The Effect of Route Delivery on the Flavor, Riboflavin, and Ascorbic Acid Content of Milk

Abstract

Summary Approximately 70 per cent of all retail milk deliveries are removed from the doorstep or protected from light within five minutes after delivery while 3.3 per cent of customers leave milk exposed for more than two and one-half hours. Under experimental conditions of exposing milk to sunlight, the loss of ascorbic acid is extremely rapid with only insignificant quantities remaining after 30 minutes. Losses of this vitamin in the shade are also quite rapid. Riboflavin losses vary depending upon the intensity of sunlight, the temperature of the milk, and the size of bottles in which the milk is exposed. Under conditions of direct sunlight exposure for extended periods of time, milk loses significant quantities of this vitamin. On the other hand, the loss of riboflavin from milk exposed to shade does not exceed 25 per cent of that experienced in the direct sunlight. The photolysis of riboflavin stops when milk is removed from light while losses of ascorbic acid continue at a somewhat slower rate. The “sunlight” flavor, which develops in milk during exposure, appears to be a more critical problem than the loss of some of the riboflavin. On the basis of route studies and certain basic assumptions, it is believed that the average loss of riboflavin in all milk delivered does not exceed 3.25 per cent. It is the feeling of the writers that a program of consumer education in the care of milk can be of great value in maintaining the palatability and nutritional qualities of this important food. Further practical and fundamental studies are being conducted on the matters of “sunlight” flavor development and vitamin losses, the results of which will be reported in the near future.