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1.
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
2.
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
3.
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
4.
Int J Food Microbiol ; 305: 108244, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31202150

RESUMO

This study examined the prevalence and phenotypic and genotypic antibiotic resistance patterns of Staphylococcus aureus in sushi from 20 Danish outlets. Microbial quality of sushi products and food inspector ranking of outlets were assessed and results for thirteen of the outlets were compared with findings from a previous study in 2012. Inspector rankings were similar in the two studies. The mesophilic aerobic counts were slightly lower (p = 0.0296) in 2017 than in 2012 with average values of the 13 shops of 5.2 log CFU/g and 5.7 log CFU/g, respectively. In both studies E. coli was only found in the products from outlets that did not have consistently superior rankings. On the other hand prevalence and average counts of Staphylococcus spp. were slightly higher in 2017 (p = 0.0286) but no methicillin-resistant S. aureus (MRSA) were observed in the present study. Methicillin-sensitive S. aureus (MSSA) were, however, isolated from 18.7% of sushi products with an average count below 2 log CFU/g. Based on spa and multilocus sequence typing (MLST), isolates belonged to clonal complex CC7 (t2016), CC20 (t7836), CC45 (t065, t127, t362), CC88 (t1998) and CC398 (t164, t331, t1451). The Panton-Valentine leukocidin (PVL)-encoding gene lukF was detected only in isolates of the t065 spa-type whereas the scn gene from the ΦSa3 prophage was detected in 76.5% of the isolates, supporting that the majority of isolates were of likely human origin. Thirty-six isolates (70.6%) were resistant to at least one of the antibiotic compounds tested. Antibiotic resistance genes that confer resistance to ß-lactams (blaZ) and macrolides (ermC) were detected in 33.3% and 9.8% of isolates, respectively. The tet(K) gene that encode tetracycline resistance was only found in a t7836 strain. Overall, this study indicates that S. aureus in sushi products in Denmark do not represent a major food safety hazard due to, firstly, the low temperature and limited time of storage of product may prevent significant growth and production of toxic levels of enterotoxin of this species. Secondly, the S. aureus isolates obtained did not include MRSA variants and none of them encoded PVL that constitute one of the virulence factors in pathogenesis. Several MSSA isolates contained however genes encoding antibiotic resistance, which emphasize the potential role of foods as vehicles for transmission of such variants.


Assuntos
Farmacorresistência Bacteriana , Produtos Pesqueiros/microbiologia , Inspeção de Alimentos/normas , Animais , Antibacterianos/farmacologia , Dinamarca , Escherichia coli/classificação , Escherichia coli/genética , Escherichia coli/isolamento & purificação , Peixes , Humanos , Meticilina/farmacologia , Staphylococcus aureus Resistente à Meticilina/classificação , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Staphylococcus aureus Resistente à Meticilina/genética , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Testes de Sensibilidade Microbiana , Tipagem de Sequências Multilocus , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/classificação , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/genética , Staphylococcus aureus/isolamento & purificação , Fatores de Virulência/genética , beta-Lactamas/farmacologia
5.
J Food Sci ; 84(7): 1871-1880, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31218691

RESUMO

Impact of dielectric barrier discharge high-voltage cold atmospheric plasma (DBD-HVCAP) generated with the mixture of oxygen and argon (10:90) for various treatment times (2.5 to 10 min) on the qualities of Asian sea bass slices during 4 °C storage was investigated. Microbial load of slices treated with DBD-HVCAP were lower than the control. The efficacy of bacteria reduction by DBD-HVCAP was dependent on the treatment times (P < 0.05). Total viable bacteria count (TVBC) was more than 6.0 Log CFU/g at day 6 for the control kept in air. Slices treated with DBD-HVCAP for all treatment times used had TVBC lower than the limit at day 12. Total volatile nitrogen base content (TVNB) as well as trimethylamine (TMA) content in slices treated with DBD-HVCAP were lower than that of the control throughout the storage. TVNB as well as TMA contents were lower in HVCAP treated slices in a treatment time-dependent manner. Nevertheless, lipid oxidation in samples treated with DBD-HVCAP was higher than that of the control. Polyunsaturated fatty acids were decreased in slices treated with DBD-HVCAP for more than 5 min after 12 days of storage. Therefore DBD-HVCAP treatment for 5 min was demonstrated to be potential means for increasing the shelf-life of Asian sea bass slices with minimal negative effect on chemical and sensory properties, in which they could be stored longer than 12 days at 4 °C. PRACTICAL APPLICATION: Microbial inactivation capacity of dielectric barrier discharge high-voltage cold atmospheric plasma (DBD-HVCAP) has been documented with limited information on its application in extending the shelf-life of foods. DBD-HVCAP was demonstrated as an innovative technology for extending the shelf-life of Asian sea bass slices, which could be implemented in seafood industries for assuring safety and extending shelf-life of products. The shelf-life of the slices treated with DBD-HVCAP was extended to 12 days of storage at 4 °C as compared to the 6 days of the untreated counterpart.


