Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/5/2006
Publication Date: 9/17/2006
Citation: Schober, T.J., Bean, S. 2006. How large is the role of proteins and their interactions with starch in gluten-free bread? [abstract]. AACC International Meeting. Symposia Paper No. 115. Interpretive Summary:
Technical Abstract: Gluten-free breads for celiac patients may be based on isolated starches and cereals including rice, maize or sorghum. This study focuses on the development of an improved gluten-free sorghum-starch bread (70% sorghum flour, 30% different starches) and the understanding of the physicochemical background. Starch-protein interactions in such breads may be relevant in two ways. Within the sorghum endosperm, the embedding of starch into a stable protein matrix might be responsible for the unavailability of some of the starch and a gritty mouth feel. In the batter, starch surface proteins might enable interactions between the granules. Additionally, solubilized proteins might stabilize bubbles. Starch breads without sorghum could be successfully baked without the addition of hydrocolloids or emulsifier. It was essential to carefully adjust water levels, so that it was just sufficient to create a homogenous batter, without water surplus within which the starch would settle. Individually, wheat starch performed best, maize starch intermediately and potato starch worst, although breads were still leavened. A 70/30 maize/potato starch mixture totally failed. However, adding an excess (100% on a starch basis, sb) of water in conjunction with 2.2 %sb hydroxypropyl methylcellulose (HPMC), produced a much superior, better aerated, bread. In such highly diluted systems, it is unlikely that many starch granules could interact via surface proteins. When using the 70% sorghum system, only the strategy of excess ('100%) water worked. Addition of HPMC, sourdough fermentation of the complete sorghum portion and the addition of a thermostable amylase greatly improved quality. HPMC could not be replaced by sorghum protein solubilized in alkali. It is concluded that in 70% sorghum/30% starch bread, starch-protein interactions play no relevant role in the batter but that it is advantageous to open up the endosperm by sourdough fermentation to release starch.