Starch-water, gluten-water, and flour-water model systems as well as straight-dough bread were investigated with (1)H NMR relaxometry using free induction decay and Carr-Purcell-Meiboom-Gill pulse sequences. Depending on the degree of interaction between polymers and water, different proton populations could be distinguished. The starch protons in the starch-water model gain mobility owing to amylopectin crystal melting, granule swelling, and amylose leaching, whereas water protons lose mobility due to increased interaction with starch polymers. Heating of the gluten-water sample induces no pronounced changes in proton distributions. Heating changes the proton distributions of the flour-water and starch-water models in a similar way, implying that the changes are primarily attributable to starch gelatinization. Proton distributions of the heated flour-water model system and those of fresh bread crumb are very similar. This allows identifying the different proton populations in bread on the basis of the results from the model systems.

Results and DiscussionDuring storage of bread for 168 h, ∆H AP increased while the relative amount of FW decreased (Table 1). Water becomes unfreezable due to inclusion into the amylopectin crystals but also due to inclusion into the continuous, rigid amylopectin network. No amylopectin retrogradation was observed during drying. Crumb firmness increased during storage and drying ( Figure 1).The decreased crumb moisture content during storage did not result in an increased crumb firmness (Figure 1), showing that amylopectin retrogradation was largely responsible for crumb firming during storage. However, the increase in melting enthalpy levelled off after a couple of days of storage (Table 1), while crumb firmness increased further. This points to an additional phenomenon which contributes to crumb firmness.With 1 H NMR, changes in the distribution of protons from water and biopolymers can be observed. During storage of bread, the area of population A (rigid protons) increased due to formation of amylopectin crystals (Figure 2a). In addition, the mobility (T 2 relaxation time) and area of population E (mobile exchanging protons in the formed gel network) decreased during bread storage due to formation of a continuous, rigid amylopectin network and crumb to crust moisture migration (Figure 2a). Bread crumb firming is a complex process. It is generally accepted that amylopectin retrogradation is an important contributor to crumb firming during storage, but there is no direct cause and effect relationship between both processes 1 . Besides formation of amylopectin crystals 1 , water diffusion also affects crumb firmness during storage. Literature is scarce about the impact of such diffusion. It occurs on a macroscopic scale, i.e. from crumb to crust 2 , as well as on a molecular scale, i.e. from gluten to starch 3 . However, the relative importance of water redistribution and amylopectin retrogradation for bread firming is still under debate. Since water related phenomena are involved in crumb firming, the use of low resolution (LR) proton Nuclear Magnetic Resonance ( 1 H NMR) to examine bread crumb holds promise. the objective of this study was to investigate changes during bread storage, thereby distinguishing between the effect of crumb to crust migration and evaporation of water and the effect of amylopectin recrystallization with water incorporation into the resulting starch network. Introduction and Objective ReferencesBread making process Bread was made using a straight-dough method [100.0 g wheat flour (14.0% moisture), 5.3 g compressed yeast, 6.0 g sucrose, 1.5 g NaCl, 57.0 mL water] as described in Bosmans et al. (2012) 4 . Differential scanning calorimetry (DSC) measurementsThe melting enthalpy of retrograded amylopectin (∆H AP ) and the relative amount of freezable water (FW) were determined with DSC 5 . Firmness measurementsCrumb firmness was detected with an Instron 3342 (Instron, Norwood, MA, USA) on fresh, stored (for 168 h) and dried bread crumb 5 . H NMR measurementsProton relaxation measurement...

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The functionality of wheat flour lipids in sponge cakes prepared from flour, sugar, eggs and leavening agents only was investigated by altering their location or content in flour. Hexane (hex) or the more polar hexane:isopropanol (3:2 v/v) (hex:isoprop) were used to impact free flour lipid (FFL) or both FFL and bound flour lipid (BFL) fractions, respectively. Flour from which the FFLs were removed resulted in significantly improved cake volumes and crumb structures. Additional removal of part of the BFLs did not further impact cake quality. Prior contact of flour with hex:isoprop followed by gently removing the solvent broke native interactions between BFLs and starch or gluten and relocated more lipids than did hex. Cakes from flour with relocated lipids had coarse crumb structures. Our study demonstrates that FFLs and relocated flour lipids negatively impact sponge cake quality by disturbing air-liquid interface stabilization during mixing and the early phases of baking.