<i>Streptococcus thermophilus </i>for use in preparation of fermented products

Abstract

The present invention relates to novel strains of Streptococcus thermophilus, compositions comprising said strains and to methods for the preparation of such compositions.

Claims

1. A dairy composition comprising milk and Streptococcus thermophilus strain(s) deposited at CNCM under reference number(s) CNCM 1-5030 and/or CNCM 1-4992.

2. The dairy composition according to claim 1, comprising at least 10.sup.5 CFU/g of Streptococcus thermophilus CNCM 1-5030 and/or CNCM 1-4992.

3. The dairy composition according to claim 1, wherein said dairy composition is a fermented composition.

4. The dairy composition according to claim 1, further comprising at least one, two, three or more strains of Bifidobacterium or lactic acid bacteria.

5. The dairy composition according to claim 4, wherein said dairy composition comprises at least two strains of lactic acid bacteria, wherein said strains of lactic acid bacteria comprise at least one strain of Lactobacillus bulgaricus.

6. The dairy composition of claim 4, further comprising one or more strains of Bifidobacterium.

7. The dairy composition of claim 1, wherein the milk is vegetal milk.

8. The dairy composition of claim 7, wherein the vegetal milk is soya, almond, oat, hemp, spelt, coconut, or rice milk.

9. The dairy composition of claim 1, wherein the milk is animal milk.

10. The dairy composition of claim 9, wherein the animal milk is goat, ewe, camel, mare or cow milk.

11. The dairy composition according to claim 1, comprising milk and Streptococcus thermophilus strain deposited at CNCM under reference number CNCM 1-5030.

12. The dairy composition according to claim 1, comprising milk and Streptococcus thermophilus strain deposited at CNCM under reference number CNCM 1-4992.

13. The dairy composition according to claim 1, comprising milk and Streptococcus thermophilus strains deposited at CNCM under reference numbers CNCM 1-5030 and CNCM 1-4992.

14. The dairy composition of according to claim 13, further comprising Lactobacillus bulgaricus.

15. A fermented food product comprising Streptococcus thermophilus strain(s) deposited at CNCM under reference number(s) CNCM 1-5030 and/or CNCM 1-4992.

16. A method for the preparation of a fermented dairy product comprising fermenting a mixture comprising: a) milk; and b) S. thermophilus CNCM 1-5030 and/or CNCM 1-4992, to provide a fermented dairy product.

17. The method according to claim 16, wherein the mixture comprises at least one, two, three or more strains of Bifidobacterium or lactic acid bacteria.

18. The method according to claim 17, further comprising one or more strains of Bifidobacterium.

19. The method according to claim 17, wherein the mixture comprises at least two strains of lactic acid bacteria, wherein said strains of lactic acid bacteria comprise at least one strain of Lactobacillus bulgaricus.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 provides the milk acidification kinetics of S. thermophilus strain CNCM I-4992 as determined according to Example 1. Time in minutes is provided on the x-axis, pH is represented on the y-axis.

(2) FIG. 2 provides the milk acidification kinetics of S. thermophilus strain CNCM I-5030 as determined according to Example 1. Time in minutes is provided on the x-axis, pH is represented on the y-axis.

(3) FIG. 3 provides a plot representing fermented milk post-acidification, S. thermophilus viability and texturizing properties of a panel of over 40 S. thermophilus strains according to Example 2. Post-acidification is represented as dornic acidity increase over 28 day-storage of the fermented on the X-axis. S. thermophilus viability as determined by colony forming unit count loss over 28 day-storage is provided on the Y-axis. Each tested strain is represented by a single circular point and classified according to viscosity of the fermented milk, points highlighted in a square have a measured viscosity of <0.25 Pa. S−1, circular points which are not highlighted by a further shape have a viscosity of 0.25-0.5 Pa. S−1, points highlighted in a pentagon have a measured viscosity of 0.5-0.75 Pa. S−1 and points highlighted in a triangle have a measured viscosity of 0.75-1.1 Pa. S−1.

(4) FIG. 4 provides the dornic acidity of test fermented milks according to Example 3. Acidity was measured at 3 time points; Day 0 (white bar), Day 14 (black bar) and Day 28 (grey bar).

(5) FIG. 5 provides the change in acidity of test and control fermented milks over 28 days according to Example 4.

(6) FIG. 6 provides the milk acidification kinetics of test (dark grey) and control (light grey) fermented milks as determined according to Example 4. Time in minutes is provided on the x-axis, pH is represented on the y-axis.

EXAMPLES

(7) A screening of over 40 strains of S. thermophilus was carried out to identify strains that were firstly suitable for the preparation of fermented milk products (FMP) but that also have sweetness enhancing properties in such products based on their impact on post-acidification during storage and texturizing properties. Two strains of S. thermophilus were selected on the basis of having high viability and good milk acidification properties together with good texturizing capabilities (increased viscosity) and low post-acidification during storage. Sweetness perception enhancing properties of the strains was determined by a tasting panel evaluating two types of FMP.

Example 1

CNCM I-5030 & CNCM I-4992 Milk Acidification and Viability

(8) Reconstituted milk was prepared by mixing 137.5 g skimmed milk powder (Aria) per litre permuted water and pasteurized at 95° C. for 45 minutes, for strain CNCM I-5030 0.5% Vitalarmor 950 (Armor Proteins) was added. Bacterial strains were provided in frozen form by Danone. Strains were inoculated at 1% in the reconstituted milk from a culture obtained in milk enriched by 0.2% of yeast extract, obtained itself by a 1% inoculation of the strain from a first step of culture in M17 medium inoculated by the bacterial strain in frozen form. Fermentation was carried out at 37° C. and monitored using a CINAC pH probe. The resultant fermented milk was cooled and stored at 10° C. for determination of strain viability and post-acidification of the fermented milk over 28 day storage.

