Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2008
Publication Date: August 18, 2008
Citation: Bonnaillie, L., Tomasula, P.M. 2008. Whey protein fractionation using supercritical carbon dioxide [abstract]. 236TH ACS National Meeting Abstract. Technical Abstract: Sweet whey, a coproduct of the cheesemaking process, can be concentrated using ultrafiltration and ion-exchange to produce whey protein isolates (WPI). WPI contains approximately 32% alpha-lactalbumin (alpha-LA) and 61% beta-lactoglobulin (beta-LG), plus a small amount of minor whey proteins. While WPI is highly functional, various fractionation techniques have been developed to separate either the alpha-LA or beta-LG proteins from the rest of the WPI solution and exploit the individual physical, chemical and nutritional properties of these proteins. The fractionation techniques rely on salts, organic solvents and acids which contaminate the proteins and the waste streams. In an alternative process, injection of carbon dioxide (CO2) into water under supercritical conditions creates an aqueous acidic environment suitable for protein fractionation. In this environmentally friendly process, the CO2 is evolved upon release of pressure and may be recycled. The resulting products are free of contaminants. In this study, we demonstrated the use of supercritical CO2 (SCO2) to prepare enriched fractions of alpha-LA and beta-LG from WPI solutions through the acidic precipitation of alpha-LA and selective recovery of alpha-LA-enriched aggregates. Parallel studies were conducted using hydrochloric acid (HCl) solutions to elucidate the aggregation kinetics and behavior of alpha-LA versus four process parameters: protein concentration, temperature, pH and time, and to determine if the mechanism for HCl precipitation of alpha-LA is identical to that of SCO2. Process parameters were optimized to obtain both high aggregation efficiency and an optimal composition for the aggregate fraction. The optimally enriched fractions contained 62% alpha-LA (aggregate fraction) and 98% beta-LG (liquid fraction), and were obtained at pH 4 to 4.2 and 60°C, with a run-time greater than 30 minutes and a WPI solution concentration of 10 wt%. Anti-solvent effects of CO2, precipitation of the proteins induced by abrupt changes in the solvent properties of water due to excess CO2, were not observed. In this presentation, the quality of the protein fractions obtained to date as a function of HCl- and SCO2-processing will be discussed, as well as the challenges that remain for further utilization of the SCO2 technology.