Question

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

Answer 1

Baking soda mainly consists of sodium bicarbonate which is an ionic salt of basic character. Its ability to neutralize small organic acidic groups and its tendency to act as a cleaning agent is one of the main reasons for its application in treatment of rancidity.

Complete Step By Step Answer:
Rancidification is the process by which food materials degrade and get spoiled over time which is exposed to the moisture and air present in the surroundings. Food items that contain oils and fats are most susceptible to rancidification.
The long organic fatty acid chains present in fats and oils get broken down by the action of microbes and other chemical substances in the atmosphere into shorted hydrocarbon chains containing carboxylic acid, aldehyde, ketones and alcohol functional groups.
The water and air from the surrounding is sufficient to hydrate and actively oxidize the fragments of fatty acid chains that produce molecules like lactic, pyruvic, propionic, isovaleric acids , acetaldehydes, and other smaller groups. These compounds are foul smelling in nature and not fit for consumption. Therefore the food tastes bad and has a distinct unpleasant odour.
Sodium bicarbonate also known as baking soda when spread across the surface has cleansing power and tendency to absorb the foul odours of the rancid food particles. Moreover the organic acids released by fatty acid decomposition and oxidation are neutralized by sodium bicarbonate which causes the smell to vanish.

Note:
The groups that have short chains and low molar mass are the ones with low boiling points that makes them highly volatile. The acidic group forms sodium salt after getting treated by baking soda and these salts are not volatile in nature, which is why the smell gets removed.