Dry fractionation for sustainable production of plant protein concentrates

The global demand for protein-rich foods is expected to double in the coming decades due to the increasing prosperity and world population. To keep up with the demand, the transition from an animal to a plant-based protein supply is desirable from long-term economic and environmental perspectives. In particular, legumes such as pea and lupine are of interest due to their nutritional profile and high protein content. Legume proteins are commonly purified by wet fractionation, which consumes large amount of water and energy and alters the native functionality of the proteins. Therefore, this thesis describes a sustainable, dry fractionation method for legumes to obtain functional protein-enriched fractions. Firstly, experiments have been performed to increase understanding of both the material properties of legume seeds and of the process conditions relevant to dry fractionation. Dedicated milling settings were selected for starch-rich and oil-rich legumes based on legume morphology. Milling settings were estimated based on starch granule size in starch-rich legumes, while coarse milling provided better results for oil-rich legumes. Separation of the protein bodies from other cellular components was established by air classification, which consumed ten times less energy and 50 litre water per kg protein less compared to conventional wet fractionation. Secondly, the functionality of the fractions was analysed. The dry-enriched protein fractions provided higher solubility than conventionally produced fractions, making them suitable for high protein drinks. Moreover, pea fractions could also be gelatinized which opens opportunities for preparing solid protein foods such as meat replacers. In conclusion, this thesis contributes to the awareness that the food industry could exploit a more sustainable dry fractionation technique to obtain functional protein fractions rather than focussing on wet extraction of relative pure protein ingredients.