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The physicochemical, pasting, thermal, viscoelastic, and syneresis properties of nine formulations prepared with wheat starch, potato starch, and hydrocolloids (pectin, HPMC, arabic gum, and konjac glucomannan (KG)) were assessed. The addition of the hydrocolloids decreased the water solubility index and water absorption capacity but did not modify the swelling power of starch granules. The starch gelatinization temperature decreased in the presence of the hydrocolloids, while the enthalpy of gelatinization and gelatinization range temperature increased. Pectin and HPMC addition decreased the paste viscosity whereas KG increased and arabic gum had no effect. On the other hand, the pasting temperature was not modified by the presence of hydrocolloids. All the blends behaved as solid as the storage modulus was higher than the viscous modulus within all the frequency range assayed. Viscous characteristics were improved with the addition of pectin and HPMC. The presence of hydrocolloids increased the stability of the gelled starch mixtures to freeze-thaw cycle and no syneresis was observed in these gels stored at 4°C.

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Yerba mate (Ilex paraguariensis) contains a high amount of polyphenols associated with antiradical activity and possible benefits for preventing degenerative diseases. Natural extracts from this South American herb were encapsulated in calcium alginate and calcium alginate-chitosan beads to be incorporated as an additive in food products. The interactions between the active compound and the polymers were evaluated by Scanning Electron Microscopy (SEM), thermal analysis (Thermo Gravimetric Assays, TGA, and Differential Scanning Calorimetry, DSC) and Fourier Transform Infrared Spectrometry (FT-IR) studies. Also, the effect of these interactions on extract release in a gastrointestinal model system was evaluated. Results showed the interactions between the calcium alginate matrix and the chitosan external layer. Also, interactions between the natural extract and each polymer were observed. In both encapsulation systems the highest polyphenol content was released in simulated gastric fluid. However, capsules coated with chitosan allowed releasing a higher amount of polyphenols into the simulated intestinal fluid. This fact was attributed to both the protecttion of the chitosan barrier and the strong interaction between yerba mate extract and chitosan.

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