Question

Acetic acid is present in vinegar. Curd contains________.
A. Lactic acid
B. Tartaric acid
C. Picric acid
D. None of the above

Answer 1

Hint: We know that curd can be produced from milk by coagulation of milk by the process named as curdling.

Complete answer:
The coagulation of milk can be done by adding edible acidic substances such as vinegar or lemon juice. The increase of acidity of milk causes the formation of solid masses of milk, that is, curd. Curd contains lactic acid in it.

So, the correct option is A, that is, lactic acid.

Additional Information:
A white, crystalline organic solid which is found in many fruits, such as grapes, bananas, citrus, tamarind etc. is termed as tartaric acid. The salt of tartaric acid, that is, potassium bitartrate develops naturally in the fermentation process. Tartaric acid is used in beverages, jams, jellies, baking powders etc. The chemical formula for tartaric acid is ${{\rm{C}}_{\rm{4}}}{{\rm{H}}_{\rm{6}}}{{\rm{O}}_{\rm{6}}}$.
> An organic compound which chemical formula is ${\left( {{{\rm{O}}_{\rm{2}}}{\rm{N}}} \right)_3}{{\rm{C}}_{\rm{6}}}{{\rm{H}}_{\rm{2}}}{\rm{OH}}$ is picric acid and its IUPAC name is 2,4,6-trinitrophenol. The ‘picric’ word in Greek means bitter taste. Picric acid can be produced by reacting phenol with concentrated nitric acid in the presence of concentrated sulphuric acid. Picric acid is very hazardous in case of eye and skin contact. Eye contact of picric acid results blindness. Skin contact of picric acid results in inflammation and blistering.

Note: The formula of lactic acid is ${{\rm{C}}_{\rm{3}}}{{\rm{H}}_{\rm{6}}}{{\rm{O}}_{\rm{3}}}$. Curd can be made by first boiling the milk and then cooling it to thirty to forty degree Celsius and then adding a spoon of curd. The lactobacillus in the curd multiplies itself in the temperature range of $30^\circ {\rm{C}} - 40^\circ {\rm{C}}$ and produces curd.