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 × 10<sup>3</sup> cfu/g) followed by peanuts (11.46 × 10<sup>3</sup> cfu/g). In contrast, walnuts (20.90 × 10<sup>3</sup> cfu/g) represented the highest infections of fungi. A total of 8 different fungal genera (<i>Aspergillus</i> spp. <i>Acremonium</i> spp., <i>Cladosporium</i> spp., <i>Fusarium</i> spp., <i>Mucor</i> spp., <i>Rhizopus</i> spp., <i>Paecilomyces</i> spp., and <i>Penicillium</i> spp.) and 16 species were isolated. <i>Aspergillus, Mucor</i> and <i>Penicillium</i> genera were more frequently detected than other genera of fungi. <i>Aspergillus</i> spp. was found in the most investigated nut samples. The greatest diversity of micromycetes was detected in hazelnuts and walnuts.