Objective: To compare the amount of reducing sugars and starch in yellow and green bananas.
Bananas are green in colour and taste flat but after they are harvested and stored for some days, they will turn yellow from green and become sweet.
The green banana tasted plain because it contained large amount of starch, while the yellow banana tasted sweet since it contained large amount of reducing sugars.
Benedict's test for reducing sugar:
Reducing sugars include all monosaccharides (glucose) and some disaccharides (maltose). Benedict's solution contains copper sulphates. Reducing sugars reduce copper(2) ions present in the blue copper sulphate solution to insoluble red brown precipitates.
The initial blue colour of the mixture turns green, then yellowish and may finally form a brick-red precipitates in the presence of reducing sugars. The amount of ppt gives a rough indication of the amount of reducing sugar present.
Iodine test for starch
Starch is slightly soluble in water in which it forms a colloidal solution.
A blue-black colour indicates the presence of starch due to the formation of complex.
In this experiment, the independent variable is the length of the starch period, hence keep the green banana in the freezer which assumes that storing bananas at the freezing temperature can stop the ripening process. Also keep the other green bananas
in a bell jar can let it become yellow.
The dependent variables are the amount if sugar and starch in the 2 banana samples. The amount of reducing sugars in the 2 samples can be compared by performing the Benedict's test and finding the amount of red ppt in each sample .
The amount of starch in the bananas can be compared by performing the iodine test and finding the intensity of dark blue colour in each sample .
After the experiment, I expect the yellow banana...