title: Cold enzymatic bleaching of fluid whey.
abstract: Chemical bleaching of fluid whey and retentate with hydrogen peroxide (HP) alone requires high concentrations (100-500 mg of HP/kg) and recent studies have demonstrated that off-flavors are generated during chemical bleaching that carry through to spray-dried whey proteins. Bleaching of fluid whey and retentate with enzymes such as naturally present lactoperoxidase or an exogenous commercial peroxidase (EP) at cold temperatures (4°C) may be a viable alternative to traditional chemical bleaching of whey. The objective of this study was to determine the optimum level of HP for enzymatic bleaching (both lactoperoxidase and EP) at 4°C and to compare bleaching efficacy and sensory characteristics to HP chemical bleaching at 4°C. Selected treatments were subsequently applied for whey protein concentrate with 80% protein (WPC80) manufacture. Fluid Cheddar whey and retentate (80% protein) were manufactured in triplicate from pasteurized whole milk. The optimum concentration of HP (0 to 250 mg/kg) to activate enzymatic bleaching at 4°C was determined by quantifying the loss of norbixin. In subsequent experiments, bleaching efficacy, descriptive sensory analysis, and volatile compounds were monitored at selected time points. A control with no bleaching was also evaluated. Enzymatic bleaching of fluid whey and retentate at 4°C resulted in faster bleaching and higher bleaching efficacy (color loss) than bleaching with HP alone at 250 mg/kg. Due to concentrated levels of naturally present lactoperoxidase, retentate bleached to completion (>80% norbixin destruction in 30 min) faster than fluid whey at 4°C (>80% norbixin destruction in 12h). In fluid whey, the addition of EP decreased bleaching time. Spray-dried WPC80 from bleached wheys, regardless of bleaching treatment, were characterized by a lack of sweet aromatic and buttery flavors, and the presence of cardboard flavor concurrent with higher relative abundance of 1-octen-3-ol and 1-octen-3-one. Among enzymatically bleached WPC80, lactoperoxidase-bleached WPC80 contained higher relative abundance of 2,3-octadienone, 2-pentyl furan, and hexanal than those bleached with added EP. Bleach times, bleaching efficacy, and flavor results suggest that enzymatic bleaching may be a viable and desirable alternative to HP bleaching of fluid whey or retentate.
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh 27695.
authors.forename: R E
authors.initials: RE
authors.lastname: Campbell
authors.forename: M A
authors.initials: MA
authors.lastname: Drake
mesh_terms: D000818:Animals; D057886:Bleaching Agents / Q000494:pharmacology*; D002338:Carotenoids; D003080:Cold Temperature; D003116:Color; D003611:Dairy Products / Q000032:analysis* / Q000592:standards*; D003612:Dairying / Q000379:methods*; D006861:Hydrogen Peroxide / Q000737:chemistry; D007659:Ketones / Q000032:analysis; D007784:Lactoperoxidase / Q000494:pharmacology; D008894:Milk Proteins / Q000737:chemistry*; D000442:Octanols / Q000032:analysis; D000067816:Whey Proteins
chemical_list: D057886:Bleaching Agents; D007659:Ketones; D008894:Milk Proteins; D000442:Octanols; D000067816:Whey Proteins; D002338:Carotenoids; C113805:1-octen-3-one; D006861:Hydrogen Peroxide; C099823:norbixin; D007784:Lactoperoxidase; C038844:1-octen-3-ol
keywords: bleach; flavor; lactoperoxidase; whey