Flavour and vitamin stability in pasteurized milk in polyethylene‐coated cartons and in polyethylene bottles

Commercially pasteurized, non‐homogenized full cream milk in 2‐pt white polyethylene (PE)‐coated cartons overprinted with blue, and in 4‐pt PE bottles was stored for 4 d in the dark or under white fluorescent light of 4000 1x, at a temperature of 7°C. The flavour of milks kept in the dark remained good, but exposure to light resulted in early off‐flavour development: cartoned milk was disliked by a flavour panel after about 17.5 h exposure and milk in the PE bottles after 9 h. Vitamins A and B 2 were stable in the milk during 4 d storage in the dark in both bottles and cartons, and in cartons exposed to light. In the bottled milks, light‐induced losses of these vitamins after 4 d were, respectively, 15% and 35%. but there was little or no loss before the development of light‐induced flavour. Loss of total vitamin C by day 4 was about 50% in the dark, irrespective of container. In the cartons exposed to light, 66% of the vitamin C was lost, while virtually none remained in the exposed, bottled milk. There was also a markedly greater loss of vitamin C in the bottled milk than in the cartoned milk at the time the flavour became unacceptable. The dissolved O 2 concentration dropped considerably in the bottled milk exposed to light, but only marginally in the cartons. There were small increases in dissolved O 2 in the dark in both types of container.