Use of oscillatory flow reactors for the optimised extraction of proteins from side and residual streams in the food industry

Food production by-products such as brewers¿ spent grain (BSG) and oil press cake contain valuable bioactive compounds, particularly proteins, that are often underutilized and primarily used as animal feed. Enhancing their recovery is essential for reducing food waste and supporting a transition towards a more sustainable and circular agri-food system in the context of global challenges. This study investigates the continuous extraction of proteins from BSG using an oscillatory flow reactor (OFR), focusing on the optimisation of key process parameters, including solid loading (SL) and residence time, with respect to yield, purity, productivity, and space-time yield. The results demonstrate that degrees of extraction of 30 ¿ 78 %, and yields of protein product from 11 ¿ 54 %, with average protein contents of 63 %, can be achieved. Optimal operating conditions were identified at a solid loading of 8 ¿ 9 % and a residence time of 30 minutes, representing a compromise between performance indicators. In addition, the biogas potential of the extraction residues was assessed as a subsequent step and shows promising. Furthermore, initial steps towards process scale-up were investigated. In the trial batch-experiment, comparable degrees of extractions (50 ¿ 80 %) were achieved, indicating promising potential for industrial application. However, further optimisation and stabilisation of reactor operation are required to ensure reliable continuous processing at larger scales.