核磁共振及其成像技术研究面粉吸水率及其形成过程

Study on the Absorbability and Formation of Flour with NMR and MRI Techniques

利用核磁共振及其成像技术研究了面筋含量、含水量、添加物、搅拌与面团中水的状态之间的关系。水分状态的测定使用自旋-晶格和自旋-自旋弛豫时间(T1和T2)。在面团搅拌过程中,在初期T2*和相应的质子密度值随着搅拌时间的延长而快速减小,说明自由水加入到面粉中后迅速与面粉中的蛋白以及其他成分发生了水合作用。T2*与搅拌时间的曲线体现了面团的这个搅拌过程,从中可以直观的得到面团的最佳搅拌时间。搅拌时间受水分含量的影响,并且不同面筋含量的面粉搅拌稳定时间也不相同。面筋含量与搅拌时间成才正比。高温有利于面团的形成,并且影响面团中水分的流动性。通过低、中、高三种不同面筋含量面粉吸水率与NMR自旋—晶格弛豫时间关系的研究,实验结果发现T1以及T1幅度随水分含量的增加而增加,随面筋含量的增加而减少,并且得到了T1与吸水量之间的关系曲线,不同面筋含量面粉的最佳吸水量:湿面筋含量25.4%面粉的吸水量为55.0%;湿面筋含量30.4%面粉的吸水量为57.5%;湿面筋含量35.8%面粉的吸水量为60%。

The relationship between gluten contents, stiring, hydration, and the state of water in flour dough were studied with NMR and MRI techniques. The state of water was measured using spin-lattice and spin-spin relaxation times, or T1 and T2 respectively. In stiring period, T2＊ values （or the apparent T2 obtained with single 90 degree pulse sequence） and the corresponding proton density decreased rapidly initially with increasing silting time, indicating that the bulk water added to the flour was rapidly incorporated into the flour, hydrating the proteins and other components in the flour. The curve between T2^＊ and mixing time showed the formation process of dough that can direct the optimal stiring time in dough. Stiring time was also affected by moisture content, however, there was no different among different content of gluten. The date shows that the stable time was different with the different of gluten content in dough, the higher the gluten, the longer stable time. Higher temperature increased the formation of dough. The water mobility was also found to be affected by silting temperature. With two component fitting, it was found that T1 values and T1 amplitudes increased with increasing moisture content and decreasing gluten content, also found that there was solid relationship between T1 and water absorption in flour which decided the optimal moisture content in different gluten flour, with the gluten content of 25.4%, 30.4%, 35.8% in flour the optimal moisture absorption is 55%, 57.5% and 60% respectively.