SOP: Determination of Ash Content in Sugar by the Gravimetric Method

GIFSQ — Global Institute for Food Safety & Quality

Principle

The organic matter of the sugar sample is destroyed by charring and ashing in a muffle furnace at 550°C until an almost white ash remains. The ash is moistened, dried and re-ashed to obtain a constant weight; the increase in the weight of the tared dish is the ash content, expressed as per cent. (The ash content of refined sugar is very small, but it is estimated as a general indicator of the degree of refining.)

Apparatus required

• Tared dish
• Muffle furnace (550°C)
• Desiccator
• Water bath

Reagents

None.

Procedure

Ignite 5 g of sample in a tared dish on a low flame until the mass is thoroughly charred

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Heat in a muffle furnace at 550°C until an almost white ash is obtained

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Cool in a desiccator, moisten the ash with a few drops of water, and dry on a water bath

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Heat again in the muffle furnace, cool, and weigh

Calculation

Ash (%) = (weight of ash × 100) / (weight of sample taken)

Where,

• Weight of ash = final weight of dish and ash − tare weight of dish
• Weight of sample taken = 5 g

Precautions

• Char the sample thoroughly on the low flame before placing it in the muffle furnace.
• Cool in a desiccator before every weighing.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.