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Salmonella is the pathogen mostly associated with feed and dry food safety incidents and is a cause of many foodborne outbreaks. In most feed mills conditioning and retentioning systems are installed to improve the pelleting process but also as a kill-step to reduce the microbial load of the feed material. As knowledge about the efficiency of this kill-step at different process conditions in specific feed matrices is lacking, a study was carried out to characterize the inactivation kinetics of Salmonella spp. in broiler feed treated with superheated steam in laboratory scale. First, Salmonella strains commonly associated with feed materials were identified through a literature review. Five Salmonella strains were screened for heat resistance allowing selection of Salmonella Agona as one of the most heat-resistant serotype. Screening of triplicate strains of this serotype allowed selection of S. Agona RA1052 (isolated from animal feed) as the most suitable strain to be used in determination of D- and z-values at selected moisture levels and temperatures in broiler feed. D-values for S. Agona strain RA1052 in broiler feed mash adjusted to 12% moisture, determined within a customized autoclave at 65°C and 85°C, were 178.2 s and 3.1 s, respectively. At 19% moisture, D-values were 81.1 s at 65°C and 0.7 s at 85°C. To perform on-site challenge tests, the surrogate Enterococcus faecium ATCC 8459 (NRRL B-2354) with an equivalent heat resistance to S. Agona RA1052 was selected. The collected data will serve as a basis for the validation of conditioning and retentioning as a Salmonella spp. kill step in pilot and industrial scale.
Steghöfer et al. (Fri,) studied this question.