Harnessing the potential of green leaves : agricultural biomass as a source of sustainable food protein

Abstract: Demand for sustainable protein-rich food sources is currently increasing to meet the nutritional requirements of a growing population, while also considering climate challenges. Green leafy biomass (GLBM), in the form of side-streams and main crops, is a widely available protein source with potential food value. Extended use of GLBM, e.g. through a biorefinery process targeting leaf protein concentrates (LPCs), could add direct values, e.g. economic revenues from side-stream valorisation, or indirect values, e.g. reduced greenhouse gas emissions from higher resource utilisation. In this thesis, several types of GLBM were successfully subjected to an extraction protocol targeting water-soluble proteins, although the outcomes, e.g. yield, differed significantly between GLBM types. The major protein component in LPC was the enzyme RuBisCO. A pre-feasibility assessment revealed insufficient recovery rates on upscaling the process. To achieve economic viability, further process development is needed and additional compounds and products should be targeted. The use of LPCs in food applications is of interest due to their nutritional aspects, i.e. high protein content and good amino acid profile. Another area of interest is their potential as a functional ingredient, e.g. their foam stabilising ability, which was demonstrated for LPCs from several GLBM types in this thesis. Air-water interfacial properties, which can serve as an indicator of foam stabilising capacity, did not differ significantly between LPCs from the GLBM types evaluated. Further, no major differences in interfacial properties were observed between the LPCs and egg white. Green leafy biomass can be viewed as a valuable resource with great potential and extending the use of GLBM through LPC production could contribute to a more sustainable food production system.