Extending the shelf life of red chilies (Capsicum annuum): exploring steam, microwave, and pulsed light treatments under different storage conditions†

Abstract

Red chilies face significant challenges in maintaining quality and safety during storage, thus necessitating effective preservation strategies to extend their shelf life under varying environmental conditions. In this study, the effects of steam (ST) (120 °C|300 s), microwave (MW) (540 kJ), and pulsed light (PL) (2.59 J cm⁻²) conditions on the shelf life of 0.6 and 0.35 a_w red chillies were examined while packed in polypropylene (PP) pouches under ambient (28 °C) and refrigerated storage (4 °C) conditions. Post-treatment, steam-treated red chillies retained 26.0% and 22.0% fewer phenolics, 37.4% and 36.2% fewer flavonoids, 13.3% and 9.4% fewer antioxidants, 34.6% and 35.0% fewer ascorbic acid, and 13.7% and 24.1% fewer carotenoids than MW and PL treated chillies, respectively. Based on the microbiological limit of 6 log₁₀ CFU g⁻¹, steam-treated red chillies had a shorter shelf life compared to even untreated samples, i.e., 22 days and 59 days for 0.60 and 0.35 a_w chillies, whereas untreated chillies had 35 days and 101 days for respective a_w under ambient storage. Meanwhile, the shelf life of microwave and pulsed light-treated red chillies was more than 150 days at both a_w and storage temperatures. There was a significant colour change in steam-treated samples with an E* value of 7.85 compared to MW (2.15) and PL (2.30). Even after 210 days, PL-treated red chilies retained >80% of their bioactive compounds. The first-order kinetic model confirmed that the retention of bioactive compounds is greater in MW- and PL-treated samples than in steam-treated chillies at both a_w and storage temperatures. The red chillies treated with MW showed almost similar shelf life to the PL treated chillies in terms of all the quality attributes, but there was an increase (3.3% to 24.9%) in enzyme activity after PL treatment. Hence, MW and PL can be used as alternative sterilization techniques to extend the shelf life of red chillies.