Assuntos
Bass/microbiologia , Produtos Pesqueiros/análise , Conservação de Alimentos/métodos , Gases em Plasma/farmacologia , Animais , Argônio/química , Argônio/farmacologia , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Produtos Pesqueiros/microbiologia , Armazenamento de Alimentos , Oxigênio/química
6.
Food Microbiol ; 82: 455-464, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31027805

RESUMO

Listeria monocytogenes causes the foodborne illness listeriosis, which exhibits high fatality among people in risk groups. The incidence of listeriosis has increased in Europe, which raises concerns about L. monocytogenes occurrence in foodstuffs. Ready-to-eat seafood products are considered particularly risky vehicles. Poor hygiene at processing facilities predisposes them to L. monocytogenes contamination, which can be controlled by stringent self-checking system measures. We examined the association of fish-processing plant operational and hygiene practices with the occurrence of L. monocytogenes in vacuum-packaged gravad (cold-salted) and cold-smoked salmon and rainbow trout products. Product sampling of 21 fish-processing plants was carried out, and operational procedures relating to L. monocytogenes control were surveyed using an in-depth risk assessment questionnaire. L. monocytogenes occurred only in sliced and mainly in gravad products of seven fish-processing plants. Shortages in preventive measures were discovered predominantly among the L. monocytogenes positive fish-processing plants. Using generalized linear modeling, we identified the following features associated with L. monocytogenes product contamination: the number of processing machines, deficiencies in the processing environment and machinery sanitation, and staff movement from areas of low toward high hygiene. Furthermore, performing frequent periodic thorough sanitation alongside everyday sanitation practices associated with a decreased risk of product contamination.


Assuntos
Produtos Pesqueiros/microbiologia , Manipulação de Alimentos/métodos , Indústria de Processamento de Alimentos/estatística & dados numéricos , Higiene , Listeria monocytogenes/isolamento & purificação , Saneamento/estatística & dados numéricos , Alimentos Marinhos/microbiologia , Animais , Microbiologia Ambiental , Monitoramento Ambiental , Contaminação de Equipamentos , Contaminação de Alimentos/análise , Contaminação de Alimentos/prevenção & controle , Manipulação de Alimentos/instrumentação , Microbiologia de Alimentos , Indústria de Processamento de Alimentos/normas , Humanos , Higiene/normas , Oncorhynchus mykiss , Salmão , Saneamento/normas , Inquéritos e Questionários , Vácuo
7.
Food Microbiol ; 82: 465-473, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31027807

RESUMO

Biogenic amines (BAs) are frequently present in traditionally fermented salted foods. In this study, a Tetragenococcus halophilus strain (MJ4) with no BA-producing ability was isolated from a fish (anchovy) sauce. Strain MJ4 did not produce BAs from supplied precursors and no BA-producing genes were identified in its genome. Bacterial community analysis showed that in non-inoculated saeu-jeot (shrimp sauce) fermentation, Tetragenococcus predominated after 82 days, while in strain MJ4-inoculated saeu-jeot, Tetragenococcus predominated during the entire fermentation. Strain MJ4 repressed the growth of T. muriaticus, a known BA producer, during fermentation, but metabolite analysis demonstrated that metabolite profiles, including amino acids, were similar regardless of MJ4 inoculation. The metabolite analysis also showed that strain MJ4 clearly repressed the formation of cadaverine during fermentation. This study suggests that the use of strain MJ4 as a starter culture in salted fish fermentation may be a good strategy for the reduction of BA formation.


