Application Of Coupled Membrane Separation Technology In Low Lactose Milk Powder

As one of the main food sources for infants and young children,milk powder contains rich nutrients such as fat,protein,amino acids,calcium,iron,and zinc,which are needed by the human body.But for special needs(lactose intolerant patients),milk powder also contains the component(lactose)that cannot be absorbed.People with special needs not only cannot consume milk powder effectively,but can also cause symptoms such as non-infectious diarrhea.Lactose intolerance has been a widespread worldwide problem;accordingly,the demand for lactose free or low lactose dairy products is growing.Therefore,this project designs an integrated membrane separation engineering system which is suitable for the coupling of ultrafiltration,nanofiltration and electrodialysis.On the premise of basic guarantee of the original ingredients(protein,fat,inorganic salt and some amino acids,etc.)of milk,lactose is accurately separated,and finally high-quality low lactose milk powder is prepared.In this study,fresh milk was used as raw material.Firstly,ultrafiltration membrane technology was used to extract macromolecular nutrient components(such as protein,fat and large amino acids).Secondly,mineral salts were separated by electrodialysis.Subsequently,the lactose was extracted and separated by nanofiltration.Finally,the effective components of ultrafiltration and electrodialysis were mixed,and low lactose milk powder was prepared by spray drying technology.Low lactose milk powder(lactose content less than 0.2%)and high purity milk powder(95.7%)were obtained.The whole membrane separation process is based on the physical pore size screening mechanism,without adding any chemical reagents that affect the physical and chemical properties of milk.In addition,in the application process of separation membrane,the presence of various mineral ions has a huge impact on the improvement of separation efficiency.In order to further study the relationship between mineral ions and proteins in milk during membrane separation.In this study,single protein and pure whey protein were used as raw materials,and different single cations(K+,Ca2+,Na+,and Mg2+)were added to investigate the relationship between the existence of ions in protein structure and morphology changes and separation performance.The results show that several multivalent metal ions can induce protein aggregation and produce metal colloids easily under the condition of high ion concentration.The mixing experiments of different ions and proteins also conform to the description of Hofmeister effect.It is worth noting that the ultrafiltration flux of desalting whey and ionic protein solution has a special lowest point(the conductivity is about 150 μs/cm).This phenomenon is in line with the view that small particles are easier to deposit on the membrane than large particles on the membrane surface.Therefore,the economic benefit of the process can be improved by adjusting the sequence of the process.