JP2707166B2 - Sponge gel and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sponge-like gel, and more particularly to a sponge-like porous material applicable to a wide range of fields such as foods, shock absorbers, and water absorbing materials.

[0002]

2. Description of the Related Art Conventionally, as a technique combining protein and chitosan, a method in which milk protein and chitosan are contained in water, pH is adjusted and heat treatment is carried out (JP-A-63-169939),
After adding collagen to chitosan and forming it into a sponge,
A method for acylation (JP-A-62-238209) is known.
However, a technique for gelling a complex of protein and chitosan by freeze treatment as in the present invention has not yet been reported.

According to the method, the precipitate obtained by the heat treatment is an aggregate of a complex of milk protein and chitosan, and this is dried by spray drying or freeze drying to obtain a partially dehydrated product or powder thereof. Can be obtained, but does not provide a sponge-like gel as in the present invention. Collagen used is a protein, but has little reactivity with chitosan because its constituent amino acids are limited to glycine, proline, hydroxyproline and alanine. In other words, the method is a technique for producing an insoluble sponge-like material by acylating chitosan, and collagen is only used as a reinforcing agent. In this method, it is necessary to add a collagen to an acid solution of chitosan, prepare a sponge-like molded product by freeze-drying or the like, and then perform acylation.
It is necessary to use a large amount of an acylating agent, which is suitable as a cosmetic material, but has a problem that it is difficult to use it for food.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a chitosan sponge-like gel which can be applied to a wide range of fields including the food field without performing chemical synthesis such as acylation.

[0005]

The present invention provides a soy protein,
A protein selected from whey protein or casein , chitosan, and water are mixed under acidic conditions, then neutralized and uniformly mixed, and the resulting viscous mixture is further sponge-formed by freezing. It is a gel. The present invention is also a method for producing a sponge-like gel in which the raw materials are mixed under acidic conditions and then neutralized to uniformly mix the resulting viscous mixture, followed by freezing.

As the protein used in the present invention, any protein having high reactivity with chitosan can be used, but soy protein, whey protein and casein are preferred. These proteins can be denatured by heating in advance to increase the gel strength. Here, casein includes dairy products such as milk, skim milk powder, and casein soda. Collagen with low reactivity with chitosan, ovalbumin, cannot be used in the present invention. One or more of the highly reactive proteins can be used.

In the present invention, it is important to mix chitosan and protein uniformly in water to form a complex. To do this, chitosan is dissolved in acid, mixed with protein under acidic conditions,
Next, it is desirable to perform neutralization. If the neutralization is not performed, gelation does not occur even by a freezing treatment, and if a neutralizing agent is added to chitosan and protein in advance, partial aggregates will be generated, making it difficult to mix uniformly. Any acid can be used as long as it can dissolve chitosan, but preferred examples include acetic acid, lactic acid, citric acid, and hydrochloric acid. Adjust the pH to such an extent that the chitosan can be dissolved. The pH at the time of mixing the proteins is desirably 5.5 or lower, preferably 4.8 or lower. If the pH exceeds 5.5, the chitosan is not sufficiently dissolved, and it becomes difficult to uniformly mix the protein and chitosan.

[0008] The concentration of the protein is preferably about 1 to 30% by weight, and if it is less than 1% by weight, gelation is insufficient, and if it exceeds 30% by weight, it becomes difficult to dissolve the protein or mix it with chitosan. . The ratio of chitosan to 100 parts by weight of protein varies depending on the type of protein and its coexisting substances.
It is desirable that the amount be from 300 to 300 parts by weight, preferably from 30 to 200 parts by weight.
If it is less than 10 parts by weight, gelling does not occur, and if it exceeds 300 parts by weight, the gel strength does not change even if chitosan is added.

