Acidic compositions comprising protein and fiber are described. In one embodiment, the compositions comprise: (a) a protein component comprising a protein selected from the group consisting of whey, casein, and mixtures thereof; and (b) from about 0.8% to about 5% of a fiber component, by weight of the composition;wherein the composition comprises particles having a median particle size of about 1 micron or less and wherein the pH of the composition is from about 3 to about 5.In another embodiment, the compositions comprise: (a) a protein component comprising a protein selected from the group consisting of whey, casein, and mixtures thereof; and (b) from about 0.05% to about 5% of a fiber component, by weight of the composition;wherein the composition comprises particles having a median particle size of greater than about 0.8 microns to about 1 micron and wherein the pH of the composition is from about 3 to about 5. In yet another embodiment, certain compositions may be prepared by the following process: (a) mixing the protein component and the fiber component to form a first mixture comprising the particles; and (b) mixing an acidic component and the first mixture at a temperature of from about 4 oC to about 43 oC to form a second mixture comprising the particles; wherein the particles have the median particle size of about 1 micron or less; and wherein the first mixture and second mixture are formed under high shear conditions.