Journal of Food Processing & Technology

Abstract

Identification of Bacteria that Contribute to IMP Degradation in Horse Mackerel

Hiroko Seki and Naoko Hamada-Sato

Inosinic acid (inosine monophosphate, or IMP) is a taste component of fish that is broken down by an IMP-degrading enzyme (IMPase), impacting flavor. To measure IMPase activity, the enzyme is extracted as a solution from homogenized fish flesh, the IMP is then degraded by the enzyme, and the production of phosphoric acid from IMP is quantified. However, the degradation of IMP by bacteria that can be present in fish muscle could potentially affect the quantitation of endogenous IMPase activity. In this study, we isolated two bacterial strains from the enzyme solution obtained from horse mackerel and investigated their ability to degrade IMP. The isolates were identified as Pseudomonas fragi and either Pseudomonas veronii or Pseudomonas extremaustralis, as determined by 16S rDNA analysis. Of the two isolates, only P. fragi was found to be able to degrade IMP. Furthermore, the influence of the bacteria on the detection of IMPase activity was only seen when the reaction time was extended beyond 24 h.