Firming of bread crumb with cross-linked waxy barley starch substituted for wheat starch (1992)

Cereal Chem. 69(3):321-325 White pan bread was baked from flour that had been fractionated a higher enthalpy of melting than that of control bread crumb, except and reconstituted using cross-linked waxy barley starch (5.9% amylose at 6 hr after baking. Furthermore, a 50% gel of cross-linked waxy barley content) in place of prime wheat starch (28.3% amylose content). starch in water recrystallized faster at 250C than a 50% gel of wheat Compression measurements of crumb firmness showed that experimental starch as measured by enthalpy of melting. These data suggest that amylose bread firmed faster during storage at 250 C than control bread, even though dilutes the effect of the amylopectin, the recrystallization of which is the experimental bread had the lower crumb firmness 6 hr after baking. at least partially responsible for the firming of bread crumb. At the same time, the aged bread crumb of the experimental bread showed Bread staling involves organoleptic and physicochemical changes, such as firming of crumb, declining flavor, increasing opacity of crumb, toughening of crust, and decreasing starch solubility (Willhoft 1973, Maga 1975, Knightly 1977, Kulp and Ponte 1981). Perhaps the most important change is firming of bread crumb. Schoch and French (1947) suggested that amylopectin recrystallization is the main cause of firming of bread crumb on the basis of their study of the water-soluble starch extracted from bread crumb. Prentice et al (1954) supported the Schoch and French hypothesis using flour fractionation and starch replacement experiments with waxy corn and waxy sorghum. Several other investigators (Axford and Colwell 1967, Colwell et al 1969) also confirmed the hypothesis using differential thermal analysis. However, in more recent years, several researchers (Kim and D'Appolonia 1977, Ghiasi et al 1984, Rogers et al 1988) have suggested that mechanisms other than amylopectin recrystallization are involved in crumb firming of stored bread. Barley starch was found to be interchangeable with wheat starch in bread baking (Hoseney et al 1971), but when wheat starch was replaced with waxy barley starch in reconstituted flour, the bread made from the reconstituted flour shrank excessively during cooling (Hoseney et al 1983). However, Wu (1988) succeeded in baking bread containing a high level (95%) of amylopectin by introducing cross-links into waxy barley starch. Such highamylopectin bread may yield valuable information on the mechanism of crumb firming. If the Schoch and French hypothesis is operative, the rate and extent of crumb firming might be expected to be greater in the high-amylopectin bread than in regular bread, because amylose may dilute the effect of amylopectin (Tester and Morrison 1990). The objectives of this study were to replace wheat starch with cross-linked waxy barley starch in reconstituted flour and determine the level of cross-linking that gives high-amylopectin bread volume comparable to that of control bread, to examine the effect of the cross-linked waxy barley starch on crumb firming, and to compare the rate of crumb firming of the high-amylopectin bread with the rate of amylopectin recrystallization in the crumb.