| Under industrial conditions, shrinkage represents a serious economic concern during pork carcasses chilling, and microbial contamination is fearful on the slaughter line, therefore, it is necessary to take measures to control shrinkage and microbial contamination. This study was designed to determine effects of spray-chilling and lactic acid on surface bacteriology, meat color and pork carcass shrinkage in different seasons. The contents and results are as follows:1. Effects of season and spray-chilling on carcass shrinkage and pork qualityThe effects of season and spray-chilling on carcass shrinkage and pork quality were evaluated. One hundred and fifty crossbred pigs were randomly and equally allocated to five groups (four spray-chilling groups and one air-chilling) at 45 rain post-mortem, and then placed in the same chiller in winter and summer, respectively. The carcass sides in spray-chilling groups were intermittently sprayed for 1 min at half-hour intervals for 4 h, 8 h, 12 h and 16 h, while control sides were air-chilled. Spray-chilling had significant effect (P＜0.05) on shrinkage. Drip loss, L*-value of M. longissimus, ultimate pH and microbial counts in summer were higher (P＜0.05) than those in winter. After 24 h chilling, the shrinkage were 1.28%, which is higher (P＜0.05) than shrinkage of 1.16%,0.99%,0.83% and 0.69% from spray-chilling sides in 4 h, 8 h, 12 h and 16 h, respectively.2. Effects of season and lactic acid on surface bacteriology, meat color of pork carcassUnder industrial conditions, the efficacy of surface decontamination, meat color of pork carcass were evaluated. Three factors: concentration of lactic acid (2.0%, 2.5% and 3.0%), temperature (35℃, 45℃and 55℃) and spray duration (30s, 45s and 60s) were selected and designed 9 different combinations. The results indicated that APC and TCC of all had significant decreased to the control. 3% treatment Group were lower than 2.0% and 3.0% treatment Groups. Concetration and temperature of Lactic acid had significant effect (P＜0.05) on APC and TCC. The 9 different combinations had significant effect on CIE a*(P＜0.05). Concetration and temperature of lactic acid had significant effect on CIE a*(P＜0.05).3. Effects of lactic acid and spray-chilling on pork surface decontamination in different seasonsThe effects of lactic acid and spray-chilling on pork surface decontamination were evaluated in different seasons. Four hundreds and eighty crossbred pigs were randomly and equally allocated to four batches (three spray-chilling batches and one air-chilling) at 45 min post-mortem, and then placed in the same chiller (0-4℃, 2.5m·s-1), respectively in winter and summer. The carcass sides in spray-chilling groups were intermittently sprayed for 60 s at half-hour intervals for 4, 8 and 12 h, whilst control sides were air-chilled. And then control and sprayed sides were chilled until 24 h post mortem. Every batch must be equally allocated to four different treatments: the first group was control; others were sprayed by lactic acid (2.5%, 3.0% and 4.0%). The results indicated that APC and TCC of pork carcasse in batches had no significant effect, but Groups in every batch had significant effect (P＜0.05) on APC and TCC. The two groups (2.5%, 45℃and 3.0%, 35℃) had the best effectiveness of decontamination on pork carcasses surface.
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