Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 7 de 7
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Food Chem ; 308: 125590, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-31644970

RESUMO

A novel fluorescent nanoprobe was for the first time developed for the efficient detection of ferrocyanide ions ([Fe(CN)6]4-) based on nitrogen (N), sulfur (S) and chlorine (Cl) co-doped carbon nanoparticles (N,S,Cl-CNPs). The N,S,Cl-CNPs were fabricated through a simple and ultrafast acid-base neutralization method. The sensing mechanism was based on the quenching effect of [Fe(CN)6]4- on the fluorescence emission of N,S,Cl-CNPs via dynamic interaction. The N,S,Cl-CNPs were found to show high selectivity and sensitivity towards [Fe(CN)6]4- detection with two good linear relationships were achieved in the concentration ranges of 0.01-1.0 µg/mL and 1.0-50.0 µg/mL, respectively, and the detection limits are as low as 3.3 and 21.8 ng/mL, respectively. The proposed fluorescence method was successfully applied for [Fe(CN)6]4- analyses in food samples with high accuracy. The results of this study indicate the great application prospects of N,S,Cl-CNPs for [Fe(CN)6]4- detection in complex food matrix.


Assuntos
Carbono/química , Ferrocianetos/análise , Nanopartículas , Cloro/química , Ferrocianetos/química , Fluorescência , Análise de Alimentos , Limite de Detecção , Nitrogênio/química , Espectrometria de Fluorescência/métodos , Enxofre/química
2.
Food Microbiol ; 86: 103330, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703878

RESUMO

Pickle is a type of mildly lactic acid fermented vegetable and is a traditional dish favored in China, Japan, and Korea. Corruption of spoilage bacteria and accumulation of nitrite during vegetable fermentation are common problems that affect the pickle industry and consumer health. In this work, cucumber juice was used as a vegetable model to study the dominant mesophilic aerobic bacteria (MAB) producing nitrite during pickle fermentation. Virulent phages infecting the dominant MABs combined with Lactobacillus plantarum M6 were used to control these bacteria. Enterobacter cloacae and Pseudomonas fluorescens are the dominant MABs in the fermentation of cucumber juice containing 4% or 8% NaCl, with isolation percentages reaching 30.6% and 23.1%, respectively. Virulent phages PspYZU5415 and EcpYZU01 were isolated using P. fluorescens J5415 and E. cloacae J01 as the host bacteria, respectively. These two phages show a broad host range and strong lytic activity, and their genomes contain no toxins and antibiotic resistance genes. PspYZU5415 and EcpYZU01 were combined into a cocktail (designated as Phage MIX) that effectively inhibits the growth of E. cloacae and P. fluorescens in cucumber juice with different salt concentrations. PhageMIX combined with L. plantarum M6 decreased the counts of P. mendocina and E. cloacae to undetectable levels at 48 h during the fermentation of cucumber juice artificially contaminated with P. mendocina and E. cloacae. In addition, nitrite content increased to 11.3 mg/L at 20 h and then degraded completely at 36 h. By contrast, P. mendocina and E. cloacae remained in the groups without PhageMIX during fermentation (0-48 h). Nitrite content rapidly increased to 65.7 mg/L at 12 h and then decreased to 21.6 mg/L at 48 h in the control group. This study suggests that PhageMIX combined with lactic acid bacterial strains can be used as an ecological starter for controlling the dominant MABs P. mendocina and E. cloacae and for reducing nitrate production during the early stage of pickle fermentation.


Assuntos
Bacteriófagos/fisiologia , Bacteriófagos/patogenicidade , Cucumis sativus/microbiologia , Enterobacter cloacae/virologia , Microbiologia de Alimentos/métodos , Pseudomonas fluorescens/virologia , Verduras/microbiologia , Aerobiose , Bacteriófagos/genética , Bacteriófagos/isolamento & purificação , Cucumis sativus/metabolismo , Enterobacter cloacae/metabolismo , Fermentação , Especificidade de Hospedeiro , Lactobacillus plantarum/metabolismo , Nitritos/metabolismo , Pseudomonas fluorescens/metabolismo
3.
Food Chem ; 280: 195-202, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30642486

RESUMO

In this work, a novel simple, fast, selective and inexpensive fluorescence method for the determination of curcumin based on the fluorescence quenching of nitrogen and chlorine dual-doped carbon nanodots (N,Cl-CDs) was for the first time presented. The N,Cl-CDs were fastly and greenly produced by simply mixing glucose, 1,2-ethylenediamine (EDA) and hydrochloric acid (HCl). The fluorescence of N,Cl-CDs was significantly quenched by curcumin via a synergistic effect of dynamic quenching and inner filter effect (IFE). The N,Cl-CDs shows high selectivity and sensitivity towards curcumin sensing, achieving a linear range of 0.1-35 µM and a limit of detection (LOD) as low as 38 nM. The proposed fluorescence method was successfully utilized for curcumin detection in food samples with recoveries in a range of 96.8-106.1%. The findings of this study suggest the feasibility and usefulness of N,Cl-CDs as an effective fluorescence probe for the determination of curcumin in complex food matrix.


