应用核磁共振法研究豆豉发酵过程中水分的变化规律

Study on variation of moisture in lobster sauce during fermentation by nuclear magnetic resonance

核磁共振横向弛豫时间（T2）反映不同发酵时间的豆豉制品中氢质子组分及运动性，从而可得出不同发酵时间的豆豉制品中水分的变化规律。采用CPMG（CarrPurcellmeiboom—gill）测试，经PQ001分析软件及CPMG序列采集豆豉T2信号，得到他谱图。谱图显示豆豉中氢质子大致分为4种相态：T21（0．01～1．52ms）、T22（1．52N7．05ms）、T23（7．05-100ms）、T24（〉100ms）。从组分含量分析得出，随着厌氧发酵的进行、微生物分泌的酶系对蛋白质为主的原料的分解、微生物的代谢活动、风味物质的形成，结合水含量不断减小，不易流动水即细胞内水存在相互转化的过程（T22与T23），自由水含量也有一定程度减小。随着发酵的进行，豆豉的鲜味成分大量形成、氨基酸态氮显著提高，风味物质显著增加，豆粒软化色泽加深。利用核磁共振法能够间接反映发酵过程中豆豉风味形成、质构等指标的变化。

Nuclear magnetic resonance （NMR） transverse relaxation time （T2） reflects the hydrogen proton component and motility in fermented soybean products with different fermentation time, and it was used to discover the variation of moisture in fermented soybean products. The T2 signal of fermented soybean was collected by PQ001 analysis software and CPMG （Carr Purcell meiboom -gill） sequence to obtain T2 spec- trum. The spectrum showes that the hydrogen proton in fermented soybean roughly divided into four phases ： T21 （0.01- 1.52 ms）, T22（ 1.52-7.05 ms）, T23 （7.05- 100 ms）and T24（ 〉 100 ms）. Through the com- ponent content analysis, along with the anaerobic fermentation, decomposition of protein - based materials by microbial enzymes, metabolic activity of microorganisms and the formation of flavor substances, the combined water reduced continuously. There was a process of mutual transformation of water in cells （ T22 and T23）, and the content of free water also decreased in a certain extent. During the fermentation, the umami ingredients increased largely, amino nitrogen improved significantly, flavor substances increased significantly, the color of soften soybean deepened. NMR method can indirectly reflect the formation of the flavor and the change in texture and other index during fermentation.