Foaming and sensory properties of bovine milk protein isolate and its associated enzymatic hydrolysates

Abstract

The surface tension, foaming, bitterness and colour properties of bovine milk protein isolate (MPI) and MPI hydrolysates generated with Flavourzyme™, Neutrase™ and Protamex™ were evaluated. The surface tension of the hydrolysate samples (46.6–48.3 mN m−1), measured using pendant drop shape analysis, was reduced compared with the intact protein samples (49.1–49.6 mN m−1). The foam half-life of the hydrolysates (58.1–214 s) at 25 °C was significantly reduced compared with the intact protein (783–850 s). The L∗ value of the hydrolysates (69.9–77.4) was significantly lower than the intact protein (84.3–86.0). The Flavourzyme™ hydrolysate (60 min incubation) demonstrated a mean bitterness score (2.14) comparable with the intact protein (1.52–1.57). All other hydrolysates displayed increased bitterness; Neutrase™ and Protamex™ hydrolysates had the highest mean bitterness scores (8.80–9.39). The hydrolysate foaming and sensory properties were enzyme and DH dependent; bitterness development may be minimised by using Flavourzyme™ as the hydrolytic enzyme due to the presence of exopeptidase activities.