Origin and ecological selection of core and food-specific bacterial communities associated with meat and seafood spoilage

The microbial spoilage of meat and seafood products with short shelf lives is responsible for a significant amount of food waste. Food spoilage is a very heterogeneous process, involving the growth of various, poorly characterized bacterial communities. In this study, we conducted 16S ribosomal RNA gene pyrosequencing on 160 samples of fresh and spoiled foods to comparatively explore the bacterial communities associated with four meat products and four seafood products that are among the most consumed food items in Europe. We show that fresh products are contaminated in part by a microbiota similar to that found on the skin and in the gut of animals. However, this animal-derived microbiota was less prevalent and less abundant than a core microbiota, psychrotrophic in nature, mainly originated from the environment (water reservoirs). We clearly show that this core community found on meat and seafood products is the main reservoir of spoilage bacteria. We also show that storage conditions exert strong selective pressure on the initial microbiota: alpha diversity in fresh samples was 189±58 operational taxonomic units (OTUs) but dropped to 27±12 OTUs in spoiled samples. The OTU assemblage associated with spoilage was shaped by low storage temperatures, packaging and the nutritional value of the food matrix itself. These factors presumably act in tandem without any hierarchical pattern. Most notably, we were also able to identify putative new clades of dominant, previously undescribed bacteria occurring on spoiled seafood, a finding that emphasizes the importance of using culture-independent methods when studying food microbiota.     

Lactococcus piscium: a psychrotrophic lactic acid bacterium with bioprotective or spoilage activity in food—a review

The genus Lactococcus comprises 12 species, some known for decades and others more recently described. Lactococcus piscium, isolated in 1990 from rainbow trout, is a psychrotrophic lactic acid bacterium, probably disregarded because most of the strains are unable to grow at 30°C. During the last 10 years, this species has been isolated from a large variety of food: meat, seafood and vegetables, mostly packed under vacuum (VP) or modified atmosphere (MAP) and stored at chilled temperature. Recently, culture‐independent techniques used for characterization of microbial ecosystems have highlighted the importance of Lc. piscium in food. Its role in food spoilage varies according to the strain and the food matrix. However, most studies have indicated that Lc. piscium spoils meat, whereas it does not degrade the sensory properties of seafood. Lactococcus piscium strains have a large antimicrobial spectrum, including Gram‐positive and negative bacteria. In various seafoods, some strains have a protective effect against spoilage and can extend the sensory shelf‐life of the products. They can also inhibit the growth of Listeria monocytogenes, by a cell‐to‐cell contact‐dependent. This article reviews the physiological and genomic characteristics of Lc. piscium and discusses its spoilage or protective activities in food.     

A rapid chemical spot test for the detection of lactic acid as an indicator of microbial spoilage in preserved foods

A ckland , M.R. & R eeder , J.E. 1984. A rapid chemical spot test for the detection of lactic acid as an indicator of microbial spoilage in preserved foods. Journal of Applied Bacteriology 56 , 415–419.
A rapid method for the detection of lactic acid in preserved foods has been developed, based upon a chemical spot test which does not require solvent extraction or derivatisation of the lactic acid in the sample. The test can be completed within 5 min and was shown to confirm microbial spoilage detected by cultural techniques in a range of preserved foods. In addition the test was able to indicate microbial spoilage in samples where cultural techniques failed because the spoilage organisms were dead. The test may not be appropriate for products which have a naturally high lactic acid content.     

A rapid chemical spot test for the detection of lactic acid as an indicator of microbial spoilage in preserved foods

A rapid method for the detection of lactic acid in preserved foods has been developed, based upon a chemical spot test which does not require solvent extraction or derivatisation of the lactic acid in the sample. The test can be completed within 5 min and was shown to confirm microbial spoilage detected by cultural techniques in a range of preserved foods. In addition the test was able to indicate microbial spoilage in samples where cultural techniques failed because the spoilage organisms were dead. The test may not be appropriate for products which have a naturally high lactic acid content.     

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.     