Assuntos
Carbono/química , Cloro/química , Curcumina/análise , Nitrogênio/química , Pontos Quânticos/química , Espectrometria de Fluorescência , Etilenodiaminas/química , Corantes Fluorescentes/química , Análise de Alimentos/métodos , Glucose/química , Ácido Clorídrico/química , Limite de Detecção
4.
Carbohydr Polym ; 207: 362-370, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30600018

RESUMO

Effect of pulsed electric field (PEF) on the structural properties of representative starches with different crystalline type, wheat starch for type A, potato starch for type B, and pea starch for type C, were investigated with polarized light microscopy (PLM), X-ray diffractometry (XRD), attenuated total internal reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, solid-state nuclear magnetic resonance (SSNMR) spectroscopy, small-angle X-ray scattering (SAXS), and gel permeation chromatography (GPC) to understand whether PEF could be applied directly in starchy foods. The results showed that PEF could change the structure of all three types of starch, especially potato starch; the birefringence, represented by Maltese cross in polarized microscopic observation changed slightly; XRD and SSNMR spectra demonstrated PEF did not change the crystalline type of starch granules. However, relative crystallinity variations happened at some points of electric field intensity (EFI). Increasing with the EFI, a bigger variation of R1045/1022 happened in potato starch than in wheat starch and pea starch, as illustrated by ATR-FTIR. Significant influences of PEF on the scatter structure and fractal dimension of self-similar structures were observed for wheat starch and potato starch, but not for pea starch. The GPC suggested that molecular weight distribution changed for all the three starches. And in vitro tests showed that PEF changed significantly (P < 0.05) the digestibility of starches, especially wheat starch and potato starch.

5.
Int J Food Microbiol ; 292: 107-117, 2019 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-30594742

RESUMO

The growth of Shewanella spp., mainly S. baltica and S. putrefaciens, is responsible for the spoilage of chilled fresh fish. Phages are an alternative tool to control bacterial growth. In this study, virulent phages infecting 4 S. baltica and 6 S. putrefaciens strains were isolated and characterized. Transmission electron microscopy revealed that 6 out of 10 phages (3 phages infecting S. baltica and 3 phages infecting S. putrefaciens) belonged to Myoviridae, while the other 4 phages (1 phage infecting S. baltica and 3 phages infecting S. putrefaciens) belonged to Siphoviridae. Phage SppYZU01 and SppYZU05 showed the broadest host range, being lytic towards all the 4 S. baltica strains and 5 out of the 6 S. putrefaciens strains, respectively. The genome sequence of SppYZU01 had no similarity with known genome sequences, while that of SppYZU05 was 88.5% similar to the genome of a virulent S. putrefaciens-infecting phage (Spp001). According to the host range and lytic activity, 3 phages, including SppYZU01, SppYZU05, and SppYZU06, were combined into a cocktail (designated as SPMIX3-156). SPMIX3-156 showed potential as an antimicrobial agent to control S. baltica and S. putrefaciens strain growth in catfish matrices. Bacterial growth in the catfish muscle juice inoculated with 104 colony-forming units (CFU)/mL of Shewanella strains was partially inhibited by 105 plaque-forming units (PFU)/mL of SPMIX3-156 at both 25 °C and 4 °C. The catfish fillets inoculated with Shewanella strains were used as a model to evaluate the biopreservative effects of SPMIX3-156. Total viable counts of fillet samples treated with 107 PFU/mL of SPMIX3-156 were reduced by 3.21 and 2.75 log units after 1 day at 25 °C and 10 day at 4 °C, respectively, compared to those of untreated samples. Fillet quality indices, including pH, total volatile basic nitrogen, and sensory value of the SPMIX3-156-treated samples, considerably improved compared to those of the control samples at both 4 °C and 25 °C. Our results suggest that SPMIX3-156 is a promising biological agent against S. baltica and S. putrefaciens, and may have a potential use in chilled fish fillet biopreservation.


Assuntos
Bacteriófagos/genética , Genes Virais , Ictaluridae/microbiologia , Shewanella putrefaciens/virologia , Shewanella/virologia , Animais , Bacteriófagos/isolamento & purificação , Agentes de Controle Biológico , Contagem de Colônia Microbiana , DNA Viral/isolamento & purificação , Contaminação de Alimentos , Microbiologia de Alimentos , Conservação de Alimentos , Myoviridae/isolamento & purificação , Alimentos Marinhos/microbiologia , Análise de Sequência de DNA , Siphoviridae/isolamento & purificação
6.
J Microbiol Biotechnol ; 27(11): 1971-1982, 2017 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-28910860

