Functional properties of soybean and lupin protein concentrates produced by ultrafiltration‐diafiltration

Abstract

Ultrafiltration followed by diafiltration (UF-DF) was evaluated for the production of protein products from partially defatted soybean meal or undefatted lupin (Lupinus albus L.2043N) meal. This study determined the effects of UF-DF on functional properties of the extracted proteins and compared the results with those of protein prepared by acid-precipitation (AP). UF-DF produced only protein concentrates (73% crude protein, dry basis, db), while AP produced protein isolates (about 90% crude protein, db). Soybean protein produced by UF-DF showed markedly higher values for solubilities up to pH 7.0, surface hydrophobicity index, emulsion activity index, and foaming capacity than did the AP soybean protein. UF-DF soy protein was also the most heat-stable among all protein samples tested. With lupin proteins, only the surface hydrophobicity and emulsion activity indices were significantly improved by using UF-DF. UF-DF generally had no adverse effects on, and in most cases even improved, the functional properties of soy protein concentrate produced by this method. UF-DF did not produce a comparable improvement in functional properties of lupin proteins as it did for soybean protein.The Clean Air Act, which limits emissions of volatile organic compounds and other hazardous air pollutants, has spurred the utilization of mechanical extraction processes in the oilseed industry (1). One such solvent-free process is extrusion-expelling (E-E), a simple and relatively inexpensive operation (2) that has produced soybean oil of such quality that only minimal refining will be required (3). The resulting meal has higher oil content than what is found in meal produced from traditional solvent extraction (2), but E-E meal is considered as a higher energy source for livestock feed (1). Because E-E does not use desolventizing and drying, the meal is also presumed to have better functional properties, which would make it possible to use E-E meal for the production of the higher-value flours, concentrates, or isolates. Heywood et al. (4) prepared low-fat soy flours from E-E meal and found them to possess good solubilities (at pH values less than and greater than 4), emulsifying and foaming properties, and water-and fat-binding capacities. No study has yet been reported on the preparation and quality of concentrates or isolates from E-E meal.The present study explores ultrafiltration (UF) as a means of producing protein concentrates or isolates from E-E soybean meal. UF is a pressure-driven membrane process that has gained wide acceptance in protein bioseparations (5). It has a broad variety of applications, but it is used mainly for concentration, desalting, clarification, and fractionation (5). Sessa (6) recently produced peroxidase and Bowman-Birk inhibitor concentrates from soybean hulls by using UF, followed by discontinuous diafiltration (DF), a membrane-based method that removes low M.W. solutes such as salts while continuously replacing the solvent lost with the permeate (5). Both peroxidase and Bowman-Birk inhibitor are valua...

Extraction, Composition and Functional Properties of Pennycress (Thlaspi arvense L.) Press Cake Protein

“…These results with press cake protein extracts are similar to those we observed for pennycress seed meal protein isolates [7]. Foaming properties of the press cake protein extracts also compared favorably with values we reported for soybean protein isolate (131 ml and 95 % remaining foam [33]). In contrast, previous research on canola protein isolate produced by methods similar to ours found that the foaming capacity and stability of the isolates were inferior to the foaming properties of its meal and also declined as the pH increased from 10 to 12 [27,34,35].…”

Extraction and Functional Properties of Non‐Zein Proteins in Corn Germ from Wet‐Milling

“…1% b-mercaptoethanol, which had even higher oil content (15% db, Table 1), produced the most stable foam. Its 93% remaining foam almost equaled the foam stability we observed for soybean protein concentrate [30]. We believe that this enhanced foam stability was the result of SDS co-extracted with the protein and not removed thoroughly by dialysis, as was mentioned previously.…”

“…At pH 7, protein from finished germ had a better emulsifying capacity than wet germ protein, as shown by greater EAI values ( Table 2). All the corn germ protein extracts, however, had EAI values that exceeded the 56 m 2 /g protein we determined for soybean protein [30]. At pH 10, all the corn germ protein extracts had EAI values that were significantly greater than those observed at pH 7 ( Table 2).…”

Effects of cooking and screw‐pressing on functional properties of Cuphea PSR23 seed proteins

“…Higher EAI values indicate better emulsifying capacity. The EAI value at pH 10 for unprocessed Cuphea proteins (Table 2) was more than twice that of low-fat soy flour determined by Heywood et al (18), but 25 and 50% less than the EAI for acid-precipitated lupin and soybean proteins, respectively, reported by HojillaEvangelista et al (19). Heating the flaked seeds (in the conditioner and screw press) increased EAI values by at least 40% (CF75) and as much as 133% (CF120).…”

“…The ESI value for unprocessed Cuphea seed protein ( Table 2) was double that observed for acid-precipitated soybean protein (19), which implied that emulsions formed by Cuphea protein were more stable than those formed by soybean protein.…”