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Inactivation of E. coli in UCFM3.1 History3. Uncooked Fermented Meat ProcessesFermented meats, including salami, have been manufactured for centuries (Lücke, 1985;Leistner, 1995; Ricke and Keeton, 1997). European sausages have been produced since theMiddle Ages and per capita production and consumption of UCFM is still greatest in Europe.European migrants to USA and Australia brought their UCFM methods and styles with them,which have since altered and ‘evolved’ in those new cultures. Chinese-style sausage, withpork as the main ingredient, is also common in Asia and dates back thousands of years(Leistner, 1995; Yu and Chou, 1997). The Thai fermented sausage Nham is also receivingattention in the scientific literature. Increasing Asian immigration to Australia may see theintroduction of Asian UCFM products also, but these are not considered specifically in thisreport. Some details of manufacturing processes for Asian UCFM, and an assessment oftheir safety relative to European UCFM processes, are given in Appendix 4.European UCFM are generally considered to fall into two categories – semi-dry and dry. InUSA these products are broadly termed as cervelat and salami, respectively. Salamisoriginated in the Mediterranean region, and are characterised by heavy seasoning and by notbeing smoked. These styles generally have Italian or Spanish names. As UCFM methodsspread north to cooler parts of Europe, the semi-dry sausages emerged. Typically, thesewere prepared during the cooler winter months and stored until summer. Hence, theybecame known as ‘summer sausage’. They were less spiced, smoked at cool temperatures,and because of the cooler climate were less susceptible to spoilage. These styles typicallynow have Germanic names. An overview of UCFM styles and their characteristics is shownin Appendix 1.Appendix 2, however, illustrates the range of product names and final product parameters forsausages available in USA, the Toronto region of Canada, and Australia and shows thatproducts with apparently similar names can have quite different pH and water activities. InAustralia there are also many varieties of fermented sausages available. Table 3 comparesthe characteristics of Australian UCFM products marketed as ‘salami’ or ‘mettwurst’, andreveals that there is little difference despite that the ‘typical’ characteristics of these productsare very different (see Appendix 1). The evolution of the industry and the products ofindividual processors has meant that product names are no longer reliable descriptions ofprocessing methods or product characteristics.3.2 Making UCFMUCFM products have long shelf lives due to the combination of acidification (throughfermentation or addition of the acidulant glucono-∂-lactone), removal of oxygen, addition ofcompounds that favour the growth of some microbes while retarding the growth of others,and ultimately the removal of water. Variables in the production of fermented meats include:• type of meat;• amount of fat added;• starter culture used (if used);• curing mix composition & concentration – nitrite/nitrate levels, salt, spices, etc• fermentation time and temperature;• maturation time and temperature;• sausage diameter;• final pH, final water activity, and• recommended storage temperaturesThe relevance of each of these variables to the microbiological safety of the products isdiscussed below. Unless otherwise noted the information in those sections is drawn fromLücke (1985), Leistner (1995), Lücke (1995) and Ricke and Keeton (1997).Page 10 of 59
Inactivation of E. coli in UCFM3.2.1 IngredientsMeat and FatFrom a product quality perspective, the type of meat used in UCFM is important. It is lessimportant for the microbiological safety of the product, unless some types of meat are morehighly contaminated with pathogens than others. Beef and pork are the species usedpredominantly in UCFM production. Both are known to be contaminated occasionally withpathogenic E. coli, as is sheep meat which appears to have slightly higher levels ofcontamination (Chivell, 1995; MRC, 1996, MLA, 1998) 5 . Details of levels and incidence ofpork contamination by E. coli (generic or EHEC) in Australia were not found in the publishedliterature. Heuvelink et al. (1999a) isolated EHECs from two of 145 Dutch pigs and Heuvelinket al. (1999b) isolated EHECs in two of 402 samples of minced beef and pork and 1 in 393samples of other raw pork products at retail in the Netherlands. Korsak et al. (1998) isolatedEHECs from 14% of pork carcasses in Belgium slaughterhouses, and Borie et al. (1997) alsoreported high rates of contamination (>50%) of pork carcases at slaughter in Chile.The percentage of meat to fat, and type of fat, is also an important quality consideration, andamong the defining characteristics of the finished product. Again, it is not importantmicrobiologically except in the sense that the proportion of fat affects the amount of freewater in the product. Of the lean muscle in the mix, about 70 –75% by weight is water. UCFMrecipes are typically described in terms of weight of additives per weight of the batch. It is theconcentration of the additives in the aqueous (water) phase of the food that is important tounderstanding the microbiology of the product. The effective concentration of those additivesdepends on the proportion of fat in the batch. More fat in the mixture means that there is lesslean meat, which in turn means less water.As a guide, for a product containing 30% (by weight) fat, water makes up only about 53% ofthe weight of the batch. Thus, the effective concentration of any water soluble additives isabout twice that predicted simply on the basis of its weight compared to the overall weight ofthe batch. During maturing of UCFM weight losses of 20 – 30% occur in ‘semi-dry’ UCFMand even more for ‘dry’ style products. This is due to loss of water only, and further increasesthe effective concentration of the water soluble components, so that the final concentration isup to 4 times the apparent level added to the mixture expressed on a weight for weight basis.The meat is ground together with some or all of the following ingredients. That mixture isknown as the ‘batter’.Salt (NaCl)Typically 2.5 – 3.0% NaCl (w/w) is added to UCFMs. The water activity (a w ) of the productdecreases during processing as the product loses water. Drying can be a rapid process,particularly if the pH is below 5.3 since protein solubility is low and a gel forms around meatand fat particles (Lücke, 1985). This facilitates the removal of water and lowering of a w ,preventing growth of pathogens. As explained above, this leads to effective concentrations inthe typical finished semi-dry product of ~ 7.5 – 12 % salt, corresponding to water activities inthe range 0.95 - 0.92. Lower water activities (~0.85) are achieved in Southern Europeanstyle dry sausages (see Table 1) (Calicioglu et al., 1997; Ricke and Keeton, 1997).SugarsSugars (0.4 – 0.8%) are added to the mixture as a carbon source for the fermentativebacteria. These bacteria, usually ‘lactic acid bacteria’, metabolise the sugars producing lacticacid in the process, which is released into the UCFM. The biochemistry of conversion ofsimple sugars (e.g glucose) results in almost twice as much lactic acid being produced as theconcentration of simple sugars added. For more complex sugars, a smaller ratio of lactic acid5In recent years there has been an epidemic of Nipah virus among pig herds in South East Asian nations. The resultingshortage in pork in those nations has opened a valuable export market for Australian pork producers. There is anecdotalevidence that this has resulted in less pork being available in Australia, and that lower proportions of pork are being usedin some Australian UCFM, being replaced with by beef and/or muttton/lamb.Page 11 of 59
Page 1 and 2: Final reportFOOD SAFETYPrepared by:
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