Assuntos
Cadaverina/metabolismo , Enterococcaceae/fisiologia , Microbiologia de Alimentos , Alimentos Marinhos/microbiologia , Aminoácidos/análise , Aminoácidos/metabolismo , Animais , Cadaverina/análise , Crustáceos , Enterococcaceae/crescimento & desenvolvimento , Enterococcaceae/isolamento & purificação , Enterococcaceae/metabolismo , Fermentação , Produtos Pesqueiros/microbiologia , Peixes , Microbiota , Frutos do Mar , Cloreto de Sódio
8.
Arq. bras. med. vet. zootec. (Online) ; 71(2): 687-695, mar.-abr. 2019. tab, ilus
Artigo em Português | LILACS, VETINDEX | ID: biblio-1011277

RESUMO

O objetivo do presente trabalho foi desenvolver a carne de bijupirá defumada, assim como avaliar o rendimento, a qualidade bacteriológica, a composição centesimal e a aceitabilidade do produto. Análises microbiológicas de pesquisa de Salmonella sp. e contagens de Staphylococcus aureus, coliformes totais e Escherichia coli foram realizadas. Foi determinada a composição centesimal e realizado o teste de aceitação do produto. O rendimento médio da carne após a salga foi de 83,41%, com base no peso do charuto. A análise microbiológica da carne defumada apresentou-se positiva em apenas uma amostra para Staphylococcus aureus e negativa para as demais bactérias. O produto possui boa qualidade nutricional e alcançou 97% de aceitação para o aspecto global, atingindo média de 6,26 (± 0,99). A carne de bijupirá defumada obteve condições higiênico-sanitárias satisfatórias, boa qualidade nutricional, além de alto índice de aceitação sensorial, destacando-se os atributos textura e sabor. Evidenciou-se, assim, que esse tipo de processo pode ser realizado em escala artesanal ou industrial.(AU)


The objective of the study was to develop the smoked cobia meat and to evaluate the yield, the bacteriological quality, the centesimal composition, and the acceptability of the product. Microbiological analysis of Salmonella sp. and Staphylococcus aureus, total coliforms and Escherichia coli counts were performed. The centesimal composition was determined and the acceptance test was performed. The average yield of the product after salting was 83.41% based on the fish roll weight. The microbiological analysis of the smoked meat showed positive in only one sample for Staphylococcus aureus and negative for the other bacteria. The product has a good nutritional quality and was accepted obtaining 97% for the overall aspect, average of 6.26 (± 0.99). The smoked cobia meat obtained satisfactory hygienic-sanitary conditions, good nutritional quality, besides a high index of sensorial acceptance emphasizing the texture and flavor attributes. Smoked process can be easily carried out on an artisanal or industrial scale.(AU)


Assuntos
Animais , Salmonella/isolamento & purificação , Staphylococcus aureus/isolamento & purificação , Colimetria , Produtos Pesqueiros/microbiologia , Peixes , Conservação de Alimentos
9.
J Sci Food Agric ; 99(10): 4731-4738, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-30924936

RESUMO

BACKGROUND: Sakacin-A due to its specific antimicrobial activity may represent a good candidate to develop active packaging solutions for food items supporting Listeria growth. In the present study a protein extract containing the bacteriocin sakacin-A, produced by Lactobacillus sakei Lb 706 in a low-cost culture medium containing deproteinized cheese whey, was adsorbed onto cellulose nanofibers (CNFs) to obtain an active material to be used as a mat (or a separator) in direct contact with foods. RESULTS: The applied fermentation conditions allowed 4.51 g L-1 of freeze-dried protein extract to be obtained, characterized by an antimicrobial activity of near 16 700 AU g-1 , that was used for the preparation of the active material by casting. The active material was then characterized by infrared spectra and thermogravimetric analyses. Antimicrobial trials were carried out in vitro using Listeria innocua as indicator strain; results were also confirmed in vivo, employing smoked salmon fillets intentionally inoculated with Listeria innocua: its final population was reduced to about 2.5-3 Log cycles after 28 days of storage at 6 °C in presence of sakacin-A, compared with negative control mats produced without the bacteriocin extract. CONCLUSION: This study demonstrates the possibility of producing an antimicrobial active material containing sakacin-A absorbed onto CNFs to decrease Listeria population in smoked salmon, a ready-to eat-food product. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.


