What bleached flour actually is, and why it is in your tortillas

Two bags of flour tortillas sit on the same grocery shelf. In Tallow, one scores 5 out of 100 and the other scores 95. They cost within a couple of dollars of each other and they do the same job at dinner.

The gap opens up on the very first word of the ingredient list. One of them says bleached.

The two labels, side by side

Here is Old El Paso Flour Tortillas for Soft Tacos and Fajitas, copied from the manufacturer's own product page:

Enriched Flour Bleached (wheat flour, niacin, iron, thiamin mononitrate, riboflavin, folic acid), Water, Palm Oil, Glycerin. Contains less than 2% of: Baking Powder (sodium aluminum phosphate, baking soda), Mono and Diglycerides, Salt, Potassium Sorbate and Calcium Propionate (preservatives), Fumaric Acid, Hydrogenated Vegetable Oil (soybean, palm, and/or cottonseed oil), Dough Conditioner (salt, wheat starch, enzymes).

And here is Vista Hermosa Flour Tortillas, from the Whole Foods listing:

Organic Wheat Flour, Non-GMO Cassava, Avocado Oil, Salt, Water.

Five ingredients against roughly seventeen. We should be precise about one thing: a tortilla is often described as needing only four things — flour, water, fat, salt — and Vista Hermosa actually uses five, because it adds cassava. That is still five recognizable foods.

The 5 and the 95 are Tallow's own scores, not a lab result. They reflect what is on the label, not a measurement of what is in the package.

What "bleached" actually means

It is not a marketing word. It is a regulated process, and the FDA spells it out in 21 CFR 137.105, the federal standard of identity for flour. That regulation lists the permitted bleaching agents and requires that the word "Bleached" appear in the name of the food when they are used.

The workhorse is benzoyl peroxide — the same compound sold over the counter for acne. It has been permitted in American flour since the 1920s. BAKERpedia's technical write-up explains that it is applied at roughly 0.001% of flour weight and strips most of the color out within about 24 hours.

Freshly milled wheat flour is pale yellow, from carotenoid pigments. Left alone for a few weeks it oxidizes and whitens on its own, and the gluten matures. Bleaching does in a day what aging does in a month, which is a genuine industrial advantage. What it also does is oxidize the pigments and some of the vitamins along with them.

Why Europe said no and America did not

A 2025 review in Food, Nutrition and Health, Flour bleaching: over a century of health risks and controversies, traces the practice back to 1901 England, where it was invented to mimic naturally aged flour. The authors write that these agents degrade vitamins E and A and generate reactive free radicals, and they note that the practice is banned in the EU, the UK, China and Turkey while the United States still permits it.

That review is pointed in its framing, so treat its strongest language as argument rather than settled consensus. But the regulatory split it describes is a plain fact you can verify yourself: American flour bags say "bleached," and European ones do not, because in the EU there is no authorized flour bleaching agent to use.

We are deliberately not repeating a claim that circulates with this one, including in our own short-form video: that Canada bans flour bleaching. We could not verify that, so we are not asserting it. EU, UK, China and Turkey are the ones we can stand behind.

The 1914 ruling that still shapes your flour

This is the part that explains why the two continents diverged.

In 1914 the Supreme Court decided United States v. Lexington Mill & Elevator Co.. The government had seized 625 sacks of flour whitened by the "Alsop Process," which ran nitrogen peroxide gas through the flour and left behind nitrites. The trial court told the jury that adding any amount of a poisonous ingredient violated the 1906 Pure Food and Drug Act.

The Supreme Court disagreed. It held that the statute did not condemn flour merely because a poisonous substance had been added — the government had to show that the added substance may render the food injurious to health.

That is a reasonable legal rule. It is also the reason the American default became "permitted until proven harmful" while the European default drifted toward "not permitted until proven necessary." A century later you can read the consequence on a tortilla package.

What we are not claiming

You will find articles saying bleached flour contains alloxan and that alloxan gives you diabetes. Here is the honest version.

Alloxan is real, and it does show up. A 2017 LC-MS/MS study reported the first detection of alloxan in bleached flour, finding it in about 24% of samples at a mean of roughly 0.95 mg/kg, concentrated in cake flour. So it is not invented.

The diabetes leap is where it falls apart. Researchers use alloxan to induce diabetes in rodents by injection, and rodent beta cells are unusually sensitive to it. As McGill's Office for Science and Society lays out, human beta cells are far more resistant, and there is no evidence that dietary alloxan causes diabetes in people.

We would rather lose the scarier version of the story than publish something we cannot defend. The case against bleached flour does not need it.

Propylparaben, the other one on tortilla labels

Old El Paso does not use propylparaben. Plenty of tortillas do.

It is a preservative that stops mold, and NPR covered its presence in American tortillas back in 2014. The Environmental Working Group has documented it in dozens of US grocery products, including packaged corn tortillas from brands like La Banderita and Chi-Chi's.

The regulatory picture matters here:

AB 418 was the first US law to ban a paraben from food. The concern is endocrine activity: propylparaben behaves as a weak synthetic estrogen in laboratory work.

The rest of that Old El Paso list

Bleached flour is the headline, but scan the rest and a pattern shows up. Hydrogenated vegetable oil (soybean, palm and/or cottonseed). Mono and diglycerides, which are fats that function as emulsifiers. Sodium aluminum phosphate in the baking powder. Glycerin, fumaric acid, potassium sorbate, calcium propionate, and an enzyme dough conditioner.

None of these is banned in the US, and none of them will hurt you at dinner tonight. They are there to make a flat bread survive weeks in a plastic sleeve on a shelf. That is the actual trade: shelf life bought with chemistry, at a price that never appears on the receipt.

How to shop this

1. Read the first ingredient. If it says "bleached," you know the flour was chemically oxidized. Unbleached is on the same shelf and usually costs the same.
2. Count the list. A tortilla that needs seventeen ingredients is solving a logistics problem, not a cooking one.
3. Check for parabens by name. Propylparaben is spelled out. It is not hidden behind "preservatives."
4. Watch the fat. Hydrogenated oils and palm oil are the standard tortilla shortening. Avocado oil, butter, lard and tallow all work and all show up on cleaner labels.
5. Refrigerate the good ones. Short-ingredient tortillas mold faster. That is the point, and it is manageable.

Tallow scans the barcode and scores what is actually on the label, so the difference between a 5 and a 95 takes two seconds in the aisle instead of a chemistry degree. Try it on your tortillas.

Ingredient lists in this post were taken from the manufacturers' own published listings on the dates linked above and can change without notice. Scores are Tallow's own label-based ratings, not laboratory measurements. This is not medical advice.