Lactic acid bacteria associated with vacuum-packed cooked meat product spoilage: population analysis by rDNA-based methods

AIM: To determine the lactic acid bacteria (LAB) implicated in bloating spoilage of vacuum-packed and refrigerated meat products. METHODS AND RESULTS: A total of 18 samples corresponding to four types of meat products, with and without spoilage symptoms, were studied. In all, 387 colonies growing on de Man, Rogosa and Sharpe, yeast glucose lactose peptone and trypticase soy yeast extract plates were identified by internal spacer region (ISR), ISR-restriction fragment length polymorphism and rapid amplified ribosomal DNA restriction analysis profiles as Lactobacillus (37%), Leuconostoc (43%), Carnobacterium (11%), Enterococcus (4%) and Lactococcus (2%). Leuconostoc mesenteroides dominated the microbial population of spoiled products and was always present at the moment bloating occurred. Lactobacillus sakei, Lactobacillus plantarum and Lactobacillus curvatus were found in decreasing order of abundance. The analysis of two meat products, 'morcilla' and 'fiambre de magro adobado' obtained from production lines revealed a common succession pattern in LAB populations in both products and showed that Leuc. mesenteroides became the main species during storage, despite being below the detection level of culture methods after packing. CONCLUSIONS: Our results pointed to Leuc. mesenteroides as the main species responsible for bloating spoilage in vacuum-packed meat products. SIGNIFICANCE AND IMPACT OF THE STUDY: Prevention of bloating spoilage in vacuum-packed cooked meat products requires the sensitive detection of Leuc. mesenteroides (i.e. by PCR).     

Why fruit rots: theoretical support for Janzen's theory of microbe–macrobe competition

We present a formal model of Janzen''s influential theory that competition for resources between microbes and vertebrates causes microbes to be selected to make these resources unpalatable to vertebrates. That is, fruit rots, seeds mould and meat spoils, in part, because microbes gain a selective advantage if they can alter the properties of these resources to avoid losing the resources to vertebrate consumers. A previous model had failed to find circumstances in which such a costly spoilage trait could flourish; here, we present a simple analytic model of a general situation where costly microbial spoilage is selected and persists. We argue that the key difference between the two models lies in their treatments of microbial dispersal. If microbial dispersal is sufficiently spatially constrained that different resource items can have differing microbial communities, then spoilage will be selected; however, if microbial dispersal has a strong homogenizing effect on the microbial community then spoilage will not be selected. We suspect that both regimes will exist in the natural world, and suggest how future empirical studies could explore the influence of microbial dispersal on spoilage.     

In vitro and in situ growth characteristics and behaviour of spoilage organisms associated with anaerobically stored cooked meat products

AIMS: Understanding spoilage caused by different types of spoilage organisms, associated with vacuum-packaged sliced cooked meat products (CMP). METHODS AND RESULTS: First, strains were characterized in a broth at 7 degrees C under anaerobic conditions to compare their growth rate, acidifying character and metabolite production under conditions simulating refrigerated vacuum-packaged conditions. Brochotrix thermosphacta grew faster than the lactic acid bacteria (LAB). Within the group of the LAB, all strains grew fast except Leuconostoc mesenteroides subsp. dextranicum and Leuconostoc carnosum. Secondly, the organisms were inoculated on a model cooked ham to better understand the relationship between spoilage, microbial growth, pH, metabolite production and accompanying sensory changes. Most rapidly growing strains were Leuc. mesenteroides subsp. mesenteroides followed by B. thermosphacta, while Leuc. mesenteroides subsp. dextranicum and Leuc. carnosum grew very slowly compared with the other LAB. Brochotrix thermosphacta caused sensory deviations at a lower cell number compared with the LAB. The related pH changes, metabolite production and sensory perception are presented. CONCLUSIONS: In this pure culture study, B. thermosphacta and Leuc. mesenteroides subsp. mesenteroides had the highest potential to cause rapid spoilage on CMP. SIGNIFICANCE AND IMPACT OF THE STUDY: A systematic study on the behaviour of spoilage organisms on a model cooked ham to establish the relationship between microbial growth, pH, metabolite formation and organoleptic deviations.     

