Extraction of Protein from Walnut, "Shinano-Gurumi" (Juglans regia L.) and Properties of the Protein

Abstract

The effect of pH and NaCl concentration on the extraction of the protein from walnut, "Shinano-Gurumi" (Juglans regia L.) was examined; 98.7% of the total nitrogen in walnut was extracted with a 10% NaCl containing NaHCO₃-Na₂CO₃ buffer solution system (pH 11.0), and on a dry basis, about 87.6% of the isolated fraction was protein. It was least soluble at pH 7.0, but its solubility increased to 96 and 90% respectively, at pH 3.0 and 11.0. Glu, Arg, Asp were rich and Cys, Met, His were poor in its amino acid composition. The isolated protein was characterized using an acetic acid-urea polyacrylamide gel electrophoretic system and sodium dodecyl sulfate (SDS) polyacryiamide gel electrophoresis: three main bands A1, A2, and A3 were estimated to have molecular weights of 42, 000, 39, 000 and 25, 000 respectively, on SDS polyacrylamide gel electrophoretical pattern. The content of sulfhydryl and disulfide bond in the protein was higher than soybean and yeast proteins.