The extent to which the transformation of nucleotides, biogenic amines, and microbiological changes affect the quality and shelf life of vacuum packaged low processed rainbow trout (Oncorhynchus mykiss) gravad during storage at 7 +/- 1 degrees C for 42 days was investigated. Although total viable counts increased slowly up to 6 log CFU g(-1) at the end of storage, coliform bacteria disappeared. The histamine concentration and the biogenic amine index increased up to 45.2 +/- 1.62 mg kg(-1) and 100 mg kg(-1) respectively. The highest concentration of inosine monophosphate was achieved in freshly prepared gravad, whereas the hypoxanthine level increased with storage time up to 28 days. Among nucleotide ratios, the G value is more suitable for the determination of gravad quality than K, K-i and H values. Once the gravad obtained the limit of acceptability by the panelists (35 days) the G value rose to 470%.