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The prevalence of Clostridium botulinum types A, B, E and F in river lampreys caught in Finnish rivers was determined for the first time using a quantitative PCR-MPN (most probable number) analysis. One of 67 raw whole lampreys (1.5%) was positive for the botulinum neurotoxin type E gene, with the estimated C. botulinum count being 100spores/kg. Two type E strains were isolated from the positive sample and confirmed as different genotypes by pulsed-field gel electrophoresis. Although the current procedure of bringing the charcoal-broiled lampreys to market has been without any further packaging or extended storage, interest towards increasing the shelf life of the product by vacuum-packaging is increasing. Our results demonstrate that C. botulinum type E may constitute a safety hazard in processed lampreys from the Baltic Sea area if packaging and extended shelf lives are to be used. To control the potential risk, a storage temperature of 3 degrees C or below should be recommended for these products.

The microbiological quality of 30 production lots of charcoal-broiled river lampreys was studied at three lamprey processing plants (plants A, B, and C). Samples were taken directly after charcoal broiling and stored at 22 and 3 degrees C. Lampreys were examined on the day of manufacture, and those kept at 22 degrees C were examined every second day for 6 days. Samples kept at 3 degrees C were examined every fourth day for up to 24 days. On the production day, the mean aerobic plate counts (APCs) for broiled lampreys from plants A, B, and C were 2.29 log CFU/g, 1.88 log CFU/g, and undetectable (1.67 log CFU/g), respectively. At 22 degrees C, the mean APCs for samples from plants A, B, and C increased markedly within 4 days, and after 6 days the counts for samples from these plants were 8.56, 5.04, and 6.23 log CFU/g, respectively. Chilling and storage at 3 degrees C remarkably improved the shelf life of the product. The levels of bacteria in charcoal-broiled river lampreys from plant A were higher than those in lampreys from plants B and C. No significant increases in APCs were observed during storage at 3 degrees C for 24 days; mean APCs did not exceed 2.80 log CFU/g for samples from any plant. Staphylococcus aureus was found in two samples. No lactic acid bacteria, thermotolerant coliforms, enterococci, Clostridium perfringens, or Listeria monocytogenes was detected. Microbiological data from this study will be used for the development of a hazard analysis for the determination of critical control points.

Contamination analysis of persistent and nonpersistent Listeria monocytogenes strains in three meat processing plants and one poultry processing plant were performed in order to identify factors predisposing to or sustaining persistent plant contamination. A total of 596 L. monocytogenes isolates were divided into 47 pulsed-field gel electrophoresis (PFGE) types by combining the restriction enzyme patterns of AscI (42 patterns) and ApaI (38 patterns). Persistent and nonpersistent strains were found in all plants. Nonpersistent PFGE types were found mostly at one sampling site, with the processing environment being the most common location, whereas the persistent strains were found at several sampling sites in most cases. The processing machines were frequently contaminated with persistent L. monocytogenes PFGE types, and it was of concern that surfaces having direct contact with the products were contaminated. The role of the processing machines in sustaining contamination and in contaminating the products appeared to be important because the final product of several processing lines was contaminated with the same L. monocytogenes PFGE type as that found in the processing machine. The proportion of persistent PFGE types in heat-treated products was eight times higher than in the raw products, showing the importance of the persistent PFGE types as contaminants of the final heat-treated products. The contamination status of the processing lines and machines appeared to be influenced by the compartmentalization of the processing line, with poor compartmentalization increasing L. monocytogenes contamination. The separation of raw and post-heat treatment areas seemed especially important in the contamination status of post-heat treatment lines.

