Enzymatic batch processes bear some disadvantages, such as the high quantity of enzyme, energy and labor needed and, consequently, high production costs. The aim of this study was the production of a sodium caseinate hydrolysate with improved antioxidative capacity and reduced bitterness in a continuous system to avoid such drawbacks. Therefore, a novel, food-grade, two-step enzymatic membrane bioreactor (EMBR) process was designed in which a functional improved permeate with a 33% increased antioxidativity compared to sodium caseinate was produced with the endopeptidases Sternzym BP 25201. This bitter permeate was subsequently debittered in a second EMBR step with commercial Flavourzyme, which was reduced in its endopeptidase activity. This resulted in a linear production of 7.5 gProduct h−1 of antioxidative (antioxidativity: +39% compared to sodium caseinate), debittered peptides. The influence of the peptidases on each other was excluded by separating the endo- and exopeptidases in two EMBR steps and a product with consistent properties like degree of hydrolysis, antioxidativity and taste was obtained. The process conditions chosen were optimal regarding a stable product formation for three days. Therefore, the process was superior in its productivity, enzyme usage and run time compared to an equivalent batch process.
The technofunctional properties (e.g. emulsifying, foam formation) of milk proteins can be influenced by enzymatic hydrolysis. Enzymatic batch process is an established method for the production of protein hydrolysates in the food industry. The disadvantages of an enzymatic batch process include a lack of enzyme reuse, batch-to-batch variations of the final hydrolysate and, depending on the peptidase used, high substrate and product inhibitions. A continuous process using enzyme- immobilization or enzyme membrane bioreactor (EMBR) with free enzyme could overcome these drawbacks. Therefore, the aim of this work was to develop a continuous hydrolysis process for milk protein hydrolysates with a defined peptide composition, new technofunctional properties and without a negative sensory profile (bitterness).