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Animal coats in carcass contamination
Animal coats are a significant source of microbial contamination of the carcass (Hudson, Mead & Hinton, 1998). Many countries apply a subjective ordinal visual rating system to food animals presented for slaughter, categorizing animals by degree of coat cleanliness (Small, Wells-Burr & Buncic, 2005). Animals assessed as clean are normally processed for human consumption. However, research on cleanliness of the animal coat has demonstrated that visually clean cattle often carry pathogens, for example, E. coli O157:H7 and Salmonella spp (Avery et al. 2002; Small et al., 2002) confirming that hides should always be considered as posing a serious risk to meat safety. All operations during slaughter and dressing of food animals that involve penetration of the skin such as penetrative stunning of animals, also in South Africa, carry a risk of introducing pathogenic bacteria from the skin onto edible parts of the animal as penetrative stunning pistols are not sterilized between animals (Buncic, McKinstry, Reid & Anil, 2002). Buncic et al. (2002) demonstrated in their study investigating the role of the penetrative pistol in spreading microbial contamination to edible parts and the abattoir environment that microbial contamination association with penetrative stunning can spread from the brain to the edible parts of the same animal, including muscles via the blood circulation. In addition, Buncic et al. (2002) observed that positive detection of the marker organisms in their study varied between individual animals, between types of tissues/organs and between types of the marker organism.
The authors then speculated that the variation could have been due to factors including: (a) differences in stunning-associated damage of the brain blood vessels between individual animals, which could cause different counts of the bacteria to enter the blood circulation, (b) differences in post-stunning rate and/or duration of the heart activity between individual animals, which could cause different transfer of bacteria through the animal bodies, and (c) difference in volume/mass of blood, tissue and organs between individual animals, which could result in different “dilution” factors for the counts of the marker organisms. Blood and liver were most commonly contaminated (in 90% of animals), followed by the lungs and spleen (in 80% of animals), deep muscle (in 20% animals) and on the carcass surface (in 50% of animals). In this study penetrative stunning was also positively linked to the spread of contamination to the environment. The marker organisms were present in protective clothing samples collected from the slaughtermen conducting the stunning of animals and samples collected from the pelt (leg, breast and shoulder) of the stunned animals.
Buncic et al. (2002) further demonstrated that penetrative stunning could spread contamination to subsequently stunned animals if equipment was not cleaned and sterilized between animals.
Small et al. (2005) evaluated the effects of pre-skinning hide decontamination on carcass contamination. They recorded a positive correlation between the microbial loads on skinned carcasses with those on the hide of the same animal. They concluded that pre-skin hide decontamination would reduce overall microbial loads introduced into the slaughter line environment and onto the dressed carcasses, and hence, improve meat quality and safety.
Effect of line speed on carcass hygiene
According to Roberts (1980), line speed may have serious implications in relation to carcass contamination. The faster the line operates, the more opportunities there are for mistakes to be made and hence for more contamination to occur. The relationship between line speed and carcass contamination is influenced by a large number of factors including operator fatigue, knife skills, length of working day, levels of boredom and the presence or absence of proper management structures such as HACCP. The most important aspect is whether or not the operatives have sufficient time to carry out their jobs. In some countries, the speed line is regulated by the number of carcasses that an inspector can examine in an hour (Roberts, 1980).
Abattoir workers
The hygienic status of dressed carcasses is largely dependent upon the general slaughterhouse hygiene and the skills of the workers (Mothershaw, Consolacion, Kadim & Ahmed, 2006; Rahkio & Korkeala, 1996. The interviews conducted by Mothershaw et al. (2006) revealed that 89% of workers at the abattoir where they conducted their study had no training in safe food handling, and as a result, personal hygiene standards were also found to be low. Furthermore, Desmarchelier, Higgs, Mills, Sullivan and Vanderlinde (1999) showed that the incidence of coagulasepositive staphylococcus (CPS) at one of the abattoirs in their study increased by 33.5% after evisceration compared to counts enumerated before evisceration. This increase corresponded to the heavy contamination of the hands of workers performing the evisceration task. Desmarchelier et al. (1999) found that the hands of 75% of workers at trimming of visible contamination step were contaminated with CPS. Therefore, Desmarchelier et al. (1999) concluded that workers’ hands could have been a source of carcass contamination with CPS, hence a large increase in counts after chilling for 72 hours. The significance of workers’ contribution to carcass contamination was also illustrated by Wagude (1999) who observed a great improvement in the microbiological quality of beef after training workers on sanitation, personal hygiene and hand washing techniques.
