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In addition to protein concentration, the relative proportions and subunit compositions of the gliadin and glutenin fractions also have significant effects on dough rheology and functionality for different end uses. In broad terms, gliadins contribute to the viscosity and extensibility and glutenins to the elasticity and strength of doughs (Rustgi et al. 2019). The proportions of gliadins and glutenins may vary between genotypes (Wieser 2000) and there are also significant differences in quality associated with allelic variation in the protein compositions of the two fractions. In particular, one group of gluten proteins, the high molecular weight subunits of glutenin, are widely used as biochemical markers for dough strength (see Chapter 8 and Payne et al. 1987) based on analysis by sodium dodecylsulphate polyacrylamide gel electrophoresis or by capillary or reversed‐phase high‐performance liquid‐chromatography (RP‐HPLC) (Rustgi et al. 2019).

The strong genetic control of protein quality means that cultivars are often grouped based on their intended end use. For example, in the UK cultivars are grouped depending on whether they have potential for breadmaking (Groups 1 and 2), biscuit making (Group 3), or neither end use (Group 4).

The proportions and compositions of the gliadin and glutenin fractions are also affected by environmental factors, which can lead to effects on processing quality. For example, the availability of S is particularly important as it affects the ratio of N : S in the grain and, therefore the proportions of proteins which are rich in cysteine (a suphur‐containing amino acid required for the formation of disulphide bonds in glutenin polymers) (Wieser et al. 2004). Indeed, several studies showed that the grain S concentration was a better predictor of breadmaking quality than N concentration (Zhao et al. 1999a, b; Ruske et al. 2004).