Alginate gel principle is shared for free.

Alginate colloids can be prepared by extrusion into solutions of multivalent cations such as Ca2+, Sr2+ or Ba2+. Monovalent cation and Mg 2+ can't form gel, but the gel formed by Ba2+ and Sr2+ has stronger performance than that formed by Ca2+. Today, Qingdao Nanshan Biotech Co., Ltd. has to share the basic methods about the principle of alginate gel:

　　Basic methods of sodium alginate colloid;

　　1, dialysis/diffusion method

　　This is one of the most commonly used methods. When using this method, the aqueous solution of sodium alginate forms colloid after contacting with calcium ions from outside. The colloid formed in this way is generally uneven, because a part of sodium alginate that comes into contact with calcium ions early solidifies and shrinks after gel formation, and its solid content is higher than that of the colloid formed later. The lower the concentration of calcium ion, the smaller the relative molecular weight of sodium alginate, the higher the concentration and the higher the content of G acid, the stronger the heterogeneity. Because the gelation rate is limited by the diffusion rate of calcium ions, this method has limited application and can only be used to prepare thin sheet materials.

　　2. In situ method

　　This method generally uses calcium salts with low solubility or calcium ions coordinated with other materials. After fully mixing with sodium alginate, weak acid with slow release effect is added. Calcium ions are released under the action of acid and then combine with alginic acid to form colloid. The colloid formed in this way is very uniform, and the colloid which is not fully crosslinked, that is, the mixed colloid of calcium and sodium alginate, can also be prepared.

　　3. Cooling method

　　Because calcium ions in the solution can't combine with alginic acid at high temperature, the colloid of alginic acid can be prepared by mixing calcium ions with sodium alginate at high temperature and cooling.

　　4. Crosslinking method

　　This method uses epichlorohydrin, which is crosslinked by Xiang group in alginic acid molecule. Alginate loses its solubility after crosslinking and forms colloid. The colloid thus formed has stable structure and high water content, and can absorb 50-200 times of dry weight.

　　The properties of colloids formed under different processing conditions are quite different. The following are some basic rules about alginate colloid, which can be used to change the compactness and setting time of the gel:

　　(1) When the content of calcium chelate increases, the rigidity of gel decreases. On the contrary, when the content of calcium chelate decreases, the rigidity of gel increases. However, if the amount of chelating agent is too small, a gel with small particles is formed.

　　(2) The amount of calcium added is reduced, and the generated gel is softer; With the increase of calcium content, the gel formed is stronger. However, too much calcium will produce granular gel and even calcium alginate precipitate.

　　(3) In the acidic gel system, adding some slow-soluble acid can accelerate the solidification of the gel when its acid content increases, but it may produce granular gel.

　　(4) When the concentration of soluble sodium alginate increases, the generated gel becomes firm, but its structure may be uneven. The higher the concentration of sodium alginate, the more brittle the gel obtained and the sharper the edge of its fragments.

　　(5) As the amount of calcium added approaches the stoichiometric amount required for complete reaction with sodium alginate, the dehydration shrinkage tendency of the gel obtained increases.
　

　　The following is a schematic diagram, and calcium ions play the role of crosslinking:

　　

　

　　This small experiment is relatively safe, and the raw materials are not toxic. If it is food-grade raw materials, it can also be used for cooking, so you can try it at home if you have the chance. The formula I have seen is roughly that 0.5 ~ 2g of sodium alginate is dissolved in 100ml of water (purified water is better), and the same quality of calcium chloride is dissolved in another 100ml of water, and then the colors are adjusted according to preferences. Different places have different opinions on the concentration, so you can adjust it yourself. The dissolution of sodium alginate is slow. You can use an electric stirrer to stir and accelerate the dissolution, and then let it stand for a while to defoam.

　　Generally speaking, sodium alginate can be dropped into the calcium salt solution with a dropper or injected with a syringe, so that small particles like "fish eggs" or long gels can be obtained. The middle is often not completely solidified, so the effect of "Explosicum" can be made (this feature will be used in molecular cooking).

　　

　

　

　　This looks good, but it is difficult to make a larger gel "water polo" by this direct pouring method. I have tried to put sodium alginate in a spoon and slowly put it into a calcium salt solution before, but I can't keep the regular shape no matter what I do, and I only get something fascinating in the end … …

　　

I've had enough of this strange thing … … )

　

　　Recently, however, I read some molecular cooking tutorials and got the correct way to open alginate gel balls. Today, let's share the results _ (:з "∠ )_

　　First, prepare the calcium salt solution you need (molecular cooking will flavor this part of the solution, such as making it with cocktail drinks, and we will use calcium chloride solution directly here), and then put it in an ice cube for freezing and shaping. Next, prepare the sodium alginate solution, take out the calcium salt ice cubes, completely immerse them in the sodium alginate solution for several minutes, and then carefully remove them and wash away the excess alginic acid and ions with clear water.

　　Note: These raw materials are safe enough, but if you want to make food, you must make sure to use food-grade raw materials. My sodium alginate is not very pure, so it can't be used for cooking.

　　Ice cubes soaked in sodium alginate:

　　

　

　　As the ice melts, the calcium salt on the surface comes into contact with the alginic acid outside, so it becomes gel and fixes the shape ~

　　Wash in clean water:

　　

　

　　Pretend to put on a plate, I am already very satisfied with this result _ (:з "∠ ) _ At least everything that comes out of this way is shape controllable.

　　

(Spherical and hemispherical molds are better, and heart-shaped molds are used here.)

　

　　Theoretically, as long as there is a suitable mold and the operation is careful enough, larger water polo can be made ~ The water polo made by this method also has a better "Explosicum" effect.