The influence of lipid changes in bran and offall on the baking properties of wheaten flour

Abstract

Bread is an important commodity in South Africa for its nutritional value and contribution to the economy. As such anything that enhances consumption of bread is of economic importance.

Variation in bread volumen influences its utility value aand consumer acceptance of the product- The variation of brown bread volume is much greater than that of white bread. Bakers will benefit if they could control the variation in brown bread volume since consumer studies indicate that brown bread sales could surpass that of white bread in the near future. The baking industry uses an automated, continuous baking process that is difficult to alter. Variance of flour thus causes variance in bread volume. Flour variance is caused by the availability of suitable wheat cultivars to blend the grist, the sxtraction rate of the flour, the amount of bran and germ materials inclusionan and the amount of cake flour divided off. Although millers strive to control variation in flour quality, they must operate their mills within constraints of profitability and wheat availability. Deregulation is only applied to bread and excludes the raw material. Since the total deregulation of bread, the fixed price structure has been abolished. Bakers can now use more expensive additives to negate any shortfalls in floUT quality. This could ensure standard bread quality at a slightly higher price. The problem at this stage is that very little is known about the factors that cause variable bread volume. In most cases decreased volumes are attributed to shortfalls in protein quality and quantity and bran content. Baking quality of brown bread flour deteriorates during storage. The deterioration is mor pronounced in flour blended with bran before storage. This study centres around the effects of changing lipid composition during storage on the baking quality of the flour. A review of the literature, with respect to the formation of gluten and the lipidprotein interactions during this process) shows that the various authors have contradictory opinions. The effects of bran and its contribution to the baking process led to even more contradictions. The research approach of this study differed from the approach published in the literature where the researchers use a specific sample of wheat and then generalise for wheat in total. fn this study the samples were selected such that variation between samples are as high as possible. The lipids were extracted as total lipid, and were not separated into various fractions. This allowed the determination of the effect of the changed total lipid content on bread volume. The separation of the different flour samples, that was necessary in the analysis of the results, indicates that one or more important parameters were absent in the design. With this approach it was shown that the changes in total lipids are caused by enzymatic action and that total lipid profIles correlate with bread volumes. It was however impossible to generalise for all the different samples of flour.