Method Investigation to Control Inosinic Acid Degradation after Thermal Sterilization: the Effect of pH Change

Abstract

Although thermal sterilization reportedly alters the flavor of packed food, few studies have systematically examined this change. We have previously demonstrated that inosinic acid, which imparts umami in dried bonito extract (katsuo-dashi), decomposes to inosine and hypoxanthine; this decrease in the inosinic acid concentration contributes to flavor alteration (corroborated by sensory evaluation of a model liquid). Suppressing inosinic acid decomposition via sterilization may preserve katsuo-dashi's flavor. This study was focused on the role of pH in maintaining the flavor of katsuo-dashi after sterilization. Samples of katsuo-dashi and a model solution were enclosed in borosilicate glass ampoules and heated in an oil bath at 110, 120, and 130 ℃ to simulate thermal sterilization. After heating, the concentration of inosinic acid in the model solution, with pH 4.8–6.8 buffers, remained higher at pH 6.8 than at pH 4.8, indicating that adjusting pH could suppress inosinic acid decomposition. Therefore, a similar warming test was conducted by adjusting the pH of katsuodashi. However, in this case, the results varied, and the findings from the model solution were not reproduced. The complex components of katsuo-dashi influenced these results. Thus, pH adjustment was not effective for controlling inosinic acid decomposition and preserving flavor during thermal sterilization.