🍎 Determination of titratable acidity of fruit and vegetable juices — 25 ml of sample is titrated potentiometrically with sodium hydroxide solution 0.25 mol/l to pH 8.1; result in millimoles H+ per litre (with 25 ml and 0.25 mol/l equal to the titrant volume times 10) or, after multiplying by a factor, as tartaric, malic or anhydrous citric acid in g/l, PN-EN 12147

Food chemistry PN-EN 12147

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the sample of SIST EN 12147:1998 (the text of EN 12147:1996 without changes) — a scan, read from the page images: contents, foreword and Clauses 1–10 (scope, normative references, definitions and symbols, principle, reagents, apparatus, procedure, calculation, precision, test report). Outside the sample remain Annex A (bibliography) and Annex B with statistical results of the interlaboratory test — we did not read these.

ACCORDING TO THE TEXT OF EN 12147:1996 (Clauses 1–10). The standard was prepared by CEN/TC 174 (secretariat AFNOR). Scope (1): a method for the determination of titratable acidity of fruit and vegetable juices and related products. Definition (3.1): titratable acidity is a measure of the content of mineral and organic acids determined by titration according to this standard. Principle (4): potentiometric titration with standard volumetric sodium hydroxide solution to pH 8.1. Reagents (5): only reagents of recognized analytical grade and degassed water of at least grade 3 according to EN ISO 3696:1995; sodium hydroxide, standard volumetric solution c(NaOH) = 0.25 mol/l; buffer solutions of suitable pH. Apparatus (6): pH meter accurate to at least 0.01 pH units, pH glass electrode and reference electrode (e.g. calomel) or instead a combination glass electrode, magnetic stirrer, burette of 25 ml graduated in 0.05 ml divisions, low-form beaker (typically 50 ml), one-mark pipette of 25 ml. Preparation of the test sample (7.1): normally products are not pre-treated and the analysis is on a volumetric basis, with the result per litre of sample; concentrated products may be analysed volumetrically after dilution to a known relative density, which is then indicated; based on a weighed sample and taking dilution into account, the result may also be expressed per kilogram of product; for high viscosity or a very high content of cells (e.g. pulp) a weighed test sample is the usual procedure. A sample containing appreciable quantities of carbon dioxide is degassed — by shaking in a stoppered conical flask and removing the stopper from time to time, or by vacuum or ultrasound — until no more gas evolves. Calibration (7.2): two-point calibration of the pH meter at 20 °C with buffer solutions, with agitation and following the manufacturer’s instructions; with temperature compensation calibration may be at another temperature, but in any case between 10 °C and 30 °C. Determination (7.3): at 20 °C transfer 25 ml of sample (V0) by pipette into the beaker, start the stirrer and titrate from the burette with sodium hydroxide solution until pH 8.1 is obtained; record the volume of solution used (V1); with temperature compensation the determination may be at another temperature, but between 10 °C and 30 °C. Calculation (8.1): titratable acidity in mmol H+ per litre of product = 1000 × V1 × c / V0, where V0 — volume of the test portion (as a rule 25 ml), V1 — volume of NaOH solution, c — exact concentration of NaOH in mol/l; with V0 = 25 ml and c = 0.25 mol/l the formula simplifies to V1 × 10; the result is reported without a decimal place. Conversion to acid (8.2): titratable acidity can conventionally be expressed as acid content in g/l by multiplying the result of 8.1 by a factor from Table 1 — tartaric acid 0.075, malic acid 0.067, citric acid anhydrous 0.064; dilution and the reference to mass or volume are taken into account; if a concentrated product was diluted to single strength, the relative density of the single-strength juice is reported; the result as tartaric, malic or anhydrous citric acid — in accordance with the regulations of the country concerned — is reported to one decimal place. Precision (9): details of the interlaboratory test are in Annex B, and the values from it may not be applicable to concentration ranges and matrices other than those given there; repeatability r = 1.03 mmol H+/l, reproducibility R = 2.28 mmol H+/l (each exceeded in not more than 5 % of cases). Test report (10): identification of the sample, reference to the standard, date and type of sampling (if known), dates of receipt and test, results and units, whether repeatability was verified, particular observations and operations not specified in the method or optional which might have affected the results.

