By Claire Knight

Aim of this prac The aim of this practical activity is to determine what effect changing acid and base levels has on taste.

Equipment required Icing sugar Bicarbonate of soda Citric Acid Jelly crystals 4 containers Measuring spoons

The recipes tested Recipe A (original recipe) 4 teaspoons of icing sugar ½ teaspoon of citric acid ½ teaspoon of jelly crystals ¼ teaspoon of bicarb of soda Recipe B (more citric acid) 4 teaspoons of icing sugar 1 teaspoon of citric acid ½ teaspoon of jelly crystals ¼ teaspoon of bicarb of soda Recipe C (more bicarb soda ) 4 teaspoons of icing sugar ½ teaspoon of citric acid ½ teaspoon of jelly crystals ½ teaspoon of bicarb of soda Recipe D (less icing sugar) 2 teaspoons of icing sugar ½ teaspoon of citric acid ½ teaspoon of jelly crystals ¼ teaspoon of bicarb of soda

Predict – Reasons for the recipes chosen It is predicted that the sherbet with more citric acid than the original recipe will produce a greater chemical reaction and taste better than the recipe with more bicarb soda and the last recipe that will have less icing sugar.

Method In each container, carefully measure the required ingredients. Mix well. To conduct taste test, use a small stick or spoon to place a small amount of the mixture into your mouth.

Observe - Results RecipeTaste Recipe A Quite sweet with a little fizz. Can taste a lemon type taste Recipe B A lot fizzer than the first one, same level of taste (lemon type). Really big after taste, more than Recipe A Recipe C A little fizz, tasted more powdery than the previous 2. Very little after taste. Tasted quite bitter. Recipe D Moderate fizz (much like Recipe A), not as sweet as the other recipes. Quite a powdery taste too. Seemed a little bitter, not as much as Recipe C though.

Acids & Bases The acids in this test were – the citric acid, food acid in the jelly crystals. The bases in this test were – the bicarbonate of soda. There was only a small amount of bicarb soda required because it has a much higher pH level in comparison to citric acid, which is a weak acid.

Explanation of results Prediction – that the sherbet with more citric acid (Recipe B) than the original recipe (Recipe A) will produce a greater chemical reaction and taste better than the recipe with more bicarb soda (Recipe C) and the last recipe that will have less icing sugar (Recipe D). From the results, Recipe B did produce a greater chemical reaction, as it was far more fizzier than Recipe C & D. This reaction can be explained by there being more citric acid in the mixture. It was more pleasant to eat than Recipes C & D, as C had more bicarb, which produces a more bitter tasting reaction and D had less sugar, which again meant a more bitter taste.

Further explanation To reproduce this test again, it would better if the tester didn’t know which each mixture was, creating a ‘blind test’. Also another recipe could be chosen when less jelly crystals were used, as the ingredients of jelly crystals include cane sugar and food acids. The test would be more fair if more testers were involved, as would allow for more comparison of results.