Nine restriction enzyme combinations and 108 different primer combinations were initially tested for suitability for amplified fragment length polymorphism (AFLP) analysis of Listeria monocytogenes; the combination of HindIII and HpyCH4IV showed consistently strong signals on gels, amplified an adequate number of DNA fragments and detected polymorphism among closely related strains based on AscI macrorestriction profiles. AFLP also distinguished between L. monocytogenes, L. innocua, L. ivanovii, L. seeligeri, L. welshimeri and L. grayi species. All Listeria species showed species-specific clusters, with less than 33% similarity between different species. A total of 34 L. monocytogenes strains were characterised by using both AFLP and pulsed-field gel electrophoresis (PFGE). The results of AFLP analysis of L. monocytogenes strains were in concordance with those obtained by PFGE. Both methods identified 29 different genotypes of L. monocytogenes and had a high discrimination index (> 0.999). By combining the results of AFLP and PFGE, subtype discrimination was further improved. Numerical analysis of both AFLP and PFGE profiles yielded three genomic groups of L. monocytogenes strains. AFLP was found to be faster and less labour-intensive than PFGE. We conclude that the AFLP protocol is a highly discriminatory, reproducible and valuable tool in characterisation of Listeria strains and may also be suitable for Listeria species identification.

The possibility of the transfer of persistent Listeria monocytogenes contamination from one plant to another with a dicing machine was evaluated, and possible reasons for persistent contamination were analyzed. A dicing machine that diced cooked meat products was transferred from plant A to plant B and then to plant C. After the transfer of the dicing machine, L. monocytogenes PFGE type I, originally found in plant A, was soon also found in plants B and C. This L. monocytogenes PFGE type I caused persistent contamination of the dicing lines in plants B and C. The persistent L. monocytogenes strain and three nonpersistent L. monocytogenes strains found in the dicing line of plant C were tested for adherence to stainless steel surfaces and minimal inhibitory concentrations of a quaternary ammonium compound and sodium hypochlorite, disinfectants widely used in the dicing lines. The persistent strain showed significantly higher adherence to stainless steel surfaces than did the nonpersistent strains. The minimal inhibitory concentrations of sodium hypochlorite were similar for all strains, and the minimal inhibitory concentrations of the quaternary ammonium compound for three of the L. monocytogenes PFGE types, including the persistent PFGE type, were high. All persistent L. monocytogenes PFGE type I isolates were found in an area with high hygienic standards, with the dicing machine being the first point of contamination. These observations show that the dicing machine sustained the contamination and suggest that the dicing machine transferred the persistent L. monocytogenes PFGE type from one plant to another.

A taxonomic study was conducted to clarify the relationships of two bacterial populations belonging to the genus Weissella. A total of 39 strains originating mainly from Malaysian foods (22 strains) and clinical samples from humans (9 strains) and animals (6 strains) were analysed using a polyphasic taxonomic approach. The methods included classical phenotyping, whole-cell protein electrophoresis, 16S and 23S rDNA RFLP (ribotyping), determination of 16S rDNA sequence homologies and DNA-DNA reassociation levels. Based on the results, the strains were considered to represent two different species, Weissella confusa and a novel Weissella species, for which the name Weissella cibaria sp. nov. is proposed. Weisella confusa possessed the highest 16S rDNA sequence similarity to Weisella cibaria, but the DNA-DNA reassociation experiment showed hybridization levels below 49% between the strains studied. The numerical analyses of Weisella confusa and Weisella cibaria strains did not reveal any specific clustering with respect to the origin of the strains. Based on whole-cell protein electrophoresis, and ClaI and HindIII ribotyping patterns, food and clinical isolates were randomly located in the two species-specific clusters obtained.

Hand and nasal samples of flight-catering staff were collected from 1995 to 1997 to find employees carrying Staphylococcus aureus. Altogether 153 hand samples and 136 nose samples were taken. Nasal sampling showed a higher prevalence of S. aureus among food handlers (29%) than hand sampling (9%). A high proportion of the strains (46%) were enterotoxigenic, and a considerable amount of food handlers carried enterotoxigenic S. aureus, 6% and 12% according to hand and nasal sampling, respectively. Pulsed-field gel electrophoresis macrorestriction profiles revealed a total of 32 different types associated with the 35 employees carrying S. aureus. In most cases, the same type colonized both the hand and nose of a person. Despite the wide variety of types found, one strain colonized five persons and the second most common strain was associated with four food handlers. The predominant toxin produced was B, which was produced by the most common strain. The results showed that nasal sampling is a good way to detect S. aureus carriers, whereas hand sampling may fail to reveal carriers. The high proportion of enterotoxigenic strains show that a food handler harboring S. aureus must be considered a potential source of enterotoxigenic strains for airline meals.

