The indicator of purple cabbage will turn red when it meets acidic substances and green when it meets alkaline substances. Purple cabbage contains a lot of anthocyanin, which is a water-soluble plant pigment and exists in cell fluid.

The color of anthocyanins changes with the pH value, and the acidity is red and the alkalinity is blue. White vinegar is acidic, baking soda solution is alkaline and water is neutral. Therefore, the purple cabbage juice turns blue when dropped into baking soda solution, blue when added with white vinegar, and purple when dropped into water.

Matters needing attention in the experiment of acid-base change of purple cabbage juice

Because the cold tolerance of Chinese cabbage is stronger than that of Chinese cabbage, it can enter the cellar a little later than that of Chinese cabbage, and it can be stored in the cellar by stacking, shelf storage and basket storage. Stacking can be made into triangular stacking and rectangular stacking, and it is best to store them on shelves. Each shelf can be loaded with two or three floors, which is beneficial to ventilation and heat dissipation. Stacking in a basket is also good for ventilation, and the effect is good.

Dig 1.5 to 2.0 meters wide on the land with high terrain and good drainage, depending on the local climate and stacking layers, it is required that 1.2 to 1.5 meters deep, and 2 to 4 layers of Chinese cabbage can be stacked in the ditch. For those Chinese cabbages that are not yet strong, cover them with straw, and then gradually cover them with soil according to the change of external temperature to prevent freezing injury.