PROPERTIES OF AQUEOUS-ALCOHOL-WASHED PROTEIN CONCENTRATES PREPARED FROM AIR-CLASSIFIED PEA PROTEIN AND OTHER AIR-CLASSIFIED PULSE PROTEIN FRACTIONS

Pea protein concentrates were prepared from air-classified pea protein by aqueous-alcohol (ethanol or isopropanol) washing. Response surface methodology (Box Behnken design) was used to create mathematical models to explain quantitatively the relationship between treatment combinations (aqueous alcohol concentration, extraction temperature, extraction time) on the protein contents and yields of the pea protein concentrates. Also studied were the effects of these treatments on the starch, fat, lipid, ash and oligosaccharide contents and the functionality (water hydration capacity (WHC), oil hydration capacity (OHC), emulsion activity (EA), emulsion stability (ES), foaming capacity (FC), foam stability (FS) and nitrogen solubility index (NSI) of the concentrates.\nThe protein contents of concentrates decreased as the concentration of alcohol increased, whereas yield increased. Time and temperature were found to have no significant effect on protein content or yield. The protein contents and yields of aqueous-ethanol and isopropanol washed concentrates ranged from 68.2-72.1%, 66.4-76.1% 66.6-73.1% and 63.9-76.4%, respectively. Optimal conditions for protein content were identified as 52% aqueous-ethanol, 32°C, 12-minute extraction time or 55% aqueous-isopropanol, 50°C, 11-minute extraction time. Optimal conditions for yield were identified as 65% aqueous-ethanol, 40°C, 11-minute extraction time or 70% aqueous-isopropanol, 44°C, 10-minute extraction time. All aqueous-alcohol-washed concentrates were true protein concentrates (protein concentration >65% on a dry weight basis) and were higher in protein and starch and lower in lipid and raffinose-family oligosaccharides in comparison to the starting material, air-classified pea protein.\nIn general, the aqueous-alcohol-washed concentrates exhibited higher functionality values compared to the starting material, and WHC, OHC, EA, ES, FC and FS were similar for corresponding concentrates prepared using aqueous-ethanol or aqueous-isopropanol. In a few instances, aqueous-ethanol and aqueous-isopropanol had differential effects on ES, FC and/or FS. NSI was affected negatively by all treatments. All aqueous-alcohol-washed concentrates were lighter in colour and more green (less red) and more blue (less yellow) than the starting material. The functionality of aqueous-alcohol-washed concentrates was similar in most respects to that of one or both of the commercial soy concentrates analyzed. \nThe optimal conditions identified for protein and yield of aqueous-alcohol-washed pea concentrates were used in the preparation of concentrates from air-classified pea, fababean, lentil and navy bean protein fractions. Only products prepared from air-classified pea and fababean protein contained over 65% protein (dry weight basis) and could be classified as true protein concentrates, due to the lower protein contents of the lentil and navy bean air-classified protein fractions. The effects of aqueous-ethanol washing on the composition and functionality of products prepared from fababean, lentil and navy bean were similar to those observed previously for aqueous-alcohol-washed pea protein concentrates. \nThe aqueous-ethanol extracts obtained from preparation of protein concentrates from air-classified pea protein at conditions identified as optimal for protein content or yield were analyzed for their composition. The extracts were similar in composition and contained lipid, protein and oligosaccharide components. Stachyose was the most abundant oligosaccharide, and raffinose the least abundant. The protein constituents of the extracts were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions. The starting material, concentrates and extracts contained proteins in the molecular mass range of 10-95 kDa, 17-95 kDa and 10-20 kDa, respectively. The concentrates were depleted in lower molecular mass components; these components were predominant in the extracts.\nFat was extracted from pea and chickpea flours using either hexane or 70%-aqueous-ethanol prior to fine grinding and air classification to determine the effects of fat removal on the yield and composition of air-classified fractions. Hexane was the more effective solvent for fat removal. For both pea and chickpea, extraction of fat prior to air classification reduced the yield of the fine (protein-enriched) fraction and increased the protein content of both the coarse (starch-rich) and fine fractions. For chickpea, air classification was much more effective in separating starch and protein when fat-reduced flours were employed.\nA product prepared by Agriculture and Agri-Food Canada from air-classified pea protein by reflux extraction with 80%-aqueous-ethanol was analyzed for its composition and functionality. The reflux-extracted product was similar in composition to aqueous-ethanol-washed pea concentrates and commercial concentrates from soybean, with the exception of its lower protein and higher oligosaccharide contents. The reflux-extracted product was similar in functionality to aqueous-ethanol-washed concentrates, with the exception of its lower NSI.

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.