Growth and production of toxin of clostridium botulinum type e in rainbow trout under various storage conditions

Abstract

Rainbow trout (Oncorhynchus mykiss) were inoculated with 3 to 4 log 10 spores per g of fish of a mixed pool of four strains of Clostridium botulinum type E (Beluga, Minnesota, G21-5, and 070). The trout were vacuum-skin packaged with either oxygenbarrier or oxygen-permeable films. Trout packaged with oxygenpermeable film were stored at 4°C for 21 days, while trout packaged with oxygen-barrier film were stored either at 4°C for 21 days or at 10°C for 15 days. Storage at 10°C was used to simulate commercial temperature abuse. Clostridium botulinum outgrowth was determined by a most-probable-number (MPN) method using (tryptone peptone yeast extract glucose trypsin) anaerobic broth. Toxin production was evaluated using a mouse bioassay. Psychrotrophic and anaerobic populations increased with time regardless of packaging type. After 6 days at 10°C, botulinum toxin was detected in the packaged trout; however, the fish was noticeably spoiled before that time. No botulinum toxin was detected in trout packaged with either barrier or permeable films and stored at 4°C for 21 days, although the product was considered spoiled by day 12. Copyright © International Association of Milk, Food and Environmental Sanitarians.