Biosensors in fish production and quality control

Fishery products are important not only from a nutritional point of view, but also as an item of international trade and foreign exchange earner for a number of countries in the world. Fish and shellfish are highly perishable, and prone to vast variations in quality due to differences in species, environmental habitats, feeding habits, etc. In addition, they can also function as carriers of several microbial and other health hazards. Therefore, maintenance of quality is of utmost importance in production and trade of fishery products. Most of the current quality control techniques are time consuming and cumbersome. There is an excellent scope for the application of biosensors in the seafood industry including the rapidly expanding aquaculture operations for fast assessment of quality. This article discusses the scope of applications biosensors in the seafood industry.     

Characterization of the bacterial spoilage flora in marinated pork products

Aims: To investigate the microbiota in marinated, vacuum‐packed pork and to characterize isolated bacteria with regard to their spoilage potential. Methods and Results: Laboratory marinated pork meat and commercial products from three Norwegian producers were examined. Lactic acid bacteria dominated in all products at the expiration date. The flora in marinated products was similar only for products from the same plant. Strains of Lactobacillus algidus, Lactobacillus sakei, Lactobacillus curvatus, Carnobacterium divergens, Carnobacterium maltaromaticum, Leuconostoc mesenteroides, Leuconostoc carnosum and Leuconostoc sp. were isolated and tested for their spoilage potential. Samples inoculated with Lact. algidus or Leuc. mesenteroides were rated as most unpleasant by randomly selected people. A sensory panel scored samples with Lact. algidus highest for sour and intense odour. Lactobacillus algidus was found in products from two out of three production plants. Culture‐independent DNA isolation confirmed that cultivation on Blood agar at 20°C yielded a representative picture of the total flora in marinated flintsteak. Conclusions: Lactobacillus algidus may be an important, but underestimated, spoilage organism that needs to be focused on more when spoilage of vacuum‐packed meat is considered. Significance and Impact of the Study: Routine microbial testing may have to be revised in order to detect spoilage LAB that are unable to grow under currently used conditions.     

Bacterial spoilage of wine and approaches to minimize it

Bacteria are part of the natural microbial ecosystem of wine and play an important role in winemaking by reducing wine acidity and contributing to aroma and flavour. Conversely, they can cause numerous unwelcome wine spoilage problems, which reduce wine quality and value. Lactic acid bacteria, especially Oenococcus oeni, contribute positively to wine sensory characters, but other species, such as Lactobacillus sp. and Pediococcus sp can produce undesirable volatile compounds. Consequences of bacterial wine spoilage include mousy taint, bitterness, geranium notes, volatile acidity, oily and slimy-texture, and overt buttery characters. Management of wine spoilage bacteria can be as simple as manipulating wine acidity or adding sulfur dioxide. However, to control the more recalcitrant bacteria, several other technologies can be explored including pulsed electric fields, ultrahigh pressure, ultrasound or UV irradiation, and natural products, including bacteriocins and lysozyme.     

High-pressure processing – effects on microbial food safety and food quality

High-pressure processing (HPP) is a nonthermal process capable of inactivating and eliminating pathogenic and food spoilage microorganisms. This novel technology has enormous potential in the food industry, controlling food spoilage, improving food safety and extending product shelf life while retaining the characteristics of fresh, preservative-free, minimally processed foods. As with other food processing methods, such as thermal processing, HPP has somewhat limited applications as it cannot be universally applied to all food types, such as some dairy and animal products and shelf-stable low-acid foods. Herein, we discuss the effects of high-pressure processing on microbial food safety and, to a lesser degree, food quality.     

