Pectin and pectin/chitosan hydrogel beads as coffee essential oils carrier systems

Two pectin fractions extracted from coffee pulp, one high-methoxylated (Coffea arabica pectin, CAP) and other low-methoxylated (chelating agent-soluble pectic fraction, CSP), were used for the development of hydrogel beads loaded with coffee roasted and green essential oils (EOs). The aim of the study was to compare the two types of pectin, with or without chitosan, on their encapsulation performance for the delivery of EOs. Systems were analyzed regarding their rheological, morphological, physicochemical and mechanical properties. Association with chitosan reinforced the beads, which showed better mechanical properties and resisted to acidic and basic treatments, influenced by EO type. ATR-FTIRspectroscopy and X-ray diffraction were performed to assess structural characteristics and interactions of the different samples. The analyses showed that alkaline treatment caused more structural modifications than the acidic treatment in the polysaccharide matrix. Swelling ability of CAP was higher than that of CSP, and green coffee oil prevented bead degradation by acids. Controlled release was carried out in fatty food simulant, and the formulations containing CAP and chitosan had the highest release values. DPPH radical scavenging activity showed that coffee essential oils can act as antioxidants, with the roasted coffee oil presenting superior antioxidant activity.