A comparative study of gamma irradiation and hydrothermal processing on antioxidant properties, phytic acid, oxalate, and heavy metals content of rice bran

This study evaluated the efficacy of gamma irradiation (2.5, 5, 7.5, and 10 kGy) and hydrothermal processing in rice bran physico-chemical properties. The hydrothermal treatment was highly effective in decreasing phytic acid and oxalate content. Compared to the control, the treated samples exhibited reductions of 19.8% in phytic acid (from 437.01 ± 5.03 to 350.41 ± 5.10 mg/100 g) and 49.9% for oxalate (from 63.05 ± 0.05 to 31.55 ± 0.02 mg/100 g). The 5 kGy irradiation was the most effective dose for oxalate reduction and significantly enhanced antioxidant activity (DPPH and FRAP) and total phenolic content. While both treatments generally reduced mineral content, hydrothermal processing notably increased soluble calcium. A critical finding was the dose-dependent increase in lead concentration after irradiation and a more pronounced increase after hydrothermal treatment, although cadmium and arsenic levels remained undetectable. hydrothermal processing is superior for leaching the soluble antinutrients, such as phytic acid, gamma irradiation at 5 kGy is more effective in enhancing antioxidant capacity through the release of phenolic compounds, without the extensive leaching and thermal degradation of heat-sensitive antioxidants that occur during hydrothermal treatment. However, both methods can release heavy metals from complexes, presenting an important safety consideration. These findings support the application of these technologies to transform rice bran into a safer, high-value functional food ingredient.