratable acidity was found to have little influence on the flavor of the stored cream when the cream was pasteurized at 165° F. for 15 minutes or higher. There appeared to be a direct correlation between a high titratable acidity and susceptibility toward off-flavor development in the stored cream when the cream was pasteurized at 150° F. for 30 minutes.
1 Jour. Article No. 615, n.s., Michigan Agricultural Experiment Station.
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