Selective hydrolysis of whey proteins using a flow-through monolithic reactor with large pore size and immobilised trypsin

Abstract

Immobilised trypsin in a flow-through monolithic reactor was able to selectively hydrolyse β-lactoglobulin (β-Lg) in whey protein isolate (WPI), producing a whey product still rich in native α-lactalbumin (α-La). The monolith, with 6.2 ± 0.3 μm pore size, ensured long-term stability and operation at high flow rates, i.e., low backpressure. Increasing the flow rate from 0.8 to 32 mL min−1 reduced the recirculation time by 45% to reach the same degree of hydrolysis (DH) value. The immobilised trypsin showed the greater accessibility to intact β-Lg at increased pH and low ionic strength, i.e., only 14.75 ± 10.14% β-Lg at DH 4% was detectable (pH 9.2, without NaCl). Although α-La was almost inaccessible to the immobilised trypsin (85% of its initial native amount remained in all obtained hydrolysates), its presence significantly influenced the susceptibility of β-Lg, i.e., a three-fold decrease in Vmax for β-Lg hydrolysis was found in the kinetic analysis.