Food safety interventions
The complexity of the pre-harvest, harvest and post-harvest environment of the food supply chain makes it impossible to control all potential sources of microbial contamination, as opportunities for contamination arise at many points. Thus, multiple control measures must be implemted throughout the food production and processing system to ensure the wholesomeness of the final product.
An intervention is a procedure or process - mechanical or human - that significantly reduces the number of pathogens and other microorganisms present on a meat surface, be it a carcase or carcase piece. Using interventions can consequently lead to improvements in shelf life of the fresh or further processed product. Such interventions include;
These technologies and new food safety technologies are continually being developed to help processors to meet the increasingly stringent microbiological criteria that are being applied through the red meat supply chain. Regulatory bodies in a number of countries are accepting the use of intervention technologies as part of the fresh meat processing chain.
For example, the US Food Safety and Inspection Service (FSIS) document ‘E. coli O157:H7 contamination of beef products' (USDA/FSIS, 2002) and accompanying guidance documents were published in the Federal Register in October 2002. Inter alia, they stated that beef slaughter establishments should consider interventions that can be validated and verified as CCPs for reducing or eliminating E. coli O157:H7.
The technologies described in this package have been categorised as physical interventions or chemical interventions, and includes those that are currently available and novel technologies. Each intervention treatment is considered in terms of its microbial efficacy, food safety issues, advantages and limitations of the technology, the current regulatory status, market access and potential customer issues. The food safety technologies described can be applied at one or more points in the supply chain.
The farm or feedlot is the origin of micro-organisms introduced onto carcases during slaughter and dressing. During rearing, numerous factors interact to affect the visual cleanliness and pathogen shedding characteristics of livestock.
Age, coat length, clipping, journey time, feeding and abattoir have been found to influence coat cleanliness, while in Britain sex, breed, transport vehicle floor type, transport vehicle dirtiness and housing prior to transport were not significantly related to visual cleanliness of cattle (Davies et al., 2000).
A lot of interest has been taken in the effects of modifying the diet or feeding probiotics to animals to reduce shedding of pathogens such as E. coli O157, but results are conflicting, probably because of the complexity of the interactions between all the factors involved.
Processing (hide on)
The hide is one of the major sources of carcass contamination. It is important to keep the hides clean prior to skinning, and preslaughter conditions can have a marked impact both on visual cleanliness and microbial load.
Cleaning of the hide may be carried out while the animal is alive, although excessive handling can lead to poor quality meat, or following stunning and sticking, before skinning takes place.
Clipping or shearing of sheep prior to slaughter is widely practised in many countries, the entire fleece being removed in countries where the wool market is good, and in other countries, merely the belly being clipped to reduce the potential for fleece contamination of the carcass during skinning. Full shearing is normally carried out prior to slaughter, but "bellying out" may be carried out on the bleed rail.
Clipping of cattle hides has been advocated as a method of removing visible tag and contamination, and the brisket, belly and hind legs are targeted. This process, when carried out on the live animal involves considerable operator risk, as the animals often kick out and are confined in unsuitable crushes for the purpose. Clipping of cattle immediately prior to slaughter results in numerous short clippings of hair being present on the hide, and these are observed to be transferred to the carcass during the skinning process. Clipping also increases the microbial load recoverable from cattle hide by swabbing, probably as a result of these free short hairs. Singeing of the cattle hide after clipping can give the greatest reductions in recoverable microbial load when compared to washing with warm water (50 °C) or washing with a food-safe chemical solution.
Chemicals can be used, as part of a wash step, to clean the hides before hide removal with the aim of lowering microbial contamination. Compounds such as sodium hydroxide, trisodium phosphate, acidified chlorine (sodium hypochlorite with acetic acid), and phosphoric acid have been evaluated for this purpose. These chemicals do not have a neutral pH, and thus a water rinse is needed to remove the residual chemical and to minimise exposure to risks for plant personnel. There have also been investigations into the use of steam condensing at sub-atmospheric pressures for the treatment of hide-on cattle.
Processing (hide off)
The majority of interventions used in meat processing are applied to the carcass following hide removal. Wiping cloths were used in the past to remove visible contamination and hairs, and when this practice was outlawed, trimming and washing became commonplace. Whole carcass spray washing has continually evolved over time from ambient temperature water, to warm water washes to use of antimicrobial agents, hot water and steam. During dressing, there are numerous opportunities for microbial contamination of the carcass surface, and although excellent hygienic practices in place at modern plants limit the amount of contamination present on carcasses, it cannot be prevented totally. In modern meat production, the major food safety hazards are microbial, and to continue to improve meat safety, a combination of proactive good hygiene measures during dressing and application of intervention technologies will be required.
Chilling itself causes a slight reduction in microbial count on carcasses. Spray chilling is commonly practised in North American meat processing but has had limited uptake in Australia. Some studies have investigated the incorporation of an organic acid and acidified sodium chlorite into a spray chilling system. If an establishment chooses to apply this technology, it must satisfy the Food Standards Codedefinition of a processing aid (FSANZ 2006) i.e. there is no residue on the final product. Also, it should not result in any increase in carcass weight. Ionization of the air, or the use of Ultraviolet (UV) lights in coolrooms may help to reduce the microbial load on the product.
Packaging or retail
Interventions suitable for controlling pathogens in trimmings and ground meat include acidified sodium chlorite and organic acids. Modification of packaging atmospheres can be used to suppress microbial growth, and various additives can be used in meat products to the same end. Carbon dioxide is commonly used in modified atmosphere packs to suppress microbial growth. "Liquid smoke" additives have been advocated in the US, but are prohibited in the EU.
Contamination in processed and ready-to-eat (RTE) meats often occurs after cooking during packing and re-slicing. Post-package food safety technologies such as in-package thermal pasteurisation and irradiation, and formulating meat products with antimicrobial additives are common approaches to control pathogens such as Listeria monocytogenes. The effectiveness of in-package pasteurization in inactivating pathogenic organisms depends upon package size and the roughness of the product surface as well as the time or temperature of the treatment.
Chemical and physical interventions and the stage at which they can be used are below.
Interventions may be applied to the entire carcass or product as a spray, deluge or immersion treatment, or may be applied to small sections as spot treatment. Specific areas to be treated can be identified visually, or using a number of instrumental techniques.
A summary of interventions and summary of options are also available.