Background:

Tree nuts and dried fruits are very profitable products, highly vulnerable to contamination and subsequent deterioration by molds such as Penicillium spp., Aspergillus spp. and Rhizopus spp. In Mexico, microbial contamination of nuts and dried fruits, particularly of the product sold for bulk consumption, which also has a lax regulation.

Objective:

To study the fungal contamination status of peanuts, pecans, pumpkin seeds, and walnuts from different regions of the country.

Methods:

The moisture content and water activity of 111 samples of peanuts (36), pecans (30), walnuts (12) and pumpkin seeds (33) were measured. Additionally, the different species of molds present in the samples were isolated and identified.

Results and conclusions:

Only some samples, mainly pumpkin seed, were found with mold and yeast contents above what is allowed by Mexican regulations. However, many samples were contaminated with toxigenic mold species, such as Aspergillus flavus, Penicillium spp. and Fusarium spp., as well as other deteriorating molds. Although contamination levels do not seem to be cause for alarm, the sale of nuts in bulk should be monitored and regulated, as there is a potential risk to the consumer if storage conditions are not adequate.

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