Submitted to: Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2014
Publication Date: 1/9/2014
Publication URL: http://handle.nal.usda.gov/10113/59485
Citation: Bonnaillie, L., Qi, P.X., Wickham, E.D., Tomasula, P.M. 2014. Enrichment and purification of casein glycomacropeptide from whey protein isolate using supercritical carbon dioxide processing and membrane filtration. Foods. 3:94-109. DOI: 10.3390/foods3010094.
Interpretive Summary: Whey protein concentrates (WPC) and isolates (WPI) from cheese whey are known as sources of proteins that have excellent digestibility and enhance health and well-being. An environmentally friendly process that uses pressurized carbon dioxide has been developed to remove the individual proteins from WPC or WPI to create new food ingredients that exploit their unique properties. One of these proteins is the little known, GMP, or glycomacropeptide, which can be present in WP in quantities of up to approximately 20%. GMP is a very interesting macro peptide with many proven nutraceutical properties that include dental cavity prevention, appetite suppression, and immune system support. It also has potential as an ingredient in foods for patients with phenylketonuria (PKU) since it does not contain phenylalanine, an amino acid that must be avoided by PKU patients. In this study, the carbon dioxide process has been modified to obtain GMP with purities ranging from 80 to 94%. Because a detailed method to measure the GMP content of WPC or WPI has not yet been made widely available, a new procedure to characterize and measure GMP was also designed. This new procedure uses a step-by-step combination of laboratory spectroscopic and chromatographic techniques. This method requires less time for sample preparation and is more sensitive at low concentrations of GMP than the methods that have been previously reported. This research will allow food researchers and processors to have access to a greater range of nutritious whey proteins that can be used to create health-promoting beverages and foods that are produced using sustainable processing methods.
Technical Abstract: Whey protein concentrates (WPC) and isolates (WPI), which are dried, concentrated forms of cheese whey, are comprised mainly of beta–lactoglobulin (beta-LG), a–lactalbumin (a-LA), and glycomacropeptide (GLY), and are added to foods to boost their nutritional and functional properties. In previous studies, supercritical carbon dioxide (SCO2) was used to fractionate WPC and WPI to obtain enriched protein fractions containing (a-LA) and (beta-LG). In this study, SCO2 was used to fractionate WPI by precipitating a–LA or a–LA and beta-LG and the minor whey proteins to obtain a fraction enriched in beta –LG and GMP or a fraction containing mostly GMP. Optimization of the parameters: temperature, pH, residence time and WPI concentration, showed that maximum precipitation of a–LA was obtained at low pH and at temperatures > 65 deg C. Ultrafiltration was used to separate beta –LG from GMP in the soluble fraction. ß–LG with a purity of 83.9% and GMP with a purity of 58% were obtained. At 70 deg C, both beta -LG and a–LA precipitate leaving a solution rich in GMP that may be purified through ultrafiltration and diafiltration steps to obtain GMP with purity of up to 94%. The collective individual proteins obtained from this process will allow for the design of foods and beverages that target the specific nutritional needs of individuals.