I'm looking for a dietary fiber or a mix of dietary fibers (and other ingredients which act like dietary fibers such as sugar alcohols) with really low (even zero) food calories that I can create a crunchy (as in chips) or crusty (as in bread) texture.   Please think of molecular level fibers not as in fiber-rich food. For example a common dietary fiber is Inulin (which is a fructan) and can be used as a sweetener. Another one is Glucomannan which is used as a thickener and a gelling-agent. Both of these have no calories.  I thought of using Isomalt, which to some extent acts like a dietary fiber, to make hard candy, but I think it's not going to be as low calory as I want since it's just half the calories of sugar or flour. I'm looking for recommendations to achieve such a texture, which could be considered suitable for a calorie controlled diet.  As a response to the close requests:   I'm not asking for a recipe, the question is about ingredients and techniques I don't think it's broad for the following reasons:   I'm asking for a very specific texture and how to achieve it. I don't know of any combination that could result in such a texture with low calories. Think of a combination before voting close for this reason (better yet, write it on the comments :))   
Kiwi.  Don't knock it until you try it. It will have a similar acidity and texture to pineapple. Use ripe kiwi and maybe a touch extra lime juice! 