Process for manufacturing of a fermented dairy product

Abstract

A process for the manufacture of a fermented dairy product comprising (a) subjecting a milk base to fermentation with a starter comprising of a weakly post-acidifying bacterial culture, until a desired pH value in the range of 4.0 and 5.0 is reached (end of fermentation), (b) optionally cooling the fermented milk base obtained in step (a); and (c) packaging the fermented dairy product.

Claims

1. A process for manufacturing a fermented dairy product comprising: a. subjecting a milk base to fermentation with a starter comprising at least one Streptococcus salivarius thermophilus strain and at least one Lactobacillus delbrueckii subsp bulgaricus strain, until a desired pH value in a range of 4.0 and 5.0 is reached immediately at the end of fermentation; b. optionally cooling a fermented milk base obtained in (a); and c. packaging the fermented dairy product, wherein at least one Streptococcus salivarius thermophilus strain is weakly post-acidifying, wherein at least one Streptococcus salivarius thermophilus strain is selected from the group consisting of CBS129457 and CBS129458 and wherein the pH value of the packaged fermented dairy product is not less than 4.1 and does not fluctuate more than 0.3 pH unit upon storage at 20° C. or 30° C. for 33 days after the end of fermentation, and wherein weakly post-acidifying is defined as having a two-phase acidification profile, wherein the two-phase acidification profile is determined by continuous recordation of pH as a function of time comprising an initial period from inoculation to end of fermentation followed by a period where pH does not fluctuate more than 0.3 pH unit in a Dutch milk composition comprising 1.5% (w/w) fat, 3.6% (w/w) protein, 4.6% (w/w) carbohydrates and 2% RSM powder to make Dutch fermented milk product.

2. The process of claim 1, wherein the fermented dairy product is a yoghurt.

3. The process according to claim 1, wherein the fermentation temperature is from 30° C. to 45° C.

4. The process according to claim 1, wherein the desired pH value is from 4.0 to 4.7.

5. The process according to claim 1, wherein said milk base is from at least one mammal and/or at least one plant source and/or a mixture thereof, and/or from a mammal selected from the group consisting of a cow, a sheep, a goat, a buffalo, a camel, a llama, a mare, a deer, and/or a combination thereof.

6. The process according to claim 1, wherein the fermented dairy product is a stirred yoghurt and/or a drinking yoghurt.

7. The process according to claim 3, wherein the fermentation temperature is from 37° C. to 42° C.

8. The process according to claim 4, wherein the desired pH value is from 4.3 to 4.5.

Description

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

(1) The advantage of the use of a weakly post-acidifying bacterial culture is that the pH value does not fluctuate more than 0.3 pH unit upon storage measured from day 1 following end of fermentation. The storage conditions at which said pH does not fluctuate more than 0.3 pH may be 1 day or more or may be 40 days or less and the storage temperature may be from 0° C. to 40° C., preferably from 10° C. to 30° C., including said temperatures. In a preferred embodiment, said pH does not fluctuate more than 0.2 pH, more preferably said pH does not fluctuate more than 0.1 pH.

(2) Preferably, the fermented dairy product is as defined hereinbefore such any type of regular yoghurt, low fat yoghurt, non fat yoghurt, kefir, dahi, ymer, buttermilk, butterfat, sour cream and sour whipped cream as well as fresh cheeses. Most preferably, the fermented dairy product is yoghurt as defined hereinbefore such as set yoghurt, stirred yoghurt, drinking yoghurt, Petit Suisse, heat treated yoghurt and yoghurt-like products. More preferably, the yoghurt is a stirred yoghurt or a drinking yoghurt.

(3) The weakly post-acidifying bacterial culture can be any culture having a two-phase acidification profile in Dutch and/or Chinese milk as defined hereinbefore. Preferably the weakly post-acidifying bacterial culture is selected from the genus Streptococcus, more preferably Streptococcus salivarius thermophilus. Most preferably, the weakly post-acidifying bacterial culture is selected from the group consisting of CBS129457 and CBS129458 deposited on 6 May 2011 at the Centraalbureau voor Schimmelcultures (Fungal Biodiversity Centre), Utrecht, The Netherlands.

