Imagine you have some food (e.g. 100g of mushrooms) and you mix them to a soup. To what degree the percentage of (insoluble) fiber is affected? I don't mean the question "raw" vs. "cooked", just the fiber-contents of the 100g mushrooms before and after mixing.
I am not able to find any information about this except for some unclear statements, e.g. here:
David Katz, director of the Yale-Griffin Prevention Research Center at Yale University … wrote that while the blending process “certainly [has] an effect” on fiber, there has been little research documenting precisely how much it breaks down insoluble fiber and reduces the benefits of fruit. He added, “Let’s face it: Chewing grinds up fiber to some extent, too.” That said, “we have a fairly solid basis for saying: Whole food is best,” he wrote.