Abstract:Buttermilk is a by-product generated during butter production and is rich in high-value functional components, including milk fat globule membrane (MFGM), casein micelles, whey proteins, and phospholipids, giving it considerable potential for nutritional and food-processing applications. This review focuses on the basic composition and physicochemical properties of buttermilk, as well as technologies for the fractionation and separation of its functional components. The applicability of membrane separation, enzymatic methods, supercritical carbon dioxide extraction, and adsorption-based separation is compared, and recent advances in the application of buttermilk in emulsion systems, dairy products, bakery and flour-based products, fermented dairy products, and dairy beverages are further summarized. Finally, future research should strengthen the standardized characterization of buttermilk raw materials, establish whole-process mass balances that comprehensively account for target-component purity, cumulative recovery, membrane flux, energy consumption, cleaning burden, and utilization of side streams, and promote coordinated optimization between separation technologies and end-use food applications, thereby facilitating the large-scale and high-value utilization of buttermilk.