Effects of hexanal fumigation on fungal spoilage and grain quality of stored wheat

The prevention of fungal spoilage is an essential consideration in wheat storage. Recent studies have revealed that volatile organic compounds (VOCs), possibly with natural fungicidal properties, could be produced from stored wheat grains. In this study, the antifungal effect of hexanal, a main component of VOCs from stored wheat, against spoilage fungi on agar plate and in high-moisture wheat grains were investigated via the gas fumigation method. And the impact of hexanal fumigation on grain quality was evaluated through analysis of the malondialdehyde content, fatty acid values, germination percentages and vigor of 16% and 18% moisture wheat grains fumigated with 1.66, 2.49, and 3.31 mmol/L hexanal vapor. The results of in vitro antifungal experiments on agar plates revealed that the minimum inhibitory concentration and minimum fungicidal (fatal) concentration of hexanal against the five fungi were 4–14 folds and 4–7 folds lower than those of propionic acid, respectively. The fungal spoilage of high-moisture wheat grains inoculated with pure fungal spores and with naturally occurring fungi could be completely inhibited by 1.66 mmol/L hexanal vapor. During 5-week storage of high-moisture wheat grains fumigated with 1.66, 2.49, and 3.31 mmol/L hexanal vapor, the malondialdehyde content in high-moisture wheat grains did not change significantly in all samples, and fatty acid values were slightly higher in 18% moisture wheat than in 16% moisture wheat. The germination percentages and vigor of wheat samples decreased with increased hexanal vapor concentrations and moisture content. These results indicated that hexanal fumigation could be used as an alternative chemical control method to prevent the fungal spoilage of postharvest wheat.