New insight for spent hops utilization: simultaneous extraction of protein and xanthohumol using deep eutectic solvents

Abstract

Agro-food by-products are a cheap source of bioactive and functional compounds that should be used via a biorefinery approach to produce a range of bio-based products. Spent hops (SH) are an important by-product of the brewing industry and are rich in valuable ingredients such as proteins and xanthohumol (XN). Considering the increasing demand for plant-based proteins and the broad spectrum of XN bioactivity, it is important to develop eco-friendly and cost-effective techniques to extract these components. In this work, a simple, one-pot, green method for the simultaneous extraction of proteins and XN from SH using deep eutectic solvents (DESs) was developed. Protein and XN-rich precipitates were obtained by adding water (antisolvent) to the DES extracts. To determine the XN content, the precipitates were extracted with methanol and the extracts were analyzed by HPLC. The presence of protein in the methanol-insoluble fractions was confirmed by techniques such NMR, IR, elemental analysis, and SDS-PAGE. The protein content varied between 40 and 64%, which was up to 87% higher than the protein content in the SH. This study demonstrates the potential use of SH and DESs to develop an environmentally friendly method to obtain protein and XN-rich products. Graphical abstract: [Figure not available: see fulltext.]