Enzymatic modification of vegetable protein: Mechanism,kinetics, and production of soluble and partially soluble protein in a batch reactor

Enzymatic hydrolysis of insoluble soybean protein by a protease enzyme produced by Penicillium duponti K 1104, was investigated in a batch reactor. The reaction conditions were 30–55°C and pH 3.4–3.7. The mechanism of solubilization of the insoluble protein by the Penicillium duponti enzyme was deduced from a series of experiments. Kinetic models were developed that involved adsorption followed by peptic digestion of protein, inhibition of low-molecular-weight peptides, and enzyme deactivation. The uncoupled kinetic parameters were estimated using the Marquardt nonlinear parameter estimation algorithm. A bang–bang production of soluble and partially soluble protein is suggested for higher productivity. The essential amino acids pattern of the enzyme-Hydrolyzed soy protein was comparable with the unhydrolyzed protein isolate. Aggregation of the soluble protein for an extended time was observable. The low-molecular-weight soluble protein was incorporated into noncarbonated beverages. The amount of protein that could be incorporated into a can of 355 ml noncarbonated beverage, without observable changes in the optical density and also aggregation of the protein, was 2.5 g soluble protein. Beverages with caramel color showed excessive decrease in optical density and precipitation. The kinetics and diffusion in a multipore immobilized-enzyme recycle reactor will be considered in part II of this series.