Abstract: In order to evaluate the effects of dominant mold stains on rice quality, indica rice grown in Hunan, China was inoculated with different molds isolated from a rice granary and stored at 30 ℃ and 85% relative humidity. The number of molds, chromaticity, fatty acid value, soluble protein content, malondialdehyde (MDA) content, amylase activity, polyphenol oxidase activity and catalase activity were determined at different storage times. The results showed that Aspergillus flavus and Aspergillus niger from rice samples were isolated, both of which exhibited the biggest colony diameter of all isolates, and had a relatively larger effect on the deterioration of rice quality. The colony counts of the two fungal strains were increased by 2.029 and 1.960 (lg (CFU/g)) after the inoculated samples were stored for 10 days, which almost completely covered the surface of rice. The highest browning degree was found in rice inoculated with Aspergillus flavus at the end of the 10-day storage period. At this time, the fatty acid value and MDA content were the highest in rice inoculated with Aspergillus niger (148.93 mg/100 g and 108.82 nmol/g, respectively), followed by that inoculated with Aspergillus flavus (118.48 mg/100 g and 96.47 nmol/g, respectively). Aspergillus flavus had the greatest impact on the activity of polyphenol oxidase. The activity of polyphenol oxidase in rice inoculated with Aspergillus flavus was only 2.444 U/mg on the 10th day. Aspergillus flavus and Aspergillus niger both had the greatest impact on the activity of catalase in rice, and the activity of catalase in the inoculated samples was 0.014 and 0.181 U/mg on the 10th day, respectively. This indicates that more attention should be paid to the prevention and control of Aspergillus flavus and Aspergillus niger in future studies on grain storage safety.

Key words: rice; dominant mold strains; colony diameter; mold count; rice quality