Effect of Citric Acid and Vacuum Impregnation Washing on the Reduction of Escherichia coli and Quality of Fresh-cut Carrot

Abstract

This study aimed to evaluate the efficacy of combining citric acid and vacuum impregnation applied to the washing process to reduce Escherichia coli on the fresh-cut carrot. Additionally, the effect of combination treatment on carrot quality was determined. The interaction effect of washing conditions (atmospheric pressure (A) and vacuum impregnation (V)) and treatment time (5, 10, 15, and 20 min) in citric acid solution was studied. The maximum reduction of E. coli was 5 log CFU/g observed after washing with citric acid combined with vacuum impregnation for 15 and 20 min (p<0.05). However, fresh-cut carrots’ quality (pH, titratable acidity, and hardness) changed compared to unwashed controls. The washing with citric acid in atmospheric pressure for 15 min (A15) and citric acid combined with vacuum impregnation for 5 min (V5) accomplished a 3 log CFU/g reduction of E. coli on the fresh-cut carrot without causing adverse quality changes (pH, titratable acidity, and hardness), and also decreased the whiteness index. Scanning electron photomicrographs showed that most E. coli on carrot surface were washed out with citric acid combined with vacuum impregnation (V5), which was more than washing in atmospheric (A15). The number of E. coli on fresh-cut carrots subjected to vacuum impregnation washing treatment was lower in all storage (p ≥ 0.05). Using citric acid in combination with vacuum impregnation for 5 min could reduce the growth of E. coli and maintain the quality of fresh-cut carrots.