Chem food testing report.docx
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Transcript of Chem food testing report.docx
Results table
Food 1. Starch iodine test
2. Benedict´s test for reducing sugar
3. Biuret test for protein
4. Emulsion test for lipids
1.Egg white
2.Bread
3.Vegetable oil
4.Apple
5.Sweet
6.Milk
7.Sweet biscuit
8.Cheese
Luís Moreira
Chemical Food Testing
Aim
To identify if starch, sugar, protein and fat are present in 8 different types of food.
Introduction
Food tests enable you to find out what kind of food types a food contains.
FOOD TESTS:
FOOD TYPE TESTING REAGENT RESULT
STARCH Iodine solution+ = black
- = yellow/ brown
REDUCING SUGARe.g. glucose Benedict´s solution
+ = orange/ red
+/- = yellow/ green
- = blue
PROTEIN Biuret reagent+ = purple
- = blue
FATS Ethanol & water
+ = cloudy white
- = colourless
(+ = positive; +/- = slightly positive; - = negative)
Luís Moreira
2. Benedict´s test for reducing sugar e.g. glucose
Method
1. With a marker label 8 test tubes with numbers 1-82. Add 1 cm3 of food to each test tube3. Add 1 cm3 of distilled water 4. Add enough Benedict´s solution to cover the food & water.5. Place 4 test tubes in a beaker (x2) with water6. Place the beakers on a hot plate for about 3 minutes7.Observe the colour change and record your results on the results table – orange/red indicates presence of reducing sugar; yellow/ green concentration of reducing sugar low; blue no reducing sugar present
Diagram
Safety
HAZARD CONTROL MEASURES
Benedict´s solution Irritant Wear a lab coat & gogglesWash hands & skin if it spills
Burning Don´t touch hot plate & don´t put your head over it
Luís Moreira
Benedict´s solution
Hot plate
3. Biuret test for protein
Method
1. With a marker label 8 test tubes with numbers 1-82. Place 1 cm3 of food to each test tube3. Add 1 cm3 of distilled water4. Slowly, drip 1 cm3 of Biuret reagent5. Wait 3-5 minutes6. Observe the colour change and record your results on the results table – purple indicates presence of protein; blue no protein present
Diagram
Safety
HAZARD CONTROL MEASURES
Biuret solution Irritant Wear a lab coat & gogglesWash hands & skin if it spills
Luís Moreira
Biuret reagent
4. Emulsion test for lipids
Method
1. With a marker label 8 test tubes with numbers 1A-8A & other 8 test tubes with numbers 1B-8B2. Place 1 cm3 of food to each test tube labelled A3. Add 2 cm3 of ethanol4. Shake test tubes 1A-8A5. Pour 1 cm3 of liquid (not food) gently into test tubes labelled B 6. Add some distilled water & shake again7. Observe and record your results on the results table – cloudy white indicates presence of lipids; colourless no lipids present
Diagram
Test tubes B
Safety
HAZARD CONTROL MEASURESEthanol Flammable Irritant
Wear goggles
Luís Moreira
Ethanol
Distilled water
Test tubes A
Conclusion
Egg white - tested negative for starch, slightly positive for reducing sugar and positive for protein & lipids. Egg white has protein, lipids & a small amount of reducing sugar. It does not have starch.
Bread - tested negative for protein & lipids, slightly positive for reducing sugar and positive for starch. Bread has starch & a small amount of reducing sugar. It does not have protein & lipids.
Vegetable oil - tested negative for starch & protein, slightly positive for reducing sugar and positive for lipids. Vegetable oil has lipids & traces of reducing sugar. It does not have starch & protein.
Apple - tested negative for starch, protein & lipids and positive for reducing sugar. Apple has reducing sugar. It does not have starch, protein & lipids.
Sweet - tested negative for starch, protein & lipids and slightly positive for reducing sugar. Sweet has traces reducing sugar. It does not have starch, protein & lipids.
Milk - tested negative for starch, slightly positive for reducing sugar and positive for protein & lipids. Milk has protein, lipids & a small amount of reducing sugar. It does not have starch.
Sweet biscuit - tested negative for protein, slightly positive for reducing sugar & positive for starch & lipids. Sweet has starch, traces of reducing sugar & lipids. It does not have protein.
Cheese - tested negative for starch & for reducing sugar and positive for protein & lipids. Cheese has protein & lipids. It does not have starch & reducing sugar.
Luís Moreira
1. Starch iodine test
Method
1. Number 1-8 on a spotting tile2. Place a sample of each food in each spot3. Add 2 drops of iodine solution to each sample4. Observe the colour change and record the results on the results table – black indicates presence of starch; yellow/brown no starch present
Diagram
Luís Moreira
1 2 3 4
5 6 7 8
Iodine solution
Safety
HAZARD CONTROL MEASURES
Iodine solution Harmful
Wear a lab coat & gogglesWash hands & skin if it spills
Spotting tile