Lactic acid bacteria (LAB) associated with gaseous spoilage of modified-atmosphere-packaged, raw, tomato-marinated broiler meat strips were identified on the basis of a restriction fragment length polymorphism (RFLP) (ribotyping) database containing DNAs coding for 16S and 23S rRNAs (rDNAs). A mixed LAB population dominated by a Leuconostoc species resembling Leuconostoc gelidum caused the spoilage of the product. Lactobacillus sakei, Lactobacillus curvatus, and a gram-positive rod phenotypically similar to heterofermentative Lactobacillus species were the other main organisms detected. An increase in pH together with the extreme bulging of packages suggested a rare LAB spoilage type called "protein swell." This spoilage is characterized by excessive production of gas due to amino acid decarboxylation, and the rise in pH is attributed to the subsequent deamination of amino acids. Protein swell has not previously been associated with any kind of meat product. A polyphasic approach, including classical phenotyping, whole-cell protein electrophoresis, 16 and 23S rDNA RFLP, 16S rDNA sequence analysis, and DNA-DNA reassociation analysis, was used for the identification of the dominant Leuconostoc species. In addition to the RFLP analysis, phenotyping, whole-cell protein analysis, and 16S rDNA sequence homology indicated that L. gelidum was most similar to the spoilage-associated species. The two spoilage strains studied possessed 98.8 and 99.0% 16S rDNA sequence homology with the L. gelidum type strain. DNA-DNA reassociation, however, clearly distinguished the two species. The same strains showed only 22 and 34% hybridization with the L. gelidum type strain. These results warrant a separate species status, and we propose the name Leuconostoc gasicomitatum sp. nov. for this spoilage-associated Leuconostoc species.

Adherence of 3 persistent and 14 nonpersistent Listeria monocytogenes strains to stainless steel surfaces after short and long contact times was investigated. L. monocytogenes strains were obtained from poultry plants and an ice cream plant throughout several years. Adherence tests were performed in tryptic soy broth at 25 degrees C for 1, 2, and 72 h. Test surfaces were rinsed after the contact time, and attached cells were stained with acridine orange and enumerated with an epifluorescence microscope. The persistent poultry plant strains showed adherence 2- to 11-fold higher than the nonpersistent strains following 1- and 2-h contact times. The adherence of the persistent ice cream plant strain after 1- and 2-h contact times was higher than most of the nonpersistent strains. Seven of 12 nonpersistent ice cream strains showed an adherence of less than half that of the persistent strain. After 72 h, the differences in adherence were not as marked, since half the nonpersistent strains had reached adherence levels comparable with the persistent strains. In fact, three nonpersistent strains showed even higher adherence than the persistent strains. Thus, results of this study reveal that persistent L. monocytogenes strains show enhanced adherence at short contact times, promoting their survival in food processing facilities and possibly having an effect on initiation of persistent plant contamination.

Febrile gastroenteritis in five healthy persons was associated with the consumption of vacuum-packed cold-smoked rainbow trout containing Listeria monocytogenes. L. monocytogenes isolates from the incriminated fish product lot and the stool samples were all of serotype 1/2a and were indistinguishable by pulsed-field gel electrophoresis employing AscI and SmaI.

Three commercially available test systems for the identification of anaerobic bacteria were evaluated for the identification of 18 proteolytic group I and 69 non-proteolytic group II Clostridium botulinum, four Clostridium sporogenes and 18 non-toxigenic group II C. botulinum-like strains. All proteolytic C. botulinum strains were misidentified by the Rapid ID 32 A and RapID ANA II, while 14 strains and all C. sporogenes strains were identified as C. botulinum or C. sporogenes by the API 20 A. Reversely, all non-proteolytic C. botulinum strains were misidentified by the API 20 A while the Rapid ID 32 A recognized 67 and RapID ANA II 68 strains. All C. sporogenes strains were recognized by the RapID ANA II, while the Rapid ID 32 A recognized one strain. All non-proteolytic non-toxigenic strains were identified as C. botulinum group II by the Rapid ID 32 A, 17 strains by the RapID ANA II, and one strain by the API 20 A. The results show that these test systems do not provide a reliable method for identification of C. botulinum.

