Impact of the extraction method on the composition and solubility of leaf protein concentrates from perennial ryegrass (Lolium perenne L.)

There is an increasing demand for developing new sources of proteins, and plants are considered the preferred alternative to animal proteins. In particular, green leaves are a source of RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase). This work assessed perennial ryegrass as a source of soluble proteins using mild treatments to preserve their functional properties. Two different extraction methods were compared, differing in the presence or abscence of a heating step (at 50 °C for 30 min) aimed to improve the removal of chloroplast material. The method that included the heating step resulted in a protein concentrate with high solubility (>90% at pH 7), and higher concentration of phenolic compounds. On the other hand, avoiding the heating step resulted in a higher extraction yield, but the residual chloroplast material affected the solubility of the final powder (>60% at pH 7). The protein extracts obtained by both methods consisted mainly of RuBisCO and presented a balanced amino acid profile covering the FAO (2011) recommendations for all the essential amino acids. Therefore, perennial ryegrass showed potential to become an alternative source of proteins for food applications with good nutritional value, whose phenolic compound, chlorophyll content and solubility was strongly dependent on the extraction process.