Milk Products Comprising High Amounts of Galactooligosaccharides (GOS) and Their Production
The present invention relates to milk products comprising a high amount of in situ produced galactooligosaccharides (GOS) and methods of producing same. Milk substrate having a lactose content of at least 20 wt % lactose is treated with an enzyme having transgalactosylating activity. The transgalactosylating activity of said enzyme may have been increased via glycation of lysine and/or arginine residues by incubation of said enzyme with high concentrations of glucose at elevated temperatures.
1 . A milk product which comprises a total amount of at least 11 wt % of in situ produced DP3+ galactooligosaccharides (GOS) and wherein the in situ produced DP3+ GOS constitute at least 35 wt % of the total free carbohydrates.
2 . The milk product of claim 1 , which is reconstituted milk powder, concentrated milk, or milk powder.
3 . The milk product of claim 1 , which comprises at least 40 wt % dry matter.
4 . The milk product of claim 1 , which comprises a total amount of at least 10 wt % milk protein.
5 . The milk product of claim 1 , which does not comprise added lactose.
6 . The milk product of claim 1 , wherein at least 50 wt % of the total free carbohydrates is in situ produced DP2+ GOS.
7 . A method for producing a milk product which comprises:
(a) providing a milk substrate comprising at least 20 wt % lactose,
(b) contacting the milk substrate with an enzyme having transgalactosylating activity for at least 45 minutes,
(c) fully or partly inactivating the enzyme, and
(d) thereby obtaining a milk product wherein at least 35 wt % of the total free carbohydrates is in situ produced DP3+ galactooligosaccharides (GOS).
8 . The method of claim 7 , wherein the milk substrate is reconstituted milk powder or concentrated milk.
9 . The method of claim 7 , wherein the milk substrate comprises a total amount of at least 10 wt % milk protein.
10 . The method of claim 7 , wherein the milk substrate does not comprise added lactose.
11 . The method of claim 7 , wherein the milk substrate comprises at least 40 wt % dry matter.
12 . The method of claim 7 , wherein at least 50 wt % of the total free carbohydrates in the milk product is in situ produced DP2+ GOS.
13 . The method of claim 7 , wherein the enzyme having transgalactosylating activity enzyme is a beta-galactosidase having a ratio of transgalactosylating to hydrolysing activity of at least 1, when measured in a 60% solution of skim milk powder after 24 hours at 50° C. using an enzyme concentration of 13 LAU(C) per g lactose.
14 . The method of claim 7 , wherein the enzyme having transgalactosylating activity has an amino acid sequence which is at least identical to amino acids 1-1304 of SEQ ID NO: 1 and has a length of 900-1350 amino acids.
15 . A milk product obtainable by the method of claim 7 .