A rapid method for the evaluation of both extrinsic and intrinsic contamination and resulting spoilage of water-in-oil emulsions

AIMS: To develop a method for studying the microbial spoilage of water-in-oil emulsions and to use this to investigate (i) the intrinsic stability of water-in-oil formulations and (ii) Pseudomonas aeruginosa SP1-induced spoilage of a proprietary emulsion. METHODS AND RESULTS: Aliquots of test emulsion were placed into wells of a microtitre plate and the opacity (492 nm) monitored at 120-min intervals over several hours. Cracking of the emulsion was associated with marked reductions in opacity. Rate and extent of change in O.D. could be used as indicators of spoilage. Spoilage of a laboratory emulsion formulation was investigated where microorganisms with demonstrated spoilage potential were incorporated either into the water phase prior to emulsification or where the proportion of contaminated water droplets was varied by dilution of contaminated emulsion with a sterile formulation. Results suggested that the route of introduction was a critical determinant of the probability of gross spoilage. Ps. aeruginosa SP1-induced spoilage of a proprietary formulation was found to be independent of growth in the formulation; rather it was attributed to the presence of a heat-labile extracellular spoilage-factor that was protease labile and possessed both lipase and polysorbate hydrolytic activity. Such spoilage potential was unique to one Ps. aeruginosa culture filtrate amongst five pseudomonads tested. SIGNIFICANCE AND IMPACT OF THE STUDY: The method is both rapid and reproducible, enables evaluation of the effects of route of contamination upon emulsion spoilage and has potential application in formulation development for cosmetic, pharmaceutical and food products.     

Analyzing the relation between the microbial diversity of DaQu and the turbidity spoilage of traditional Chinese vinegar

Vinegar is a traditional fermented condiment, and the microbial diversity of DaQu makes the quality of vinegar products. Recently, turbidity spoilage of vinegar sharply tampered with the quality of vinegar. In this study, the relation between the microbial diversity of DaQu and turbidity spoilage of vinegar was analyzed by plating technique, PCR–denaturing gradient gel electrophoresis (DGGE), and high-performance liquid chromatography (HPLC). The 16S rRNA sequencing and DGGE analysis indicated that Bacillus (Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus thuringiensis) and Lactobacillus (including Lactobacillus acidipiscis and Lactobacillus pobuzihii) species were the dominant contaminants in vinegar products. Meanwhile, DGGE analysis showed that the dominant bacteria in DaQu belonged to genera Bacillus, Lactobacillus, Pseudomonas, Weissella, Saccharopolyspora, Enterobacter, and Pantoea. However, only two yeast species (Pichia kudriavzevii and Saccharomycopsis fibuligera) and seven mold species including Aspergillus oryzae, Aspergillus niger, Aspergillus candidus, Rhizopus microspores, Eurotium herbariorum, Absidia corymbifera, and Eupenicillium javanicum were detected in the DaQu. The population level of fungi was below 5 log CFU/g in DaQu. The chemical and physical properties of vinegar and sediments were also determined. On the basis of a combined microbial diversity-chemical analysis, we demonstrated that turbidity spoilage of vinegar was a result of cooperation among the low population level and abundance of fungal species in DaQu, the suitable climate conditions, and the contaminants in vinegar. This is the first report to analyze the relation between the microbial diversity of DaQu and turbidity spoilage of vinegar.     

Hydration and pH of Microbially Spoiling Beef

S ummary . The extract-release volume (ERV) technique was used to study the relationship between the hydration and pH of ground beef undergoing microbial spoilage at refrigeration temperatures. The ERV of samples of meat at various stages of freshness and spoilage was determined after adjusting their pH values to between 4.5 and 7.0. ERV responded instantly to pH change and, regardless of the microbial quality of the meat, minimum hydration or maximum ERV occurred at pH 5.5. Since most of the decrease in ERV during the spoilage of beef resulted from the increase in hydration of its proteins, it was concluded that the significant correlation noted previously between ERV and the bacterial quality of beef is highly dependent on the increase in pH value of the meat during spoilage.     

Lactic acid bacteria associated with a heat-processed pork product and sources of variation affecting chemical indices of spoilage and sensory characteristics

Aims:  To evaluate the potential for developing a quality index for a Danish modified atmosphere packaged (MAP) heat-processed and naturally contaminated pork meat product stored at 5°C.
Methods and Results:  The composition of the predominating microflora and changes in contents of tyramine, arginine, organic acids and sensory characteristics were analysed. The microflora was predominated by Lactobacillus sakei , Leuconostoc carnosum and Carnobacterium divergens . The presence of each species varied between products and batches resulting in limited usefulness of the concentrations of these bacteria or their metabolites as indices of quality. Furthermore, the three species differed in their metabolic activities as shown by use of a model meat extract. However, when MAP storage of the processed pork product was followed by aerobic storage then acetic acid showed some potential as a chemical indicator of sensory quality.
Conclusion:  Variation in processing parameters and spoilage microbiota limited the usefulness of concentrations of micro-organisms and their metabolites as indices of spoilage for the studied processed MAP pork product.
Significance and Impact of the Study:  The present study contributes to an understanding of the difficulties experienced in developing quality indices to be used in the control of microbial spoilage of processed MAP meat products.     

