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1.
Food Chem ; 340: 128104, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33010644

RESUMO

Bacteria release membrane vesicles into the extracellular environment but which activity is unclear. We investigated the applications of extracellular vesicles (EVs) isolated from probiotic Lactobacillus plantarum to protect tuna fish against spoilage and quality loss in this study. A significant difference was found in EVs size obtained from L. plantarum after 8, 24, and 48 hr incubation. The L. plantarum-derived EVs were collected and used to confirm the anti-bacterial activity versus Shewanella putrefaciens. Finally, the tuna fish was stored at 4 °C for 5 days after coating with EVs or sodium erythorbate, and the quality indexes were assayed. Results indicated that EVs markedly inhibited oxidation reaction, total volatile base nitrogen (TVBN), peroxide value (PV), malondialdehyde (MDA), and bacteria levels. These results finding out that EVs from L. plantarum may have potential for application in food storage technology. Overall, we indicated this new material may be developed as an anti-bacterial agent for prolonging the shelf life of tuna fish.


Assuntos
Antibacterianos/farmacologia , Vesículas Extracelulares , Produtos Pesqueiros/microbiologia , Microbiologia de Alimentos/métodos , Lactobacillus plantarum/citologia , Animais , Antibacterianos/química , Armazenamento de Alimentos , Malondialdeído/metabolismo , Oxirredução , Probióticos , Shewanella putrefaciens/efeitos dos fármacos , Shewanella putrefaciens/crescimento & desenvolvimento , Atum/microbiologia
2.
Int J Food Microbiol ; 336: 108895, 2021 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-33075693

RESUMO

Fresh Atlantic salmon (Salmo salar) represents a healthy, nutritious food with global distribution and increasing consumption and economic value. Contaminating Listeria monocytogenes in fresh salmon represents a health hazard to consumers, is linked to extensive product recalls and is a major challenge for salmon processors. Verdad N6, a commercially available buffered vinegar, was evaluated as a treatment for raw salmon fillets either alone or in combination with the antimicrobial peptide nisin, with regard to anti-listerial effects under processing and storage, and influence on sensory quality and background microbiota. Salmon fillets were surface contaminated with L. monocytogenes and immersed in solutions of Verdad N6 or treated with nisin or a combination of these two treatments. Levels of L. monocytogenes were determined during vacuum-pack refrigerated storage. The use of Verdad N6 resulted in increased lag times and substantially reduced growth of L. monocytogenes. The inhibitory effects were dependent on Verdad N6 levels, immersion time, and storage time and temperature. A 5 s immersion in 10% Verdad N6 solution at 4 °C reduced growth of L. monocytogenes from log 2.8 to log 1 after 12 days of storage. Nisin (0.2-1 ppm) had listericidal effects up to 1 log but did not inhibit regrowth when used alone. Appropriate combinations of Verdad N6 and nisin led to L. monocytogenes levels no higher after 12 days of storage than the initial levels. The inhibitory effects were markedly lower at 7 °C than at 4 °C. Salmon with Verdad N6 showed reduced levels of total counts during storage indicating a longer shelf-life, and a shift in the dominating bacteria with reduced and increased relative levels of Enterobacteriaceae and lactic acid bacteria, respectively. Sensory analyses of raw and cooked Verdad N6 treated a non-treated salmon resulted in small differences. In summary, Verdad N6 is an option for production of high-quality raw salmon with increased shelf-life and enhanced food safety through its Listeria inhibiting effects. The application of Verdad N6 in combination with nisin treatment can further reduce the listeria-risks of these products.


Assuntos
Ácido Acético/farmacologia , Antibacterianos/farmacologia , Produtos Pesqueiros/microbiologia , Armazenamento de Alimentos/métodos , Listeria monocytogenes/efeitos dos fármacos , Nisina/farmacologia , Salmo salar/microbiologia , Animais , Contagem de Colônia Microbiana , Microbiologia de Alimentos , Alimentos Crus/microbiologia , Vácuo
3.
Lett Appl Microbiol ; 71(4): 359-368, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32713031

RESUMO

Staphylococci from Sheedal of Northeast India was isolated, identified and characterized. All the isolated staphylococci were found to be coagulase negative. Based on the rpoB gene sequences followed by analysis using NCBI-BLAST software, seven species of Staphylococcus namely, S. piscifermentans, S. condimenti, S. arlettae, S. sciuri, S. warneri, S. nepalensis and S. hominis were recognized. Phylogenetic analyses revealed three major cluster groups. All the seven Staphylococcus showed their NaCl tolerance from 2 to 8%. No species was able to grow at 55°C. Except S. arlettae and S. sciuri, all the isolated staphylococcal species exhibited growth at pH 4-8. No isolated species was able to ferment mannitol, sucrose and arabinose. All the species exhibited moderate to maximum proteolytic and lipolytic activities. All the seven species were found to be sensitive to the antibiotics, namely, erythromycin, norfloxacin, ampicillin, streptomycin and vancomycin, whereas all were resistant to co-trimoxazole. Only S. piscifermentans was found antagonist to Salmonella enterica, Escherichia coli and Bacillus subtilis, although the clear zone was minimal. All the staphylococcal species except S. arlettae and S. sciuri exhibited hydrophobicity ranging from 25 to 66%. The observed characteristics of isolated Staphylococci from Sheedal revealed their role in fish fermentation.


