| A commercial hybrid pig crossed by Duroc, Landrace and York(D×L×Y) was selected for use in this study. The effects of slaughter weight, season and bagging on precooling loss, temperature and meat quality of pork carcass was studied. The changing regular of pork carcass under different slaughter weight, season and bagging conditions was investigated by studying its pH values, colors, tenderness and total plate count. The whole study is divided into the following several parts:(1) Effect of slaughter weight on precooling loss, temperature and meat quality of pork carcassThe hybrid pig carcass(D×L×Y) with 130 kg, 140 kg and 150 kg slaughter weight was selected for use in this study. The precooling loss of pork carcass, carcass temperature and meat quality before and after the precooling were studied. The results showed that the precooling loss of 130 kg carcass was obviously higher than other weight carcasses(P<0.05), but the total plate count had no obvious difference(P>0.05). After precooling the L* value of 130 kg carcass was obviously higher than that of 140 kg and 150kg(P<0.05). Before precooling, the a* value of 150 kg was significantly higher than that of 130 kg and 140kg(P<0.05). When the weight was same, the pH value after precooling were obviously lower than before precooling(P<0.05). Also the water content significantly decreased after precooling when the weight was 130 kg(P<0.05). The shear force after precooling was lower than before precooling at 130 kg and 140kg(P<0.05). Considering the energy saving and meat traits, the slaughtering weight of 140 kg is suitable for cold fresh meat production and 150 kg is suitable to produce hot fresh meat.(2) Effect of slaughter season on precooling loss, temperature and meat quality of pork carcass.Two slaughter seasons, the hot summer and the cold winter, was selected to study the season effect. The hybrid pig carcass(D×L×Y) with 110 kg slaughter weight was selected for use. The cooling time was 4h. The effect of season on carcass precooling loss, carcass temperature, and meat quality was studied. The results showed that in summer the pork carcass before precooling had a higher temperature(P<0.05) and precooling loss(P<0.05) than that in winter. The water content after precooling was lower than before precooling(P<0.05) in summer. Compared to winter, in summer the L* value of pork carcass increased significantly after precooling(P<0.05) and the a* value decreased obviously(P<0.05) before the precooling. The research showed that pork carcass in winter has good color and low precooling loss. Therefore, winter slaughter is more suitable for cold fresh meat production, however, summer slaughter is unfavorable for cooling.(3) Effect of bagging treatment on precooling loss, temperature and meat quality of pork carcassThe hybrid pig carcass(D×L×Y) with 110 kg slaughter weight was selected for use in this study. It was cooled for different times(2h, 4h, 8h, 12 h, 18 h, 24h). The difference of precooling loss, temperature and meat quality was studied with and without bagging. The results showed that the precooling loss increased significantly(P<0.05) when the cooling time was 8h. The precooling loss had little change(P>0.05) when the cooling time was 8h-18 h, but it increased significantly again(P<0.05) when cooling time was 24 h. In 2h-18h’s cooling, the precooling loss was increased significantly(P<0.05) without bagging. When cooling time was 4h, the tenderness degrees were significantly increased(P<0.05) both with and without bagging and then tended to be stable finally. Compared to 2h, the L* value increased significantly(P<0.05) with bagging at 12 h cooling and the a* value also increased significantly(P<0.05) at 8h cooling. Compared to pork carcass without bagging, the precooling loss of pork carcass with bagger decreased(P<0.05) at 4h-24 h cooling, the L* value increased(P<0.05) at 12 h cooling, and the total plate count significantly increased(P<0.05) at 12h-24 h cooling, But not exceeds the scope of the total number of colonies of fresh meat. The result showed that bagging can effectively reduce the precooling loss of pork carcass. When cooling time was 4h, the pork carcass had good tenderness and color. However, 8h cooling is better for carcass without bagging. Considering the energy saving and meat traits, the suitable cooling time for pork carcass with bagging is 4h. |