Assuntos
Antibacterianos/química , Bacteriocinas/química , Produtos Pesqueiros/análise , Conservação de Alimentos/métodos , Conservantes de Alimentos/química , Nanofibras/química , Animais , Antibacterianos/farmacologia , Bacteriocinas/farmacologia , Celulose/química , Fast Foods/análise , Fast Foods/microbiologia , Produtos Pesqueiros/microbiologia , Conservação de Alimentos/instrumentação , Conservantes de Alimentos/farmacologia , Listeria/crescimento & desenvolvimento , Salmão/microbiologia
10.
Molecules ; 24(4)2019 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-30781435

RESUMO

This study investigated the effects of α-tocopherol (α-TOH) on the physicochemical properties of sturgeon surimi during 16-week storage at -18 °C. An aliquot of 0.1% (w/w) of α-TOH was added into the surimi and subjected to frozen storage, and 8% of a conventional cryoprotectant (4% sorbitol and 4% sucrose, w/w) was used as a positive control. Based on total viable count, pH and whiteness, α-TOH exhibited a better protection for frozen sturgeon surimi than cryoprotectant during frozen storage. According to soluble protein content, carbonyl content, total sulfhydryl content, and surface hydrophobicity, α-TOH and cryoprotectant showed the same effects on retarding changes of proteins. The results of breaking force, deformation, gel strength, water-holding capacity and microstructure of sturgeon surimi indicated that the gel properties of frozen sturgeon surimi were retained by α-TOH. Our results suggest that α-TOH is an attractive candidate to maintain the quality of sturgeon surimi during frozen storage.


Assuntos
Crioprotetores/farmacologia , Peixes/metabolismo , Congelamento , alfa-Tocoferol/farmacologia , Animais , Produtos Pesqueiros/análise , Produtos Pesqueiros/microbiologia , Conservação de Alimentos/métodos , Armazenamento de Alimentos/métodos , Compostos de Sulfidrila/metabolismo
11.
Microb Genom ; 5(2)2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30775964

RESUMO

We present the LiSEQ (Listeria SEQuencing) project, funded by the European Food Safety Agency (EFSA) to compare Listeria monocytogenes isolates collected in the European Union from ready-to-eat foods, compartments along the food chain (e.g. food-producing animals, food-processing environments) and humans. In this article, we report the molecular characterization of a selection of this data set employing whole-genome sequencing analysis. We present an overview of the strain diversity observed in different sampled sources, and characterize the isolates based on their virulence and resistance profile. We integrate into our analysis the global L. monocytogenes genome collection described by Moura and colleagues in 2016 to assess the representativeness of the LiSEQ collection in the context of known L. monocytogenes strain diversity.


Assuntos
Laticínios/microbiologia , Produtos Pesqueiros/microbiologia , Listeria monocytogenes/classificação , Listeriose/microbiologia , Produtos da Carne/microbiologia , Animais , Estudos Transversais , Farmacorresistência Bacteriana/genética , Europa (Continente) , Manipulação de Alimentos , Microbiologia de Alimentos , Variação Genética , Humanos , Listeria monocytogenes/genética , Listeria monocytogenes/isolamento & purificação , Virulência/genética , Sequenciamento Completo do Genoma
12.
J Microbiol Biotechnol ; 29(2): 209-221, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-30609884

