Benedict Test Practicum - Biochemistry Courses - IPSE FPMIPA UPI Assignment

BIOCHEMISTRY

Benedict’ Test

Objective :

To identify the reducing sugars in sample through benedict’ test

Basic Theory:

Benedict’s test is a classification test that is used to identify reducing sugars, which include all monosaccharides and most disaccharides (excluding sucrose).  In contrast, all polysaccharides are nonreducing sugars.  Monosaccharides fluctuate between a ring open form and a ring closed form.  The ketone (-C=O) group, circled below for Fructose and the aldehyde group (-CHO), circled below for Glucose in the ring open forms can be reduced using Benedict’s test.  Some sugar units in disaccarides also fluctuate between a ring open form and a ring closed form.  These disaccharides are also reducing sugars because the ring open form has a ketone or aldehyde to react.  Sucrose is one of the few disaccharides that does not have a ring open form so it is a nonreducing sugar.  Benedict’s solution contains copper(II) sulfate (CuSO₄) dissolved in strong base.  The Cu²⁺ ions that are present in solution oxidize aldehyde and ketone groups.  In the process, the Cu²⁺ ions are reduced to Cu¹⁺ ions.  This is the origin of the title “reducing sugar.”  A positive Benedict’s test result is marked by the disappearance of the blue color due to Cu²⁺ ions and the appearance of a red precipitate consisting of reduced copper(I) oxide (Cu₂O). 

                                   

 

Materials and Equipments

Materials Benedict Solution Sample solution

Equipments Test Tube (6) Test Tube Rack Test Tube Holder Graduated cylinder 10 mL (1) Beakers 250 mL (1) Tripod with wire gauze Bunsen burner

 

Benedict’s Test procedure:

1. Add 1 mL of each sample to be tested into separate labeled test tubes.  In addition to your samples, test a blank sample (distilled water).
2. Add 2 mL of Benedict’s solution to each test tube and place the test tubes in a boiling water bath.
3. After about 2-3 minutes, remove the test tubes from the bath using a test tube clamp.  Record the appearance of each solution.  Note whether each result is positive or negative for the presence of reducing sugars.
4. Put your food products on display for the other groups.

 

Observation Table

No	Sample	Observation
		Before Heating	After Heating

 

Data Analysis

 

 

 

Conclusion

 

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