Studies of the proteins and the polyphenols of sunflower seed (Helianthus Annuus)

Abstract

Studies of the distribution of nitrogen, of conditions affecting its extraction and of the isolation, fractionation and amino acid composition of the soluble proteins of sunflower seed (Armavirec variety) have been reported. The effects of polyphenols --chlorogenic and caffeic acids --and of quinic acid reported to be present in the sunflower seed on the pH-solubility profile of sunflower and soybean proteins, on the production of color in the presence of protein at various pH levels and on the activity of trypsin and pepsin have been studied. A simple method for the preparation of colorless sunflower protein isolate has been developed. On the basis of the classical Osborne method the nitrogen of sunflower seed is distributed as follows: albumin (22%), globulin (ca. 55%), prolamine (1%), glutelin (17%), insoluble nitrogen (ca. 3.5%), and the non-protein-nitrogen (ca. 1.5%). Studies of the distribution of amino acids in water, salt and alkali soluble protein revealed that albumin fraction has a higher content of lysine, glycine and methionine and a lower content of phenylalanine than globulin and glutelin. Experimental variables such as pH, temperature and the types and concentration of salts used, have marked effects on the extractibility of the sunflower seed proteins. By ammonium sulfate precipitation, two water soluble and two salt soluble proteins were obtained. Ultracentrifugal and disc gel electrophoretic studies showed that the salt soluble proteins each contained one major and one minor component; the water soluble proteins, on the other hand, showed considerable heterogeneity. Amino acid compositions of one salt soluble and two water soluble proteins have been reported.