Effects of gamma and electron-beam irradiations on the stability of free radicals, bioactive compounds and microbial characteristics of turmeric powder

Turmeric is a functional ingredient commonly used in food, pharmaceutical, and cosmetic products due to its health benefits and bioactivity, including anti-inflammatory, antioxidant, and anticancer benefits. Irradiation is a common technique used to decontaminate microorganisms and extend the shelf life of spices. However, there are scientific debates over the use of irradiation in food products. This study aimed to assess the effects of ionizing radiation, including gamma rays and electron beams, on bioactive compounds and microbial characteristics of turmeric powder. Technically, high-performance liquid chromatography with UV–Vis detection was used to assess bioactive compounds. Another aim of the present study was to determine free radicals in irradiated and non-irradiated samples within one month of storage using electron paramagnetic resonance (EPR). Results showed that gamma and electron-beam irradiations could decrease microbial contamination of turmeric by approximately 5 and 6 log cfu/g, respectively. Contents of bioactive compounds increased in irradiated samples and curcumin contents in gamma and electron-beam irradiated samples were 232–248 and 215–266 mg/g dry weight (dw), respectively. Furthermore, the study detected that free radicals increased in all irradiated samples immediately after irradiation but decreased over time. Decrease in EPR signals was faster in gamma-irradiated samples during storage. Numbers of free radicals induced by gamma and electron-beam irradiations were 6.59–4.70, 2.69–1.60, 1.61–1.34, and 0.99–1.05 on days 0, 7, 14, and 21, respectively. After 21 days of storage, the numbers of free radicals in all non-irradiated and irradiated samples were similar. Therefore, free radicals induced by irradiations were degraded during storage and eliminated after 21 days.