JPS5947589B2 - How to make natto by restoring it with cold water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing instant natto with good flavor by improving the restorability of dried natto and restoring it with cold water.

Various attempts have been made to research methods for producing dried natto that has a long shelf life, and a method for vacuum freeze-drying natto is already known, such as in Japanese Patent Publication No. 21783/1983.

However, the conventional dried natto has extremely poor restorability, and even if it is restored by adding water, it does not have the same stringiness and umami flavor as raw natto.

As a result of our studies on the restoration of dried natto, the present inventors have found that it is possible to produce dried natto with good restorability, and to restore the flavor using cold water of 40°C or lower, preferably 30°C or lower. It is necessary to obtain good instant natto, and for dried natto with good restorability, add 21 to 100% water by weight to raw natto and hold for an appropriate time to fully soak the raw natto with water. After that, they discovered that it could be obtained by vacuum freeze-drying, leading to the present invention.

That is, the present invention is a method for producing natto in which 21 to 100 wt. .

In the present invention, the natto used as a raw material is raw natto produced by a conventional method, and the amount of water added to the raw natto must be 21 to 100% by weight based on the raw natto.

From the test results shown in conjunction with the examples below, if the amount of water added is less than 21% by weight, dried natto with good reconstitution properties that can be restored with cold water cannot be obtained, and if it exceeds 100% by weight, the subsequent vacuum freeze-drying treatment is difficult. Therefore, it is advantageous to keep the content to 100% by weight or less.

When you add water to raw natto and leave it for about an hour, the inside of the natto will be fully impregnated with water, and the sticky substance on the surface of the natto will decrease, increasing its fluidity, making it easier to dry in a vacuum freeze-dryer. It can be expanded to

At this time, if the water to be added is hot water of 50℃ or higher, it will impregnate the natto well and give good results for the restorability of dried natto, so it is recommended to add hot water of 50℃ or higher. desirable.

Furthermore, by adding water to which seasonings such as soy sauce and monosodium glutamate have been added, the natto will be seasoned during the manufacturing process and its flavor can be enhanced.

Next, in the vacuum freeze-drying of the present invention, all conventional vacuum freeze-drying methods can be applied.

If unimpregnated water remains in the raw natto, it may be separated using a wire mesh or the like, and the liquid portion may be contaminated with mucilage on the surface of the natto, so the liquid portion and the natto may be vacuum freeze-dried separately.

Dried natto obtained by vacuum freeze-drying as described in Section 2 has extremely good reconstitution properties, and can be reconstituted in 7 to 15 minutes even with cold water.

During this restoration, if the temperature of the water is high, the restored natto will feel strange and undesirable, so it is necessary to restore with cold water of 40° C. or lower, preferably 30° C. or lower.

When reconstituted with cold water of 40° C. or lower, the reconstituted natto has an umami taste, has almost no unpleasant natto odor, is firm and not too soft, and has a good flavor.

When raw natto is vacuum freeze-dried, the outer layer including the sticky part and outer skin of natto can be separated from the inner layer very easily, and the outer layer, which has a small volume and apparent specific gravity, can be separated using a shaking sieve, air classifier, etc. However, if the outer layer and inner layer of natto vacuum freeze-dried by the method of the present invention are separated as described above, the resiliency improves, so it is possible to carry out the present invention. This is particularly desirable.

In this case, the separated outer layer and inner layer can be restored simultaneously in the same container with cold water.The inner layer can be restored first with cold water and then the outer layer can be added.

Examples, reference examples, tests, and test results of the present invention are shown below.

Reference example 1 Spread 600g of commercially available natto on a tray to a thickness of about 1cm, -
After pre-freezing in a freezer at 20°C to -30°C, dry by vacuum freeze-drying with a vacuum freeze dryer RL-50VS manufactured by Kyowa Shinku Co., Ltd. while maintaining the temperature of the drying shelf at 25°C to 40°C. 245 g of natto was obtained.

30 ml of water at 20° C. was added to 22.5 g of this dried natto, stirred gently, held for 8 minutes, then stirred again, and 10 minutes after the water was added, a sensory test was immediately conducted.

Reference Example 2 A product was produced and restored in the same manner as in Example 2, except that hot water at 80° C. was used instead of the water temperature of 20° C. during restoration in Example 2, and a sensory test was conducted.

Reference Example 3 Instead of adding 360 ml of hot water to 600 g of commercially available natto in Example 2, 190 ml (15% by weight) of hot water was added, and otherwise the same procedure as in Example 2 was carried out to produce and reconstitute the product, and a sensory test was conducted.

