1. UNIDAD 2 Feeding and nutrition ANTIOXIDANTS: LEMON JUICE Biology and Geology 3. Secondary Education

2. UNIDAD 3 The lemon: an antioxidant UNIT 2 Biology and Geology 3. Secondary Education Foods oxidise when certain substances in them react with oxygen and deteriorate, producing bad smells, rancid tastes, alterations in their colour and texture, etc. An experiment with apples and lemons For example, many fruit and vegetables discolour when they come into contact with the air. Anti-oxidants are substances which prevent oxidation. 1. Cut an apple in half.

3. UNIDAD 3 The lemon: an antioxidant UNIT 2 Biology and Geology 3. Secondary Education 2. Rub one of the halves of the apple with a lemon.

4. UNIDAD 3 The lemon: an antioxidant UNIT 2 Biology and Geology 3. Secondary Education 3. After a few hours, observe what has happened. The apple that was rubbed with lemon is not discoloured. The apple that was not rubbed with lemon has oxidised (turned a darker colour).

5. UNIDAD 3 The lemon: an antioxidant UNIT 2 Biology and Geology 3. Secondary Education Explanation When the apple is cut in half, substances are released which react with the oxygen in the air and produce brown pigments. Lemon juice contains vitamin C, which is an antioxidant, and prevents or slows down this reaction with oxygen.

6. UNIDAD 3 The lemon: an antioxidant UNIT 2 Biology and Geology 3. Secondary Education Conclusions The importance of taking care of foods to avoid deterioration caused by certain external agents. The need to use certain products in order to conserve them. With this experiment, we have demonstrated: