Ochratoxin A and Aspergillus spp. Contamination in Brown and Polished (White) Rice from Indian Markets

Rice is one of the most important staple foods for the human population, necessitating continuous monitoring for mycotoxin risk in particular in the sub-tropical area, such as India. In the present study, a total of eighty-one samples comprising brown (n = 36) and polished (white) rice (n = 45) intended for direct human consumption were collected from markets across various districts of Tamil Nadu, India, and analysed for ochratoxin A (OTA) and fungal contamination. Aspergillus ochraceus, an ochratoxigenic fungus belonging to Aspergillus section Circumdati, exhibits optimal growth and OTA production at temperatures ranging from 25 °C to 30 °C. Among the fungal isolates, Aspergillus niger and A. ochraceus were the most prevalent, occurring in 50 out of 81 samples (62%). A. ochraceus demonstrated a significantly higher OTA-producing capacity compared to A. niger, with an OTA concentration range of 12.3–196.8 µg/kg and 0.2–2.8 µg/kg. Chemical analysis of fifty fungal-contaminated market rice samples revealed that 76% (38/50) were contaminated with OTA. Further, detectable levels of OTA were observed in 83% of brown rice and 69% of polished rice samples, with the highest frequency falling within the range of 1–<3 µg/kg. However, none of the tested rice samples exceeded the acceptable OTA threshold set by the Food Safety and Standards Authority of India (FSSAI) (20 µg/kg), with all concentrations falling below the national regulatory limit. This study represents further insight into OTA exposure in rice, with greater concern regarding brown rice than white rice, and emphasizes the necessity of implementing sound and safe storage practices, effective management strategies, and continuous monitoring programs to prevent OTA contamination throughout the Indian rice supply chain.