Study On Manufacturing Process Of Micellar Casein Concentrate Powder By Membrane Separation Technology

Micellar casein concentrate powder can be produced by membrane fractionation of micellar caseinand serum protein in skim milk, evaporation and spray drying process. Compared with the traditionalcaseinates produced by acid precipitation or rennet coagulation, micellar casein concentrate powderretains the native micellar casein and shows excellent solubility, foaming and good flavor. Micellarcasein concentrate has been applied for cheese manufacturing, high protein functional beverage makingand pastry, and it can also be used as coffee whitener, dietary alternatives and body-building foods andso on. So it has a wide prospect of application. The main objective of this study was to successfullydevelop a pilot scale production process for micellar casein concentrate powder and facilitate its rapidadoption and manufacturing in China’s dairy plants. This study was carried out following the micellarcasein concentrates powder production line, including the comparison of micellar casein and serumprotein separation by different membranes, the diafiltration process parameters of skim milk formicellar casein proteins and serum proteins separation by20nm tubular stainless steel membrane, spraydrying process parameters for micellar casein concentrates, the micellar casein concentrate powdermanufacturing in pilot scale process and the reclamation of by-products. The study showed us that:（1） the20nm pore sized tubular stainless steel membrane is the optimum selection for separation ofmicellar casein and serum proteins in skim milk. Compared with the100nm pore sized stainless steelmembrane and20nm hollow fiber ceramic membrane, the20nm pore sized tubular stainless steelmembrane had the highest membrane flux (56.62kg·m^-2·h^-1), permeates of20nm pore sized tubularstainless steel membrane had the highest clarity, in which the casein protein content was lowest （0.05%）and the percentage of casein loss was also lowest （1.23%）.（2） The optimum operating parameters for20nm pore sized tubular stainless steel membrane wasinlet pressure of2×10⁵Pa and feed temperature of50℃. The best concentration factor was3during theskim milk diafiltration process for separation of micellar casein and serum proteins. When theconcentration factor was3, after the diafiltration process with3stages, the percentage of casein in trueprotein and true protein in total solids achieved was91.17%and82.48%, respectively. At the end ofdiafiltration, the percentage decline of pure water flux was37.97%. After the membrane was cleaned by2%sodium hydroxide solution and0.5%nitric acid solution, the pure water flux recovered to98.48%ofthe original level.（3） The optimum atomizing pressure, feed flow rate, feed temperature, and inlet temperature duringspray drying of micellar casein concentrates with total solids of26.17%were1.5×105Pa,1.5kg/h,60℃, and140℃, respectively. When the micellar casein concentrate was spray dried under theseconditions, there was no sticking phenomenon on the chamber wall, the concentrate was atomized intovery small liquids uniformly. The micellar casein concentrate powder after drying, had a bright whitecolor and thick milk fragrance. The water content and solubility of this powder was4.18%（wt./wt.） and82.17g, respectively.（4） When the skim milk was processed with the combination of3×,3-stage difiltration and spray drying in a pilot scale, the micellar casein concentrate powder with protein content>80%and thepercentage of casein in true protein>90%was obtained. Reclamation of serum protein in serum byultrafiltration, the SPC42can be successfully made. After the permeates of ultrafiltration were processedwith nanofiltration and evaporation,35°Bé concentration of liquid lactose was obtained. Thenanofiltration permeates can be processed for reverse osmosis water, the conductivity of pure water was450μs/cm and it be added into the diafiltration process for recycle use.（5）This study successfully produced micellar casein concentrate powder with protein content>80%and percentage of casein in true protein>90%in a pilot scale. Besides this, we also recycled theserum protein, lactose and water in serum, so the pilot scale production line for micellar caseinconcentrates powder is green, low carbon, circular and economical.