LAUSR

The fractionation of serum protein (SP) and micellar casein (CN) from skim milk can be accomplished using microfiltration (MF). The objective of this study was to determine the removal of total SP using a 0.05‐μm ceramic membrane at each stage of production, as well as the composition of retentates and permeates for a three‐stage, 3×, discontinuous bleed‐and‐feed process. The average flux of ceramic membrane obtained from our results was 96.25 kg/m² per hour. The cumulative removal rate of actual SP is 96.2% at Stages 1, 2, and 3 (58.1%, 25.0%, and 13.0%, respectively), closely related to the theoretical value of 96%. In addition, the rate of removal of lactose, ash, calcium, and phosphorus were 86.44%, 82.68%, 34.9%, and 55.0%, respectively. The water flux of the membrane reduced by 55.57% after MF, while membrane flux recovered to 99.21% after cleaning with 2% (w/v) sodium hydroxide and 1% (v/v) nitric acid solution. Moreover, permeates and retentates were concentrated by vacuum and spray drier in order to obtain serum and micelle CN powder having protein contents of 10.19% and 75.57%, respectively. PRACTICAL APPLICATIONS: This article proposes high‐efficiency fractionation of macromolecules and small molecules by membrane technology using skim milk as raw material. Permeate was used to produce high‐quality SP products, which was essentially sterile and fat‐free, and had better solubility, foaming, and gelation than cheese whey protein. And retentates can be directly used for micelle CN powder or cheese production. The composition of the cheese produced was similar to that of traditional cheese. It improves the quality of the products and reduces environmental pollution. In addition, the study also provided a theoretical and applied basis for the membrane separation process of goat milk and the research and development of functional goat milk‐based ingredient.