Effectiveness of poly(ethylene terephthalate) and high-density polyethylene in protection of milk flavor

The development of certain off-flavors in whole milk (3.25% milk fat) as re lated to packaging material [glass, high-density polyethylene (HDPE), amber poly(ethylene terephthalate) (PETE), clear PETE, and clear PETE-UV] were e valuated after exposure to fluorescent light (1100 to 1300 Ix) for 18 d at 4 degreesC. Control samples packaged and stored under identical conditions were wrapped in foil to prevent light exposure. Selected flavor compounds i n milk were measured analytically on d 0, 7, 14, and 18 of storage, while i ntensities of "oxidation, " "acetaldehyde," and "lacks freshness" off-flavo rs were determined by sensory analysis at the same intervals. In light-expo sed samples, oxidation off-flavor was significantly lower when packaged in amber PETE versus other containers. Milk packaged in HDPE containers showed a significantly higher level of oxidation off flavor than milk packaged in PETE-UV containers but not higher than clear PETE or glass containers. No significant difference in acetaldehyde off-flavor was found between package material treatments (exposed or protected). Acetaldehyde concentration nev er exceeded flavor threshold levels, regardless of packaging material. Ambe r and PETE-UV materials proved to be a competitive packaging choice for mil k in preserving fresh milk flavor.