Effects of alternative technologies on disinfection of carrot surface and quality parameters

Ready to eat products are spoiled very fast because they are not processed in any preservation method that inactivates spoilage microorganisms. Residues as well as micro and macro contaminants cause deterioration of soil originated products such as carrot. Therefore, it is important to process these products without losing their quality properties with microbial safety. Applications of ozone (O) (O1; 33.6 g/m3, 5 min and O2; 101 g/m3, 15 min), ultrasonication (US) (US1; 35 kHz, 5 min and US2; 35 kHz, 15 min), high hydrostatic pressure (HHP) (HHP1; 250 MPa, 5 min, HPP2; 350 MPa, 5 min and HPP3; 450 MPa, 5 min) and electrodialyzed water (EW) (EW1; pH 8.5, 15 min and EW2; pH 10, 15 min) for surface disinfection of carrots and the changes on the important quality parameters as well as inactivation of endogenous and inoculated microorganisms after the processes were determined in the study. pH, conductivity, titratable acidity (%), °Brix, color (L*, a* and b*), hue, chroma, total color difference, total antioxidant capacity, total phenolic content, total carotenoid, total beta carotene, total ascorbic acid, individual phenolic components, organic acids and changes in textural properties of carrots were determined. In order to determine the effects of the treatments on microbial reduction, total aerobic mesophilic bacteria count (TMAB), total mold and yeast count (TMY) and total coliform bacteria count (TCB), in addition to inactivation on inoculated Salmonella Typhimirium and Escherichia coli O157:H7 were conducted. According to the results, the HHP groups provided a significant decrease of 5.77 log kob/mL in TMAB, whereas the initial total mold and yeast (TMY) and total coliform (TCB) were completely inactivated. The most effective applications for E. coli O157:H7 inactivation were O and HHP groups. The most effective inactivation was observed at HPP3 (450 MPa for 5 min) on S. Typhimirium count. In general, microbial inactivation provided by US and EW were less than that of both O and HHP. Significant difference of color parameters was observed due to decrease on carotenoid content; while pH, °Brix, conductivity, titration acidity, total phenolic content were not significantly changed (p ˃ 0.05). HHP groups presented the best protective effect on the amount of ascorbic acid, although there were various reductions in the amount of organic acids. On the other hand, no important changes were detected on the textural properties of carrot samples by applied treatments.