Efficacy of gamma irradiation in improving the microbial and physical quality properties of dried by adgi chilli (Capsisum Annum L.) imported from India

Abstract

Dried chilli imported from India and China are widely used by local spices manufacturers to produce chilli powder and chilli-based products. Aflatoxins and microbial contamination in dried chilli are major public health and economic concern because they cause serious health and economic problems for consumers and producers around the world. Preliminary quality evaluation for dried chillies showed that Byadgi variety imported from India has high risk for aflatoxin and heavy microbial contamination but free from pathogenic Escherichia Coli (E. Coli). It is obligatory to diminish the aflatoxin contamination and reduce the microbial load in dried chilli to an acceptable level before it reaches the end users. Hence, this study aimed to evaluate the efficacy of gamma radiation and storage quality on microbial (Total Aerobic Count, coliform, yeast, mold, E. Coli) contamination, physical and chemical quality parameters (moisture, water activity, capsaicin, dihydrocapsaicin and surface colour) for dried Byadgi chilli. In this work, effect of various gamma radiation doses (0, 2.5, 5.0, 7.5 and 10.0 kGy) and the storage quality was evaluated up to 16 weeks. This study showed gamma radiation had no significant effect (p>0.05) on moisture content and water activity in dried Byadgi chilli, but the values increased with storage. Irradiation at 2.5 kGy resulted in the best capsaicin value compared to the other radiation doses. Furthermore, after storage, irirradiated samples showed better capsaicin retention compared to non-irirradiated samples. Gamma radiation did not give a significant effect (p>0.05) on the surface colour (L*, a*, b*, Chroma and hue). However, colour values in stored samples dropped drastically especially for control and 2.5 kGy irirradiated samples. Irradiation at 10.0 kGy did not help in preserving quality even though complete sterilization was achieved. Furthermore, irradiation at 10.0 kGy was unable to reduce colour and pungency loss upon storage of up to 16 weeks. The results obtained at 10.0 kGy irradiation could be benchmarked against 5.0 and 7.5 kGy radiation to provide some reference for the optimal setting of gamma irradiation dose for dried Byadgi chilli to be stored at ambient temperature. Preliminary quality evaluation for dried chilli is important to determine the appropriate radiation dose required for decontamination purposes whilst taking into consideration the physical properties such as moisture content, surface colour and pungency level. It was observed that low gamma radiation doses of 5.0 kGy and lesser proved to be a promising tool for reducing total microorganism and shelf-life extension up to 16 weeks at ambient temperature, with minimal effect on physical quality parameters.