Abstract: 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·mL-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 remained 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 postmortem 24 h at 4℃. The evaluation method of fresh pork umami index was established and optimized in this study.

Key words: pork, inosine 5′\, monophosphate, inosine, hydroxypurine, high performance liquid chromatography, umami index