Supercritical Fluid CO2 Extraction and Microcapsule Preparation of Lycium barbarum Residue Oil Rich in Zeaxanthin Dipalmitate

Abstract

The scope of this investigation aimed at obtaining and stabilizing bioactive products derived from Lycium barbarum seeds and peels, which were the byproducts in the processing of fruit juice. Zeaxanthin dipalmitate is a major carotenoid, comprising approximately 80% of the total carotenoid content in the seeds and peels. The method of obtainment was supercritical fluid CO2 extraction, studying different parameters that affect the oil yield and content of zeaxanthin dipalmitate. The optimized protocol to enact successful supercritical fluid CO2 extraction included optimum extraction pressure of 250 bar, temperature at 60 °C over a time span of 2.0 h, and a CO2 flow of 30 g/min, together with the use of a cosolvent (2% ethanol). The yields of oil and zeaxanthin dipalmitate under these optimal conditions were 17 g/100 g and 0.08 g/100 g, respectively. The unsaturated fatty acids were primarily linoleic acid (C18:2), oleic acid (C18:1), and γ-linolenic acid (C18:3), with their contents being as high as 91.85 ± 0.27% of the total fatty acids. The extract was a red-colored oil that was consequently microencapsulated through spray-drying with octenylsuccinate starch, gum arabic, and maltodextrin (13.5:7.5:3, w/w) as wall materials to circumvent lipid disintegration during storage and add to fruit juice in a dissolved form. The mass ratio of core material and wall material was 4:1. These materials exhibited the highest microencapsulation efficiency (92.83 ± 0.13%), with a moisture content of 1.98 ± 0.05% and solubility of 66.22 ± 0.24%. The peroxide content level within the microencapsulated zeaxanthin dipalmitate-rich oil remained at one part per eight in comparison to the unencapsulated oil, following fast-tracked oxidation at 60 °C for 6 weeks. This indicated the potential oxidation stability properties of microcapsule powders. Consequently, this microencapsulated powder has good prospects for development, and can be utilized for a vast spectrum of consumer health and beauty products.