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1.
Food Chem ; 305: 125435, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31494497

RESUMO

Soluble dietary fibre (SDF) of micronized and non-micronized powders of lotus root nodes were investigated based on its adsorption and activity inhibition of pancreatic lipase (PL) by using circular dichroism, fluorescence spectroscopy and modification. Results showed that SDF2 (SDF from micronized powders of lotus root nodes) had stronger PL adsorption and enzyme activity inhibition than SDF1 (SDF from non-micronized powders of lotus root nodes). Specifically, SDF2 showed more binding sites than SDF1 in PL. There were hydrogen bonds and van der Waals interactions between SDF and PL, with Trp on PL probably serving as the main binding site. Carboxyl groups exhibited a stronger inhibition on PL by carboxymethyl and hydroxypropyl modification. The common mechanisms between SDF1 and SDF2 can be attributed to the combination between Trp and carboxyl groups, while the differences may be generated by the variations in structures or chemical groups induced by micronization.

2.
Food Chem ; 279: 373-378, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30611503

RESUMO

The differences in cell wall polysaccharides are considered as a major influencing factor on the texture of plant-based food after cooking. Here, 18 varieties of lotus rhizomes were collected from different regions of China and subjected to analysis, with the aim to identify the key factors that affect the texture of lotus rhizomes after cooking. The texture (hardness) of fresh samples and the samples after thermal treatment for different time periods was examined. The cell wall polysaccharides present in alcohol insoluble residue (AIR) were further subdivided into different fractions, and the composition of monosaccharides in each fraction was analyzed by gas chromatography. We then calculated the sugar ratios to examine the discrepancies in molecular structure among the fractions. Principal component analysis and regression analysis showed that the ratio of chelate-soluble fraction (CSF) to AIR is the major factor affecting the texture of lotus rhizomes after cooking.


Assuntos
Culinária , Lotus/química , Rizoma/química , Parede Celular/química , China , Culinária/métodos , Etanol/química , Dureza , Ácidos Hexurônicos/análise , Monossacarídeos/análise , Pectinas/química , Polissacarídeos/química , Análise de Componente Principal , Análise de Regressão , Rizoma/citologia
3.
Food Chem ; 278: 502-508, 2019 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-30583404

RESUMO

This study aims to investigate the impact of ferulic acid pretreatment on the hardness of Chinese radish after cooking. Radish slices were immersed in ferulic acid solution and distilled water, respectively. The ferulic acid treated samples showed significantly higher hardness (p < 0.05) than the control samples after cooking, and could keep relatively more integrated cell wall structure after cooking at 100 °C for 30 min. Subsequently, we determined the cell wall fraction contents, sugar ratio and molecular weight distribution of different treated samples. Ferulic acid treated groups showed higher percentage of chelate-soluble fraction (CSF) and sugar ratio 1 than the control groups in both fresh and cooked samples. The CSF had two high molecular weight peaks at 7.7 min and 8.6 min, probably due to the cross-linking with ferulic acid. This research may provide an effective way to decrease the softening of thermally processed fruits and vegetables.


Assuntos
Culinária/métodos , Ácidos Cumáricos/química , Raphanus/química , Temperatura Alta
4.
Food Chem ; 228: 204-210, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-28317714

RESUMO

The effects of acetic acid pretreatment on the texture of cooked potato slices were investigated in this work. Potato slices were pretreated with acetic acid immersion (AAI), distilled water immersion (DWI), or no immersion (NI). Subsequently, the cell wall material of the pretreated samples was isolated and fractioned to evaluate changes in the monosaccharide content and molar mass (MM), and the hardness and microscopic structure of the potato slices in different pretreatments before and after cooking were determined. The results showed that the highest firmness was obtained with more intact structure of the cell wall for cooked potato slices with AAI pretreatment. Furthermore, the MM and sugar ratio demonstrated that the AAI pretreated potato slices contained a higher content of the small molecular polysaccharides of cell walls, especially in the hemicellulose fraction. This work may provide a reference for potato processing.


