ARS | Publication request: Supercritical carbon dioxide fractionation of whey protein isolate for new food-grade ingredients

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 10, 2009
Publication Date: June 9, 2009
Citation: Bonnaillie, L., Tomasula, P.M. 2009. Supercritical carbon dioxide fractionation of whey protein isolate for new food-grade ingredients [abstract]. IFT '09 Annual Meeting & Food Expo. Paper No. 251:14.

Technical Abstract: A new, environmentally benign whey protein fractionation process was developed using supercritical CO2 (SCO2) as an acid aggregating agent to separate a-lactalbumin (a-LA) aggregates from soluble beta-lactoglobulin (beta-LG) protein in concentrated whey protein isolate (WPI) solutions. The process enables fractionation of commercial WPI, containing approximately 60wt.% beta-LG and 30wt.% a-LA, into two food-grade, enriched fractions uncontaminated with chemical or mineral additives. In preliminary experiments, acid-aggregation mechanisms and kinetics of a-LA in 10% WPI solutions were determined using 1M HCl, and optimal processing parameters (pH, temperature, residence time) producing the most enriched fractions with the highest individual protein recoveries were defined. The SCO2 process generates carbonic acid within WPI solutions to induce aggregation and precipitation of a-LA proteins but may also introduce pressure effects. To compare the acid fractionation properties of SCO2 with the HCl standard, the pressure-solubility relationship for CO2 in WPI solutions was determined and pH was calibrated versus CO2 pressure (0-14 MPa) and protein concentration (0-28wt.% WPI). Thermodynamic and kinetic limitations of the process were minimized by optimizing critical operating parameters including CO2 pressure, fractionation temperature and mixing speed. Other processing parameters (concentration, residence time) were methodically optimized to maximize aggregation kinetics and obtain high enrichment of both protein fractions as well as high recovery rates for both a-LA and beta-LG proteins. Solid aggregate fractions containing 70% a-LA and soluble liquid fractions containing 95% beta-LG were successfully obtained at 60-62 deg C and CO2 pressures up to 34 MPa. SCO2 and HCl results agreed well. Analysis of the effects of product recovery methods and post-treatment techniques (centrifugation, washing, lyophilization) permitted further improvement of the fractions’ compositions and properties. Enriched whey protein fractions produced with this new SCO2 fractionation process are food-grade and contain no residual chemical (pH 6.0), and will lead to many potential new food and non-food applications.