This study evaluated for first time the effect of Microwave (MW) radiation on systems based on potato and rice starches supplemented with 5% of calcium caseinate (CA) or soy protein isolate (SPI). The goal of this treatment was the physical modification of these starch-based systems to provide ingredients of new functionalities. The hydration and pasting properties as well as gel viscoelastic features were evaluated. Dynamic oscillatory rheological tests were used. The effect of MW treatment (MWT) depended on the starch botanical origin and was significantly affected by protein presence and type. MWT of starch + protein blends revealed the most notable changes when SPI was added. Adding it to rice starch decreased swelling power (-45%), altered viscometric profiles and reinforced gel structure with important increases in both viscoelastic moduli (+160%-G' and +58%-G''). In blends with potato starch, MWT increased water absorption capacity (+115%) and decreased water solubility index (-82%). MWT of protein-potato blends promoted gel stability, decreased their pasting profiles and resulted in enhanced viscoelastic moduli (+483-G' and 243%-G''). MWT combined with protein addition allows designing starch-based foods with tailored properties.

Abstract:Gold nanoparticles (AuNPs) have been obtained using musts (freshly prepared grape juices where solid peels and seeds have been removed) as the reducing and capping agent. Transmission Electron Microscope images show that the formed AuNPs are spherical and their size increases with the amount of must used. The size of the AuNPs increases with the Total Polyphenol Index (TPI) of the variety of grape. The kinetics of the reaction monitored using UV-Vis shows that the reaction rates are related to the chemical composition of the musts and specifically to the phenols that can act as reducing and capping agents during the synthesis process. Since the particular composition of each must produces AuNPs of different sizes and at different rates, color changes can be used to discriminate the variety of grape. This new technology can be used to avoid fraud.