Comparative effects of steam, microwave, and pulsed light treatments on the shelf life of fresh red chillies (Capsicum annum) at 28 °C and 4 °C

Abstract

Preserving the quality and safety of red chillies is challenging, making it essential to implement effective strategies that can extend their shelf life. This research evaluated the impact of steam (ST) (120 °C|300 s), microwave (MW) (480 kJ), and pulsed light (PL) (2.59 J·cm⁻²) on the shelf life of red chillies, packed in plastic tray stored at room temperature (28 °C) and under refrigeration (4 °C). Untreated and treated chillies were assessed for total phenolics, flavonoids, antioxidant capacity, ascorbic acid content, microbial load, enzyme activity, and colour stability (∆E*). Steam treatment caused the highest initial loss of bioactive compounds. For instance, red chillies retained 41.5 % and 27.1 % less phenolics, 67.3 % and 69.2 % less flavonoids, 14.5 % and 14.5 % less antioxidants, and 24.5 % and 26.5 % less ascorbic acid compared to those treated with MW and PL, respectively. Based on a microbial limit of 6-log₁₀ CFU·g⁻¹, steam-treated samples had a shelf life of 9 days at 28 °C, whereas MW and PL treatments extended shelf life up to 14 and 18 days, respectively. Under refrigerated conditions, the shelf life exceeded 15 days for MW and PL-treated chillies. Only PL treatment led to a 6 % increase in enzyme activity. Steam-treated samples showed significant colour degradation (∆E* = 7.85), in contrast to MW (2.15) and PL (2.30). MW and PL treatments preserved more than 70 % of the chillies' bioactive compounds till the end of the storage. The degradation of bioactive in chilli during storage was described by a first-order kinetic model. MW and PL-treated samples retained more bioactive compounds compared to steam-treated red chillies across both storage conditions. Therefore, MW and PL treatments emerge as promising alternatives for sterilizing red chillies while effectively enhancing their shelf life.