I have exactly this issue - neither of my girls will touch jars, even the organic just pure veg ones - somehow they just know. If I am going somewhere that it is unpractical to heat up stuff, I take fresh stuff that I can quickly whip up at meal time such as a ripe banana and some fromage frais in a cool bag, one of those mini avocados you can now buy in packs from Tescos, a really ripe pear (when a bit older) etc. etc. Most of these type of things only take seconds to mash up in a bowl and IMO is better than having to resort to jars that mine spit out anyway. (When starting weaning I used to take out the baby Danone from "4 months" pots and baby rice with milk, moved onto the banana etc. a few weeks later on)