Food Protection Trends - October 2008 - (Page 713)

2. Trace the origins and historical reasons for using 82°C water for disinfection; 3. Outline the current regulatory requirements and guidelines; 4. Describe current industry practice in Australia for knife disinfection; 5. Assess the microbiological efficacy of current knife cleaning regimes; and 6. Describe recent investigations of alternative procedures equivalent to 82°C water in the laboratory and in the plant. THE ROLE OF THE KNIFE The single-bladed knife is used for a range of operations in slaughter and dressing of meat animals. Skin and underlying tissues of the neck are opened by a lateral incision when sheep and calves are slaughtered and exsanguinated; smaller cuts to the throat of pigs open the arteries in the neck to allow bleeding; cattle may be slaughtered by means of a single cut across the throat in religious slaughter operations or by using a vertical incision into the common carotid artery at the thoracic inlet. The skin is opened by incisions that are made so that they do not extend to underlying tissues; opening cuts are developed by so-called “spear cuts” in which the knife is reversed and the hide incised from “inside-out”; the hide is cleared from opening incisions by cuts that separate skin from selvedge; feet, tails and heads are removed by cuts through the joints; the rectum is freed by a circular cut at the anus; an incision is made to open the abdomen and extended by a spear cut; viscera are removed by incisions; bruised and visibly abnormal tissues are excised; fat and surface tissue are trimmed. Traditionally, the entire slaughter and dressing process, particularly of sheep, was done by a single operator – so-called “solo butchery.” Over time, the process was divided into unit operations and the number of operators increased, with each performing fewer operations on animals that were conveyed past each work station. In addition, for some tasks the single-bladed knife was replaced by pneumatically operated knives – oscillating ones for hide clearing and by rotary slicing knives (e.g., Whizard® knife) for trimming. Mechanical equipment was also developed for opening the brisket, for removing feet and heads, and for splitting the backbone of beef carcasses. As meat processing evolved, meat inspection focused, inter alia, on identifying and removing gross pathological lesions and on improving operator hygiene procedures. To prevent transfer of pus, disease agents and other infectious materials from carcass to carcass, the operator was required to “sterilize” the knife between animals by dipping the knife into a bath containing hot water (called a “sterilizer”). However, for the past half century the prevalence of animal disease in developed countries in general, and in those countries that export meat in particular, has gradually decreased. In modern meat production, the meat safety issues are those that do not produce visible pathology of the tissues, such as microbiological contamination with enterohemorrhagic Escherichia coli, Campylobacter spp. or Salmonella spp. As a result, some question the benefit of traditional “organoleptic” or visual meat inspection in controlling meatborne illness (4, 18, 28). Similarly, the potential for invisible microbial contamination to be transferred between carcasses through handling has led to the suggestion that the number of incisions and palpations carried out during traditional inspection should be reduced or that such handling should be stopped altogether. Despite this, the requirement to sterilize knives and other equipment has remained, with the strict enforcement of a minimum temperature of 82°C in sterilizers. The implication of such regulation is that each operator will use a sterile knife on each carcass. However, even a passing consideration of the process will confirm that use of the terms “sterilize” and “sterilizer” is unsustainable from the microbiological viewpoint. Also, it is moot whether “sanitize” or “disinfect”are appropriate terms, because although both imply elimination or reduction to an acceptable level of microorganisms of public health importance, no process criteria have been set for the performance of sterilizers in meat production plants. ORIGINS OF THE 82°C/180°F REQUIREMENT The origins of 82°C (180°F) as the cardinal temperature for meat hygiene are unclear. Although such temperatures as 65°C (cooking), 72°C (pasteurization), and 121°C (sterilization, e.g. canning) and the corresponding treatment times are frequently specified in food microbiology texts (e.g., 16), no corresponding treatment time is provided in meat hygiene texts and no reason is given for using water of 82°C or 180°F. Publications earlier than 1970 refer to a number of equipment cleaning procedures. For example, two publications suggested that water should be heated to 140°F (60°C) for one minute or to 130°F (54.4°C) for 5 minutes to kill low-temperature types of organisms by heat (7, 8). Empey and Scott (8) also recommended that knives and saws should be replaced and subjected to immersion in alkali at 160–180°F (71.1–82.2°C) after twelve carcasses had been processed. Collins (7) commented that the circular saw used for carcass splitting must be periodically wiped clean of all visible blood and sawdust. Past and present staff at the United States Department of Agriculture (USDA) have provided a number of opinions on the origins of the 82°C water requirement (Brewer, R., personal communication). In the 1950s, a Dr. Sloan, working for the USDA Agricultural Research Service (ARS) in Beltsville, Maryland, is believed to have investigated methods of sterilizing carcasssplitting saws. Sloan found that dipping the carcass splitting saws in water at 82°C effectively killed sufficient numbers of organisms to satisfy regulatory requirements. Eventually, 82°C water became the standard for all slaughter floor operations. Unfortunately, there is no evidence of publication of Sloan’s studies, and during changes of administrations at USDA, reports of most of the old investigations pertaining to sanitation were apparently discarded. An alternative explanation given is that the 82°C requirement was based on the heat resistance of a particular zoonotic pathogen (Brewer, R., personal communication). Historically, tuberculosis was still a widespread concern in the 1950s. Water at 82°C may have been chosen as the knife sterilization procedure that would kill Mycobacterium tuberculosis, an important target organism in milk and other foods at that time. Mandatory pasteurization of milk (72°C for 15 s) had been introduced many years before to reduce the risk of contracting tuberculosis from OCTOBER 2008 | FOOD PROTECTION TRENDS 713

Table of Contents Feed for the Digital Edition of Food Protection Trends - October 2008

Food Protection Trends - October 2008 Contents Sustaining Members Perspectives from Your President Commentary from the Executive Director Employee Motivators for Following Food Safety Practices: Pivotal Role of Supervision Knife Sanitizing in Abattoirs: The Effectiveness of Current and Alternative Practices Call for Nominations – 2009 Secretary Call for Awards – IAFP 2009 New Members Updates Industry Products Coming Events Advertising Index Journal of Food Protection Table of Contents Audiovisual Library Order Form Booklet Order Form Membership Application

Food Protection Trends - October 2008

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