One dominating strain of serotype 1/2b was found when serotyping and pulsed-field gel electrophoresis (PFGE) patterns were used for the characterization of 41 Listeria monocytogenes isolates originating from an ice cream plant. Samples were taken from the production environment, equipment and ice cream during the years 1990-1997. Serotyping divided the isolates into two serovars, 1/2b and 4b. Three rare-cutting enzymes (ApaI, AscI and SmaI) were used in the creation of PFGE patterns. AscI resulted in the best restriction enzyme digestion patterns (REDPs) for visual comparison. Eight different AscI REDPs were obtained, whereas ApaI produced six and SmaI seven banding patterns. When one-band differences are taken into account, 12 different PFGE types were distinguished based on information obtained with all three enzymes. The dominant PFGE type was found to have persisted in the ice cream plant for seven years. Improved and precisely targeted cleaning and disinfection practices combined with structural changes making for easier cleaning of the packaging machine, resulted in eradication of L. monocytogenes from this plant.

The microbiological contamination of reindeer carcasses was studied in 10 Finnish reindeer slaughterhouses. Six of the slaughterhouses were field slaughterhouses and four were plant slaughterhouses. In each slaughterhouse 11 to 30 carcasses were sampled, with abdomen, brisket, and foreleg as sampling sites. Sampling was performed immediately after slaughter, using a nondestructive swabbing method. The overall mean bacterial count of carcasses was 3.12+/-0.61 log CFU/cm2. The mean bacterial value of the carcasses and the bacterial counts of abdomen and brisket were significantly lower in field slaughterhouses than in plant slaughterhouses, suggesting that the controlled conditions of plant slaughterhouses do not necessarily improve the microbiological quality of reindeer carcasses. However, the highest bacterial contamination was found in a field slaughterhouse where the slaughter was performed after rain when the ground was without snow. Carcass contamination seemed to be increased by the use of an evisceration apron, the unnecessary washing of forelegs, and the unnecessary handling of carcasses with hands and arms.

Leuconostoc carnosum was shown to be the specific spoilage organism in vacuum-packaged, sliced, cooked ham showing spoilage during 3 weeks of shelf life. Identification of the specific spoilage organism was done by use of phenotypic data and ClaI, EcoRI, and HindIII reference strain ribopatterns. One hundred L. carnosum isolates associated with the production and spoilage of the ham were further characterized by pulsed-field gel electrophoresis (PFGE), together with some meat-associated Leuconostoc species: L. citreum, L. gelidum, L. mesenteroides subsp. dextranicum, and L. mesenteroides subsp. mesenteroides. ApaI and SmaI digests divided the industrial L. carnosum strains into 25 different PFGE types, ApaI and SmaI types being consistent. Only one specific PFGE type was associated with the spoiled packages. This type also was detected in air and raw-meat mass samples. The spoilage strain did not produce bacteriocins. Only seven isolates belonging to three different PFGE types produced bacteriocins. Similarity analysis of the industrial L. carnosum strains revealed a homogeneous cluster which could be divided into eight subclusters consisting of strains having at most three-fragment differences. The L. carnosum cluster was clearly distinguished from the other meat-associated leuconostoc clusters, with the exception of the L. carnosum type strain. Ribotyping can be very helpful in the identification of L. carnosum, but its discriminatory power is too weak for strain characterization. PFGE provides good discrimination for studies dealing with the properties of homogeneous L. carnosum strains.

Lactic acid bacteria are considered a major component of the microbial population found on various types of vacuum-packaged cooked sausages. Lactobacillus sake and Lactobacillus curvatus have been shown to be common species in these products. L. sake seems to form the predominant part of the spoilage population. Lactic acid bacterial growth on the surface of the sausages produces undesirable sensory attributes, such as sour aroma and taste. A specific spoilage phenomenon of commercial significance, characterized by long, stretchy, polysaccharide ropes between sausages or sausage slices, has also been found. L. sake strains play a major role in this spoilage phenomenon as well. Cooking of sausages during manufacturing destroys lactic acid bacteria on the surface of the sausages. Sausages are recontaminated with spoilage lactic acid bacteria mainly during the processing stages after cooking. During the chilling process, product contamination apparently results from exposure to airborne microorganisms. Workers and equipment are among the most likely sources of contamination during packaging and slicing. Spoilage strains originating from raw material may spread to other areas in the production facility (i.e., chill, slicing, and packaging rooms) via the air, workers and equipment. Decontamination methods can be used to prevent the growth of spoilage microorganisms and to extend the shelf life of vacuum-packaged sausages after packaging.

