Mycology and spoilage of retail cashew nuts

Abstract

Thirty-two samples of retail cashew nuts from Lagos, Nigeria were examined on two media. The pH
values (5.1-6.3) of all the samples were conducive for fungal growth and mycotoxin production.
Moisture content levels ranged between 4.1 and 6.8%. Fifteen samples had moisture contents up to or
above 5.8%, the highest level estimated to be ‘safe’ for the storage of the nuts. Fourteen fungal
species, mostly toxigenic and belonging to 5 genera were isolated. Seven species were from genus
Aspergillus, 3 from Penicillium, 2 from Rhizopus and one each from Mucor and Syncephalastrum. The
most predominant isolates were: A. niger, A. restrictus, A. flavus, A. fumigatus and Aspergillus sp. The
mean and range of total fungal counts (CFU/g) in samples were: 3,368 (180 to 16, 300). At acceptable
fungal levels of 103
and 104
/g, only 14 and 28 samples, respectively, were deemed fit for human
consumption. All the species recovered induced detectable loss in weights of the milled nuts, though
to varying extents and would be expected to cause considerable spoilage of the nuts.