屠前緊迫對台灣土雞與白肉雞生化特性之影響

Abstract

中文摘要 本試驗目的在探討雞隻施予屠前禁食及追趕緊迫處理在台灣土雞與白肉雞屠前緊迫狀態之差異及其對屠後酵素與蛋白質功能性之影響。在本試驗中分為四個處理組，第一組為屠前禁食12小時只供給飲水，且屠前不施予追趕緊迫；第二組為屠前禁食12小時只供給飲水，且於屠前施予人為追趕緊迫，跑步追趕雞隻使之連續不停運動，計時10分鐘(避免讓雞隻休息或者碰撞造成瘀傷)；第三組為屠前正常供給飲水及飼料，且屠前不施予追趕緊迫；第四組為屠前正常供給飲水及飼料，且於屠前施予人為追趕10分鐘。測定項目包括：屠前血清性狀、放血率、肌肉總血原色素、血液pH值、肝臟pH值、屠後肌肉粗萃calpain及cathepsin D活性、肌原纖維與肌漿蛋白質溶解度、感官品評。 結果顯示：白肉雞與台灣土雞在屠前受到追趕緊迫，屠後有較低的血液pH值，較低的放血率及普遍會增加血清中glucose、Ca2+、CK、LDH與ALP濃度，其中台灣土雞較白肉雞血液pH下降較少，放血率較高，血清中CK及LDH濃度亦較低，且白肉雞由於緊迫和掙扎程度較高，造成放血不良而提高肌肉總血原色素。另外，台灣土雞較白肉雞有較高的肝臟pH值；而在蛋白質功能特性方面，白肉雞施予屠前緊迫處理，屠後有較高之粗萃calpain活性；而台灣土雞則相反，屠前施予追趕緊迫會使屠後胸肉有較低的粗萃calpain活性及屠後24小時有較高的cathepsin D活性；台灣土雞在蛋白質溶解度方面均以禁食處理加上屠前施予追趕緊迫組在屠後15min顯著有較高的肌原纖維蛋白和肌漿蛋白質溶解度(p<0.05)，未禁食處理加上屠前施予緊迫組則有最低的蛋白質溶解度；在白肉雞則是以肌漿蛋白溶解度有一致性的結果，肌原纖維蛋白溶解度則無顯著差異。整體而言台灣土雞各組之蛋白質溶解度均較白肉雞為高。官能品評結果發現，白肉雞方面大致上以禁食處理加上屠前施予追趕緊迫組有較高外觀評分、較高多汁性評分、較低嫩度評分及較高總接受性；台灣土雞方面則大致上以禁食處理加上屠前施予追趕緊迫組有較低外觀評分、較低嫩度評分與較高咀嚼性評分，在總接受性則各組差異不大。 綜合以上結果，白肉雞接受屠前緊迫之後，所造成之血清酵素變化較台灣土雞顯著，且放血程度較差；而在屠後雖然有較高之calpain嫩化酵素活性，蛋白質溶解度也有提高(禁食處理之下)，但在感官品評嫩度方面卻反而不被喜愛，且緊迫所造成各處理組之差異均較台灣土雞顯著，而台灣土雞接受屠前緊迫後，可能因為其較佳抗緊迫的特性使屠前肝醣含量仍很高，因而屠後乳酸堆積較多，肌肉pH值較低而影響肉質特性，但各處理組之差異不如白肉雞來的顯著，由此可推測台灣土雞可能比白肉雞有較佳之對抗緊迫能力。 關鍵詞：台灣土雞、緊迫、生化特性

ABSTRACT The purpose of this study was to investigate the effects of ante-mortem fasting and stress on stress reaction and changes of biochemistry characteristics post-mortem of Taiwan country chicken and broiler. All chickens were divided into four treatments, first, feed withdrawal for 12h and normal slaughter, second, feed withdrawal for 12h and chased for 10min before slaughter, third, feed withdrawal for 0 h and normal slaughter, and forth, withdrawal for 0 h and chased for 10 min before slaughter. Determine items include serum analysis of ante-mortem, bleeding rate, total heme pigment, blood pH, liver pH, activity of crude calpain and cathepsin D, myofibrillar and sarcoplasmic protein solubility, and panel evaluation. The results showed that ante-mortem chasing resulted in lower blood pH, bleeding rate, and higher glucose, Ca2+, CK, LDH, and ALP level of serum in broiler and Taiwan country chicken. Especially, that had less decrease of blood pH, higher bleeding rate, and lower CK and LDH level of serum in Taiwan country chicken than broiler. Additionally, ante-mortem chasing in broiler resulted in higher total heme pigment by low bleeding degree because of stress and struggle. Liver pH was higher in Taiwan country chicken than broiler. Aspect of protein function, ante-mortem chasing in broiler resulted in higher activity of crude calpain post-mortem, on the contrary, ante-mortem chasing in Taiwan country chicken resulted in lower activity of crude calpain from breast and higher activity of cathepsin D post-mortem at 24h. however, ante-mortem chasing with feed withdrawal had significant higher myofibrillar and sarcoplasmic protein solubility (p<0.05) post-mortem at 15 min, and ante-mortem chasing without feed withdrawal had the lowest protein solubility in Taiwan country chicken. And, sarcoplasmic protein solubility in broiler had the same results as Taiwan country chicken, however, all treatment had no significant difference on myofibrillar protein solubility from broiler. On the whole, protein solubility in Taiwan country chicken was higher than broiler. The result of panel evaluation showed that ante-mortem chasing with feed withdrawal had higher scores of appearance, juiciness, total acceptability, and lower scores of tenderness in broiler. In addition, ante-mortem chasing with feed withdrawal had lower scores of appearance, tenderness, and higher chewiness, and it had no difference on total acceptability in Taiwan country chicken. These results showed that changes of blood enzyme were more significant and the degree of bleeding was lower in broiler than Taiwan country chicken after ante-mortem chasing. Although ante-mortem chasing made higher calpain activity and protein solubility (with feed withdrawal) in broiler, the scores of tenderness wasn't higher than control treatment. Additionally, the difference among all treatment in broiler were higher than Taiwan country chicken. On the contrary, in Taiwan country chicken, perhaps because of anti-stress ability resulted that glycogen content still high ante-mortem, so that higer lactic acid accumulation, and resulted lower pH of muscle, and effect on meat quality further. However, the difference among all treatment wasn't significant in Taiwan country chicken than broiler. By these result, it is presumable that Taiwan country chicken herhaps has better anti-stress ability than broiler. Key words: Taiwan country chicken, stress, biochemistry characterist