探讨高压均质次数对小米糠不溶性膳食纤维 (insoluble dietary fiber, IDF) 的结 构性质及水纤维分散体物理稳定性的影响. 采用解淀粉芽孢杆菌液态发酵小米糠 (30 ◦C, 180 r/min, 48 h) 制备膳食纤维 (dietary fiber, DF), 并对其进行高压均质改性. 测定 IDF 改 性前后的理化性质, 通过傅里叶变换红外光谱和 X 射线衍射分析样品结构, 同时测定高压均 质前后水纤维分散体的粒度分布、黏度值、Zeta 电位值及物理稳定性. 解淀粉芽孢杆菌发酵 小米糠得到的 IDF 在经过 0、5、10、15、20、25 次高压均质后, 持水力和膨胀力明显提升, 其 中高压均质 25 次与未经高压均质的 IDF 相比, 持水力和膨胀力分别提升了 80.5% 和 81.84%.

通过傅里叶红外光谱图发现: 高压均质并未使 IDF 产生新的化学官能团结构, 但部分吸收峰 的强度减弱; 木质素及半纤维素发生降解与重排, 晶体的有序度降低. 结合 X 射线衍射结果分 析, 虽然小米糠 IDF 表现出天然 Ⅰ 型纤维素的特征, 但随着高压均质次数的增多, IDF 的结 晶度下降. 混合水纤维分散体中 IDF 的平均粒径随高压均质次数的增加而逐渐减小, Zeta 电位绝对值逐渐增大, 当均质次数达到 20 次时, 水纤维分散体具备良好的物理稳定性. 随着高压均质次数的增多, 水纤维分散体的表观黏度逐渐增大, 均表现出剪切稀化的行为. 高压均质可以改善小米糠 IDF 的结构及理化性质, 提升水纤维分散体的稳定性.

This study investigated the effects of number of times of high-pressure homogenization on the structural properties of insoluble dietary fibres (IDFs) derived from millet bran fermented using Bacillus amylolyticus and the physical stability of aqueous IDF suspensions. Millet bran dietary fibres (DFs) were obtained through liquid-state fermentation (30 ◦C, 180 r/min, 48 h) using Bacillus amylolyticus and further modified via high-pressure homogenization. The physicochemical properties of the homogenised IDFs were evaluated using various techniques, and their structural characteristics were analysed through Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The particle size distribution, viscosity, zeta potential, and physical stability of the IDF suspensions in water were evaluated before and after high-pressure homogenization. The water-holding capacity and swelling capacity of the IDFs obtained via millet bran fermentation using Bacillus amylolyticus increased significantly after 0, 5, 10, 15, 20, and 25 cycles of high-pressure homogenization. In particular, the water-holding capacity and swelling capacity increased by 80.5 and 81.84%, respectively, after 25 cycles of high-pressure homogenization compared with those of the untreated IDFs. FTIR spectra revealed that no new chemical functional groups were generated after high-pressure homogenization, but the intensities of certain FTIR peaks were weakened, indicating the partial degradation and rearrangement of lignin and hemicellulose, and decreased ordering degree of the crystalline domains. Combined with the XRD results, it can be inferred that, although the millet bran IDFs exhibited the characteristics of natural type I cellulose, their crystallinity decreased with increasing cycles of high-pressure homogenization. The average particle size of the IDFs in aqueous suspensions gradually decreased with the increase in high-pressure homogenization recirculation, and the absolute zeta potential value increased gradually. When the homogenization recirculation reached 20 times, the aqueous fibre suspension exhibited good physical stability. Moreover, as the cycle number of high-pressure homogenization recirculation increased, the apparent viscosity of the aqueous IDF suspension increased steadily, and all samples exhibited shear-thinning behaviour. High-pressure homogenization can improve the structure and physicochemical properties of IDFs derived from fermented millet bran and enhance the stability of aqueous IDF suspensions.