Assuntos
Alimentos e Bebidas Fermentados/microbiologia , Produtos Pesqueiros/microbiologia , Staphylococcus/isolamento & purificação , Ampicilina/farmacologia , Animais , Antibacterianos/farmacologia , Eritromicina/farmacologia , Fermentação , Peixes/microbiologia , Contaminação de Alimentos/análise , Índia , Filogenia , Staphylococcus/classificação , Staphylococcus/efeitos dos fármacos , Staphylococcus/genética
4.
PLoS One ; 15(7): e0234999, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32702039

RESUMO

Acid adaptation enhances survival of foodborne pathogens under lethal acid conditions that prevail in several food-related ecosystems. In the present study, the role of undissociated acetic acid in inducing acid resistance of Salmonella Enteritidis Phage Type 4 both in laboratory media and in an acid food matrix was investigated. Several combinations of acetic acid (0, 15, 25, 35 and 45 mM) and pH values (4.0, 4.5, 5.0, 5.5, 6.0) were screened for their ability to activate acid resistance mechanisms of pathogen exposed to pH 2.5 (screening assay). Increased survival was observed when increasing undissociated acetic acid within a range of sublethal concentrations (1.9-5.4 mM), but only at pH 5.5 and 6.0. No effect was observed at lower pH values, regardless of the undissociated acetic acid levels. Three combinations (15mM/pH5.0, 35mM/pH5.5, 45mM/pH6.0) were selected and further used for adaptation prior to inoculation in commercial tarama (fish roe) salad, i.e., an acid spread (pH 4.35 ± 0.02), stored at 5°C. Surprisingly and contrary to the results of the screening assay, none of the acid adaptation treatments enhanced survival of Salmonella Enteritidis in the food matrix, as compared to non-adapted cells (control). Further examination of the food pH value, acidulant and storage (challenge) temperature on the responses of the pathogen adapted to 15mM/pH5.0, 35mM/pH5.5 and 45mM/pH6.0 was performed in culture media. Cells adapted to 35mM/pH5.5 were unable to induce acid resistance when exposed to pH 4.35 (tarama salad pH value) at 37°C and 5°C, whereas incubation under refrigeration (5°C) at pH 4.35 sensitized 45mM/pH6.0 adapted cells against the subsequent acid and cold stress. In conclusion, pre-exposure to undissociated acetic acid affected the adaptive responses of Salmonella Enteritidis Phage Type 4 in a concentration- and pH-dependent manner, with regard to conditions prevailing during acid challenge.


Assuntos
Ácido Acético/farmacologia , Adaptação Fisiológica/efeitos dos fármacos , Bacteriófagos , Microbiologia de Alimentos , Salmonella enteritidis/virologia , Ácidos/farmacologia , Animais , Relação Dose-Resposta a Droga , Produtos Pesqueiros/microbiologia , Concentração de Íons de Hidrogênio , Refrigeração
5.
Food Chem ; 331: 127353, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32580127

RESUMO

Aroma defects limit the application of fish protein hydrolysates as flavourings. This study aimed to develop a flavour concentrate from fermented tilapia fish head hydrolysate bymaximising the Maillard reaction production of meaty and roasted aroma associated compounds. We studied the optimal conditions of the Maillard reaction of xylose with cysteine to form meat-like odorants using response surface methodology. A 3-factored and 3-leveled Box Behnken design was employed, where the independent variables were cysteine concentration (A, w/v, %), heating temperature (B, °C) and heating time (C, min). 2-Methyl-3-furanthiol and 2-furfurylthiol were used as response factors. The optimal conditions were obtained as follows: A, 0.80%; B, 183.80 °C; C, 89.34 min. Compared with the controls, Maillard reaction products enriched the meaty and roasted aroma associated compounds in the treated hydrolysate. In conclusion, the treated tilapia fish head hydrolysate may be used as a base in development of new fish-based flavourings.


