Spray-drying microencapsulation of black quinoa bioactive extracts: process optimization and physicochemical properties for functional ingredient applications

Abstract This work explored the physicochemical composition, stability and encapsulation efficiency of bioactive compounds of the hydroalcoholic extracts of Black Quinua Collana. Physicochemical characterization indicated low moisture and water activity, stabilizing grain, and extract indicated enriched amounts of soluble solids and bioactives. A synergistic interaction between temperature and pH was indicated in response surface analysis to affect bioactive stability, with greater retention at 40oC and pH 4.5, and decreased stability at near-neutral pH. Betacyanins showed a high pH sensitivity relative to the betaxanthins that were broadly stable. The presence of phenolic antioxidants was affected by both pH and thermal stress with gallic acid showing the greatest impact of both pH and thermal stress whereas no significant effect of pH was observed on catechin stability. Optimized wall materials (3% gelatin:7% maltodextrin) combined with spray drying at 160o C yielded the greatest encapsulation efficiencies (>90 %) and produced spherical microcapsules with unimodal particle size distribution (~8.7 μm). Samples showed structural integrity by scanning electron microscopy, and the wall composition was polysaccharide-protein, with high carbon and oxygen content by EDX. Colorimetry showed that moderate temperatures led to the better preservation of pigments, as would be expected with that of betalains. Altogether, the results indicate that the stability of bioactives obtained by controlled extraction and microencapsulation ensures their improved functional properties, which can be used in nutraceuticals and functional food formulas.