Mycoflora, Proximate Composition and Nutritional changes during the Storage of Oryza sativa.

Abstract

The mycoflora and their effects on the proximate and nutritional composition of sundried rice were investigated after a 20-week period of storage. Seven fungi were isolated from the rice sample by dilution, direct plating and washing methods. They were Aspergillus flavus, Aspergillus niger, Absidia spp, Fusarium spp, Rhizopus spp, Saccharomyces cerevisiae and Aspergillus fumigates. The proximate analysis in g/100g revealed that moisture and protein contents increased during storage; moisture from 7.84 to 11.72 and protein from 11.45 to 12.56. While the ash, fat, fibre and carbohydrate contents reduced significantly throughout the storage period: ash (4.51 to 4.25), fat (2.04 to 1.57), fibre 10.27 to 8.52 and carbohydrate (63.72 to 61.28). The minerals (mg/100mg): Na, K, Ca, Mg, Zn, Fe, Mn and P decreased significantly during storage. Na (41.26 to 38.50), K (97.55 to 90.43), Ca (5.36 to 4.25), Mg (3.78 to 3.20), Zn(3.54 to 3.12), Fe (2.18 to 2.00), Mn (1.25 to 1.02) and P (23.33 to 18.55). It was observed that the storage condition and rice nutrients encouraged fungal growth; thereby reducing the seeds weight and affecting their economic value. Some of these fungi produce toxins which are injurious to health when consumed. Hence, depletion of rice nutrients as a result of fungal contaminants would be prevented by storing rice in environmental condition unsuitable for fungal growth.

Key words: Fungi, Proximate, Mineral, Sundried-rice, Stored rice