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Tests

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Benedict's Test (Test for Reducing Sugar)
Benedict's Solution is a chemical reagent named after an American chemist, Stanley Rossiter Benedict. Benedict's reagent is used as a test for the presence of reducing sugars. This includes all monosaccharides and the disaccharides , lactose and maltose.

Benedict's Solution
A solution of sodium citrate, sodium carbonate, and copper sulfate that changes from blue to yellow or red in the presence of reducing sugars, such as glucose.

Procedure
To test for the presence of monosaccharides and reducing disaccharide sugars in food, the food sample is dissolved in water, and a small amount of Benedict's reagent is added. During a water bath, which is usually 4-10 minutes, the solution should progress in the colors of blue (with no glucose present), green, yellow, orange, red, and then brick red or brown (with high glucose present).A color change would signify the presence of glucose.

Benedict's reagent can be used to test for the presence of glucose in urine. Glucose found to be present in urine is an indication of diabetes mellitus. Once a reducing sugar is detected in urine, further tests have to be undergone in order to ascertain which sugar is present. Only glucose is indicative of diabetes.

Biuret's Test (Test for Protein)
The biuret test is a chemical test used for detecting the presence of peptide bonds. In the presence of peptides, a copper(II) ion forms a violet-colored complex in an alkaline solution. Several variants on the test have been developed.

The Biuret reaction can be used to assay the concentration of proteins because (for most proteins) peptide bonds occur with approximately the same frequency per gram of material.

Biuret's Solution
The biuret reagent is made of potassium hydroxide (KOH) and hydrated copper (II) sulfate, together with potassium sodium tartrate. The reagent turns from blue to violet in the presence of proteins, blue to pink when combined with short-chain polypeptides.

Procedure
An aqueous sample is treated with an equal volume of 1 % strong base (sodium or potassium hydroxide most often) followed by a few drops of aqueous copper(II) sulfate. If the solution turns purple, protein is present.

Emulsion Test (Test for fats)
The emulsion test is a method to determine the presence of fats or oil.

Procedure
Add ethanol to test substance. Shake to dissolve. Dilute the liquid with water. The test tube will be warm if fats is present.

The solution
Organic compound, most important of the alcohols, chemical formula CH3CH2OH. Produced by fermentation, it is the intoxicating ingredient in alcoholic beverages.

Iodine Test (Test for starch)
Add a couple of drops to solution or food item. There is no need to heat. The result will be almost instantaneous. A colour change from orange to blu-black shows the presence of starch.

The solution
A nonmetallic element, symbol I, atomic number 53, relative atomic mass 126.9045, the heaviest of the naturally occurring halogens. Under normal conditions, iodine is a black, lustrous, volatile solid.

Tests

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