Assuntos
Cisteína/química , Aromatizantes/química , Reação de Maillard , Odorantes , Tilápia/metabolismo , Xilose/química , Animais , Fermentação , Alimentos e Bebidas Fermentados , Produtos Pesqueiros/microbiologia , Proteínas de Peixes da Dieta/química , Furanos/química , Cabeça , Hidrolisados de Proteína/metabolismo , Compostos de Sulfidrila/química , Paladar , Temperatura
6.
Int J Food Microbiol ; 327: 108654, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32416377

RESUMO

A soup stock made from katsuobushi is an important element of, and the basic seasoning responsible for the taste of, traditional Japanese cuisine. Fermented and ripened katsuobushi, called karebushi, is manufactured via a repeated molding process on the katsuobushi surface. Our aim was to characterize the surface Aspergillus community and their enzymes involved in the fermentation and ripening. Five dominant Aspergillus species isolated from the karebushi surface were identified-A. amstelodami, A. chevalieri, A. pseudoglaucus, A. ruber, and A. sydowii. Analyses were performed on final molding stage-samples from different manufacturers, and 1st to 4th molding stage-samples from the same manufacturer. The composition ratios of the five Aspergillus spp. varied according to the manufacturer of the karebushi. A. amstelodami and A. chevalieri tended to be detected as dominant species when the water content of the karebushi fillet was >15% and the fat content was >3.5%, respectively. In samples from a given manufacturer, the dominant species in the final molding stage tended to be A. chevalieri and A. pseudoglaucus. Mixed molds were cultured by solid-state fermentation using katsuobushi powder medium at two different water activity (aw) levels. Crude extracts from each culture showed lipase, aminopeptidase, carboxypeptidase, and protease activities. Notably, the crude extracts cultivated at 0.85 aw showed higher protease activity toward hemoglobin and lipase activity toward p-nitrophenyl palmitate than those at 0.95 aw. These hydrolytic enzymes are probably involved in decolorization of katsuobushi and lipid degradation during the long fermentative and ripening period. In addition, mixed cultures could transform 2,6-dimethoxyphenol into 1,2,3-trimethoxybenzene, previously reported as an attractive and mild flavor component. Our results may help promote the use of desirable Aspergillus spp. as starter cultures for manufacturers to stabilize and improve the quality of fermented and ripened karebushi.


Assuntos
Aspergillus/fisiologia , Fermentação , Alimentos e Bebidas Fermentados/microbiologia , Produtos Pesqueiros/microbiologia , Microbiologia de Alimentos , Animais , Produtos Pesqueiros/normas , Hidrólise , Lipase/metabolismo
7.
Crit Rev Food Sci Nutr ; 60(7): 1228-1242, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-30676059

RESUMO

Fermentation is a traditional food preservation method and is widely used for improving food safety, shelf life, and organoleptic and nutritional attributes. Fermented fish are produced and consumed in different parts of the world and are an integral part of many food cultures. Furthermore, fermented fish are a source of interesting microbes and are an important industry in many countries. This review tries to update the types and manufacturing processes for fermented fish around the world. The emphasis is on this work related to fermented fish and their health benefits, as well as the contribution of microorganisms to their fermentation. A variety of different approaches have been used to determine and understand microbial composition and functionality. Moreover, some challenges and future research directions regarding fermented fish are also discussed in this review. Further research into fermented fish products is of crucial importance not only for the food industry but also for human health. However, extensive in vivo and toxicological studies are essential before the application of bioactive-rich fermented fish products for human health benefits.


Assuntos
Fermentação , Produtos Pesqueiros/microbiologia , Produtos Pesqueiros/normas , Peixes , Microbiologia de Alimentos , Conservação de Alimentos/normas , Inocuidade dos Alimentos , Animais , Peixes/microbiologia , Humanos
8.
Int J Food Microbiol ; 314: 108416, 2020 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-31707172

RESUMO

The population, diversity and succession of microbial communities and chemical characteristics of dried crimson snapper (Lutianus erythropterus) during storage for 50 days were investigated. The population of bacteria, yeasts and filamentous fungi in the samples were enumerated by culture methods using appropriate agar media. The amplicons of the 16S rRNA of bacteria and the ITS region of fungi were sequenced and compared with gene libraries to obtain the identity and abundance of microorganisms in the community. Free amino acids and several other chemical characteristics were determined by HPLC and corresponding chemical reaction methods. Before storage, the average counts of bacteria, yeasts and filamentous fungi in the dried fish were 3.2, 2.5 and 2.2 log CFU/g, which increased to 4.6, 3.6 and 3.9 log CFU/g, respectively after storage. Major succession in the bacterial > fungal communities occurred during storage as evidenced by a significant decline in the number and diversity of microbial communities. Predominant bacterial genera were Phytobacteria, Vibrio, Acinetobacter and Macrococcus in the freshly dried fish, which were replaced by Bacillaceae, Halomonas, Lentibacillus, Alkalibacillus after storage. The fungal community of the freshly dried fish consisted of Penicillum > Yamadazyma, Malassezia, Candida and Eurotiales with Penicillum being the most dominant. Penicillium camemberti was the most abundant fungal species in the dried fish before storage with most dominant after storage and accounted for >96% of the abundance. The succession in the microbial community was accompanied by major changes in chemical characteristics with a significant decrease in fat, and an increase in total free amino acids and total volatile basic nitrogen (TVB-N).


