Changes in quality attributes of pulsed light treated dehydrated onion shreds during storage

Processing of dehydrated onion shreds involves contamination during peeling, chopping, and dehydration. Pre-treatments such as blanching, dipping and soaking in chemical solutions reduce the contamination prior to dehydration. Post dehydration treatments include thermal and non-thermal technologies. Hot water blanching in presence of CaCl2 as pre-treatment followed by pulsed light of 2208 ± 0.5 J·cm−2 (2100 V, 120 s) as post-dehydration treatment is employed. Further, the microbial quality and other attributes were assessed during the storage at 25, 30, and 37 °C. The population for aerobic mesophiles and yeasts & molds crossed 5 and 4 log CFU∙g−1, respectively after 30, 27, 19 days of storage at 25, 30, and 37 °C, respectively. Browning index, pyruvic acid, total phenols and flavonoids were most sensitive among the color parameters and bioactive compounds degraded during storage. After 30 days of storage at 25 °C, there was reduction of 82% in ascorbic acid, 39% in pyruvic acid, 93% in thiosulphinate, 50% in total phenolics, and 52% in total flavonoids content of the shreds. At 37 °C, the rate of bioactive degradation was higher and the retention in bioactives after 19 days was 24, 56, 35, 35, and 52% of ascorbic acid, pyruvic acid, thiosulphinate, total phenolics, and total flavonoids content, respectively. The pyruvic acid, ascorbic acid, phenolic and flavonoid content in the onion shreds degraded following first order kinetics, whereas thiosulphinates followed zero order degradation. The shelf-life of the pulsed light decontaminated dehydrated onion shreds was 30, 27, 19 days at 25, 30, and 37 °C, respectively. Pulsed light treatment is recommended for dehydrated onion shreds as an effective technology for microbial inactivation.