Biochemical Tests
Specific Objective:
Carry out test for reducing sugar, non reducing sugar, starch , protein and lipid. BIOCHEMICAL TESTS
Reducing and non-Reducing Sugars
Sugars can be classified as either reducing or non-reducing based on their ability to reduce copper(II) ions to copper (I) ions during the Benedict's Test. Reducing sugar have contain free aldehyde or ketone group and have the ability to reduce copper(II) ions to copper (I) ions during the Benedict's Test. All monosaccharides are reducing sugars while only some dissacharides are reducing sugar.
Examples of reducing sugar are:
Monosaccharides
Glucose
Fructose
Galactose
Dissacharides
Lactose
maltose
Non-reducing sugars do not contain have free aldehyde groups and upon testing with Benedict’s solution will not reduce copper(11) ions to copper (1) ions.
Non-reducing sugars do not react with any of the reducing-sugar test solutions. However, a non-reducing sugar can be hydrolysed using dilute hydrochloric acid. After hydrolysis and neutralization of the acid, the product may be a reducing sugar that gives normal reactions with the test solutions (Benedict’s solution /Fehling solution). Sucrose is the most common disaccharide non-reducing sugar.
TEST FOR REDUCING SUGAR
Procedure
1. A liquid food sample does not need prior preparation except dilution if viscous or concentrated. For a solid sample prepare a test solution by crushing the food and adding a moderate amount of distilled water. Decant the suspension to remove large particles. Use the decanted liquid as the test solution.
1. Add 2 cm3 of the sample solution to a test tube.
1. Add an equal volume of Benedict's solution to the test tube and swirl or vortex the mixture.
2. Leave the test tube in a boiling water bath for about 5 minutes, or until the colour of the mixture does not change.
3. Observe the colour changes during that time as well as the final colour.
4. To prepare a control, repeat steps 3-5 using 2 cm3 of
Carry out test for reducing sugar, non reducing sugar, starch , protein and lipid. BIOCHEMICAL TESTS
Reducing and non-Reducing Sugars
Sugars can be classified as either reducing or non-reducing based on their ability to reduce copper(II) ions to copper (I) ions during the Benedict's Test. Reducing sugar have contain free aldehyde or ketone group and have the ability to reduce copper(II) ions to copper (I) ions during the Benedict's Test. All monosaccharides are reducing sugars while only some dissacharides are reducing sugar.
Examples of reducing sugar are:
Monosaccharides
Glucose
Fructose
Galactose
Dissacharides
Lactose
maltose
Non-reducing sugars do not contain have free aldehyde groups and upon testing with Benedict’s solution will not reduce copper(11) ions to copper (1) ions.
Non-reducing sugars do not react with any of the reducing-sugar test solutions. However, a non-reducing sugar can be hydrolysed using dilute hydrochloric acid. After hydrolysis and neutralization of the acid, the product may be a reducing sugar that gives normal reactions with the test solutions (Benedict’s solution /Fehling solution). Sucrose is the most common disaccharide non-reducing sugar.
TEST FOR REDUCING SUGAR
Procedure
1. A liquid food sample does not need prior preparation except dilution if viscous or concentrated. For a solid sample prepare a test solution by crushing the food and adding a moderate amount of distilled water. Decant the suspension to remove large particles. Use the decanted liquid as the test solution.
1. Add 2 cm3 of the sample solution to a test tube.
1. Add an equal volume of Benedict's solution to the test tube and swirl or vortex the mixture.
2. Leave the test tube in a boiling water bath for about 5 minutes, or until the colour of the mixture does not change.
3. Observe the colour changes during that time as well as the final colour.
4. To prepare a control, repeat steps 3-5 using 2 cm3 of