Microbiological safety in pistachios and pistachio containing products

Abstract

Pistachio nuts, including salted pistachios, unsalted pistachios and shelled pistachios which are ready to eat foods, recently appeared as possible sources of infection with foodborne bacteria besides the high levels of aflatoxins. Several types of pistachio and pistachio containing products were evaluated for the presence of Staphylococcus aureus, and Salmonella spp; also aerobic mesophilic bacteria, coliforms and yeasts and moulds, were enumerated. The analysis was performed in three different sampling times. Aflatoxins levels were determined using a commercial kit. Unsatisfactory levels of mesophilic, coliforms and yeasts and moulds counts were obtained in 55%, 22% and 15% of the samples respectively. Samples contained ≥105 CFU/g moulds were tested for aflatoxins. For Salmonella detection, conventional methods were used, and all the suspected colonies on two different selective media were confirmed biochemically. Isolates that biochemically identified as Salmonella spp. were confirmed using multiplex PCR which included primers for 16S rDNA (bacteria control), invA (for Salmonella spp.) and STM4057 (for Salmonella enterica subsp. enterica). Due to presence of 16S rDNA bands only or other bands not explained by any of used primers in multiplex PCR patterns, some isolates were sequenced. Sequencing results revealed that those isolates included Klebsiella pneumonia and Salmonella sp. These results reveled that pistachios and pistachio products can be a possible source of infection with foodborne bacteria and aflatoxins contamination.