🧂 Chloride (as NaCl) in Meat and Meat Products — Volhard Method

Food Chemistry PN-ISO 1841-1

Overview

STATUS (as of 02.11.2026). PN-ISO 1841-1:2002 — Polish version, implements ISO 1841-1:1996 [IDT]; according to the PKN catalogue card (read on 02.11.2026) published on 05.11.2002 and withdrawn on 06.07.2018, with no replacing standard indicated. Part 2 — PN-ISO 1841-2:2002 (potentiometric method) — was withdrawn in the same way. The standard ISO 1841-1:1996 — the first edition of this part, which replaced ISO 1841:1981 — remains current according to Standard Norge, so the content of the method has not changed. The description is based on the full text of ISO 1841-1:1996 (French version, iTeh preview).

SCOPE AND DEFINITION (clauses 1–2). A method for the determination of the chloride content of meat and meat products, including poultry, with a sodium chloride content equal to or greater than 1.0 % (m/m). The result is the total chloride content determined by this method, expressed as a percentage by mass of sodium chloride. The lower limit is justified by an ISO interlaboratory study comparing the Volhard method with potentiometric titration (P. R. Beljaars, W. Horwitz, J. Assoc. Off. Anal. Chem. 1985): the repeatability of the Volhard method was poorer, especially below 1.0 % sodium chloride, so a lowest determination level of about 1.0 % was proposed for it.

PRINCIPLE (clause 3). A test portion is extracted with hot water and the proteins are precipitated. After acidification, an excess of silver nitrate solution is added to the filtrate and the excess is titrated with potassium thiocyanate solution.

REAGENTS (clause 4). Halogen-free distilled water (test: to 100 ml of water add 1 ml of silver nitrate 0.1 mol/l and 5 ml of nitric acid 4 mol/l — only a slight turbidity may appear). Nitrobenzene or 1-nonanol. Nitric acid 4 mol/l — 1 volume of concentrated acid (ρ20 from 1.39 g/ml to 1.42 g/ml) and 3 volumes of water. Protein precipitation solutions: A — 106 g of potassium hexacyanoferrate(II) trihydrate in water to 1000 ml; B — 220 g of zinc acetate dihydrate in water with 30 ml of glacial acetic acid, to 1000 ml. Silver nitrate 0.1 mol/l — 16.989 g of the salt dried for 2 h at (150 ± 2) °C and cooled in a desiccator, in water to 1000 ml; stored in a dark glass bottle, away from direct light. Potassium thiocyanate 0.1 mol/l — about 9.7 g in water to 1000 ml, standardized to the nearest 0.000 1 mol/l against the silver nitrate solution using the iron indicator. Indicator — aqueous solution of ammonium iron(III) sulfate dodecahydrate, saturated at room temperature.

APPARATUS (clause 5). Homogenizing equipment — a high-speed rotational cutter or a mincer with a plate with holes not exceeding 4 mm in diameter; 200 ml and 1000 ml volumetric flasks; conical flasks of about 250 ml; a 25 ml or 50 ml burette; 20 ml one-mark pipettes; a boiling water bath; an analytical balance accurate to ±0.001 g.

SAMPLE (clauses 6–7). Sampling is not part of the standard (ISO 3100-1 is recommended); representative sample of at least 200 g. Homogenization without exceeding 25 °C (mincer — at least twice), airtight container, analysis as soon as practicable after homogenization, always within 24 h.

PROCEDURE (clause 8). About 10 g of the sample are weighed to the nearest 0.001 g into a conical flask, 100 ml of hot water are added and the flask is heated for 15 min in a boiling water bath, shaking from time to time. After cooling to room temperature, 2 ml of solution A and then 2 ml of solution B are added, mixing after each addition, the flask is left for 30 min, the contents are transferred quantitatively to a 200 ml volumetric flask, made up to the mark with water, mixed and filtered through a fluted filter paper. When the method is also used for the determination of nitrate and nitrite, or the sample contains more than 0.1 % ascorbic acid, 0.5 g of activated carbon is also added to the test portion, and after mixing in solutions A and B the pH is adjusted to between 7.5 and 8.3 with sodium hydroxide. 20 ml of the filtrate are pipetted into a conical flask, 5 ml of nitric acid 4 mol/l and 1 ml of indicator are added with a measuring cylinder, 20 ml of silver nitrate with a pipette and 3 ml of nitrobenzene or 1-nonanol with a measuring cylinder; the contents are mixed and shaken vigorously to coagulate the precipitate. The mixture is titrated with potassium thiocyanate until a permanent pink colour appears and the volume is recorded to the nearest 0.05 ml. A blank test is carried out in the same way with the same volume of silver nitrate. When the repeatability has to be checked, two separate determinations are carried out under repeatability conditions.

