The quality of rice will decline if it is stored for a long time. This is mainly caused by colloid aging, decreased enzyme activity and decomposition.

New rice and old rice can be identified by the following aspects:

1. Look at the hardness: the hardness of new rice is greater than that of old rice-the greater the hardness of rice, the higher the protein content and transparency. You can tell whether it is new rice or old rice with a bite of your teeth.

2. Look at the belly white: The belly white of new rice should be milky white or light yellow, while the color of old rice will become darker or even brown.

3. Look at the yellowing of rice grains: The yellowing of rice grains is caused by the chemical reaction of some nutrients in rice under certain conditions or the proliferation of microorganisms in rice grains. Such yellow rice will affect the flavor and taste of rice. The new rice grains are even and shiny, and the surface of the rice grains is gray powder or old rice with white ditches. The more white ditches and gray powder, the older they are. It was old rice who had a musty smell and was eaten by insects.

4. Insert the hand into the rice bag or rice barrel, and observe the surface of the hand after pulling it out. There is a little white flour, which proves to be new rice after being lightly blown, and old rice or inferior adulterated rice with sludge that cannot be lightly blown.

5. Moisture and fragrance: The moisture in the new rice grain is more than that of the newly ground rice by Chen Gu, and it feels sticky when pinched by hand. The freshest rice can even be kneaded into a ball, while old rice is as stiff as loose sand. The new rice smells like rice, but the old rice doesn't.