Crumb bread, formation

Rye Proteins. While rye is the only European cereal able to completely replace wheat in bread, rye protein is not as effective as wheat protein. One reason for this is that as much as 80% of the protein in a rye sour dough is soluble compared with 10% of soluble protein in a wheat dough. One factor that inhibits the formation of a gluten-like complex is the 4-7% of pentosans present, which bind water and raise the viscosity of the dough. The crumb structure is then formed from the pentosans in combination with the starch. 

Furthermore, the data presented indicate that a thermally induced rupture of the yeast cells during crust formation is an important step to liberate precursors of the Acp or to liberate the Acp already formed in the interior of the yeast. This would also provide an explanation for the fact that much higher amounts of Acp are present in wheat bread crust compared to the crumb (see chapter by Schieberle and Grosch, this book). 

Another laboratory invoked the role of water in bread staling involving a zipper mechanism that results in the formation of interchain crosslinks 492 Moisture redistribution from crumb to crust played a significant role in crumb firming and amylopectin recrystallization for breads stored for more than seven days 493 According to Piazza and Masi494 to inhibit staling it is more important to slow the dehydration phenomena than it is to increase the initial moisture content in the bread. 

The n-alkyl portion of emulsifiers such as glycerol monostearate form a complex with helical regions of starch, a phenomenon that is thought to be responsible for the ability of GMS to retard starch crystallization in bread crumb, slowing the process of staling. Several workers have measured the stoichiometry of complex formation by using various methods. Some of these studies are mentioned later in connection with the discussion on bread staling here three typical reports are summarized. 

As discussed above, linear alkyl chains such as the fatty acid moiety of monoglycerides can form a complex with helical segments of the solubilized starch molecules. The recrystallization of amylose is apparently little affected by complexation with mono glycerides. Differential scanning calorimetry (DSC) studies of day-old bread crumb show that all the amylose seems to be present in a crystalline state. Complex formation with monoglyceride by the short side chains of amylopectin, however, markedly slow the rate of retrogradation. The half-life for reformation of amylopectin crystals (measured by DSC) is increased twofold to threefold when... 

The amorphous starch phase in bread crumb is far from equilibrium and the formation of ordered structures reduces the free energy of the system. Starch has a strong tendency to associate since the interaction between the starch polymers... 

Staling of white-bread crumb begins with the formation of crystalline structures in amylopectin. The endotherm peak at 60 °C appears again in the thermogram of stored white bread (Fig. 15.52). A state of order arises which corresponds to that of B starch (cf. 4.4.4.14.2) and binds up to 27% of crystal water, which is withdrawn from amorphous starch and proteins. The crumb loses its elasticity and becomes stale. On storage of white bread, the amount of water that can freeze decreases corresponding to the conversion to non-freezing crystal water (Fig. 15.53). 

Gassenmeier, K., ScMeberie, R Potent aromatic compounds in the crumb of wheat bread (French-type). Influence of preferments and studies on the formation of key odorants during dough processing. Z. Lebensm. Unters. Forsch. 201, 241 (1995)... 

Potassium bromate (KBrOj) Oxidizing agent used to improve the baking properties of flour. It enhances the formation of disulfide bonds and improves bread volume and crumb texture. 

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