Recovery of bioactive compounds from artichoke brines by nanofiltration

The health-protective potential of artichoke, especially in terms of hepatoprotective, anticarcinogenic and hypocholesterolemic activity is widely recognized. Artichokes exhibit a high antioxidant capacity which can be attributed to high levels of phenolic compounds with a wide range of caffeoylquinic acid derivatives (with chlorogenic acid as the most important of these derivatives) and flavonoids such as apigenin-7-O-glucoside and luteolin. The production of preserved artichokes is based on the use of acidulated brines at pH values lower than 4.6 in order to limit the growth of Clostridium botulinum and make possible a pasteurization treatment at temperatures lower than 100°C to obtain the microbiological stability. However, the production of acidulated brines represents a serious environmental problem for the processing industry that must withstand high treatment costs and disposal. One of the main objectives for the artichoke industrial exploitation is to identify suitable processes and protocols to obtain phenolic-rich extracts from artichoke byproducts. In this work a membrane-based process for the fractionation of artichoke brines was investigated in order to separate flavonoids and caffeoylquinic acids from salt compounds. Therefore, the performance of different spiral-wound nanofiltration (NF) membranes in the treatment of clarified artichoke brines was evaluated in terms of productivity and selectivity towards bioactive compounds in selected operating conditions. Membranes with different polymeric material (polyethersulphone, polyammide) and molecular weight cut-off (MWCO) (from 200 to 1000 Da) were tested. NF membranes of 200 Da produced better results in terms of recovery and concentration of compounds of interest. A better separation of salt compounds from caffeoylquinic acid derivatives was reached by using Filmtec-Dow NF 200 and Desal DL membranes. For these membranes a low rejection towards dry residue (between 14 and 18%) was observed, while rejections towards total caffeoylquinic acids, flavonoids and cynarin were higher than 92%. According to the obtained results the NF permeate, enriched in salt compounds, can be reused in the working cycle for the preparation of new acidulated brines through the adjustment of the standard salt concentration; the concentrated stream, enriched in phenolic compounds, is a good source of possible ingredients to functionalize foodstuffs.