Microbiological analysis of raw edible insects

Abstract

Relatively little is known about the microbiological quality of edible insects. In Germany, living insects are also bought from pet shops, rededicating thus a feedstuff to a foodstuff. A preliminary survey was conducted to assess the microbiological quality of these animals. Samples of raw insects ( Acheta domesticus, Gryllus assimilis, Gryllus bimaculatus, Locusta migratoria, Blabtica dubia, Galleria mellonella, Chilecomadia moorei, Pachnoda marginata, Tenebrio molitor, Zophobas atratus, and Apis mellifera) from pet shops were analysed using classical food hygiene parameters (total aerobial mesophilic bacterial count (TBC), Enterobacteriaceae count (EC), staphylococci (SC), bacilli (BC), yeasts and moulds counts (YMC), salmonellae, Escherichia coli, and Listeria monocytogenes). They were also inoculated on blood agar for specific microbial identification. Merged samples were taken from living animals (n=39), dead ones (n=7), and the bedding material (n=16) of the boxes they were sold in. Geometric means per species variedbetween 5.7 and 7.5 (TBC), 5.5 and 7.3 (EC), ≤6.1 (SC), ≤5.6 (YMC), and 3.5 and 7.2 lg cfu/g (BC), each displaying a individual microbial pattern. Dead animal values ranged above those of living ones, while bedding materials’ values could be higher or lower. From blood agar plates, coagulase-negative staphylococci, Enterobacteriaceae (typically Proteus spp. and Serratia liquefaciens), pseudomonads and fungi (e.g. Candida albicans, Issatchenkia orientalis, Geotrichum spp.) were isolated. All samples were free of salmonellae, E. coli, L. monocytogenes, and Staphylococcus aureus, complying thus with the food hygiene criteria recently issued by Belgium and the Netherlands. Process hygiene criteria however were not met entirely due to elevated TBC and EC. These high bacterial counts and the presence of many (opportunistic) pathogenic and spoiling agents found also typically in other foodstuffs create the need to heat insects thoroughly before consumption.