Abstract:The total colony number, the bactericidal effect against mold and yeast, and bactericidal kinetics were studied, after short and medium-wave infrared radiations were applied on carrot powder at various temperatures (100 ℃, 110 ℃, and 120 ℃) for 1, 2, 3, 4, and 5 min. The effects of the treatments on carrot powder moisture-content and color were evaluated. The results showed that the bactericidal effects of infrared radiation were strengthened with increasing temperature and time; mold and yeast were more sensitive to temperature and could be inactivated by subjecting to 120 ℃ for 3 min, and the resulting decrease in moisture content was beneficial for prolonging storage time. The color difference value was increased after infrared radiation, particularly by treatments at 110 ℃ for 4 min and 5 min or 120 ℃ for 2~5 min. The Weibull model was used to fit the survival curve for bacteria grown on the carrot powder subjected to different treatments. The correlation coefficients (R2) of kinetic curves determined at three temperature levels were higher than 0.98, and the values of c2 and root-mean-square error (RMSE) were less than 0.01 and 0.40, respectively, indicating a good fit. Based on the bactericidal effect, the effects on water content and color, and the equipment operating cost, the optimal conditions for microbial inactivation of carrot powder using short- and medium-wave infrared radiation was determined to be 120 ℃ for 1 min.