HYGIENE MANAGEMENT SYSTEMS AT ABATTOIRS
Cattle slaughter operations, such as bleeding, dressing and evisceration expose sterile muscle to microbiological contamination that is present on the skin, in the digestive tract and in the environment (Gill & Jones, 1999; Sofos et al., 1999). With a view to reducing the risks associated with the presence of food pathogens on carcasses, the need to achieve standardized control systems, and the desire to access international markets, the South African meat industry approached the government for assistance. The DoA co-ordinated a task team representing South African Meat Industries Company (SAMIC), RMAA and GPDoA: VPH. This task team developed the Hygiene Assessment System (HAS) based on the United Kingdom’s evaluation/audit system. HAS became a mandatory requirement for all registered abattoirs in 2000 upon its inclusion in the Meat Safety Act 40 of 2000 (RMAA, 2008).
CHAPTER ONE: INTRODUCTION AND PROBLEM STATEMENT
1.1 Introduction
1.2 Problem statement
CHAPTER TWO: LITERATURE REVIEW
2.1 E. coli O157:H7, a food pathogen
2.2 Recorded E. coli O157:H7 associated foodborne outbreaks
2.3 Characteristics of E. coli O157:H7
2.4 Transmission of E. coli O157:H7
2.5 Classification of Family Pseudomonadaceae
2.6 Classification and physiology of Lactic Acid Bacteria
2.8 Sources and control of contamination of meat and meat products
2.9 Hygiene management systems at abattoirs
2.10 Common control measures used at HAS alone and HAS and HACCP abattoirs in South Africa
2.11 Competition between spoilage and food pathogens during beef storage
2.12 Bacterial interactions on meat
2.13 Influence of storage conditions of meat on its microbiota
2.14 Hypotheses
2.15 Objectives
CHAPTER THREE: EFFECT OF HYGIENE AND SAFETY MANAGEMENT SYSTEMS ON THE MICROBIOLOGICAL QUALITY OF FRESH BEEF
ABSTRACT
3.1 Introduction
3.2 Materials and methods
3.3 Statistical analysis of the results
3.4 Results
3.5 Discussion
3.6 Conclusions
CHAPTER FOUR: SURVIVAL OF E. COLI O157:H7 CO-CULTURED WITH DIFFERENT LEVELS OF PSEUDOMONAS FLUORESCENS AND LACTOBACILLUS PLANTARUM ON FRESH BEEF
ABSTRACT
4.1 Introduction
4.2 Materials and methods
4.3 Results
4.4 Discussion
4.5 Conclusions
CHAPTER FIVE: GENERAL DISCUSSION
5.1 Review of methodology
5.2 Isolation of Enterobacteriaceae from chilled beef carcasses
5.3 Isolation of E. coli O157:H7 from beef carcasses
5.4 Isolation of Salmonella spp. from chilled beef carcasses
5.5 Sample preparation for E. coli O157:H7 survival studies from artificially contaminated beef loins
5.6 Effect of HAS alone and HAS combined with HACCP on the microbiological quality of fresh beef
5.7 Survival of E. coli O157:H7 co-cultured with different levels of Pseudomonas fluorescens and Lactobacillus plantarum on fresh beef
5.8 Areas for future research
CHAPTER SIX: CONCLUSIONS AND RECOMMENDATIONS
CHAPTER SEVEN: REFERENCES
