Effect of encapsulating agent on physical-chemical characteristics of olive pomace polyphenols-rich extracts

During the last years, olive industry wastes are considered as a potential source of extracts with antioxidant properties rich in polyphenols. The recovery of these added-value compounds can be interesting both for their beneficial properties and from an environmental point of view and several studies have been performed for the optimization and characterization of the phenolic compounds present in olive pomace liquid extracts. However, dried forms of natural extracts are associated with several advantages over liquid forms, such as limited storage costs, higher concentration and stability of target compounds. Spray drying is one of the most common techniques for the transformation of a liquid extract, or food formulation, into dried powder, due to low operative costs respect to other methods, and high flexibility, related to the large number of operative parameters that can be optimized, such as coating agent type and concentration, inlet temperature, feed flow and aspiration rate. In this study, an ethanolic extract rich in phenolic compounds from olive pomace (Taggiasca cultivar) was obtained by high pressure and temperature extraction and spray dried with different ratios of gum Arabic and maltodextrin as coating agents (0:100, 20:80, 40:60, 60:40, 80:20 and 100:0 % w/w). The total amount of coating agent was maintained constant and equal to 10 % w/v (100 g/L). Inlet temperature, feed flow and aspiration rate were 160 °C, 5 mL/min and 30 m3/h, respectively. For all products, moisture content, water solubility index, total polyphenol content, antiradical power and microencapsulation yield were determined. The results of this study show that the coating agent and process conditions led to the production of microencapsulated powders with improved water dissolution rate and a minimal loss in phenolics during the drying phase. The obtained microparticles, due to their high content in bioactive compounds and ease of handling, can have potential industrial applications as functional components for foods or nutraceuticals purposes.