From vegetable food waste to earthworms as novel food/feed: microbial hazard identification

From vegetable food waste to earthworms as novel food/feed: microbial hazard identification D. Tedesco, J. Parisi, M. Castrica and C. Balzaretti Department of Health, Animal Science and Food Safety, University of Milan, Via Celoria 10, 20133 Milano, Italy; doriana.tedesco@unimi.it Earthworms grown on fruit and vegetable waste can be a future alternative, and sustainable, food/feed source, contributing to waste disposal efficiency, responding to global food demand and reducing GHG (Greenhouse Gases) emission. In this study, we evaluated the earthworms (Eisenia foetida) when reared on food vegetable waste, in order to establish critical limits and critical control points (HACCP) of this rearing system, for the prevention, elimination or reduction of identified microbial hazards. Our aim is to verify the safety of these new food / feed, regarding the presence of pathogenic micro-organisms, other than those provided by the reg. (EU) 2073/2005. In our first HACCP evaluation, the earthworms from this rearing process were characterized by levels of microflora ranged above common benchmark and threshold values to be considered a safety product. In this step, continuing on the HACCP system and Critical Control Point (CCP) identification, we evaluated the microbial contamination of earthworms (Eisenia foetida) reared on food vegetable waste that belong to the category ‘fruit and vegetables to consume raw, uncut and unprocessed’. The earthworms samples from this rearing process were analyzed according to AFNOR and ISO methods for Total Bacterial Count, Enterobacteriaceae, coagulase-positive Staphylococci, Bacillus cereus, Total Coliforms, Listeria Monocytogenes, sulphite reducing Clostridia, Escherichia coli and Salmonella spp. Bacterial counts were expressed as Log cfu/g sample. Conforming to the Reg. (EU) 2073/2005, Salmonella spp. and Listeria monocytogenes were absent in 25 g samples; Escherichia coli and coagulase-positive Staphylococci were below the detection limit (1 log cfu/g). Nevertheless, samples were characterized by unsatisfactory levels of Enterobacteriaceae and total coliforms, whereas Bacillus cereus and sulphite reducing Clostridia were slightly higher than the acceptable safety range. Considering that fruit and vegetable waste substrate, represents the primary source of microbiological contamination for earthworms and consequently a relevant CCP, other detailed studies are needed to reduce the hazard and guarantee the safety of this new nutritional source.