Maple syrup is dark in colour.
Natural pH indicators like turmeric or morning glories generally change in colour and indicate the pH of any solution
The pH change is due to high hydronium ion concentration of hydroxide ion concentration.
The pH change is indicated by change in colour by natural indicators which is possible to be observed if we have some light coloured sample / transparent sample to be tested.
In case of maple syrup the colour is so dark that it becomes difficult to observe the colour change in any natural indicator