(4) In a preferred embodiment, the starter further comprises at least one Lactobacillus delbrueckii subsp bulgaricus strain, more preferably at least one Lactobacillus delbrueckii subsp bulgaricus and at least Streptococcus salivarius thermophilus strain selected from the group consisting of CBS129457 and CBS129458 deposited on 6 May 2011 at the Centraalbureau voor Schimmelcultures (Fungal Biodiversity Centre), Utrecht, The Netherlands.

(5) In another preferred embodiment, the starter comprises an exopolysaccharide-producing bacterium strain as have been defined hereinbefore. This may be a Lactobacillus, or a weakly post-acidifying bacterial such as a Streptococcus salivarius thermophilus strain described hereinbefore or another strain.

(6) In the process of the invention, the fermented dairy product is maintained at a fermentation temperature until the desired pH value in the range of 4.0 and 5.0 is reached (end of fermentation) preferably 4.0 to 4.7 and more preferably in the range of 4.2 to 4.5. For a Dutch fermented milk product the pH is preferably in the range of 4.2-5.0. The length of the fermentation period is not critical for the present invention and can be determined easily by the skilled person. The fermentation temperature may be in the range of 30° C.-45° C., more preferably in the range of 37° C.-42° C.

(7) In the process of the invention, any milk can be used such as the milk from a mammal selected from the group consisting of cow, sheep, goat, buffalo, camel, llama, mare, deer, and combinations thereof. Preferably the milk of cow, more preferably Dutch milk or Chinese milk is used.

(8) Preferably, the fermentation is not stopped by exhaustion of a nutrient added to the milk base, but by cooling as in step (b) of the process of the invention. In this embodiment, the fermented dairy product may be cooled down from the fermentation temperature as defined above, for example a temperature between 30 and 45° C., to a lower temperature, for example in a range between 4 and 20° C., more preferably below 10° C., most preferably between 4 and 7° C.

(9) In a second aspect the invention provides a weakly post-acidifying bacterial culture having a two-phase acidification profile, as determined by the continuous recordation of the pH as a function of time, in a Dutch milk composition comprising 1.5% (w/w) fat, 3.6% (w/w) protein, 4.6% (w/w) carbohydrates and 2% RSM powder and/or a Chinese milk composition comprising 2.9% (w/w) protein, 3.6% (w/w) fat, 4.7% (w/w) carbohydrates at 42° C., comprising an initial period between inoculation and end of fermentation followed by a period at 30° C. between 1 and 40 days in which the pH value does not fluctuate more than 0.3 unit. Preferably the pH does not fluctuate more than 0.2 pH, more preferably said pH does not fluctuate more than 0.1 pH

(10) In a preferred embodiment, the bacterial culture comprises at least one weakly post-acidifying bacterial culture of the genus Streptococcus more preferably the strain Streptococcus salivarius thermophilus. Highly preferred is a Streptococcus salivarius thermophilus strain selected from the group consisting of CBS129457 and CBS129458 deposited on 6 May 2011 at the Centraalbureau voor Schimmelcultures (Fungal Biodiversity Centre), Utrecht, The Netherlands.

(11) In a third aspect the invention provides the use of a weakly post-acidifying bacterial culture as defined in the second aspect of the invention in a process for the production of a fermented dairy product.

(12) TABLE-US-00001 MATERIALS AND METHODS Cultures CBS-number Strain Deposit date* CBS129457 Streptococcus salivarius thermophilus 6 May 2011 CBS129458 Streptococcus salivarius thermophilus 6 May 2011 CBS132133 Streptococcus salivarius thermophilus 13 Mar. 2012 *deposited at the Centraalbureau voor Schimmel-cultures (Fungal Biodiversity Centre), Utrecht, The Netherlands

(13) The streptococcus strains CBS129457 and CBS129458 are EPS-producing strains that produce a highly viscous, smooth yoghurt product.

(14) Lactobacillus delbrueckii subsp. bulgaricus 100-B is a commercial culture strain and can be obtained from DSM Food Specialties B.V., Delft, The Netherlands—www.dsm.com.

(15) Preculturing of the Cultures

(16) Selected Streptococcus salivarius thermophilus strains and a Lactobacillus delbrueckii subsp. bulgaricus 100-B were precultured overnight at 37° C. in 10% (w/v) reconstituted skimmed milk (RSM) (Nilac, NIZO food research) supplemented with 0.05% (w/v) yeast extract.