RESUMO

Gamma-aminobutyric acid (GABA) is a neurotransmitter that exerts several physiological functions and positive effects on human health. The aim of this study was to isolate and characterize the strains that had GABA-producing abilities from various fermented fish products. A total of 91 acid-producing strains were isolated from 41 samples of fermented fish products, and 27 strains showing GABA-producing abilities were identified by the 16S rDNA sequences. Among the strains, 31% strains tolerated at high-salt environment of 10-20% throughout the fermentation of fish sauces. The 27 isolates that produced GABA at various concentrations did so in the range of 5 to 454 mM. These GABA-producing isolates were identified as lactic acid bacteria of 14 strains, which included twelve Lactococcus lactis, one Enterococcus faecium, and one Lactococcus pentosus; eight Bacillus cereus group, which included seven B. thuringiensis and one B. cereus; and five Staphylococcus spp. Interestingly, with Vietnamese fish sauces, we mostly identified species of B. thuringiensis and Staphylococcus spp., while with Korean fermented fish products, the majority of the strains identified belonged to L. lactis. Among the strains, B. thuringiensis LH2134 produced the highest levels of GABA at 366 mM among the strains identified from Vietnamese fish sauces, whereas L. lactis LA43, a new strain isolated from Korean jeotgal (salted shrimp paste), produced the highest amount of GABA at 454 mM and the glutamate concentration in the medium was essential for GABA accumulation. Therefore, such the isolates might serve as good starters for development of more GABA-reinforced foods among fermented fish products.


Assuntos
Bactérias/isolamento & purificação , Bactérias/metabolismo , Produtos Pesqueiros/microbiologia , Microbiologia de Alimentos , Ácido gama-Aminobutírico/metabolismo , Bactérias/classificação , Bactérias/genética , Meios de Cultura/química , Ácido Glutâmico , Filogenia , RNA Ribossômico 16S/genética , Alimentos Marinhos/microbiologia , Cloreto de Sódio/metabolismo
13.
Int J Food Microbiol ; 292: 137-143, 2019 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-30599453

RESUMO

The aims of this study were to isolate halophilic lactic acid bacteria possessing aspartate decarboxylase and elucidate the property of the isolates as starter cultures for fish sauce fermentation. Seventy-four strains were isolated from fermented fish foods on aspartate indicator broth containing bromocresol purple, and all isolates were identified as Tetragenococcus halophilus and confirmed to possess the aspartate decarboxylase gene (aspD) by PCR amplification. The isolates were classified into 14 groups based on their aspD-encoding plasmid construction. Strains selected from each group and a control strain incapable of aspartate decarboxylation were inoculated into fish sauce mash as starter cultures. Isolated strains possessing aspD converted aspartate into alanine almost completely in the fish sauce mash. In addition, the strains prevented the accumulation of biogenic amines, as did the control strain, whereas various amines were accumulated in fish sauce mash without starter cultures. Sensory evaluation tests indicated that converting the sour amino acid aspartate into the sweet amino acid alanine made the fish sauce taste milder. In conclusion, the use of T. halophilus possessing aspartate decarboxylase as a fish sauce fermentation starter causes the conversion of aspartate to alanine, accompanied by taste alteration, and prevents biogenic amine accumulation in fish sauce products.


Assuntos
Carboxiliases/metabolismo , Fermentação , Produtos Pesqueiros/microbiologia , Microbiologia de Alimentos , Lactobacillales/enzimologia , Adulto , Alanina/metabolismo , Aminoácidos/metabolismo , Ácido Aspártico/metabolismo , Aminas Biogênicas/análise , Carboxiliases/genética , Enterococcaceae/isolamento & purificação , Humanos , Plasmídeos/genética , Paladar , Adulto Jovem
14.
J Food Sci ; 84(1): 127-132, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30569471

