Production of leaf protein concentrate from ryegrass (Lolium perenne x multiflorum) and alfalfa (Medicago sativa subsp. sativa).: Comparison between heat coagulation/centrifugation and ultrafiltration

Juices from pressed green grass and alfalfa have a high protein content and are used for producing protein concentrates. Heat coagulation is the most-used method for this product category. An alternative method is ultrafiltration. which promises a product with a higher solubility. Both methods are carried out with two different raw materials. Alfalfa (Medicago sativa subsp. sativa) and ryegrass (Lolium perenne x multiflorum) were prepared under equal conditions to get a green juice. In an additional experiment, juice pressed from ensiled ryegrass was used as a feed for ultrafiltration with a very low cut off (1 kD). It was found that only a part of the crude protein, which can be recovered, is true protein. The crude protein recovery by ultrafiltration of ryegrass juice was 59% compared to 45% by heat coagulation. The rate of crude protein yield of alfalfa juice was 52% by ultrafiltration and 53% by heat coagulation and centrifugation. It was shown that protein degradation under ultrafiltration conditions plays an important role. During ultrafiltration of silage juice no selective crude protein retention was observed.