The compositional and functional properties (i.e., solubility ,water-holding and fat-absorption capacity, electroconductivity and emulsification capacity, and stability) as well as digestibility by trypsin of buttermilk solids (BMS) and buttermilk protein preparations (i.e., buttermilk whey protein concentrates, BMWPC ; buttermilk casein-co-precipitate, BMCCP ; total buttermilk protein, TBMP and buttermilk acid casein, BMAC)  were studied. The effect of different pH levels on solubility, electroconductivity and emulsification capacity and stability was evaluated. All samples were similar in their chemical composition as they contained protein, lactose, fat and ash. BMS had higher fat, lactose and ash content and lower protein content compared with those of other dried buttermilk protein powders. Except electroconductivity and solubility, BMS showed limited functional properties in fat-absorption capacity (0.66 g fat/g protein) and emulsifying capacity (0.373-0.543, O.D) and stability (34-37 min.) at low pH (pH≤5) while , BMWPC had the highest fat-absorption capacity (2.5 g fat/g protein) and emulsifying capacity(0.400-0.800, O.D) and stability(38-44 min.) at the same pH , furthermore, its high digestibility by trypsin . This could be due to the heat treatment applied during preparation of BMWPC. So, BMWPC appears to be a promising and unique ingredient in the formulation of low pH foods.