Effect of shelf-life and light exposure on acetaldehyde concentration in milk packaged in HDPE and PETE bottles

Poly(ethylene terephthalate) (PETE) packaging is becoming an increasingly popular choice of packaging material for milk, but has the disadvantage of releasing odorous acetaldehyde into food matrices.

Sensory detection group thresholds for acetaldehyde in whole, low fat and nonfat unflavored milks were 3939, 4020, and 4040 ppb respectively with no significant difference due to fat level. Chocolate flavored milk and spring water showed detection thresholds levels for acetaldehyde of 10048 and 167 ppb respectively. This information assisted in determining if acetaldehyde migration from the package to the product would influence the flavor of the product.

Whole milk was packaged in glass, high density polyethylene (HDPE), amber PETE, clear PETE, and clear PETE with UV light block and was exposed to fluorescent light of 1100-1300 lux (100-120 FC) at 4oC for 18 days. Sensory and chemical analysis and was done on milk from all containers over a period of 18 days. Emphasis was on oxidation, acetaldehyde and lacks freshness off-flavors and byproducts.

All volatile flavor compounds studied (acetaldehyde, pentanal, dimethyl disulfide, and hexanal) were increased in light-exposed milk samples. Amber PETE showed the least amount of oxidation off-flavor, while clear PETE with UV block showed significantly less oxidation off-flavor than glass, clear PETE or HDPE on day 7 and 18. Acetaldehyde was not detected by sensory analysis in either light-exposed or light-protected samples. Chemical analysis showed relative acetaldehyde levels in glass (2220 ppb), HDPE (1265 ppb), amber PETE (3397 ppb), clear PETE (2930 ppb), and clear PETE with UV light block (1754 ppb) were all below concentrations found for human flavor threshold.