Assuntos
Produtos Pesqueiros/análise , Produtos Pesqueiros/microbiologia , Alimentos em Conserva/análise , Alimentos em Conserva/microbiologia , Microbiota , Aminoácidos/análise , Animais , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Bactérias/isolamento & purificação , DNA Ribossômico/genética , Gorduras/análise , Peixes , Microbiologia de Alimentos , Fungos/genética , Fungos/crescimento & desenvolvimento , Fungos/isolamento & purificação , Microbiota/genética , Nitrogênio/análise
9.
Int J Food Microbiol ; 315: 108439, 2020 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-31710972

RESUMO

The variation in microbial composition over time was assessed in biofilms formed in situ on selected non-food and food contact surfaces of meat and fish industries, previously identified as Listeria monocytogenes-positive foci. First, all samples were analysed for the detection and quantification of L. monocytogenes using ISO 11290-1 and ISO 11290-2 norms, respectively. Although the pathogen was initially detected in all samples, direct quantification was not possible. Psychrotrophic bacteria counts were among resident microbiota in meat industry samples (Meanmax = 6.14 log CFU/cm2) compared to those form fish industry (Meanmax = 5.85 log CFU/cm2). Visual analysis of the biofilms using epifluorescence microscopy revealed a trend to form microcolonies in which damaged/dead cells would act as anchoring structures. 16S rRNA gene metagenetic analysis demonstrated that, although Proteobacteria (71.37%) initially dominated the bacterial communities at one meat industry location, there was a dramatic shift in composition as the biofilms matured, where Actinobacteria (79.72%) became the major phylum present in later samples. This change was largely due to an increase of Nocardiaceae, Micrococcaceae and Microbacteriaceae. Nevertheless, for the other sampling location, the relative abundance of the dominating phylum (Firmicutes) remained consistent over the entire sampling period (Mean = 63.02%). In fish industry samples, Proteobacteria also initially dominated early on (90.69%) but subsequent sampling showed a higher diversity in which Bacteroidetes and Proteobacteria were the most abundant phyla accounting for the 48.04 and 37.98%, respectively by the last sampling period. Regardless of the location, the community profiles of the endpoint samples were similar to those reported previously. This demonstrated that in a given industrial setting there is a trend to establish a determinate biofilm structure due to the environmental factors and the constant incoming microbiota. This information could be used to improve the existing sanitisation protocols or for the design of novel strategies.


Assuntos
Biofilmes/crescimento & desenvolvimento , Produtos Pesqueiros/microbiologia , Listeria monocytogenes/isolamento & purificação , Produtos da Carne/microbiologia , Carne/microbiologia , Animais , Bacteroidetes/genética , Bacteroidetes/isolamento & purificação , Firmicutes/genética , Firmicutes/isolamento & purificação , Microbiologia de Alimentos , Indústria de Processamento de Alimentos , Listeria monocytogenes/genética , Microbiota/genética , Proteobactérias/genética , Proteobactérias/isolamento & purificação , RNA Ribossômico 16S/genética
10.
Food Microbiol ; 86: 103313, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703873

RESUMO

This study investigated the effect of phytic acid and lysozyme on the microbial composition and quality of grass carp (Ctenopharyngodon idellus) fillets stored at 4 °C. The control, 0.5 mg/mL lysozyme-treated fillets (T1), 0.5 mg/mL phytic acid-treated fillets (T2) and 0.25 mg/mL lysozyme + 0.25 mg/mL phytic acid-treated fillets (T3) were evaluated based on sensory assessment, biogenic amines, ATP-related compounds, total volatile basic nitrogen (TVB-N), and total viable counts (TVC). Changes in microbial composition were analyzed using high-throughput sequencing. Results showed that phytic acid and lysozyme treatment delayed the decrease in sensory scores, reduced the rate of degradation of IMP to Hx, inhibited the growth of microorganisms, and attenuated the increase in TVB-N and putrescine. Phytic acid exhibited better preservation effects than lysozyme and their combination was more effective than using either alone. High-throughput sequencing showed that Acinetobacter and Kocuria were the predominant bacteria in fresh grass carp, but Pseudomonas rose rapidly with storage time; Pseudomonas, Shewanella, and Aeromonas constituted the main spoilage bacteria of grass carp fillets. Lysozyme treatment significantly reduced the proportion of Shewanella and Acinetobacter, and phytic acid and the combination of phytic acid and lysozyme significantly reduced the proportion of Pseudomonas in spoiled grass carp fillets.


