Abstract
Goji (Lycium barbarum L.) leaves and fruits have been described as a valuable source of bioactive compounds with a great potential for the development of health-promoting formulations. The present study aimed to evaluate the potential of a sustainable process for the recovery of phenolic compounds from Goji leaves through a combination of aqueous extraction and membrane-based operations. Water was used as a safe, cheap, and non-hazardous extraction solvent, and parameters of extraction of dried Goji leaves were optimized in order to maximize the yield of polyphenols, total soluble solids (TSS), and total antioxidants simultaneously. The aqueous extract was clarified by ultrafiltration and then processed with three flat-sheet polyethersulphone (PES) membranes with molecular weight cut-off (MWCO) values in the range of 0.3–4.0 kDa, in order to remove sugar compounds from polyphenols and improve the antioxidant activity of the produced fractions. Among the selected membranes, a 1 kDa membrane exhibited the best performance in terms of purification of polyphenols from the clarified aqueous extract. The rejection by this membrane of TSS and total carbohydrates was in the range of 15.8–25.3%, and was decreased by increasing the volume reduction factor (VRF). On the other hand, the retention values for total polyphenols and total antioxidant activity (TAA) were in the range of 73–80%, and were increased by increasing the VRF.
Highlights
Lycium barbarum L., commonly known as Goji, has long been used in traditional Chinese medicine, and is increasingly becoming popular as a so-called “superfruit” in Europe and North America [1]
The aqueous extract was ultrafiltered using a laboratory pilot unit equipped with a capillary polysulphone (PS) membrane supplied by China Blue Star Membrane Technology Co., Ltd. (Beijing, China) having a nominal molecular weight cut-off (MWCO) of 100 kDa and an effective membrane area of 0.16 m2
Differences were considered to be significant at p < 0.05
Summary
Lycium barbarum L., commonly known as Goji, has long been used in traditional Chinese medicine, and is increasingly becoming popular as a so-called “superfruit” in Europe and North America [1]. The challenge here is the development of suitable downstream processing techniques, allowing for the recovery of these compounds from their original sources without affecting their structure and function, which translates into their bioactivity In this context, membrane processes offer interesting sustainable solutions to this problem, since they can operate in mild operating conditions of temperature and pressure, without the use of chemical agents or solvents, avoiding product contamination and preserving the biological activity of target compounds [17,18]. Pressure-driven membrane processes, such as ultrafiltration (UF) and nanofiltration (NF) have been successfully used in the fractionation and concentration of biologically active compounds, including polyphenols, from undervalued bioresources and natural products [21,22]. The performance of selected membranes was compared in terms of productivity (permeate fluxes), fouling index, cleaning efficiency, and selectivity towards target compounds
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