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Washington, D.C.: USDA 185 Yamamoto, S., H Itano, H Kataoka, and M Makita 1982 Gas–liquid chromatographic method for analysis of di- and polyamines in foods J Agric Food Chem 30:435–439 186 Zhao, T., M.P Doyle, P.J Fedorka-Cray, P Zhao, and S Ladely 2002 Occurrence of Salmonella enterica serotype Typhimurium DT 104A in retail ground beef J Food Protect 65:403–407 187 Zottola, E.A., and F.F Busta 1971 Microbiological quality of further-processed turkey products J Food Sci 36:1001– 1004 Chapter Processed Meats and Seafoods PROCESSED MEATS Processed meats are those meat products that are cured, smoked, or cooked The microbiota most often associated with these products is listed in Table 5–1 The behavior of processed meats stored under vacuum or modified atmospheres is discussed in Chapter 14 Curing Although curing was used in ancient times as a means of meat preservation, it is employed now more for flavor and color development The classic meat cure ingredients are NaCl, nitrite or nitrate, and sugar (sucrose or glucose), with NaCl being the major ingredient In addition to these, some products may contain curing adjuncts such as phosphates, sodium ascorbate or erythorbate, potassium sorbate, monosodium glutamate, hydrolyzed vegetable proteins, lactates, or spices In dry curing, no water is added to the NaCl, nitrite or nitrate, and sugar mixtures In pickle curing, these ingredients are added to water to form a brine Salt serves to prevent microbial growth during and after curing, and up to 2.5% may be found in finished products Nitrite or nitrate serves to stabilize red meat color, contribute to cured meat flavor, retard rancidity, and prevent the germination of clostridial spores The isomers sodium ascorbate and erythorbate are used to stabilize color, to speed curing, and to make the cure more uniform Since erythorbate is more stable than its isomer, its use is preferred, and it increases the yield of nitric oxide from nitrite and nitrous acid At a level of 550 ppm, ascorbate or erythorbate reduces nitrosamine formation Sugar is involved in at least three curing functions: color stabilization, flavoring, and substrate for lactic fermentation Also, it moderates the harsh flavor of NaCl Corn syrups, molasses, or honey may be substituted for flavor Phosphates are used in most pumped meats (bacon, ham, roast beef, pastrami, etc.) to increase water binding In curing brines, sodium tripolyphosphate is most commonly used, but a mixture of tripolyphosphate and sodium hexametaphosphate is used widely See Chapter 13 for information on polyphosphates as antimicrobial agents 101 102 Modern Food Microbiology Table 5–1 Genera of Bacteria and Fungi Most Frequently Found on Processed Meats Bacteria Genus Acinetobacter Aeromonas Alcaligenes Bacillus Brochothrix Carnobacterium Corynebacterium Enterobacter Enterococcus Hafnia Kocuria Kurthia Lactobacillus Lactococcus Leuconostoc Listeria Microbacterium Micrococcus Moraxella Paenibacillus Pediococcus Pseudomonas Serratia Staphylococcus Vibrio Weissella Yersinia Carnimonas Clostridium Macrococcus Shewanella Fungi Gram Reaction Relative Prevalence − − − + + + + − + + + + + + + + + + − + + − − + − + − − + + − X X X X X X X X X X X X XX X X X X X X X X XX X X X X X X XX X X Genus Relative Prevalence Yeasts Candida Debaryomyces Saccharomyces Trichosporon Yarrowia X XX X X X Molds Alternaria Aspergillus Botrytis Cladosporium Fusarium Geotrichum Monilia Mucor Penicillium Rhizopus Scopulariopsis Thamnidium X XX X X X X X X XX X X X Note: X = known to occur; XX = most frequently reported Sausages (L salsus, salted or preserved) constitute one of the major groups of cured meat products and they may be classified as follows: fresh (patties, links) uncooked smoked (mettwurst and Polish sausage) cooked smoked (bologna and wieners) cooked (liver sausage) dry (Genoa salami, pepperoni) semidry (Lebanon bologna, cervelat) Processed Meats and Seafoods 103 Semidry sausages have a final pH around 4.7–5.0, and refrigeration is required The final pH of dry sausages is about the same as that for semidry but these products are shelf stable because of their lower moisture content The relative safety of these products is discussed below The common cured bacon in the United States is either dry or pickle cured, with the latter being the more common Following cure, it may be smoked Canadian bacon is characterized by being quite lean, since it comes from the large muscle of pork loins Wiltshire bacon is prepared from the sides of