Method for producing a dairy product
The present invention relates to a method for producing a dairy product using an enzyme having lactase activity.
1. A method for producing a dairy product comprising treating a milk-based substrate comprising lactose with an enzyme having lactase activity, wherein
(a) the milk-based substrate is selected from the group consisting of whole milk, low fat milk, skim milk, buttermilk, reconstituted milk powder, condensed milk, solutions of dried milk, UHT milk, whey, whey permeate, acid whey and cream;
(b) the enzyme having lactase activity has an amino acid sequence which is at least 90% identical to amino acids 28-1331 of SEQ ID NO: 2 and has a ratio of lactase to transgalactosylase activity of more than 1:1 when hydrolysing the lactose in the milk-based substrate; and
(c) the lactose in the milk-based substrate is reduced in an amount of at least 70%.
2. The method of claim 1 , wherein the enzyme having lactase activity has an amino acid sequence which is at least 95% identical to amino acids 28-1331 of SEQ ID NO: 2.
3. The method of claim 1 , wherein the enzyme having lactase activity has an amino acid sequence which is at least 98% identical to amino acids 28-1331 of SEQ ID NO: 2.
4. The method of claim 1 , wherein the lactose in the milk-based substrate is reduced in an amount of at least 80%.
5. The method of claim 1 , wherein the lactose in the milk-based substrate is reduced in an amount of at least 90%.
6. The method of claim 1 , wherein the lactose in the milk-based substrate is reduced in an amount of at least 95%.
7. The method of claim 1 , wherein the lactose in the milk-based substrate is reduced in an amount of at least 97%.
8. The method of claim 1 , wherein the enzyme having lactase activity has a pH optimum of the lactase activity at 37° C. is above pH 5, and the lactase activity of the enzyme at pH 5 is at least 50% of its lactase activity at pH 6 when measured at 37° C.
9. The method of claim 1 , wherein the treatment takes place at a temperature of at least 50° C.
10. The method of claim 1 wherein the lactase activity of the enzyme at 52° C. is at least 70% of its lactase activity at 38° C. when measured at pH 6.5.
11. The method of claim 1 , wherein the enzyme having lactase activity is added to the milk-based substrate at a concentration of less than 30 LAU per g lactose in the milk-based substrate.
12. The method of claim 1 , wherein the enzyme having lactase activity is added to the milk-based substrate at a concentration of less than 1000 LAU per liter milk-based substrate.
13. The method of claim 1 , further comprising fermenting said substrate with a microorganism, wherein the dairy product is a fermented dairy product.
14. The method of claim 13 , wherein the fermented dairy product is yoghurt.
15. The method of claim 13 , wherein the treatment and the fermentation are performed essentially at the same time.
16. The method of claim 13 , wherein the enzyme and the microorganism are added to the milk-based substrate at essentially the same time.
17. The method of claim 13 , wherein less than 80% of the lactose is hydrolyzed after two hours of fermentation, and more than 90% of the lactose is hydrolyzed in the final fermented dairy product.
18. The method of claim 13 , wherein less than 80% of the lactose is hydrolyzed when fermentation is completed, and more than 90% of the lactose is hydrolyzed in the final fermented dairy product.
19. The method of claim 13 , wherein the enzyme having lactase activity has at most 1304 amino acids.