Supplementary Textual Material in Chemistry for Class XII Supplied by CBSE
CBSE published some supplementary textual material earlier this year for Class XII Chemistry. In case if you have not downloaded them, please do it now. We have given below the abridged portion of the supplimentary study material.
The major portion is from
Unit 16: Chemistry in Everyday Life – ANTIOXIDANTS
Antioxidants are one of the important and necessary food additives. These compounds retard the action of oxygen on food thus reducing its speed of decomposition by oxidation. Hence they help in the preservation of food. These act as sacrificial materials, i.e. these are more reactive towards oxygen than are the materials they are protecting. They also reduce the rate of involvement of free radicals in the aging process.
Examples: The two most familiar antioxidants used are butylated hydroxy toluene (BHT) and butylated hydroxy anisole (BHA) (Figure 1). These phenolic compounds are added to preserve fats in packaged food. Oxygen reacts preferentially with BHA or BHT rather than oxidizing fats or oils, thereby protecting them from spoilage. The addition of BHA to butter increases its storage life from months to years. Sometimes, BHT and BHA are added in combination with citric or ascorbic acids to produce a more active synergetic
Sulphur dioxide and sulphites ( such as sodium sulphite, sodium bisulphite and sodium metabisulphite) are useful antioxidants for wine and beers, sugars syrups and cut, peeled or dried fruits and vegetables. They prevent or reduce their discoloration.
Questions from the section
1. Name one antioxidant commonly used to increase the storage life of butter.
2. Name one antioxidant used in wine and beers.