Suggested is method for producing galactooligosaccharides, comprising the following steps:



(i) Providing an aqueous milk sugar solution;
(ii) Sterilising the milk sugar solution;
(iii) Performing a transgalactosilation of the milk sugars present in the sterilised milk sugar solution of step (ii) by adding at least one beta-galactosidase within its optimum temperature and pH value intervals for a period of at least 30 minutes, obtaining a reaction mixture;
(iv) Inhibiting the enzyme mass in the reaction mixture of step (iii), and
(v) Confectioning the reaction mixture of step (iv),
Wherein
(a) The enzyme mass is wholly or partly inhibited by setting a pH value outside the activity optimum of the enzymes;
(b) The reaction mixture, together with the inhibited enzyme mass, is subjected to filtration, obtaining a retentate (R1) and a permeate (P1);
(c) The inhibited amount of enzymes is separated as a retentate (R1) and is fed back to step (iii); and
(d) The permeate (P2) containing the galactooligosaccharides is passed on to step (v).