The paper is concerned with the isolation of food protein from clover and lucern leaves in a soluble nondenaturated state. The protein concentrates are white or light-cream-coloured and contain 74 and 82% of protein, 11.5 and 7.9% of carbohydrates, and 800 and 1OOOmg calcium/kg, respectively. The concentrates are water-soluble at pH over 6.0 and include fractions 1 and 2 of leaf protein. The content of essential amino acids in the clover and lucern proteins is 42-43'1/, and the protein in vitro digestibility is as high as 90% relative to the major milk-casein one.
Green plant leaves represent high-efficient producers of food protein whose biological value exceeds that of soy protein and is not inferior to that of milk proteins [l, 21.
Usually food protein is obtained from green plant leaves in the following stages : powdering the plant pulp, juicing (or protem extraction), removal of nonfood chloroplast particles from the juice, isolation and purification of the protein. The principal, techniques for the preparative laboratory isolation of leaf protein are well known [3,4]. However, the processes for producing food protein from leaves, having high functional properties, have not been investigated as yet. This may be due to a series of undesirable physico-chemical processes occurring in the powdering of the green plant leaf pulp and affecting the composition, properties and food usefulness of the proteins obtained. Moreover, this calls for a search for novel methods to isolate protein without loss of its solubility and food value.
Studies into the thermodynamic compatibility and complexing of milk proteins and anionic polysaccharides, that have been under way for the last few years, indicate that the process of phase separation of the systems water-protein-polysaccharide may involve two types of protein concentration processes [5,6]. First, it is the so called membraneless osmosis based on the thermodynamic incompatibility of proteins and polysaccharides, and second - on the formation of insoluble protein-polysaccharide complexes. As compared with spray drying and vacuum evaporation, the processes of polysaccharide-assisted protein concentration do not lead to protein denaturation and loss of its solubility, on the one hand, and afford high productivity and energy consumption, on the other [6,7]. The processes of phase separation in the systems water-leaf protein-polysaccharide are obviously advantageous both to the flocculation of the chloroplast particles and protein isolation. Therefore the purpose of this work is to discuss the possibility of using polysaccharides for the production of food leaf protein with a high solubility and favourable functional properties.
Methods
In our studies we used a green biomass of lucern (Medicago sativa L.) and red clover (Trifoliumprarense L.) obtained from the test field of the Agricultural Research Institute for the USSR NON-Black Central Regions for one cutting from 8 a. m. at the stage of plant budding.