Effect of bovine casein and its hydrolysates on hardening in protein dough model systems during storage

In recent years, high protein food bars (HPFB) are a rapidly growing market. One major problem for commercial HPFB is that they become harder over time without moisture loss, making the product unacceptable to consumers. In this study, the effect of bovine casein and its hydrolysates on bar hardening during storage was studied. Five formulations of protein dough model systems were prepared from five commercial spray-dried dairy protein powders. According to our results, moisture migration should be the decisive factor of bar hardening in the moisture nonequilibrium systems during storage. Furthermore, disulfide-induced protein/peptide aggregation could also cause bar hardening. The substitution of a portion of whey protein isolates with either intact casein or hydrolyzed casein proteins could effectively reduce bar hardening during storage. In addition, the effect of the degree of hydrolysis on selected physicochemical properties (moisture sorption and glass transition) and bar hardening was also investigated.