(9) S. thermophilus strains CNCM I-1630 and CNCM I-2130 used in the preparation of commercially available fermented milk products were used as the benchmarks for CNCM I-5030 and CNCM I-4992 respectively to determine the suitability of strains for use in the preparation of fermented milk food products.

(10) Streptococcus thermophilus strains CNCM I-5030 & CNCM I-4992 demonstrated excellent milk fermentation properties, as illustrated in the acidification curves provided in FIGS. 1 & 2. Milk fermentation properties of the strains were comparable to commercially used strains CNCM I-1630 and CNCM I-2130 respectively for strains CNCM I-5030 & CNCM I-4992.

Example 2

CNCM I-5030 & CNCM I-4992 Fermented Milk Characteristics

(11) Post-acidification affects the taste of fermented milk products and is caused by the continued production of lactic acid by bacterial cultures during the shelf-life of the products. In order to determine the post-acidification properties of the panel of S. thermophilus strains fermented milk products were prepared using said strains according to Example 1. The change in dornic acid degree of the fermented milks was determined over 28 day-storage at 10° C. Viability of the S. thermophilus strains, as measured by bacterial counts in colony forming units (CFU) was also determined. Finally, texturizing properties of the strains was determined by measuring viscosity. The viscosity was measured by applying a regular shearing strength increase using a rheometer with 2 co-axial cylinders (RM 180, Mettler). Mobile n°1 was used together with the pot n°1. 64 s−1 shearing is applied during 10 seconds on the test product at 10° C.

(12) Results are shown in FIG. 3, a change in dornic degree of zero (i.e. no post-acidification) is preferred. Maintenance of S. thermophilus bacterial counts was measured by CFU counts at the beginning and end of storage, maintenance of high counts together with low post-acidification are preferred. As demonstrated in FIG. 3, of the tested strains CNCM I-5030 & CNCM I-4992 demonstrated an exceptional combination of post-acidification and texturizing properties as well as good strain viability.

Example 3

(13) FMP starter cultures typically contain an association of S. thermophilus and L. bulgaricus strains. Accordingly In order to confirm its post-acidification properties strain CNCM I-4992 was tested in association with 3 different strains of L. bulgaricus. A food-grade fermented milk product was prepared by fermentation of a pasteurized milk base (13.75% cow skim milk powder in permuted water and pasteurized at 95° C. for 45 minutes) with the yogurt starter culture (L. delbrueckii, S. thermophilus). Fermentation was carried out at 37° C., and monitored using a CINAC probe. Fermentation was stopped by rapid cooling when pH 4.7 was reached. The change in dornic acid degree of the fermented milks was determined over 28 day-storage at 10° C. As demonstrated in FIG. 4, post-acidification of the fermented milks remained low.

Example 4

Fermented Milk Product Test

(14) A test fermented milk product starter culture was prepared using strains CNCM I-5030 & CNCM I-4992 together with a L. bulgaricus strain (CNCM I-2787) (test product). As a benchmark a yogurt (Vitalinea™) starter culture containing two strains of S. thermophilus and L. bulgaricus was used (control). Ferments were provided in frozen pellet form and defrosted prior to use at 38° C., the liquid ferment was added to the milk mixture at 0.02% volume. A food-grade fermented milk product was prepared using a homogenized & pasteurized milk mix: 95% milk base (milk, skim milk powder & cream) & 5% sugar and fermenting with the test and control starter cultures. Fermentation was carried out at 38° C. to pH 4.6 (6-7 hours). The resultant fermented milks were smoothed with a mixer (Ystral), cooled to 20° C. and stored at 10° C. for 30 days. The change in dornic acid degree was determined at the end of the storage period. FIG. 6 provides the milk acidification curves of the products prepared using the test (dark grey) and control (light grey) starter cultures, confirming that the favourable acidification kinetics of the test starter culture are comparable to control starter culture. As can be seen in FIG. 5, the test product comprising the strains of the invention had better post-acidification properties.

(15) The qualities of sweetness, acidity, thickness and global dairy notes of Test & benchmark products were assessed by a panel of volunteer testers. Products were tested at days 14 and 28 of storage at 10° C. Fermented milk products prepared using Test starter culture were found to be significantly sweeter than those prepared using benchmark culture.

Example 5

Sweetness Perception Fermented Milk Product

(16) Enhanced sweetness perception of products prepared using the test starter culture according to Example 4 (CNCM I-5030+CNCM I-4992+L. bulgaricus strain) as compared to the control starter culture was confirmed in a “fromage frais” (fresh cheese) style calcium-supplemented FMP.

(17) A food-grade fermented milk product was prepared by fermenting a pasteurized milk mix: 93.85% milk base (milk, skim milk powder & cream), starch 1.5%, 4.5% sugar and 0.15% calcium with the test and control starter cultures. Fermentation was carried out at 38° C. to pH 4.6 (6-7 hours). The two products were compared by a panel of volunteers for visual whey, colour, firmness, acidity, fruity intensity, texture in mouth and off notes. No significant differences were found between the test and control products for visual whey, colour, firmness, sweetness, acidity, fruity intensity, texture in mouth and off notes. However increased sweetness was confirmed in the test product, and differences in firmness were also noted.