Process for preparing fermented soybean milk

Details Process for preparing fermented soybean milk Process for preparing fermented soybean milk

1998-01-21

2003-07-29

Hendricks, Keith (Department: 1761)

Food or edible material: processes, compositions, and products

Fermentation processes

Of isolated seed, bean or nut, or material derived therefrom

Reexamination Certificate

active

06599543

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing a fermented soybean milk.
2. Description of the Related Art
Recently, vegetable protein has attracted public attention from the point of view of health. Especially, soybean milk, which is made from soybean, containing good quality protein but not cholesterol, has attracted a great deal of public attention as a health food.
However, there are some problems in using the soybean milk. For example, the soybean milk has an unpalatable taste such as grassy smelling and stimulating taste due to minor components from soybean such as 2-hexenal and several saponins.
In order to improve the flavor of soybean milk, some methods including a step of fermenting soybean milk with lactic acid bacterium have been proposed, for example, in Japanese Laid Open Patent Applications Nos. SHO 61-141840, SHO 62-205735, SHO 63-7743, SHO 63-276979, HEI 2-167044, HEI 6-276979 and HEI 8-66161. However, the products obtained by these known methods still have some problems such as insufficient masking of the unfavorable soybean flavor, unpleasant fermentation flavor, and a disappearance of the soybean's body and taste.
For the purpose of solving these problems, the inventors have tried to ferment soybean milk with various strains of lactic acid bacteria, and have found that lactic acid bacterium of the genus Bifidobacterium is useful to improve the unpleasant flavor peculiar to soybean without adding components other than soybean. However, when the inventors
Lactobacillus bulgaricus
, which had been known to have flavor improving ability, in addition to Bifidobacterium bacteria, the former bacteria could not grow well in soybean milk. When saccharides that are utilized by lactic-acid bacteria were added to the soybean milk,
Lactobacillus bulgaricus
could grow well in soybean milk, but the flavor of the obtained fermented soybean milk was not improved sufficiently.
On the other hand, the conventional lactic-acid fermented soybean milk has a problem that it generates reverse odor of soybean during cold storage. Therefore, conventional products are heat-treated so that the bacteria in the products are destroyed. However, the heat treatment causes aggregation of the product or generation of unpleasant taste.
SUMMARY OF THE INVENTION
One object of the present invention is to provide lactic-acid fermented soybean milk having an improved total flavor without the unpleasant flavor of conventional soybean milk.
The present invention provides a process for preparing fermented soybean milk comprising the steps of: inoculating a lactic acid bacterium of the genus Bifidobacterium,
Lactobacillus bulgaricus
and one strain selected from the group consisting of
Lactobacillus acidophilus
and
Lactobacillus casei
to soybean milk, and fermenting the same.
Soybean milk used in the present invention is preferably one obtained by the process comprising the steps of contacting dehulled and dehypocotyl whole soybeans with warm or hot water; removing the warm or hot water-soluble component from the soybeans; pulverizing the soybeans to make a slurry, and removing the insoluble component from the slurry.
Another object of the present invention is to provide a lactic-acid fermented soybean milk, which can be stored longer without the problem of reversed odor of soybean. The present invention also provides a process for producing lactic acid fermented soybean milk further comprising the step of introducing the lactic acid fermented soybean milk into an container made of a material having an oxygen permeability of below 100 cc/ m
2
/24 hr/atm (25 &mgr;m, 25° C., 50% RH).
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the present invention, soybean milk may be one obtained from whole or defatted soybeans according to any conventional method and may be any conventional commercially available soybean milk. For example, soybean milk can be obtained by the process comprising the steps of impregnating whole soybeans or dehulled soybeans with water by immersing them into water or any other procedure, pulverizing the same with water to make a slurry and removing the insoluble portion of the slurry by a method such as filtration, to provide soybean milk.
The soybeans employed in the present invention may be whole or defatted soybeans, preferably dehulled soybeans, and more preferably dehulled and dehypocotyl soybeans. According to the present invention, it is preferred to remove the hot or warm water-soluble portion of the soybeans by contacting the same with the hot or warm water and then separating and removing the water phase containing the portion eluted in the water. Said portion may contain isoflavone, sapogenin and saccharides. In the case of whole soybeans, the soybeans may be contacted with water at a temperature of about 50 to 100° C. for about 30 minutes to 10 hours. In the case of dehulled and dehypocotyl soybeans, the temperature of the water may be about 20 to 100° C. and the contacting time may be about 20 minutes to 10 hours. Most preferably, the hot or warm water-soluble portion may be removed from the soybeans so that said portion remaining in the soybean milk is no more than 20 percent, preferably, no more than 15 percent by weight of the dried solid portion of the obtained soybean milk.
According to the present invention, the pH of the hot or warm water with which the soybeans are contacted may be from neutral to weakly alkaline.
Preferably, the pH is weakly alkaline in order to avoid stimulating taste due to the effect of &bgr;-glucosidase. Any food additive, which can adjust the pH to weakly alkaline, may be employed to control the pH. For example, a salt of an organic acid such as sodium dioxide carbonate and sodium carbonate is preferably used from the point of view of flavor.
After that, the treated soybeans are pulverized in water to make a slurry and then, soybean milk can be obtained by separating and removing the insoluble portion from the slurry.
The step of pulverizing the soybeans may be conducted at room temperature. However, in order to prevent degradation of the product during the pulverizing step due to lipoxygenase, peroxidase or &bgr;-glucosidase, it is preferable to carry out the step at a temperature of below about 10° C. or above about 80° C.
The obtained slurry may be kept above about 80° C. and then may be separated into okara and soybean milk by any conventional means such as filtration, decanting, centrifugation or the like.
The soybean milk obtained as above may be sterilized by, for example, heating it to about 135 to 150° C. for about 1 to 120 seconds before fermentation.
Since the soybean milk obtained as above has good flavor, it will provide good flavor to the fermented soybean milk of the present invention. In addition, because of the relatively small concentration of saccharides, it is easy to control the fermentation of the soybean milk by adding saccharides to the same, which saccharides are utilized by lactic-acid bacteria.
It is preferable to add some saccharides, which are utilized by lactic-acid bacteria, to the soybean milk to promote fermentation. Any saccharides utilized by lactic-acid bacterium may be employed, and oligo saccharides are preferable. When oligo saccharides are employed, they may be added to the soybean milk in an amount of about 0 to 5%, preferably, 1 to 2% by weight of the soybean milk. In addition, bifidus factor may be added to the soybean milk.
The lactic-acid bacterium of the genus Bifidobacterium used in the present invention may be any strain belonging to said genus. For example,
B. bifzdum, B. longum, B. breve, B. infantis
, and
B. animalis
may be used for the present invention. However, from the point of view of health, it is preferable to use bacterium occurring in human, i.e. other than
B. animals.
Lactobacillus bulgaricus
used in the present invention may be any of the known strain and these are commercially available.
Both of
Lactobacillus acidophilus
and
Lactobacillus casei
used in the present invention may be any of the known

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