METHOD FOR PRODUCING AND STORAGE OF STARTER FOR A YOGURT-LIKE FERMENTED MILK PRODUCT "MATSONI"

FIELD OF THE INVENTION

The present invention relates to food industry, particularly to microbiology and biotechnology of fermented milk products, and may be applied to production of handy form of bacterial starter for wholesome or dietetic fermented milk product "matsoni".

BACKGROUND OF THE INVENTION

During the home and the industrial processing of the popular Georgian milk product matsoni, as a starter (besides the pure bacterial culture) is often used matsoni obtained from farms. Also, for processing of new product, matsoni fermented on previous days is used as a starter. In this case matsoni easily loses its significant qualities (degenerates). At the same time, the storage life of a fluid starter is limited because its properties change. From the commercial point of view, the storage and usage of the fluid form of starter are bounded with definite inconveniences.

There are known several methods for producing matsoni and its starter (Georgian patents GE1064U, GE1065U and GEl 066U), which implicate inoculation of milk with pure bacterial cultures, but they do not specify (apply for) the bacterial cultures involved and their ratio (proportional share).

It is also known "A Symbiotic Product and its Application as a Carrier of Natural Bioactive Substances in Functional Food Additives" (international application WO2005056028) that claims usage of symbiotic product containing Lactobacillus delbueckii subsp. bulgaricus, Streptococcus thermophilius and other microorganisms as a starter, but does not specify the role of each component and their optimal ratio.

The "Method for Producing Yogurt-like Soybean Milk Fermented Product" (see Japanese patent JP63007743) by its purpose and significant features is the closest one to the present invention and is selected as its prototype. This method supposes producing yogurt through milk fermentation with symbiotic starter culture containing

Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus along with many other microorganisms, however, the role and ratio of each bacteria are not specified.

In some measure, matsoni may be considered as a product similar to yogurt, but it must possess its distinctive, traditional properties. Therefore, the use of the same symbiotic starter culture as in the prototype will affect the characteristic taste, flavor, consistence, and wholesome qualities of matsoni. Numerous researches and tests carried out by the authors have proved the negative effect mentioned above and determined the main components of matsoni starter (Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus) that are in charge of imparting taste, flavor, consistence, and wholesome qualities specific for matsoni. For example, in yogurt the same functions are charged to Lactobacillus delbrueckii subsp. bulgaricum and Streptococcus thermofilus. The presence of other bacteria (but Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus) in matsoni starter is simply unnecessary (or unnecessary them to exceed a definite ratio) and affects the final result.

AIM OF THE INVENTION

The present invention is aimed at solution of the task of simultaneous improvement of the quality and the wholesome properties of the fermented milk product (matsoni) and stable obtention of them during the reproduction by means of maintenance of the optimal composition of its starter (dedo). Also, it aims to make possible production of handy and shelf stable form of the starter for business enterprises and population.

DISCLOSURE OF THE INVENTION

For achievement of the said task, the method for producing and storage of starter for a yogurt-like fermented milk product "matsoni", implying an inclusion of a symbiotic combination of at least two kinds of bacteria, Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus in its composition, and inoculation of milk medium with them, envisages the following distinguishing essential features:

- the amounts of cells of Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus are taken within the ratio 1/ (2í4);

- until being inoculated in milk for processing matsoni, the starter comprising the symbiotic mixture of Lactobacillus delbruechii subsp. lactis and Streptococcus thermophilus is stored in a lyophilized form.

There is the following cause-effect connection between the distinctive features and the achieved results: the combined usage of only these two components, pure cultures of bacteria Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus in the given optimal ratio in the starter is necessary and enough for preparation of matsoni possessing the best quality and wholesome properties. It is possible to lyophilize such a starter according to the well-known methods and store it in a dry (tableted) form for long term up to several years, maintaining the viability of bacteria, in order to ensure stability of quality during the reproduction of matsoni.