RESUMO

This study aimed to evaluate the effect of ε-polylysine hydrochloride (ε-PLH) on the growth and thermal inactivation kinetics of Listeria monocytogenes in fish balls. Samples, supplemented with ε-PLH (0, 150, or 300 ppm, w/w), were inoculated with a three-strain cocktail of L. monocytogenes and incubated at constant temperatures of 3.4, 8, 12, or 16 °C for growth studies, or heated at 60, 62.5, 65, or 67.5 °C for thermal inactivation tests. The growth curves were fitted to the Huang primary model, and the Huang and Ratkowsky square-root models (SRM) were used as the secondary models to evaluate the effect of temperature on bacterial growth. The survival during heating was analyzed with a log-linear model. The results showed that, while the lag time of L. monocytogenes was affected by both ε-PLH concentration and temperature, the specific growth rate was unaffected by ε-PLH. Under the same temperature, a 10-time in increase of the lag time would be expected for every 565 ppm in the increase of ε-PLH concentration. Using the Ratkowsky SRM, the estimated nominal minimum growth temperature was -2.04 °C, while the minimum growth temperature was 0.29 °C when estimated with the Huang SRM. Validation at 10 °C showed that the Huang primary model, in combination with either the Huang or Ratkowsky SRM, could accurately predict the growth of L. monocytogenes. On the other hand, the thermal resistance of the pathogen was significantly reduced by increase in temperature or ε-PLH. The thermal z value of L. monocytogenes was 5.78 °C, and the ε-PLH z value was 1642 ppm. The results of this study showed that the combined application of ε-PLH and temperature can be used to control L. monocytogenes in fish balls and to improve food safety and reduce risks to public health.


Assuntos
Produtos Pesqueiros/microbiologia , Listeria monocytogenes/efeitos dos fármacos , Polilisina/farmacologia , Animais , Contagem de Colônia Microbiana , Peixes/microbiologia , Contaminação de Alimentos/prevenção & controle , Microbiologia de Alimentos , Listeria monocytogenes/crescimento & desenvolvimento , Modelos Teóricos , Sais , Temperatura Ambiente
15.
J Sci Food Agric ; 99(1): 199-209, 2019 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-29851067

RESUMO

BACKGROUND: The quality of marinated ready-to-eat (RTE) swordfish fillets, with or without inoculation with the probiotic strain Lactobacillus paracasei IMPC 2.1, was assessed over 3 months of refrigerated storage at 4 °C. RTE probiotic and control fish fillets were sampled after 7, 14, 30, 60, and 90 days of storage. Microbiological tests were performed, and fatty acid (FA) profiles and malondialdehyde content were examined. Microbiological counts, including total viable count, lactic acid bacteria (LAB), yeasts, moulds, Enterobacteriaceae, and Pseudomonadaceae were determined. RESULTS: Inoculation successfully ensured the growth of the probiotic strain and prevented the growth of other LAB. The two RTE products showed significant differences in lipid profile and lipid oxidation during storage. In particular, inoculation with L. paracasei IMPC 2.1 increased the amount of polyunsaturated FAs and limited the amount of monounsaturated FAs and oleic acid, as well as lipid oxidation. It thus represents an interesting strategy for preserving the chemical quality of fish fillets and an alternative means of delivering probiotics. CONCLUSION: Probiotic inoculation with Lactobacillus paracasei seemed to delay lipid oxidation of the fish flesh and increase the retention of polyunsaturated FAs, suggesting a potential application for this strain in the seafood industry. © 2018 Society of Chemical Industry.


Assuntos
Fast Foods/microbiologia , Produtos Pesqueiros/análise , Produtos Pesqueiros/microbiologia , Peixes/microbiologia , Conservação de Alimentos/métodos , Lactobacillus paracasei/fisiologia , Animais , Antibiose , Enterobacteriaceae/crescimento & desenvolvimento , Enterobacteriaceae/fisiologia , Fast Foods/análise , Armazenamento de Alimentos , Fungos/crescimento & desenvolvimento , Fungos/fisiologia , Lactobacillus paracasei/crescimento & desenvolvimento
16.
J Sci Food Agric ; 99(6): 2922-2930, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30471133

RESUMO

BACKGROUND: Refrigeration is commonly used in the processing and storage of surimi products. However, refrigerated surimi products are susceptible to microbial contamination, which leads to deterioration of the products and shortens their shelf life. The aims of the present study were therefore to evaluate the effects of ϵ-polylysine (ϵ-PL) on spoilage bacteria in surimi products, and to investigate the antibacterial mechanism of Bacillus cereus, which is the dominant spoilage bacterium. RESULTS: ϵ-Polylysine with a high degree of polymerization (20-30K) proved able to decrease the total number of colonies in surimi products and showed an obvious antibacterial effect against B. cereus. After ϵ-PL treatments, the distinct broken areas on the bacterial surfaces and the aggregations of cells were observed by scanning electron microscope (SEM). The intracellular materials, such as small molecules, soluble proteins, and deoxyribonucleic acids in the cells were analyzed, which revealed the destructive effects of ϵ-PL on bacterial cells. Experiments with propidium iodide (PI) infiltration experiments verified that the permeability of cell membranes was enhanced by ϵ-PL treatment. CONCLUSION: These results indicated that ϵ-PL could destroy the cell membranes and change the permeability of B. cereus, and subsequently the cell contents leaked out to achieve antibacterial effects. © 2018 Society of Chemical Industry.


