Foods like oranges, lemons, yogurt and apples have a sharp taste because they contain naturally occurring acids. Citrus fruits contain citric acid, apples contain malic acid and yogurts are rich in lactic acid. In this text-based activity, students summarise the functions and uses of citric acid as a food additive.
Foods containing flour must be baked before they can be eaten, to enable the starch in the flour to become digestible. Cakes and bread contain a raising agent that contains an acid and an alkali. These react to liberate carbon dioxide, which makes the baking flour rise.
Students investigate different combinations of raising agents in the baking of scones.
The reactions between acids and alkalis are important in the production of food.
Sherbert contains citric acid and sodium bicarbonate. These react to form the characteristic fizz of sherbert on the tongue.
Acids can be found in many drinks. Fruit juices and carbonated drinks are tested to find their pH.
Citric acid and sodium bicarbonate are dissolved in water to give two commonly used solutions in the food industry.
The pH of these solutions is measured and their reaction observed when mixed together.
The level of acid in a range of drinks is then measured. An extension activity is included