Attachment 2 a Risk Profile of Dairy Products in Australia Appendices 1
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2-06 22 March 2006 Attachment 2 A Risk Profile of Dairy Products in Australia Appendices 1-6 DRAFT ASSESSMENT REPORT PROPOSAL P296 PRIMARY PRODUCTION AND PROCESSING STANDARD FOR DAIRY RISK PROFILE OF DAIRY PRODUCTS IN AUSTRALIA VII APPENDICES 1. IMPACT OF PROCESSING ON DAIRY PRODUCT SAFETY 1.1 Milk and cream 1.2 Cheese 1.3 Dried milk powders 1.4 Infant formulae 1.5 Concentrated milk products 1.6 Butter and butter products 1.7 Ice cream 1.8 Cultured and fermented milk products 1.9 Dairy desserts 1.10 Dairy based dips 1.11 Casein, why products and other functional milk derivatives 1.12 Colostrum 2. EPIDEMIOLOGICAL INFORMATION ON OUTBREAKS OF FOODBORNE ILLNESS ASSOCIATED WITH DAIRY PRODUCTS 3. OCCURRENCE OF MICROBIOLOGICAL HAZARDS ASSOCIATED WITH DAIRY PRODUCTS 4. CONSUMPTION FIGURES OF DAIRY PRODUCTS FOR AUSTRALIAN CONSUMERS 5. HAZARD IDENTIFICATION/HAZARD CHARACTERISATION OF PATHOGENS 5.1 Aeromonas Spp. 5.2 Bacillus cereus 5.3 Brucella Spp. 5.4 Campylobacter jejuni/coli 5.5 Clostridium Spp. 5.6 Coxiella burnetii 5.7 Corynebacterium ulcerans 5.8 Cryptosporidium 5.9 Enterobacter sakazakii 5.10 Pathogenic Escherichia coli 5.11 Listeria monocytogenes 5.12 Mycobacterium bovis 5.13 Mycobacterium avium subsp. paratuberculosis 5.14 Salmonella Spp. 5.15 Shigella Spp. 5.16 Staphylococcus aureus 5.17 Streptococcus Spp. 5.18 Yersinia enterocolitica 6. PREVIOUS RISK ASSESSMENTS ON MICROBIOLOGICAL PATHOGENS IN DAIRY PRODUCTS 7. CHEMICAL RISK ASSESSMENT FRAMEWORK 8. REGULATORY FRAMEWORK FOR AGRICULTURAL AND VETERINARY CHEMICALS 9. MAXIMUM RESIDUE LIMITS 10. CHEMICAL RESIDUES MEASURED IN BOVINE DAIRY PRODUCTS 11. REGISTERED ANTIMICROBIAL AGENTS 12. REVIEW OF ANTIBIOTICS AND ANTIMICROBIAL RESISTANCE IN AUSTRALIA 13. FEEDS AND FEED COMMODITIES FOR CATTLE 14. THERAPEUTIC PRODUCTS USED IN GOAT PRODUCTION AND REGISTRATION STATUS FOR USE IN GOATS 226 184 APPENDIX 1 Impact of processing on dairy product safety 1.1 Milk and cream 1.1.1 Description Milk is defined in Standard 2.5.1 of the Food Standards Code as “the mammary secretion of milking animals, obtained from one or more milkings for consumption as liquid milk or for further processing but excludes colostrums”. In this Dairy Risk Profile, milk refers to the fluid form of milk derived from cow, sheep, goats, buffaloes, camels, horses and other mammalian animals, and available for human consumption through retail sale in Australia. Milk may be sold in many forms, including whole milk, skim milk, low-fat milk, flavoured milk and other modified milks. Some of these products require the removal of the fat portion as cream. Under Standard 2.5.2, cream is defined as “a milk product comparatively rich in fat, in the form of an emulsion of fat-in-skim milk, which can be obtained by separation from milk”. Cream is produced from whole milk by skimming or other separation means. Milk is subjected to a range of processing operations before being sold. Typical processes include standardisation or formulation of milk, which may include: separation steps such as filtration, centrifugation, and sometimes clarification; homogenisation; and various forms of heat treatment such as thermisation, pasteurisation, sterilisation and UHT (ultra-high temperature) processing. The key processing operations are shown in Figure 1. Dairy animal husbandry Milking, cooling and refrigerated storage Transport to processing plant Milk receival and testing Cold storage Standardisation or formulation Homogenisation Homogenisation and pasteurisation and UHT Chilling Packaging and storage Distribution 185 Figure 1: Indicative processing of fluid milk and cream products Figure 1 simplifies the major steps in the processing of liquid milk products. The raw milk for low fat, skim milk and modified milk products is subjected to centrifugal separation to remove some of the fat phase. Flavoured milks have the addition of flavours and colouring agents, which are sometimes added post-pasteurisation, while ultra-high temperature processing (UHT) results in milk products which are shelf-stable and do not require refrigeration or chilling. The cream that is separated from whole milk may be used in the production of liquid cream products, butter, and anhydrous milk fat. The cream may be subjected to additional processes including vacuum pasteurisation, which involves heat treatment and deodorisation of the fat. 1.1.2 The Microbial Flora of Milk The microbial status of raw milk is influenced by various factors associated with milk production on farm. These factors impact on both the numbers of microorganisms present in raw milk and the type of bacterial flora. Generally, few bacteria are present in milk drawn from the udder of a healthy animal, but bacteria may enter milk if it is drawn from an infected animal or if it is contaminated by unhygienic milking practices and poor milk handling. Bramley and McKinnon (1990) identified the main groups of microorganisms comprising the microflora of raw milk as follows: Table 1: Major flora of raw milk Group Incidence (%) Micrococci e.g. Micrococcus, Staphylococcus 30-99% Streptococci