Mohammad Shirkhani - Department of Food Technology Faculty of Agriculture, Urmia University Urmia, Iran
Asghar Khosrowshahi Asl - Department of Food Technology Faculty of Agriculture, Urmia University Urmia, Iran
Ashkan Madadlou - Department of Food Technology Institute of Chemical Technologies, Iranian Research Organization for Science & Technology (IROST) Tehran, Iran

Acidified milk drinks are popular drinks diversely consumed in many countries. Lowering of pH to less than 4.2 can be performed by direct addition of acids or activity of lactic acid bacteria. Separation of serum, due to aggregation of milk proteins, is the main industrial defect in these types of beverages. Hydrocolloids are very commonly used to prevent serum separation in acidified milk drinks by increasing the viscosity, electrostatic or/and steric repulsion. Viscosity increase can also be achieved by employing of exopolysaccharides-producing starter cultures. Casein-wheyproteins ratio alteration, up to a certain level, is capable of stabilizing the system. However, homogenization pressure increase has no significant influence on the prevention of serum separation in acidified milk drinks.

acidified milk drinks; stability; milk proteins;hydrocolloids; exopolysaccharides