一株食醋污染菌CICC 10774 的鉴定及其生长代谢特性

【目的】对食醋污染菌CICC 10774进行多相分类学鉴定,并对其生长特征和代谢产物进行研究。【方法】通过16S r RNA基因序列系统发育学分析,结合形态特征和生理生化特性确定该菌株的分类学地位。通过分光光度法测定菌株生长的最适温度和最适p H值,确定其最佳培养条件。采用HPLC测定该菌株代谢产物。【结果】多相鉴定分析表明菌株CICC 10774为耐酸乳杆菌(Lactobacillus acetotolerans),革兰氏染色呈阳性,兼性厌氧生长,具有明胶酶活性,能够利用葡萄糖、果糖、甘露糖、N-乙酰葡萄糖胺、熊果苷、七叶灵、水杨苷、纤维二糖、海藻糖和龙胆二糖作为碳源底物生长。生长代谢特性研究表明,CICC 10774的最适生长温度为37°C,最适p H值为5.0,代谢产物主要为醋酸和乳酸,是一株典型的耐酸菌。【结论】对引起食醋污染的耐酸乳杆菌CICC 10774生长代谢特征进行了研究,为食醋生产企业生产过程的微生物控制提供理论基础。     

Proteomics as a tool for the investigation of seafood and other marine products

The state-of-the-art and future trends of the application of proteomics to seafood and other marine products are reviewed. Consumers' demands for seafood products have increased in the recent years and this situation has underlined the need to guarantee the safety, traceability, authenticity, and health benefits of such products. The increasing presence of commercially available aquaculture products has also prompted the seafood industry to face newer challenges. In this sense, a review of the present status and perspectives of the application of proteomics in the development of newer biotechnology products of marine origin is given.     

Bacteriocins from lactic acid bacteria and their potential in the preservation of fruit products

Bacteriocins produced by lactic acid bacteria (LAB) are well-recognized for their potential as natural food preservatives. These antimicrobial peptides usually do not change the sensorial properties of food products and can be used in combination with traditional preservation methods to ensure microbial stability. In recent years, fruit products are increasingly being associated with food-borne pathogens and spoilage microorganisms, and bacteriocins are important candidates to preserve these products. Bacteriocins have been extensively studied to preserve foods of animal origin. However, little information is available for their use in vegetable products, especially in minimally processed ready-to-eat fruits. Although, many bacteriocins possess useful characteristics that can be used to preserve fruit products, to date, only nisin, enterocin AS-48, bovicin HC5, enterocin 416K1, pediocin and bificin C6165 have been tested for their activity against spoilage and pathogenic microorganisms in these products. Among these, only nisin and pediocin are approved to be commercially used as food additives, and their use in fruit products is still limited to certain countries. Considering the increasing demand for fresh-tasting fruit products and concern for public safety, the study of other bacteriocins with biochemical characteristics that make them candidates for the preservation of these products are of great interest. Efforts for their approval as food additives are also important. In this review, we discuss why the study of bacteriocins as an alternative method to preserve fruit products is important; we detail the biotechnological approaches for the use of bacteriocins in fruit products; and describe some bacteriocins that have been tested and have potential to be tested for the preservation of fruit products.     

The role of seafood in bacterial foodborne diseases

Pathogenic bacteria, when present in marine seafood and in fresh cultured products, are usually found at fairly low levels, and where these products are adequately cooked, food safety hazards are insignificant. A few bacteria associated with faecal contamination of seafood continue to pose a large-scale health threat through seafood.