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1.
Food Chem ; 304: 125442, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31491714

RESUMO

In this study, the effects of moderate electric fields during thermal denaturation of ß-lactoglobulin were examined through an in situ circular dichroism approach, complemented by intrinsic extrinsic fluorescence analysis. Results have shown that the effects of electric fields in protein unfolding were linearly dependent on the applied electric field intensity (V/cm) and increased by the use of low electric frequencies - i.e. 50 to 200 Hz. These electric effects caused significant changes on ß-lactoglobulin melting temperature, unfolded conformation and subsequent intermolecular interactions, revealed by the increase of surface hydrophobicity (ANS affinity) and higher conservation of retinol binding. The obtained data provides a clear evidence that moderate electric fields contribute to distinct folding/unfolding of ß-lactoglobulin, resulting in structural modifications. These findings are relevant for (bio)-technological applications involving electric fields processing, bringing new insights for the development of innovative strategies to control protein function and tune production of functional protein systems.

2.
J Agric Food Chem ; 66(43): 11227-11233, 2018 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-30296069

RESUMO

Milk proteins are being widely used in formulated foods as a result of their excellent technological, functional, and biological properties. However, the most representative proteins from casein and whey fractions are also recognized as major allergens and responsible for the prevalence of cow's milk protein allergy in childhood. Electroheating technologies based on thermal processing of food as a result of application of moderate electric fields, also known by ohmic heating (OH) or Joule effect, are establishing a solid foothold in the food industry. Currently, the influence of OH on allergenic aspects of milk proteins is under debate but still undisclosed. The occurrence of electrical effects on the protein structure and its function has already been reported; thus, the impact of OH over allergenicity should not be overlooked. On the basis of these recent findings, it is then relevant to speculate about the impact of this emergent technology on the potential allergenicity of milk proteins.


Assuntos
Eletricidade , Manipulação de Alimentos/métodos , Proteínas do Leite/química , Proteínas do Leite/imunologia , Alérgenos/química , Alérgenos/imunologia , Temperatura Alta , Hipersensibilidade a Leite
3.
Food Res Int ; 99(Pt 1): 435-443, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28784503

RESUMO

The influence that ohmic heating technology and its associated moderate electric fields (MEF) have upon production of whey protein isolate cold-set gels mediated by iron addition was investigated. Results have shown that combining heating treatments (90°C, 5min) with different MEF intensities let hydrogels with distinctive micro and macro properties - i.e. particle size distribution, physical stability, rheological behavior and microstructure. Resulting hydrogels were characterized (at nano-scale) by an intensity-weighted mean particle diameter of 145nm, a volume mean of 240nm. Optimal conditions for production of stable whey protein gels were attained when ohmic heating treatment at a MEF of 3V∙cm-1 was combined with a cold gelation step using 33mmol∙L-1 of Fe2+. The consistency index of hydrogels correlated negatively to MEF intensity, but a shear thickening behavior was observed when MEF intensity was increased up to 10V∙cm-1. According to transmission electron microscopy, ohmic heating gave rise to a more homogenous and compact fine-stranded whey protein-iron microstructure. Ohmic heating appears to be a promising technique, suitable to tailor properties of whey protein gels and with potential for development of innovative functional foods.

4.
Carbohydr Polym ; 129: 127-34, 2015 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-26050897

RESUMO

Montmorillonite modified with a quaternary ammonium salt C30B/starch nanocomposite (C30B/ST-NC), silver nanoparticles/starch nanocomposite (Ag-NPs/ST-NC) and both silver nanoparticles/C30B/starch nanocomposites (Ag-NPs/C30B/ST-NC) films were produced. The nanoclay (C30B) was dispersed in a starch solution using an ultrasonic probe. Different concentrations of Ag-NPs (0.3, 0.5, 0.8 and 1.0mM) were synthesized directly in starch and in clay/starch solutions via chemical reduction method. Dispersion of C30B silicate layers and Ag-NPs in ST films characterized by X-ray and scanning electron microscopy showed that the presence of Ag-NPs enhanced clay dispersion. Color and opacity measurements, barrier properties (water vapor and oxygen permeabilities), dynamic mechanical analysis and contact angle were evaluated and related with the incorporation of C30B and Ag-NPs. Films presented antimicrobial activity against Staphylococcus aureus, Escherichia coli and Candida albicans without significant differences between Ag-NPs concentrations. The migration of components from the nanostructured starch films, assessed by food contact tests, was minor and under the legal limits. These results indicated that the starch films incorporated with C30B and Ag-NPs have potential to be used as packaging nanostructured material.


Assuntos
Anti-Infecciosos/farmacologia , Embalagem de Alimentos , Nanoestruturas/química , Amido/química , Silicatos de Alumínio/química , Candida albicans/efeitos dos fármacos , Argila , Cor , Módulo de Elasticidade , Escherichia coli/efeitos dos fármacos , Alimentos , Nanopartículas Metálicas/química , Testes de Sensibilidade Microbiana , Oxigênio/análise , Permeabilidade , Prata/química , Staphylococcus aureus/efeitos dos fármacos , Vapor , Água/química , Difração de Raios X
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