该研究采用不同浓度的Na+,在不同超滤时间点调控乳清蛋白超滤过程,缓解膜污染,提高膜超滤效率。研究发现在超过滤0、4、8 min时分别加入10、15、10 mmol/L可以有效提高超滤在24 min时的膜通量,膜表面蛋白含量降低30%左右。离子强度高于20 mmol/L时导致蛋白结构收缩和聚集,膜孔堵塞,通量降低。在超滤0 min时,加入10 mmol/L的Na+,超滤24 min时,β-折叠含量降低65%。红外光谱显示膜表面蛋白的CO伸缩振动增强,酸性氨基酸暴露;拉曼光谱显示与芳香族和脂肪族氨基酸有关的C—H振动在波数2 930~2 933 cm-1处显著降低,说明膜表面蛋白的亲水性增加。因此,Na+调控的时间点和浓度对膜超滤效率的提高具有重要的意义。
This study used different Na+ concentrations to regulate the whey protein ultrafiltration process under different ultrafiltration time conditions, which was to reduce membrane fouling and increase filtration efficiency. It was found that at the membrane filtration time of 0 min, 4 min, and 8 min, the Na+ was added with the concentration of 10 mmol/L, 15 mmol/L, and 10 mmol/L, the membrane filtration flux at 24 min could increase, and protein content on membrane surface reduced approximately 30%. The ionic strength was higher than 20 mmol/L, leading to protein contraction and aggregation, which could block membrane pores and flux reduction. At the filtration time of 0 min, 10 mmol/L Na+ was added, and the content of the β-sheet decreased by 65% at ultrafiltration for 24 min. The Fourier transform infrared spectroscopy (FTIR) results showed that the CO stretching vibration of the membrane surface protein increased, which was related to the exposure of acidic amino acids in the protein. Raman spectra showed that the C—H vibration of aromatic and aliphatic amino acids at 2 930-2 933 cm-1 significantly reduced, which indicated that the hydrophilicity properties of the protein increased on membrane surface proteins. Therefore, the regulation of ultrafiltration time and the concentration of Na+ addition are of great significance in improving the efficiency of the whey filtration process.
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