Natural Occurrence of Ustiloxin A and D in Rice in China

Rice, a staple food for more than half of the global population, undergoes multiple processing stages—such as harvesting, dehulling, milling, and polishing—before it reaches consumers. However, these processes not only alter the physical and nutritional characteristics of rice but may also affect the distribution and concentration of contaminants, thereby posing potential safety and quality risks. In this study, a total of 231 unhusked rice samples were collected from three provinces (Jiangsu, Anhui, and Fujian) in China between 2016 and 2018, along with 11 white rice samples purchased from supermarkets in 2018, and analyzed for the presence of ustiloxins A and D. After dehulling, 31.6% and 5.6% of the brown rice samples were found to be contaminated with ustiloxins A and D, respectively, while neither toxin was detected in the 11 white rice samples obtained from the market. The occurrence of ustiloxins A and D was higher in middle-late rice ecotypes than in the early rice ecotype, with the highest frequency observed in japonica-type rice. Geographically, Jiangsu Province had the highest incidence of ustiloxin A, whereas Anhui Province showed the highest occurrence of ustiloxin D. Importantly, the concentrations of both ustiloxins were higher in unhusked rice than in brown rice and white rice, underscoring that processing can significantly reduce, though not completely eliminate, contamination risks. These findings highlight the importance of continuous monitoring and further investigation into the transfer dynamics of contaminants during rice processing to ensure the safety of the final product.