358. The effect of a high pre-heating temperature with and without ethyl gallate on the storage life of whole-milk powder spray-dried on a Gray-Jensen drier

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Abstract
1. Storage tests have been made independently in two laboratories on four samples of spray-dried whole-milk powder prepared on a Gray-Jensen plant from one batch of milk using pre-heating temperatures of 160 and 190° F. with and without the addition of 0·06–0·08% of ethyl gallate as antioxidant. The powders were packed in lacquered and in plain tinplate containers and stored at 47, 37 and 15° C, and at room temperature. Deterioration was followed by tasting tests, by determination of the amount of oxygen absorbed by the powders and by estimation of peroxide in the fat.2. Raising the pre-heating temperature from 160 to 190° F. or the addition of ethyl gallate to the milk improved the keeping quality of the resulting powder, as measured by taste, by a factor of the order of 1½–2½ at 47° C, of 2–3 at 37° C. and of 3–4 at 15° C. and room temperature.3. Increasing the pre-heating temperature and incorporating ethyl gallate in the milk extended the storage life of the powder by a factor of the order of 3 at 47° C., 4 at 37° C. and 8 at 15° C. and room temperature.4. For an equivalent loss of palatability powder from high-temperature pre-heated milk absorbed appreciably more oxygen than the corresponding powder from low-temperature pre-heated milk, and the gallate-treated samples slightly more than the corresponding control powders.5. The temperature coefficients for deterioration were slightly higher for the high-temperature powders than for the corresponding low-temperaturepowders.6. With the two control powders storage in lacquered tinplate resulted in a small increase, of the order of 10%, in keeping properties as comparedwith storage in plain tinplate. With the ethyl gallate-treated powders no advantage resulted from the use of lacquered tinplate.