The characteristics and processing requirements of wheat for breadmaking

Abstract

The project, jointly funded by the Home-Grown Cereals Authority, MAFF and the EC, established the different pre-baking processes that flour from individual wheat varieties needs to make good bread.

The project highlighted differences in bakery performance between white and wholemeal flour. White flour from different varieties needs varying amounts of working or processing to make a good white loaf. Therefore, millers should grist according to the mixing requirements of individual varieties to produce flour with uniform dough mixing for the baker. However, when making wholemeal bread the energy needed to mix the dough is less critical.

Flour from some varieties such as Fresco, need so much mixing at the dough stage they are not commercially acceptable for white breadmaking unless blended with a variety with low mixing characteristics such as Riband.

Although intrinsically of poor breadmaking quality when used on its own, Riband is flexible in the amount of processing it needs to form a good loaf. It is therefore very suitable for blending with other quality wheats.

The study also showed that wholemeal flours need to be fortified with gluten to produce a loaf volume equivalent to that made from white flour from the same sample of grain.

These and other results enabled the researchers to establish several new wheat quality assessment tests which have now been included in the Recommended List assessment protocol.

The increasing proportion of the UK breadmaking wheat grist that is of UK origin (up to 88%), and the dominance of single wheat varieties has made the baking performance of these varieties very important.

Work carried out under this project has shown that the work-input requirement in the Chorleywood Bread Process (CBP) can vary from 5Wh/kg for Riband up to 20 Wh/kg for "extra-strong" types such as Fresco. Clear differences were observed between varieties in their tolerance to high work-input levels and rates of work input. Fresco performed best at high work-input/mixer speed combinations, and performed poorly in mixing regimes equivalent to current commercial practice.

Hereward and Mercia performed well at low work-input levels. In particular Hereward performed well in all mixing conditions. Riband was surprisingly tolerant of high work-input levels, although lower loaf volumes and crumb scores reflected its lower quality.

In a traditional breadmaking process, the fermentation tolerance of Canadian Western Red Spring (CWRS), Hereward, Mercia and Haven showed that for all varieties, increased fermentation time was not beneficial probably due to a lack of fermentable sugars for the yeast.

The varieties Fresco and Hereward are capable of carrying weaker varieties such as Galahad, Riband and Haven, the work-input requirement and baking performance of the blends approximating to the arithmetic means of the base flours.

In wholemeal, the high work-input requirement of "extra-strong" varieties such as Fresco was lost, and gluten fortification had no effect on the work-input requirement of wholemeal flours. The importance of protein content in wholemeal was demonstrated.

Wholemeal flours were shown to be more tolerant to increased cereal alpha-amylase levels (up to 100 FU). The deleterious effects observed in white bread on crumb stickiness, resilience and density were not apparent. Dextrin formation was much lower than in white bread possibly due to binding of calcium by phytic acid present in bran restricting enzyme activity.

A survey of several UK and continental European wheats showed that wholemeal loaf volumes could not be predicted from those of white. Soft milling varieties of breadmaking quality, and "extra-strong" varieties appeared to have advantages in wholemeal.

Rheological and biochemical tests highlighted a number of quality assessment methods that have potential in prediction of baking quality. In particular, the stress relaxation properties of yeasted doughs gave correlations with loaf volume in a relation that included white, wholemeal, and gluten fortification of wholemeal.

The glutenin fraction of wheat protein measured as gel-protein indicated that the elastic modulus (G') or the breakdown rate during mixing are quality attributes that may be used to predict the performance of varieties in the CBP. Such tests, had they been in use, would have demonstrated the "extra-strong" character of Fresco and the weak quality of Pastiche at an early stage in the trialling system. These tests are now included in the assessment of potential breadmaking varieties in Recommended List Trials.