How to Analyse ASH CONTENT

 ASH CONTENT

Ash content of a food sample provides the information about the amount of indigestible components of the product.

Aim: To determine the percentage ash content of a food sample

Precaution: 

v  Standard reagents must be used

 

PRINCIPLE: The organic contents of food are burnt off in air during the ashing period. The residue ash, which consists of the inorganic components are in the form of oxides and chlorides. These inorganic components are minerals and other indigestible substances.

APPARATUS: Crucible, analytical balance, spatula, hot-plate, fume cupboard, pair of tongs and carbolite furnace.

PROCEDURE

1.       A Crucible is cleaned, dried in an Oven, cooled in a desiccator and weighed (W1).

2.       Weigh 2-5g of the sample into the Crucible (W2), using a spatula.

3.       The setup is charred on a hot plate in a fume cupboard until no more smoke is given off. It is then transferred, using a pair of tongs into the Carbolite furnace at 500⁰C until it fully ashes (for 7-8hrs).

4.       It is removed and cooled in a desiccator and weighed (W3)

NOTE: If the ashing process is incomplete after 7-8 hours, evident by black particles present in the ash, the ash is removed from the furnace, cooled in a desiccator, moistened with some drops of 1% Nitric acid, dried in a water bath or in an oven, and then returned to the furnace until fully ashes. 

 

 

Calculation: 

Percentage Ash content =       (W3-W2)    ×   100 %

                                                (W2-W1)

LIMITS: 6% maximum for Cream powdered milk, 5.5% for cheese (cheddar, gouda), 1% for wheat and semolina, 2% for biscuits, 1.5% for garri, 0.8% for custard, 0.8% for rice, 1% for honey.