Effect of retort sterilization on microbial safety and quality characteristics of a rice cake, songpyeon.

Rice cake, songpyeon, is a commonly consumed snack food in Korea. Currently, the recommended shelf life of rice cakes is only 1 day at room temperature because of concerns over quality deterioration and microbial safety. In this study, retort sterilization for 15 to 19 min was used to produce microbiologically safe songpyeon, and quality characteristics were analyzed. Sterilization of songpyeon at 121°C for 15 min resulted in complete eradication of Bacillus cereus and B. subtilis. Total plate count, yeast, fungi, and coliform counts were below detection. With increasing sterilization time, the average L* and a* values of songpyeon decreased from 28.86 to 23.07 and -1.63 to -6.73, respectively, whereas the b* value tended to increase from 4.91 to 9.82 on average, showing low lightness and high yellowness. Texture analysis showed increased gumminess (1240.6 to 2469.63 g) and decreased chewiness (2283.94 to 1366.26 g) and hardness (2933.94 to 1616.26 g) in songpyeon with increasing sterilization time. According to sensory evaluation, songpyeon sterilized at 121°C for 17 min was preferred by sensory panels based on average appearance (7.65), color (7.15), taste (7.45), and overall acceptance (7.4) scores. Therefore, sterilization at 121°C for 17 min is suggested to be optimal for producing microbiologically safe songpyeon with the best quality characteristics.