CEREAL TECHNOLOGY: WHEAT FLOURS
Diagram
Coarse durum flour for pasta, fine soft flour for general baking
Semolina
Coarse flour milled from durum wheat. Hard, yellow, high in protein, and it holds its shape in boiling water.
↓
All-purpose flour
Fine flour milled from a blend of hard and soft wheat. White, soft, medium in protein, for general baking.
Figure 1: Semolina is coarse durum flour for pasta, while all-purpose flour is fine blended flour for general baking. Drawn in our own style from the milling discussion in Cornell and Hoveling, Wheat: Chemistry and Utilization, Chapter 2, The Milling of Wheat.
Introduction
Semolina and all-purpose flour are both wheat flours, but they come from different wheats and are milled to different fineness. Semolina is the coarse flour milled from durum wheat, the hardest wheat, and it is yellow, gritty and high in protein, which is why it is used for pasta: it holds its shape in boiling water and gives pasta its firm bite. All-purpose flour is a fine white flour milled from a blend of hard and soft wheat, medium in protein, made for general baking: it suits cakes, biscuits, bread and pastry well enough, but it is not the best flour for any one of them.
Quick comparison
Table 1: Semolina compared with All-Purpose Flour
| Aspect | Semolina | All-Purpose Flour |
|---|---|---|
| Wheat | Durum wheat, the hardest wheat | A blend of hard and soft wheat |
| Fineness | Coarse and gritty | Fine and smooth |
| Colour | Yellow, from the carotenoid pigments of durum | White |
| Protein | High, and the gluten is strong | Medium, between bread flour and cake flour |
| Gluten | Strong, so pasta holds its shape | Medium strength, for general baking |
| Water absorption | High, but it hydrates slowly because it is coarse | Medium |
| Used for | Pasta, couscous and some breads | Cakes, biscuits, bread, pastry and general baking |
| In boiling water | Holds its shape and stays firm | Would fall apart, because it is a fine soft flour |
| Flavour | Nutty and wheaty | Mild and neutral |
| Milling | Durum is milled coarsely on purpose | Milled fine and blended to a standard protein |
Scientific explanation
Definition
Semolina is the coarse flour milled from durum wheat, high in protein and yellow in colour, used mainly for pasta. All-purpose flour is a fine white flour milled from a blend of hard and soft wheat, medium in protein, made for general baking.
Working principle
Durum wheat is so hard that milling it gives coarse, gritty pieces rather than fine flour, and those pieces are semolina. The high protein of durum forms a strong gluten network, and the coarse pieces hydrate slowly, so pasta made from semolina holds its shape in boiling water and stays firm to the bite instead of going soft. All-purpose flour is milled fine from a blend of hard and soft wheat, so its protein sits between bread flour and cake flour: strong enough for a loaf, tender enough for a cake, but not the best for either. Its fineness lets it hydrate fast and give a smooth batter.
Apparatus
The books used here name no laboratory apparatus for measuring or comparing either term, so no apparatus list is given.
Measurement procedure
The books used here give no standard laboratory procedure with volumes and steps for either term, so no procedure is invented here.
Factors affecting readings
For semolina, the durum variety and the coarseness of the milling decide the pasta quality: coarse semolina hydrates slowly and needs kneading and resting. For all-purpose flour, the blend of hard and soft wheat decides the protein and so the balance between strength and tenderness. In both cases the water decides the dough: semolina needs time to absorb water, while fine flour absorbs it at once.
Formulas and calculations
The books used here give no formula for either term, so no formula is given here.
Industrial applications
- Semolina: pasta, where its strong gluten and coarse grain hold the shape in boiling water.
- Semolina: couscous, where the coarse flour is rolled into small grains.
- Semolina: some breads and puddings, where its yellow colour and nutty flavour are wanted.
- All-purpose flour: cakes, biscuits and pastry, where a fine, medium protein flour is wanted.
- All-purpose flour: bread and general baking, where one flour must do many jobs.
Advantages and limitations
- Semolina, advantage: its strong gluten and coarse grain give pasta a firm bite that survives boiling.
- Semolina, limitation: it is too coarse and too strong for cakes, and it hydrates slowly.
- All-purpose flour, advantage: one flour suits cakes, biscuits, bread and pastry, so it is the general baking flour.
- All-purpose flour, limitation: it is not the best flour for any one job: it makes neither the best bread nor the best cake.
FAQ
What is the difference between semolina and all-purpose flour?
Semolina is coarse flour from durum wheat, high in protein and used for pasta, while all-purpose flour is fine flour from a blend of hard and soft wheat, for general baking.
Why is semolina yellow?
Durum wheat holds carotenoid pigments, which give semolina its yellow colour.
Can I use all-purpose flour for pasta?
The pasta will be softer and may fall apart in boiling water, because all-purpose flour lacks the strong gluten and coarse grain of semolina.
Can I use semolina for cake?
No. It is too coarse and too strong, and the cake will be gritty and tough.
What is all-purpose flour made from?
A blend of hard and soft wheat, milled fine and blended to a medium protein.
References and further reading
- FTN books on disk: Cereal Technology.
- Cornell, Hugh and Albert W. Hoveling. Wheat: Chemistry and Utilization. CRC Press, 1998 (Google Books page read)
- Google Books pages read for this article:
- Cornell, Hugh and Albert W. Hoveling. Wheat: Chemistry and Utilization. CRC Press, 1998 (Google Books page read)
