STUDIES ON MODIFIED ATMOSPHERE PACKAGING OF THIN SLICED BEEF .1. EFFECT OF 2 MODIFIED ATMOSPHERE PACKAGING SYSTEMS ON PH VALUE, MICROBIAL-GROWTH, METMYOGLOBIN FORMATION AND LIPID OXIDATION OF THIN SLICED BEEF

This study was conducted to determine the effect of two modified atmos phere packaging systems with and without vacuum treatment on storage q uality characteristic of thin sliced beef stored at 5 degrees C. Thin sliced beef was packaged in atmospheres of: (A) air without gas flush treatment (control), (B) 20% CO2 + 80% O-2 after vacuum treatment and (C) 20% CO2 + 80% O-2 without vacuum treatment. After 0, 2, 4, 6 and 8 days of storage, each sample was evaluated for pH value, microbial gr owth metmyoglobin (MetMb) formation, lipid oxidation (TEA number). The pH value of the control was significantly higher than those of (B) an d (C) samples after 8 days of storage. The viable and psychrotrophic b acterial counts and the number of coliforms of (B) and (C) samples wer e less than those of the control during storage. The control, (B) and (C) samples attained a MetMb level of 20% after 3, 5 and 6 days of sto rage, respectively. At 6 days of storage, MetMb formation of (C) sampl e was significantly lower than that of the control, but the difference in the results of the control and (B) sample could not be regarded as significant. Although the TEA numbers of (B) and (C) samples were hig her than those of the control, both samples maintained a TEA number of 3.0 even after 6 days of storage. These results suggested that the di fferences in pH value, microbial growth, lipid oxidation of vacuum bet ween samples with and without vacuum treatment were not recognized sig nificantly, but the rate of MetMb formation may be different between t hem during storage.