Assuntos
Antibacterianos/farmacologia , Bacillus cereus/crescimento & desenvolvimento , Produtos Pesqueiros/microbiologia , Conservação de Alimentos/métodos , Conservantes de Alimentos/farmacologia , Polilisina/farmacologia , Antibacterianos/análise , Bacillus cereus/efeitos dos fármacos , Produtos Pesqueiros/análise , Conservação de Alimentos/instrumentação , Conservantes de Alimentos/análise , Polilisina/análise , Refrigeração
17.
J Sci Food Agric ; 99(5): 2428-2437, 2019 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-30362163

RESUMO

BACKGROUND: Microbial spoilage of fishery products accounts for significant financial losses, yearly on a global scale. Psychrotrophic spoilage bacteria often secrete extracellular enzymes to break down surrounding fish tissue, rendering the product unsuitable for human consumption. For a better understanding of bacterial spoilage due to enzymatic digestion of fish products, proteases in Serratia grimesii isolated from North American catfish fillets (Ictalurus punctatus) were investigated. RESULTS: Mass spectrometric evidence demonstrated that S. grimesii secretes two distinct extracellular proteases and one lipase. Protease secretion displayed broad thermostability in the 30-90 °C range. The major protease-secretion (O-1) was most active under alkaline conditions and utilized manganese as a co-factor. Organic solvents significantly disrupted the efficacy of S. grimesii extracellular enzymes and, in a series of bactericidal detergents, protease activity was highest when treated with Triton X-100. Ethylenediaminetetraacetic acid (EDTA) and phenylmethylsulfonyl fluoride (PMSF) significantly inhibited the enzyme activity, while protease was moderately stable under freeze-thaw and refrigerated storage. CONCLUSION: The influence of fish spoilage-related enzymes, depending on various factors, is discussed in this paper. This study will provide new insight into enzymatic spoilage and its control, which can be exploited to enhance food safety and the shelf-life of fishery products worldwide. © 2018 Society of Chemical Industry.


Assuntos
Proteínas de Bactérias/química , Ictaluridae/microbiologia , Peptídeo Hidrolases/química , Serratia/enzimologia , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Proteínas de Bactérias/metabolismo , Estabilidade Enzimática , Produtos Pesqueiros/análise , Produtos Pesqueiros/microbiologia , Temperatura Alta , Peptídeo Hidrolases/genética , Peptídeo Hidrolases/isolamento & purificação , Peptídeo Hidrolases/metabolismo , Serratia/química , Serratia/genética , Serratia/isolamento & purificação
18.
J Sci Food Agric ; 99(5): 2356-2364, 2019 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-30367501

RESUMO

BACKGROUND: This study investigated the effect of chitosan coating enriched with extracted egg yolk antibodies on microbial and sensory quality of rainbow trout fillet during refrigeration (4 ± 1 °C). Firstly, bacterial antigen suspensions (total psychrophilic bacteria, Pseudomonas fluorescens and Shewanella putrefaciens) were injected into the breast muscles of chickens. Eggs of immunized chickens were then collected to isolate immunoglobulin from egg yolks (IgY). Fresh fish fillets were coated by chitosan solution containing different types of IgY separately, at two concentrations (60 and 90 mg mL-1 ), refrigerated for 16 days and analysed for total viable count, psychrotrophic, Pseudomonas spp., P. fluorescens and S. putrefaciens count as well as sensorial properties. RESULTS: The tested microbial values increased in all samples during the storage period; however, CH + IgY treated samples could significantly retard microbial growth compared to control. The shelf life of CH + IgY-P samples was extended for about 4 days, while it was extended for about 8 days in CH + IgY-S and CH + IgY-T samples, when they were compared to control (p < 0.05). Higher scores for sensory attributes were also observed in CH + IgY treated samples, especially in CH + IgY-S samples until the end of storage period. CONCLUSIONS: Accordingly, use of chitosan coating containing IgY increases the microbial and sensory quality of fish flesh at 4 °C. Therefore, given the consumer interest in natural additives, chitosan coating containing IgY can be a promising candidate. © 2018 Society of Chemical Industry.


