Glycine betaine enhanced foam separation for recovering and enriching protein from the crude extract of perilla seed meal

The utilization of agro-food waste into protein products is an alternative solution for global protein shortage and waste management. Perilla ( Perilla frutescens L.) seed meal (PSM) is abundant and protein-rich by-products from the oilseed industry. To achieve the industrial production of valuable PSM protein (PSMP), a two-stage foam separation with a low cost and a high efficiency was developed to fractionate the high-concentration PSMP (1.3 times its critical micelle concentration (CMC)) from its crude extract. In the first-stage, glycine betaine (GB), a naturally occurring osmolyte, was used as a green enhancer for the recovery of PSMP. The result of SEM, FTIR, UV–vis and fluorescence spectra demonstrated that GB engaged in cation-π interactions with aromatic residues of PSMP, which made the protein structure unfold and enabled its hydrophobic groups of PSMP to be more exposed. These factors, plus protein aggregation, were responsible for the enhanced interfacial adsorption of PSMP. Its recovery percentage with 0.3 g/L GB (pH 7.0) increased by 52.9% compared to that without GB. Furthermore, an internal component of regular-hexagon hollow prismoid (RHP) was also designed to intensify the foam drainage and raise PSMP enrichment to 7.1 ± 0.3. In the second-stage, PSMP could be further recovered and its total recovery percentage reached 94.5 ± 4.7%. After foam separation, the amino acid composition of PSMP was analyzed by SDS-PAGE and HPLC–UV and its functional properties was also evaluated. These results provide a new insight into enhancing the protein separation from agro-food waste.