🔥 Total Ash in Meat and Meat Products

Food Chemistry PN-ISO 936

Overview

STATUS (as of 02.11.2026). PN-ISO 936:2000 — Polish version, published on 14.06.2000, implements ISO 936:1998 [IDT], replaced PN-A-82115:1989; the PKN catalogue card has no withdrawal note (read on 02.11.2026). ISO 936:1998 is the second edition of the standard (published on 30.07.1998), which replaced ISO 936:1978 “Meat and meat products — Determination of ash (Reference method)”; according to Standard Norge the 1998 edition is current. The description is based on the full text of ISO 936:1998 (iTeh preview).

SCOPE AND DEFINITION (clauses 1 and 3). A method for the determination of total ash in all kinds of meat and meat products, including poultry. Total ash is the mass of the residue obtained after incineration at (550 ± 25) °C under the operating conditions of the standard, divided by the mass of the test portion; it is usually expressed as a percentage.

PRINCIPLE (clause 4). A test portion is dried, carbonized and then incinerated at (550 ± 25) °C; after cooling, the mass of the residue is determined. The same ashing temperature, 550 °C, is given by the Nordic method NMKL No. 23 (moisture and ash in meat and meat products) — its interlaboratory study (K. Kolar, J. AOAC 1992) is cited in the bibliography of the standard as the source of the precision data — and by the successor of that method, NMKL No. 173 (ash in foods, ashing at 550 °C to constant mass).

REAGENTS AND APPARATUS (clauses 5–6). Water complying with at least grade 3 of ISO 3696 and hydrogen peroxide, 30 %. Equipment for homogenizing the sample — a high-speed rotational cutter or a mincer with a plate with holes not exceeding 4.0 mm in diameter; a flat-bottomed dish of porcelain, quartz, metal (for example nickel, platinum, stainless steel) or another material unaffected by the test conditions, at least 60 mm in diameter, with inclined walls at least 25 mm high; an electrically heated muffle furnace with a programmable time-temperature controller, capable of being maintained at (550 ± 25) °C; a desiccator with an efficient desiccant; an analytical balance weighing to the nearest 0.1 mg. A drying oven at (103 ± 2) °C and an electric hot plate or gas flame are needed only if the furnace has no controller.

SAMPLE (clauses 7–8). Sampling is not part of the standard (ISO 3100-1 is recommended); the laboratory should receive a truly representative sample that has not been damaged or changed during transport or storage, of at least 200 g. The sample is homogenized so that its temperature does not rise above 25 °C (with a mincer — at least two passes), stored in an airtight container and analysed as soon as practicable, always within 24 h after homogenization.

PROCEDURE (clause 9). The dish is heated for 20 min in the furnace at 550 °C, cooled in the desiccator to room temperature and weighed to the nearest 0.1 mg (m₀). 1.5 g to 2 g of the sample are weighed in, spread out evenly and weighed again without delay (m₁); if the analyst considers it appropriate in view of the nature of the sample, up to 5 g may be taken — this is noted in the test report. Furnace with controller: the dish is placed in the cool furnace, the temperature is raised gradually over 5 h to 6 h to (550 ± 25) °C and ashing is continued until the ash is grey-white. Furnace without controller: the dish is dried for 1 h at 103 °C, heated progressively on a hot plate or over a flame until the sample carbonizes with the evolution of smoke, and carbonization is carefully continued until smoke evolution ceases — the sample shall neither ignite nor burn with a flame; the dish is then transferred to the cool furnace, the temperature is raised to (550 ± 25) °C and the dish is removed after 4 h. In both variants the dish is cooled in the desiccator and the ash is inspected: black ash is moistened with a few drops of hydrogen peroxide or water and the ashing is repeated, grey-white ash is weighed to the nearest 0.1 mg (m₂). When the repeatability limit has to be checked, two single determinations are carried out.

RESULT AND PRECISION (clauses 10–11). wₐ = (m₂ − m₀) / (m₁ − m₀) · 100 %, the result rounded to the nearest 0.01 %. Repeatability limit r = 0.099 0 % + 0.009 33 · w̄, reproducibility limit R = 0.138 % + 0.004 6 · w̄, where w̄ is the mean of the two results as a percentage; the values were derived from an interlaboratory test according to ISO 5725 and may not apply to other concentration ranges and matrices.

FOOD LABELLING. The mandatory nutrition declaration under Regulation (EU) No 1169/2011 (Article 30(1)) covers energy value, fat, saturates, carbohydrate, sugars, protein and salt — it does not cover ash.

WHAT WE DO NOT GIVE HERE. The standard does not require repeated ashing to constant mass, does not provide for nitric acid to complete the ashing and does not give a cooling time in the desiccator — we give no such values here.

Method principle

A test portion of the homogenized sample (1.5 g to 2 g) in a weighed flat-bottomed dish is dried and carbonized and then incinerated in a muffle furnace at (550 ± 25) °C until the ash is grey-white. In a furnace with a controller the temperature is raised gradually over 5–6 h; in a furnace without a controller the sample is first dried for 1 h at 103 °C and carbonized on a hot plate or over a flame, and ashing takes 4 h.

Black ash is moistened with a few drops of hydrogen peroxide or water and ashed again. After cooling in the desiccator the residue is weighed; total ash is its mass relative to the mass of the test portion, as a percentage.

Applications

• All kinds of meat and meat products, including poultry — total ash (clause 1)
• Laboratories with a muffle furnace with or without a time-temperature controller — two variants of the procedure (9.2, 9.3)

Key parameters

Standard

Standard number

PN-ISO 936:2000

Title (PL)

Mięso i przetwory mięsne — Oznaczanie popiołu całkowitego

Title (EN)

Meat and meat products — Determination of total ash

Step-by-step procedure

1. Preparation of the sample

   At least 200 g of sample; homogenization without exceeding 25 °C (mincer — at least twice); airtight container; analysis within 24 h after homogenization (7, 8).

2. Dish and test portion

   Dish heated for 20 min in the furnace at 550 °C, cooled in the desiccator, weighed (m₀); 1.5 g to 2 g of sample spread out evenly, weighed without delay (m₁) — to the nearest 0.1 mg (9.1).

3. Ashing in a furnace with controller

   Dish into the cool furnace, gradual rise in temperature over 5–6 h to (550 ± 25) °C, ashing until a grey-white ash is obtained (9.2).

4. Or: drying, carbonization and ashing without controller

   1 h at 103 °C; heating on a hot plate or over a flame until carbonized and smoke evolution ceases, without ignition of the sample; cool furnace, (550 ± 25) °C, removal after 4 h (9.3).

5. Inspection of the ash and weighing

   Cooling in the desiccator; black ash — a few drops of hydrogen peroxide or water and repetition of the ashing; grey-white ash — weighing to the nearest 0.1 mg (m₂) (9.2–9.3).

6. Calculation of the result

   wₐ = (m₂ − m₀) / (m₁ − m₀) · 100 %, rounded to the nearest 0.01 %; when checking repeatability — two single determinations (10, 11.2).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• When transferring the dish with the ash from the furnace to the desiccator and from the desiccator to the balance, take care to avoid loss of ash (caution in the standard, 9.2–9.3)
• During carbonization the sample shall neither ignite nor burn with a flame (9.3)

Frequently asked questions