Valorization of grape pomace: Encapsulation and storage stability of its phenolic extract

The objective of this work is to optimize a new method of grape pomace application in food industries, based on the microwave-assisted extraction of phenolic compounds followed by their encapsulation by spray drying. Mixtures of maltodextrin and milk proteins were used as wall materials. An expected integrated mean-squared error (EIMSE) optimal design was applied to determine the effects of inlet air temperature, ratio of core to wall material, and drying air flow rate on encapsulation efficiency and yield. Characterization of powder properties was accomplished to determine if successful development of the product was achieved. Mathematical models were developed to describe the relationship between the operating and response variables. In this case of yield, the inclusion of a new independent variable, the outlet air temperature, improved the predictive ability of the model. Moreover, a good correlation was found between the product yield and the amount that the droplet temperature has exceeded its glass transition temperature. The optimum values of encapsulation efficiency (92.49%) and yield (37.28%) were predicted. Furthermore, the antioxidant capacity and stability of the crude and the encapsulated extract were evaluated during storage at accelerated conditions. (C) 2018 Elsevier B.V. All rights reserved.