From Wheat to Flour: A History of the Miller's Craft

What's Actually Inside a Wheat Kernel

Cut a wheat kernel in half and three distinct layers appear: the outer bran, the embryo or germ at its core, and the starchy endosperm that fills the space between them.

Endosperm makes up roughly four-fifths of the kernel's weight, with bran and germ sharing the remaining fifth. Milling is, at its core, the act of separating these three layers — and how much of each ends up in the final flour determines its color, nutrition, and shelf life.

Stone Mills vs. Roller Mills

A stone mill crushes the kernel in a single pass between a fixed bed stone and a rotating stone above it, mixing bran, germ, and endosperm together as it grinds.

Roller mills work differently: the kernel passes through a sequence of steel rollers, with sifting stages between each pass that separate endosperm fragments from bran and germ. This staged process allows the three layers to be pulled apart far more thoroughly than a single stone pass ever could.

Roller mills began replacing stone mills industrially in the 19th century, a shift that made fine, bran-free white flour possible at a scale stone mills never reached.

Why Milling Removes the Germ

Wheat germ is over 10 percent fat by weight, most of it polyunsaturated. Those fats oxidize quickly once exposed to air, and flour milled with the germ intact can turn rancid within six to nine months depending on climate and grain quality.

Removing the germ is one of the main reasons white flour keeps so much longer. The trade-off is nutritional: germ is a concentrated source of protein, vitamin E, folate, zinc, and magnesium, while bran contributes fiber and B vitamins that also disappear once both are sifted out.

What Flour Type Numbers Actually Measure

Extraction rate describes how much flour, by weight, comes out of the wheat that goes in. Refined white flour typically runs at roughly 50 to 60 percent extraction, since only the endosperm is kept; whole wheat flour runs close to 100 percent, because nothing is removed.

Flour type is usually classified by ash content — the mineral residue left after flour is incinerated. White flour tends to sit around 0.4 grams of ash per 100 grams; whole wheat flour can reach 2 grams or more, because bran and germ carry far more minerals than endosperm does.

The numbering conventions built on this logic differ by country, so a type number on one country's flour bag doesn't map directly onto another's system — the underlying ash-content logic is universal, the scale is not.

Anatolia's Watermill Record

The geographer Strabo recorded a water-powered grain mill operating near the palace of King Mithridates VI of Pontus at Cabira before 71 BC — a site in what is now Niksar, in Turkey's Tokat province, making it one of the earliest documented watermills anywhere and placing it squarely in Anatolia.

About four centuries later, Gregory of Nyssa, a Christian writer from Anatolia, also described the use of water power. Together, these two records anchor the region's watermill tradition in antiquity — mills built where rivers ran strong and steady enough to keep a wheel turning.

The Return of Stone-Ground Flour

A growing number of artisan bakers and small mills have gone back to stone grinding, prizing how it leaves the germ largely intact and produces a coarser, more flavorful whole wheat flour than the roller process typically does.

The label isn't always a reliable guide, though. In the United States, flour only needs to pass between stones once to be legally called stoneground, which means ordinary roller-milled whole wheat flour sometimes carries the label anyway. It's worth checking how a mill actually describes its process before taking the term at face value.