Assuntos
Carpas/microbiologia , Produtos Pesqueiros/microbiologia , Conservação de Alimentos/métodos , Conservantes de Alimentos/farmacologia , Microbiota/efeitos dos fármacos , Muramidase/farmacologia , Ácido Fítico/farmacologia , Acinetobacter/efeitos dos fármacos , Acinetobacter/crescimento & desenvolvimento , Aeromonas/efeitos dos fármacos , Aeromonas/crescimento & desenvolvimento , Animais , Aminas Biogênicas/análise , Conservação de Alimentos/instrumentação , Armazenamento de Alimentos , Humanos , Pseudomonas/efeitos dos fármacos , Pseudomonas/crescimento & desenvolvimento , Shewanella/efeitos dos fármacos , Shewanella/crescimento & desenvolvimento , Paladar
11.
Microb Cell Fact ; 18(1): 188, 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31690323

RESUMO

BACKGROUND: Probiotic bacteria can provide health benefits when delivered in functional foods. This study involved isolation of lactic acid bacteria (LAB) from traditionally dried and salted anchovy fish and characterization of their survival in simulated gastrointestinal digestion. Promising strains were used to prepare fermented fish sausages which were then evaluated for cytotoxicity activity against two cancer cell-lines, antidiabetic activity as determined by α-amylase and α-glucosidase inhibition, and antioxidant and proteolytic activities in vitro, as compared to non-fermented control sausages. RESULTS: Out of 85 LAB obtained, 13 isolates with high tolerance to simulated gastrointestinal digestion were obtained, which were identified as Enterococcus spp. Four E. faecium strains, one E. faecalis, and one E. durans were used separately to make fermented fish sausages. The α-amylase and α-glucosidase inhibition from fish sausages fermented by Enterococcus spp. ranged from 29.2 to 68.7% and 23.9 to 41.4%, respectively, during 21 days of storage. The cytotoxicity activities against Caco2 and MCF-7 cells of fish sausages fermented with Enterococcus spp. ranged from 18.0 to 24% and 13.9 to 27.9%, respectively. Cytotoxicity activities correlated positively with proteolysis and antioxidant activities, α-amylase and α-glucosidase inhibition activities, but negatively with the pH in fermented fish sausages. Strains also exhibited antimicrobial activity against foodborne pathogens and presented no significant concerns with regards to antibiotic resistance or virulence gene content. CONCLUSIONS: Fish sausages fermented by potential probiotic isolates of Enterococcus spp. from dried fish had valuable health-promoting benefits compared with non-fermented control sausages.


Assuntos
Enterococcus faecalis , Enterococcus faecium , Enterococcus , Produtos Pesqueiros/microbiologia , Microbiologia de Alimentos , Probióticos , Linhagem Celular Tumoral , Diabetes Mellitus/terapia , Enterococcus/isolamento & purificação , Enterococcus/metabolismo , Enterococcus faecalis/isolamento & purificação , Enterococcus faecalis/metabolismo , Enterococcus faecium/isolamento & purificação , Enterococcus faecium/metabolismo , Humanos , Probióticos/isolamento & purificação , Probióticos/metabolismo
12.
J Food Sci ; 84(12): 3364-3372, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31710097

RESUMO

Low-temperature cooking, such as sous vide, has become a favored method for processing seafood. For this method to be applicable for retail products, combinations with other processing steps are needed to keep the products safe and durable while maintaining high quality. The present experiments were designed to investigate the influence of low-temperature treatment (40, 50, or 60 °C) in combination with various packaging technologies (modified atmosphere [MA] or soluble gas stabilization [SGS]) on both the microbial growth and the physiochemical quality. Salmon loins were either kept natural or inoculated with Listeria innocua prior to drying (16 to 18 hr) in either 100% CO2 (SGS) or atmospheric air (MA packaging). All samples were sous vide treated, repackaged in MA, and stored at 4 °C for 24 days. The results showed shelf life to be significantly improved with the implementation of SGS, by prolonging the lag-phase and slowing the growth rate of both naturally occurring and inoculated bacteria. Variations in packaging technology did not significantly influence any of the tested quality parameters, including drip loss, surface color, and texture. Growing consumer demand for lightly processed seafood products makes Listeria spp. an increasing problem. The present experiment, however, has shown that it is possible to lower processing temperatures to as little as 40 or 50 °C and still obtain inhibition of Listeria, but with improved chemical quality compared to traditional processing.


Assuntos
Culinária/métodos , Produtos Pesqueiros/microbiologia , Listeria/crescimento & desenvolvimento , Salmo salar/microbiologia , Animais , Atmosfera , Contagem de Colônia Microbiana , Produtos Pesqueiros/análise , Microbiologia de Alimentos , Embalagem de Alimentos/métodos , Armazenamento de Alimentos , Temperatura
13.
Bull Exp Biol Med ; 167(6): 818-822, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31656009

RESUMO

We developed a technological accessory bacteriophage-based preparation and a method for phage-mediated bioprocessing for elimination of pathogenic microorganisms from the surface of fresh fish and for prolongation of the shelf-life of chilled hydrobionts. Specimens of rainbow trout (Salmo irideus) served as the objects of the study carried out at a fish-processing plant in the Republic of Karelia. The specimens were decontaminated by a bacteriophage cocktail containing six original virulent phage strains characterized by their pheno- and genotypical properties. A new method of biodecontamination (plunging the rainbow trout for 30 sec into a solution of bacteriophage cocktail (bacteriophage titers ≥108 PFU/ml) delayed bacterial degradation of hydrobionts by 3 days. The use of the new method for decontamination of food half-products - phage-mediated bioprocessing - promoted preservation of the initial ecological purity, nutritive value, and taste of the products and prolonged their shelf-life in comparison with the actual standards.