Assuntos
Ácido Acético/química , Parede Celular/efeitos dos fármacos , Polissacarídeos/química , Solanum tuberosum/química , Culinária/métodos , Dureza
5.
Food Chem ; 211: 409-14, 2016 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-27283649

RESUMO

Pretreatments such as low temperature blanching and/or calcium soaking affect the cooked texture of vegetal food. In the work, lotus rhizomes (Nelumbo nucifera Gaertn.) were pretreated using the following 4 treatments, blanching at 40°C, blanching at 90°C, soaking in 0.5% CaCl2, and blanching at 40°C followed by immersion in 0.5% CaCl2. Subsequently, the cell wall material of pretreated samples was isolated and fractioned to identify changes in the degree of esterification (DE) and monosaccharide content of each section, and the texture of the lotus rhizomes in different pre-treatments was determined after thermal processing with different time. The results showed that the greatest hardness was obtained after blanching at 40°C in CaCl2, possibly attributing to the formation of a pectate calcium network, which maintains the integrity of cell walls. Furthermore, the content of galactose, rhamnose and arabinose decreased due to the breakage of sugar backbones and subsequent damage to cell walls. Our results may provide a reference for lotus rhizome processing.


Assuntos
Cálcio/toxicidade , Temperatura Alta/efeitos adversos , Nelumbo/química , Nelumbo/efeitos dos fármacos , Rizoma/química , Rizoma/efeitos dos fármacos , Antioxidantes/análise , Antioxidantes/química , Cálcio/administração & dosagem , Fenômenos Químicos/efeitos dos fármacos , Extratos Vegetais/análise , Extratos Vegetais/química
6.
Luminescence ; 27(1): 34-8, 2012 Jan-Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21674749

RESUMO

The adenosine triphosphate (ATP) bioluminescence rapid determination method may be useful for enumerating the total viable count (TVC) in soy sauce, as it has been previously used in food and beverages for sanitation with good precision. However, many factors interfere with the correlation between total aerobic plate counts and ATP bioluminescence. This study investigated these interfering factors, including ingredients of soy sauce and bacteria at different physiological stages. Using the ATP bioluminescence method, TVC was obtained within 4 h, compared to 48 h required for the conventional aerobic plate count (APC) method. Our results also indicated a high correlation coefficient (r = 0.90) between total aerobic plate counts and ATP bioluminescence after filtration and resuscitation with special medium. The limit of quantification of the novel detection method is 100 CFU/mL; there is a good linear correlation between the bioluminescence intensity and TVC in soy sauce in the range 1 × 10(2) -3 × 10(4) CFU/mL and even wider. The method employed a luminescence recorder (Tristar LB-941) and 96-well plates and could analyse 50-100 samples simultaneously at low cost. In this study, we evaluated and eliminated the interfering factors and made the ATP bioluminescence rapid method available for enumerating TVC in soy sauce.


Assuntos
Medições Luminescentes , Alimentos de Soja/microbiologia , Trifosfato de Adenosina , Bactérias/citologia , Contagem de Colônia Microbiana , Limite de Detecção
7.
Biosens Bioelectron ; 24(8): 2323-7, 2009 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-19261458

RESUMO

A novel flow injection chemiluminescence (CL) sensor for the determination of maleic hydrazide (MH) using molecularly imprinted polymer (MIP) as recognition element is reported. The MH-MIP was synthesized by thermal initiated polymerization in methanol, using methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker in the maleic hydrazide template molecule. Molecular modeling was employed to simulate the possible recognition process of the MIP, and to achieve high selectivity. Then the synthesized MH-MIP was employed as recognition element by packing into flow cell to establish a novel flow injection CL sensor. The CL intensity responded linearly to the concentration of MH in the range 3.5x10(-4)-5.0x10(-2) mg/mL with a detection limit of 6.0x10(-5) mg/mL (3sigma), which is lower than that of conventional methods. The relative standard deviation (RSD) for the determination of 1.0 microg/mL of MH was 2.7% (n=11). The sensor is reusable and has a great improvement in sensitivity and selectivity for CL analysis. As a result, the new MIP-CL sensor had been successfully applied to the determination of MH in vegetable samples.


