What is the expression of eating green plums?

When Li Jiaqi took a bite, his expression was completely out of control. Look at his expression. It's really funny. But have you noticed Yang Mi's performance? She directly took a bite of the green plum, so to speak, her expression did not change. Even she felt that the green plum was not sour at all, which was in sharp contrast with Li Jiaqi, so the green plum should be particularly sour, probably because Yang Mi likes to eat sour.