RESUMO
The consumption of food with health benefits is growing today worldwide. This study was designed in order to incorporate papaya dietary fibre concentrates (DFCs) from peel and pulp dehydrated with the use of microwave (MW), or convection with hot air (CV) in oil-in- water emulsions. Results of studies indicated that Pulp DFC produced more stability to creaming (18 weeks) than Peel DFC (6 weeks). It was found that peel DFCs exerted up to 30% reduction in lipid peroxidation in comparison to the reference system during storage. Rheological analysis showed a similar behaviour when emulsions were mixed with pulp DFCs either dehydrated by MW or CV, while the dressing with peel DFCs had a much lower consistency than the former. The analysis of the emulsions micro-structure showed a polydisperse system of oil droplets and fiber structures trapping oil. Finally, emulsions with pulp DFCs showed a better consumer´s acceptance. These results also suggested that the use of DFCs may have high industrial potential in contributing to dietary fibre enrichment through technological intervention of emulsion formulation by papaya pulp and peel, increasing antioxidant property, consistency and stability during storage.
RESUMO
The cell wall polysaccharides of Regina and Sunburst cherry varieties at two developmental stages were extracted sequentially, and their changes in monosaccharide composition and functional properties were studied. The loosely-attached pectins presented a lower d-galacturonic acid/rhamnose ratio than ionically-bound pectins, as well as lower thickening effects of their respective 2% aqueous solution: the lowest Newtonian viscosity and shear rate dependence during the pseudoplastic phase. The main constituents of the cell wall matrix were covalently bound pectins (probably through diferulate cross-linkings), with long arabinan side chains at the RG-I cores. This pectin domain was also anchored into the XG-cellulose elastic network. Ripening occurred with a decrease in the proportion of HGs, water extractable GGM and xylogalacturonan, and with a concomitant increase in neutral sugars. Ripening was also associated with higher viscosities and thickening effects, and to larger distribution of molecular weights. The highest firmness and compactness of Regina cherry may be associated with its higher proportion of calcium-bound HGs localized in the middle lamellae of cell walls, as well as to some higher molar proportion of NS (Rha and Ara) in covalently bound pectins. These pectins showed significantly better hydration properties than hemicellulose and cellulose network. Chemical composition and functional properties of cell wall polymers were dependent on cherry variety and ripening stage, and helped explain the contrasting firmness of Regina and Sunburst varieties.