Opportunities for extraction of protein from alfalfa

Authors: Heuschele, Deborah - Jo

Submitted to: Proceedings of the World Alfalfa Congress
Publication Type: Proceedings
Publication Acceptance Date: 11/14/2022
Publication Date: 11/17/2022
Citation: Heuschele, D.J. 2022. Opportunities for extraction of protein from alfalfa. Proceedings of the World Alfalfa Congress. November 14-17, 2022. San Diego, California.

Interpretive Summary:

Technical Abstract: There is a growing demand for protein due to increased population and affluent countries demanding protein rich foods. The majority of plant-based proteins on the market are storage proteins extracted from seeds. These types of proteins are stable prior to extraction and easily extracted with current technologies. However, the most abundant type of plant-based protein resides in plant leaves and stems as the functional protein RuBisCo. When this and other functional proteins are extracted and condensed, they form leaf protein concentrate (LPC). Current methods of LPC extraction include either pulping or juicing the material to release the proteins and then either coagulation, acidification, fermentation, or ultrafiltration to concentrate the soluble proteins. Recovered LPC yields in alfalfa range from 15 to 43% of the original amount of protein found in the plant. These yields are higher than other leafy plants making alfalfa a prime candidate for cultivation for LPC. Unfortunately, alfalfa contains high levels of endogenous proteases which could impact the LPC recovery rates. Proteases breakdown proteins into small subgroups that change protein solubility and the ability to be filtered at a specific size. Our lab is testing how harvest management changes protein size and extraction yields. Three commercial varieties were harvested then either immediately dried, immediately juiced, or air dried after cutting. Crude protein extractions were visualized on an acrylamide gel compared with a molecular weight marker standard. The juiced samples had the highest concentration of bands approximately 55 kda in size, supporting previous studies that indication most of the proteins within alfalfa leaf tissue are RuBisCo; its subunits are approximately 55 kda in size. Immediately dried alfalfa had protein bands at 55kda and smaller with some protein smearing. While aired dried samples showed no protein bands, with extensive protein smearing, suggesting that little or no proteins remained intact. To further investigate harvest impacts on protein stability we tested seven different harvest including freeze drying and spray drying alfalfa for protein extraction. Our experiments conclude that the harvest method of alfalfa for protein is important for the overall extraction yield.