小麦粉面团形成过程水分状态及其比例变化

为揭示小麦粉面团形成过程水分状态和比例、面团结构的变化,以及这种变化与粉质仪和拉伸仪表征的质量特性之间的关系;认识面团形成过程表征筋力强弱的物质基础和变化机理。选用中筋(宁春4号)和强筋(师栾02-1)小麦品种为试验材料,利用低场核磁共振技术测定粉质仪和面过程、拉伸仪醒发拉伸过程不同时间点面团水分状态和比例的变化;利用红外显微成像技术分析面团形成过程不同取样点蛋白质和淀粉的分布及结构变化。结果表明,面粉原料中主要为弱结合水。面粉在粉质仪加水搅拌形成面团后,水分状态和比例发生显著变化,面团中的水可以分为强结合水(T_(21))、弱结合水(T_(22))和自由水(T_(23))。面团搅拌形成过程中,中筋小麦品种宁春4号面团中的强结合水比例显著降低;师栾02-1的强结合水的弛豫时间在和面终点消失,弱结合水的弛豫时间显著延长,而自由水的比例显著增加(P0.05)。强筋小麦粉强结合水的保持时间较长。拉伸过程加盐和不加盐对同一取样点、同一种水分状态之间的水分弛豫时间和比例无显著影响;宁春4号自由水的弛豫时间在加盐和不加盐处理时都显著缩短(P0.05)。湿面筋含量高、筋力较强面团的蛋白质网络结构致密。粉质仪和面过程强结合水和弱结合水弛豫时间和比例的变化,与面筋含量和强度有关。该结论可为面制品加工过程和面工艺选择与优化等方面提供一定的理论参考。

Changes of water status and proportion during wheat flour dough mixing

The purpose of this study was to investigate the changes of water state, proportion and structure during dough mixing and resting in order to establish a relationship between those changes and dough quality properties during dough mixing and resting using Farinograph and Extensograph, which helps to understand the dough development mechanism for flour with different gluten strength. Two wheat varieties (Ningchun4 and Shiluan02-1) with different gluten strength were selected as experimental materials. Water state (T2) and relative proportion (A2) in dough were investigated at different time during dough mixing, and dough resting and stretching by Low-Field Nuclear Magnetic Resonance (LF-NMR). Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance micro (FTIR-ATR) was used to analyze the distribution of starch and protein and the structural changes of protein at different sampling points during the dough mixing. The results showed that water in raw flour were mainly less tightly bound water (T22). While flour was mixed with water in Farinograph to dough development time, three types of water, tightly bound water (T21), less tightly bound water (T22) and free water (T23) were found in the dough. With longer mixing time, the relative proportion of tightly bound water (A21) in Yongliang 4 significantly decreased; transverse relaxation time of tightly bound water (T21) in Shiluan 02-1 did not show by the end of the mixing, transverse relaxation time of less tightly bound water (T22) was significantly prolonged, while the relative proportion of free water (A23) was significantly increased (P<0.05). Water states and proportion for dough mixed with salt or without salt showed no significant changes during dough resting and stretching (P<0.05). After resting, the transverse relaxation time of free water (T23) in Yongliang4 was significantly shortened (P<0.05). The network of dough with higher gluten content was more compact in dough structure. The changes of the relaxation time and proportion of tightly bound water and less tightly bound water during mixing were related to the gluten content and strength. During dough mixing, the relaxation time of strongly bound water (T21), extended or disappeared by the end of mixing. The relative proportion of free water (A23) increased significantly. Strong gluten wheat flour had a longer retention time of strongly bound water. The changes of relaxation time and ratio of strongly bound water and weakly bound water were related to the gluten content and strength. The essences of flour quality characterized by Farinograph were the change of gluten network structure and the tolerance degree of kneading during dough mixing. The changes of water binding state and proportion during dough formation could be effectively characterized by LF-NMR technology. The results can provide some theoretical basis for the selection and optimization of mixing processing.