Question

Explain how food items are spoiled by chemical reactions?

Answer 1

• Spoilage of food and vegetables:
  Food spoilage may be defined as any change that causes food unfit for human consumption. The chemical reactions catalyzed by the enzymes result in the degradation of food quality such as the development of bad taste and odour, deterioration, and loss of nutrients.
  Example 1: Rotten eggs develop a bad smell due to the formation of hydrogen sulphide gas.
  Example 2: Decaying of vegetables and fruits due to microbes.
• Rancidity of fishes and meat:
  Fishes and meat containing high levels of polyunsaturated fatty acids that undergo oxidation cause a bad odour when exposed to air or light. This process is called rancidity.
• Apples and fruits turn brown when cut:

1. Apples and some fruits turn brown due to a chemical reaction with oxygen in the air. This chemical reaction is called browning.
2. The cells of apples, fruits and other vegetables contain an enzyme called polyphenol oxidase or tyrosinase, when coming in contact with oxygen catalyses a biochemical reaction of plants, phenolic compounds to brown pigments known as melanins.