Assuntos
Quitosana/química , Gema de Ovo/imunologia , Produtos Pesqueiros/análise , Conservação de Alimentos/métodos , Imunoglobulinas/farmacologia , Animais , Galinhas , Gema de Ovo/química , Produtos Pesqueiros/microbiologia , Humanos , Imunoglobulinas/química , Imunoglobulinas/imunologia , Imunoglobulinas/isolamento & purificação , Oncorhynchus mykiss/microbiologia , Pseudomonas fluorescens/efeitos dos fármacos , Pseudomonas fluorescens/crescimento & desenvolvimento , Refrigeração , Shewanella putrefaciens/efeitos dos fármacos , Shewanella putrefaciens/crescimento & desenvolvimento , Paladar
19.
Food Sci Technol Int ; 25(2): 91-100, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30149729

RESUMO

In this work, the effect of the addition of olive leaf extracts on the quality of vacuum-packed salmon burgers stored at 4 ℃ during 16 days has been studied. Olive leaf extract and its hydrolysate were initially characterized and then incorporated to salmon burgers. A shelf life study was conducted in three different batches (control, olive leaf extract, and hydrolyzed olive leaf extract burgers). Among the chemical indices determined, total volatile base nitrogen values were lower in hydrolyzed olive leaf extract and olive leaf extract burgers than in control samples. Lipid oxidation was lower in salmon burger with olive leaf extract. Salmon mince treated with hydrolyzed olive leaf extract showed lower microbial counts during the whole study, which extended the shelf life of the fish product. Therefore, the potential of olive leaf extracts to preserve salmon burgers during cold storage has been demonstrated.


Assuntos
Produtos Pesqueiros/microbiologia , Manipulação de Alimentos/métodos , Conservação de Alimentos/métodos , Armazenamento de Alimentos/métodos , Olea , Extratos Vegetais , Salmão , Animais , Temperatura Baixa , Microbiologia de Alimentos , Embalagem de Alimentos/métodos , Conservantes de Alimentos , Humanos , Peroxidação de Lipídeos , Folhas de Planta , Refrigeração
20.
BMC Microbiol ; 18(1): 216, 2018 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-30563460

RESUMO

BACKGROUND: Lactobacillus plantarum, a versatile lactic acid-fermenting bacterium, isolated from the traditional pickles in Ningbo of China, was chosen for grass carp fermentation, which could also improve the flavor of grass carp. We here explored the central metabolic pathways of L. plantarum by using metabolomic approach, and further proved the potential for metabolomics combined with proteomics approaches for the basic research on the changes of metabolites and the corresponding fermentation mechanism of L. plantarum fermentation. RESULTS: This study provides a cellular material footprinting of more than 77 metabolites and 27 proteins in L. plantarum during the grass carp fermentation. Compared to control group, cells displayed higher levels of proteins associated with glycolysis and nucleotide synthesis, whereas increased levels of serine, ornithine, aspartic acid, 2-piperidinecarboxylic acid, and fumarate, along with decreased levels of alanine, glycine, threonine, tryptophan, and lysine. CONCLUSIONS: Our results may provide a deeper understanding of L. plantarum fermentation mechanism based on metabolomics and proteomic analysis and facilitate future investigations into the characterization of L. plantarum during the grass carp fermentation.


Assuntos
Carpas/microbiologia , Lactobacillus plantarum/metabolismo , Animais , China , Fermentação , Produtos Pesqueiros/microbiologia , Glicólise , Lactobacillus plantarum/genética , Lactobacillus plantarum/isolamento & purificação , Metabolômica , Proteômica
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