Staling Effects When Adding Low Amounts of Normal and Heat-Treated Barley Flour to a Wheat Bread

The properties of a white wheat bread could be changed by adding normal or heat-treated barley flour in small amounts (2 and 4%) to a white wheat bread recipe. Differences regarding gelatinisation as well as retrogradation properties were found when analysing the two flours in model systems. The heat-treated flour was fully gelatinised due to a prior time-, temperature- and pressure-treatment and could therefore absorb larger amounts of water than the other flours. In gelatinised model systems with 40% flour (dry weight basis), the heat-treated barley flour was found to contain less retrograded amylopectin as compared to normal barley flour after storage for up to 14 days, whereas no differences were found at 20%. However, stored breads showed an increased retrogradation of amylopectin (as measured by differential scanning calorimetry, DSC) when 2% pre-treated barley flour was added as compared to an addition of 2% normal barley flour. On the other hand, there were no significant differences at the 4% level. Addition of either of the barley flours resulted in less firm breads during storage as compared to the control breads. An increased water absorption in barley flour and thereby an increased water content in the breads and/or different water binding capacities of the flour blends could explain these results. The present study indicated that water had a stronger influence on the bread firmness than the retrogradation of amylopectin. This conclusion was based on breads with pre-treated barley flour being less firm than breads with normal barley flour, although the retrogradation, as determined by DSC, was higher