Combined Ascorbic Acid and Mild Heat Treatment to Improve the Quality of Fresh-Cut Carrots

Mild heat (MH) treatment and ascorbic acid (AsA) addition can improve the quality of fresh- cut produce when used individually; however, their combined effect remains unclear. Herein, fresh- cut carrots were used as models to explore the effects of MH (50 ◦C)–AsA (0.5%) on quality properties including reactive oxygen species (ROS) metabolism, antioxidants, lignin metabolism, naturally present microbes, and inoculated pathogens (Escherichia coli O157: H7 and Salmonella Typhimurium) during storage (0–5 d, 4 ◦C). The results indicate that the antioxidant properties in the MH–AsA group were consistent with those of single treatments, resulting in a consistent ROS-scavenging effect. From day 3–5, lignin synthesis was significantly inhibited by MH–AsA as compared with single treatments, probably because the two enzymes (phenylalanine ammonia-lyase and peroxidase) responsible for lignin synthesis exhibited lower expressions. Microbial analysis revealed that MH–AsA treatment led to the lowest counts of both pathogens and aerobic mesophilic bacteria at 0–5 d. Conversely, the inhibitory effect of MH–AsA treatment on mold and yeast was consistent with the single treatments. These results suggest that MH–AsA is a low-cost and safe approach to improve the physiological characteristics of fresh-cut produce while reducing microbial risk. Keywords: fresh-cut carrots; minimal processing; hurdle technology; pathogen