Pasting, thermal and structural changes of part-baked bread prepared under freezing conditions

In frozen part-baked bread technology, starch is influenced by various processing factors. This study aimed to investigate the effect of part-baking time, freezing rate and frozen storage time on pasting, thermal and structural properties of part-baked bread. Wheat dough was part-baked for 0, 3 or 6 min and frozen at −20 °C using two freezing rates: slow (0.15 °C min⁻¹) or fast (1.45 °C min⁻¹). Next, samples were stored in frozen conditions for 56 days and analysed every 14 days for starch damage, pasting properties, thermal and X-ray analysis. The level of damaged starch increased with 3 min (69.3%), and 6 min (88.8%) of part-baking time for both freezing rates compared to no part-baked. In pasting analyses, peak viscosity decreased 27.3% and 38.4% for 3 and 6 min of part-baking time, respectively, at 0 days of frozen storage; however, this tendency was observed for all frozen storage time. The gelatinisation enthalpy (ΔH_g) decreased as part-baking time increased, showing the maximum reduction at 6 min of part-baked (94.9%). In X-ray diffraction analyses at 3 and 6 min of part-baking, the intensity of the signal increased 4.4% and 10.9%, respectively, probably due to the starch gelatinisation. These results can serve as a valuable guide for developing strategies to enhance the quality of part-baked bread and improve production performance.