Aqueous ozone sanitization of whole peeled onion: Process optimization and evaluation of keeping quality during refrigerated storage

Fruits and vegetables, especially in their minimally processed form, are highly susceptible to microbial spoilage, highlighting the need of a safe and effective sanitizing agent to extend their shelf-life. This study was carried out to optimize the aqueous ozone sanitization parameters viz. ozone concentration (1-5 mg/L), exposure time (2-8 min), and pH (3-5) for whole peeled onion. Consequently, the keeping quality was investigated for ozonated (optimized conditions), chlorinated (100 mg/L) and water-washed samples packed in tray packs and stored under refrigerated conditions (5 +/- 1 degrees C, 90 +/- 1 % RH). Numerical optimization using the 3 factor, 3 level, Box and Behnken design suggested that aqueous ozone at 4.51 mg/L exposed to the onions for 8 min at a pH of 3 provided optimized sanitization that resulted in the most favorable reductions in microbial load (3.74 log CFU/g), pyruvate content (14.2 % less than fresh untreated) and a good overall acceptability score (8.5). After storage, the microbial shelf life obtained from optimized ozone sanitization was found to be 14.3 % (2 d) higher than waterwashed and 13.04 % lower than chlorinated samples. Ozone-treated onion was observed to retain better quality attributes in terms of pyruvate content, color change and firmness as compared to other treatments studied.

Automated summary

The study demonstrated that optimizing aqueous ozone sanitization parameters can improve the shelf life of onions, such as reducing microbial load, maintaining good quality, and overall acceptability. Compared to water-washed and chlorinated treatments, ozone-treated onions showed a longer microbial shelf life and retained better quality attributes during storage.