GIFSQ Tools · Module 2 — Food Chemistry & Physicochemical Testing · Tool 22 of 500
Titrate a food sample with standard sodium hydroxide and get the titratable acidity as the named acid, in percent. AOAC 942.15.
Try sample values — fills the form with the worked example below.
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Titratable acidity (%)
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Net titration (mL)
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Reported as
Equation: Titratable acidity % = (V − Vblank) × N × meq × 100 ÷ m, where V is the titration volume in mL, N the NaOH normality, meq the milliequivalent weight of the named acid in g, and m the sample weight in g.
Method: AOAC 942.15 (acidity of fruit products) — titration with standard NaOH to the phenolphthalein end point (pH 8.1). Milliequivalent weights: citric 0.064, malic 0.067, tartaric 0.075, lactic 0.090, acetic 0.060 g per meq.
Assumptions: the named acid is the main acid in the sample; the NaOH is standardised; the end point is pH 8.1.
Limitations: a food contains a mix of acids, so the result is "as citric acid" (or the acid named) and not a true total of each acid. Dark or cloudy samples hide the colour end point — titrate to pH 8.1 with a pH meter instead.
Rounding: acidity to 2 decimal places; net titration to 2 decimal places.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: AOAC 942.15 (acidity of fruit products) — titration with standard NaOH to the phenolphthalein end point (pH 8.1). Milliequivalent weights: citric 0.064, malic 0.067, tartaric 0.075, lactic 0.090, acetic 0.060 g per meq.
Assumptions: the named acid is the main acid in the sample; the NaOH is standardised; the end point is pH 8.1.
Limitations: a food contains a mix of acids, so the result is "as citric acid" (or the acid named) and not a true total of each acid. Dark or cloudy samples hide the colour end point — titrate to pH 8.1 with a pH meter instead.
Rounding: acidity to 2 decimal places; net titration to 2 decimal places.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: 10.00 g orange juice titrated with 8.50 mL of 0.1 N NaOH, blank 0.00 mL, reported as citric acid. Acidity = 8.50 × 0.1 × 0.064 × 100 ÷ 10.00 = 0.54 % as citric acid.
Enter values above to see results.
Typical titratable acidity: orange juice 0.7–1.2 % as citric, apple juice 0.3–0.8 % as malic, grape juice 0.6–1.0 % as tartaric, yogurt 0.8–1.2 % as lactic, vinegar 4–5 % as acetic. Tool 22 of 500 — GIFSQ
