Toss a handful of wheat at an open flame and you’ll get some singed wheat.
Toss a handful of finely powdered flour at an open flame and fwoom.
Insoluble fibers like wheat husks might act as fiber at a particle size like you get from whole wheat bread. If you turn it into a fine powder, the FDA might continue to believe that it is an insoluble fiber so far as the nutrition panel goes, but I am skeptical that we haven’t changed some of the fundamental aspects of what makes it operate as a good thing for your gut in that process.
When you powderize something, you have massively increased its surface area relative to its volume. What might formerly have been resistant to digestion might now become digestible; what formerly might have acted like a little wall between your food and your intestinal wall, haphazardly, protecting some nutrients so that they make it lower into your gut will no longer be able to do so; if there is any form of scraping roll that insoluble fibers play in keeping your intestines clean (I don’t know that there is) that might go away.
Until someone who knows better comes along:
A search term that returns academic literature suggesting that it has been studied is:
insoluble fiber particle size
Given that all insoluble fiber is not created equal (fermentable, phenolic, etc., and apparently size too) it appears to be complicated.
AIUI most of the scraping, shielding, is due more to gelation, not the action if individual particles, but I’m out of my depth here and may but have the latest poop on how fiber works.
Reduce a log to sawdust and toss handful on a fire and it also goes “fwoon”.
As you mentioned, all that is a function of surface area.
Something like wheat husks are mostly cellulose, which are indigestible by human biology at any size down to individual molecules. The chief differences with the powdered version are that powders are more easily suspended in liquids/combined with foods to make consumption easier, and fewer identifiable bits in your feces.
Powdering indigestible fibers do not make them digestible because their chemistry hasn’t changed and digestion is largely about chemistry. Increased surface area doesn’t change the chemistry.
ISTR reading an article sometime in the early 1990s that referenced a study where researchers fed test subjects insoluble plastic that had been milled to the same physical size/shape as insoluble fiber typically was, and checked the results. Apparently the role of insoluble fiber in the digestive tract is a physical one- it irritates/stimulates the colon or something based on its size/shape/texture and acts as a laxative.
Take a flawless golf ball sized salt crystal, add into a pitcher of water, start timer, stir until fully dissolved, stop timer.
Take finely powdered salt of equal weight as the weight of your previous golf ball, add into a pitcher of water of equal quantity, start timer, stir until fully dissolved, stop timer.
But salt is soluble in water. Try the experiment again with something insoluble in water, like a steel ball bearing and a teaspoon of finely powdered steel. What happens then?
I didn’t take it as intending a close analogy to digestion, I took it as making a more general point that changing the physical structure of something, even if it’s the same substance, can dramatically change its properties.
So we need to understand exactly what fiber is doing in digestion, and how it’s doing it. I’m certainly not an expert, but I know one relevant example. When eating “whole” foods with structurally integrated fiber, the fiber slows the digestion process, lowering the glycemic index. So that would be one situation where adding powdered fiber to processed food would probably not have the same effect on glycemic index.
But there are different kinds of fiber, and I think a number of different processes, so it’s not going to be a simple answer.
I know what you’re trying to say, but the terminology is not quite right - it obviously changes the physical chemistry, which is always a critical aspect of biochemistry.
It will corrode faster. If small enough, it will suspend instead of sitting on the bottom of the beaker. And the surface area has been increased by many orders of magnitude. I’m not sure what the confusion is here.
Swallow a chunk of wood and you’ll poop a chunk of wood. Swallow finely powdered wood and the cellulose and lignin will gel in your gut.
I’ve already noted there’s literature about this. It seems people are posting without taking a look for themselves.
OK, what if it’s a pile of powdered gold vs a lump of gold? Neither will corrode, will it? And the powdered wood may gel (I have no idea if it will or not) but it won’t dissolve, will it?
It was conceivable that cellulose was practicably insoluble under traditional preparations rather than truly insoluble. It is, after all, an organic molecule that is digestible by other mammals (e.g. cows). I didn’t want to take the name at face value, given that.
If small enough, gold will suspend (not dissolve) and look pretty. Often pink, depending on the size. A colloidal suspension can be clear (to the eye) and colorless or clear and colored. It can also be cloudy.
I’m not sure what point you’re trying to make. The chemical reactions (or lack of them) undergone by the fiber itself are not all that matters. The nature of the physical structure formed by the fiber is important in itself; and it can certainly influence the reaction rate of anything that is reactive.
And lots of insoluble fiber is reactive. Or at least not inert. Some is fermentable by gut flora. The surface chemistry dictates gel formation. It adsorbs other molecules. Higher surface area increases phenolic extractability and bioaccessibility, etc.
For the purposes of this thread, the question is whether the fiber will continue to have its properties that allow it to act as a “fiber” rather than, e.g. being broken down into something from which energy can be extracted, fermented, etc.
I’m not sure if that would be better termed “soluble”, “digestible”, or “fermentable”.
I am finding a number of sources saying that cellulose is partially digested in humans. I also see one source which says that they have found greater levels of digestion (by bacteria) in direct correlation to the duration that their cellulose was reduced via ball mill.
Cellulose is NOT digestible by cows or other ruminants. It is digestible by symbiotic bacteria that live in their guts. The cows then utilize what is essentially bacteria poop. Those same bacteria do not live in the guts of humans. Cellulose is not digestible by humans.
For the record - termites can’t digest wood, either. It’s digested by symbiotic bacteria that live in their guts. Termites also live on bacteria poop. Again, that bacteria does not and can not live in human guts.
ETA: OK, it’s possible for a teeny bit to get broken down in a non-ruminant, non-termite gut, but I doubt very much it’s enough to matter.