Explain food preservatives and antioxidants in food.

(N/A) $(i)$ Food preservatives: Food preservatives prevent spoilage of food due to microbial growth. The most commonly used preservatives include table salt,sugar,vegetable oils,and sodium benzoate,$C_6H_5COONa$.
Sodium benzoate is used in limited quantities and is metabolized in the body. Salts of sorbic acid and propanoic acid are also used as preservatives.
$(ii)$ Antioxidants: These are important and necessary food additives. These help in food preservation by retarding the action of oxygen on food. These are more reactive towards oxygen than the food material which they are protecting.
The two most familiar antioxidants are butylated hydroxy toluene $(BHT)$ and butylated hydroxy anisole $(BHA)$. The addition of $BHA$ to butter increases its shelf life from months to years.
Sometimes $BHT$ and $BHA$ along with citric acid are added to produce more effect. Sulphur dioxide and sulphite are useful antioxidants for wine and beer,sugar syrups,and cut,peeled,or dried fruits and vegetables.