**1. Introduction**

 From the batting inserted in the manufacturing process of the cream of fresh milk and butter, it is possible to obtain a by-product derived from the aqueous phase, called buttermilk [1, 2]. Buttermilk is made up of fat globules which are surrounded by membranes called milk fat globule membranes (MFGMs). Such membranes avoid its coalescence and its enzymatic degradation [1, 3]. During agitation, the fat globules are disrupted releasing various components dispersed into the aqueous medium such as polar lipids and fragments of MFGMs, which are possessing high functional potential due to their nutritional and technological characteristics [1, 2]. Exact quantity of production of buttermilk is not assessed; however, the quantity of production of buttermilk can be predicted on the basis of production

of butter. Approximately 6.5–7.0% of total milk produced worldwide is used for the preparation of butter that yields high bulks of buttermilk as a by-product (around 3.2 million tons/annum) [4].

 MFGM is rich in polar and neutral lipids, phospho- and sphingolipids, as well as mono-, di-, and triglycerides, as well as cholesterol [1]. Due to their technological and biological properties, the search has been increased by methods that concentrate and isolate MFGM [1, 3].

The use of buttermilk is justified due to its high nutritional value and low cost of obtaining it [5]. Its disposal in wastewater is uneconomical because it results in high BOD value (biochemical oxygen demand) [6]. Moreover, the lack of opportunities by not using this by-product in other industrial segments forces the dairy producers to continually invest in new technology for an environmentally correct disposal for this waste such as bioremediation [7].

 On this front, the dairy industry is increasingly interested in using its byproducts in new applications. The application of buttermilk is facilitated by the application of techniques such as pasteurization, concentration, and spray drying. Considering these aspects, the objective of the work was to gather studies that present the technological and biological properties of buttermilk.
