The Performance of U.S. Hard White Wheats: Effect of Milling Extraction on Flour, Pan Bread, Tortilla and Pita (Arabic) Bread Quality

Three U.S. hard white wheat varieties grown in California, Colorado and Kansas were milled to flour of straight-grade and 80% extractions. The proximate wheat analysis for test weight ranged from 55.8 to 63.0; protein from 10.1 to 13.7; and ash from 1.52 to 1.81 g/100 g. The flour samples were analysed and made into pan bread, pita (Arabic bread) and tortillas. Increasing the extraction rate from straight-grade to 80% resulted in an average increase of 0.4 g/100 g in protein content, 0.2 g/100 g in ash, 1.1 g/100 g in farinograph water absorption, and an average decrease of 1.3 in L-value of color (means darker flour), and a reduction in relatively viscosity of 37.4 units. Flours of high protein content produced higher pan bread volume, and superior quality tortillas. However, pita bread quality deteriorated with higher flour protein. Various flour quality factors affected the quality of the final product. The prediction equations for pan bread volume prepared from straight-grade flour showed the importance of flour protein content and farinograph water absorption. In those prepared with flour of 80% extraction, these quality components, farinograph maximum tolerance index (MTI) and starch peak viscosity constituted the best prediction equation. The appearance of starch peak viscosity and MTI in the prediction equation is presumably due to the reduced influence of quality of protein in flours of high extraction rate. The prediction equations for pita bread and tortillas were governed by various flour components. Hence, it is erroneous to assume that a flour for optimum quality pan bread produces similar quality pita or tortillas.