Question

testing of food items for carbohydrates, proteins,fats
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Answer 1

Answer:

Hi This might help you...

Explanation:

Carbohydrates provides energy to cells in the body. Protein is the major functional and structural component of all the cells of the body. Fats and oils are the highest energy sources contain fatty acids which is essential for health which is not produced by the human body.

Aim:

To detect the presence of carbohydrates, fats and proteins in the given food stuffs.

Theory:

The presence of carbohydrates, fats and proteins in any food stuff is detected by performing the tests for proteins, fats and carbohydrates with the extract of the foodstuff. The advantage is these tests do not interfere with each other.

Test for Carbohydrates:

Molisch’s test – Given sample food + Molisch’s reagent → Purple or violet ring confirms the presence of carbohydrate.

Fehling’s test – Given sample food + Fehling’s reagent → Red precipitate confirms the presence of carbohydrates

Benedict’s test – Given sample food + Benedict’s reagent → Red precipitate confirms the presence of carbohydrates.

Tollen’s test – Given sample food + Tollen’s reagent → Silver mirror confirms the presence of carbohydrates.

Iodine test – Given sample food + Iodine solution → Blue colour solution confirms the presence of starch.

Test for Proteins:

Biuret test – Given sample food + Aqueous copper sulfate → Violet colouration confirms the presence of Proteins

Xanthoproteic test – Given sample food + Nitric acid → Yellow colour solution confirms the presence of proteins.

Millions test – Given sample food + Mercuric sulfate in the presence of sodium nitrite and sulfuric acid → Brick red colour solution confirms the presence of proteins.

Ninhydrin test – Given sample food + Pyridine solution of ninhydrin → Violet colour solution confirms the presence of proteins.

Test for Oils and Fats:

Solubility test – Given sample food + Chloroform or alcohol → Miscible with chloroform and immiscible with water the fat presence is confirmed.

Translucent spot test – Given sample food + rubbed between the folds of filter paper → presence of translucent spot then the presence of fats is confirmed.

Acrolein test – Given sample food + Potassium bisulfite KHSO4 → Pungent irritating odor then the presence of fats or oil is confirmed.

Materials Required:

Molisch’s reagent

Fehling’s reagent

Benedict’s reagent

Tollen’s reagent

Iodine solution

Copper sulfate solution

Sodium hydroxide

Nitric acid

Mercuric sulfate

Sodium nitrite

Alcohol

Chloroform

Filter paper

Potassium bisulfate

Concentrated hydrochloric acid

Furfural solution

Test tubes

Test tube holder

Water bath

Dropper

Stirrer

Bunsen burner

Apparatus Setup:



Procedure:

To test the presence of carbohydrates, proteins, fats and oils in the given food sample, first the extract of the given foodstuff should be prepared. Dry the given foodstuff in the mortar with a pestle or by boiling with minimum quantity of water extracting with a small quantity of an organic solvent after grinding the foodstuff.

Some of the examples of preparing extract of food stuff is given below.

For potatoes – cut to slices and boil with water.

For butter – test directly

For grapes – Extract the juice.

For boiled egg – take the white portion grind and shake with water.

Answer 2

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Testing of food items for carbohydrates, proteins,fats

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Biuret test – Given sample food + Aqueous copper sulfate → Violet colouration confirms the presence of Proteins. Xanthoproteic test – Given sample food + Nitric acid → Yellow colour solution confirms the presence of proteins.

$\huge\tt\colorbox{pink}{Test for Carbohydrates}$

Take a small quantity of food to be tested on a porcelain tile. Dilute it with 2 drops of water. Put 2-3 drops of iodine solution on it. You will observe the color of the food item into blue-black that indicates the presence of starch in the food.

$\huge\tt\colorbox{aqua}{Test for Protein}$

A total protein test measures the amount of protein present in the blood serum or urine. A total protein test can detect normal or abnormal protein levels, which can help diagnose medical conditions, such as kidney and liver diseases.

$\huge\tt\colorbox{yellow}{Test for fat}$

Reagent Ethanol

Method Add ethanol to the food to dissolve the fat then add water.

Initial colour Colourless

Colour of positive result White emulsion

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