Modification Preparation and Hypolipidemic Activity Exploration of Water-soluble Dietary Fiber from Grape Pomace

This study aimed to treat grape pomace-derived soluble dietary fiber (SDF) using two modification methods, optimize the modification parameters, compare the physicochemical properties of SDF before and after modification, and investigate its hypolipidemic effects in hyperlipidemic mice, thereby providing a theoretical basis for in-depth research on grape pomace SDF and food development. Using grape pomace SDF as the raw material, it was subjected to modification by microwave-acid (M-A) and cellulase-ultrasound wave (C-UW) methods. Based on single-factor experiments, response surface methodology was employed to optimize the experimental conditions and determine the optimal parameter combinations for modification. The physicochemical properties (including functional characteristics, cholesterol adsorption capacity, and cation exchange capacity) of unmodified SDF and the two modified SDF were compared. Scanning electron microscopy and Fourier transform infrared spectroscopy analyses were also conducted. Additionally, a hyperlipidemic mouse model was established to explore the hypolipidemic effects of SDF before and after modification. Measurements and analyses were conducted on mouse body weight, four lipid profile indicators, serum ALT and AST activities, liver indices, and histological staining of liver sections. Results showed that the optimal parameter combination for M-A method modified SDF was a solid-to-liquid ratio of 1:24.97, microwave power of 220.56 W, microwave time of 60.24 s, and the yield of SDF was 22.17%. For validation, the process parameters were slightly adjusted to citric acid mass fraction 6%, solid-to-liquid ratio 1:25, and microwave power 240 W, resulting in an average SDF yield of 21.74%, with only a minor deviation of 0.41% from the theoretical yield. For the C-UW-modified SDF, the optimal parameters were: cellulase addition 0.38%, enzymatic hydrolysis temperature 54.04℃, and enzymatic hydrolysis time 28.61 min, resulting in an SDF yield of 28.8%. For validation, the process parameters were slightly adjusted to cellulase addition 0.4%, enzymatic hydrolysis temperature 55 ℃, and enzymatic hydrolysis time 30 min, resulting in an average SDF yield of 28.29%, with only a minor deviation of 0.51% from the theoretical yield. In terms of physicochemical properties, C-UW-modified SDF exhibited significant superiority over unmodified SDF and M-A-modified SDF. SEM results showed that C-UW-modified SDF formed a denser, rod-like structure, while FTIR analysis indicated that the main components and overall chemical structure of the three SDFs remained relatively stable without significant changes. These findings confirmed that C-UW-modified SDF demonstrated better modification effects compared to unmodified SDF and M-A-modified SDF. In the mouse experiments, compared to the model group, C-UW SDF significantly reduced TC, TG, and LDL-C, while significantly increasing HDL-C. Compared to other treatment groups (unmodified SDF, M-A SDF), C-UW SDF showed more pronounced effects in improving the four lipid profile indicators, particularly in reducing LDL-C and increasing HDL-C. Additionally, C-UW SDF exhibited a reducing effect on serum ALT and AST activities, an inhibitory effect on weight gain, and alleviated liver damage, protecting the integrity of hepatocytes. These results confirmed that C-UW SDF was more effective in reducing blood lipid levels in hyperlipidemic mice, laying a foundation for subsequent research on grape pomace SDF and food development.

本研究旨在采用两种改性方法处理葡萄果渣来源的可溶性膳食纤维（soluble dietary fiber, SDF），优化改性参数，对比改性前后SDF的理化性质，并探究其对高脂血症小鼠的降血脂功效，以期为葡萄果渣SDF的深入研究及食品开发提供理论依据。本研究以葡萄果渣SDF为原料，分别采用微波-酸（microwave-acid, M-A）法与纤维素酶-超声（cellulase-ultrasound wave, C-UW）法进行改性处理。在单因素试验基础上，采用响应面法优化实验条件，确定两种改性方法的最优参数组合。对比未改性SDF与两种改性SDF的理化性质，包括功能特性、胆固醇吸附能力与阳离子交换容量，并开展扫描电子显微镜（scanning electron microscopy, SEM）与傅里叶变换红外光谱（Fourier transform infrared spectroscopy, FTIR）分析。此外，本研究建立高脂血症小鼠模型，探究改性前后SDF的降血脂功效，检测并分析小鼠体重、四项血脂指标、血清谷丙转氨酶（ALT）与谷草转氨酶（AST）活性、肝脏指数，以及肝脏组织切片的组织学染色情况。结果显示，微波-酸法改性SDF的最优参数组合为料液比1:24.97、微波功率220.56 W、微波时间60.24 s，此时SDF得率为22.17%。验证实验中，将工艺参数微调为柠檬酸质量分数6%、料液比1:25、微波功率240 W，最终SDF平均得率为21.74%，与理论得率仅相差0.41%，偏差极小。对于纤维素酶-超声法改性SDF，最优参数为：纤维素酶添加量0.38%、酶解温度54.04℃、酶解时间28.61 min，此时SDF得率为28.8%。验证实验中，将工艺参数微调为纤维素酶添加量0.4%、酶解温度55℃、酶解时间30 min，最终SDF平均得率为28.29%，与理论得率仅相差0.51%，偏差极小。理化性质方面，纤维素酶-超声法改性SDF的各项性能显著优于未改性SDF与微波-酸法改性SDF。扫描电子显微镜结果显示，纤维素酶-超声法改性SDF形成了更为致密的棒状结构；傅里叶变换红外光谱分析表明，三种SDF的主要成分与整体化学结构相对稳定，未发生显著变化。上述结果证实，相较于未改性SDF与微波-酸法改性SDF，纤维素酶-超声法改性SDF具有更优异的改性效果。小鼠实验结果显示，与模型组相比，纤维素酶-超声法改性SDF可显著降低总胆固醇（total cholesterol, TC）、甘油三酯（triglyceride, TG）与低密度脂蛋白胆固醇（low-density lipoprotein cholesterol, LDL-C）水平，并显著升高高密度脂蛋白胆固醇（high-density lipoprotein cholesterol, HDL-C）水平。相较于其他处理组（未改性SDF、微波-酸法改性SDF），纤维素酶-超声法改性SDF在改善四项血脂指标方面效果更为显著，尤其在降低LDL-C与升高HDL-C方面表现突出。此外，纤维素酶-超声法改性SDF可降低血清ALT与AST活性，抑制体重增长，并缓解肝脏损伤，保护肝细胞完整性。上述结果证实，纤维素酶-超声法改性SDF可更有效地降低高脂血症小鼠的血脂水平，为后续葡萄果渣SDF的研究及食品开发奠定了基础。