Fermented milk product with a reduced content of lactose
Acidified milk product, which has a pH of between 3.0 and 5.0 and a content of lactose of at least 1.5 mg/ml, wherein the product contains a lactase, which retains its activity at a pH of 5.0 and a temperature of 37° C. at a level of at least 5% as compared to its activity at the optimum pH of the lactase.
1. An acidified milk product, produced by a process comprising:
chemically acidifying or fermenting a milk substrate with a starter culture to obtain an acidified milk product having a pH of between 3.0 and 5.0 and a lactose content of at least 1.5 mg/ml,
subjecting the acidified milk product to heat treatment after chemical acidification or fermentation to achieve a level of bacteria in the acidified milk product of no more than 1×10 2 CFU/g, and
adding a lactase to the acidified milk product after the heat treatment, wherein the lactase exhibits an activity at a pH of 5.0 and a temperature of 37° C. that is at least 5% of its activity at its optimum pH,
wherein the acidified milk product has a pH of between 3.0 and 5.0, contains the lactase, and contains no more than 1×10 2 CFU/g bacteria.
2. The acidified milk product according to claim 1 , wherein the lactase exhibits an activity at a temperature of 10° C. and a pH of 6.0 that is at least 10% of its activity at its optimum temperature.
3. The acidified milk product according to claim 1 , wherein the product contains the lactase in an amount of between 100 and 20000 LAU per liter milk product.
4. The acidified milk product according to claim 1 , wherein the product contains an acid whey product selected from the group consisting of acid whey and acid whey permeate.
5. The acidified milk product according to claim 1 , wherein the lactase is a lactase originating from Bifidobacterium bifidum.
6. The acidified milk product according to claim 5 , wherein the lactase originating from Bifidobacterium bifidum comprises an amino acid sequence which is at least 95% identical to a sequence selected from the group consisting of amino acids 28-1931 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, and lactase active fragments of any thereof.
7. The acidified milk product according to claim 5 , wherein the lactase originating from Bifidobacterium bifidum comprises an amino acid sequence selected from amino acids 28-1931 of SEQ ID NO: 1, amino acids 28-979 of SEQ ID NO: 1, amino acids 28 1170 of SEQ ID NO: 1, amino acids 28-1323 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 1, amino acids 28-1600 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 2, SEQ ID NO: 3, and SEQ ID NO: 4.
8. A process for producing a chemically acidified or fermented milk product, comprising
subjecting a chemically acidified or fermented milk product having a pH of between 3.0 and 5.0 and a lactose content of at least 1.5 mg/ml to heat treatment to achieve a level of bacteria in the product of no more than 1×10 2 CFU per g, to obtain a heat-treated chemically acidified or fermented milk product having a pH of between 3.0 and 5.0 and a lactose content of at least 1.5 mg/ml,
adding a lactase to the heat-treated chemically acidified or fermented milk product, wherein the lactase exhibits an activity at a pH of 5.0 and a temperature of 37° C. that is at least 5% of its activity at its optimum pH, to obtain a lactase-containing chemically acidified or fermented milk product, and
storing the lactase-containing chemically acidified or fermented milk product at a temperature of at least 2° C. for at least 1 day.
9. A process according to claim 8 , wherein the lactase is a lactase originating from Bifidobacterium bifidum.
10. A process according to claim 9 , wherein the lactase originating from Bifidobacterium bifidum comprises an amino acid sequence which is at least 95% identical to a sequence selected from the group consisting of amino acids 28-1931 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, and lactase active fragments of any thereof.
11. A process according to claim 9 , wherein the lactase originating from Bifidobacterium bifidum comprises an amino acid sequence selected from amino acids 28-1931 of SEQ ID NO: 1, amino acids 28-979 of SEQ ID NO: 1, amino acids 28 1170 of SEQ ID NO: 1, amino acids 28-1323 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 1, amino acids 28-1600 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 2, SEQ ID NO: 3, and SEQ ID NO: 4.
12. A process according to claim 8 , wherein the product is a fermented milk product and the method further comprises, prior to the heat treatment, fermenting a milk substrate using a starter culture of lactic acid bacteria to obtain the fermented milk product which has a pH of between 3.0 and 5.0 and a content of lactose of at least 1.5 mg/ml.
13. A process according to claim 12 , wherein the lactase-containing fermented milk product is stored at a temperature of at least 15° C.
14. A process according to claim 12 , wherein the lactase-containing fermented milk product is stored for at least 7 days.
15. A process according to claim 12 , further comprising, after the fermenting and prior to the heat treatment, subjecting the fermented milk product to a concentration step to divide the fermented milk product into a concentrated fraction and a separated acid whey fraction, wherein the separated acid whey fraction is subjected to the subsequent steps of the process.
16. A process for reducing lactose in an acidified milk product during storage, comprising
subjecting an acidified milk product having a pH of between 3.0 and 5.0 and a lactose content of at least 1.5 mg/ml to heat treatment to achieve a level of bacteria in the acidified milk product of no more than 1×10 2 CFU per g, to obtain a heat-treated acidified milk product having a pH of between 3.0 and 5.0 and a lactose content of at least 1.5 mg/ml, and
adding a lactase to the heat-treated acidified milk product, wherein the lactase exhibits an activity at a pH of 5.0 and a temperature of 37° C. that is at least 5% of its activity at its optimum pH.
17. A process according to claim 16 , wherein the lactase is a lactase originating from Bifidobacterium bifidum.
18. A process according to claim 17 , wherein the lactase originating from Bifidobacterium bifidum comprises an amino acid sequence selected from amino acids 28-1931 of SEQ ID NO: 1, amino acids 28-979 of SEQ ID NO: 1, amino acids 28 1170 of SEQ ID NO: 1, amino acids 28-1323 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 1, amino acids 28-1600 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 2, SEQ ID NO: 3, and SEQ ID NO: 4.
19. A process according to claim 17 , wherein the lactase originating from Bifidobacterium bifidum comprises an amino acid sequence which is at least 95% identical to a sequence selected from the group consisting of amino acids 28-1931 of SEQ ID NO: 1, amino acids 28-1331 of SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, and lactase active fragments of any thereof.