Wheat. Peter R. Shewry

b). These contributions are higher in Poland, with bread providing 21.9% of energy, 16.5% of protein, 35.4% of fibre, 24.9% of iron, and 20.7% of folate (vitamin B9) (Laskowski et al. 2019). The wide consumption and low price of bread therefore make it an excellent vehicle for delivering improved nutrition to large populations at low cost.

      The nutritional and health impacts of wheat are discussed in detail in Chapter 9, with the following sections focusing on more practical aspects of the processing of wheat for food, particularly bread.

      1.4.1 The Development of Milling and Baking

The remains of grains of wild cereals and goat grasses from c. 50 000 to 60 000 BP have been found in cave dwellings at Kebrara in modern‐day Israel (Lev et al. 2005), while remains of c. 23 000 years old wild emmer have been identified from the Ohalo II hunter‐gatherer camp on the shores of the Sea of Galilee (Weiss et al. 2004). The seed collections from both sites are diverse. Kebrara is dominated by the remains of legume seeds; at Ohalo II, the emmer is a rarity amongst greater amounts of wild barley ( Hordeum spontaneum ) and an extensive range of smaller seeded grasses. Nonetheless, there is good evidence that grains of wild wheats were eaten at least 13 000 years before domestication, and a much earlier date is probable.

      Raw wheat seeds are tough, unpalatable, and relatively indigestible unless milled or crushed. At Ohalo II, there is evidence that seeds were crushed between grindstones, long before the advent of agriculture. Crushing would have exposed the starchy endosperm and dramatically increased the bioavailability of nutrients, particularly that of carbohydrate. It would also have speeded the rate with which blood sugar was increased, i.e. the glycaemic index (Rubel 2011).

The ancient process of milling involved manually grinding the grain between stones; a lower, usually concave, static quern stone (called a saddle quern) and an upper hemispherical or cylindrical (like a rolling pin) handstone pushed over the grain. A fine example from Norway is shown in Figure 1.16a.

      Of particular importance for the adoption of wheat as a food crop were the properties of the dough formed by mixing the flour released from crushed or milled grain with water. Wheat doughs have unique visco‐elastic properties that confer significant functional and organoleptic qualities on wheat products, particularly bread and other baked goods. Baking dates back at least 14 000 years (Henry et al. 2011, 2014; Arranz‐Otaegui et al. 2018), and possibly much earlier (Rubel 2011). In particular, doughs made from wheat, far more than from other cereals, are able to trap carbon dioxide released during fermentation by yeast, and hence can produce baked foods with low density. This is the basis of the diverse forms of leavened bread. Yeast spores may occur naturally on the surface of cereal grains and some fermentation occurs readily in wheat dough left to rest. However, it is probable that early bakers used sourdough systems (mixtures of lactobacilli and yeasts), with starters being carried over from batch to batch as in artisan bakeries today. Bread production was clearly important in the Uruk culture (6000–5100 BP) of lower Mesopotamia, and cuneiform writings from around 4000 BP include Sumerian poems and myths about the invention of bread, along with recipes. The Egyptians appear to have perfected leavened bread production by 4000 BP.

Figure 1.16 Stone querns on display at the Archaeological Museum, University of Stavanger, Norway. a, neolithic (possibly bronze age) saddle quern; b, pair of rotary quern stones (46–47 cm diameter) from about 550 CE.

      Source: Photographs kindly provided by Per Storemyr (Per Storemyr Archaeology and Conservation).

From around 2500 BP the laborious use of saddle querns had been replaced by rotary querns. These comprised two circular stones with the upper being rotated by hand and the grain fed through a hole in the upper stone and the flour emerging from the edge (Figure 1.16b). Further refinement of this basic system led to mechanized stone milling. In Roman times, grain was ground as it passed down between a lower meta stone and the upper, rotated, catillus (Figure 1.17). The Romans prized wheat as the empire's principal staple food. In Rome, at any one time, up to 320 000 of the poorer population were supported by free wheat grain and bread (Rickman 1980).

By the 1800s CE stone milling had evolved into a highly sophisticated process, with the mill stones being carved (dressed) to improve efficiency. Dressing divides the surface of the stone into flat areas, called lands, which are separated by furrows. Further small feathering grooves are then carved from the furrows onto the lands. These provide cutting edges, acting like scissors, and channel the meal from the centre to the outside of the stones. A gap is also maintained between the stones to prevent wear and overheating. Dressing mill stones is a highly skilled art and needs to be carried out regularly (see Cookson 2019). Stone milling produces wholemeal flour which can be dressed (sieved through cloth filters) to separate white flour. However, the separation of the flour and bran is poor, and the flour produced is expensive. Hence, before the introduction of roller mills, white flour was a luxury, associated with purity and the social elite due to its appearance and cost. This situation was transformed with the advent of roller milling (Figure 1.18).

The first successful roller mill was developed in Switzerland about 1830 CE and the first complete roller mill (Radford's Albert Mill, Liverpool) established in the UK in 1870 CE (Cookson 2019). Roller milling was widely adopted by the end of the nineteenth century. Roller mills use a series of rollers; these initially break the grain open and then scrape the starchy endosperm away from the bran (comprising the pericarp, testa, aleurone layer, and usually also the germ) to give break fractions. Further rollers reduce the size of the flour particles in these fractions to give reduction fractions. When combined with sieving, these two types of roller generate over 20 white flour fractions in modern mills; when recombined the flour may account for up to 80% of the grain dry weight, essentially the whole of the starchy endosperm. The white flour produced by roller milling is very fine and pure, and the process is highly efficient and economical to operate. It therefore led to the current global dominance of white bread.

Figure 1.17 The milling room and detail of a mill in a bakery complex at the port of Rome, Ostia; constructed c. 200 CE (

      Source: described by Bakker 1999).

Figure 1.18 A modern roller mill and miller.

      Source: Photograph kindly provided by Dr. Mervin Poole, Heygates Ltd., UK.

      1.4.2 The Cultural Significance of Bread

In view of the life or death importance of wheat, it is not surprising that it has become firmly entrenched in both culture and religion. One of the most culturally embedded types of bread is non (Figure 1.19g), a leavened bread which is consumed throughout Central Asia. It is cooked on the wall of a clay oven (tandoor) and stamped with a wooden tool studded with pins (a chekich) to raise