Spoilage Bacteria in Canned Foods: II. Sulfide Spoilage Bacteria in Canned Mushrooms and a Versatile Medium for the Enumeration of Clostridium nigrificans

Clostridium nigrificans was found to be a spoilage organism of canned mushrooms in Taiwan. A modified beef extract tryptone iron medium, both in broth and agar form, was designed for the detection and recovery of the organisms. A procedure of simple plate counting method of C. nigrificans was established.     

PCR Detection of Thermophilic Spore-Forming Bacteria Involved in Canned Food Spoilage

Thermophilic bacteria that form highly heat-resistant spores constitute an important group of spoilage bacteria of low-acid canned food. A PCR assay was developed in order to rapidly trace these bacteria. Three PCR primer pairs were designed from rRNA gene sequences. These primers were evaluated for the specificity and the sensitivity of detection. Two primer pairs allowed detection at the species level of Geobacillus stearothermophilus and Moorella thermoacetica/thermoautrophica. The other pair allowed group-specific detection of anaerobic thermophilic bacteria of the genera Thermoanaerobacterium, Thermoanaerobacter, Caldanerobium and Caldanaerobacter. After a single enrichment step, these PCR assays allowed the detection of 28 thermophiles from 34 cans of spoiled low-acid food. In addition, 13 ingredients were screened for the presence of these bacteria. This PCR assay serves as a detection method for strains able to spoil low-acid canned food treated at 55°C. It will lead to better reactivity in the canning industry. Raw materials and ingredients might be qualified not only for quantitative spore contamination, but also for qualitative contamination by highly heat-resistant spores.     

The Detection of Microbial Spoilage in Canned Foods Using Thin-layer Chromatography

Thin-layer chromatography was investigated as an inexpensive alternative to traditional microbiological techniques for the detection of microbial growth in canned vegetables. It was compared with culture methods, pH determination and direct microscopy in batches of canned vegetables with a known incidence of spoilage.     

聚合酶链式反应快速鉴定啤酒有害菌研究

建立了PCR快速鉴定啤酒有害菌的新方法。用基于抗酒花基因horA部分序列的特异引物对啤酒污染乳酸菌进行PCR检测,灵敏度可达到3个细胞(CFU),样品的预培养需12~16h。啤酒有害菌检测所需时间从传统的5d减少到24h。     

The Mechanism of Microbiological Leaker Spoilage of Canned Foods: A Review

S ummary : This review summarizes the work on the subject carried out mainly in the authors'laboratories but also in the associated laboratories of Metal Box Co. Ltd., London, and Plat Manufaktor, Malmö, Sweden. Special attention is paid to the mechanism of bacterial reinfection and how it is influenced by deviations in can construction or can handling procedures. Methods of preventing bacterial reinfection at the most critical points in the canning operation are considered and certain guiding principles are derived.     

Extracellular Enzymic Activity of Poultry Spoilage Bacteria

The extracellular enzymic activity has been studied of 224 strains of bacteria isolated mainly at 1° from spoiling chickens and turkeys and from poultry processing plants. The isolates comprised 44 strains of pigmented Pseudomonas , 57 strains of nonpigmented Pseudomonas , 29 strains of Ps. putrefaciens , 50 strains of oxidase positive Acinetobacter and 44 strains of oxidase negative Acinetobacter. None of the strains showed any significant activity against dextrin, starch, glycogen, inulin, dextran, xylan or pectin. Proteolytic activity was found mainly amongst 2 groups of pigmented pseudo-monads, and Ps. putrefaciens. Nuclease activity was found particularly amongst strains of Ps. putrefaciens and the oxidase negative Acinetobacter strains isolated from spoiling poultry. Almost all of the strains showed lipolytic activity when tested with tributyrin and a proportion of strains could also attack chicken fat. This latter property was particularly evident amongst the nonpigmented Pseudomonas strains.     

Cellulolytic Bacteria Associated with Sloughing Spoilage of California Ripe Olives

Sloughing spoilage of California ripe olives during processing is characterized by severe softening, skin rupture, and flesh sloughing. It was assumed that cellulolytic activity was responsible for skin rupture and sloughing of flesh, and so a deliberate search was made for cellulolytic bacteria from olives undergoing sloughing spoilage. A bacterium identified as Cellulomonas flavigena was highly cellulolytic, attacking filter paper, carboxymethyl cellulose (CMC) gel, and olive tissue. Other bacteria attacking CMC, but not filter paper, enhanced the activity of the Cellulomonas strain when grown in mixed culture, although they did not, in pure culture, have any effect on filter paper. These latter cultures (all degraded olive tissue) represented the genera Xanthomonas, Aerobacter, and Escherichia. Other noncellulolytic bacteria belonging to the genera Alcaligenes, Kurthia, and Micrococcus also were used for study of mixed culture fermentation of cellulose by C. flavigena. Cellobiose accumulation at levels of 1.0% (w/v) and above suppressed growth of C. flavigena.     

Effect of Carbon Dioxide on Growth of Meat Spoilage Bacteria

The ability of CO₂ to inhibit respiration and growth of representative strains of seven species of meat spoilage bacteria was examined. Enterobacter and Microbacterium thermosphactum were unaffected by CO₂. Both respiration and growth of the other species were inhibited. With four of the species (fluorescent and nonfluorescent Pseudomonas, Alteromonas putrefaciens, and Yersinia enterocolitica), the inhibition pattern in a complex medium was similar, and inhibition was incomplete and reached a maximum level at comparatively low concentrations of CO₂. With Acinetobacter, inhibition continued to increase with increasing CO₂ concentration. The degree of inhibition with a constant concentration of CO₂ in solution increased with decreasing temperature for all CO₂-susceptible species except the nonfluorescent Pseudomonas. Anaerobic growth of CO₂-susceptible facultative anaerobes was unaffected by CO₂.     

