Processed food isn't food at all, it's a 'food product' make to resemble food.
Hint: the preservative is "Citric Acid", also known as lemon-juice. A wee bit more acidity negates any chance of botulism (which just barely can live in the PH of Tomato-acid. But add a squeeze of lemon to it and make it slightly more acidic and this rare bacteria is taken care of).
Otherwise, you're looking at just mashed up tomatoes + a squeeze of lemon inside of a can. No joke, nothing else is in there.
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The other aspect of "preserving" is the airtight can, which prevents other organisms (other bacteria, mold, fungus) from entering the can.
Any tomato paste can you find is basically using this technique.
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Other canned veggies are even more pure. Canned corn is just heated (at the factory) to a temperature that kills botulism spores. A lot of cans add salt for flavor, but you can easily buy salt-free cans and get pure corn if that's your preference.
Unfortunately, these 'ultraprocessed' journalists commonly refer to canned corn as processed food.
Doritos, frozen pizza, cup noodles are clearly unhealthy. And I think most reasonable people know that.
But these 'ultra' journalists have... Questionable... discussion points when you dig into the articles.
I think that's an unreasonable assumption, cup noodles sure, but for chips and frozen pizza it's obviously a question of quantity and people who work long hours end up forced to resort to these to just get calories in at the end of the day.
The problem with Chips is that they're starch, and in the USA, we overeat starches. There's pretty much no reason to be snacking on starch.
Instead, you should snack on fat and fiber: nuts and fruits. Dehydrated fruits are as easy to store and eat as any chips (Raisins, Pineapple) and will instantly increase your dietary fiber intake. Canned / Processed fruits are extremely easy and incredibly healthy. Apple Sauce, canned pineapple (since its cooked, no worries about it dissolving your tongue), canned apricots, canned peaches. You've got a lot of options for a quick-and-easy fruit snack that's as convenient as chips.
Nuts are a high energy source of healthy fats. Almonds, Peanuts, Cashews, Pistachios. Plenty of good stuff, and they balance well with fruits (fruits are low on fat/lipids/protein, nuts are high on fat/lipids/protein). There's also a different set of vitamins you get from them, so the variety is key to healthy eating.
In theory: if you were low on starch for some reason, Potato chips (or corn chips) probably would be fine. But... that's just not what the typical American has problems with.
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Just watch your sugar intake. In the USA at least, a lot of these canned / dehydrated fruits have added sugar in them (yeah, we like our things sweet).
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Frozen stuffs just have too much sodium in my experience. Frozen Pizza doubly-so, because cheese often is made with amounts of salt. Still, I understand the need of a convenient dinner every now and then if you're busy, but definitely don't make a habit of it IMO.
The tomato, to begin with, I'm using this[1] as the source for nutritional values, we've got 70 calories with 5.5g of sugar (tomatoes are pretty sweet after all), 0 mg Sodium - we also have (for our DAVs) 97% Vitamin C, 11% Vitamin A, 6% Calcium - all that is in 1 tomato
For the Hunt's I'll use this[2] source where a small can has 10 of these servings, but I'll double the serving size to make calories match up. We've again got 70 Calories (due to my manipulation) with 8g Sugar (about 50% more than a raw tomato) 50mg Sodium (2% DAV) with no Vitamin C or A but with a bit of Potassium and Iron (12% each of DAV).
Next up is Compliments Tomato Sauce source[3] - this is actually much less calorie dense so I'm going to multiple the serving size up to five cans (or 1 1/4 cups of sauce) which is 75 Calories. The ingredients are actually just: Water, Tomato Paste, Salt, Citric Acid, Onion powder, Dried Garlic and "Spice". We've got 10g Sugar here, possibly some added under "Spice" or just concentrated tomato, 1200mg Sodium (50% DAV) along with 10% Vitamin A, 40% Vitamin C, 10% Iron
And, lastly, Unico Pizza Sauce[4] this comes in a 1/4 cup can that I'll quadruple to match Calories. Ingredients wise we've got Crushed Tomatoes, Water, Salt, Modified Corn Starch, Sugar, Spices, Dehydrated Garlic, Citric Acid. We have 12g of sugar, 1280 mg Sodium (50% DAV), 8% Vitamin A, 40% Vitamin C and other bits.
I went through the above mostly to highlight that yes, there are "pure" canned vegetable and fruit options, they often only mildly miss out on nutrition (like the complete lack of Vitamin C in Hunt's Tomato Paste) but there are also a lot of nearby options that are loaded down with other crap.
Just a note - the sources below are for the internet. I actually initially read each one off the label but I wanted to show my work and sourced them from the internet - I actually ended up recalculating a few since I could only find US nutritional facts which are noticeably worse than Canadian products.
1. http://www.fitbit.com/foods/Tomato+Raw+Beefsteak+Large+13+oz...
2. https://smartlabel.labelinsight.com/product/6119604/nutritio... (linked on Hunt's website)
3. https://www.fatsecret.ca/calories-nutrition/compliments/toma...