The biggest advantage of ultrafiltration membrane is that it does not use any additives during use. The operating temperature and pH value can be controlled and adjusted according to the processing requirements. At present, ultrafiltration separation technology is used in the production of fruit and vegetable juices, which can achieve the effects of sterilization, clarification and concentration.

Ultrafiltration is a fluid tangential flow and pressure driven filtration process that separates particles by molecular weight. The pore size of the ultrafiltration membrane element is in the range of about 10 to 200 ?. The dissolved substance and the substance having a smaller pore diameter than the membrane can be used as a permeate-permeable membrane, and the substance that cannot penetrate the membrane is gradually concentrated in the discharge.

Application of ultrafiltration in the production of fruit and vegetable juice

Tubular ultrafiltration membrane technology can replace the traditional enzymatic hydrolysis method for fruit juice clarification. The research found that the ultrafiltration technology can separate the juice and pectin, and the separation process is short and normal, which makes the color and flavor of the juice better.

After ultrafiltration and reverse osmosis, the juice can be energy-saving and of good quality. The small molecules such as aromatic components, sugars, amino acids, minerals and water are mostly retained by the ultrafiltration membrane, and the fat-soluble components are retained. Therefore, after the concentrated juice is re-produced, it is not much different from the fresh juice, and the storage period is long. Due to the effect of cold sterilization, and the absence of enzymatic treatment of the undecomposed pectin in the filtrate, long-term storage generally does not occur secondary precipitation.

The quality of ultrafiltration membrane components after clarification of fresh kiwifruit juice by ultrafiltration was studied experimentally. The total antioxidant capacity, ascorbic acid content, suspended solids, turbidity and viscosity were used as indicators to analyze the ultrafiltration process for fresh juice. The total suspended solids and turbidity have a good purifying effect.

In the apple as an experimental material, the polysulfone membrane is used as an ultrafiltration membrane. The experimental results show that the polysulfone membrane with molecular weight cutoff of 10000 retains the aromatic component of Guoguang juice, and almost completely retains 2-methylpropanol, butanol and 2-methylbutanol. As the membrane flux increases, the retention of aromatic components in the juice gradually decreases. The reason is that the adsorption of the aromatic component on the ultrafiltration membrane mainly occurs on the surface of the membrane, and the effect of the PS-80000 membrane with a large non-porous area on the aromatic component is greater than that of the PS-10000.

In the application process of tubular ultrafiltration membrane for decolorizing apple juice, it is proposed to decolorize apple juice by ultrafiltration process. The traditional fruit and vegetable juice processing adopts activated carbon or resin adsorption to decolorize apple juice. Ultrafiltration is undoubtedly a new process. Studies have found that polyether sulfone or polyvinylpyrrolidone membrane is more effective in reducing polyphenols than regenerated cellulose membranes, slowing discoloration and increasing flow rate in the selection of juice decolorizing membranes.

The ultrafiltration technology operates a physical process that is environmentally friendly and has no secondary pollution, and has low energy consumption. The effect of concentration and separation can be achieved without adding any substance.