Molecular dynamics of starch and water during bread making monitored with temperature-controlled time domain ¹H NMR

Time domain proton nuclear magnetic resonance (TD ¹H NMR) was applied in a temperature-controlled mode to in situ study the timing and extent of starch transitions and water redistribution during bread making. Changes in proton population areas during initial baking (≤ 60 °C) were attributed to water absorption by starch and some initial amylose leaching. During subsequent heating (60-90 °C), proton population areas changed because of amylopectin crystal melting and amylose leaching. Granule swelling and amylose leaching increased the system's viscosity and thereby decreased the proton mobility. After crumb setting at about 65 °C, proton mobility increased with a temperature dependence according to Arrhenius' law. During cooling, amylose crystallization increased the portion of rigid protons and decreased the gel network's proton mobility. The uniqueness of this study is that differential scanning calorimetry, colorimetric and gravimetric analyses underpinned NMR data interpretation and the usefulness of the online method to study molecular dynamics during bread making.