Table 1. Effect of oxygen concentration in modified atmosphere packaging (MAP) on the superoxide dismutase (SOD) activity and total reducing ability (TRA) of ground beef during storage

Items	Storage time (day)	O₂/CO₂/N₂ (%) in MAP
Items	Storage time (day)	0/20/80	25/20/55	50/20/30	75/20/5
SOD (U/g meat)	0	148.36±3.90	147.64±4.29^A	149.09±3.28^A	150.55±2.39^A
	3	143.38±4.91^a	132.31±4.32^bB	131.69±5.04^bB	131.08±6.07^bB
	7	139.52±2.89^a	93.44±2.89^bD	88.96±3.97^cD	86.40±3.43^cC
	11	144.62±10.81^a	99.08±4.91^bC	94.15±3.87^bC	92.92±2.78^bC
TRA	0	0.29±0.02^B	0.29±0.03^A	0.29±0.02^A	0.29±0.03^A
	3	0.39±0.04^aA	0.29±0.03^bA	0.27±0.03^bA	0.25±0.02^bB
	7	0.34±0.03^aA	0.17±0.02^bB	0.14±0.02^bB	0.11±0.01^cC
	11	0.24±0.02^aC	0.14±0.01^bC	0.12±0.01^bB	0.09±0.01^cC

Means±S.D. in the same row with different letters differ significantly (p<0.05).
Means±S.D. in the same column with different letters differ significantly (p<0.05).