GIFSQ Tools · Module 2 — Food Chemistry & Physicochemical Testing · Tool 26 of 500
Lane-Eynon titration after acid inversion: get total sugars as invert sugar and the sucrose content of the sample. AOAC 923.09.
Try sample values — fills the form with the worked example below.
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Total sugars as invert (%)
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Sucrose (%)
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Reducing sugar (%)
Equation: Total sugars as invert % = F × V ÷ (T × m × 10), where F is the Fehling factor in mg per 10 mL, V the dilution volume in mL, T the titre of the inverted solution in mL, and m the sample weight in g. Sucrose % = (total sugars as invert − reducing sugar %) × 0.95.
Method: AOAC 923.09, Lane-Eynon general volumetric method after acid inversion — sucrose is hydrolysed to glucose and fructose, then titrated against boiling Fehling’s solution. The factor 0.95 is 342.3 ÷ 360.3, the ratio of the molar mass of sucrose to the combined molar mass of glucose plus fructose.
Assumptions: inversion is complete; the reducing-sugar value comes from the same sample preparation (Tool 25); the Fehling factor suits the titre (see Tool 25).
Limitations: other sugars present are counted as invert sugar, and the sucrose figure is by difference, so an error in either titration lands in the sucrose result. The titre must fall between 15 and 50 mL.
Rounding: results to 2 decimal places.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: AOAC 923.09, Lane-Eynon general volumetric method after acid inversion — sucrose is hydrolysed to glucose and fructose, then titrated against boiling Fehling’s solution. The factor 0.95 is 342.3 ÷ 360.3, the ratio of the molar mass of sucrose to the combined molar mass of glucose plus fructose.
Assumptions: inversion is complete; the reducing-sugar value comes from the same sample preparation (Tool 25); the Fehling factor suits the titre (see Tool 25).
Limitations: other sugars present are counted as invert sugar, and the sucrose figure is by difference, so an error in either titration lands in the sucrose result. The titre must fall between 15 and 50 mL.
Rounding: results to 2 decimal places.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: 5.000 g of jam made up to 500 mL; after inversion, 25.0 mL of the solution reduces 10 mL of Fehling’s solution; factor 51.1 mg; reducing sugar before inversion 10.22 %. Total sugars as invert = 51.1 × 500 ÷ (25.0 × 5.000 × 10) = 20.44 %; sucrose = (20.44 − 10.22) × 0.95 = 9.71 %.
Enter values above to see results.
Typical total sugar: jam 60–65 %, honey 75–80 %, sweetened condensed milk 55–58 %, fruit juice 10–15 %. If the inverted titre is larger than the reducing-sugar titre, the inversion step needs checking. Tool 26 of 500 — GIFSQ
