Vol. XXIV · Bread Plate 1 of 12flour, wheat flour, protein content, bread flour, all-purpose flour, cake flour, 高筋面粉, 中筋面粉, 低筋面粉, wholemeal, ash, T55, T65, gluten, water absorptionMT

Flour.

The bag says "bread flour" or "高筋面粉". What it is telling you is a number: about 12–14 % protein, enough to build the gluten that holds a loaf up.

Wheat flour is mostly starch with 7–15 % protein, and most of that protein is glutenin and gliadin, which with water and work become gluten (VI.10). The amount depends on the wheat: hard wheats, grown in dry climates, are high in protein; soft wheats are low. Mills blend them to grades. Cake and pastry flour (about 7–9 %) make tender, fine crumbs; all-purpose (plain) flour (about 10–12 %) is the compromise; bread flour (12–14 %) builds strong, elastic doughs that trap gas and give chewy, open bread. Chinese flour is labelled the same way: 低筋 for cakes and biscuits, 中筋 for dumplings, noodles and steamed buns (XXVI.1), 高筋 for bread and hand-pulled noodles (XXVI.4).

More protein also means more water absorbed: bread flour takes a few per cent more water than plain flour for the same dough feel (XXIV.3). Ash — the mineral residue after burning a sample — measures how much bran is in the flour: European grades are named by it (French type 55 is about 0.55 % ash, type 65 a little more bran, type 150 wholemeal), and higher ash gives a darker, more flavourful, slightly weaker dough. Wholemeal flour is high in protein but its bran cuts gluten strands (XXI.1). The workshop compares flours.

Below: protein in four flours (USDA FoodData Central) and the gluten each develops in a dough of 65 % water kneaded ten minutes (course gluten model, as in VI.10), the flour you choose highlighted, with its typical uses.

What you will learn
Workshop
Protein from USDA FoodData Central: cake flour, all-purpose (plain) flour, bread flour and whole-grain flour. Gluten: the course teaching model at 65 % water and ten minutes of kneading; bran in wholemeal is not modelled and weakens it in practice. Chinese grades: 低筋 below about 9.5 %, 中筋 about 9.5–11.5 %, 高筋 above about 11.5 % protein (typical market practice).

Choose the flour by its protein

In USDA's data cake flour has about 8.2 % protein and bread flour about 12.0 %; kneaded the same way with the same water, the course model develops gluten of 0.49 and 0.71. That difference is the whole reason for the grades: the strong network of bread flour stretches into the thin walls of an open crumb and springs in the oven (XXIV.9), the weak one of cake flour gives a short, tender bite (XXV.2).

Practical choices: bread, pizza, bagels and 拉面 — bread flour or 高筋; dumplings, 馒头, noodles and pastry — all-purpose or 中筋; sponges, chiffon and shortbread — cake flour or 低筋, or plain flour with a tenth replaced by cornflour; wholemeal bread — wholemeal mixed with bread flour, more water and a longer rest (XXIV.4). Store white flour sealed and dry for up to a year, wholemeal in the cold (XXIII.2). Check the protein on the label; brands of "plain flour" differ by two percentage points or more.

At the stove

Read the protein per 100 g on every flour in your kitchen and sort them from weakest to strongest. Make a small dough with each at the same water and feel the difference.

The French type numbers come from the ash test, introduced to classify flours in the nineteenth century; in China, flour grades were formalised in national standards for specialised flours (bread, noodle, dumpling, cake), each with its own protein range.

Terms

Protein content
The share of protein in flour, mostly gluten-forming.
高筋 / 中筋 / 低筋
Chinese high-, medium- and low-gluten flours.
Ash
Mineral residue that measures bran in flour.
Hard and soft wheat
High- and low-protein wheats.
Flour grades are protein grades: cake/低筋 for tender crumbs, all-purpose/中筋 for dumplings and noodles, bread/高筋 for strong, chewy doughs. More protein absorbs more water; ash measures bran.

Sources

  1. USDA FoodData Central, SR Legacy (April 2018), public domain.
  2. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
  3. H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.