Comparison of microbial inactivation and quality characteristics of Korean turbid rice wine, Makgeolli pasteurized with conventional and ohmic heating

Abstract

Makgeolli is traditional rice based turbid wine in Korea. In this study, Makgeolli, was subjected to ohmic heating (OH) and conventional heating (CH) at different temperatures (65, 75, and 85 degrees C), and yeast inactivation, physicochemical properties, bioactive compounds, antioxidant activity, and sensory scores were compared. The D-values for OH were about half the values of CH under the same treatment temperature. Makgeolli was pasteurized for 10 D at 65, 75, and 85 degrees C, and then the quality characteristics were analyzed. The yeast counts in Makgeolli were zero after pasteurization for 10 D. The reducing sugar level was significantly higher after OH treatment than that after CH treatment (p < 0.05); however, but the acidity was more stable than that following CH treatment. There were minimal differences in pH between ohmically heated Makgeolli (OHM) and conventionally heated Makgeolli (CHM). The total phenolic and flavonoid contents of OHM were significantly higher than those of CHM (p < 0.05), and the antioxidant activity of OHM was significantly higher than that of CHM at 65 degrees C (p < 0.05). The residual alpha-amylase and glucoamylase activities were highest after OH treatment at 65 degrees C. Furthermore, sensory evaluation showed no significant differences between OHM and untreated Makgeolli; the scores of all parameters of OHM were higher than those of CHM. These results indicate that OH at 65 degrees C can optimally pasteurize Makgeolli, and it can be effectively applied with minimal deterioration in the quality of Makgeolli compare to conventional heating.