Encapsulation of açaí (Euterpe oleracea) pulp with whey protein isolate by spray-drying: An optimization study using response surface methodology (RSM)

Abstract

Açaí fruit (Euterpe oleracea) is a rich source of bioactive compounds such as anthocyanins and flavonoids in general. However, once anthocyanins are easily degradable, efforts have been made toward the development of methods for preserving them from degradation throughout industrial processing. The objective of this study was to optimize the encapsulation of açaí pulp with whey protein isolate by spray drying. For this purpose, the Central Composite Rotational Design (CCRD) with response surface methodology (RSM) was applied to evaluate the influence of inlet temperature (Te), drying air flow rate (VA), and compressed air flow rate (VB) on the following response variables: encapsulation yield, water activity, hygroscopicity, density, ash, and protein, in addition to the content of the bioactive compounds anthocyanins and flavonoids. The coefficient of determination (R²) of CCRD ranged between 0.87 and 0.97, and the sum of squared error (SSE) varied from 0.0003 to 14505, indicating an adequate performance of this experimental design. In general, the optimization analysis showed that Te between 150 and 165 °C, VA below 2.9×10−5 m³ /s and VB less than 0.0006 m³ /s favored the minimization of water activity and hygroscopicity, 0.25 and 2.9 g/100 g, respectively, the maximization of density, and encapsulation yield (around 45%), as well as the preservation of both the anthocyanins (170 mg .100 g−1) and flavonoids (420 mg. 100 g−1), respectively, obtaining a high-quality product. This study represents a first step in the encapsulation of açaí, aiming not only to preserve its bioactive compounds but also to provide a product with a rich protein source, such as whey protein. Ultimately, this research offers potential industrial production alternatives, opens up a new field of study, and presents a potential new market opportunity for small, medium, and even large-scale producers.