Microbial infestation triggered quality depreciation in stored wheat: Assessment for animal consumption and bioethanol production

Abstract

Five samples of microbially spoilt wheat (SW) grains were investigated for their suitability as food, feed or feed supplement using various biochemical analyses. Microbial infestation had visibly deteriorated grains' appearance that manifested the most in sample SW6 with diminished test weight (15.20g) and starch content (29.16%) against corresponding values of 38.86 g and 60.59%, in reference wheat (NW1). The other spoiled samples however contained reasonable levels of starch ranging from 51.20 to 57.26%. While the contents of nitrogen (1.90–2.24%) and protein (10.83–12.77%) were almost similar in various samples regardless of spoilage, the phosphorus content increased with spoilage from 4400 ppm in sample NW1 to 7200 ppm in SW6. Although the chemical composition testifies the suitability of wheat samples as food but the increased loads of bacteria (6.954–9.204 log cfu/g) and molds (5.477–7.477 log cfu/g), like Aspergillus, Rhizopus, Mucor and Penicillium restrict their suitability for human consumption. Further the presence of aflatoxins and ochratoxin ‘A’ in SW5 (26.7 ppb) and SW6 (213.7 ppb) and the higher concentrations of heavy metal viz. Lead, simply questions their use, even as feed or its supplement. Availability of starch and other essential nutrients in spoilt wheat pointed towards the possibility of its conversion into bioethanol. A hydrolyzed 30% slurry of flour samples SW2-SW5, produced 9.6–11.3% (v/v) ethanol in 24h against 8.3% by NW1, in the absence of any externally added yeast nutrients. This is the first report showing that the microbially deteriorated grains paradoxically resulted in added rate of ethanol production on wheat.