GIFSQ Tools · Module 1 — Food Composition & Proximate Analysis · Tool 3 of 500
Ash is the mineral residue left after burning off all the organic matter. Weigh the crucible empty, with the sample, and with the ash — or enter the sample and ash weights directly.
Try sample values — fills the form with the worked example below.
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Total ash (%)
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Sample weight (g)
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Ash weight (g)
Equation: Total ash % = mash ÷ msample × 100
From crucible weights: msample = (crucible + sample) − empty crucible; mash = (crucible + ash) − empty crucible.
Method: Dry ashing at 550 °C to constant weight, AOAC 923.03 (ash of flour) / AOAC 942.05 (ash in animal feed).
Assumptions: all organic matter is burned off; the residue is mineral matter; the crucible is at constant weight before and after ashing.
Limitations: some minerals volatilise at 550 °C (notably chlorides and some potassium salts), so ash slightly understates total minerals; a sample that spatters or foams loses material and understates ash; ash does not say which minerals are present.
Rounding: results to 2 decimal places; intermediate values are not rounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
From crucible weights: msample = (crucible + sample) − empty crucible; mash = (crucible + ash) − empty crucible.
Method: Dry ashing at 550 °C to constant weight, AOAC 923.03 (ash of flour) / AOAC 942.05 (ash in animal feed).
Assumptions: all organic matter is burned off; the residue is mineral matter; the crucible is at constant weight before and after ashing.
Limitations: some minerals volatilise at 550 °C (notably chlorides and some potassium salts), so ash slightly understates total minerals; a sample that spatters or foams loses material and understates ash; ash does not say which minerals are present.
Rounding: results to 2 decimal places; intermediate values are not rounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: empty crucible 25.000 g, crucible + sample 30.000 g, crucible + ash 25.075 g. Sample = 30.000 − 25.000 = 5.000 g; ash = 25.075 − 25.000 = 0.075 g; total ash = 0.075 ÷ 5.000 × 100 = 1.50 %.
Enter values above to see results.
Typical ash: white flour 0.4–0.6 %, whole wheat flour 1.4–1.7 %, milk powder 5–6 %, meat 1–1.5 %. Ash is a quick check for flour extraction rate and for added mineral matter. Tool 3 of 500 — GIFSQ
