Abstract: 【Objective】Pre-slaughter fasting is defined as duration of food and water withdrawal during loading, unloading, transport and control during pre-slaughter lairage period. Impropriety of pre-slaughter handling decreases carcass yield, affects eating quality and technical characteristics of meat. The objective of this study was to investigate the effects of different pre-slaughter fasting time on quality of mutton and determine how long fasting time is suitable for production of high quality mutton.【Method】Thirty six-month old sheep were divided into 3 groups fasting for 0 h(control group), 12 h and 24 h. The eating quality (pH value, meat colour, shear force and water holding capacity), sensory quality (odour, tenderness, juiciness and overall liking), hygiene quality (aerobic plate count and coliforms), glycogen concentration, sarcomere length and protein degradation during post-mortem were analyzed.【Result】Fasting for 24 h resulted in higher pH value than 12 h and control group at 0 h, 45 min and 4 h post-mortem. As aging time extended, pH value at 24 h and 48 h post-mortem had no significant difference (P＜0.05). The group fasting for 24 h had lower cooking loss than 12 h and control group (P＜0.05). There was no significant difference among three groups in L*, a*, b*,ΔE, drip loss, shear force and sensory characteristics of odour, tenderness, juiciness and overall liking of the mutton (P＞0.05). Aerobic plate count and coliforms of the mutton from different fasting time groups were all under the range of national standard regulations at 24 h post-mortem. Aerobic plate count of mutton had no significant difference among three treatments. Coliforms of the mutton were decreased as the fasting time increased. Fasting treatments caused the decrease of enumeration of coliforms compared to control group. There was no significant difference in glycogen content of mutton at 0 h, 45 min, 4 h, 8 h, 12 h, 24 h and 48 h post-mortem among three groups. The degree of glycolysis increased but the glycogen content decreased as the extension of aging time. With the increase of pre-slaughter fasting time, sarcomere length increased. Fasting for 24 h resulted in larger sarcomere length than 12 h and fasting for 12 h was higher than 0 h (P＜0.05). The degree of myofibrillar protein degradation in different fasting treatments was consistent at 0 h post-mortem. There was no apparent bands appeared or disappeared. All groups had 27 kD fragment appeared at 24 h post-mortem. The appearance of the 27 kD was darker in fasting for 12 h and 24 h treatments than the control. It was shown that fasting for 24 h and 12 h resulted in higher protein degradation degree than the control group.【Conclusion】Fasting for 12 and 24 h increased the hygiene quality and accelerated meat myofibrillar protein degradation. Fasting for 24 h decreased cooking loss. Fasting for 12 and 24 h had no significant effects on pH value, glycogen content and other quality characteristics of mutton. Compared with the control group, fasting for 12 and 24 h had positive effects on mutton hygiene quality but no effect on eating quality and sensory quality.

Key words: sheep , pre-slaughter , fasting , meat quality