The use of lactoperoxidase for the bleaching of fluid whey

Abstract

Lactoperoxidase (LP) is the second most abundant enzyme in bovine milk and has been used in conjunction with hydrogen peroxide (H2O2) and thiocyanate (SCN–) to work as an antimicrobial in raw milk where pasteurization is not feasible. Thiocyanate is naturally present and the lactoperoxidase system purportedly can be used to bleach dairy products, such as whey, with the addition of very little H2O2 to the system. This study had 3 objectives: 1) to quantify the amount of H2O2 necessary for bleaching of fluid whey using the LP system, 2) to monitor LP activity from raw milk through manufacture of liquid whey, and 3) to compare the flavor of whey protein concentrate 80% (WPC80) bleached by the LP system to that bleached by traditional H2O2 bleaching. Cheddar cheese whey with annatto (15mL of annatto/454kg of milk, annatto with 3% wt/vol norbixin content) was manufactured using a standard Cheddar cheesemaking procedure. Various levels of H2O2 (5–100mg/kg) were added to fluid whey to determine the optimum concentration of H2O2 for LP activity, which was measured using an established colorimetric method. In subsequent experiments, fat-separated whey was bleached for 1h with 250mg of H2O2/kg (traditional) or 20mg of H2O2/kg (LP system). The WPC80 was manufactured from whey bleached with 250mg of H2O2/kg or 20mg of H2O2/kg. All samples were subjected to color analysis (Hunter color values and norbixin extraction) and proximate analysis (fat, protein, and moisture). Sensory and instrumental volatile analyses were conducted on WPC80. Optimal LP bleaching in fluid whey occurred with the addition of 20mg of H2O2/kg. Bleaching of fluid whey at either 35 or 50°C for 1h with LP resulted in >99% norbixin destruction compared with 32 or 47% destruction from bleaching with 250mg of H2O2/kg, at 35 or 50°C for 1h, respectively. Higher aroma intensity and increased lipid oxidation compounds were documented in WPC80 from bleached whey compared with WPC80 from unbleached whey. Monitoring of LP activity throughout cheese and whey manufacture showed that LP activity sharply decreased after 30min of bleaching (17.01±1.4 to <1U/mL), suggesting that sufficient bleaching takes place in a very short amount of time. Lactoperoxidase averaged 13.01±0.7U/mL in unpasteurized, fat-separated liquid whey and 138.6±11.9U/mL in concentrated retentate (11% solids). Lactoperoxidase may be a viable alternative for chemical whey bleaching.