Wholegrains and traditional bread making processes to enhance health benefits of baked goods

摘要

The processes of grain milling as well as bread making both have a very long history and the evolution of current practices has seen many changes in both processing and formulation of baked goods. White flour is preferred as the primary ingredient rather than wholemeal. In addition there has been a trend to abandon sourdough fermentation and adopt rapid bread making procedures. However growing evidence indicates that traditional approaches offer significant health advantages to consumers. Accordingly, the purpose of this project has been to investigate the significance of various aspects of bread making in relation to the health implications of bread. For this purpose loaves have been prepared by applying bulk and sourdough fermentation using freshly milled whole grains. Various components have been investigated and the effects of fermentation time and temperature evaluated for selected blends of wholemeal grains. In order to study the stability and retention of vitamin E components, the possibility and advantages of replacing hexane with the less toxic (and greener) option of heptane for HPLC analysis was evaluated. Strategies to increase the quantity of vitamin E were found and the optimal fermentation conditions established. The use of palm oil as an ingredient in bread making was demonstrated as a means to increase the vitamin E content of wholemeal breads and a further advantage was the wider range of E vitamers retained during baking. To evaluate factors influencing phytate levels and resistant starch (RS) formation, the effects of fermentation time and temperature on selected wholemeal flours from rye, oats and wheat were also investigated. Fermentation temperature was found to make only a small difference to the degree of phytate reduction and the formation of resistant starch (RS). The presence of palm oil in formulations decreased the RS content in rye bread when added at 8 %. The rye sourdough fermentation gave the greatest formation of RS and temperature also influenced the levels to some extent. Rye sourdough fermentation because of the lowering of pH appeared to have a greater effect on RS formation than that observed for bulk fermented wholemeal breads. A further series of trials were been carried out to evaluate the detoxification of gliadin by a partially purified preparation of the papaya enzyme caricain. The incorporation of the enzyme directly into wholemeal wheat dough demonstrated that caricain is able to detoxify wheat to a level at where it is less of a problem for coeliac sufferers and this approach warrants further investigation in baking as well as other processes using cereal grains, particularly wheat and rye. Accordingly, the results of the phases of this investigation show that some of the more traditional approaches in milling and baking do have potential as ways to enhance the nutritional profile of baked goods. Various ways to provide health benefits are therefore recommended and these impact upon the vitamin E and resistant starch contents of breads.