Recovery And Kinetics Study Of Isoelectric Precipitation Of Sunflower Protein In A Tubular Precipitator

ABSTRACT

Oilseed sunflower is one of the major vegetable oil sources. The residue after the extraction of oil (defatted meal, DM) contains a substantial amount of nutritious protein which is recoverable by extraction and precipitation methods. For effective recovery of the solid proteins from the solids-liquid suspension, it is imperative to have large particles with a narrow spread in their size distribution and high solids concentration. In this research, up to 97 % w/w and 65 % w/w of the proteins in the laboratory and industrially defatted sunflower meals, respectively, were extracted using aqueous alkaline solutions at pH 10.0. Up to 84 % of these soluble proteins were recovered as solids when the pH was lowered from 10.0 to 4.0 (isoelecmc pH) using aqueous HCI acid. The amount of proteins recovered as solids decreased with decreasing concentrations of the acid. Three types of precipitator configuration were used in this study: the batch, mixed suspension mixed product removal (MSMPR), and the fxbular precipitators. Factors affecting the particle size distributions and the solids yield were studied. The batch precipitator was found to produce precipitates with high solids concentrations (yield), but small mean parricle sizes (< 10 pm) with narrow spread in the particle size dismbution (PSD). The MSMPR precipitator produced low solids yields and medium pamcle sizes (ca. 10 to 20 pm) with a wide spread in the PSD. High concentrations of the protein in the feed solution resulted in bimodal PSD. The tubular precipitator operating in turbulent flow regime produced precipitates with small particles and a narrow size distribution similar to the batch precipitator. In the laminar flow regime, the tubular precipitator produced large pamcles (aggzgates) which increased in size with increases in the mean residence time and protein concentration in the feed solution. These sizes increased from ca. 10 pm to ca. 40 pm..