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a b s t r a c tAnthocyanin stability and antioxidant activity of powdered açai juice was evaluated throughout 120 days. Powders were produced by spray drying using four types of carrier agents: maltodextrin 10DE, maltodextrin 20DE, gum Arabic and tapioca starch. Samples were stored at different temperatures (25 and 35°C) and water activities (0.328 and 0.529), in order to verify the effect of these conditions on anthocyanin degradation and antioxidant activity reduction. Anthocyanin degradation exhibited two first-order kinetics: the first one, with higher reaction rate constant, up to 45-60 days of storage, and the second one, after this period, with lower degradation rate. Both temperature and water activity negatively affected anthocyanin stability. Antioxidant activity also decreased with increasing water activity, but was higher for the powders stored at 35°C. Maltodextrin 10DE was the carrier agent that showed the best pigment protection and the highest antioxidant activity, for all the conditions studied.

The objective of this work was to study the influence of some process conditions on the microencapsulation of flaxseed oil by spray drying. The process was carried out on a mini spray dryer and gum Arabic was used as wall material. Seventeen tests were made, according to a central composite design. Independent variables were: inlet air temperature (138-202°C), total solid content (10-30% w/w) and oil concentration with respect to total solids (10-30% w/w). Encapsulation efficiency, lipid oxidation and powder bulk density were analyzed as responses. Powder morphology and particle size distribution were also analyzed. The feed emulsions were characterized with respect to droplet size and viscosity. Higher solid content and lower oil concentration led to higher encapsulation efficiency and lower lipid oxidation, which was related to the higher emulsion viscosity and lower droplets size. Increasing drying temperature resulted in higher lipid oxidation. Bulk density increased when higher solid content and lower inlet air temperature were used. The particles were rounded and shriveled, and their mean diameter was mainly affected by total solid content.

Physicochemical and morphological properties of ac¸ai powder produced with different carrier agents were evaluated in this work. Powders were produced by spray drying, using maltodextrin 10DE, maltodextrin 20DE, gum arabic and tapioca starch as carrier agents. Powder characterisation included analysis of moisture content, water activity, solubility, hygroscopicity, particle size distribution, morphology, total polyphenolics and antioxidant activity. Results showed that the samples produced with maltodextrin 20DE and gum arabic presented the smallest size and highest hygroscopicity. The powder produced with tapioca starch exhibited the lowest hygroscopity and solubility, and the highest mean diameter. With regard to morphology, all particles exhibited spherical and shrivelled surfaces, except those produced with tapioca starch, which exhibited rounded and smooth surfaces. Powders produced with maltodextrins and gum arabic showed high polyphenolic retention and antioxidant activity preservation after storage at 40°C for 15 days, while for the particles produced with tapioca starch, this protective effect was less pronounced.

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a b s t r a c tSorption isotherms and glass transition temperature (T g ) of powdered açai juice were evaluated in this work. Powders were produced by spray drying using different materials as carrier agents: maltodextrin 10DE, maltodextrin 20DE, gum Arabic and tapioca starch. The sorption isotherms were determined by the gravimetric method, while the T g of powders conditioned at various water activities were determined by differential scanning calorimetry. As results, experimental data of water adsorption were well fitted to both BET and GAB models. Powders produced with maltodextrin 20DE and gum Arabic showed the highest water adsorption, followed by those produced with maltodextrin 10DE and with tapioca starch, respectively. With respect to the glass transition temperature, Gordon-Taylor model was able to predict the strong plasticizing effect of water on this property. Both a w and T g were used to determine the critical conditions for food storage, at which powders are not susceptible to deteriorative changes such as collapse, stickiness and caking.