System for evaluating clostridial inhibition in cured meat products.

A method for evaluating inhibition of Clostridium botulinum, C. sporogenes, and C. perfringens in cured meat products was developed. This system can easily be used in the microbiology laboratory using aluminum ointment tubes as the product container. Swells caused by gas production by the organism are easily observed by using the aluminum tubes. Results obtained confirmed earlier work on the inhibitory effect of sodium nitrite and sorbic acid against the clostridia in cured meat products.     

Effect of processing variables on the outgrowth of Clostridium sporogenes PA 3679 spores in comminuted meat cured with sorbic acid and sodium nitrite.

The effects of the initial pH and a "short pump" on the outgrowth of Clostridium sporogenes PA 3679 spores in comminuted cured pork were studied. Fresh ground pork was cured with salt, sugar, phosphate, ascorbate, and varying amounts of sodium nitrite and sorbic acid. The product was comminuted and inoculated with 1,000 spores of C. sporogenes per g. The meat was stuffed into 1-ounce (ca. 28.4-g) aluminum tubes, cooked to 58.5 degrees C, cooled, and incubated at 27 degrees C to observe for swells. Product cured with 0.2% sorbic acid in combination with 40 ppm sodium nitrite (40 microgram/g) had better clostridium inhibition than did product cured with 120 ppm nitrite within a pH range of 5.0 to 6.7. The sorbic acid-40 ppm nitrite combination also gave better clostridial protection than did the 120 ppm nitrite alone when reduced amounts of curing ingredients were present.     

Effect of processing variables on the outgrowth of Clostridium sporogenes PA 3679 spores in comminuted meat cured with sorbic acid and sodium nitrite.

The effects of the initial pH and a "short pump" on the outgrowth of Clostridium sporogenes PA 3679 spores in comminuted cured pork were studied. Fresh ground pork was cured with salt, sugar, phosphate, ascorbate, and varying amounts of sodium nitrite and sorbic acid. The product was comminuted and inoculated with 1,000 spores of C. sporogenes per g. The meat was stuffed into 1-ounce (ca. 28.4-g) aluminum tubes, cooked to 58.5 degrees C, cooled, and incubated at 27 degrees C to observe for swells. Product cured with 0.2% sorbic acid in combination with 40 ppm sodium nitrite (40 microgram/g) had better clostridium inhibition than did product cured with 120 ppm nitrite within a pH range of 5.0 to 6.7. The sorbic acid-40 ppm nitrite combination also gave better clostridial protection than did the 120 ppm nitrite alone when reduced amounts of curing ingredients were present.     

RECOVERY and SPECIATION of LISTERIA FROM RAW and COOKED MEAT and POULTRY PRODUCTS

Recovery of Listeria from raw and cooked meat products was compared using Fraser broth (FB) enrichment incubated at 30 and 35C for 24 and 48 h. the Micro-ID Listeria test strip for biochemical characterization of Listeria was also compared with conventional tests. Listeria spp. were recovered from 33, 47, and 20 of the raw chicken, raw beef and cooked meat products, respectively. No false-negative reactions were observed and more total Listeria -positive samples were found using FB incubated for 48 h compared with 24 h. Samples incubated at 35C had fewer false negative tubes than those incubated at 30C. More false-positive FB tubes were observed after 48 h than after 24 h incubation. Over half of the cooked samples did not hydrolyze the esculin and turn the tubes black, and therefore did not have to be streaked onto selective plates. However, with raw chicken or beef because of the large number of false-positive FB tubes, almost all tubes had to be streaked onto selective plates and very little advantage was gained from using the FB. the Micro-ID Listeria test kit gave a 100% correlation with conventional biochemical reactions for pure cultures of Listeria isolated from the three categories of meat products in this study. When used in conjunction with hemolysis plates and CAMP reactions, this test identifies species of Listeria isolates within 24 h of visible colony formation.     

Probiotic meat products and human nutrition

Raw cured and ripened meat products have been traditionally manufactured using the fermentation of native or added carbohydrates by lactic acid bacteria found in meat or in its environment. The commercial application of probiotic microorganisms in dry fermented meat products is not yet common. Probiotic bacterial strains that can be used in the manufacturing of dry fermented meat products should be capable of surviving in conditions found in fermented products; furthermore, they should dominate other microorganisms found in the finished product. The initial number of microorganisms in sausage filling or on the surface of ham or loin cannot be reduced as in milk pasteurization, for example. Therefore, the choice of appropriate microorganisms is important. Probiotic meat products are a relatively new and not very well recognized field of meat industry, but the most important issue is to find a compromise between technological aspects, safety, quality and health-beneficial effects of food. Therefore, the object of this review is on the one hand to analyze technological possibilities and quality parameters of probiotic meat products, and on the other hand to discuss risks and benefits of probiotic meat used in human nutrition.     

