Evaluation Of Meat Quality And Classification Of Freshness For Chilled Yellow Chicken

As the flu invasion of H7N9 and increasing awareness of public health and food safety among consumers in recent years,the live-poultry market of yellow-feather broiler(quality chicken)is shrinking and gradually replaced by chilled-quality yellow chicken(chilled yellow chicken)after slaughter and preliminary processing.But there is no evaluation standard of chilled yellow chicken so far and it is hard to identify the quality,as well as the time for storage and sale,of chilled yellow chicken for consumers.So the recognition and acceptance of chilled yellow chicken are hard.To help consumers to accept chilled yellow chickens better,we studied carcass appearance and meat quality firstly to decide whether they were suitable for chilled sale.Then we detected total bacteria of chilled yellow chickens on sale and found two key points of microbiological change.At last,sensory indicators and physical-chemical indicators of chilled yellow chickens were detected combined with electronic nose and tongue,meanwhile the freshness grades were divided.Firstly,chilled yellow chickens were chosen as material and pore density of back and abdomen were detected followed by pH value,meat color,water loss rate,tenderness and meat ingredients(water,protein,fat,collagen)of breast and thigh.Results showed that pore density of back was significantly higher(P<0.05)than abdomen and pore density of female was higher than male.The carcass is beautiful.In terms of meat quality,pH value,redness,tenderness,collagen and fat content of breast were higher than thigh,but lightness,water loss rate and protein content were lower.The results showed that breast meat was tender and contained high protein.Thigh meat was red,bright and high level of collagen and fat.So Xueshan yellow chicken was beautiful on carcass and good on meat quality,which was suitable for chilled processing.Secondly,total viable counts of chilled yellow chickens stored at 4 ? purchased from supermarket were detected and the results showed that the number of bacteria raised as time growing and it raised quickly in the first three days,with significant difference,until it exceeded 107cfu/g which meant spoil among all samples at five days during storage.So three days for storing was the first key point and the five days was the second key point in the decline of freshness.In addition,there was difference between both genders and parts in the freshness of chicken meat.Male samples spoiled more quickly than female and thigh samples spoiled more quickly than breast.Thirdly,to determine and grade the freshness of chilled yellow chicken,sensory indicators,pH values,ATP and IMP contents were detected combined with electronic nose and tongue,then the freshness of chilled yellow chicken was evaluated and divided.Results suggested that,there was large changes from three to five days among sensory indicators,pH values,ATP and IMP contents.All G0/G values of sensors were declined to minimum at storing four days and discriminant analysis showed that the odor of samples stored for four days was different obviously from those for three or five days.LDA results of electronic tongue suggested that storing for 3 and 5 days were two key points.Combining with the number of bacterial,we divided the freshness of chilled yellow chicken into three level:the chilled yellow chicken stored within three days was first freshness grade,from 3 to 5 days was the second freshness grade,above 5 days was non-freshness grade.