e.g. Enterococcus 0-50% Asporogenous Gram +ve rods e.g. Corynebacterium, Microbacterium, etc <10 Gram –ve rods e.g. Klebsiella, Escherichia, Enterobacter, Pseudomonas, etc <10 Sporeformers e.g. Bacillus spores or vegetative cells <10 Miscellaneous e.g. Streptomycetes, yeasts, moulds, etc <10 Various pathogenic microorganisms may also be associated with raw milk. These include organisms shed by an infected animal (pathogens will predominate in milk from mastitic cows) or organisms that enter the milk from contaminated equipment and poor milking hygiene. Surveys of raw cow’s milk, mainly conducted overseas, have detected Aeromonas spp., B. cereus, Brucella spp., Campylobacter spp., Coxiella burnetii, pathogenic E. coli, L. monocytogenes, Mycobacterium spp., Salmonella spp., S. aureus, Streptococcus spp. and Y. enterocolitica. Raw goat’s and sheep milk have been shown to contain Aeromonas spp., Brucella spp., Campylobacter spp., pathogenic E. coli, L. monocytogenes, Mycobacterium spp., S. aureus and Y. enterocolitica. In Australian surveys, potential pathogens detected in raw cow’s milk have included Aeromonas spp. and S. aureus. Detections in raw goat’s milk have included E. coli, L. monocytogenes, and Y. enterocolitica (Appendix 3). 186 Overseas surveys of cream have detected Aeromonas spp. and Shigella spp., while Australian surveys have indicated the presence of E. coli and Salmonella spp. (Appendix 3). 1.1.3 Effect of milk processing on the growth and survival of microbial pathogens To minimise microbiological activity, raw milk harvested from animals at dairy farms is cooled rapidly to temperatures of 7°C or lower within 2 hours of milking (White, 2003). In Australia, milk is cooled to 4°C. After a period of storage on farm, raw milk is transported by insulated bulk milk tankers to milk processing facilities. Traditionally, milk transportation was conducted in the early part of the day to minimise the impact of heat from sunlight, but nowadays milk collection may occur at any time during the day or night and insulated tankers minimise the impact of ambient temperatures on milk. When the raw milk reaches the processing plant, it is sampled and its status assessed by measuring parameters such as temperature, presence of antibiotics, somatic cell counts, standard plate count, bactoscan, fat content, etc. Information on the microbial content of milk is helpful in judging its sanitary quality and the conditions of production, and is used in payment schemes that reward producers of high quality raw milk. The raw milk is normally transferred to large insulated storage silos and maintained at temperatures of less than 4°C before decisions are made about how it will be processed. Milk for drinking is usually homogenised, a process where the milk fat globules are physically reduced in size and then remain in suspension throughout the milk for long periods of time. In unhomogenised milk, fat globules may coalesce to form a compact cream layer. Homogenisation has little effect on the microbiology of fluid milk, but may predispose the fat to oxidation reactions that affect its quality, hence homogenisation occurs simultaneously with pasteurisation. Practically all drinking milk in Australia is homogenised, preventing the milk from separating and giving it a more uniform colour. Pasteurisation involves heat treatment of milk with the aim of ensuring a microbiological safe product, as well as to extend the shelf-life during refrigerated storage. Milk pasteurisation may be carried out either as a batch holding heat treatment or a high-temperature-short-time (HTST) heat treatment. The batch process involves low-temperature-holding for 30 minutes or longer at temperatures of approximately 63°C. This has been largely replaced by HTST treatment at temperatures of ≥72°C for at least 15 seconds. The Food Standards Code states: Milk must be pasteurised by: (a) heating to a temperature of no less than 72°C and retaining at such temperature for no less than 15 seconds and immediately shock cooling to a temperature of 4.5°C; or (b) heating using any other time and temperature combination of equal or greater lethal effect on bacteria;Where dairy products contain elevated levels of fat or solids, the specified temperature is increased to compensate for the protective effect of these fat and solids on microorganisms. These specifications are sufficient to reduce populations of vegetative bacterial pathogens to a level considered safe for public health. The pasteurisation process used by processors of milk often employs temperatures and times in excess of 72°C for 15 seconds. This is to provide a higher margin of safety and to extend the shelf-life of liquid milk. 187 From survey data on industry pasteurisation practices in Australia HTST treatment of milk for liquid milk products was mostly in the range of 74-78°C for 15-30 seconds1. Pasteurisation processes for cream products utilise higher temperatures because of the protective effects of fat on microorganisms. From survey data on industry pasteurisation practices in Australia the pasteurisation temperatures and times for table cream varied in the range from 75-80°C for 20-30 seconds2.