Ab initio bread design

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Ab initio bread design: The role of bubbles in doughs and pores in breads This thesis is presented for the degree of Doctor of Philosophy of The University of Western Australia

School of Earth and Environment and The UWA Institute of Agriculture March 2015

Shuo Wang B.A. Computer Science University of Minnesota Minneapolis, MN

Abstract Bread is a staple food in the human diet. It is a ‘convenient’ product delivering both satiety and nutrition, and is therefore highly desired worldwide. Traditionally, bread is made using high protein wheat as consumers generally do not like the quality of bread made with lower protein wheat. Most high protein wheat is grown in North America and exported to other countries to make bread products. However, low protein wheat is more prevalent worldwide. Attempts to improve soil conditions, plant genetics and fertilizers to bolster protein levels in non-bread making (low protein) wheat have been made. While there have been some improvements in crop health and yield, and even protein content, the improved wheat has not been comparable in bread making functionalities to those grown in North America. Looking at bread as a material, it is easy to recognize that breads have a foamlike structure. While many attempts have been made to develop the wheat varieties needed to make bread, little knowledge has been generated regarding the creation of an optimal foam structure. It is from this angle -- engineering the foam structure in bread -that this work was carried out. This project examined the role of bubbles in bread quality, how dough is transformed into bread, the relevant properties for bubble growth in proofing dough, and whether or not pore structure in bread and bubble structure in dough could be generalized. The study was divided into four components: (1) establish the importance of pore structure on bread texture by examining a range of breads varying in texture and composition using x-ray microtomography and mechanical testing, (2) examine the importance of porosity on a given bread by developing digital versions of breads examined in (1), and changing porosity and pore structure without changing the properties of solid phases, (3) examine the growth of bubbles in dough made with Australian and Canadian flours using x-ray microtomography and rheological properties of dough, and (4) apply the percolation theory to determine the critical parameters required for defining bread structure. The results from each of the above components are: (1) demonstrated that porosity is mostly due to one large, tortuous, interconnected structure with the remainder (