Micromycetes contaminating nuts used for food

Abstract

Nuts are one of the  most delicious and nutritious foods, but due to the  extremely high fat, protein and low water content they are quite refractory to spoilage by microorganisms. In this study a wide range of microorganisms was recorded. The samples were collected from 6 different markets in Kaunas, Lithuania. The  moisture content of nuts was determined by drying the samples in an oven at 103 (±2) °C temperature for 6 hours. Dilution plating (a surface-spread method) was used for colony counting. The  analyses of nut samples revealed that imported nuts were quite intensely contaminated with propagules of various fungi species. The  moisture content in the  nuts varied in dependence of their type and acquisition place. The  highest moisture content was observed in walnuts, 13.93%, while almost twice less in pistachio and hazelnuts, 6.38 and 6.76%, respectively. The least number of colony forming units (cfu) of fungi was detected in hazelnuts (9.11 × 10³ cfu/g) followed by peanuts (11.46 × 10³ cfu/g). In contrast, walnuts (20.90 × 10³ cfu/g) represented the  highest infections of fungi. A  total of 8 different fungal genera (Aspergillus  spp. Acremonium  spp., Cladosporium spp., Fusarium spp., Mucor spp., Rhizopus spp., Paecilomyces spp., and Penicillium spp.) and 16 species were isolated. Aspergillus, Mucor and Penicillium genera were more frequently detected than other genera of fungi. Aspergillus spp. was found in the most investigated nut samples. The greatest diversity of micromycetes was detected in hazelnuts and walnuts.