STATUS (catalogue cards as of 03.10.2026). The card of PN-EN 12147:2000 (Polish version, published 11-01-2000, 10 pages, price group E) has the header “Withdrawn”: withdrawal date 09-04-2024; Food, Agriculture and Forestry Sector, KT 38 Fruit and Vegetable Products, ICS 67.160.20, “Introduces: EN 12147:1996 [IDT]”, “Supersedes: PN-A-75101-04:1990 — Polish version”. The card has no “Replaced by” field, and the PKN search (term “PN-EN 12147”, 03.10.2026) shows no other edition — PKN indicates no successor. The “Scope” field of the card, in full (our translation): “A method is presented for the determination of titratable acidity in fruit and vegetable juices by potentiometric titration of the analysed product with standard sodium hydroxide solution. The way of converting titratable acidity to acid content, the values of the relevant factors and the permissible limits for repeatability and reproducibility are given. Detailed data of the interlaboratory study of repeatability and reproducibility using fruit juices and nectar are also presented”. In the iTeh catalogue (read 03.10.2026) EN 12147:1996 has the status “Withdrawn”: stage 99.60 “Withdrawal effective”, procedure started 06.12.2023, withdrawal date 30.09.2026, without an indicated replacing document; the Slovenian adoption SIST EN 12147:1998 was withdrawn on 09.03.2026. The card of PN-A-75101-04:1990 (fruit and vegetable products — determination of total acidity, potentiometric method to pH 8.1 and visual method with phenolphthalein or indicator paper) has the header “Withdrawn”: withdrawal date 02-12-2011, “Replaced by: PN-EN 12147:2000”; its amendment Az1:2002 is also withdrawn with the same date. The chain of successors therefore ends with a standard withdrawn without a successor. The withdrawal does not change the method itself — the text is the same; it changes the fact that the standard is no longer a valid document, and neither PKN nor CEN indicates a successor to which one could move. In the current PCA scopes five laboratories still cite the 2000 edition, and AB 400 the designation without year (the newest of these documents is of 07.08.2026).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read 03.10.2026). The number 12147 appears in 6 records at 6 laboratories: AB 381, AB 400, AB 452, AB 532, AB 1095, AB 1334. In the current scopes on the PCA website (read 03.10.2026, issues from 30.10.2025 to 07.08.2026) five laboratories give “PN-EN 12147:2000”, and AB 381 “PN-EN-12147:2000” (with a hyphen after “EN”); AB 400 gives the designation alone without year. The “Laboratories” tab (“PN-EN 12147”) shows 5 laboratories — all except AB 381, whose notation with the hyphen does not begin with “PN-EN 12147”; under the term “PN-EN-12147” the tab shows exactly AB 381. Checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (PCA items). Juices, nectars, purées and soft drinks, fruit and vegetable juices, fruit and vegetable products, and at AB 400 — food in general. The items are called “Titratable acidity” (AB 400, AB 452, AB 532), “Total acidity” (AB 1095), “Acidity” (AB 1334) and “Acidity expressed as the acid used” (AB 381). Technique: potentiometric titration (AB 400, AB 452, AB 532, AB 1334) or “titration method” (AB 381, AB 1095). The ranges use four different units: mmol H+/l — (10–220) mmol H+/l (AB 532), g/l — (2.00–40.0) g/l (AB 452), (0.30–70) g/l (AB 1095), (0.1–20.0) g/l (AB 1334), and g/100 ml — (0.2–6.0) g/100 ml (AB 381); AB 400 gives no range. In the scope of AB 1334 just below, for fruit, vegetables and their products, there is “Acidity” (0.2–20.0) % according to PN-90/A-75101/04+Az1:2002 — a standard withdrawn in 2011 and replaced precisely by PN-EN 12147:2000. A range in g/l or g/100 ml corresponds to the conversion of 8.2, i.e. a result expressed as a particular acid — the scopes do not state which one.

