Comparative study on decontamination of mixed feeds by radicidation and by pelletisation

Abstract

Feed components contaminated with Salmonella act as vehicles in the transmission of these bacteria to animals and hence to meat and poultry. Sanitary improvements in processing, bagging and storage do not always effectively reduce Salmonella contamination rates and therefore ingredients or mixed feed should be decontaminated at the end of processing.Enumeration of Enterobacteriaceae was used to assay the decontamination effect of pelletisation of mixed feed. A working temperature over 80" usually reduced the bacterial count by a factor of lo5; lower temperatures currently used, reduced it by a factor of lo3 only.In similar dose-range-finding tests on decontamination with 6 O C o gamma rays, about 0.5 Mrad were required for reductions in the counts of the most resistant Enterobacteriaceae by a factor of lo5. Survival curves being usually non-linear, 'gross effective dose' had to be used as a parameter. Neither loss of nutritive value nor the occurrence of orally toxic factors was observed when rats were fed for 2 years on a ration containing 35% fishmeal irradiated at 0.8 Mrad.A combination of improved sanitation, pelletising at the highest possible temperature and, if still required, terminal low-dose irradiation of the hermetically bagged material seems, therefore, a promising approach to the manufacture of Salmonella-free feeds.

Effects of processing and gamma irradiation on the microbiological contaminants of a laboratory animal diet

“…Generally the mixed ingredients are heated by direct contact of the meal with steam before being forced through a die to form the pellets. Pelleting has been shown to bring about significant reductions in the numbers of Enterobacteriaceae and Salmonellae contaminating the mixed ingredients (Mossel, van Schothorst & Kampelmacher, 1967;Stott, Hodgson & Chaney, J 975). The reduction in the viable bacterial count achieved by pelleting may be sufficient to satisfy microbiological limits suggested for the numbers and types of contaminants that can be tolerated on diets intended for conventional laboratory stock (Coates, O'Donoghue, Payne & Ward, 1969;Clarke et al, 1977).…”

Microbiological risk assessment in feedingstuffs for food‐producing animals ‐ Scientific Opinion of the Panel on Biological Hazards

“…Heat treatment has traditionally been considered the simplest and most cost effective method of decontaminating feed (Saulmon, 1966;Nape and Murphy, 1971;Williams, 1981). Many studies have demonstrated the potential of heat to reduce microbial contamination (Mossel et al, 1967;Stott et al, 1975;Jones et al, 1991;Veldman et al, 1995). The effectiveness of heat treatment is considerably influenced by the constituents of the feed (especially fats) (Doyle and Mazzotta, 2000;Juneja and Eblen, 2000), available water levels (Liu et al, 1969;Farkas, 2001), level and homogeneity of contamination, the temperature profile achieved through the batch of feed and individual feed particles and the minimum treatment period (Ricke, 2005).…”

THE ELIMINATION OF ENTERIC BACTERIAL PATHOGENS FROM FOOD AND FEED OF ANIMAL ORIGIN BY GAMMA IRRADIATION WITH PARTICULAR REFERENCE TO SALMONELLA RADICIDATION1

“…In the former, doses of ionizing radiation are assessed that will result in the same degree of reduction of cfu counts of Salmonella or Enterobacteriaceae as is achieved in a comparable, conventional mode of processing, particularly a thermal decontamination treatment. This mode of assessing required MPED's of radiation has been successfully applied in studies on the decontamination of mixed feed, where steam pelletisation is such a similar, conventional process (Mossel et al 1967). It is not very feasible for dose assessment of radicidation of fresh meats and poultry, where no analogous thermal mode of processing is available for comparison.…”