Grain-based Flours
What are Grain-based Flours?
Grain-based flours are powders produced by reducing grains to small particle sizes. They are used primarily for making breads, cookies, cakes, pastries and other baked goods.
Grain flours are commercially-available in two main forms:
- Whole flours which contain the grain’s endosperm, germ and bran fractions
- Refined flours which contain only the endosperm fraction
Commonly used grain flours can be classified into gluten- and non-gluten containing types:
| Grains containing gluten | Grains not containing gluten |
Origin
Producing flours from grains is an ancient practice which is believed to have originated around 6000 BC. Scenes of milling and baking can still be seen on the walls of Egyptian tombs dating back to 2600 BC.
Earlier flour grinding systems were cone mills which developed into stone mills. Roller mills were invented in 1865 in Hungary while the first steam mill was built in England in 1879. Jet milling is one of the newest technological advances for making superfine flours.1
Typical composition of common grain-based flours:*
| Flour | Protein (%) | Fat (%) | Carbohydrates/total sugars (%) | Fiber (%) | Energy (Kcal) |
| Gluten-containing grains | |||||
| Wheat | 11.8 | 1.1 | 70.7 / 1.4 | 12.6 | 345 |
| Spelt | 16.67 | 1.67 | 73.33 | 13.3 | 367 |
| Khorasan | 14.7 | 2 | 60.6 | 10 | 1.6 |
| Emmer | 8-15 | 2.8 | 68 | 13 | 2.3 |
| Einkorn | 18.2 | 2.48 | 74.2 | 8.7 | 1450 |
| Barley | 10 | -1 | 76.67 | 16.7 | 367 |
| Triticale | 12.5 | 1.56 | 71.88 | 15.6 | 344 |
| Rye (medium color) | 10.88 | 1.52 | 75.43 | 11.8 | 349 |
| Non-gluten-containing grains | |||||
| Oat | 14.66 | 9.12 | 65.7 | 6.5 | 404 |
| Corn | 10.35 | 5.17 | 75.86 | 6.9 | 379 |
| Millet | 10 | 3.33 | 73.33 | 13.3 | 367 |
| Sorghum | 11.76 | 2.84 | 73.53 | 8.8 | 353 |
| Quinoa | 11.75 | 1 | 31 | 13 | 364 |
*USDA Branded Food Products Database, July 2018 & other sources3
Flour composition varies significantly with the grain’s cultivar, milling process, flour extraction rate among others.
Commercial Production
Grain milling uses two approaches:
- Break open kernel to separate the endosperm from bran (principle of roller milling). It involves multiple grinding and separation steps from sifting to aspiration and gravity separation.
- Decortication/degermination and transforming the endosperm to grits or flour. Typically used with maize and sorghum.
Modern milling operations consist of:
- Cleaning the kernels to remove extraneous material.
- Tempering and moisture adjusting to toughen the bran and make the germ more pliable so the endosperm is easily separated.
- Breaking/crushing the kernels between corrugated rollers, loosening the endosperm from the bran and germ.
- Separating or purifying the endosperm from the bran and the germ, using sieves and air currents to produce middlings.
- Grinding the middlings into flour between a series of smooth, reduction rollers.
Steps 3, 4 and 5 can be repeated several times to generate flour streams where each progressive stream contains less endosperm and more bran and germ impurities than the last. These streams are selectively combined and sifted to produce commercial grades of flour. The flour is then naturally aged or treated with bleaching and maturing agents. Production of whole wheat flours requires unique systems to prevent lipid deterioration due to rancidity.
Types
Ancient grains such as spelt, Khorasan and emmer have vitreous and hard kernels with high ash content. They produce flours with low yield. Barley milling challenges are similar to those of ancient grains.
Triticale grains are milled using standard wheat flour milling techniques. However, its low milling efficiency caused by the grain morphology (shriveled, long, deep creases and soft endosperm) can be improved by co-milling triticale with wheat3
Millet and sorghum are decorticated prior to grinding. Roller milling produces whole wheat flour, semi-refined and a bran-rich fraction. Finely-ground particles are sifted...
