Understanding differences in protein fractionation from conventional crops, and herbaceous and aquatic biomass - Consequences for industrial use

Background: Alternative protein sources are constantly explored to secure the future food and protein demand. Among these sources, biomasses originating from algae, seaweed or leaves receive lots of attention. However, when the yields and purities of protein extracted from these sources are compared to the corresponding data for protein crops such as soy, lupine and pulses, much lower yields are reported for alternative biomasses. Scope and approach: In this overview paper, we analyse whether this difference is due to lack of scientific insight and technology or that more fundamental reasons are behind the variations in the extraction behaviour. For this purpose, we prepared a description of herbaceous and aquatic biomasses (denoted as green biomass/sources) and their protein extraction practices, final products, and common trends and challenges. The discussion continues with a general comparison to protein crops and the implications for future research. Key findings and conclusions: Overviewing the state of the art, we tend to conclude that physiological and biochemical factors hinder efficient fractionation of green sources. Such factors include cell architecture and high interconnection between cell components; and biochemical differences, in particular the type of proteins present. These fundamental differences imply that green sources should be explored in a different manner, with higher emphasis on the interesting functional properties of enriched fractions and less on their purity. This approach is further encouraged by highlighting examples where the intricate structures found in green biomass can give rise to positive effects (e.g. health, food structure) when integrally applied in food products.