CEREAL TECHNOLOGY: CEREAL GRAINS
Diagram
Two grains for bread, two kinds of dough
Wheat
The main bread grain. Its proteins form gluten, a strong elastic network that traps gas and gives a light loaf.
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Rye
A hardy grain for cold climates. Its proteins do not form the same gluten, so rye bread is dense, moist and dark.
Figure 1: Wheat forms a strong gluten network, while rye does not, so wheat bread is light and rye bread is dense. Drawn in our own style from the comparison of wheat with other cereals in Cornell and Hoveling, Wheat: Chemistry and Utilization, Chapter 1, Comparison of Wheat with Other Cereals.
Introduction
Wheat and rye are both cereal grains used for bread, but they give very different loaves. Wheat is the main bread grain because its proteins, gliadin and glutenin, form gluten when water is added and the dough is mixed: a strong, elastic network that traps the carbon dioxide from yeast and lets the loaf rise high and light. Rye is a hardy grain that grows where wheat struggles, in cold and poor soils, but its proteins do not form the same gluten network. Rye dough is held together by sticky pentosans, not by gluten, so rye bread is dense, moist and dark, with a strong flavour of its own.
Quick comparison
Table 1: Wheat compared with Rye
| Aspect | Wheat | Rye |
|---|---|---|
| Main use | Bread, the main bread grain | Bread, especially in cold climates where wheat struggles |
| Gluten | Forms a strong, elastic gluten network | Does not form the same gluten network |
| Dough | Elastic and stretchy, holds gas well | Sticky and slack, held by pentosans, holds gas poorly |
| Bread | Light, high, with an open crumb | Dense, moist, dark, with a close crumb |
| Flavour | Mild and wheaty | Strong, sour and earthy |
| Protein | Gliadin and glutenin, which form gluten | Proteins that do not form gluten in the same way |
| Starch | Starch that gelatinises in baking | Starch with more pentosans, which hold water |
| Growing | Needs a mild climate and good soil | Hardy, grows in cold and poor soils |
| Flour colour | White to brown, by the milling | Grey to dark brown |
| Bread keeping | Stales by crumb firming | Keeps moist longer, because pentosans hold water |
Scientific explanation
Definition
Wheat is a cereal grain whose proteins form gluten, a strong elastic network that traps gas and gives bread its volume. Rye is a cereal grain whose proteins do not form the same gluten network, so its bread is dense and moist and is held together by sticky pentosans.
Working principle
When wheat flour meets water and is mixed, gliadin and glutenin join into gluten, a network that stretches as gas bubbles grow and holds them in the dough. The loaf rises high and the crumb is open and light. When rye flour meets water, its proteins do not form that network, so the dough cannot trap gas in the same way. Instead, the pentosans of rye, gummy carbohydrates in the grain, absorb water and make the dough sticky and thick, which holds the loaf together but keeps it dense. Rye bread is often made with sourdough, whose acid helps the pentosans set and gives the bread its sour flavour.
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 wheat, the protein amount and quality decide the loaf volume: strong gluten gives a high loaf. For rye, the pentosans and the acidity decide the loaf: a sourdough acid helps the dough set and keeps the crumb moist. In both cases the milling decides the flour: wholemeal rye is darker and denser than white rye flour. The books used here give no protein values with numbers, so none are stated.
Formulas and calculations
The books used here give no formula for either term, so no formula is given here.
Industrial applications
- Wheat: white and whole wheat bread, rolls, cakes and pastries, where a light loaf is wanted.
- Wheat: pasta and noodles, where strong gluten holds the shape.
- Rye: rye bread and pumpernickel, where a dense, moist, dark loaf is wanted.
- Rye: crispbread and sourdough rye, where its strong flavour is the point.
- Both: mixed wheat and rye breads, where rye adds flavour and wheat adds volume.
Advantages and limitations
- Wheat, advantage: its gluten gives bread a large volume and a light, open crumb.
- Wheat, limitation: it needs a mild climate and good soil, and it does not grow where rye thrives.
- Rye, advantage: it is hardy and grows in cold and poor soils, and its bread keeps moist and has a strong flavour.
- Rye, limitation: its proteins do not form gluten, so its bread is dense and cannot rise like wheat bread.
FAQ
What is the difference between wheat and rye?
Wheat proteins form a strong gluten network that gives a light loaf, while rye proteins do not, so rye bread is dense and moist.
Why is rye bread dense?
Rye dough is held by sticky pentosans, not by gluten, so it cannot trap gas as well as wheat dough.
Why is rye bread often sour?
Rye bread is often made with sourdough, whose acid helps the dough set and gives the sour flavour.
Can rye grow where wheat cannot?
Yes. Rye is hardy and grows in cold and poor soils where wheat struggles.
Can you make bread from rye alone?
Yes, but it stays dense. Bakers often mix rye with wheat flour to add volume.
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)
