"Aging" is the reverse process of "gelatinization". The essence of the "aging" process is that during the gelatinization process, the dissolved and expanded starch molecules rearrange and combine to form a structure similar to natural starch. substance. It is worth noting that the aging process of starch is irreversible, and it is impossible to return to its pre-aging state through gelatinization. Aged starch not only tastes worse, but its digestion and absorption rate also decreases.

The aging of starch is firstly closely related to the composition of starch. Starch containing more amylose is easy to age and is not easy to gelatinize; starch containing more amylopectin is easy to gelatin and is not easy to age. Corn starch and wheat starch age easily, while glutinous rice starch ages slowly. The moisture content value that causes aging.

Factors affecting starch aging

1. Type of starch. Amylose ages more easily than amylopectin; amylose with a small molecular weight ages easily; amylose with a degree of polymerization between 100 and 200 is the most susceptible to aging.

2. Starch concentration. The concentration of the solution is high, and there are many opportunities for molecular collisions, making it easy to age. However, when the moisture content is below 10%, starch is difficult to age. When the moisture content is between 30% and 60%, especially around 40%, starch is most susceptible to aging.

3. Types of inorganic salts. Inorganic salt ions can hinder the orientation of starch molecules.

4. pH value of food. When the pH is between 5 and 7, the aging rate is fast, while when it is acidic or alkaline, the aging is slowed down due to the same charge.

5. Freezing speed. When gelatinized starch is cooled slowly, aging will be aggravated, while quick freezing can reduce the degree of aging.

6. The temperature. The optimal temperature for starch aging is 2 to 4°C. It is not easy to age above 60°C or below -20°C. However, aging will still occur when the temperature returns to normal temperature.

7. The influence of deposits. Lipids and emulsifiers can resist aging; polysaccharides (except pectin), surfactants or polar lipids with surface activity are added to bread and other foods to extend the shelf life. Completely gelatinized starch is cooled naturally at a lower temperature or slowly dehydrated and dried, which will cause hydrogen bonds to recombine between the starch molecules, causing the water molecules in the starch latex to gradually escape, resulting in water precipitation.

At this time, the starch molecules are rearranged into orderly crystals and condensed, and the starch milk ages back to form a gel. This kind of starch that regenerates into crystal after gelatinization is called aged starch. Aged starch is difficult to rehydrate and harden, so it is difficult to digest rice that has been cooked, roasted and then cooled. Simply put, starch aging is the crystallization process of gelatinized starch molecules forming regular arrangements.

Source of the above content: Baidu Encyclopedia-Starch Aging