Fungal Incidence, Aflatoxin B1, Tocopherols and Fatty Acids Dynamics in Ground and Tree Nuts during Storage at Two Moisture Levels

Any damage in the shell or kernel in field, during transportation, processing, and handling or storage enhances the prospect for fungal invasion in nuts. Processing in any way lowers microbial load of food but nuts are directly consumed so the microbiological characteristics of nuts are of special attention to food manufacturers. The presence of mycoflora also intimidates about the possible incidence of mycotoxins. The objective following the present study was to investigate the effect of different moisture levels on the multiplication of mycoflora, detection of aflatoxin B1 (AFB1), tocopherols and fatty acid profiles in tree and ground nuts during storage. Nuts; walnut, almond, pistachio and peanut, randomly selected from the retail market of Faisalabad, Pakistan were found infected with Aspergillus parasiticus, A. flavus and Penicillium. The moisture content of the nuts was increased to 10 plus or minus 3% and 16 plus or minus 3% to facilitate mould growth. In nuts after a storage period of 12 weeks, the fungi were found growing in all nuts along with considerable aflatoxin B1 production. Peanut samples maintained at 16 plus or minus 3% moisture level showed highest level of fungal contamination as well as that of AFB1 (158.67 mu g kg-1). The tocopherol contents of ground and tree nuts were significantly affected during storage period of 12 weeks. Storage period brought about an increase in free fatty acids in all the analyzed nuts. [copy 2012 Friends Science Publishers