Title: Food Testing Lab Paper 3 practice

Purpose:

to determine the presence/absence of carbohydrates, lipids, and proteins in food.

to understand the relevance of food testing to diet and health issues

Materials:

Iodine-Potassium Iodine solution (starch test)
Benedict’s solution (monosaccharide test)

Biuret solution (protein test)

Brown paper (lipid test)

Alcohol (lipids test)

Hydrochloric acid (breakdown reducing sugars)

Bunsen burners

5 test tubes in a test tube rack

Test tube holders

Plastic trays / tiles

Procedure: Using small quantities of food, test for the presence of proteins, lipids, carbohydrates (starch and reducing sugars).

Starch Test

Test tubes
Test tube racks Test tube holders Hot plate pipettes

Put 1 dropper of sample into a test tube or onto a tray.
Add 2—3 drops iodine/potassium solution.
A blue-black color indicates the presence of starch.

Reducing Sugar Test

Put 1 dropper of Benedict’s solution into a test tube.
Add 5—10 drops of sample or a small piece if solid.
Hold the test tube (with a test tube holder) in a bunsen flame carefully for one minute. A brown-orange color - red indicates the presence of a monosaccharide (glucose or fructose).

Protein Test

Put 1 dropper of food sample in a test tube or a small piece. Add 5—10 drops Biuret solution
A purple color indicates the presence of protein.

Lipid Test

Simple version:

Pick up a slip of brown paper and try to see through it.
Place 1—2 drops of food sample (or rub a piece onto the paper) onto the brown paper.
Now pick it up and try to see it.
Translucence (ability to partially see through the paper) indicates the presence of fat.

Lipid test 2: Emulsification test.

Take a small piece of sample and add it to a test tube

Add 5 drops of ethanol

Add 5 drops of water

A cloudy appearance indicates the presence of fats

1.  Perform the “control” tests (above) and then test various food samples for the presence of starch, sugar, protein, and lipids.

2.  Record your results in a data table similar to the one below.

Results:

Describe the appearance of each sample after the test.

Sample / Starch test / Protein test / Lipid test1 / Lipid test2 / Sugar test1 / Sugar test2

Questions:

1.)  Summarise your findings, using the qualitative terms (such as a high, medium and low amounts) about the contents of the 3 samples you investigated (6)

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2) According to your knowledge of health issues, can you identify any health risks associated with the consumption of any food item, based on your findings (4)

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3) BMI (Body mass index is calculated as mass in kilograms divided by height in M, squared). State the body mass index of a man who has a mass of 75 kilogram and a height of 145cm. (1)

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4) A woman has a height of 150cm and a BMI of 40. Calculate the minimum amount of body mass she must lose to reach normal body mass status. Show all your working.

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