Chinese steamed bread: Packaging conditions and starch retrogradation

Background and objectives The starch retrogradation of Chinese steamed bread (CSB) under different packaging conditions (sealed package [SP], vacuum package [VP], and thermal-vacuum package [T-VP]) was compared in the present study. Parameters including moisture content, moisture migration, starch granule structure, and starch retrogradation were monitored by NMR, SEM, XRD, and FT-IR. Findings During storage, T-VP steamed bread kept higher water content and had longer shelf life compared to SP and VP. T-VP hindered the interactions among water molecules, gluten, and starch, thus relatively increasing the mobility of water molecules represented by T-23 in NMR tests compared to SP. T-VP decreased the speed of CSB starch granules getting narrowing in SEM, maintaining a good taste of steamed bread. Results from FT-IR and XRD suggested a lower retrogradation rate of CSB starch with T-VP as compared to SP and VP, and the retrogradation of CSB starch was affected by free water during storage. Conclusions Thermal-vacuum package could delay the speed of water desorption, blocked the interaction among water molecules, gluten and starch and slowed the adhesion between starch granule, thus retard starch retrogradation of CSB.