采用自行研制的脉冲电场设备, 利用傅里叶变换红外光谱(FTIR)比较研究了脉冲电场(PEF)和热处理对大豆分离蛋白(SPI)分子结构的影响。 结果表明: 50 kV·cm-1的脉冲场强处理引起SPI分子内和分子间氢键增强, 分子中C—O—O糖苷键伸缩振动和PO, P—O—C伸缩振动增强, 且其增加值与PEF处理时间呈正相关。 研究发现较短时间(1 600 μs)PEF处理导致了SPI分子结构中α-螺旋和β-折叠分别减少了5.9%和0.7%, β-转角和侧链结构分别增加了7.5%和9.6%； 处理时间延长至2 400 μs, 其α-螺旋和β-折叠减少量增至6.0%和5.6%。 对比而言, 热处理对SPI分子结构中C—O—O糖苷键伸缩振动和PO, P—O—C伸缩振动的影响程度较大, 而对蛋白质二级结构影响程度较小: 90 ℃热处理30 min, α-螺旋和β-折叠分别减小5.1%和6.6%, β-转角结构增加19.1%。 由此可以认为PEF和热处理对SPI的影响机理是不一样的。

The effects of pulsed electric field (PEF) under 50 kV·cm-1 as well as heat treatments on the secondary structure of soy protein isolate (SPI) were investigated by Fourier transform infrared (FTIR) method in the present paper. A set of self-designed and made PEF equipment was used. It was demonstrated from the FTIR spectra that the PEF treatment under 50 kV·cm-1 had induced the increase in hydrogen bonds amidst in the intermolecule and intramolecule of SPI, and the increase in C—O—O bonds stretch vibration and the PO or P—O—C stretch vibration, which is positive relative to the increase in the time of PEF treatment. It was shown that after PEF treatment, the ratio of α-helix and β-sheet structure in SPI was decreased by 5.9% and 0.7%, respectively. On the other hand, the ratio of β-turn and side chain vibration structure was obviously increased by 7.5% and 9.6% at the treatment time of 1 600 μs, respectively. Comparatively the effect of heat treatments with 90 ℃ for 30 min on the C—O—O bonds stretch vibration and the PO or P—O—C stretch vibration is more evident, but the effect of which on the secondary structure of SPI is less. So it is concluded that the effect mechanism of PEF and HT on SPI structure is significantly different.