Assuntos
Bacteriófagos/fisiologia , Produtos Pesqueiros , Conservação de Alimentos/métodos , Armazenamento de Alimentos/métodos , Alimentos Marinhos , Animais , Temperatura Baixa , Contagem de Colônia Microbiana , Descontaminação/métodos , Produtos Pesqueiros/microbiologia , Produtos Pesqueiros/virologia , Manipulação de Alimentos/métodos , Microbiologia de Alimentos , Testes de Sensibilidade Microbiana , Oncorhynchus mykiss/microbiologia , Oncorhynchus mykiss/virologia , Refrigeração , Federação Russa , Alimentos Marinhos/microbiologia , Alimentos Marinhos/virologia
14.
J Food Biochem ; 43(8): e12865, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31368569

RESUMO

This study aims to investigate the technological properties of yeast strains isolated from traditional low-salt fermented Suan yu fish as starter culture. A step-by-step approach was used to determine the technological properties of the isolated yeast strains. The enzymatic activity (catalase, urease, ß-glucosidase, protease, and lipase) under adverse conditions (pH, salt, and temperature) were evaluated. Principal component analysis was used to assess data. Twenty-five strains with desirable technological properties were selected for evaluation of probiotic traits (tolerance at pH 2.5 and 0.3% bile salts, antimicrobial activity, hydrophobic properties, and biofilm production). These isolates were identified by sequencing the D1/D2 region of 26S rDNA. Finally, seven isolates with desirable probiotic traits were analyzed for their ability to survive through gastric transit using a gastrointestinal simulation model. An In vitro test showed that isolates 3, 12, 19, 24, and 43 exhibited high survival levels (60%-70%), similar to those of the indicator strain (Saccharomyces cerevisiae). The results suggest that five isolates (S. cerevisiae strains 3, 12, 19, 24, and 43) showed desirable technological properties and probiotic traits and therefore can be used as functional starter cultures to produce fermented fish products. PRACTICAL APPLICATIONS: Researchers have investigated the activity of LAB as functional and probiotic microorganisms; however, information on the probiotic potential of yeasts remains limited. Yeasts are microorganisms that present and induce biochemical changes in several fermented meat and fish products. In the present study, the technological and probiotic properties of 52 isolates from Suan yu were investigated to identify potential probiotic strains for starter cultures. Our results suggest that five isolated S. cerevisiae strains showed desirable technological properties and probiotic traits and therefore can be used as functional starter cultures to produce fermented fish products, and other fermented foods. Functional yeast isolates are used to effectively improve the quality of fermented fish products for consumer acceptance. This study has focused on the possibility to produce a functional Suan yu using a potential probiotic S. cerevisiae as starter culture to enhance health benefits.


Assuntos
Produtos Pesqueiros , Microbiologia de Alimentos , Probióticos/isolamento & purificação , Leveduras/isolamento & purificação , Animais , Biofilmes , China , Alimentos e Bebidas Fermentados , Produtos Pesqueiros/microbiologia , Concentração de Íons de Hidrogênio , Cloreto de Sódio
15.
J Food Sci ; 84(9): 2592-2602, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31429485

RESUMO

Lactic acid bacteria and Listeria monocytogenes are psychotropic organisms that can grow and compete in food such as lightly preserved fishery products. Predictive microbiology is nowadays one of the leading tools to assess the behavior of bacteria in food and to predict food spoilage. Mathematical models can be used to predict the growth, inactivation or growth probability of bacteria. Currently, the efforts in microbial modeling are oriented towards extrapolation of results beyond experiments in order to predict the growth of interacting microorganisms and develop new food preservation processes. In the present work, a model combining both heterogeneous population and quasi-chemical approaches to describe the different phases of the bacterial growth curve is presented. The model was applied to both monoculture and co-culture cases of lactic acid bacteria, Carnobacterium maltaromaticum H-17, and two Listeria monocytogenes strains in a raw fish extract. It is a highlight that our model includes novel inhibition reactions due to the accumulation of metabolites, and a general equation to take into account the effect of chemical compounds during the lag or physiological adaptation phase of the cells. Our results show that the proposed model can accurately describe the experimental data when the curve shape is a sigmoid, and when it presents a maximum. Besides, the parameters have biological interpretability since the model is mechanistically inspired.


