Detect the presence of synthetic food colours, Chemistry

Assignment Help:

Q. Detect the presence of synthetic food colours in the given samples?

Objectives

After conducting this activity, you will be able to:

• describe the kind of natural and synthetic colours used in the food industry,

• recognize the permissible limits of the synthetic food colours,

• isolate the synthetic colours in various food products, and

• identify these synthetic colours.

Principle

Synthetic colours form a major group of food colours which are classified into synthetic colour dyes and mineral pigments. These synthetic colours are futher divided into acidic and basic dyes. The isolation is carried out with the wool dyeing technique.

To identify them, you must study the colour reactions of these water soluble, acidic dyes which are characteristic to each colour and thus can be used as conformatory tests. The reactions of various colours with different chemical medium are given in Table earlier. Write down the reactions once again here in the format given:

Procedure

Carry out the activity following the procedure enumerated herewith:

1) Preparation of the Sample

Before carrying out the isolation of acidic colours, it is necessary to remove the interfering substances such as starches and fats, which hinder with the extraction procedures. The pre preparation of the sample for the extraction process would involve:

1) For Alcoholic drinks

Boil the alcoholic drinks to remove alcohol.

2) For the starchy products carry out the following steps:

Grind the starchy products like custard powders, cakes, pulses, candied fruits.

Treat 10 g of the ground sample with 50 ml of 2% NH3 in 70% ethanol.

Keep aside for one hour.

Centrifuge and take the liquid portion in a beaker.

Evaporate on the water bath.

Dilute the residue with 30 ml of dilute acetic acid.

3) For fatty food products like sausages, meats, fish pastes, processed nuts etc.

Defat the product with light petroleum in soxhlet apparatus.

Treat the defatted sample with 50 ml of 2% NH3 in 70% ethanol.

Keep aside for one hour.

Centrifuge and take the liquid portion in a beaker.

Evaporate on the water bath.

Dilute the residue with 30 ml of dilute acetic acid.

4) For the acidic products like fruit preserves and sauces

Solid samples are mixed with water and acidified with glacial acetic acid.

2) Dyeing of Wool

1) Immerse a 1m piece of pure white wool in the acidified solution of the sample.

2) Warm the solution till the wool gets dyed.

3) Take out the wool wash in water.

4) Put the dyed wool in 25 ml of 2% NH4OH and boil it.

5) Add NH4OH in excess till the colour gets extracted and comes in the solution.

6) Take 24 ml of this aqueous solution add 6 ml of 10% NaOH and 30 ml of solvent ether.

7) Take them in separating funnel, shake gently to mix all the layers.

8) Remove the aqueous fraction in another beaker.

9) To the ether layer add 5 ml of glacial acetic acid, if pink colour appears in the ether layer, it indicates the presence of rhodamine.

10) Take the aqueous layer from the 8th step, add 10 ml of glacial acetic acid and 30 ml of ether. Shake well.

11) Remove the aqueous layer in separate beaker and to the ether layer add excess of 10 ml of conc. NH4OH. If pink colour appears in the ether layer, it indicates the presence of Erythrosine.

12) Take 25 ml of the aqueous layer, add 10 ml of 20% NaCl shake and add 30 ml amyl alcohol. Add excess of conc. HCl so that the total volume becomes 60 ml.

13) Remove the aqueous layer and to this add 30 ml ether. Shake. Pink colour will appear in the water layer.


Related Discussions:- Detect the presence of synthetic food colours

What is threshold energy, The minimum amount of energy needed for the react...

The minimum amount of energy needed for the reaction to takes place is known as threshold energy.

The four quantum number for the valence shell electron, The four quantum nu...

The four quantum number for the valence shell electron or last electron of sodium (Z = 11) is: (1)  n =1, l= 1, m= -1, s= -1/2    (2) n =3, l=0, m=0, s= +1/2   (3) n =3,

Determine electron affinity, Q. How to Determine Electron Affinity? An...

Q. How to Determine Electron Affinity? Ans. Electron affinity is the measure of an atom's tendency to form a negative ion. Electron affinity can be measured by the amou

SOLID STATE, HOW UNIT CELL AND SPACE LATTICE ARE RELATED TO EACH OTHER?

HOW UNIT CELL AND SPACE LATTICE ARE RELATED TO EACH OTHER?

Metals, sodium does not react with a) Carbon b) Nitrogen c) Hydrogen d)b...

sodium does not react with a) Carbon b) Nitrogen c) Hydrogen d)both a an b

Benzoic acid, benzoic acid from benzene.i can''t see it clearly

benzoic acid from benzene.i can''t see it clearly

What is dielectric loss, What is Dielectric loss These losses occur ...

What is Dielectric loss These losses occur because of electrons hopping from one lattice site to another in transition metal oxides.

Copper, stuck on a chemistry assignment i need a way to include the elctron...

stuck on a chemistry assignment i need a way to include the elctron configuration and chemical properties of copper into a oral that is also a sales pitch.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd