Effect of various dairy packaging materials on the shelf life and flavor of ultrapasteurized milk

Raw milk from three different dairies (each a separate trial: 1, 2, and 3) was standardized to 2% fat and processed at 140.6, 129.4, 118.3, and 107.2 degreesC (temperatures 1, 2, 3, and 4, respectively) for 2 s and packaged i nto six different packaging boards, [standard (A) milk boards with standard seam, juice boards with standard (B) and J-bottom (D) seams, barrier board s with standard (C) and J-bottom (E) seams and foil (F) boards with J-botto m seam], resulting in 24 different treatments. Standard plate count (SPC) w as used to test for microbial quality, and taste panels were employed for f lavor acceptability and difference in the milk stored at 6.7 degreesC at 1, 2, 3, 5, 10, and 15 wk. Lipolysis was measured by standard procedures for acid degree value (ADV) of milk. Statistical analysis of taste panel data s howed that the flavor of 14 milk samples deteriorated over time. The flavor of UP milk packaged in standard (A) and juice (B and D) boards deteriorate d at a faster rate than UP milk packaged in barrier (C and E) and foil (F) boards. At wk 6, a slightly hammy or cardboardy flavor was detected for mil k packaged in boards with standard seams (A, B, and C) and a slightly cooke d flavor was detected for milk packaged in barrier and foil boards with J-b ottom (E and F) seams. The hammy or cardboardy flavor intensified with stor age time, and all of the cooked flavor dissipated at wk 10. Milk processed at 118.3 and 129.4 degreesC maintained the lowest bacterial growth rates, and milk processed at 107.2 degreesC had the highest bacteria l growth rates during 15 storage wk. More than 87% of milk processed at 118 .3, 129.4, and 140.6 degreesC maintained acceptable level of bacterial coun ts at wk 15. The extent of lipolysis showed that ADV of milk increased with storage time. The ranges of ADV for trials 1, 2, and 3 were 0.76 to 0.85 ( from 12 to 22 wk), 0.39 to 0.51 (from 6 to 16 wk), and 0.53 to 0.60 (from 6 to 16 wk), respectively.