Gum Arabic -pectin powders loaded with eggplant peels’ extract

Abstract

Addressing the instability issues of anthocyanins, the present work studied the encapsulation of anthocyanin rich eggplant peel extract in powders formed by oven drying using gum arabic alone or in mixtures with high and low methoxyl pectins. Moreover, the powders were incorporated in gelatine gels, in order to investigate their exploitation in food formulations as natural colour and antioxidant sources. Despite the heat sensitive nature of anthocyanins, the oven process resulted in great yield (75.31–87 %) and encapsulation efficiency (79.88–94.72 %) values. The powders shared similar moisture content (0.35–0.51 %) and solubility (63.15–63.69 %) with their bulk, tapped and particle densities and porosity varying from 0.67 to 0.75 g/cm³, 0.70–0.82 g/cm³, 1.18–2.51 g/cm³ and 40.7–65.6 %, respectively. They had very good flowability (Carr Index: ∼5), low cohesiveness (Hausner ratio ∼1.06), good wettability (<2 s) and their dispersibility ranged from 40 to 53.4 %. Redness was close to +30 as expected due to the presence of anthocyanins. The phenolics content of the powders (0.089–0.124 mg GAE/0.5 mL) was lower than that of the initial extract (0.243 mg GAE/0.5 mL) whereas their antioxidant activity was 40 %. Regarding the wall material, the incorporation of pectins led to powders with increased porosity and particle density, better wettability and worst dispersibility. FT-IR suggested possible polysaccharide-polysaccharide and polysaccharide–extract interactions. No anthocyanins were detected in the gels. However, their AA ranged from 15.46 to 53.79 %. Overall, the present work can be a first step in the modulation of anthocyanin loaded powders for future use as encapsulating, antioxidant and colour agents in food matrices.