Partners SSICA, University of Parma and IRIS investigated three different extraction methods: An environmentally friendly aqueous extraction (EFAE), an ultra-sound assisted approach (UAE) and an enzyme-assisted hydrolysis (EAE).
The environmentally friendly aqueous extraction, developed by SSICA, applies mild conditions at room temperature. The extracts from chickpeas and fungi have a protein content of around 65 % and 58 %, respectively. The simplicity of the method with little technical interventions make it a prime candidate for up-scaling.
IRIS investigated how protein extraction using alkaline solutions could benefit from the use of ultrasonic power. Ultrasound assisted extraction (UAE) is a non-classical extraction method that can enhance the extraction efficacy by promoting the rupture of the cell wall of the plant material due to the influence of acoustic cavitation. This facilitates the mass transport from the plant material to the solvent. We tested the extraction efficiency at different set points for acoustic energy and temperature of the process. Roughly speaking, the harsher the conditions, the better the extraction efficiency. Yet this also affects the protein quality. A particular challenge was to balance the yield of proteins with their quality and integrity. Initial issues with a relatively high degree of amino acid racemization could be controlled by adaptation of reaction conditions. With an optimized protocol we were able to recover 20 % of the proteins from coffee green beans.
A different approach to enhance protein extraction was pursued by UNIPR: the use of enzymes. Other than ultrasound, they facilitate the process by biochemical reactions instead of physical interaction. Essentially the extraction is accelerated by partial digestion of the protein. The challenge here is to stop the hydrolysis at an appropriate stage and to remove the enzyme from the final protein solution. For our purpose we selected papain or alcalase. The extraction efficiencies observed on the coffee feedstocks and different fungi ranged between 20 and 40 %, which is higher than for the UAE. However, the method yields a mix of peptides, i.e. proteins of shorter length and lower molecular weight.
Plant-based proteins 1