Abstract: A comparative investigation of the effectiveness of three extraction methods (heating in an acidic environment, alkalization and fermentation) for alfalfa leaf protein  was studied based on extraction yield, nitrogen content, solubility, foaming capacity, foam stability, emulsifying capacity, emulsion stability, water-holding capacity, oil-binding capacity and scanning electron microscopic (SEM) observation. The results showed that the extraction rate and nitrogen content of alfalfa leaf protein from fermentation was 14.9% and 45.08%, respectively, which was significantly higher than those from other two methods. The foaming capacity, water-holding capacity and oil-binding capacity of alfalfa leaf protein obtained from alkalization were 200%, 5.40% and 5.31%, respectively, which were better than those obtained from other two methods. The alfalfa leaf protein obtained from fermentation showed better solubility, emulsifying capacity and emulsion stability, which were 80.53%, 78.60% and 20.65%, respectively. The alfalfa leaf protein prepared by alkalization displayed a loose damaged structure as observed under SEM. The surface structure of the alfalfa leaf protein prepared by other two methods was compact and consecutively intact. Furthermore, fermentation had degrading effect on alfalfa leaf protein. Therefore, different preparation processes can result in differences in the extraction rate, nitrogen content, functional properties of alfalfa leaf protein.

Key words: alfalfa, leaf protein, extraction method, functional properties, characterization