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ThesisItem Open Access Design, development and evaluation of ozonation system for shelf life enhancement of minimally processed onion (Allium cepa L.)(Punjab Agricultural University, Ludhiana, 2019) Aslam, Raouf; Alam, M. S.The study was carried out to design and develop an ozonation treatment system for sanitization of horticultural produce with aqueous ozone. The developed ozonation system was evaluated for minimally processed onion (cut slices and whole peeled) based on kinetics of degradation, application methods, homogeneity of dissolution, ozone demand under no-load and full load of produce. The system was conceptually designed using CREO 3.0 software for a maximum design capacity of 15 kg minimally processed onion and the ozonation process parameters were optimized using response surface methodology. Experiments were conducted to optimize the developed system process parameters i.e. ozone concentration (1-5 ppm), exposure time (2-8 min) and pH of water (3-5) for cut sliced as well as whole peeled onion. Optimization was done to maximize microbial log reductions, pyruvate content and overall acceptability. In order to assess the efficacy of ozonation treatment, both the forms of minimally processed onion were sanitized at optimized conditions and were compared with samples exposed to 100 ppm chlorine and water washed (control). The treated samples were packed in cling wrapped HDPE tray packs and were stored under ambient (26.8 to 37.3 oC, 10-57% RH) as well as refrigerated conditions (5±1oC, 90±1% RH) and were monitored for change in quality attributes at regular intervals. The results revealed that the developed system effectively sanitized minimally processed onion without significantly affecting the quality parameters. The degradation kinetics of dissolved ozone was found to follow a first order reaction with a half-life of 18.23 min. Among different methods of ozone application tested, splashing method yielded better log reductions. Among the two types of minimally processed onion used for evaluation of developed system, cut slices were observed to exhibit a higher ozone demand in comparison to whole peeled onion. The optimized sanitizing conditions obtained for cut sliced onion were 5 ppm ozone concentration, 8 min of exposure time and an aqueous pH of 3.01 whereas 4.51 ppm ozone concentration, 8 min of exposure time and an aqueous pH of 3 for whole peeled onion with a desirability of 0.95. The samples stored under refrigerated conditions were observed to have a higher shelf life than samples stored under ambient conditions. Among the samples stored under ambient conditions, aqueous ozone treated samples had a significantly better shelf life (2 days) as compared to chlorine treated (1 day) samples. Whereas, under refrigerated storage conditions, a higher shelf life was observed for minimally processed onion treated with chlorine followed by ozone. The microbial shelf life of minimally processed onion treated with ozone and stored under refrigerated conditions was found out to be 13 days for cut slices and 16 days for whole peeled onion.