Inactivation of Clostridium sporogenes spores in fish by-products by a new processing method

Summary

The aim of the study was to determine the hygienization effect of a new processing method intended for category 2 material of fish origin. The method includes storage (≥ 24 hours) and heat treatment (≥ 85 ºC/≥ 25 minutes) of grinded fish material with added formic acid to pH ≤ 4,0. C.sporogenes (ATCC 19404) spores replaced C.perfringens spores in D-value determinations and in examinations of hygienization effect during all phases of the new processing method. In order to minimize interference from the indigenous flora on the analysis of added spores, the fish minces were pre-treated with gamma irradiation (10 kGy). Average D-value for heat treatment of C.sporogenes spores at 85 ºC in fine fish mince adjusted to pH 7 was 580 minutes. Acidification of fish mince with formic acid to pH 4,0 had no inactivation effect per se, but heat treatment at 85 ºC in the presence of the same acid dosage resulted in a markedly reduced D-value; 8,9 minutes. The inactivation effect encountered during the complete new processing method was at least 3 Log10 reductions in fine as well as in coarse fish mince. This is regarded as satisfactory, considering the low incidence of C.perfringens spores in fish silages.