Preservation Effect of Ultrasonic-ε-Polylysine Hydrochloride Compound Treatment on Fresh-cut Apples

In order to improve the quality of fresh-cut apples and prolong the shelf life, the optimal parameters and fresh-keeping effect of ultrasonic-ε-polylysine hydrochloride compound treatment of fresh-cut apple were explored. Box-Behnken design was used to determine the optimal parameters of ultrasonic-ε-polylysine hydrochloride compound treatment of fresh-cut apples with the growth of the total number of colonies as the response value by response surface method. According to the results of the total number of colonies, mold and yeast, color difference and V_C content, the fresh-keeping effect of ultrasonic-ε-polylysine hydrochloride compound treatment on fresh-cut apples during storage was evaluated. The results showed that the optimal parameters of ultrasonic-ε-polylysine hydrochloride compound treatment for fresh-cut apples were as follows: Ultrasonic time 10 min, ultrasonic temperature 40 ℃, ε-polylysine hydrochloride concentration 0.2 g/L. The actual values of before and after cutting were 1.59 lg CFU/g and 1.71 lg CFU/g, respectively, and the relative errors with the predicted values were 3.92% and 5.59%, respectively, indicating the high degree of fitting and reliability of the models. During storage at 4 ℃, the growth rates of bacteria, mold and yeast in the fresh-cut apples treated with optimized conditions were significantly lower than that in the CK (P<0.05), and V_C was not significantly damaged. The color difference rise rate was lower in the ultrasound-ε-polylysine hydrochloride compound treatment group before cutting than that of the CK. The combined treatment of fresh-cut apples with ultrasonic-ε-polylysine hydrochloride optimized by response surface method was feasible, and the effect of ultrasonic treatment before cutting was better, and the shelf life was longer 4 days than that of the CK.