Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2011
Publication Date: 12/27/2011
Citation: Yver, A., Bonnaillie, L., Yee, W.C., Mcaloon, A.J., Tomasula, P.M. 2011. Fractionation of whey protein isolate with supercritical carbon dioxide – process modeling and cost estimation. International Journal of Molecular Sciences. 13(1):240-259.
Interpretive Summary: Supercritical carbon dioxide (sCO2) is a dense gas with interesting acid and solvent properties that has been used to extract and purify various proteins such as soy and fish proteins to manufacture purified protein products. The sCO2 technology is also efficient at separating the proteins of cheese whey and of concentrated whey protein products to prepare enriched fractions of the main proteins, alpha-lactalbumin (alpha-LA), beta-lactoglobulin (beta-LG) and glycomacropeptide (GMP), to provide new food ingredients with excellent nutrition and function, that may be beneficial to specific categories of people such as infants, the elderly, or phenylketonuria patients. The CO2 technology for the preparation of enriched whey protein products has been patented, and is being optimized and modeled using pilot-scale experimental data to design and complete industrial-scale sCO2-fractionation plant. The new model is used to calculate the total production costs and study the cost variations as a function of the quantity (yield) and quality (purity) of the products, both of which are very sensitive to the temperature and pressure in the reactor. The optimization of the operating conditions of the process to minimize total production costs and maximize product quality and quantity will provide whey producers with an affordable, clean, and environmentally-friendly technology for the production of alpha-LA and beta-LG powders that are free of contaminants and ready to use in various health-enhancing food applications.
Technical Abstract: An economical and environmentally friendly whey protein fractionation process was developed using supercritical carbon dioxide (sCO2) as an acid to produce enriched fractions of alpha-lactalbumin (alpha-La) and beta-lactoglobulin (beta-Lg) from a commercial whey protein isolate (WPI) containing 55% beta-LG and 20% alpha-LA, through selective precipitation of alpha-LA. Pilot-scale experiments were performed around the optimal parameter range (T=60 to 65C, P=8 to 31 MPa, C= 5 to 15% (w/w) WPI) to quantify the recovery rates of the individual proteins and the compositions of both fractions as a function of processing conditions. Mass balances were calculated in a process flow-sheet to design a large-scale, semi-continuous process model using SuperproDesigner software to estimate total startup and production costs as a function of processing parameters, product yield and purity. Temperature, T, pressure, P, and concentration, C, showed conflicting effects on equipment costs and the individual precipitation rates of the two proteins, affecting the quantity, quality, and production cost of the fractions considerably. The highest alpha-LA purity, 61%, with 80% alpha-LA recovery in the solid fraction, was obtained at T=60C, C=5% WPI, P=8.3 MPa, with a production cost of $3.92 per pound of WPI treated. The most profitable conditions resulted in 57%-pure alpha-LA, with 71% alpha-LA recovery in the solid fraction and 89% beta-LG recovery in the soluble fraction, and production cost of $2.46 per pound of WPI treated at T=62C, C=10% WPI and P=5.5 MPa. The two fractions are ready-to-use, new food ingredients with a pH of 6.0 and contain no residual acid or chemical contaminants.