**Abstract**

Understanding the acid coagulation of milk is the core of producing different fermented dairy products. The formation of the gelled structure includes the decreased stability of casein micelles, aggregation, and the gradual development of the bonding between proteins during acidification and cold storage. The coagulation behavior of casein micelles and the physical properties of the final gels can be modified by processing techniques. Exopolysaccharides (EPS) produced by starter culture during fermentation also contribute significantly to the microstructure and texture of acid gels. This chapter discusses the mechanisms of acid-induced gelation of milk based on the modified nanocluster model of casein micelles. The recent findings of heating, high-pressure treatment, ultrasonication, and enzymatic modification on the acid gelation behavior of milk are described. The influence of different ingredients such as polysaccharides (endogenous and exogenous) and phenolic compounds on the physical properties of acid gels are also summarized.

**Keywords:** casein micelle, acid gelation, yogurt, Exopolysaccharride, whey proteins
