冷鲜猪肉货架期品质测定及主要致腐微生物预报

Shelf-life Properties of Chilled Pork and Forecasting of Main Putrescence Microorganisms

为研究微生物的生长和猪肉品质评定及理化性质之间的关系,及建立微生物模型进行预报,本实验采用基础培养基和多种选择性培养基对冷鲜猪肉中的主要致腐微生物进行分离和初步鉴定。自冷鲜猪肉购入的第1、3、5、7、9、11天分别对冷鲜猪肉的pH值、肉色、水分活度、系水力、嫩度和主要致腐微生物的数量进行测定。结果表明:pH值呈现先下降后上升的趋势;肉色a*一直降低,b*先下降后上升,L*随着保水性的升高,红度的降低和黄度的升高综合改变;水分活度变化不大;系水力逐渐下降;嫩度先下降后上升。以微生物菌落总数的对数和各主要致腐菌菌落总数的对数对贮藏时间求出其拟合曲线方程。各种微生物的方程不同,但大多趋势与理论相符合。温度和pH值对微生物的生长有影响,其他因素影响不大。微生物总数对数值与肉质、pH值、蒸煮损失之间成正相关,且差异显著(P<0.05)。微生物总数对数值与色差红度a*之间成负相关性,差异显著(P<0.05)。

In order to study the relationships between microbial growth and quality of pork and to establish the models forecasting growth of microorganisms, the main microorganisms causing the spoilage of chilled pork were isolated and identified using basic medium and a variety of selective media in this study. During 4 ℃ storage, chilled pork was analyzed for pH value, muscle color, water activity, water holding capacity, tenderness, and numbers of the main spoilage microorganisms. The experiments were done at intervals of 2 d from the first day until the eleventh day. The pH at first declined and then rose. The redness a ＊ of chromatic aberration kept descending, the b ＊ increased after the first drop, and the L ＊ had a integrated change with the drop of a＊, the increase of b＊ and the increase of water-holding capacity. Little change was found in the water activity. The water holding capacity was be found to gradually decline. The tenderness exhibited a trend of first increase and then decrease. The logarithmized total number of microorganisms and individual numbers of the main spoilage microorganisms could be simulated on a few fitted equations with storage time as an independent variable. The equations were different from each other, but all of them were consistent with the theoretical ones. Temperature and pH affected the growth of microorganisms, while other factors did not. There was a positive correlation between the logarithm of total number of microorganisms and the meat quality, pH value, and cooking loss, with a significant difference （P 〈 0.05）, while the logarithm of totai number of microorganisms was negatively correlated with the redness a＊ of chromatic aberration （P 〈0.05）.