RESULT AND PRECISION (clauses 9–10). w = 0.058 44 · (V₂ − V₁) · 200/20 · 100/m · c = 58.44 · (V₂ − V₁) · c / m, as a percentage by mass of sodium chloride, where V₁ is the volume of thiocyanate used for the determination, V₂ — for the blank test (ml), c — the concentration of the thiocyanate (mol/l), m — the mass of the test portion (g); the result is reported to the nearest 0.05 % (m/m). Repeatability: the difference between two results not more than 0.15 % (m/m) at sodium chloride contents from 1.0 % to 2.0 % and 0.20 % (m/m) above 2.0 %; reproducibility: 0.20 % and 0.30 % (m/m) in the same ranges; confidence level 95 %.

FOOD LABELLING. Regulation (EU) No 1169/2011 requires salt to be given in the mandatory nutrition declaration (Article 30(1)) and defines it as the salt equivalent content calculated using the formula: salt = sodium × 2.5 (Annex I, point 11). The result of this method is chloride expressed as sodium chloride — it is not a quantity derived from the sodium content.

WHAT WE DO NOT GIVE HERE. Direct titration with silver nitrate using potassium chromate — this standard does not cover it; results for products containing less than 1.0 % sodium chloride — they are outside the scope of the standard.

Method principle

A test portion of the sample (about 10 g) is heated with hot water in a boiling water bath, and the proteins are precipitated with potassium hexacyanoferrate(II) and zinc acetate solutions; the suspension is made up to 200 ml and filtered. A measured excess of silver nitrate is added to 20 ml of the filtrate acidified with nitric acid — the chlorides are precipitated as silver chloride.

After the addition of nitrobenzene or 1-nonanol and coagulation of the precipitate, the excess silver ions are titrated with potassium thiocyanate in the presence of ammonium iron(III) sulfate to a permanent pink colour. The chloride content, expressed as sodium chloride, is calculated from the difference between the volumes of thiocyanate used for the blank test and for the determination.

Applications

• Meat and meat products, including poultry, with a sodium chloride content of at least 1.0 % (m/m) — chloride as NaCl (clause 1)
• Samples with more than 0.1 % ascorbic acid, or a filtrate for the determination of nitrate and nitrite — with activated carbon and pH from 7.5 to 8.3 (note 2 to 8.2)
• Mandatory salt declaration on the label — under Regulation (EU) No 1169/2011 salt is calculated from the sodium content (salt = sodium × 2.5), not from chloride

Key parameters

Standard

Standard number

PN-ISO 1841-1:2002

Title (PL)

Mięso i przetwory mięsne — Oznaczanie zawartości chlorków — Część 1: Metoda Volharda

Title (EN)

Meat and meat products — Determination of chloride content — Part 1: Volhard method

Step-by-step procedure

1. Preparation of the sample

   At least 200 g; homogenization without exceeding 25 °C (mincer — at least twice); airtight container; analysis within 24 h (6, 7).

2. Test portion and extraction

   About 10 g of sample (to the nearest 0.001 g) into a conical flask, 100 ml of hot water, 15 min in a boiling water bath with occasional shaking (8.1–8.2).

3. Deproteinization and filtration

   After cooling, 2 ml of solution A and 2 ml of solution B (mix after each), 30 min at room temperature, transfer to a 200 ml flask, make up with water, mix and filter through a fluted filter paper (8.2).

4. Precipitation of the chlorides

   20 ml of filtrate, 5 ml HNO₃ 4 mol/l, 1 ml of indicator, 20 ml AgNO₃ 0.1 mol/l, 3 ml of nitrobenzene or 1-nonanol; mix and shake vigorously to coagulate the precipitate (8.3).

5. Titration

   With potassium thiocyanate 0.1 mol/l to a permanent pink colour; volume to the nearest 0.05 ml (8.3).

6. Blank test

   Procedure 8.2–8.3 without the sample, with the same volume of silver nitrate (8.4).

7. Calculation of the result

   w = 58.44 · (V₂ − V₁) · c / m in % (m/m) NaCl, to the nearest 0.05 %; repeatability 0.15 % (1.0–2.0 % NaCl) or 0.20 % (above 2.0 %) (9, 10.1).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Nitrobenzene is toxic — the standard allows 1-nonanol instead (4.2); follow the safety data sheets
• Nitric acid and silver nitrate are corrosive — follow the safety data sheets; the silver nitrate solution is protected from light (4.5)

Frequently asked questions