Thermal destruction of Clostridium botulinum spores suspended in tomato juice in aluminum thermal death time tubes.

The heat destruction characteristics of Clostridium botulinum spores suspended in tomato juice and phosphate buffer were determined by the survivor curve method with aluminum thermal death time tubes. Two type A strains of C. botulinum and a type B strain were evaluated. Strains A16037 and B15580 were implicated in outbreaks of botulism involving home-canned tomato products. Strain A16037 had a higher heat resistance than either 62A or B15580. The mean thermal resistance (D-values) for A16037 in tomato juice (pH 4.2) were: 115.6 degrees C, 0.4 min; 110.0 degrees C, 1.6 min; and 104.4 degrees C, 6.0 min. The mean D-values for A16037 in Sorensen 0.067 M phosphate buffer (pH 7) were: 115.6 degrees C, 1.3 min; 110.0 degrees C, 4.4 min; and 104.4 degrees C, 17.6 min. At each test temperature, the D-values were approximately three times higher in buffer than in tomato juice. The z-value for C. botulinum A16037 spores in tomato juice was 9.4 degrees C, and in buffer the z-value was 9.9 degrees C. The use of aluminum thermal death time tubes in a miniature retort system makes it possible to determine survivor curves for C. botulinum spores at 121.1 degrees C. This is possible because the lag correction factor for the aluminum tubes is only about 0.2 min, making possible heating times as short as 0.5 min.     

Organization of the gene cluster for biosynthesis of penicillin in Penicillium nalgiovense and antibiotic production in cured dry sausages

Several fungal isolates obtained from two cured meat products from Spain were identified as Penicillium nalgiovense by their morphological features and by DNA fingerprinting. All P. nalgiovense isolates showed antibiotic activity in agar diffusion assays, and their penicillin production in liquid complex medium ranged from 6 to 38 microgram. ml-1. We constructed a restriction map of the penicillin gene cluster of P. nalgiovense and found that the organization of the penicillin biosynthetic genes (pcbAB, pcbC, and penDE) is the same as in Penicillium chrysogenum and Aspergillus nidulans. The pcbAB gene is located in an orientation opposite that of the pcbC and penDE genes in all three species. Significant amounts of penicillin were found in situ in the casing and the outer layer of salami meat during early stages of the curing process, coinciding with fungal colonization, but no penicillin was detected in the cured salami. The antibiotic produced in situ was sensitive to penicillinase.     

Microbial interaction in cooked cured meat products under vacuum or modified atmosphere at 4 degrees C

AIMS: To investigate the antagonistic activity of two lactic acid strains against the spoilage microflora in cooked cured meat products, vacuum or modified atmosphere packed at 4 degrees C and to determine the inhibitory capacity of their bacteriocins. METHODS AND RESULTS: Frankfurter-type sausages and sliced cooked cured pork shoulder were inoculated with Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442 or with their bacteriocins. The microbial, physico-chemical (pH, L- and D-lactate, acetate and ammonia) and colour changes were studied. Results under vacuum packaging showed that in the uninoculated samples of the pork product the spoilage microflora grew but in the inoculated ones the spoilage microorganisms (e.g. Brochothrix thermosphacta and enterococci) reduced during the storage. This observation was more pronounced in the samples with the addition of bacteriocins. In the frankfurter-type sausages the spoilage microflora did not grow in the uninoculated and inoculated samples. In the modified atmosphere enriched in CO2 the population of spoilage microflora remained at low levels in both products, indicating that CO2 has an effect on the spoilage microorganisms' growth. In the pork product the concentrations of acetate and d-lactate increased while L-lactate decreased, but in the frankfurter-type sausages increase of acetate and D-lactate was not observed. CONCLUSIONS: Lactic acid strains had an effect on the spoilage microflora growth but did not affect, negatively, the organoleptic properties of the products. These strains may be used as biopreservative cultures or their bacteriocins could be an important contribution to microbiological quality of meat products. SIGNIFICANCE AND IMPACT OF STUDY: Establishment of biopreservation as a method for extension of shelf life of meat products.     

