Links among Mold Growth and Rice Kernel Discoloration during Storage of Long-grain Hybrid, Long-grain Pureline, and Medium-grain Rice Cultivars

摘要

The current practice at commercial grain elevators dictates, for U.S. grade 1 rice, nearly zero tolerance for discolored rice. Hence, growers run the risk of severe grain downgrading and loss of revenues due to discoloration issues. The objective of this study was to investigate the links among mold growth and rice kernel discoloration as observed during storage of different rice cultivars. In addition, the study sought to clarify if post-harvest treatment of rice kernels with antifungal agents suchas Natamycin and Salt (sodium chloride) have a significant impact on abating discoloration of the stored rice. Freshly-harvested long-grain hybrid (cv. XL 753), long-grain pure line (cv. Roy J.), and medium-grain (cv. Titan) rough rice were procured andstored at two critical moisture content (MC) levels (16% and 21%, wet basis), and at three temperatures (20°C, 30°C, 40°C) for up to 16 weeks, with samples taken every 4 weeks. Kinetics of mold growth and rice color were determined. The study findingsrevealed a direct relationship between mold growth suppression and discoloration inhibition of stored rice. The observed discoloration rates and microbial growth kinetics were rice cultivar and antifungal treatment dependent. Rice grains treated with salt were significantly less discolored than rice samples treated with Natamycin and blank sample without any antifungal agents (p<0.05). Natamycin and salt inhibited mold growth on stored samples.. The findings from this study are expected to provide growers and processors important guidelines on conditions necessary to maintain rice quality, especially the kernel color ofpopular rice cultivars.