How to prevent starchy foods from aging

1. Temperature

Ripening of starchy foods must occur above the starch gelatinization temperature. Different types and sources of starch have different gelatinization temperatures. Although different types of starch have different gelatinization temperatures, starch aging begins during the process of slow cooling after starch gelatinization, and generally does not occur before starch gelatinization. Aging occurs. The general rule of the relationship between aging and temperature in most starchy foods is that starchy foods are generally not prone to aging when they are slightly below the starch gelatinization temperature and below the starch freezing temperature. If starchy foods are placed between the above two temperatures, the aging degree of starchy foods will increase as the environmental temperature continues to drop, and the aging speed will gradually accelerate. The optimal temperature for aging to occur is approximately between 2℃ and 4 ℃.

2. Moisture

Starch foods contain a certain amount of water. Volatilization and redistribution of water promotes aging. The amount of moisture will affect the speed of starch aging. When starchy foods contain 30%-60% moisture, starch is most likely to age; when the moisture content is above 70%, the starch in the food is gelatinized more thoroughly and the degree of aging is relatively slow; when the moisture content is less than 10%, the food is less prone to aging.

During the aging process of starchy foods, most foods will be accompanied by hardening, and some foods can even become farinaceous after aging. These phenomena are attributed to the fact that when processing starchy foods, a certain amount of water always needs to be added. After artificial mixing or kneading, when heating, the starch particles begin to expand, the starch molecular structure is loose, and water molecules enter the starch molecules in the food. and associate with them. When food is made into cooked food, during the cooling and storage process, the hydrogen bonds between starch molecules and water molecules are very unstable and easy to break, resulting in the formation of stable hydrogen bonds between starch molecules. During this process, some water is squeezed out of the food, causing syneresis, causing starchy foods to harden and become crispy, and the taste is quickly reduced.

3. Starch composition

Most natural starches can be divided into long-chain amylose and tree-branched amylopectin. These two different structures of starch molecules are present in general starch granules. Amylose does not dissolve in cold water, but can only gradually dissolve in water through pressure or heating to form a more viscous colloidal solution. However, the nature of this colloidal solution is very unstable and is very easy to precipitate when left standing; amylopectin is easily soluble in hot water to form a high-viscosity colloid, and this colloidal solution is also stable after cooling.

4. Protein

Generally, starchy foods have a small amount of protein, and the aging speed of starchy foods during storage is also related to the protein content in the flour raw materials. The existence of gluten prevents the mutual gathering of starch molecules, which is not conducive to the formation of microcrystalline bundles. In addition, during the aging process of starchy foods, when the originally loose and chaotic starch molecules transform into beta-converted starch, some water will be squeezed out. Gluten protein can absorb a certain amount of water and act as a storage of water. The role of this also delays the aging of starchy foods to a certain extent.

5. Emulsifiers

Emulsifiers are used as anti-aging agents because they can increase the softness of starchy foods. The emulsifier connects with the amylose inside the starch granules to prevent the amylose from escaping, so it does not enhance the strength of the internal tissue of the freshly made starchy food. On the other hand, emulsifiers do not have the same effect on amylopectin, so they will still cause the hardening of the internal tissue during storage and will not slow down the movement of water from the inside of starchy foods to the outer skin, so emulsifiers can be used as a reinforcing agent for dough and a softening agent for the outer skin.

After aging, starch is as difficult to be digested and absorbed by the human body like raw starch. To sum up, the main way to inhibit starch aging is to prevent or avoid the re-formation of intermolecular hydrogen bonds between gelatinized α-starch molecules to maintain the quality of starch foods. (Editor in charge: Tian Tian)