Spoilage characterized by bulging as a result of gas formation in bottled ketchup was studied, Samples produced microbial growth on MRS and Rogosa selective Lactobacillus agar. Seventy randomly selected isolates typed by using restriction endonuclease ( Cla I, Eco RI, Hind III) analysis were found to have identical DNA fragment patterns in gel electrophoresis. The strain was identified as Lactobacillus fructivorans using morphological, physiological and biochemical characteristics, combined with the information obtained from ribotyping. Factors affecting growth and survival of this L. fructivorans strain in ketchup production were also studied. An L. fructivorans count of 10 5 CFU/g resulted in spoilage of inoculated ketchup samples. Spoilage occurred only in samples incubated at 15 to 30°C. The L. fructivorans implicated in causing spoilage demonstrated heat resistance with a D value of 1.2 min at 65°C. The strain did not show resistance to alkaline active chloride-containing detergent sanitizer; alkyldimethylbenzylammonium chloride and alkyldimethylethylbenzylammonium chloride-containing sanitizer were also found to be effective antimicrobial agents.

Molecular typing was applied to an in-plant lactic acid bacterium (LAB) contamination analysis of a vacuum-packaged sliced cooked whole-meat product. A total of 982 LAB isolates from the raw mass, product, and the environment at different production stages were screened by restriction endonuclease (EcoRI and HindIII) analysis. rRNA gene restriction patterns were further determined for different strains obtained from each source. These patterns were used for recognizing the spoilage-causing LAB strains from the product on the sell-by day and tracing the sources and sites of spoilage LAB contamination during the manufacture. LAB typing resulted in 71 different ribotypes, of which 27 were associated with contamination routes. Raw material was distinguished as the source of the major spoilage strains. Contamination of the product surfaces after cooking was shown to be airborne. The removal of the product from the cooking forms was localized as a major site of airborne LAB contamination. Food handlers and some surfaces in contact with the product during the manufacture were also contaminated with the spoilage strains. Some LAB strains were also able to resist cooking in the core of the product bar. These strains may have an effect on the product shelf life by contaminating the slicing machine. The air in the slicing department and adjacent cold room contained very few LAB. Surface-mediated contamination was detected during the slicing and packaging stages. Food handlers also carried strains later found in the packaged product. Molecular typing provided useful information revealing the LAB contamination sources and sites of this product. The production line will be reorganized in accordance with these results to reduce spoilage LAB contamination.

Efficacy of Hygicult-tpc contact agar to control hygiene of slaughter equipment before work was studied in 3 slaughterhouses. Brushes from pork lines had higher bacterial counts (77 +/- 114 cfu on Hygicult slide) than other pieces of equipment in pork (55 +/- 101) and beef (42 +/- 110) lines. Low hygienic levels were found also in aprons, knives and conveyor belts. In general, equipment hygiene varied among the slaughterhouses studied (17 +/- 70, 45 +/- 128, 111 +/- 140) and in the comparisons of certain special equipment. Hygienic levels of the equipment were classified into 3 subclasses according to Hygicult counts. Sterilizers and saws had the lowest counts; aprons, and polishing and prescalding brushes had moderate counts. Highest counts were detected in rubber backscraping brushes and steel brushes used to clean pork carcasses and in conveyor belts. Such equipment is difficult to clean, and the bacterial count of 120 on a Hygicult slide is therefore recommended as the acceptable level after cleaning. The level of 50 on a Hygicult slide is recommended as the acceptable level for equipment, which is easy to clean. The limits recommended are based on the distribution of the Hygicult counts obtained. Hygicult-tpc is suitable for slaughterhouse hygiene control with an incubation for 72 h at 25 degrees C. The flexible handle enables sampling of surfaces that are hard to access with unflexible slides and agars.

