3.3 describe the tests for glucose and starch

Chemical test	Food	Procedure	Positive result
Iodine	Starch Found in: bread, pasta	Add a few drops of iodine to food This test works on solid food but for accuracy, crush solids in water.	Blue-black
Benedict’s	Glucose Found in naturally sweet foods Glucose is a reducing sugar; this food test involves reducing an alkaline solution of copper sulfate into copper oxide.	Add Benedict’s solution to food, put in water bath of around 70ºC. Solid foods should be crushed in water beforehand	Brick red
Biuret solution	Protein Found in: meat, fish, egg, milk Biuret solution potassium hydroxide + copper sulfate.	Add Biuret reagent to food Solid foods should be crushed in water beforehand	Light purple
Ethanol and water Emulsion	Lipids Found in oil, butter, margarine, avocado, salmon Fats are insoluble in water but dissolve in ethanol	Add ethanol to food, shake Then add water to food, shake For solid foods, filter after shaking.	Milky and cloudy

External links:

http://biology-igcse.weebly.com/-food-test-3---emulsion-ethanol-test-for-fats.html