Co-extrusion encapsulation of canola oil with alginate: Effect of quercetin addition to oil core and pectin addition to alginate shell on oil stability

This study investigates the feasibility of encapsulating antioxidant-fortified canola oil via co-extrusion using 0.67% alginate (0.67%A), 1% alginate (1%A) or high methoxyl (HM) pectin-enhanced alginate (A-P) as the encapsulant. Results show that encapsulation conditions especially the core-shell flow rates and shell wall formulation, influenced oil bead characteristics, core oil stability and retained phenolic content. Optical and scanning electron microscopy revealed that the 3 types of co-extruded oil beads were spherically shaped with the A-P beads having the largest bead size. All beads were physically and chemically robust, and remained intact after being treated in acidified water at pH 3 for 2 h. Storage trials at 20 and 38 degrees C for 30 or 60 days revealed the interplay between shell formulations and storage conditions on oil primary and secondary oxidation, hydrolytic rancidity and total phenolic content of the encapsulated canola oils. Quercetin added to the oil core was more effective than vitamin E or BHT in suppressing oil oxidation at 38 degrees C. High performance liquid chromatography analyses indicated different decomposition pathways for quercetin in these beads during storage. FT-IR studies confirmed the chemical composition and chemical stability of the 3 types of quercetin-containing oil beads. 1%A and A-P shells are both acceptable and comparable for preserving quercetin-containing canola oil, with A-P and 1%A being slightly better for 30 and 60 day storage periods, respectively. Thus, it is feasible and beneficial to deliver unsaturated oil and phenolic antioxidants in the form of pectin fibre-enhanced alginate microbeads. (C) 2013 Elsevier Ltd. All rights reserved.