The present invention relates to Bifidobacterium breve which excellently survives storage, and to fermented soymilk of pleasant flavor containing the same.
Since long ago, fermentation of soymilk by use of microorganisms has been carried out in order to attain sensory improvement of soymilk, which has a characteristic bean odor and grassy taste. In the course of such fermentation treatment, a variety of microorganisms such as lactic acid bacteria, yeasts, Bacillus natto, acetic acid bacteria, and Aspergillus have been employed. It is reported that in most cases such treatment yields fermented products having pleasant flavor.
Soymilk has been known to promote proliferation of microorganisms which belong to genus Bifidobacterium (hereinafter referred to as bifidobacteria), possibly due to soybean oligosaccharide contained in soymilk (Yoichi KOBAYASHI et al., xe2x80x9cIntestinal Flora and Food Factors,xe2x80x9d p69, 1984, published by Gakkai Shuppan Center).
Meanwhile, a number of studies have been conducted on usefulness of bifidobacteria. For example, administration of a live-bacterium preparation (Bifidobacterium breve) has proven to exhibit a curative effect on refractory pediatric diarrhea, and a possible mechanism thereof may be attributed to improvement of intestinal flora. Furthermore, it has been found that administration of the preparation to an adult results in reduction of putrefied products in feces and putrefied-product-producing bacteria. In addition, an immunoactivating effect of bifidobacteria has also been elucidated. Thus, bifidobacteria are considered to contribute to human health through improvement of the intestinal environment (edited by Tomotari MITSUOKA, xe2x80x9cStudy of Bifidobacteria,xe2x80x9d 1994).
Thus, a variety of products employing bifidobacteria have been developed, and simultaneously efforts have been made to develop a fermented soymilk product which contains numerous bifidobacteria and which also maintains a viable count (high survival rate) throughout the period required for product distribution.
However, since bifidobacteria generate lactic acid and acetic acid at a mole ratio of 1:1.5 through metabolism of sugar, bifidobacteria tend to perish by self-produced acid. Therefore, growth thereof to a certain viable count or higher and maintenance of the viable count are difficult.
In order to solve the aforementioned problem, employment of a bifidobacterium, of high survival rate has been proposed (Japanese Patent No. 2563197).
However, even though the employed bifidobacterium shows an improved survival rate as compared with that of a conventional bifidobacterium, the employed bacterium cannot be proliferated to a level of 1xc3x97109 cells/ml or higher, and maintenance of a viable count of at least 1xc3x97108 cells/ml after 14 days"" storage is difficult.
Thus, an object of the present invention is to provide a bifidobacterium which can sustain a certain level of viable count even after storage for a certain period of time. Another object of the invention is to provide fermented soymilk containing the bifidobacterium.
In view of the foregoing, the present inventors have conducted earnest studies, and have discovered a bifidobacterium satisfying the aforementioned requirement for viable count and have also found that fermented soymilk of pleasant flavor and high viable count can be produced by use of the bifidobacterium. The present invention has been accomplished on the basis of these findings.
Accordingly, the present invention provides Bifidobacterium breve exhibiting a viable count of 1xc3x97109 cells/ml or more immediately after culturing in a soymilk medium and sustaining a viable count of 1xc3x97108 cells/ml or more after storage at 10xc2x0 C. for 14 days. The invention also provides fermented soymilk containing the same.