Effect of Sterilization Process on Physicochemical and Sensory Properties of Zongzi from Black Sticky Rice and Riceberry Rice in Retort Pouch

Abstract

This research examines the effect of heating on the quality of Zongzi products from black sticky rice and riceberry in the retort pouch. Including, the design of an appropriate sterilization process was studied at 121 °C for 10, 15, and 20 minutes, respectively. It was found that the total visible count < 10 CFU/g, which is safe for consumption. Then the moisture content value, water activity, color value (L*, a*, b*), total color difference (ΔE*), anthocyanin content and sensory evaluation were tested and compared with various properties before sterilization. The results found that L* and a* values tended to decrease after sterilization, while b* and (ΔE*) values were increased, which means the product darkened after prolonged sterilization. The hardness value of the product was highest at 35.30 N and was significantly different reduced (P≤0.05) after sterilization. The anthocyanin content also tended to decrease with increasing sterilization time. The results of anthocyanin content analysis in the product before sterilization gave a maximum value of 1.265 g/g dry weight. There was a tendency to decrease after heating at 121 °C for 10, 15, and 20 minutes, with values of 1.241, 1.144, and 0.885 g/g dry weight, respectively. In terms of moisture content and water activity, all test conditions were insignificantly different (P>0.05). Therefore, the optimum condition for producing Zongzi products in retort pouches was shown at a temperature of 121oC for 15 min due to its pleasing physical appearance and chemical properties. The number of microorganisms left in the product was lower than the standard, so it was safe for consumption. Finally, consumers had the highest satisfaction level with products soaked in hot water at 90±2oC for 5 min before consumption.