(17) Milk Type

(18) Dutch milk composition: 3.6% (w/w) protein, 1.5% (w/w) fat, 4.6% (w/w) carbohydrates and 2% (w/v) RSM powder Chinese milk composition: 2.9% (w/w) protein, 3.6% (w/w) fat, 4.7% (w/w) carbohydrates

Example 1

(19) Dutch or Chinese milk was inoculated with 10.sup.7 cfu/ml Streptococci inoculum from a full-grown preculture and 10.sup.3 cfu/ml Lactobacillus bulgaricus 100-B inoculation from a full-grown preculture. The inoculated milk was incubated at temperature of 42° C. until a pH of approximately 4.6 was reached (end of fermentation). The yoghurts were quickly cooled in melting ice water (0° C.) and subsequently stored at indicated temperatures 10, and 30° C. for up to 33 days. The pH of yoghurts was monitored at indicated time intervals.

(20) The results in Table 1 show that the pH of yoghurts obtained at the end of the fermentation step does not substantially change upon storage between day 1 and day 33. At 10° C., 20° C. and 30° C. storage for 33 days, the pH value of yoghurts is in all cases higher than 4.1. A pH value above 4.1 of a yoghurt product is considered as advantageous for taste perception by the consumers.

(21) TABLE-US-00002 TABLE 1 Strains Milk type end fermentation day 1 day 7 day 15 day 28 day 33 a: pH of yoghurts at the end of fermentation and during storage at 10° C. for up to 33 days. Yoghurts are prepared with indicated Streptococcal strains and a Lactobacillus delbrueckii subsp bulgaricus. storage temp 10° C. CBS129458 Dutch milk 4.62 4.42 4.37 4.37 4.37 4.37 CBS129457 Dutch milk 4.62 4.48 4.34 4.31 4.30 4.30 CBS129458 Chinese milk 4.60 4.28 4.22 4.23 4.20 4.20 CBS129457 Chinese milk 4.60 4.38 4.28 4.24 4.23 4.23 b : pH of yoghurts at the end of fermentation and during storage at 20° C. for up to 33 days. Yoghurts are prepared with indicated streptococcal strains and a Lactobacillus delbrueckii subsp bulgaricus. storage temp 20° C. CBS129458 Dutch milk 4.62 4.37 4.33 4.34 4.33 4.29 CBS129457 Dutch milk 4.62 4.37 4.29 4.30 4.29 4.24 CBS129458 Chinese milk 4.60 4.24 4.20 4.19 4.17 4.15 CBS129457 Chinese milk 4.60 4.30 4.22 4.22 4.21 4.19 c: pH of yoghurts at the end of fermentation and during storage at 30° C. for up to 33 days. Yoghurts are prepared with indicated streptococcal strains and a Lactobacillus delbrueckii subsp bulgaricus. storage temp 30° C. CBS129458 Dutch milk 4.64 4.32 4.29 4.31 4.26 4.26 CBS129457 Dutch milk 4.62 4.31 4.25 4.28 4.26 4.26 CBS129458 Chinese milk 4.60 4.17 4.15 4.14 4.14 4.14 CBS129457 Chinese milk 4.60 4.19 4.18 4.17 4.15 4.15

(22) The results in Table 2 show that the pH of yoghurts obtained at the end of the fermentation step do substantially change upon storage with the control strain CBS132133.

(23) TABLE-US-00003 TABLE 2 a: pH of yoghurts at the end of fermentation and during storage at 10° C. for up to 28 days. Yoghurts are prepared with the indicated Streptococcal strain and a Lactobacillus delbrueckii subsp bulgaricus. Strain Milk type end fermentation day 1 day 7 day 14 day 21 day 28 storage temp 10° C. CBS132133 Dutch milk 4.62 4.39 4.14 4.17 4.14 4.08 storage temp 20° C. CBS132133 Dutch milk 4.62 4.32 4.11 4.08 4.14 4.11 storage temp 30° C. CBS132133 Dutch milk 4.62 4.22 4.10 4.10 4.04 3.90