葡萄汁膜浓缩工艺及其酚类物质膜污染特征

Concentration of grape juice and fouling characteristics of phenolic compounds during ultrafiltration and nanofiltration

以鲜榨葡萄汁为原料,采用超滤、纳滤等膜技术浓缩多酚富集葡萄汁。通过对不同超滤和纳滤膜的膜通量和总酚截留率进行对比,确定最佳条件浓缩工艺,并分析了浓缩前后总糖、总酚和抗氧化能力等指标的差异。结果确定最佳浓缩工艺为5000 Da超滤膜+150 Da纳滤膜组合,超滤和纳滤的压力、流速、时间分别为1 MPa,5 m/s,2 h和5 MPa,5 m/s,2 h。总酚截留率随着时间和压力的增加而上升,随着流速的增加而下降。膜法浓缩获取的多酚富集浓缩葡萄汁总糖质量浓度为70.01 g/L,总酚质量浓度为3.75 g/L,分别达到原汁的202.1%和328.3%。同时,基于Resistance-in-series模型对葡萄汁中的主要酚类物质形成的膜污染机制进行分析。纳滤过程中R m是主要阻力,占60%~70%,7种酚类物质以香豆酸造成的不可逆污染阻力最高,以儿茶素和没食子酸造成的可逆污染阻力最高。

In this study,fresh grape juice was concentrated to polyphenols enriched grape juice by ultrafiltration(UF)and nanofiltration(NF)technology.Optimum conditions were determined based on comparison of membrane flux and retention of total phenols with different membranes,which was a combination of 5000 Da UF membrane and 150 Da NF membrane.The pressure,flow rate and time were 1 MPa,5 m/s and 2 h for UF and 5 MPa,5 m/s and 2 h for NF.The retention efficiency of total phenols increased with increasing time and pressure,but decreased with increasing flow rate.Concentrations of total sugars and total phenols in the concentrated grape juice were 70.01 g/L and 3.75 g/L,respectively,which were almost 202.1%and 328.3%of that in original juice,respectively.Besides,mechanism of membrane fouling caused by main phenols in the grape juice was investigated based on resistance-in-series model.The results showed that R m was the main resistance in NF,accounting for 60%-70%.Among all the phenolic compounds,coumaric acid and catechin and gallic acid showed the highest irreversible and reversible resistance,respectively.