As the neutralizing agent, an appropriate alkalizing agent may be used, and examples thereof include sodium hydroxide, sodium bicarbonate, calcium carbonate, calcium hydroxide and the like. In the present invention, the viscous mixture after the neutralization is frozen. Before freezing, the mixture is in the form of a sol and has no shape.
After thawing, it becomes a very elastic spongy gel. There are many unknown reasons for gelation due to freezing, but the complex due to the reaction between chitosan and protein undergoes denaturation due to freezing, freeze concentration by ice crystals and immobilization of the binding site occur, and insoluble porous It is presumed that the body forms.

This gelled product can be cooked as it is and used as food like Takano tofu, or dried and used as a shock absorbing material or water absorbing material. Examples of the drying method include hot air drying, freeze drying, and microwave drying, and are not particularly limited.

[0011]

According to the present invention, an insoluble sponge-like gel can be obtained by mixing a protein with chitosan and subjecting the mixture to a freezing treatment without performing a chemical treatment such as acylation.
It can be applied to a wide range of fields such as foods and shock absorbers. Further, since only natural products are used and no special chemical synthesis is performed, a material having high safety, good biodegradability, no pollution, and excellent flammability can be provided.

[0012]

Next, the present invention will be specifically described with reference to examples. [Difference in gel strength due to difference in raw protein] 2.5 g of ISP (isolated soybean protein), 95.1 g of water, 1.2 g of chitosan (75% deacetylation degree), and 1.2 g of lactic acid were uniformly mixed with a homogenizer. Next, 0.8 g of sodium bicarbonate was added and further mixed to obtain a viscous mixture. At this time, the pH was 6.4. This mixture was allowed to stand at −20 ° C. overnight to perform a freezing treatment.

For comparison, WPC (whey protein concentrate)
And ovalbumin were used in place of the ISP, and operated in the same manner. After the obtained gel was thawed at 25 ° C., the gel strength was measured with a rheometer. The measurement was performed by measuring the stress when a disk-type plunger having a diameter of 5 mm was inserted at 6 cm / min.

As shown in the table below, those using ISP, WPC and casein had gel strength, and those using ISP had the highest gel strength.

[0015]

[Table 1] The obtained ISP gel became a sponge-like gel, and when dried by microwave, became a cushion-like porous body having extremely high porosity. [Examination of essential conditions for protein-chitosan complex gel] As shown in the table below, samples were prepared in all combinations except for one or more of chitosan, lactic acid and baking soda without using proteins. After freezing and thawing, the presence or absence of gelation was examined.
The effects of the order of addition of chitosan, lactic acid, and baking soda were also examined. The proportions of the raw materials used are shown in% by weight.

[0016]

* Indicates that it was added last As is clear from the table, when no protein was used, no combination of chitosan, lactic acid and baking soda resulted in any gelling.

Next, as shown in Tables 3 and 4, all combinations except for one or more of chitosan, lactic acid and baking soda were used except that proteins (ISP, WPC) were used. Samples were prepared, freeze-thawed, and examined for gelation. Similarly, the influence of the order of addition on chitosan, lactic acid, and sodium bicarbonate was also examined.

[0018]

* Indicates that it was added last

[0019]

Table 4 * indicates last addition As is clear from Tables 3 and 4, only those using all of chitosan, lactic acid and baking soda and adding baking soda at the end gave a hard gel.

The same results as in the above table were obtained when 2.5% by weight of casein was used as the protein. From the above results, it can be said that mixing protein, chitosan, and lactic acid with water and then neutralizing with sodium bicarbonate is essential for preparing the composite gel.

Continuation of the front page (56) References JP-A-56-131639 (JP, A) JP-A-62-287447 (JP, A) JP-B-46-10022 (JP, B1)

Claims (2)

(57) [Claims] 1. A soybean protein, whey protein or casey
A sponge-like gel obtained by mixing a protein selected from the group , chitosan, and water under acidic conditions, and then neutralizing the mixture to uniformly mix the mixture, and then subjecting the resulting viscous mixture to a further freeze treatment. 2. Soy protein, whey protein or casey
A method for producing a sponge-like gel, comprising mixing a protein selected from the group , chitosan, and water under acidic conditions, and then neutralizing the mixture to uniformly mix the resulting mixture, followed by further freezing the resulting viscous mixture.