Reference Example 4 Instead of adding 360 ml of hot water to 600 g of commercially available natto in Example 2, 108 ml (18% by weight) of hot water was added, and otherwise the product was manufactured and reconstituted in the same manner as in Example 2, and a sensory test was conducted.

Example 1 600g of commercially available natto and 360ml of hot water (60% by weight)
was added and kept at 65° C. for 1 hour, then spread on a tray to a thickness of about 1 cm, and vacuum freeze-dried in the same manner as in Reference Example 1 to obtain 230 g of dried natto.

To 22.5 g of this dried natto, 30 ml of water at 20° C. was added and reconstituted in the same manner as in Reference Example 1, and a sensory test was conducted.

Example 2 600g of commercially available natto and 360ml of hot water (60% by weight)
was added and kept at 65° C. for 1 hour, then spread on a tray to a thickness of about 1 cm, and then vacuum freeze-dried in the same manner as in Reference Example 1.

This was shaken and sieved using a No. 6 ASTM-II sieve to obtain 190 g of an inner layer portion and 35 g of an outer layer portion.

2.5 g of the outer layer portion and 20 g of the inner layer portion were placed in the same container, 30 ml of water at a temperature of 20° C. was added, and the mixture was reconstituted in the same manner as in Reference Example 1, and a sensory test was conducted.

Example 3 Add 3.3 kg of commercially available natto to 3.3 kg of hot water (100% by weight)
) was added, stirred, and left at 50° C. for 1 hour, then separated using a wire mesh to obtain 2 kg of liquid portion and 4.6 kg of natto portion.

The natto portion and the liquid portion were placed separately in trays and vacuum freeze-dried in the same manner as in Reference Example 1 to obtain a liquid portion and a dried natto portion.

The dried natto portion was shaken and sieved using an ASTM-56 sieve to separate it into an outer layer portion and an inner layer portion to obtain 942 g of an inner layer portion.

In addition, the obtained outer layer part and liquid part dry matter were mixed to form a mixture 305.
I got g.

20 g of the inner layer, 2.5 g of the mixture of the outer layer and the liquid dry matter were placed in the same container, 30 ml of 18° C. water was added thereto, reconstituted in the same manner as in Reference Example 1, and a sensory test was conducted.

Example 4 20g of the inner layer obtained in Example 2 was placed in a container and the temperature was 20°C.
After adding 30 ml of water and stirring gently, the mixture was allowed to stand for 8 minutes, then 2.5 g of the outer layer obtained in Example 2 was added and stirred, and 10 minutes after the addition of water, a sensory test was conducted.

Example 5 Instead of adding 360 ml of hot water to 600 g of commercially available natto in Example 2, 126 ml (21% by weight) was added, and otherwise the same method as in Example 2 was used to produce and reconstitute Instant I natto, and a sensory test was conducted. I did it.

Example 6 Instant natto was manufactured and reconstituted in the same manner as in Example 2, except that instead of adding 360 ml of hot water to 600 g of commercially available natto in Example 2, 240 ml (40% by weight) was added, and the rest was the same as in Example 2. Instant natto was produced and reconstituted, and a sensory test was conducted. .

Example 7 Instant natto was produced and reconstituted in the same manner as in Example 1, except that instead of adding 360 ml of hot water to 600 g of commercially available natto in Example 1, 180 ml (30% by weight) was added, and the rest was the same as in Example 1. Instant natto was produced and reconstituted, and a sensory test was conducted. .

The sensory test was conducted by a panel of 10 experts, and the moisture permeability,
The firmness, stringiness, and pleasantness of taste were evaluated using numerical scaling, and the results are shown in the following table.

water permeability 5 Very good.

4 Good, there is a slight unpenetrated area.

3. Approximately 30% of the parts are rough when chewed.

2 50% kuku 1 Very bad.

waist strength 3 good 2 medium 1 The beans are too soft and fall apart.

Stringiness, pleasant taste 3 good 2 medium 1.

, *Not measurable due to insufficient restoration.'' - The results of tests on the amount of water added to commercially available natto and the water permeability (restorability) during restoration, as well as examples and reference examples, are shown in the drawing. So, the amount of water added is 21% by weight.
The above method was found to have extremely good restorability.

[Brief explanation of drawings]

The figure is a chart showing the relationship between the amount of water added to natto edibles and the water permeability of the obtained dried natto.

Claims (1)

[Scope of Claims] 1. A method for producing natto in which 21 to 100% by weight of water is added to natto, held for an appropriate amount of time, freeze-dried in vacuum, and reconstituted in cold water. . 2. A method for producing natto reconstituted with cold water according to claim 1, wherein the outer layer and the inner layer of natto are separated after vacuum freeze-drying.