When lettuce is cut, the fracture will produce white emulsion. When the emulsion is dry, it will feel slippery and foamy when cleaning. The white emulsion produced by vegetable cracking contains saponin (dài), which is the root cause of foam.

This kind of bubble is normal. Just change the water several times and clean it. If you are not at ease, you can add some salt to the water and soak it in salt water.

Extended data

Main types of lettuce:

Lettuce can be divided into head lettuce, wrinkled lettuce and upright lettuce according to the growth form of leaves.

1, lettuce

The main feature of lettuce is that its terminal leaves form leaf bulbs. The leaves are entire, serrated or deeply parted, smooth or shriveled, and the terminal leaves form small beads, which are round or eccentric. The main varieties are Hu Da 659, Qianwei 75, Sa Lin Nasi, Beishan No.3, Mamik and Green.

2, wrinkled lettuce

The main feature of wrinkled lettuce is that it does not ball. Basal leaves, oval leaves, long petioles, wavy or deeply divided leaf margins, shriveled leaves, and clustered leaves like big flowers. The main varieties are "Hongfan" purple leaf lettuce, safflower leaf lettuce, green wave lettuce and Dongshan lettuce.

3. Lettuce erecta

The main characteristics of erect lettuce are long and narrow leaves, upright growth, full or serrated leaves, thick leaves, coarse meat and poor flavor. This variety is rare, not widely distributed and rarely cultivated in China.