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Task 1.1:Conceptual visualisation of bioagents in food chains.
Decontamination: a way to reduce Salmonella
prevalence in the slaughtered swine carcass?
Marianne Halberg Larsen and Hanne Ingmer
Faculty of Life Sciences, University of Copenhagen
INTRODUCTION
QUESTIONS FOR YOU
Control of Salmonella on pork demands strict and continuous adherence to good farming,
manufacturing and hygiene practices. In the slaughterhouses, slaughter and dressing should
be performed with a high level of hygiene and according to the HACCP system. This include
control of raw material, prevention of contamination and cross contamination especially during
scalding and evisceration and prevention of risk of multiplication of Salmonella on product and
environment. The Hygiene Regulation (EC No 853/2004) also provided the legal basis to
decontaminate meat also with other substances than water and steam. This have renewed the
development and commercial application of meat decontamination in order to reduce the
numbers of human pathogenic and spoilage bacteria on pork meat. Normally, decontamination
is carried out as the last process in the slaughter line prior to carcass chilling. It has been
estimated that the production cost of hot water decontamination is 0.15 euro per pig (Goldbach
and Alban, Prev. Vet. Med. 2006).
•Decontamination is useful to reduce carcass contamination (1-3 log units) and thus assist
meat processing plants to meet regulatory criteria and protect consumers. As
decontamination results in reductions and not elimination of bacteria, Salmonella reducing
initiatives at pre-harvest and a high level of hygiene during slaughtering is still a requirement
for optimal decontamination results. Decontamination is or should be complementary to
HACCP in improving the microbiological status of carcasses. However,
•With time, new techniques of decontamination may be developed that are more effective in
microbial reductions than the present (ex. 4-5 log units reductions). What is the risk that
decontamination then will be used to mask unhygienic slaughter processes?
•Are there any potential unpredictable risks (variability, long term effects of sublethal
methods, resistance development, potential for post-slaughter decontamination etc) ?
AIM
The aim of this work is to review methods of decontamination of swine carcasses and discuss
advantages and disadvantages.
METHODS
Decontamination technologies include physical and chemical treatments. In the EC, the use of
substances other than water and steam should be authorized before use. Below are listed
examples of decontamination methods.
Thermal decontamination
Hot water (80 °C, 15 sec). Lethal effect: heat and detachment of bacteria.
Hand held steam sucking: to remove visible (manure) dirt with a sucking head and
concurrent disinfect by use of steam.
Ultrasound and steam: (1 sec): lethal effect by the steam; ultrasound promotes the heat
transfer.
Electro thermic decontamination (2-3 sec). In the presence of an electro static field superheated steam condensate on the meat surface.
Pressurized steam (6-8 sec followed by exposure to cold water)
Microbial reductions <1 to 2-3 log units.
Chemical decontamination
1-2.5 % Low molecular organic acids (acetic-, lactid- and citric acid).
Chlorine (20-50 ppm).
Trisodium phosphate (8-12 %, pH > 11.5)
Hydrogen peroxide (5%)
Microbial reductions 1-3 log units.
Alternative decontamination: Natural antibiotics
Bacteriocins (nisin, colicin, cystibiotics).
Primary metabolites (alcohol, organic acid).
Secondary metabolites (toxins and antibiotics).
Multiple hurdle decontamination
Some of the methods have synergistic or additive effects when used in series for example
use of pre-evisceration washing followed by acetic acid solution rinsing followed by warmwater washing.
Images from: www.danishmeat.dk; ing.dk, www.roxytron.com
www.britannica.com
FACULTY OF LIFE SCIENCES
UNIVERSITY OF COPENHAGEN