Effect of Steaming Time on Structural Characteristics of Pork Steamed Stuffed Bun Wrapper with Different Gluten Content

The industrial production of steamed stuffed bun frequently encounters challenges such as dry wrapper and foaming after steaming. To further investigate the influence of the steaming process on the structural characteristics of steamed stuffed bun, this study utilized flour with protein contents of 8%, 10%, and 12% as raw materials. A combination of experimental techniques, including texture analysis, low-field nuclear magnetic resonance (LF-NMR), Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), was employed to analyze the structural characteristics, water distribution, secondary structure, tertiary structure, and microstructure of steamed stuffed bun wrapper at various steaming time points. The results demonstrated that the specific volume, elasticity, and resilience of the steamed stuffed bun wrapper increased with both the extension of steaming time and the increase in protein content. Additionally, the levels of bound water and free water rose, enhancing water fluidity. With the rise in disulfide bond content, the disulfide bonds transitioned from t-g-t and g-g-t structures to g-g-g structures. When the protein content of the steamed stuffed bun wrapper reached 12%, the β-sheet and β-turn structures increased by 4.58% and 8.36%, respectively, as steaming time progressed. At a steaming time of 16 minutes, the β-sheet and β-turn structures increased by 0.31% and 5.06%, respectively, with increasing protein content. The tertiary structure of gluten proteins became more compact as steaming time increased. Simultaneously, non-covalent interactions contributed to the formation of a starch-protein network, with non-covalent bonding forces strengthening as steaming time extended. The crystallinity of starch particles decreased, along with a reduction in the intensity of diffraction peaks. As cooking time increased, starch particles diminished in size and became increasingly embedded within the damaged gluten matrix, forming a starch-gluten protein network system. Furthermore, higher gluten proteins content resulted in tighter integration between starch particles and gluten proteins. These findings provide a theoretical basis for addressing issues related to the hardness and foaming of steamed stuffed bun and offer data support for optimizing process parameters and industrial production.