Bread staling: I.—Experimental study

Abstract

Starting with a typical baker's dough, a model system was constructed in order to examine whether moisture re-distributed itself bet ween the two principal components, gluten and starch, of crumb during ageing.It was estimated that up to 30 % of the moisture associated with thegluten fraction, migrated to the starch during I20 h of storage of the baked system at 2J"c. The rate of migration decreased upproximately exponentially with time. Moisture from the gluten was also found to migrate to the starch during baking, but at an accelerated rate. The rate of moisture migrution in the model system, both at 100 and 2 5 "~. was consistent with a diffusion-controlled process involving migration of the gluten-released moisture to the gluten-starch interface. Experimental results show that staling of bread involves (in addition to the generally accepted retrogradation of the starch) an irreversible modification in the water structure of the gluten, leading to the formation of labile water, which becomes available for absorption by the incompletely gelatinised starch. Since the gluten forms the continuous matrix of the crumb, the modification results in a rigidification or firming process.Separation of the components of dough was achieved by ultra-centrifugation.

Effect of aging and ice-structuring proteins on the physical properties of frozen flour–water mixtures

“…The first distribution has been assigned to water that exhibits strong interactions with gluten and starch (Assifaoui et al, 2006;Engelsen et al, 2001;Kim & Cornillon, 2001;Ruan et al, 1999). Such a statement is rather ambiguous since it is documented in the literature that the molecular interactions of gluten water are distinct from those with starch (Li, Dickinson, & Chinachoti, 1996;Umbach, Davis, Gordon, & Callaghan, 1992;Wang, Choi, & Kerr, 2004;Wilhoft, 1971;Wynne-Jones & Blanshard, 1986). Moreover, as is shown in the inset of Fig.…”

Water dynamics in white bread and starch gels as affected by water and gluten content

“…Bushuk and Winkler (1957) reported that water is bound more to starch than to gluten, due to the higher water sorption capacity of starch. Through separation of the components of dough and measuring the moisture content of each component during baking and storage, Willhoft (1971) suggested that there is more water associated with the gluten than with the starch in the dough, and that the water moves from the gluten to the starch during conventional baking. Using differential thermal analysis (DTA) and differential scanning calorimetry (DSC), several researchers found that the bound water content in dough was independent of flour protein content, added chemicals, amount of damaged starch and mixing time (Davis & Webb, 1969;Daniels, 1975;Bushuk & Mehrotra, 1977a-c).…”

Nuclear Magnetic Resonance Studies of Water Mobility in Bread during Storage

“…Stone (8) noticed that the crisp crust became softer and more leathery during staling, probably owing to migration of moisture from the crumb, or possibly owing to absorption of moisture from the atmosphere (9). Willhoft (6) and Breaden and Willhoft (5) reported that gluten undergoes a transformation resulting in the release of water (once a part of the gluten structure) which becomes absorbed by retrograding starch. Others suggest that water is expelled from the starch matrix due to retrogradation (10).…”