Impact of storage environment on respiration, dry matter losses and fumonisin B1 contamination of stored paddy and brown rice

Abstract

The objective of this study was to compare the effect of different storage moisture conditions (0.90 and 0.95 water activity, aw) and temperatures (25, 30 °C) on (1) respiration rates (CO2; R), (2) dry matter loss (DML) of paddy and brown rice, (3) inoculation of both rice types with Fusarium verticillioides under these storage conditions on R, DML, and (4) effects on fumonisin B1 (FB1) contamination of these rice types. There was an increase in temporal CO2 production with wetter and warmer conditions in naturally contaminated rice. Higher R and consequently, percentage (%) DML were generally observed for brown rice (up to 21%) while in paddy rice this was only up to 3.5% DML. The FB1 production in paddy rice was low and similar in all treatments regardless of aw × temperature conditions. In the dehusked brown rice there were higher levels of contamination with FB1, with a maximum at 0.95 aw and 25 °C. A significant correlation between %DMLs and FB1 contamination was obtained (R=0.7454, P<0.01). These results suggest that monitoring of CO2 may provide an early indication of fungal activity in moist rice and help in evaluating the relative risk of spoilage and potential for mycotoxin contamination.