Effectiveness of pulsed light treatment for degradation and detoxification of aflatoxin B1 and B2 in rough rice and rice bran

Aflatoxins primarily accumulate in the hull and bran layers of rough rice making these by-products of rice milling unsuitable for animal feed or human consumption. Contaminated rough rice is also a potential source of aflatoxin exposure to workers handling the grain during post-harvest storage and processing. Currently, no technologies are available to remove or detoxify these toxic and mutagenic fungal metabolites from contaminated rough rice. Pulsed light (PL) is a novel technology with the potential to degrade and detoxify aflatoxins in foods and their processing by-products. Rough rice was inoculated with Aspergillus flavus to produce aflatoxin B1 (AFB1) and B2 (AFB2) contamination, followed by PL treatments of 0.52 J/cm2/pulse for various durations. A PL treatment time of 80 s reduced AFB1 and AFB2 in rough rice by 75.0% and 39.2%, respectively; while a treatment time of 15 s reduced AFB1 and AFB2 in rice bran by 90.3% and 86.7%, respectively. Since PL treatments result in the degradation of aflatoxins in situ, the toxicity and mutagenic activity of the residual by-products of AFB1 and AFB2 after PL treatment were evaluated. Toxicity was estimated using the brine shrimp (Artemia salina) lethality assay and mutagenicity measured by the fluctuation test with Salmonella typhimurum tester strains TA98 and TA100. The mutagenic activity of AFB1 and AFB2 was completely eliminated by PL treatment, while the toxicity of these two aflatoxins was significantly decreased. The obtained results suggest that PL technology has a promising potential to degrade, detoxify, and inactivate the mutagenic activity of aflatoxins in rough rice and rice bran.