Enzyme preparations yielding a clean taste
Process for producing a dairy product by adding a lactase to a dairy product which contains lactose, the lactase added having less than 40 units arylsulfatase activity per NLU of lactase activity.
1. A process for producing a dairy product which comprises adding a lactase obtained from yeast to a dairy product comprising lactose, wherein said lactase comprises less than 40 units arylsulfatase activity per NLU of lactase activity.
2. The process of claim 1 wherein the dairy product produced is free of off-flavours produced by arylsulfatase.
3. The process according to claim 2 , wherein said dairy product contains an alkyl phenol substituted with a sulfate group.
4. The process according to claim 2 , wherein the dairy product contains milk protein.
5. The process according to claim 2 , wherein the dairy product is selected from the group consisting of milk and a fermented milk product.
6. The process according to claim 2 , wherein the level of arylsulfatase in the dairy product during said treating is at most 500*10E3 arylsulfatase units per liter of dairy product.
7. A dairy product obtainable by the process according to claim 2 .
8. The process according to claim 4 , wherein the milk protein is selected from the group consisting of casein and whey protein.
9. The process according to claim 5 , wherein the fermented milk product is yoghurt, whey or a hydrolysate.
10. The process according to claim 6 , wherein the level of arylsulfatase in the dairy product during said treating is at most 250*10E3 arylsulfatase units per liter of dairy product.
11. The process according to claim 10 , wherein the level of arylsulfatase in the dairy product during said treating is at most 100*10E3 arylsulfatase units per liter of dairy product.
12. The process according to claim 10 , wherein the level of arylsulfatase in the dairy product during said treating is at most 50*10E3 arylsulfatase units per liter of dairy product.
13. The process according to claim 10 , wherein the level of arylsulfatase in the dairy product during said treating is at most 25*10E3 arylsulfatase units per liter of dairy product.
14. The process of claim 2 , wherein said lactase is obtained by:
(a) separation of arylsulfatase using chromatography from a preparation which comprises lactase and arylsulfatase,
(b) cultivating a lactase expressing cell in growth medium to which sulphate has been added to repress arylsulfatase expression,
(c) using a lactase expressing cell in which the gene for arylsulfatase is eliminated or disrupted; or
(d) using a lactase expressing strain having less than 10% of the detectable intracellular or extracellular arylsulfatase activity of the wild type strain from which the lactase expressing strain originates.
15. The process according to claim 14 , wherein said lactase is neutral lactase.
16. The process according to claim 14 , wherein said lactase is neutral lactase from Kluyveromyces lactis.
17. The process according to claim 14 , wherein said lactase is a neutral lactase derived from the cytoplasm of yeast.
18. The process according to claim 14 , wherein said off flavor is medicinal.
19. The process according to claim 14 , wherein said lactase expressing strain has less than 5% of the detectable intracellular or extracellular arylsulfatase activity of the wild type strain from which the lactase expressing strain originates.
20. The process according to claim 14 , wherein said lactase expressing strain has less than 1% of the detectable intracellular or extracellular arylsulfatase activity of the wild type strain from which the lactase expressing strain originates.
21. The process according to claim 14 , wherein arylsulfatase activity is undetectable in said lactase expressing strain.
22. The process of claim 1 wherein the yeast is Kluyveromyces.
23. The process of claim 22 wherein the yeast is Kluyveromyces lactis.
24. The process according to claim 14 (c), wherein the gene disruption is achieved by a method selected from one-step gene disruption, marker insertion, site directed mutagenesis, deletion, RNA interference, or anti-sense RNA.
25. The process according to claim 14 (c), wherein the lactase expressing cell in which the gene for arylsulfatase is eliminated or disrupted produces more lactase than the wild type cell under the same culture conditions.