Research recipes for pie fillings which include starch as a thickening agent (try cherry pie filling, apple pie filling and lemon meringue pies from a variety of sources.)

Study the recipes carefully - when is the sugar (and lemon juice in the case of lemon meringue pie) added? Why is this?

Do the recipes vary in terms of when the sugar and lemon juice is added?

What happens to the stability of the gel if you increase the sugar or lemon juice?

Do you think some recipes will have more reliable outcomes to others?