Infrared-Treated Diced Dehydrated Onion: Microbiological Shelf Life and Quality Changes

Abstract

Onion dehydration has been associated with surface contamination. Blanching treatments eliminate surface contamination and improve color and texture of the onion prior to dehydration. However, contamination may occur during dehydration through air and human contact. Infrared treatment on the diced dehydrated onion was explored as post-dehydration treatment. Hot water blanching pretreatment with CaCl2 and infrared treatment at 80°C for 15 min post-dehydration were employed. The quality attributes and microbiological safety were assessed to estimate the shelf life. Samples stored at 25°C and 75% relative humidity had a shelf life of 25 days. Samples stored at 30°C had a shelf life of 20 days, and those stored at 37°C had a shelf life of 16 days. Browning index was the most sensitive property, having an activation energy of 48.759 ± 0.31 kJ·mol−1, followed by total color change, flavonoid, and pyruvic acid content. The quality attributes degraded as per first-order kinetics. During the microbiological storage period, about 25%–39% of ascorbic acid, 47%–57% of pyruvic acid, 14%–30% of thiosulphinate content, 66%–76% of total phenolics, and 36%–39% of total flavonoid were retained. The microbiological shelf life of the infrared-treated diced dehydrated onion was 26, 20, and 16 days at 25°C, 30°C, and 37°C, respectively.