selected hogs, followed by pumping of cure ingredients and subsequent storage in pickle brines Most hams in commerce are of the pickle-cure variety and they are cured following injection of the pickle cure by artery pumping, single-needle stitch, or multiple-needle stitch For dry-cured or country-cured hams, the dry curing salts are applied by rubbing followed by storage at refrigerator temperatures for 28 to 50 days, depending on size and thickness All curing ingredients may be expected to contain microorganisms, and care should be taken to ensure that undesirable ones are not introduced to products during ingredient application Smoking This process is applied to many cured meats, and the primary purposes of smoking meat are (1) development of aroma and flavor, (2) preservation, (3) creation of new products, (4) development of color, (5) formation of a protective skin on emulsion-type sausages, and (6) protection from oxidation.73 Smoke, whether directly from wood or in liquid form, contains phenols, alcohol, organic acids, carbonyls, hydrocarbons, and gases The antimicrobial properties of smoking result from the activities of some of the smoke ingredients and the heat that is associated with wood smoking Liquid smoke contains all of the essential ingredients of wood smoke, but it is free of the carcinogen benzopyrene SAUSAGE, BACON, BOLOGNA, AND RELATED PRODUCTS In addition to the meat components, sausages and frankfurters have additional sources of organisms in the seasoning and formulation ingredients that are usually added in their production Many spices and condiments have high microbial counts The lactic acid bacteria and yeasts in some composition products are usually contributed by milk solids In the case of pork sausage, natural casings have been shown to contain large numbers of bacteria In their study of salt-packaged casings, Riha and Solberg76 found counts to range from log10 4.48 to log10 7.77 cfu/g and from log10 5.26 to log10 7.36 cfu/g for wet-packaged casings Over 60% of the isolates from these natural casings consisted of Bacillus spp., followed by clostridia and pseudomonads Of the individual ingredients of fresh pork sausage, casings have been shown to contribute the largest number of bacteria.76,88 Processed meats such as bologna and salami may be expected to reflect the sum of their ingredient makeup with regard to microbial numbers and types The biota of frankfurters has been shown to consist largely of Gram-positive organisms with micrococci, bacilli, lactobacilli, microbacteria, enterococci, and leuconostocs along with yeast.24 In a study of slime from frankfurters, these investigators found that 275 of 353 isolates were bacteria, and 78 were yeast B thermosphacta was the most conspicuous single isolate With regard to the incidence of C botulinum spores in liver sausage, of 276 heated (75◦ C for 20 minutes) and of 276 unheated commercial preparations contained type A botulinal toxin.43 The most probable number (MPN) of botulinal spores in this product was estimated to be 0.15/kg Wiltshire bacon has been reported to have a total count generally in the range of log10 5–6/g,53 whereas high-salt vacuum-packaged bacon has been reported to have a generally lower count—about 104 Modern Food Microbiology log10 4/g The biota of vacuum-packaged sliced bacon consists largely of catalase-positive cocci, such as micrococci and coagulase-negative staphylococci, as well as catalase-negative bacteria of the lactic acid types, such as lactobacilli, leuconostocs, pediococci, and enterococci.3,13,59 The biota in cooked salami has been found to consist mostly of lactobacilli So-called soul foods may be expected to contain large numbers of organisms, as they consist of offal parts that are in direct contact with the intestinal-tract biota, as well as other parts, such as pig feet and pig ears, that not receive much care during slaughtering and processing This was confirmed in a study by Stewart86 who found a geometric mean aerobic plate count (APC) of log10 7.92/g for chitterlings (pig intestines), log10 7.51/g for maws, and log10 7.32/g for liver pudding For S aureus, log10 numbers of 5.18, 5.70, and 5.15/g, respectively, were found for chitterlings, maws, and liver pudding Jerky is a dried shelf-stable product made from lightly salted and spiced slices of meat or fish—most often beef When drying to reduce aw to or below 0.86 is carried out within hours, no problems are likely to result from pathogens, but when drying is not rapid and extends over a long period of time at temperatures