Separation of bread wheat flours into starch and gluten fractions: effect of water temperature alone or in combination with water to flour ratio

Abstract

AbstractTwo different commercial bread wheat flours (BF‐I, 65% extraction and BF‐V, 86% extraction) were separated into gluten and starch milk by making a dough, allowing some time for maturation, dispersing the dough in water and wet sieving/washing. The effect of using of warm water (20–45 °C) for dough making and washing on separation was studied for BF‐I flour at 640 g kg−1 water to flour ratio of and 300 s maturation time, and the separation was found to improve with increase in temperature. The combined effects of water temperature (20–50 °C) and water to flour ratio (640–780 g kg−1 for BF‐I and 620–870 g kg−1 for BF‐V) were studied at 600 s maturation time. The quantities and dry matter contents of the gluten fraction and starch milk were measured; a sample of starch milk was centrifuged to obtain decantate, tailing and prime starch fractions, and the dry matter contents of each were determined. All the dried samples were also analysed for protein content, and the fractional recoveries of dry matter and protein in the gluten fraction, prime starch, tailings and decantate were calculated. The results indicated the optimum point for BF‐I flour to be the combination of optimum farinograph water absorption and 40 °C. BF‐V showed very poor separation behaviour within the ranges studied. At the optimum farinograph water absorption the use of warm water for dough making and 20 °C water for washing steps was also tried, but no significant improvement over the 20 °C results was obtained.© 2002 Society of Chemical Industry