以紫洋葱为原料，利用超滤技术对洋葱汁进行澄清。研究了超滤操作压力、操作温度、料液流速对膜通量的影响，比较了超滤对洋葱汁理化性质和抗氧化活性的影响。结果表明：当超滤膜的工作压力为137．90 kPa，料液流速为3．9 L／h，操作温度为35℃时，膜通量最大。经过超滤，洋葱汁中的蛋白质和总糖分别减少了99．19％和10．37％，浊度由16．85 NTU提高到7．64 NTU，而还原糖、Vc等小分子物质得到较好的保留。超滤前后洋葱汁的抗氧化能力都显著减小。因此，超滤可用于洋葱汁的加工，除去其中导致洋葱汁浑浊的部分物质。如果要保持超滤洋葱汁较高的抗氧化能力，可以采用较高截留分子量的超滤膜。%Ultrafiltration technology is used to clarify purple onion juice.The effects of operating pressure,operating temperature,liquid velocity on permeating flux are studied.The physical and chemical characteristics of onion juice before and after ultrafitration are compared.The results show that permeating flux of ultrafiltration is the maximum when the pressure is 137.90 kPa,operating temperature is 35 ℃,and liquid flow rate is 3.9 L/h.After ultrafitration,the proteins and total sugars in onion juice are decreased by 99.19% and 10.37% separately;the turbidity of onion juice is increased from 16.85 NTU to 7.64 NTU.Ultrafitration could preserve reducing sugar,Vc in onion juice.However,the antioxidant activities of onion juice are reduced before and after ultrafiltration. Ultrafiltration can be used to produce onion juice and remove parts of turbidity materials.If higher antioxidant ability of onion juice wanted to be kept,the ultrafiltration membrane with higher cut-off molecular weight can be adopted.
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