Grade 5 | Science | Lab tests, Food and Clothing, Olympiad, CBSE, ICSE, SOF, ITO
Ethanol and water solution is used for observing the presence of fat. If a white emulsion is observed then it confirms the presence of fat.
Iodine test is used for confirming the presence of starch. If blue-black color is observed then starch is present.
Benedict's solution is used for confirming the presence of simple sugar. When sugar is added to Benedict's solution and boiled the solution turns from blue to orange.
Three are 2 types of sugars:
1) Simple - Includes monosaccharides like glucose and fructose and disaccharides like maltose, sucrose and lactose. Simple sugars are sweet and dissolves in water. They cannot be tested by iodine test.
2) Complex - Consists of polysaccharides like starch, glycogen, and dextrans. Starch does not dissolve well in water and is not sweet in taste. It contains amylose which is resposible for giving it black/blue color with iodine.
Amylase is a digestive enzyme present in the saliva of humans and other mammals which is used for digesting carbohydrates and turning them into simple sugar. Starch when left in amylase for some time breaks into sugar. Optimum temperature for amylase activity on starch is around body temperatue. As the temperature rises above body temperatue amylase reaction time with starch increases.
The Biuret Test is used testing the presence of protein. If we add 3-4 drops of solution containing protein the blue color liquid will change into pink or purple color.