What is rancidification? How does baking soda stop the smells of rancidification?

1 Answer
Sep 12, 2014

Rancidification of the oils in sweat produces smelly fatty acids. Baking soda reacts with these acids.


Rancidification is the conversion of fats and oils into smaller, volatile compounds with bad tastes and odours. It occurs in three ways.

  • Hydrolysis

The oils in sweat react with water to form free fatty acids. The short-chain acids have strong smells.

  • Oxidation

Unsaturated fatty acids react with oxygen to form volatile, smelly aldehydes and ketones.

  • Microbial Action

Microbes such as bacteria use their enzymes to break down fat into strong-smelling acids. These include lactic, pyruvic, propionic, and isovaleric acids.


Baking soda is a base. The powder has a large surface area. It adsorbs the acidic vapours and reacts with them to form salts.

RCOOH + NaHCO₃ → RCOO⁻Na⁺ + H₂O + CO₂

The ionic salts have low vapour pressures, so they have no smell.