Sonzaschool

Mada za sehemu hiiNutritionMada 12

Food test is used to determine which nutrients are present in a food specimen. At this level we will learn how to test for carbohydrates, proteins and lipids.

Test Procedure Observation Conclusion Test for reducing sugar Dissolve specimen in water. Add an equal amount of Benedict's solution to the solution. Boil the mixture. Colour changes from blue to green to yellow then orange Reducing sugar is present Test for non-reducing sugar Dissolve the specimen in water. Put 2 cm³ of the solution in a test tube. Add 1 cm³ of dilute hydrochloric acid (neutralizes disaccharides to monosaccharides). Boil the mixture. Allow the mixture to cool. Add small amounts of sodium hydroxide at a time. Continue until fizzing stops. Add 2 cm³ of Benedict's solution, then boil the mixture. Colour changes from blue to green to yellow to orange Non-reducing sugar is present Test for starch Add a few drops of iodine solution to the food specimen. Colour changes to blue-black Starch is present

Test	Procedure	Observation	Conclusion
Test for reducing sugar	Dissolve specimen in water. Add an equal amount of Benedict's solution to the solution. Boil the mixture.	Colour changes from blue to green to yellow then orange	Reducing sugar is present
Test for non-reducing sugar	Dissolve the specimen in water. Put 2 cm³ of the solution in a test tube. Add 1 cm³ of dilute hydrochloric acid (neutralizes disaccharides to monosaccharides). Boil the mixture. Allow the mixture to cool. Add small amounts of sodium hydroxide at a time. Continue until fizzing stops. Add 2 cm³ of Benedict's solution, then boil the mixture.	Colour changes from blue to green to yellow to orange	Non-reducing sugar is present
Test for starch	Add a few drops of iodine solution to the food specimen.	Colour changes to blue-black	Starch is present

Procedure Observation Conclusion Biuret test : The specimen should be in solution form. Pour 2 cm³ of specimen in a test tube. Add 1 cm³ of sodium hydroxide solution then a drop of copper sulphate solution, shaking the mixture after each addition. Colour changes to purple Proteins are present

Procedure	Observation	Conclusion
Biuret test: The specimen should be in solution form. Pour 2 cm³ of specimen in a test tube. Add 1 cm³ of sodium hydroxide solution then a drop of copper sulphate solution, shaking the mixture after each addition.	Colour changes to purple	Proteins are present

Test Procedure Observation Conclusion Grease spot test Rub the specimen on a piece of dry filter paper. Hold the paper against the light. A translucent mark is formed Specimen contains lipids Sudan III test The specimen should be in solution form. Add a few drops of Sudan III solution. Droplets of oil turn red Specimen contains lipids Emulsion test Ensure the specimen is in solution form. Put the specimen in a test tube along with an equal amount of acetone, benzene or ethyl alcohol. Shake the mixture. Add an equal volume of water. The clear mixture turns cloudy, forming a milky suspension Specimen contains lipids

Test	Procedure	Observation	Conclusion
Grease spot test	Rub the specimen on a piece of dry filter paper. Hold the paper against the light.	A translucent mark is formed	Specimen contains lipids
Sudan III test	The specimen should be in solution form. Add a few drops of Sudan III solution.	Droplets of oil turn red	Specimen contains lipids
Emulsion test	Ensure the specimen is in solution form. Put the specimen in a test tube along with an equal amount of acetone, benzene or ethyl alcohol. Shake the mixture. Add an equal volume of water.	The clear mixture turns cloudy, forming a milky suspension	Specimen contains lipids

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