WHERE A SEEMINGLY CORRECT RESULT IS EASY. At preparation: carbon dioxide in a carbonated drink or a fermenting juice consumes sodium hydroxide and raises the acidity — the sample is degassed before the determination (7.1). At measurement: the end point is pH 8.1 read on the pH meter, not a colour change of an indicator; calibration and determination take place at 20 °C, and at another temperature only with temperature compensation and in any case between 10 °C and 30 °C (7.2, 7.3). At calculation: the simplification “V1 × 10” applies only with V0 = 25 ml and c = 0.25 mol/l — with another dilution or another titrant concentration formula (1) must be used; the result “as acid” depends on the chosen factor (tartaric 0.075, malic 0.067, anhydrous citric 0.064), so the same sample gives three different numbers in g/l — the report must state as which acid it was expressed; for concentrated products the relative density after dilution is reported (8.2). The precision of Clause 9 relates to the matrices and concentrations of Annex B, which we did not read.

WHAT WE DO NOT GIVE. We did not read Annex B (matrices, concentration levels and number of laboratories in the interlaboratory test), so we do not give for which juices r and R were determined. The standard does not say how the sodium hydroxide solution is standardized or how long to degas the sample — beyond the condition that gas stops evolving. We do not give acidity requirements for individual juices, because the standard does not contain them.

Method principle

The mineral and organic acids contained in 25 ml of juice are neutralized with standard sodium hydroxide solution 0.25 mol/l while the pH is measured with a glass electrode; the titration ends at pH 8.1, and the volume of titrant used is converted to millimoles H+ per litre of product (with 25 ml and 0.25 mol/l — volume times 10), and if required further to grams of tartaric, malic or citric acid per litre.

Applications

• Fruit and vegetable juices, nectars, purées and related products — titratable acidity in mmol H+/l or as acid in g/l (Clauses 1, 8)
• Concentrated products — after dilution to a known relative density or on a weighed sample, with the result per kilogram of product (7.1)
• Soft drinks and fruit and vegetable products — in the accreditation scopes of 6 laboratories at PCA, with ranges in mmol H+/l, g/l and g/100 ml

Key parameters

Standard

Standard number

PN-EN 12147:2000

Title (PL)

Soki owocowe i warzywne — Oznaczanie kwasowości miareczkowej

Title (EN)

Fruit and vegetable juices — Determination of titratable acidity

Step-by-step procedure

1. Sample preparation

   Normally no pre-treatment; dilute a concentrated product to a known relative density or analyse on a weighed sample; degas a sample containing carbon dioxide until no more gas evolves. PN-EN 12147:2000 withdrawn 09-04-2024 without a successor (PKN catalogue card as of 03.10.2026).

2. Calibration of the pH meter

   Two-point, at 20 °C, with buffer solutions, with stirring; with temperature compensation — within 10–30 °C.

3. Titration

   25 ml of sample by pipette into the beaker at 20 °C; while stirring, titrate with NaOH 0.25 mol/l to pH 8.1; record the volume V1.

4. Calculation

   mmol H+/l = 1000 × V1 × c / V0 (with 25 ml and 0.25 mol/l: V1 × 10), without a decimal place; if required times the acid factor (0.075 / 0.067 / 0.064), g/l with one decimal place.

5. Test report

   Result with unit and — when converted — the name of the acid; relative density for concentrated products; whether repeatability was verified; operations outside the standard.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Sodium hydroxide solution is corrosive to skin and eyes — goggles and gloves; the standard in the text read contains no separate warnings
• Degassing in a stoppered flask builds up pressure — open the stopper frequently and carefully (7.1)

Frequently asked questions