Microbiological contamination of air and carcasses was studied in four slaughterhouses by using impactor samples taken at the back-splitting and weighing areas and by sampling carcasses with the swabbing method. Air flow was determined by an air-flow detector, and the movement of workers was observed. The air contamination level in the back-splitting areas (2.25 log CFU/100 liters of air) was generally higher than that in the weighing areas (2.03 log CFU/100 liters of air). Associations between the microbiological contamination of air and carcasses with the movements of workers were found. Layout of the slaughtering line was shown to be important in decreasing airborne contamination. Separation of the clean and unclean parts of the line as well as separation of the weighing area from the other clean parts of the line decreased the contamination level. It appears that airborne bacteria have an important role in carcass contamination.

Contamination of sliced cooked meat products with a Lactobacillus sake starter strain was suspected to cause spoilage in the products before the end of the expected shelf life. The cooked products were sliced and vacuum packaged in the room in which a fermented product was handled. Since L. sake strains are known to be a dominant part of spoilage microflora associated with vacuum-packaged meat products, a contamination study was performed. One hundred and eighteen strains were isolated from six spoiled vacuum-packaged meat products and from the surfaces of the packaging room and adjacent refrigerators. DNA was isolated from these strains and cleaved using Eco RI and Hin dIII restriction endonucleases to obtain characteristic ribotypes. Corresponding ribotypes of the L. sake starter strain were compared by using Eco RI digestions to the 14 different patterns obtained from the strains growing in spoiled products and on surfaces. The L. sake starter strain was shown to contaminate the packaging room and it was also isolated from one of the products. However, it was not a dominant strain in this product and it could not be linked to the other products. Our results indicated that handling the fermented product in the refrigerating and packaging rooms together with cooked products was not the major cause of spoilage in these products.

At three Finnish meat processing plants the processing rooms, meat trimmings and carcasses were examined for the presence of ropy slime-producing lactic acid bacteria. Bacterial isolates similar to ropy slime-producing lactobacilli strains able to produce ropy slime on meat products, were recovered from the processing rooms and meat trimmings, indicating that these rooms and raw materials are a source of contamination for ropy bacteria. The ability to produce ropy slime would appear to be a common characteristic of lactobacilli, since altogether 10 different ropy lactobacilli groups were isolated in this study.

The ability of the ropy slime-producing lactic acid bacteria to form ropy colonies aerobically and anaerobically on APT, MRS, MRS-S and Rogosa SL agars at 15, 20 and 30 degrees C was tested. Wide variation was observed in the proportion of ropy colonies produced with different culture methods and different test periods. The percentage of viscous colonies was usually highest at 15 degrees C. No suitable uniform method for all strains was found; and the results varied according to the bacterial strain studied. For testing purposes, use of the method producing the highest proportion of ropy colonies for each bacterial strain is recommended.

The study reported here deals with the survival of ropy slime-producing lactic acid bacteria in two different heat processes used in the Finnish meat industry. In both processes tested, ropiness was prevented in products inoculated with the bacteria before cooking. The bacterial count in the sausages decreased during processing over 4-5 log units/g. The bacteria were evidently unable to survive the processes, and the contamination of the products apparently takes place after cooking. Heat treatment given to vacuum-packed grill sausages after packing could delay the formation of ropy slime., (Copyright © 1992. Published by Elsevier Ltd.)

The effectiveness of certain commercial germicides against ropy slime-producing lactic acid bacteria was studied using the 5-5-5-suspension test and a tray test which simulated surface disinfection conditions in actual use. The rate of the destruction of the bacteria was lower in the tray test, and the bacteria seemed to be more resistant to the germicides on a steel surface than in vitro. The sanitizer products proved to be more effective than the detergent-sanitizer products. Quaternary ammonium products and an acid sanitizer with hydrogen peroxide were more effective than products containing chlorine compounds and polyhexamethylene biguanide chloride. The effectiveness of hypochlorite products appeared to be dependent on the concentration of available chlorine. The resistance of the ropy slime-producing bacteria may prove problematic if ineffective germicides are used. The use of detergent sanitizers and low-concentration hypochlorite products is not recommended.

