Food or edible material: processes – compositions – and products – Fermentation processes – Of milk or milk product
Patent
1997-03-28
2000-05-02
Sherrer, Curtis E.
Food or edible material: processes, compositions, and products
Fermentation processes
Of milk or milk product
426 42, 426 43, 426583, 4352534, A23C 912, C12N 120
Patent
active
060569794
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a Streptococcus thermophilus strain, to the use of this strain for the production of fermented dairy products and to the products obtained using this strain.
The choice of lactic acid bacteria for the production of fermented dairy products calls into play various criteria, especially the acidifying activity and the formation of flavor components which provide the organoleptic properties of the product and the production of thickening agents which play a role in the texture and the unctuousness.
The acidifying activity is characterized essentially by three parameters: the kinetic of acidification, the titratable acidity and the final fermentation pH which determines the organoleptic characteristics of the product and its preservation quality, and the post-acidification which develops during preservation of the product.
A high rate of acidification makes it possible to reduce the period during which the milk-based product is sensitive to contaminants (pH>4.7) and thereby to reduce the risk of bacterial contamination.
An increase in the rate of acidification also enhances the economics of the process by increasing the productivity and the flexibility of the industrial material.
The post-acidification properties of the strains are particularly important for the preservation of the products. Indeed, fresh fermented products are preserved at temperatures of between about 4.degree. C. and 8.degree. C. for a period in general not exceeding 4 weeks; but if the metabolic activity of the bacteria is reduced by preservation at low temperature, it is not blocked and it brings about the production of lactic acid from lactose, which has as a consequence a reduction in pH and an increase in the acid taste which damages the organoleptic properties of the product.
In addition to the criteria retained for their contribution to the quality of the products, other elements more specifically linked to the process play a role in the choice of the strains, such as the fermentation temperature, the rate of acidification and the resistance to phages.
The resistance to phages is a very important criterion in the choice of the strains for reducing the risk of phage incidents during production which may block for a longer or shorter period the entire production for decontamination.
No S. thermophilus is so far known which exhibits a high rate of acidification and a high degree of acidity combined with a very low or practically zero post-acidification activity.
Indeed, it is generally observed that cultures of S. thermophilus which have a reduced post-acidification activity often show a limited acidifying activity during the fermentation, which does not allow the desired degree of acidity to be achieved in the products. In addition, these strains often have a slow growth and they require high inoculation levels and a longer incubation period which are incompatible with the economics of an industrial process.
The subject of the present invention is an S. thermophilus strain which has a rapid acidification kinetic allowing a high degree of acidity to be achieved and which does not post-acidify fresh fermented products during preservation.
More particularly, the present invention relates to an S. thermophilus strain DN-001 116 deposited at the Collection Nationale de Cultures de Microorganismes (CNCM) under No. I-1477 and mutants thereof which have similar milk acidification characteristics.
Mutant strains having milk acidifying characteristics similar to the deposited strain is intended to designate strains which may be obtained especially by mutation and selection from the reference strain and/or by genetic transformation with the aid of vectors.
The acidifying characteristics are an end-of-incubation pH of 4.6 in less than 4 hours and a pH variation at 28 days of less than 0.2 pH unit, preferably less than 0.1 unit.
The mutant strains may be obtained from the reference strain, especially by mutation and selection according to their acidifying properties. The mutation techniques are known, as well as t
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Le Lait, vol. 71, No. 4, Elsevier, pp. 445-461, Zourari et al., Ccaracterisation de bacteries lactiques thermophiles isolees de yaourts artisanaux grecs. I. Souches de Streptococcus salivarius subspthermophilus.
Database WPI, Section Ch, Week 8824, Derwent Publications Ltd., London, Class D16, An 88-166505 & SU, A, 1351 973 (Dairy Ind. Res. Inst.), Nov. 15, 1987.
Benbadis Laurent
de Villeroche Jacques
Oudot Elisabeth
Compagnie Gervais Danone
Sherrer Curtis E.
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