Modification of the Sodium Hexametaphosphate Extraction‐Precipitation Technique of Rapeseed Protein Concentrate Preparation

Abstract

A previously reported method of preparing rapeseed protein concentrate (RC) involving 2% sodium hexametaphosphate (SHMP) was modified to reduce SHMP lost in the effluent, to produce a product with higher protein, lower phosphorous content and improved color close to that of rapeseed flour and promine D. Addition of 0.25% Na2S205 to the 0.25% SHMP extractant improved color but had little effect on flavor. Except for nitrogen solubility, whippaachieved the fust two objectives. Double washing of precipitate with 50% alcohol or precipitation in 15 or 30% alcohol yielded RC with color close to that of rapeseed flour and promine D. Addition of 0.25% NazS2Os to the 0.25% SHMP extractant improved color but had little effect on flavor. Except for nitrogen solubility, whippability and viscosity, the functional properties and chemical scores of the improved RC's were similar to the control RC (2% SHMP). ~~ ~ ~Grams nitrogen recovered per lOOg nitrogen in rapeseed flour Decrease in yield between after washing and drying was attributed t o losses during transfer of precipitate from centrifuge bottle to drying pans or bottles to weighing containers. Adhering solids in the containers were considered losses.

Preparation of Rapeseed Protein Isolate by Sodium Hexametaphosphate Extraction, Ultrafiltration, Diafiltration, and Ion‐Exchange

“…The nitrogen recovered as protein isolate accounted for 63.1% of that in the starting meal, similar to the best results (63%) reported by Thompson et al (1982). However, their starting material was a dehulled rapeseed flour, while we were using an undehulled meal in which approximately 10% of the nitrogen is bound to the hull.…”

“…All treatments yielded isolates with almost 90% protein which were free of glucosinolates, low in phytates, phosphorus and fiber, light in color, and bland in taste. The isolate had protein levels similar to the best product obtained by Thompson et al (1982) using SHMP, but it had a lower phytate and phosphorus content due to the effectiveness of the ion-exchange step. Furthermore, by decreasing the solution-to-resin ratio, which increases the relative ion-exchange capacity, the phytate and phosphorus levels of the isolate were decreased further.…”

Removal of phenolic compounds in the production of high-quality canola protein isolates

“…After these tsvo extractions, a nitrogen extractability as high as 97% was achieved. The process \vas modified and scaled up by the sarne group of researchers to produce a product with a protein recovery of 650h (Thompson et al, 1982).…”

Canola and Rapeseed

“…, 1988bTzengetal. , 1990,5.0-7.5% for the protein concentrates , and < 1.0-9.8% for the protein isolates depending on the method of protein isolation Tomell 1976a, 1976b;Liu et al 1982;Thompson et al 1982;Blaicher et al 1983;Cho 1984a, 1984b;Thompson 1987;. These values are generally higher than those reported for many legumes and other oilseeds (Cheryan 1980;Reddy et al 1982;Yoon et al 1983;Harland and Oberleas 1989).…”

“…Unfortunately, under this condition, the product is brown, even after extraction with alcohol, due to the large amount of phenolics that are coextracted with the proteins . Therefore, others Liu et al 1982;Thompson et al 1982) extracted the proteins with either 2.0 or 0.25% sodium hexametaphosphate at a milder pH of7, where PA also exhibits a low solubility while protein remains highly soluble. Following isoelectric precipitation and alcohol washing, a lighter-colored protein isolate was obtained with the PA content (1.26%) lower than that of the rapeseed flour (6.27%) although higher than that prepared with pH 11 extraction (0.04%).…”