A 7-month-old baby who previously didn't eat much and now refuses even…

A 7-month-old baby who previously didn't eat much and now refuses even a few spoonfuls of food, starts crying, clenches his mouth and stops eating altogether. I tried giving him mashed potatoes, apple, pear puree, vegetable puree. None of them worked. I even tried transferring it into a bottle, he ate everything. He is refusing not the food itself but the spoon (tried different sizes, both small and large, for right-handed and left-handed babies). Has anyone experienced this? What did you do to start with spoon feeding?