基于LF-NMR方法分析电子束辐照技术影响大豆浓缩蛋白粉水分的变化

本研究借助低场核磁共振技术(low field nuclear magnetic resonance,LF-NMR)测定经不同电子束辐照(electron beam irradiation,EBI)剂量处理后的大豆浓缩蛋白粉的水分分布信息,并通过热变性实验和傅里叶变换红外光谱(Fourier transform infrared,FT-IR)初步探究了EBI对大豆浓缩蛋白粉水分变化的影响及其变化机制。结果表明,大豆浓缩蛋白粉中的主要水组分为与大豆蛋白分子紧密结合的结合水(T_(21),占97.0%±0.7%)。随着EBI剂量的增加,结合水和总水分含量均先增大后减小,在5.40 kGy时达到最大值。经热变性实验和FT-IR光谱图分析得知EBI处理不会改变大豆浓缩蛋白粉的变性温度,但是能引起结合水中的O-H基团与氨基酸中的C=O所形成的分子内H键以及分子间H键振动增强。这些结果不仅表明EBI可通过改变大豆蛋白分子内和分子间的H键作用来影响其水分分布及含量,还为进一步探究经EBI处理的蛋白类食品中的水分迁移机制奠定了基础。

Effect of Electron Beam Irradiation on Water in Soybean Protein Concentrate Powder as Evaluated by LF-NMR

Low-field nuclear magnetic resonance (LF-NMR) was used to determine water distribution in soybean protein concentrate powder treated by different doses of electron beam irradiation (EBI). Additionally, a thermal denaturation experiment and Fourier transform infrared (FT-IR) spectroscopy were used to explore the effect of EBI on changes in water components of soybean protein concentrate powder and to determine its mechanism. The results showed that bound water (T21, 97.0%±0.7%) was the main water component of soybean protein concentrate powder. Both bound and total water contents initially increased and then decreased with increasing dose of EBI, with the maximum content reached at 5.40 kGy. The thermal denaturation experiment and FTIR spectra showed that the EBI treatment did not alter the denaturation temperature of soybean protein concentrate powder; however, it enhanced the vibration of intramolecular and intermolecular hydrogen bonds, which were formed by O-H and C=O groups in bound water and amino acids, respectively. These results suggested that the EBI treatment affected the water distribution and content of soy protein by altering the intramolecular and intermolecular hydrogen bond interactions in soybean protein molecules. The study provides a theoretical basis for further studies on the mechanism of moisture transfer in protein foods treated by EBI.