Isolation of Rapeseed Protein Using Sodium Hexametaphosphate

Abstract

The suitable conditions for the extraction and precipitation of proteins from rapeseed flour (RF) using sodium hexametaphosphate (SHMP) were determined. Rapeseed protein isolate (RI) was then prepared and analyzed for chemical composition, biological value, color and yield.The highest nitrogen yield was obtained when RF was double extracted with 2% SHMP at pH 7.0, first with a RF to solvent ratio of 1: 10 and second with a ratio of 1:6 at 25°C for 30 min. The maximum precipitation of the extracted nitrogen was observed in the extract diluted with an equal volume of distilled water and adjusted to pH 2.5.The RI contained on dry basis, 72.6% protein (N × 6.25), 12.2% ash, 0.7% crude fiber, 7.6% nitrogen free extract, 3.21% phosphorus, trace amounts of glucosinolate and no myrosinase activity. Its PER was equal to that of cheese whey protein concentrate and greater than that of casein. RI was yellow at pH 2.5 and tan at pH 7.0. Ether extraction lightened the color of the neutralized RI. Thirty-four percent total solids yield and 53% protein yield were observed in the preparation of RI.