Optimisation of the hydrolysis of goat milk protein for the production of ACE-inhibitory peptides.

Goat milk protein was hydrolysed with subtilisin and trypsin. As input variables, temperature was assayed in the interval 45-70 °C for subtilisin and 30-55 °C for trypsin, while the enzyme-substrate ratio varied from 1 to 5%. The effect of the input variables on the degree of hydrolysis and ACE-inhibitory activity (output variables) was modelled by second order polynomials, which were able to fit the experimental data with deviations below 10%. The individual maximum values of the degree of hydrolysis and the ACE-inhibitory activity were found at conflicting conditions of temperature and enzyme-substrate ratio. Since such maximum values could not be reached simultaneously, a bi-objective optimisation procedure was undertaken, producing a set of non-inferior solutions that weighted both objectives.