Assuntos
Carnobacterium/metabolismo , Produtos Pesqueiros/microbiologia , Listeria monocytogenes/metabolismo , Modelos Biológicos , Animais , Técnicas de Cocultura , Conservação de Alimentos , Cinética
16.
Environ Sci Pollut Res Int ; 26(26): 27338-27352, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31325090

RESUMO

Vibrio cholerae is a leading waterborne pathogen worldwide. Continuous monitoring of V. cholerae contamination in aquatic products and identification of risk factors are crucial for assuring food safety. In this study, we determined the virulence, antimicrobial susceptibility, heavy metal tolerance, and genetic diversity of 400 V. cholerae isolates recovered from commonly consumed freshwater fish (Aristichthys nobilis, Carassius auratus, Ctenopharyngodon idellus, and Parabramis pekinensis) collected in July and August of 2017 in Shanghai, China. V. cholerae has not been previously detected in the half of these fish species. The results revealed an extremely low occurrence of pathogenic V. cholerae carrying the major virulence genes ctxAB (0.0%), tcpA (0.0%), ace (0.0%), and zot (0.0%). However, high incidence of virulence-associated genes was observed, including the RTX toxin gene cluster (rtxA-D) (83.0-97.0%), hlyA (87.8%), hapA (95.0%), and tlh (76.0%). Meanwhile, high percentages of resistance to antimicrobial agents streptomycin (65.3%), ampicillin (44.5%), and rifampicin (24.0%) were observed. Approximately 30.5% of the isolates displayed multidrug resistant (MDR) phenotypes with 42 resistance profiles, which were significantly different among the four fish species (MARI, P = 0.001). Additionally, tolerance of isolates to heavy metals Hg2+ (49.3%), Zn2+ (30.3%), and Pb2+ (12.0%) was observed. The enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR)-based fingerprinting of the 400 V. cholerae isolates revealed 328 ERIC-genotypes, which demonstrated a large degree of genomic variation among the isolates. Overall, the results of this study support the need for food safety risk assessment of aquatic products.


Assuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana/efeitos dos fármacos , Produtos Pesqueiros/microbiologia , Vibrio cholerae/efeitos dos fármacos , Vibrio cholerae/patogenicidade , Animais , Toxinas Bacterianas/genética , China , Farmacorresistência Bacteriana/genética , Proteínas de Fímbrias/genética , Água Doce , Variação Genética , Genótipo , Metais Pesados/toxicidade , Oligopeptídeos/genética , Vibrio cholerae/genética , Vibrio cholerae/isolamento & purificação , Virulência/genética , Fatores de Virulência/genética
17.
J Food Sci ; 84(7): 1881-1887, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31264719

RESUMO

Nowadays, Listeria monocytogenes continues to be a major health issue. Therefore, improvements in the speed and reliability of its detection are still needed. In the present study, the combination of real-time Recombinase Polymerase Amplification (qRPA) with immunomagnetic separation (IMS) is described. The proposed methodology was tested against a real-time PCR method, and was successfully applied to 50 smoked salmon samples spiked at levels ranging from 2 to 9.3 × 102 cfu/25 g. L. monocytogenes was detected after a 24 hr pre-enrichment, which represents a great improvement over other previously published RPA methods. Additionally, the evaluation of the method reported a Limit of dDetection 50 (LoD50 ) of 6.3 cfu/25 g, along with relative sensitivity, specificity and accuracy values higher than 90%. Finally, the index of kappa concordance was calculated to be 0.93 which is interpreted as "almost complete concordance" between the reference and alternative method. Overall, the described methodology proved to be faster, specific, and as sensitive as other methods based on RPA or real-time PCR. PRACTICAL APPLICATION: The methodology described in this study significantly reduces the detection time of L. monocytogenes, when compared with culture-based methods, and it requires fewer steps than other molecular methods, making it a reliable and more convenient method for routine testing. Finally, the evaluation of the methodology in spiked food samples, confirms its reliability.


Assuntos
Produtos Pesqueiros/microbiologia , Separação Imunomagnética/métodos , Listeria monocytogenes/isolamento & purificação , Técnicas de Amplificação de Ácido Nucleico/métodos , Salmão/microbiologia , Animais , Produtos Pesqueiros/análise , Microbiologia de Alimentos , Listeria monocytogenes/genética , Reação em Cadeia da Polimerase em Tempo Real , Recombinases/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
18.
J Food Prot ; 82(8): 1369-1376, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31322921

