Effect of Sunshine upon the Ascorbic Acid and Riboflavin Content of Milk

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Abstract
A study has been made of the effect upon the ascorbic acid and riboflavin of exposing milk in commercial one-half pint bottles to the action of sunshine. The intensity of the sunshine was measured with a pyrheliometer equipped with an automatic recording device. The milk was exposed for two 30- or two 60-minute periods. The “sunshine” varied from a total of 4.8 gm. cal. per sq. cm. on a rainy day to 144.6 gm. cal. per sq. cm. on a bright day. The temperature of the milk varied from day to day depending upon velocity of the wind, greenhouse effect of the milk bottles and intensity of the sunshine. The destruction of reduced ascorbic acid was very rapid, for little, if any, was present after 30 minutes exposure. The riboflavin disappeared more slowly than the ascorbic acid. There was a 10% loss during 60 minutes exposure on a rainy day and about 85% loss during exposure to bright sunshine for 120 minutes. In general the destruction of riboflavin increased fairly consistently with the increase in intensity of the sunshine until 60–70% of the riboflavin was destroyed when the milk was exposed to a total of 50–70 gm. cal. per sq. cm. Increasing the sunshine from a total of 70 to 140 gm. cal. per sq. cm. caused a slow increase in the destruction of riboflavin. These data show that milk allowed to stand for more than a short period on the consumer's doorstep exposed to strong light or sunshine is likely to lose a large amount of its ascorbic acid and riboflavin.