> You get to "ultra-processed" simply by making things shelf-stable, and shelf-stability isn't an actual health problem (kind of the opposite).

I would point out that many whole foods are generally shelf-stable (over at least weeks, if not months) without requiring the introduction of chemical stabilizers that don't otherwise "belong."

Chemical stabilizers are generally needed for shelf stability in ultra-processed foods, because of one of the other defining characteristics of ultra-processed foods: their matrix has been disrupted (or constructed anew) such that the food is now highly labile (biochemical term: "labile organic matter"), i.e. very easy to break down into nutrients. Which applies not only to you breaking such foods down in your gut, but also to bacteria and fungi breaking these foods down on the shelf.

And as it so happens, because these foods are labile, any such nutrients that do come from breaking down the food, come very quickly. Labile carbohydrates are high-glycemic-index insulin-spiking carbohydrates. Labile fats are atherosclerosis-inducing fats. Etc.

Your body evolved to process (metabolize, remove from circulation, etc.) metabolic inputs in an environment where most available foods were the opposite of labile (a.k.a. recalcitrant organic matter). So most meals would give a slow/gentle level of metabolic throughput; with rare spikes of higher throughput from the rare natural labile food, and then plenty of low-throughput time to recover from such events. Your body didn't evolve to be able to deal with getting high-throughput metabolic input spikes from every meal.

And this is why the the presence of chemical stabilizers in a food is actually a very helpful criterion in the definition of "ultra-processed food"! The necessity of stabilization tells you that the food is likely labile (as otherwise, why would they have needed to stabilize it?) — and therefore is unhealthy to be consumed on a continuous basis. (Unless it's milk and you're a baby.)

But note that the stabilizer isn't itself the problem. Bread is ultra-processed even without a stabilizer, because bread is a labile food with weak matrix integrity. The bread you bake at home is ultra-processed; you're the one who ultra-processed it!

The "rules" for UPFs don't assert home-baked bread as a UPF, but that's because the point of the UPF designation is to label commercial foods, and more specifically, to draw a hard-line boundary based on objectively-measurable characteristics that industry players can't argue with or lie about. And lability / matrix integrity, while quantifiable, isn't something with a clear objective way to reduce it to a single number†; so any definition of UPF based on lability would result in endless arguments/pushback from industry players insisting the FDA is "calculating it wrong."

But in your own personal life, the definition of "ultra-processed" you should be carrying around in your head and evaluating foods by, should be one that includes lability.

† (Instead, lability a high-dimensional measurement of how efficiently any single digestive enzyme, and/or any specific combination of enzymes, and/or any enzyme paired with a cofactor [e.g. a bile salt], will break apart the given food's matrix to release bio-accessible nutrients.)