Characterisation of non-toxigenic Clostridium spp. strains, to use as surrogates for non-proteolytic Clostridium botulinum in chilled food challenge testing

•Non-toxigenic clostridia strains are characterised as surrogates for C. botulinum.•These clostridia strains are safer to handle and work with than C. botulinum.•A surrogate cocktail could be used in chilled food challenge tests for growth.•Screening studies using surrogates could reduce the number of mouse bioassays.•Surrogates could also be used to study thermal inactivation processes.

Under many of the conditions studied, a two-strain cocktail of non-toxigenic Clostridium spp. was found to be suitable as a surrogate for non-proteolytic Clostridium botulinum, and has the potential for use in chilled food challenge tests measuring growth. Non-toxigenic surrogates could also be used in thermal process screening studies.