Simultaneous detection of Carnobacterium and Leuconostoc in meat products by multiplex PCR

AIMS: To develop a multiplex PCR approach for simultaneous detection of Leuconostoc and Carnobacterium and its validation in meat products. METHODS AND RESULTS: Two multiplex PCR assays were developed using newly designed 16S rDNA-directed primers adapted to the current taxonomic situation of genera Leuconostoc and Carnobacterium that allow: (i) simultaneous detection of both genera, and members of the nonmotile species of genus Carnobacterium and (ii) identification in a single assay of the nonmotile species C. divergens, C. maltaromicum and C. gallinarum. Sensitivity values of 10(3) and 10(4) CFU g(-1) were determined for multiplex PCR detection of Carnobacterium and Leuconostoc, respectively, following artificially inoculated meat trials. In addition, both multiplex PCR assays were validated in 14 naturally contaminated samples covering nine types of meat products. Results obtained by colony identification were confirmed by PCR detection. CONCLUSIONS: The methods described in this study provide a rapid and reliable tool for PCR detection of Carnobacterium and Leuconostoc, in meat products, and for colony identification. SIGNIFICANCE AND IMPACT OF THE STUDY: This multiplex PCR approach will help in the analysis of the spoilage microbiota of refrigerated vacuum-packaged meat product in order to determine the appropriate preservation method.     

Application of a virulent bacteriophage cocktail leads to reduction of Salmonella enterica serovar Enteritidis counts in processed meat products

Salmonella enterica serotype Enteritidis (SE) is a major cause of food-borne disease outbreaks worldwide. We evaluated the effectiveness of five lytic bacteriophages applied as a cocktail to reduce the counts of SE in two types of processed meat products: cooked (turkey ham (TB) and chicken sausage (CS)) and cured sausage (Italian salami (IS) and barbecue sausage (BS)). Groups of 25 samples each were contaminated with SE, treated with a phage cocktail using a multiplicity of infection of 10⁵ and then incubated for ten days at 18°C and 4°C. A significant reduction in bacteria was obtained on days 3, 6 and 10 in all matrices incubated at 18°C (from 0.48 to 2.12?log Colony Forming Units (CFU)?g^?1) and at 4°C (from 0.23 to 2.06?log CFU?g^?1), with the exception of BS at day 3 at 4°C, and IS at both incubation temperatures throughout the trial. The viral titre remained stable in all matrices analysed except in BS. These results show the effectiveness of this bacteriophage cocktail against S. enterica serovar Enteritidis in some processed meat products such as CS, BS and TB.     

Antibotulinal efficacy of sulfur dioxide in meat.

The addition of sodium metabisulfite as a source of sulfur dioxide delayed botulinal outgrowth in perishable canned comminuted pork when it was temperature abused at 27 degree C. The degree of inhibition was directly related to the level of sulfur dioxide. Levels greater than 100 microgram of sulfur dioxide per g were necessary to achieve significant inhibition when a target level of 100 botulinal spores per g was used. Sodium nitrite partially reduced the efficacy of the sulfur dioxide. Sulfur dioxide offers a new option for the control of botulinal outgrowth in cured or noncured meat and poultry products.     

A medium for the detection of bacteria causing green discolouration of cooked cured meat products

Summary A cooked haemoglobin medium was developed for the detection of hydrogen-peroxide-producing bacteria. The composition and preparation of this medium are described. The medium has proved to be an adequate medium for diagnosis of the greening of cooked cured meat products caused by hydrogen-peroxide-producing lactic acid bacteria. Offprint requests to: F. K. Stekelenburg     

Heat Inactivation of In Vivo- and In Vitro-Grown Mycobacteria in Meat Products

Heat inactivation of mycobacteria from lesions and from culture was compared in meat products. In vivo-grown organisms were more easily heat inactivated than were in vitro-grown organisms.     

Effect of prior refrigeration on botulinal outgrowth in perishable canned cured meat when temperature abused.

Perishable canned cured meat inoculated with Clostridium botulinum spores was placed at 4.4 or 10 degrees C after manufacture. Spore germination occurred at 10 degrees C. The germinated cell count remained stable over a period of 16 to 18 weeks. During that time period the inhibitory system and residual nitrite descreased. These factors combine to make perishable canned cured meats more prone to spoilage and potential hazard if they are temperature abused after a period of refrigerated storage.     

Effect of prior refrigeration on botulinal outgrowth in perishable canned cured meat when temperature abused.

Perishable canned cured meat inoculated with Clostridium botulinum spores was placed at 4.4 or 10 degrees C after manufacture. Spore germination occurred at 10 degrees C. The germinated cell count remained stable over a period of 16 to 18 weeks. During that time period the inhibitory system and residual nitrite descreased. These factors combine to make perishable canned cured meats more prone to spoilage and potential hazard if they are temperature abused after a period of refrigerated storage.     

