生鲜猪肉鲜度指标评定及呈味核苷酸降解规律的研究

Evaluation of fresh pork umami index and study on flavor nucleotides degradation process

采用高效液相色谱法对生鲜猪肉鲜度指标进行评定,并研究了呈味核苷酸降解规律,旨在为其保鲜提供理论依据。以杜长大商品猪为研究对象,在4℃的冷藏条件下对其屠宰后的生鲜猪肉进行保藏试验。通过高效液相色谱法对不同保藏期间肌肉中的呈味核苷酸如肌苷酸（IMP）、肌苷（HxR）和次黄嘌呤（Hx）等进行分析,进而了解鲜度指标K值的变化趋势。结果显示：在选定色谱条件下,IMP,HxR和Hx在0.9～400 mg·m L-1范围内线性关系良好,加样平均回收率分别为100.61%,98.70%和99.11%,峰面积的RSD值分别为1.01%,0.55%和0.30%,该方法重现性好,结果准确可靠,适合于猪肉组织中IMP,HxR和Hx的定量分析;同时,研究还发现,生猪宰后48 h内IMP的质量比基本保持在一定水平,24 h略有上升,鲜度指标K值在24h内无明显变化（9.18%至6.04%）,但是24 h之后则显著上升,96 h达到29.48%,4 d内鲜度指标K值最小的时间是24 h,说明生鲜猪肉冷藏1 d后鲜味最浓。该研究建立和优化了猪肉鲜度的评价方法。

In order to provide theoretical basis for evaluating pork freshness in preservation,fresh pork umami index was evaluated and flavor nucleotides degradation process was investigated in this paper using high performance liquid chromatography（ HPLC）. The effects of refrigeration on keeping umami of duroc × landrace × Yorkshire commercial pork were investigated at 4℃,the contents of flavor nucleotides-related compounds,such as inosine 5＇-monophosphate（ IMP）,inosine（ HxR） and hydroxypurine（ Hx） in pork which stored at 4℃,were determined by HPLC at different postmortem time. The K values and the assessing index of umami were calculated. The results were summarized as follows： The investigated compounds including IMP,HxR and Hx showed good linearities in the range of 0. 9- 400 mg·m L- 1. The average recoveries of IMP,Hx,HxR were 100. 61%,98. 70% and 99. 11%,respectively,and their repeatability index RSD results of peak area were 1. 01%,0. 55% and 0. 30%,respectively. This method was accuracy,sensitivity and feasibility to analyze the nucleotides in pork. Meantime,IMP quality ratio re-mained at a high level during the first 48 h in preservation,increased slightly at postmortem 24 h. K value had no significant change within 24 h,but increased fastly after 24 h and reached to 29. 48% at postmortem 96 h. The minimum K value was 6. 04 at postmortem 24 h,which indicated that fresh pork had the best umami index at postmortem24 h at 4℃. The evaluation method of fresh pork umami index was established and optimized in this study.