This is one of the questions i often get and as always when i feel it will be of help to many, then i will make my response into a post so that other mothers in the boat can benefit from it. You can always go to General Questions to check for updates.
How light is the pap, cereal or puree you are making for baby? Remember he has known only breast milk which is very liquid for the past six months, so your first purees to baby should be made light and not thick. Their first taste should contain more breastmilk or formula than the cereal or food so that it will be almost liquid-like. You can gradually thicken the texture as he progresses and gets used to it.