RESUMO

Piliated Lactobacillus rhamnosus (pLR) strains possess higher adherent capacity than non-piliated strains. The objective of this study was to isolate and characterize probiotic pLR strains in human fecal samples. To this end, mouse polyclonal antiserum (anti-SpaA) against the recombinant pilus protein (SpaA) of L. rhamnosus strain GG (LGG) was prepared and tested for its reactivity and specificity. With the anti-SpaA, a method combining the de Man, Rogosa, and Sharpe (MRS) agar plating separation and colony immunoblotting (CIB) was developed to isolate pLR from 124 human fecal samples. The genetic and phenotypic characteristics of the resultant pLR isolates were compared by randomly amplified polymorphic DNA (RAPD) fingerprinting, and examination of adhesion to Caco-2 cells, hydrophobicity, autoaggregation, and in vitro gastrointestinal tolerance. Anti-SpaA specifically reacted with three pLR strains of 25 test strains, as assessed by western blotting, immunofluorescence flow cytometry, and immunoelectron microscopy (IEM) assays. The optimized MRS agar separation plus anti-SpaA-based CIB procedure could quantitatively detect 2.5 × 103 CFU/ml of pLR colonies spiked in 106 CFU/ml of background bacteria. Eight pLR strains were identified in 124 human fecal samples, and were confirmed by 16S RNA gene sequencing and IEM identification. RAPD fingerprinting of the pLR strains revealed seven different patterns, of which only two isolates from infants showed the same RAPD profiles with LGG. Strain PLR06 was obtained with high adhesion and autoaggregation activities, hydrophobicity, and gastrointestinal tolerance. Anti-SpaA-based CIB is a rapid and inexpensive method for the preliminary screening of novel adherent L. rhamnosus strains for commercial purposes.


Assuntos
Fezes/microbiologia , Proteínas de Fímbrias/imunologia , Microbioma Gastrointestinal/fisiologia , Soros Imunes/imunologia , Immunoblotting/métodos , Lactobacillus rhamnosus/imunologia , Lactobacillus rhamnosus/isolamento & purificação , Probióticos , Ácidos , Animais , Aderência Bacteriana/efeitos dos fármacos , Aderência Bacteriana/imunologia , Ácidos e Sais Biliares/farmacologia , Western Blotting , Células CACO-2 , Análise por Conglomerados , Reações Cruzadas/imunologia , Microbioma Gastrointestinal/efeitos dos fármacos , Microbioma Gastrointestinal/imunologia , Humanos , Interações Hidrofóbicas e Hidrofílicas , Lactobacillus rhamnosus/efeitos dos fármacos , Lactobacillus rhamnosus/genética , Proteínas de Membrana/química , Proteínas de Membrana/imunologia , Camundongos , Subunidades Proteicas , RNA Ribossômico 16S/genética , Técnica de Amplificação ao Acaso de DNA Polimórfico , Proteínas Recombinantes/imunologia
7.
Food Chem Toxicol ; 50(5): 1238-44, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22300772

RESUMO

Evaluation of the chemical composition and antihyperglycemic and antioxidant activity of five wild edible mushrooms (Clitocybe maxima, Catathelasma ventricosum, Stropharia rugoso-annulata, Craterellus cornucopioides and Laccaria amethystea) from Southwest China. The chemical composition assay includes proximate analysis (moisture, ash, crude protein, crude fat, total carbohydrates and total energy), bioactive compounds analysis (total phenolic, flavonoid, ascorbic acid, ergosterol, tocopherol), fatty acid analysis, amino acid analysis, phenolic compounds analysis and mineral analysis of these mushrooms. Furthermore, assays of α-glucosidase inhibitory and α-amylase inhibitory activity were used for evaluating antihyperglycemic activity of the mushrooms, and assays of reducing power, chelating effect on ferrous ions, scavenging effect on hydroxyl free radicals and 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were used for evaluating antioxidant activity of the mushrooms. Based on the results, ethanolic and aqueous extract of these mushroom all showed antihyperglycemic and antioxidant potential. In particular, the aqueous extract of C. ventricosum revealed the highest α-glucosidase inhibitory activity (EC50 value 2.74 µg/mL), DPPH radical scavenging activity (EC50 value 2.86 mg/mL) and reducing power (EC50 value 0.96 mg/mL), while the aqueous extract of L. amethystea showed the highest α-amylase inhibitory activity (EC50 value 4.37 µg/mL) and metal chelating activity (EC50 value 2.13 mg/mL).


Assuntos
Agaricales/química , Antioxidantes/uso terapêutico , Hipoglicemiantes/uso terapêutico , Agaricales/classificação , Antioxidantes/farmacologia , China , Cromatografia Líquida de Alta Pressão , Avaliação Pré-Clínica de Medicamentos , Inibidores de Glicosídeo Hidrolases , Hipoglicemiantes/farmacologia , Especificidade da Espécie , alfa-Amilases/antagonistas & inibidores
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA