Five 1-gal. retail containers were evaluated for their protection of homogenized milk against development of light-induced flavor and degradation of riboflavin. These were clear polycarbonate, tinted polycarbonate, high-density polyethylene, and glass returnable containers and an unprinted fiberboard non-returnable container. All containers were held in a commercial sliding door display case at 7 ± 1 C illuminated to 1076 lx with a fluorescent lamp up to 72 h. Sensory evaluation was conducted by a trained panel using hedonic 9-point scoring and magnitude estimation scale techniques. Riboflavin was determined by the fluorometric method. An evaluation of the containers demonstrated that there was a significant difference (P < .05) in preference and degree of light-induced flavor between the milk held in clear polycarbonate and glass compared to the control milk after 12 h of exposure. Milk held in high-density polyethylene was significantly different in preference from the unexposed control following 12 h when evaluated by the hedonic method; however, 24 h of exposure were needed to demonstrate a significant difference in the degree of light-induced flavor using the magnitude estimation technique. The tinted polycarbonate container, which is fabricated with a blocking agent that inhibits transmission of light at 380–480 nm, provided the milk with greatest protection of the returnable containers against development of the off-flavor. Milks exposed in fiberboard and also milks in the five containers held in the dark were not significantly different from the unexposed control. The milks held in glass demonstrated significant losses in riboflavin following exposure.
1Authorized for publication on June 5, 1978 as paper no. 5527 in the journal series of the Pennsylvania Agricultural Experiment Station.