Assuntos
Técnicas Biossensoriais/instrumentação , Monitoramento Ambiental/instrumentação , Poluentes Ambientais/análise , Análise de Injeção de Fluxo/instrumentação , Medições Luminescentes/instrumentação , Hidrazida Maleica/análise , Hidrazida Maleica/química , Desenho de Equipamento , Análise de Falha de Equipamento , Herbicidas/análise , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Propriedades de Superfície
8.
Int J Food Sci Nutr ; 60(5): 432-8, 2009 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22519678

RESUMO

A novel method was developed to analyze lotus rhizome polyphenolic catechin using high-performance liquid chromatography (HPLC). The retain time of catechin was 14.72 min under the optimized condition. Mass spectrometry was further employed to qualify and quantify the purity of the catechin peak. Good linearity (R=0.9997) was obtained within the range of 50-1,000 ng. The coefficient of variance was determined as 5.2%, with a recovery rate of 97%. The detection and quantification limitations of catechin were 23 ng and 50 ng, respectively. The catechin level was 0.0025% in the lotus rhizome, and 0.011% in the knot of the lotus rhizome (Nelumbo nucifera cv. 'damao jie'). The optimized conditions of HPLC for catechin detection in the lotus rhizome matrix were as follows: the SuperlcosIL™ LC-18 analytical column (150 mm×4.6 mm, 5 µm), methanol-water-acetic acid (10:90:1, volume ratio) as the mobile phase, an UV detector at 280 nm, a flow rate of 0.8 ml/min, column temperature at 30°C, and an injection volume of 10 µl.


Assuntos
Antioxidantes/análise , Catequina/análise , Cromatografia Líquida de Alta Pressão/métodos , Nelumbo/química , Extratos Vegetais/química , Rizoma/química , Espectrometria de Massas/métodos , Temperatura Ambiente
9.
Biosens Bioelectron ; 22(6): 1087-91, 2007 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-16621501

RESUMO

As the daminozide (DM) and its metabolite have been identified to be potentially carcinogenic, rapid detection method for them is necessary for food safety. A type of piezoelectric crystal sensor has been prepared by using a molecularly imprinted polymer (MIP) as recognition element. The molecularly imprinted polymer was prepared by hot-induced precipitation polymerization, and then the polymer particles were fixed on the surface of the electrode. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to evaluate the obtained imprinted polymer particles and the MIP sensitive film coated on the electrode. The results showed that a typical time-response curve of the MIP-coated crystal to the DM solution had been given, frequency shifts versus logarithm changes of DM showed good linear correlation within the concentration range of 1.0x10(-9) to 10(-6) mg/mL (y=11.38 lg x+115.45, r=0.9872) and 1.0x10(-6) to 10(-1) mg/mL (y=25.22lgx+209.44, r=0.9938), respectively. The detection limit was 5.0x10(-8) mg/mL (S/N=3), which is lower than that of conventional methods. Further, computer simulation technology was employed to investigate the interaction between methacrylic acid and DM for elucidating the recognition mechanism. The influencing factor pH has also been investigated. The injection experiments of DM structurally related compounds indicated that the obtained sensor has high sensitivity, excellent selectivity, low cost, good reproducibility, and reusable property by combining with piezoelectric crystal and molecularly imprinted polymer.


Assuntos
Técnicas Biossensoriais/instrumentação , Eletroquímica/instrumentação , Polímeros/química , Succinatos/análise , Transdutores , Técnicas Biossensoriais/métodos , Eletroquímica/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Quartzo , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Propriedades de Superfície
10.
Wei Sheng Yan Jiu ; 34(2): 227-30, 2005 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-15952671

RESUMO

People have paid a more attention to the pesticides residues, so the rapid detection method is required. In this paper the application of molecular imprinting technique on the detection of pesticides residues was reviewed, including recognition principles, preparation, current applications, problems and its future.


Assuntos
Técnicas de Química Analítica/métodos , Resíduos de Praguicidas/análise , Técnicas Biossensoriais , Polímeros/química
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