面条蒸制过程中水分迁移及糊化特性

运用低场核磁共振、核磁成像、快速黏度分析和光学显微镜研究蒸制过程中面条的水分分布、迁移、糊化特性及微观结构的变化。对水分含量、弛豫时间（T2）、质子密度（M2）和糊化特性进行相关性分析。结果表明：面条中的水分主要以弱结合水的形式存在。在蒸制过程中，水分由面条外部向内部迁移，总水分、弱结合水和深层结合水含量整体呈现先增加后稳定的趋势，深层结合水增长趋势缓慢；弱结合水自由度逐渐增大。面条峰值黏度、衰减值随蒸制时间延长呈下降趋势。观察面条微观结构发现，蒸制使面条淀粉糊化，体积变大，表层淀粉糊化程度高于内层。相关性分析结果表明，水分含量与T22、M22和M总呈极显著正相关（P＜0.01）；水分含量、T22、M22及M总均与峰值黏度、衰减值、最终黏度呈显著负相关（P＜0.05）或极显著负相关（P＜0.01）。

Moisture Migration and Pasting Profiles of Noodles during Steaming

Low field nuclear magnetic resonance (LF-NMR), magnetic resonance imaging (MRI), a rapid viscosity analyzer (RVA) and an optical microscope were used to study the moisture migration, water status, pasting properties and microstructure of noodles during steaming. The correlation among moisture content, transverse relaxation time (T2), proton density (M2) and pasting properties was also analyzed. The results showed that less tightly bound water was the major component of the total moisture in steamed noodle. During steaming, moisture migrated from the surface to the interior until reaching the core. Moisture content and the proportions of less tightly bound water and tightly bound water increased until reaching a plateau; the proportion of tightly bound water showed a slower increase and the mobility of less tightly bound water gradually rose. Both peak viscosity and breakdown decreased with the increase of steaming time. The microscopic investigation showed that starch granules swelled, and became greater in size. Moreover, starch granules in the central region of steamed noodles had a lower degree of gelatinization than in the external region. Correlation analysis showed that moisture content was highly significantly correlated with T22, M22 and Mtotal (P < 0.01), and each of these was significantly (P < 0.05) or extremely significantly (P < 0.01) with peak viscosity, breakdown and final viscosity.