RESUMO

We investigated the impact of chitosan and oregano essential oil (EO) individually or in combination on the quality of eel fillets in vacuum packaging (VP) and stored under refrigeration (4°C). Treatments studied were (i) control eel fillets stored in VP (E), (ii) eel fillets treated with 0.3% (v/w) oregano EO and stored in VP (E-OR), (iii) eel fillets treated with 2.0% (w/v) chitosan and stored in VP (E-CH), and (iv) eel fillets treated with 2.0% (w/v) chitosan and 0.3% (v/w) oregano EO and stored in VP (E-CH-OR). Treatments E-CH-OR and E-CH significantly reduced counts of mesophilic bacteria, Pseudomonas, Shewanella, and yeasts and molds during storage. Use of chitosan alone or in combination with oregano EO led to a significant reduction in concentrations of trimethylamine nitrogen and total volatile basic nitrogen in fillets, which led to lower concentrations of thiobarbituric acid reactive substances compared with the control samples. The eel samples in the E-CH and E-CH-OR groups were sensorially acceptable during the entire refrigerated storage period of 18 days. Presence of chitosan in the E-CH and E-CH-OR fillets did not negatively affect the taste of the fillets. E-CH fillets received a higher taste score than did E-CH-OR fillets probably because of the distinct and "spicy" lemon taste of chitosan, which was well received by the sensory panel. Based on overall sensory data (based on mean sensory scores of odor and taste), the shelf life was 6 days for the control fillets, 10 days for the E-OR fillets, and >18 days for the E-CH and E-CH-OR fillets stored in VP at 4°C. Overall, chitosan-treated eel fillets had lower microbial loads and a longer shelf life compared with the controls. Chitosan-treated eel fillets were preferred over oregano-treated fillets. Chitosan alone or in combination with oregano could be used as a preservative treatment and shelf-life extender for other seafoods.


Assuntos
Anguilla , Quitosana , Produtos Pesqueiros , Conservação de Alimentos , Origanum , Óleos Vegetais , Anguilla/microbiologia , Animais , Quitosana/farmacologia , Produtos Pesqueiros/microbiologia , Embalagem de Alimentos/normas , Conservação de Alimentos/métodos , Origanum/química , Óleos Vegetais/farmacologia , Vácuo
19.
Appl Environ Microbiol ; 85(16)2019 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-31175191

RESUMO

Food microstructure significantly affects microbial growth dynamics, but knowledge concerning the exact influencing mechanisms at a microscopic scale is limited. The food microstructural influence on Listeria monocytogenes (green fluorescent protein strain) growth at 10°C in fish-based food model systems was investigated by confocal laser scanning microscopy. The model systems had different microstructures, i.e., liquid, xanthan (high-viscosity liquid), aqueous gel, and emulsion and gelled emulsion systems varying in fat content. Bacteria grew as single cells, small aggregates, and microcolonies of different sizes (based on colony radii [size I, 1.5 to 5.0 µm; size II, 5.0 to 10.0 µm; size III, 10.0 to 15.0 µm; and size IV, ≥15 µm]). In the liquid, small aggregates and size I microcolonies were predominantly present, while size II and III microcolonies were predominant in the xanthan and aqueous gel. Cells in the emulsions and gelled emulsions grew in the aqueous phase and on the fat-water interface. A microbial adhesion to solvent assay demonstrated limited bacterial nonpolar solvent affinities, implying that this behavior was probably not caused by cell surface hydrophobicity. In systems containing 1 and 5% fat, the largest cell volume was mainly represented by size I and II microcolonies, while at 10 and 20% fat a few size IV microcolonies comprised nearly the total cell volume. Microscopic results (concerning, e.g., growth morphology, microcolony size, intercolony distances, and the preferred phase for growth) were related to previously obtained macroscopic growth dynamics in the model systems for an L. monocytogenes strain cocktail, leading to more substantiated explanations for the influence of food microstructural aspects on lag phase duration and growth rate.IMPORTANCE Listeria monocytogenes is one of the most hazardous foodborne pathogens due to the high fatality rate of the disease (i.e., listeriosis). In this study, the growth behavior of L. monocytogenes was investigated at a microscopic scale in food model systems that mimic processed fish products (e.g., fish paté and fish soup), and the results were related to macroscopic growth parameters. Many studies have previously focused on the food microstructural influence on microbial growth. The novelty of this work lies in (i) the microscopic investigation of products with a complex composition and/or structure using confocal laser scanning microscopy and (ii) the direct link to the macroscopic level. Growth behavior (i.e., concerning bacterial growth morphology and preferred phase for growth) was more complex than assumed in common macroscopic studies. Consequently, the effectiveness of industrial antimicrobial food preservation technologies (e.g., thermal processing) might be overestimated for certain products, which may have critical food safety implications.


Assuntos
Gorduras/análise , Produtos Pesqueiros/análise , Produtos Pesqueiros/microbiologia , Listeria monocytogenes/crescimento & desenvolvimento , Animais , Contagem de Colônia Microbiana , Peixes , Microbiologia de Alimentos , Conservação de Alimentos , Cinética , Listeria monocytogenes/química , Modelos Biológicos , Viscosidade
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