Fractionation of proteins from alfalfa juice at demonstration scale: Effects of temperature and centrifugation strategies on removal of green protein and recovery of the soluble white protein fraction
Natália Hachow Motta dos Passos, Morten Ambye‐Jensen
Abstract
Given the growing global demand for protein, alfalfa (Medicago sativa) has emerged as a promising alternative protein source for both animal feed and human nutrition due to its high protein content and nutritional value. This study investigated the fractionation of proteins in freshly pressed alfalfa juice into green and white fractions, with focus on optimizing the recovery of the white protein fraction, which holds significant potential for various food applications. Two sets of demonstration-scale experiments were conducted to evaluate the impact of temperature and centrifugation techniques on the fractionation process. The goal was to achieve the optimal coagulation and removal of the green fraction while concurrently enhancing the yield of the white protein fraction. The first set of experiments explored heat treatment at four different temperatures (50 °C, 55 °C, 60 °C, and 65 °C), followed by decanter centrifugation. Optimal coagulation of the green fraction with higher white protein fraction yield was observed at 55 °C. In the second set of experiments, a constant temperature was maintained (55 °C) while testing three different separation scenarios. A two-stage centrifugation approach employing a decanter and a disc-bowl high-speed centrifuges proved most effective, removing 74 % of the coagulated green fraction and preserving over 80 % of the white fraction in the residual juice after heat treatment. Complete removal of the green fraction was not achieved, and an additional microfiltration step was introduced to clarify the residual juice. Microfiltration retained up to 50 % of the white protein, resulting in a significant reduction in the overall recovery yield. The results indicate that achieving high recovery yields of soluble white protein remains a challenge and requires further optimization of the fractionation process.