Saturday, March 03, 2007

Food Tests: Chapter 5 - Nutrition

Hmm... I'm not sure what I wanted to revise today, so I'll just pick Food Tests!
So it will be rolled out in the following format:

Name of test:
Test for ...?:
Reagent(s):
Procedures:

~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~

Name of test: Benedict's test
Test for ...?: Reducing sugar
Reagent: Benedict's solution [Copper (II) Sulphate]
Procedures:

1. Solution of 2cm3 Benedict's solution in test tube.
2. Shake mixture and immerse in boiling water.
3. Observe colours:
red precipitate - highest amount of reducing sugar present
orange precipitate
yellow precipitate
green precipitate
blue percipitate - lowest/no amount reducing sugar present

~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~

Name of test: Ethanol emmersion test
Test for ...?: Fats (liquid)
Reagent: ethanol
Procedures:
1. 2cm3 of ethanol in test tube
2. Shake mixture
3. add 2cm3 of distilled water
Results:
- Heat felt
- mixture becomes white/milky/cloudy
= fats PRESENT
- No heat felt
- mixture stays translucent
= fats ABSENT

~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~

Name of test: Oil spot test
Test for ...?: Fats (solid)
Reagent: rien (French: nothing)
Procedures:
1. wrap food in filter paper
2. crush by pestle
Results
- If it leaves a translucent spot on filter paper
= fats PRESENT
- If leaves no translucent spot
= fats ABSENT

~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~


Name of test: Biuret test
Test for ...?: Proteins
Reagents:
- sodium hydroxide
- 1% copper (II) sulphate
Procedures:
1. add 1cm3 sodium hydroxide
2. shake THROUGHLY
3. add 1% copper (II) sulphate
DROP BY DROP
SHAKING AFTER EACH DROP
Results:
Violet = highest amount of proteins
Blue = low/no proteins present

~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~

Name of test: Iodine test
Test for ...?: Starch
Reagents: iodine solution (duh.. obviously =p)
1. Drop drops of iodine sol. on food
dark blue = starch present
yellowish-brown = starch absent

12 Comments:

At 3:08 AM, Anonymous Anonymous said...

why do you get the results that you get? what reacts with what to bring about those results?

 
At 5:56 PM, Anonymous Anonymous said...

y does the ethanol become cloudy when it comes into contact with lipids?


-A very interested student.

 
At 6:06 PM, Blogger drewboy said...

why is heat felt in the ethanol immersion test if lipids are present?

 
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