Anaerobic Fish Spoilage by Bacteria I. Biochemical Changes in Herring Extracts

Water extracts of herring fillets were used as laboratory model substrates for the study of anaerobic bacterial spoilage of fish stored in bulk. The organisms studied ( Enterobacter sp., str. NTHC 151, Proteus sp., str. NTHC 153, and Aeromonas sp., str. NTHC 154) were selected for by an enrichment method designed to isolate the bacteria having the highest anaerobic growth yields in these herring extracts. The extracts were then inoculated with pure cultures of the bacteria and incubated anaerobically at 15°C. Chemical analyses of the extracts were carried out at the start and at the end of the incubation period. The compounds determined accounted for 88% of total carbon and 93% of total nitrogen of the sterile extracts. Ribose (free and bound), free hexoses and lactate were the main substrates for the growth of the bacteria. These compounds were converted to acetate and CO₂; hydrogen liberated by these processes was used for the quantitative reduction of trimethylamine oxide to trimethylamine. Fermentation balances support the contention that the biochemical changes observed represent the quantitative dominating chemical events in the herring extracts as a result of the development of the spoilage bacteria.     

Bacteriological and Shelf-Life Characteristics of Canned, Pasteurized Crab Cake Mix

The bacteriological spoilage characteristics of a canned, pasteurized crab cake mix product stored at various temperatures were investigated. A large number of bacteria, both mesophilic and psychrophilic, survived the pasteurization process. Bacillus and Micrococcus were found to predominate when the product was stored at 30 C (86 F) and 18 C (64 F), whereas Alcaligenes predominated at 2 C (36 F). The product was found to be free of Escherichia coli. Bacterial counts, trimethylamine nitrogen, volatile reducing substances, and ammonia determinations were evaluated as indices of quality for the product. Close correlation was observed between bacterial counts, volatile reducing substance values, and organoleptic tests when the product was stored at 30 C (86 F). The shelf-life of the product was approximately 6 months at 2 C (36 F), 4 days at 18 C (64 F), and 27 hr at 30 C (86 F).     

Application of Bacteriocins in the Control of Foodborne Pathogenic and Spoilage Bacteria

Bacteriocins are antimicrobial peptides or proteins produced by strains of diverse bacterial species. The antimicrobial activity of this group of natural substances against foodborne pathogenic, as well as spoilage bacteria, has raised considerable interest for their application in food preservation. Application of bacteriocins may help reduce the use of chemical preservatives and/or the intensity of heat and other physical treatments, satisfying the demands of consumers for foods that are fresh tasting, ready to eat, and lightly preserved. In recent years, considerable effort has been made to develop food applications for many different bacteriocins and bacteriocinogenic strains. Depending on the raw materials, processing conditions, distribution, and consumption, the different types of foods offer a great variety of scenarios where food poisoning, pathogenic, or spoilage bacteria may proliferate. Therefore, the effectiveness of bacteriocins requires careful testing in the food systems for which they are intended to be applied against the selected target bacteria. This and other issues on application of bacteriocins in foods of dairy, meat, seafood, and vegetable origins are addressed in this review.     

Coexistence of Lactic Acid Bacteria and Potential Spoilage Microbiota in a Dairy Processing Environment

Microbial contamination in food processing plants can play a fundamental role in food quality and safety. In this study, the microbiota in a dairy plant was studied by both 16S rRNA- and 26S rRNA-based culture-independent high-throughput amplicon sequencing. Environmental samples from surfaces and tools were studied along with the different types of cheese produced in the same plant. The microbiota of environmental swabs was very complex, including more than 200 operational taxonomic units with extremely variable relative abundances (0.01 to 99%) depending on the species and sample. A core microbiota shared by 70% of the samples indicated a coexistence of lactic acid bacteria with a remarkable level of Streptococcus thermophilus and possible spoilage-associated bacteria, including Pseudomonas, Acinetobacter, and Psychrobacter, with a relative abundance above 50%. The most abundant yeasts were Kluyveromyces marxianus, Yamadazyma triangularis, Trichosporon faecale, and Debaryomyces hansenii. Beta-diversity analyses showed a clear separation of environmental and cheese samples based on both yeast and bacterial community structure. In addition, predicted metagenomes also indicated differential distribution of metabolic pathways between the two categories of samples. Cooccurrence and coexclusion pattern analyses indicated that the occurrence of potential spoilers was excluded by lactic acid bacteria. In addition, their persistence in the environment can be helpful to counter the development of potential spoilers that may contaminate the cheeses, with possible negative effects on their microbiological quality.     

Drug Resistance of Enteric Bacteria

A nontransferable R₂₁ (TC) factor was obtained by transduction of R₁₀ (TC.CM.SM.SA) with phage epsilon in group E Salmonella. The R₂₁ (TC) factor acquired transmissibility by the normal conjugal process when group E Salmonella strains harboring R₂₁ (TC) factor were infected with wild-type F or R₁₆ (CM) factor. This transmissibility at high frequency was accounted for by the formation of the recombinant F TC and R₁₀ (CM) TC factors. The F TC and R₁₆ (CM) TC factors were genetically the same as the original F and R₁₆ (CM) factors, except for the ability to confer TC resistance. In the transduction of F TC factor with phage P1, a dF TC (d: defective) factor was obtained that was defective in many F properties, such as the ability to introduce host chromosome and produce male substance, but was capable of transducing TC resistance (dF TC-infection) at low frequency.