The microbial numbers and the lactic acid bacteria population of the raw materials of cooked ring sausages were studied in order to determine the presence of the spoilage lactic acid bacteria of the sausages. The highest aerobic plate counts and lactic acid bacteria counts (up to the level of 10 8 and 10 5 CFU/g, respectively) were found in the pork skin emulsion and the meat trimmings. Lactic acid bacteria were also commonly found in the skim milk powder and the potato flour. Lactic acid bacteria isolates able to multiply at 8°C were recovered from all the raw materials studied except for the commercial spice mixture. These isolates could be divided into 11 different groups according to their morphological and biochemical characteristics. Isolates resembling the lactic acid bacteria strains responsible for the spoilage of vacuum-packed cooked ring sausages were found in the pork skin emulsion, the meat trimmings, and the potato flour. These raw materials can thus form a source for the spoilage bacteria of the sausages at a sausage processing plant.

The minimum, optimum, and maximum growth temperatures of ropy slime-producing lactic acid bacteria able to spoil vacuum-packed cooked meat products were determined on MRS-agar with temperature-gradient incubator Gradiplate R W10. The minimum growth temperatures of slime-producing lactobacilli and Leuconostoc mesenteroides strain D1 were below -1°C and 4°C, respectively. The low minimum growth temperature allows these bacteria to compete with other bacteria in meat processing plants and in meat products causing ropiness problems. The maximum growth temperatures varied between 36.6-39.8°C. The maximum growth temperature of lactobacilli seemed to be an unstable character. Single lactobacilli colonies were able to grow above the actual maximum growth temperature, which is determined as the edge of continuous growth of the bacteria. The significance of this phenomenon needs further study.

The microbiological quality of smoked and charred Baltic herrings from two different processing plants was studied after preparation and after storage for 24, 48 and 96 h at 4 and 20°C. One of the processing plants used traditional processing methods and the other a modern processing technology. No significant increase in aerobic plate counts (APCs) was observed during storage of smoked herrings at 4°C; after 96 h the mean APC was 1.7 × 10 2 CFU/g. The mean APC of charred herrings increased markedly at 4°C within 48 h, and after 96 h was 2.4 × 10 4 CFU/g. At 20°C the mean APCs of smoked and charred herrings increased markedly within 24 h, and after 96 h were 1.0 × 10 8 and 1.7 × 10 9 CFU/g, respectively. At 20°C, high coliforms and fecal streptococci counts were found in some samples and high Staphylococcus aureus counts in 2 samples. The microbiological quality of smoked herrings was better than that of charred herrings both after processing and during storage. Bacterial numbers of smoked herrings prepared in a modern steel oven were lower than those of herrings prepared in a traditional tiled oven. The mean APC of charred herrings was, however, higher when the modern continuous-operating line was used compared to the traditional method. On the continuous-operating line, heavy bacterial contamination occurred during the salting stage. The salting procedure was therefore changed by cooling the brine. When chilled brine was used, the mean APC of charred herrings was lower than the corresponding mean for the traditional method.

The microbiological and sensory quality of cabbage casserole and mixed vegetable salad with mayonnaise was assessed after production, on the sell-by date and 7 d later. Samples were taken directly from five different plants, stored at 4°C and analyzed by three different laboratories. Sell-by periods were 8 to 14 d after the day of production. No Bacillus cereus , Clostridium perfringens , Staphylococcus aureus (salad), fecal streptococci or coliforms (casserole) were detected. Casseroles had median aerobic plate counts (APC) of 1.5 × 10 2 , 3.3 × 10 2 and 4.5 × 10 3 cfu/g on different analysis times. Yeasts were detected in some casseroles on the sell-by dates. A few more had yeasts and/or molds a week later. Taste, odor, consistency and appearance scores showed a steady decrease during storage. Nine casseroles were deemed unfit for human consumption 7 d after the sell-by dates. Main defects were sliminess and acid, fermented taste and visible mold spots. Salads had a median APC of 5.2 × 10 3 cfu/g after production, which remained constant during storage. Salads from all companies contained lactobacilli and counts increased slightly during storage. Molds were encountered in samples of only one company and yeasts primarily of another. Median sensory scores decreased slightly during storage. One salad was deemed unfit on the sell-by date and six a week later. Main defects were musty and/or fermented taste and odor and watery consistency. Linear regression equations between taste and log 10 microbial counts showed very low or no correlation. Also, the counts of sensorially unfit samples varied from low to high.