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After the grinding stage of yam tubers, ultrasonic treatment (UT) is compared to traditional starch extraction. Different sonication conditions of amplitude (12, 40, and 68%) and time (3, 6, and 9 min) are evaluated along two other treatments: a control (0% amplitude) and 70% amplitude for 15 min, in order to compare the traditional extraction method and extreme ultrasonic conditions. Extraction yield, centesimal composition, color instrumental analysis, scanning electron microscopy, optical microscopy, particle size, x‐ray diffraction, swelling power and solubility, paste clarity, pasting properties, thermal properties, and absolute density are used to evaluate the isolated starches. Yield increased from 29.85% (control) to 32.09% (70% amplitude, 15 min). The surface of certain sonicated treated starch becomes damaged, also amorphous region is reduced, but no change in the crystalline pattern of starch is observed, characterized as B type. Except for treated starches at 70% amplitude for 15 min, all others showed no change or slight increase of peak viscosity. Despite the increase in yield, ultrasound caused changes on physical and chemical characteristics, depending on time and amplitude, hence it may be used as alternative technique for physical starch modification, for example, for producing thickeners agent.

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The objective of this study was to evaluate the effect of temperature and drying time on the total phenolic content and antioxidant capacity of grape pomace. Experimental data of the drying kinetics were fitted to six mathematical models and the Page model was selected as the most suitable to represent the drying of grape pomace. The best preservation of the phenolic compounds and antioxidant capacity was observed at 60 °C, suggesting that the temperatures of 40 °C and 50 °C were not sufficient to inactivate the enzyme polyphenol oxidase, being responsible for the greater degradation of these compounds. Keywords: Antioxidant capacity; Drying kinetics; Mathematical modeling; Water activity; Polyphenol oxidase. ResumoO objetivo deste estudo foi avaliar o efeito da temperatura e do tempo de secagem sobre o conteúdo de compostos fenólicos totais e a capacidade antioxidante do bagaço de uva. Os dados experimentais das cinéticas de secagem foram ajustados a seis modelos matemáticos. O modelo de Page foi selecionado como o mais adequado para representar a secagem do bagaço de uva. A melhor preservação dos compostos fenólicos e da capacidade antioxidante foi observada a 60 °C, sugerindo que as temperaturas de 40 °C e 50 °C não foram suficientes para inativar a ação da enzima polifenoloxidase, sendo estas as responsáveis pela maior degradação desses compostos. Palavras-chave:

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