Effect of Fasting on Rigor Mortis and Meat Quality of Chicken Breast Muscle
|School||Nanjing Agricultural College|
|Course||Of Food Science|
|Keywords||fasting rigor energy quality chicken sausage ultrastructure|
Fasting is a very important pre-slaughter handling practice to decrease contamination during transportation of live animals and slaughtering. This paper was designed to investigate the effect of fasting on postmortem energy depletion, rigor mortis, meat quality and technological quality of chicken breast muscle. Sanhuang broilers were fasted for 0,8, 16 and 24 h respectively. Breast muscles were removed from hot carcasses at 20 min postmortem and chilled at 2-4℃. During chilling, energy and rigor process (glycogen, lactic acid, ATP、ADP、AMP、IMP、pH, fiber diameter, sarcomere, rigor curve), meat quality (color, pressing loss, drip loss, cooking loss, NMR T22, shear force, protein solubility, myofibrillar profile on SDS-PAGE) and technological properties of chicken sausage (color, cooking loss, pressing loss, shear force and TPA) were determined or measured at different time points. The results were shown as follows:(1) Changes of energy and rigor process with fasting. Increasing fasting time resulted in a decrease in glycogen content (p<0.05). Fasting for 24 h induced lower ATP and ADP levels than control, but short-term fasting did not affect ATP and ADP level. Fasting also led to faster pH decline than control and ultimate pH arrived earlier. Fasting also resulted in lower muscle fiber diameter. Muscles fasted for 8 and 16 h entered into rigor earlier than controls. However, muscles fasted for 24 h did not enter into rigor at all. Therefore, fasting resulted in faster depletion of glycogen content, ATP and ADP (p<0.05), pH decline and rigor mortis.(2) Changes of meat quality with fasting. Muscle L* value increased and then decreased with fasting time. Muscle a* and b* values were not affected. During rigor, water holding capacity decreased, which was increased by fasting. Percentage of NMR T22 peak area had a similar change to cooking loss and drip loss. Fasting resulted in the highest shear force values at earlier time points but much lower values during rigor resolution. Fasting for 8 and 16 h increased protein solubility, however, fasting for 24 h decreased protein solubility. On myofibrillar SDS-PAGE gels, a band with 45 kDa appeared in fasting groups but not in control, which could be due to the binding of glycolytic enzymes to myofibrillar proteins. Samples from muscles fasted for 24 h had higher band intensities for bands 29 kDa and 33 kDa than control, which could contribute to meat tenderization. Therefore, fasting for 8 to 16 h increased water holding capacity and tenderness of chicken muscle.(3) Changes of technological properties of chicken sausage with fasting. Fasting resulted in a decrease in L* and b* values of chicken sausage. Fasting decreased shear force value of sausage but increased pressing loss. Fasting also decreased hardness, springiness, cohesiveness, gumminess and chewiness.In summary, fasting resulted in earlier rigor mortis, lower intensity of rigor, faster postmortem aging. Fasting 8 and 16 h group had better eating quality than fasting 24 h group. Before rigor, fasted muscles had lower technological properties of chicken sausage than control, however, it was improved after rigor. In practice, fasting for 8 to 16 h is a good choice.