The researches and tests being carried out determined the main components of matsoni starter (Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus) that are in charge of imparting taste, flavor, consistence, and wholesome qualities essential for matsoni. For example, in yogurt the same functions are charged to Lactobacillus delbrueckii subsp. bulgaricum and Streptococcus thermofilus. The presence of other bacteria (but Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus) in matsoni starter is simply unnecessary or their presence in amounts exceeding the definite ratio affects the final result. Especially, the total amount of microorganism cells of yeast Saccharomicetes serevisiae or bacterial cells of Enterococcus durans (the last often presence in home-made matsoni) must be at least 10 times less than amount of Lactobacilus delbrueckii subsp. Lactis cells involved. According to available information, the method of producing fermented milk product matsoni implying the optimal ratio of bacterial components in the starter stated in the technical description, have not been known in the technical background. The suggested compound of attributes is not evident for a specialist from the existing technical background, since it was discovered and developed through the numerous scientific researches and experiments carried out by the authors. Therefore, the authors trust that the applied invention meets criteria of "novelty" and "level of invention".

The majority of the strains related to Lactobacilus delbrueckii subsp. Lactis is characterized with an antagonistic action against the pathogens causing intestinal diseases and disorders, such as E. coli, Sh. dysenteriae, Salmonella enteritidis, S. aureus, etc. Due to this property of the products manufactured on the base of the abovementioned bacteria, they may be recommended as the dietetic and wholesome products for children and adults.

EMBODIMENTS OF THE INVENTION (Industrial applications.)

The starter (dedo) for matsoni is to be prepared as follows: EXAMPLE 1. (Fluid starter.)

The cultures of Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus are taken (for example, from the depositary collection of pure cultures). Colonies of bacteria are being grown in inoculated skim milk at the optimal temperatures which are 42 ⁰ C for Lactobacillus delbrueckii subsp. lactis and 37 ⁰ C for Streptococcus thermofilus. Bacteria are mixed in 1 :3 ratio by amounts of their cells (or easier, by volume), for example, ImI of fluid culture of Lactobacilus delbrueckii subsp. Lactis with concentration 10 ⁹ living cells per ml and 3 ml of fluid culture of Streptococcus thermofilus with concentration 10 ⁹ living cells per ml. The obtained mixture is added to 40ml of pasteurized skim milk and incubated at 42 ⁰ C temperature during 16 hours. The amount of milk used as an inoculation medium makes no difference. It is important the final concentration of each bacterium after the 24-hour incubation to be equal to 10 ⁹ living cells per 1 ml of milk. The obtained substance (fermented milk) is further used as a starter for production of matsoni.

While preparing matsoni, the volume of starter for inoculation is taken in amount equal to 3% of milk volume and matsoni is processed according to the well-known methods.

EXAMPLE 2. (Dry starter.) The cultures of Lactobacillus delbrueckii subsp. lactis and Streptococcus thermofilus are taken. Colonies of bacteria are being grown in a nutrient solution (broth) at the optimal temperatures which are 42 ⁰ C for Lactobacillus delbrueckii subsp.

lactis and 37 ⁰ C for Streptococcus thermofilus. The final concentration of each bacterium after the 24-hour incubation must be equal to living cells per 1 ml of milk.

^• The mixture of Lactobacillus delbrueckii subsp. lactis ( 1 volume) and Streptococcus thermofilus (3 volumes) is centrifuged and to the derived biomass skim milk (1 1%) and solutions of ascorbic acid (2%) and lactose (4%) are added. The obtained mixture is vacuum dehydrated at low temperature (-20 ⁰ C ) (passes lyophilization) that completes preparing of dry starter. The lyophilized starter is added to pasteurized milk for revitalizing before use. After 24-hour incubation the substance comprising revitalized cultures may be used as a starter for matsoni fermentation. To prevent the negative effect of extraneous bacteria, for example, microorganism cells of yeast Saccharomicetes serevisiae or bacterial cells of Enterococcus durans (the last often presence in home-made matsoni) on the consumer properties of matsoni, it is recommended the total amount of extraneous bacteria cells to be at least 10 times less than amount of cells of Lactobacillus delbrueckii subsp. lactis contained in the starter.

The invented method may have a repeated industrial application guarantying constant economical and technical results showing up in increased quality and wholesome properties of final product and stable integrity of these properties during the reproduction due to the optimal composition of the starter and longer storage life provided by its dry form.

The authors consider that according to the facts mentioned above the present invention meets criterion of "industrial applicability".