Optimization of ultrasound assisted extraction of of goji berry (Lycium barbarum) fruits and evaluation of extracts' bioactivity

Abstract

Popularity of goji berry fruit extracts as functional ingredients is growing rapidly. “Green” aqueous extraction technologies are preferable to organic solvent-based processes as they improve the bioactivity and added value of these extracts. This work aimed at optimizing the ultrasound assisted aqueous extraction (UAE) of Lycium barbarum for both locally produced and imported fruits and comparing the bioactivity in relation to extraction conditions and origin of fruits, using a response surface model. The optimal solvent/extracted material ratio, extraction temperature, ultrasonic power, and extraction time were determined to achieve the following optimal quality/bioactivity indices: total solids, carbohydrates, phenolics, and antioxidant capacity based on IC-50 values of the DPPH method. Fruits of different origin had mostly similar optimal extraction conditions and antioxidant capacity but differed significantly in carbohydrate content, which was higher for locally produced fruits (1.1 ± g/L extract) compared to imported ones (0.89 ± g/L extract). Practical applications: In this study, the UAE process for goji berry extracts was successfully optimized using response surface methodology, and the most preferable conditions for optimal extraction performance and optimal bioactivity were determined. With regard to extraction yield, the optimal water/raw material ratio (33.9%), extraction temperature (32.02°C), ultrasonic power (30.95 w/cm2), and extraction time (32.03 min) were determined. Under optimal extraction conditions, locally produced fruits had no significant difference in extraction yield, and antioxidant capacity (IC50 values) compared to imported ones. However, locally produced fruits had significantly higher carbohydrate content and somewhat lower polyphenol content under optimal UAE conditions, showing that fruit origin may affect the composition of fruit extracts. These findings are a useful tool for producers of goji berry extracts to achieve an effective and economically viable extraction process as well as optimal composition and bioactivity in terms of antioxidant capacity, which are indeed important traits of these fruit extracts. © 2016 Wiley Periodicals, Inc.