伊拉兔宰后肌糖原变化及其与兔肉品质的相关性

Variation of Muscle Glycogen of IRA Rabbit After Slaughter and Its Correlation with Changes of Rabbit Meat Quality

【目的】探讨伊拉兔宰后36 h内肌糖原变化规律及与肉品品质变化的相关性。【方法】伊拉兔经屠宰之后,肌肉内的糖原会在一定时间内酵解转化为乳酸,从而改变胴体的pH值,并进一步影响肉品的持水力、剪切力、肉色等品质指标。以伊拉兔背最长肌(LD)和左后腿肌(LL)为原料,用试剂盒法分别测定了伊拉兔宰后45 min、4 h、8 h、12 h、24 h、36 h肌糖原含量的变化,并对兔宰后相应时间点的肉品品质指标如pH值、蒸煮损失、滴水损失、剪切力、色泽变化进行了检测与分析。此外,将主要设计因子(pH、蒸煮损失、滴水损失、总损失、剪切力、L*、a*、b*、C*)作为X变量,以肌糖原的含量作为Y变量,用偏最小二乘回归分析法(PLS2)对伊拉兔宰后LD和LL肉品品质与肌糖原变化规律的相关性进行探讨。【结果】伊拉兔宰后36 h内部位LD和LL的肌糖原含量均下降显著(P<0.05),二者分别从屠宰初期的(2.61±0.50)mg·g-1和(2.77±0.55)mg·g-1减少为宰后36 h的(0.94±0.05)mg·g-1和(0.99±0.07)mg·g-1。与此同时,伊拉兔LD和LL的pH分别从宰后初期的(6.91±0.02)和(6.85±0.04)下降至(5.62±0.09)和(5.61±0.09)。在此期间,随着pH的下降,伊拉兔肉品品质指标也发生了相应地改变,如剪切力、亮度L*值、红度a*值降低;蒸煮损失、滴水损失、总损失、b*值和C*值升高。PLS2分析显示,以上各肉品品质指标与兔宰后肌糖原含量变化的相关性均较大,部位LD和LL的回归系数R值分别达0.796—0.972和0.890—0.996。其中,2个部位的总损失指标(蒸煮损失与滴水损失之和)较其他肉品品质的差异来源更为显著。此外,可以用以上兔肉宰后品质指标为自变量,运用Unscrambler建立回归方程对肌糖原变化评分较好地进行预测。【结论】伊拉兔宰后36 h内肌糖原下降显著,与其间肉品品质的变化密切相关,可利用其酵解规律与各品质指标的相关性建立回归方程,从而对肌糖原含量变化进行较好地预测。

[Objective] This paper is to discuss the relevance between the change of muscle glycogen and meat quality of IRA rabbit within 36 h slaughter. [Method] After slaughter, the intramuscular glycogen of IRA rabbit occurs glyeolysis reaction into lactic acid in a certain period of time, thus changing the pH value of the carcass, and further affecting meat quality indicators, such as water holding capacity, shear force, color and so on. The longissimus dorsi （LD） muscle and the left leg （LL） muscle were used as raw materials and the variation in content of muscle glycogen of IRA rabbit at 45 min, 4 h, 8 h, 12 h, 24 h and 36 h slaughter period was measured, respectively, by kit method, and the related meat quality indexes during corresponding post-mortem, such as pH,cooking loss, drip loss, shear force and color changes were all determined. In addition, the correlation between meat quality and muscle glycogen variation of IRA rabbit from LD and LL during the 36 h post-mortem were discussed, by the way of partial least squares regression analysis （PLS2）, making the main design factors （pH, cooking loss, drip loss, total loss, shear force, L＊, a＊, b＊, C＊） as X variables, and muscle glycogen content as Y variables. [Result] The muscle glycogen content of LD and LL of IRA rabbit decreased significantly （P〈0.05） within 36 h slaughter, reduced from the initial （2.61~0.50） mg.g1 and （2.77＋0.55） mg.gl to （0.94＋0.05） mg.g1 and （0.99 ~ 0.07） mg＇g1 after 36 h slaughter, respectively. At the same time, the pH value of LD and LL of Iraq rabbit meat decreased from （6.91 ＋ 0.02） and （6.85 ＋ 0.04） in the initial post-mortem to （5.62 ~ 0.09） and （5.61 ：~ 0.09） after 36 h slaughter, respectively. In the meantime, the meat quality index of Ira rabbit occurred corresponding changes as the pH value decreased, such as shear strength, lightness value L＊, redness value a＊ decreased; cooking loss, drip loss, total losses, the value of b＊ and the value of C＊ increased. PLS2 analysis shows that the correlations between the above meat quality indicators and muscle glycogen content of IRA rabbit during 36 h post-mortem were significant, and the R regression value of location LD and LL reached up to 0.796-0.972 and 0.890-0.996, respectively. Among them, the total loss indicators （sum of cooking loss and drip loss） of the two parts （LD and LL） were provided with more significant sources of variation, compared to other meat quality indexes. What＇s more, these meat quality indicators after slaughter can be used as independent variables to predict the score of muscle glycogen changes of IRA rabbit successfully by using Unscrambler regression equation. [ Conclusion] The decrease of muscle glycogen of IRA rabbit within 36 h slaughter period was significant, and the variation was closely related to the corresponding meat quality. Therefore, the correlation between glycolysis law and meat quality indicator can be used to set regression equation for the better prediction of muscle glycogen content changes.