It's quite unlikely that the malotdextrin in the various products you've tried is "processed differently". In fact, most of it is probably sourced from the same big agri-business suppliers.
As to why some products upset your tummy, and some don't...hard to say. It might have to do with other ingredients (e.g., protein, electrolytes, flavorings, etc.), or with other things you've eaten (say, that chili cheese dog and milk shake just before the ride
).
To rule out maltodextrin intolerance, just get some straight maltodextrin (available from a variety of sources, including beer and wine-making shops).
The good thing about using your own straight malto is that you can mix up however many calories you want in your water bottle (from 100-600), depending on your ride. I normally mix about 200 calories of malto per bottle, then add a dash of "Low-Salt" (for sodium and potassium), plus a bit of magnesium citrate and calcium citrate powder. For taste, I add a bit of lemon juice.
I'm pretty certain its the maltodextrin. I dont eat many commercially proccessed foods with man made ingredients due to multiple food intolorances. Most of the foods that are marketed towards celiacs in particular have limited proccessing, preservatives, etc due to celiacs being notorious for multiple food issues. I've spent the last few days comparing multiple products I use and some I've tried in the past and refuse to use. The gels were likely my first and last encounter with that sugar I intend to have. My system literally shut down and dumped everything for 36 hours on 2 occasions when I used the products with maltodextrin as the main ingredient. The 2 times I used it with the second ingredient my system was very angry and did not digest anything propperly for about 24 hours. The gel without I've had no problems with. Many of the other products I've used over the years have been all natural due to having celiac, fat dumping issues, soy intolorance, inability to proccess whey protein, etc. My daughter has an inherrited diasaccharide intolorance, they told me whoever she got it from doesnt have to have the one she has. Well mama apparently shuts down on maltodextrin. As much as being scientific would be lovely I spent 20 years with gastric dumping due to celiac, I still get it with fats. If I find a product that makes me sick I've gotten pretty good at weeding it out now through comparative analysis. Gastric dumping syndrome is not fun, and I'm not going to deliberately make my system dump my food. I had to do a fecal fat test last year and that alone was hell, why would I go home and force my system to do that? I've got a GI doc, and a GP I think they'll consider 2 dumping issues, and 2 instances of gastrointestinal distress a good sign of diasaccharide intolorance. What they choose to do from there is their choice.