Abstract
The study aimed at measuring changes in chemical composition of maize kernels due to Aspergillus flavus Link. and Fusarium verticillioides (Sacc.) Nirenberg infection. The samples of maize kernels were incubated at 28 °C for 7, 14, 21, and 28 days. The samples were analysed for mycotoxin, moisture, crude fat, crude protein, crude ash, and crude fibre. Maize kernels inoculated with A. flavus and F. verticillioides exhibited a significant decrease in crude fat. Aflatoxin B1 (AFB1) contamination increased in maize kernels inoculated with A. flavus, and fumonisin B1 (FB1) in kernels inoculated with F. verticillioides. Crude ash and crude fibre content showed no changes. Incubation time significantly affected AFB1 and FB1 contamination levels, moisture, crude fat, and crude protein contents. AFB1 and FB1 contamination were significantly correlated with crude fat degradation. The tested strains had similar deteriorative effects on maize kernels. The significant changes in the proximate composition were only observed in maize kernels with mycotoxin contamination above the regulatory limit of 10 µg kg−1, thus not fit for human consumption.
Highlights
Maize is highly susceptible to fungal infection
The moisture content (MC) of the maize kernels was adjusted to 205 g kg−1 dry matter (DM) by soaking samples in distilled water for 2 hours
The highest increase in MC was observed in samples inoculated with A. flavus (205 to 289 g kg−1, Table 1)
Summary
Maize is highly susceptible to fungal infection. the quality of the maize kernels deteriorates (Begum et al, 2013). Fungal infection in grains is associated with losses in carbohydrates, proteins and lipids while moisture content and free fatty acid increase. Fungi produce hydrolytic enzymes including peroxidase, amylase, pectinases, proteases and lipases. These enzymes degrade biochemical components such as fats, protein, and carbohydrates leading to the loss of dry matter (Begum et al, 2013). Bhattacharya and Raha (2002) reported a decrease in carbohydrates and fat content in maize kernels and soya beans due to postharvest fungal infection. Kakde and Chavan (2011) concluded that Aspergillus flavus was responsible for the maximum depletion of fat content and reducing sugars in safflower, soya bean and sesame These enzymes degrade biochemical components such as fats, protein, and carbohydrates leading to the loss of dry matter (Begum et al, 2013). Bhattacharya and Raha (2002) reported a decrease in carbohydrates and fat content in maize kernels and soya beans due to postharvest fungal infection. Jain (2008) reported a rapid increase in free fatty acids in damaged grains due to fungal infestation. Embaby and Abdel-Galil (2006) observed a reduction in carbohydrates, sugars and crude fat due to Fusarium in legume grains. Kakde and Chavan (2011) concluded that Aspergillus flavus was responsible for the maximum depletion of fat content and reducing sugars in safflower, soya bean and sesame
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