Is milk acid or base?

Hint: pH is the measurement of the acidity or the basicity of the solution. If the pH is less than 7 the solution will be acidic, while the pH being greater than 7 the solution will be basic and when the pH is equal to 7, the solution will be neutral. Milk has a pH near 7.

Complete answer:
The pH scale ranges from 1 to 14 where 1 is the lowest which indicates the highest acidity while 14 is the highest which indicates the highest basicity of the solution.
Milk contains lactic acid which means the pH will be slightly acidic. The exact value of pH of milk depends on the processing of milk, duration of packaging and opening of the milk and also the milk produced by the cow.
Generally, at 295 K, the pH of milk ranges between 6.5 to 6.7. This pH may change over time. As we all know that the milk gets sour, this means that the pH of the milk will be lower i.e. acidic compared to the pH which the milk had in the first place. The reason behind this is a bacteria which converts the sugar lactose present in the milk into lactic acid.
The pH of the whole, evaporated milk will be lower i.e. acidic than the pH of the regular whole or the skimmed milk.
Hence milk is usually acidic.

Note:
Curdling of milk is a process in which the pH level of the milk decreases i.e. it becomes acidic, generally due to the addition of acids such as citric acid or vinegar. When this happens the molecules of the milk proteins such as casein attract each other and they form lumps or ‘curdles’ which actually float on the surface of the solution.