Tags : FSSAI

Method No.: FSSAI 03.011:2023

Scope

Ash refers to the inorganic residues remaining after either ignition or complete oxidation of organic matter. This is a routine reference method for determining the Total Ash content of cereals and cereal products. It is applicable to all food grains and products, including wheat, durum wheat, rice (paddy, husked, and milled rice), barley, millet, rye, oats, triticale, sorghum, and kaffir in the form of grains, milled grains, semolina or flour, biscuits, and other bakery ware. The method is also applicable to edible starches and starch products such as tapioca Sago (Saboodana) and palm sago starch.

Caution

• Use thermally insulated gloves, tongs, and protective eyewear when handling hot crucibles.
• Avoid touching crucibles/dishes with hands; use platinum-tipped tongs.
• Warm crucibles can create a vacuum in the desiccator on cooling. Remove the desiccator cover slowly to prevent a sudden inrush of air.
• Open and close the desiccator slowly to avoid glass breakage.

Principle

All organic matter is destroyed by incinerating the sample to a constant mass at a high temperature of 550 ± 25 °C in a muffle furnace.

Apparatus/Instruments

• Dish: Flat-bottomed, with a surface area of at least 15 cm², made of platinum, quartz, porcelain, or another material unaffected by the test conditions. Clean carefully without abrasive products.
• Muffle furnace: Capable of being regulated at 550 ± 25 °C.
• Desiccator: Containing orange indicating silica gel.
• Analytical balance: Accurate up to 0.0001 g.
• Special muffle furnace tongs: Stainless steel.
• Thermal protection gloves: Capable of resisting temperatures up to 550-600 °C.
• Bunsen/Electrical burner.
• Tripod stand: Iron.
• Wire gauze.

Method of Analysis

1. Use fresh samples rather than leftovers from moisture determination.
2. Weigh a previously clean and dried dish (W1).
3. Accurately weigh about 5 g of powdered sample into the dish.
4. Place the dish with its lid underneath in the oven at 130-133 °C for 2 hours.
5. Time should be reckoned from the moment the oven reaches 130 °C after placing the dishes.
6. Remove the dish after 2 hours, cool in the desiccator, and weigh (W2).
7. Ignite the dried material in the dish with a burner flame until charred. (This step must be carried out in a fume hood.)
8. Transfer to a muffle furnace at 550 ± 25 °C and continue ignition until grey ash is obtained.
9. Cool in a desiccator and weigh. Repeat heating, cooling, and weighing at 30-minute intervals until the difference in weight in two consecutive weighings is less than 1 mg.
10. Note the lowest weight (W2).
11. If ash still contains black particles, add 2-3 drops of pre-heated water at 60 °C. Break the ash, evaporate to dryness at 100-110 °C, and re-ash at 550 °C until ash is white or slightly grey.

Calculation and Units of Expression

Total ash on dry basis (% by weight) = (\frac{W2 - W}{W1 - W} \times 100)

Where:

• W = Mass in g of empty dish.
• W1 = Mass in g of the dish with the dried material (moisture-free) taken for test.
• W2 = Mass in g of the dish with the ash.

Calculate the mean of two determinations and express the result to one decimal place.

Reference

1. AACC (1995). “Ash – Basic method” in approved methods of the American Association of Cereal Chemists, 9th edition.
2. AOAC International (1995) “Ash of flour – direct method” in Official Methods of AOAC International, method 923.03.
3. ISO 2171:1993 Cereals and milled cereal products – Determination of total ash.