Bleaching of colored whey and milk by a multiple-enzyme system

Abstract

Carotenoids are broadly used to enhance the color of cheese types like Cheddar and Gouda. While ∼80 % of the colorants are transferred into the cheese, the rest remains in the whey and impedes its commercial utilization. Therefore, cheese whey is currently bleached chemically by addition of either hydrogen peroxide or benzoyl peroxide in the industrial practice. To avoid heat- and peroxide-induced protein denaturation and the formation of off-flavors, an enzymatic bleaching process was developed. The ability of the fungal peroxidase MsP1 to degrade carotenoids was successfully employed for the bleaching of colored whey and milk in two- and three-enzyme systems, respectively. The systems were composed of MsP1, glucose oxidase, and when necessary, acid lactase. The initial step of the three-enzyme system was the lactase-catalyzed hydrolysis of lactose to galactose and glucose. The latter served as a substrate for the enzyme glucose oxidase in the second step which yielded gluconic acid and hydrogen peroxide. Finally, MsP1 oxidatively degraded the carotenoids. The activities of the involved enzymes were fine-tuned to optimize the bleaching process.