Does peeling, cooking or pureeing fruits and vegetables change the FODMAP content? Short version: this common questions does not have a good answer at this time.
Traditional nutrient database show little difference between cooked and raw fruits and vegetables. Published data from more complete FODMAP analysis has not yet explored many of these subtler variations in fruit and vegetable preparation.
It makes sense that peeling and cooking would affect certain FODMAPs in food, but there isn't enough info to be specific except in a couple of cases. We know that fructans in vegetables are water soluble and leach out into the cooking water, which is why onions and garlic in a soup or stew are potential problems even if you pick them out. We don't know specifically how many grams change, though. This effect could be useful for vegetables like broccoli and cabbage, I would think, suggesting that boiled and drained vegetables would have less fructans than raw or sauteed, but there is no data to prove it.
Peeled v. unpeeled apples and pears were analyzed in two studies by researchers at Monash University, Australia. Overall, peeled apples and pears by % weight actually had slightly more fructose than unpeeled (we might conclude fructose must be in the flesh of the fruit rather than the peel). Two varieties of apples were analyzed for polyols, peeled v. unpeeled . Peeled Granny Smith's had slightly more sorbitol than unpeeled. Peeled Pink Lady's had slightly less sorbitol than unpeeled. No generalization can be drawn, apparently. I have not seen any FODMAP data on cooked v. uncooked fruits.
It is hard to imagine any way that pureeing would change the fructose or polyol composition of fruits or vegetables. I am not aware of any specific data about whether pureeing can break down fructans in vegetables. My guess is that it can't break the molecular bonds of fructose links in fructans. Even if it could, would that be an advantage? Breaking down fructans, for example, would just mean the puree would be higher in fructose, which is also a FODMAP! (Might be helpful for someone without fructose malabsortion.)
What about food preparation methods that involve fermentation? Theoretically, the bacteria and/or yeast in fermented food could reduce the FODMAP content of the food before you eat it (instead of after you eat it, in your gut!). So far, we know that sourdough breads have less fructans than breads leavened with baker's yeast. The traditional two-day sourdough fermentation is what counts, not the word "sourdough" in the name or the flavor of the bread. These will usually be artisan breads from specialty bakeries. One clue to identifying a bread made by the sourdough process: there will be no baker's yeast in the list of ingredients.
Those are my thoughts on the subject, what about yours?