Enzymatic bleaching in commercial colored Cheddar whey retentates

The effect of enzymatic bleaching with lactoperoxidase (LP) or exogenous peroxidase (EP) on the color and flavor of commercially produced whey protein concentrates (34% or 80% protein on a dry weight basis) was evaluated. Optimum levels of added H2O2 and optimum bleaching times were determined in commercial retentates by quantifying norbixin destruction. Retentates were then bleached and sensory and volatile analyses were conducted. In some retentates, LP-induced bleaching was not observed; however, EP-induced bleaching was effective under all conditions. Enzymatically-induced bleaching (both LP and EP) occurred faster at 35 °C than at 4 °C. Solids level also affected the speed of bleaching; samples with lower solids bleached in less time than those with higher solids. Bleached retentates, regardless of treatment, were higher in aroma intensity and cardboard flavor and were also higher in aldehydes. LP activity and subsequent bleaching of commercial retentates was variable while EP-induced bleaching was consistently effective.