Abstract: The fruit hardness degree of tomato and the factors affected were studied during the shelf phase with Baili, Katelina, R144, new tomatoes types all having hard fruit flesh and Gailun, TF997, TF998, new varieties breeded in Xingguang Seed Co.Ltd., as experimental materials, and with Lisheng Num. 8 as a check material. The results show that the fruit hardness degree and flesh of fruit hardness degree are the index to evaluate the lifespan of the fruit during shelf phase. The content of the insoluble pectin and the soluble pectin are the direct factors affecting both of them. Moreover, the fruit hardness degree and the flesh of fruit hardness degree have a positive correlation with the content of insoluble pectin as well as they have a negative correlation with the content of soluble pectin, both of them at a very significant level. PG and PE are the indirect factors affecting the softening of the fruit.

Key words: tomato, hardness degree, pectin, polygalacturonase (PG), pectinesperase (PE)