SOP: Determination of Acid Insoluble Ash — Spices
GIFSQ — Global Institute for Food Safety & Quality
1. Principle
The acid insoluble ash is a measure of sand and other siliceous matter present in the sample. When ash is dissolved in dilute acid, inorganic compounds dissolved in acid, leaving silica and sand as acid insoluble ash.
2. Application
This method is applicable to determine acid insoluble ash in spices and also in other food products.
3. Apparatus
- Desiccator
- Silica crucible
- Oven
- Funnel and beakers
- Ashless filter paper (No. 41)
- Muffle furnace
4. Reagent
Hydrochloric acid solution — dilute 1 volume concentrated HCl with 2.5 volumes of distilled water.
5. Procedure
Add 25 mL of 1:2.5 HCl solution to the total ash containing crucible
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Boil for five minutes (placing inside fume hood)
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Filter through an ashless filter paper (No. 41)
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Wash with hot distilled water till acid free
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Transfer the filter paper with its content to the original crucible and ash in the muffle (550 ± 25°C) for 1 hour
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If carbon persists, add 3 or 4 drops of water and re-ash till carbon free
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Cool and weigh
6. Calculation
Acid insoluble ash % = [Wt. of acid insoluble ash ÷ Wt. of sample taken] × 100
References
AOAC 21st edn. 2019, Official Method 941.12(b), Ash of Spices; IS Specification No. IS 1797–1985, Methods of Test for Spices and Condiments.