Response of the Extract-Release Volume and Water-Holding Capacity Phenomena to Microbiologically Spoiled Beef and Aged Beef

The aging of ground beef was effected by storing in gas-impermeable, sterile plastic bags with incubation at 7 and 15 C. Control meat from the same preparations was wrapped in aluminum foil and stored at the same temperature. In three experiments where control meat was tested, aged meat did not attain a log bacterial number of ca. 8.4 per gram until an average of 6 days after this level was reached in control meats. This degree of difference was shown in values for both extract-release volume (ERV) and water-holding capacity. The previously reported ERV value of around 25, which was found to correspond to an average log bacterial number of ca. 8.5 per gram for ground beef allowed to spoil in aluminum foil and freezer paper, was approximated for aged meats, which required an average of 9.7 days to attain this number compared with 4.1 days for unaged meats. Plate count methods indicated the predominant flora of aged beef to be gram-negative, facultatively psychrophilic rods.     

Effect of heat treatment on survival of, and growth from, spores of nonproteolytic Clostridium botulinum at refrigeration temperatures.

Spores of five type B, five type E, and two type F strains of nonproteolytic Clostridium botulinum were inoculated into tubes of an anaerobic meat medium plus lysozyme to give approximately 10(6) spores per tube. Sets of tubes were then subjected to a heat treatment, cooled, and incubated at 6, 8, 10, 12, and 25 degrees C for up to 60 days. Treatments equivalent to heating at 65 degrees C for 364 min, 70 degrees C for 8 min, and 75 degrees C for 27 min had little effect on growth and toxin formation. After a treatment equivalent to heating at 85 degrees C for 23 min, growth occurred at 6 and 8 degrees C within 28 to 40 days. After a treatment equivalent to heating at 80 degrees C for 19 min, growth occurred in some tubes at 6, 8, 10, or 12 degrees C within 28 to 53 days and at 25 degrees C in all tubes within 15 days. Following a treatment equivalent to heating at 95 degrees C for 15 mine, growth was detected in some tubes incubated at 25 degrees C for fewer than 60 days but not in tubes incubated at 6 to 12 degrees C. The results indicate that heat treatment of processed foods equivalent to maintenance at 85 degrees C for 19 min combined with storage below 12 degrees C and a shelf life of not more than 28 days would reduce the risk of growth from spores of nonproteolytic C. botulinum by a factor of 10(6).(ABSTRACT TRUNCATED AT 250 WORDS)     

Rapid and inexpensive recovery method of DNA fragments from agarose and polyacrylamide gels by a cotton-wool column tube.

We developed a rapid, convenient, simple, and inexpensive method for isolating pure DNA from agarose and polyacrylamide gels using cotton wool tubes. DNA fragments ranging in size from 193-23,130 bp can be easily recovered within 2 hours by centrifugation through cotton wool from gel slices. The recovery rate of this method is 35% to 50%, when estimated for isolation of lambda DNA-HindIII fragments. We have also recovered 700-bp polymerase chain reaction (PCR) products using cotton wool tubes from electrophoresis on both a 0.8% agarose gel and a 6% polyacrylamide gel, in which satisfactory yields of more than 50% were obtained. The DNA thus recovered in this way is biologically active and can be used as a substrate for further experimental procedures without additional purification steps.     

肉及肉制品中空肠弯曲菌的污染情况调查

我们对辽宁地区肉及肉制品进行弯曲杆菌属检查,发现12.9%(23/177)的样品为弯曲杆菌属阳性.经API Campy鉴定系统鉴定,其中26.1%(6/23)为空肠弯曲菌(C.jejuni)阳性,同时发现1株大肠弯曲菌.该调查证实,辽宁地区进出口的肉及肉制品中,存在空肠弯曲菌的污染,如果销售不当或再加工卫生不良,会对消费者的健康构成潜在威胁.     

Behaviour of Listeria monocytogenes in meat and its control by a bacteriocin-producing strain of Lactobacillus sake

Lactobacillus sake Lb 706 can release a bacteriocin inhibitory to Listeria monocytogenes . In MRS broth, viable counts decreased rapidly when Lact. sake Lb 706 was added, whereas growth of the listerias was not affected by a bacteriocin-negative variant of the same Lactobacillus strain. Inhibition of L. monocytogenes was also observed in pasteurized minced meat inoculated with Lact. sake Lb 706. The bacteriocin produced is apparently effective in meat. However, the effect of the bacteriocin producer was less evident in minced meat than in broth. In comminuted cured raw pork filled into casings (German-type 'fresh Mettwurst'), L. monocytogenes was able to grow at a pH of 6.3, but addition of Lact. sake Lb 706 prevented the growth of listerias during the first few days after manufacture. At normal pH (5.7) L. monocytogenes did not multiply and addition of Lact. sake Lb 706 reduced viable counts of listerias by about one log cycle. Lactobacillus sake Lb 706 therefore may have some potential as a protective culture in meat products.