The present work has been carried out mainly to study some functional testing such as solubility and foaming properties in four types of acid caseins Buffalo, sheep, goat and camel at different pH value ranging between 2- 8. The obtained result revealed that high solubility for all types of acid casein was at pH 2 and pH 8 except in acid sheep casein was at pH 5. Also, foaming expansion value for all acid casein was high at pH 2 and pH8. The obtained results concluded that foaming properties increased with increasing the solubility of all types of acid casein.