Post-harvest storage of corn: effect of beginning moisture content on mycoflora and fumonisin contamination

Abstract

The effect of storage on mycoflora profile was monitored bimonthly in 36 corn (Zea mays L.) samples, dividing the same sample into groups dried to 11 and 14% moisture content (1008 analysis). These groups were further subdivided based on the initial total count (moulds and yeasts) up to 104 CFU g-1 (12 samples, range 1.6 × 104 to 9.0 × 104, mean 3.8 × 104 CFU g-1) and up to 105 CFU g-1 (24 samples, range 1.0 × 105 to 5.0 × 105, mean 2.7 × 105 CFU g-1). In the corn group dried to 11%, the fumonisin content was analysed at the initial stage (freshly harvested) and at the end of 12-month storage. Fusarium spp. and Penicillium spp. prevailed at the freshly harvested stage (100%), maintaining this profile throughout 12 months, in corn dried to both 11 and 14%. Cladosporium spp., Aspergillus spp. and Phoma spp. were also detected at lower frequencies during the storage. Fusarium spp. and the total fungal colony count during 12-month storage carried out with samples dried to 11 or 14% moisture content were statistically evaluated using ANOVA for randomized complete block design. The correlation between storage time and Fusarium spp. and total fungal colony count data was analysed by Pearson's correlation test. There was no difference in Fusarium spp. and total counts in the 104 CFU g-1 initial total count group throughout the storage time (p < 0.05). There was a negative correlation between fungal population and storage time (p < 0.05) in the 105 CFU g-1 initial total count group. Fumonisins were detected in all freshly harvested corn, at a mean concentration of 9.9 ± 6.0 µg g-1 (range 0.74-22.6 μg g-1). These values did not change in the 12-month stored corn (mean of 9.9 ± 5.8 μg g-1, range 0.81-23.7 μg g-1). These post harvest data indicated the importance of moisture content at the crop harvesting/predrying stage to control fungal growth and further fumonisin production.