RESUMO
Gelling temperatures of commercial kappa-carrageenan solutions were measured using dynamic oscillatory shear rheometry, in response to varying polymer (0.4% to 1.6%, w/w) and added Ca(2+) (5 to 20 mM) salts. Gelling temperatures were found to shift to higher temperatures with increased polymer and Ca(2+) concentration. The Tang model was used to estimate the number of Ca(2+)-mediated cross-links formed with kappa-carrageenan at the onset of junction zone formation. Based on this model, 6 kappa-carrageenan double helices were estimated to be cross-linked by 5 Ca(2+) ions through ionic bridging and electrostatic attraction, within a cross-linking region equivalent to one pitch of the double helix.
Assuntos
Cálcio/química , Carragenina/química , Aditivos Alimentares/química , Transição de Fase , Cálcio/análise , Configuração de Carboidratos , Cátions/análise , Cátions/química , Módulo de Elasticidade , Géis/química , Modelos Químicos , Concentração Osmolar , Temperatura de TransiçãoRESUMO
To improve survival during exposure to adverse conditions, probiotic Bifidobacterium adolescentis 15703T cells were encapsulated in novel mono-core and multi-core phase-separated gelatine-maltodextrin (GMD) microspheres where the gelatine (G) phase was cross-linked with genipin (GP). Microscopy showed that encapsulated cells were exclusively associated with maltodextrin (MD) core(s). Small (average diameter 37 microm) and large (70 microm) GMD and G microspheres were produced by modulating factors (e.g. mixing speed, surfactant, GP and G concentrations) affecting the size, structural stability and phase-separation. In vitro sequential gastro-intestinal (GI) juice challenge experiments revealed increased survival of cells encapsulated in GMD ( approximately 10(6-7) cfu mL(-1)) and G (approximately 10(5) cfu mL(-1)) microspheres as compared to free cells (approximately 10(4) cfu mL(-1)). In GMD microspheres, the bacteria derive energy from MD to survive during exposure to acid and bile salts. In conclusion, the novel food grade GMD microencapsulation formulation was shown to protect probiotic bifidobacteria from adverse conditions.
Assuntos
Bifidobacterium/citologia , Composição de Medicamentos/métodos , Gelatina/química , Glicosídeos Iridoides/química , Polissacarídeos/química , Probióticos , Células Imobilizadas/citologia , Reagentes de Ligações Cruzadas/química , Suco Gástrico/metabolismo , Suco Gástrico/microbiologia , Trato Gastrointestinal/metabolismo , Trato Gastrointestinal/microbiologia , Iridoides , Transição de FaseRESUMO
A capillary gel electrophoretic (CGE) method for the quantitative analysis of RuBisCo in spinach leaves was developed. RuBisCo was resolved into large and small subunits in the presence of sodium dodecyl sulphate (SDS) by the CGE procedure which enabled the determination of the molecular weight of each unit accurately; the values so determined were in close agreement with those reported using other methods. Advantages of CGE over SDS-polyacrylamide gel electrophoresis and high-pressure gel filtration include decreased sample preparation and analysis time, superior resolution and greater sensitivity permitting reduced sample size and trace analysis. In addition, CGE provided precise quantification of RuBisCo and was demonstrated to be a viable alternative to other available methods of protein analysis.