Simultaneous and sequential combination of techniques for the sustainable and extensive extraction of proteins and polyphenols from malt rootlets

The emergence of tecnhiques such as microwave-assisted extraction (MAE), enzyme-assisted extraction (EAE), ultrasounds-assisted extraction (UAE), and pressurized liquid extraction (PLE) has brough many benefits but their single use does not guarantee the hollistic extraction of target compounds from complex samples. Taking into account their different principles and that one technique may favour the extraction of certain compounds over others, this work proposes the combination of these techniques for improving extraction yields in the recovery of proteins, as example of large molecule, and phenolic compounds, as example of small molecule, from a recalcitrant sample. No single extraction technique recovered all proteins or phenolic compounds, even after a proper optimization. Among them, PLE was the most advantageous, enabling the extraction of 67 % proteins and 1.20 g gallic acid equivalent (GAE)/100 g sample. Analysis of samples by scanning electron microscopy (SEM) and separation of extracts by reversed-phase high performance liquid chromatography (RP-HPLC) and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that PLE showed the most distinct efficiency among EAE, MAE, and UAE, whereas the latter three exhibited more similar results. Based in these results, ten different combinations (sequential and/or simultaneous) of these techniques were proposed. PLE in combination with another technique showed a great potential for the extraction of both large and small molecules. Particularly, the combination of EAE and PLE recovered 100 % of proteins and more than three times the phenolic compounds extracted by other methods reported in the literature, even revealing significant synergistic effects.