Effect Of Stepwise Chilling On Meat Color And Ultra-structure Of Chinese Cattle M.Longissimus Lumborum

Meat color is the main quality trait in beef.Generally,meat color plays a critical role in determining consumers’ purchasing decisions.The process of chilling has great influence on meat quality,temperature and pH value decline plays a decisive role during pre-rigor.Many studies have identified that the highest degree of meat color was obtained in pre-rigor temperrature of 12-18°C in vitro muscle,and the progress of chilling can effctively prevent cold contraction.Therefore,through different chilling methods to explore the mechamism of color stability,interpret the mechanism of the color deterioration in the process of storage time,and then find the effective countermeasures to improve the color stability,is an important scientific problems.The study designs a stepwise chilling that focuses on the temperature control in vitro meat carcass,in order to ensure muscles in 12-18°C to rigor mortis: quickly removes the M.Longissimus lumborum(LL)after slaughtering for chilling,making the temperature declines quickly to 14-16°C in 0-4°C,then the temperature of refrigeration maintains 6h in14-16°C,followed by 0-4°C chilling to 24 h postmortem.Left M.Longissimus lumborum(LL)was stepwise chilling,right M.Longissimus lumborum(LL)was conventional chilling,muscles have vaccum package in 0-4°C for aging after 24 h,quality indicators were evaluated after aging for 1,4,7,14 and 21 days.Different chilling methods can improve meat quality and avoid cold shortening.However,studies of beef ultra-structure analysis between different chilling methods are lacking,moreover,it is controversial about the benefits on meat quality by different chilling methods during postmortem aging.Therefore,it is significant to explore the effects of stepwise chilling method and aging time on ultra-structure.After simulated chilling process,ultra-structure were evaluated for 1,7 and 14 days.The main results were as follows:1.Compared with the conventional chilling,stepwise chilling process significantly improved the beef L *,a *,b * and C * values in 1 d,4 d,7 d,and have a lower metmyoglobin relative content(P < 0.05).2.Stepwise chilling treatment significantly increased the activity of lactatedehydrogenase,allows to generate more NADH,but with the extension of time,the 1 d and 7d significantly lower(P < 0.05),the aging time is higher than the effect of chilling treatment.3.Stepwise chilling treatment was significantly improved the metmyoglobin-reducing activity and total reducing activity,makes the color better.4.Electron microscopy examination of LL showed that stepwise chilling resulted in the degradation of Z-lines,lengthened I-bands and the bigger degree of degradation of myofibri.Therefore,comprehensive consideration of meat quality and safety,the enterprise economic benefit and so on,stepwise chilling process can not only improve the quality of the meat,but also can reduce the aging time,improve the color,cut costs,increase profits,can be used widely in slaughtering enterprises.