![]() Three log reductions gives 0.1 cell / ml (After 1.88 x 3 = 5.64 seconds.Two log reductions gives 1 cell / ml (After 1.88 x 2 = 3.76 seconds).One log reduction will reduce the concentration of C.Note cells and infective doses are taken as equivalent below for brevity. burnetii per ml of milk held at 72☌ and that the D 72☌ for this pathogen is 1.88 seconds then we can detail the effect of log reductions as follows. Assuming we have 100 infective doses of C. One log reduction reduces initial numbers by 10. If MAP is designated as a human pathogen it will become the most thermally resistant, vegetative pathogen in milk and it will be necessary to increase the statutory time-temperature requirements used in pasteurisation. The isolation of MAP from these commercial milk products suggests either a high thermal resistance of this organism and/or post process contamination. Even more concerning, is that significant concentrations of MAP have been isolated from commercial powdered infant milk formulae. MAP has been isolated from commercial calf replacers (CMRs) suggesting that feeding CMRs to calves may constitute a method of horizontal transfer of this pathogen. Note the evidence presented suggested that a significant number of CD cases were the result of infection by MAP. A majority of the conferees (72%) noted that MAP present in dairy products and meat causes disease in some humans and thus poses a public health threat. This has still to be conclusively proven and Bach (2015) concluded that "it has not been elucidated yet whether MAP is the primary cause of the disease, or whether it exploits the mucosal inflammation already developed and just exacerbates the disease".įollowing a conference at Temple University in the US (Kuenstner et al , 2017) the conference participants reached consensus on several issues relating to MAP and concluded that the accumulating information now strongly supports the theory that MAP is a zoonotic bacterium can cause disease in humans. MAP is the causal agent of Johne’s disease, a chronic, currently incurable although there are now experimental treatments, inflammatory bowel disease of cattle and other ruminants.īecause the symptoms of these human and animal diseases are similar and that MAP has been isolated from gut-lesions combined with the detection of a unique MAP-DNA insertion sequence (IS900) in intestinal tissue from many patients and the elimination of the disease in some patients by prolonged antibiotic treatment, a link between Crohn’s disease and MAP has been suggested. paratuberculosis (MAP) in milk since it has been linked to Crohn’s Disease (CD) and a range of other inflammatory diseases. Emerging potential pathogens that are more heat resistant than current indicator pathogens 75☌ for 25 seconds (O'Reilly et al., 2004 Mullan, 2019) or higher for pasteurization for added safety. The 15 seconds at 72☌ requirement is the minimum heat treatment required and many companies in Britain and Ireland use 25 second holding times and higher temperatures e.g. Note some strains of Listeria monocytogenes can have a higher thermal resistance than C. ![]() International regulatory agencies require that HTST pasteurization of milk is designed to ensure at least a 5 log reduction of M. burnetii was selected as the heat treatment indicator organism for pasteurization before the significance of Listeria monocytogenes was known. ![]() An updated and reviewed version of this paper has been published (Mullan, 2019).Ĭurrently Coxiella burnetii is recognised as the most heat-resistant non-sporulating pathogen likely to be present in milk. The article does not discuss the effects of heat on the functional properties or the nutritive quality of milk. The log reductions refer to log10 or decimal (10 fold) reductions in the concentration of viable bacteria. paratuberculosis (MAP) was designated as a human pathogen. This article calculates the effect of HTST treatment on the number of log reductions of major milk pathogens and discusses the temperature milk should be pasteurized if Mycobacterium avium subsp. Regrettably raw milk and raw milk products remain a major source of new cases of bovine tuberculosis. Pasteurization has eliminated heat-treated-milk as a source of infection. ![]() Prior to the introduction of pasteurization, consumption of raw cow milk was a major source of infection by bacteria causing tuberculosis. The history of pasteurization (pasteurisation is also valid) is fascinating and is notable for its public health success and for the insights of many scientists and engineers. The use of high temperature short time heat treatment (HTST) of milk (72☌ for 15 seconds) to destroy pathogenic bacteria, reduce the number of spoilage organisms and increase shelf life is well established (Juffs and Deeth, 2007).
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