🍎 Free fat in meat and meat products — extraction with a solvent (Soxhlet)
In short
A dried test portion of 5–8 g of meat is extracted with n-hexane or light petroleum (at least 6 h in a Soxhlet apparatus); after the solvent has been evaporated and the flask dried at 103 °C, the free fat is calculated from the increase in mass. The test is performed according to PN-ISO 1444:2000; Test portion: 5–8 g, weighed to the nearest 0.001 g; the minimum content of free fat in the test portion not less than 0.05 g. The procedure comprises 9 steps (about 9 h in total); it is used for: Determination of the fat content in raw meat and meat products (cured meats, canned meat), The basic chemical composition of muscles in scientific and technological studies, Control of conformity with the specification and with the declared nutritional value.
At a glance
- Standard: PN-ISO 1444:2000
- Category: Food chemistry
- Procedure steps: 9
- Total time of stages: 9 h
- Test portion: 5–8 g, weighed to the nearest 0.001 g; the minimum content of free fat in the test portion not less than 0.05 g
- Solvent: n-hexane or light petroleum distilling at 40–60 °C, bromine number < 1, residue after evaporation ≤ 0.002 g per 100 ml
- Time of extraction: At least 6 h (Soxhlet); at least 2 h in a Soxtec or another automated system
Overview
The standard specifies a method of determining the content of free fat in meat and meat products by extraction. Free fat is the mass of the fat extracted under the conditions of the standard divided by the mass of the test portion, expressed as a percentage by mass. The description is based on the preview of ISO 1444:1996 (the French version), which PN-ISO 1444:2000 implements.
The method consists in the extraction with n-hexane or light petroleum of the dry residue obtained by the method of determining the moisture described in ISO 1442, the evaporation of the solvent, and then the drying and weighing of the extract. The laboratory sample (at least 200 g) is homogenised mechanically or electrically in such a way that its temperature does not exceed 25 °C, and it is analysed as soon as possible, always within 24 h.
The determination of fat according to PN-ISO 1444:2000 is routinely used in studies of the chemical composition of meat (for example in a paper on beef muscles from the Agricultural University in Kraków) and figures in the list of testing procedures of the QAFP branch booklet for canned meat.
Method principle
A test portion of 5–8 g of the prepared sample (weighed to the nearest 0.001 g) is dried in accordance with ISO 1442; the dried test portion from the determination of the moisture may also be used. The dry residue is transferred quantitatively into a degreased paper extraction thimble and extracted in a continuous or semi-continuous apparatus (of the Soxhlet type) with a solvent distilling in the range 40–60 °C, for at least 6 h (Soxtec or other automated systems: at least 2 h). The solvent is distilled off, the flask is dried for 1 h in a drying oven at 103 ± 2 °C, cooled in a desiccator and weighed to the nearest 0.001 g, the drying being repeated until two successive weighings do not differ by more than 0.1 % of the mass of the test portion. The content of free fat: wf = (m2 − m1)/m0 × 100 %, where m0 is the mass of the test portion taken for the drying, m1 the mass of the flask with the boiling regulators, m2 the mass of the flask with the regulators and the fat after the drying. The result is given to one decimal place.
Applications
- Determination of the fat content in raw meat and meat products (cured meats, canned meat)
- The basic chemical composition of muscles in scientific and technological studies
- Control of conformity with the specification and with the declared nutritional value
- The list of testing procedures of the QAFP quality system for canned meat
Key parameters
| Parameter | Value |
|---|---|
| Test portion | 5–8 g, weighed to the nearest 0.001 g; the minimum content of free fat in the test portion not less than 0.05 g |
| Solvent | n-hexane or light petroleum distilling at 40–60 °C, bromine number < 1, residue after evaporation ≤ 0.002 g per 100 ml |
| Time of extraction | At least 6 h (Soxhlet); at least 2 h in a Soxtec or another automated system |
| Drying of the flask | 1 h at 103 ± 2 °C, to constant mass (a difference ≤ 0.1 % of the mass of the test portion) |
| Precision | r = 0.05 + 0.06·wf; R = 0.04 + 0.06·wf (wf — the mean of two results, % by mass) |
| Result | Rounded to one decimal place |
Standard
- Standard number
- PN-ISO 1444:2000
- Title (PL)
- Mięso i przetwory mięsne — Oznaczanie zawartości tłuszczu wolnego
- Title (EN)
- Meat and meat products — Determination of free fat content
Step-by-step procedure
-
Preparation of the sample
Homogenise the laboratory sample (at least 200 g) so that the temperature does not exceed 25 °C; with a mincer pass the sample through at least twice. Keep it in a tightly closed vessel and analyse it within 24 h.
-
Test portion and drying
Weigh out 5–8 g of the sample to the nearest 0.001 g (m0) and dry it in accordance with ISO 1442; the dried test portion from the determination of the moisture may be used.
-
Preparation of the flask
Dry the flask of the apparatus with the boiling regulators for 1 h in a drying oven at 103 °C, cool it in a desiccator to ambient temperature and weigh it to the nearest 0.001 g (m1).
-
Filling of the thimble
Transfer the dried test portion quantitatively from the evaporating dish into the extraction thimble; collect the remains with cotton wool moistened with the solvent and place it in the thimble as well. Put the thimble into the extractor.
-
Extraction
Pour into the flask a volume of solvent at least 1.5–2 times greater than the capacity of the extractor, connect the apparatus and heat it on the bath for at least 6 h (Soxtec or another automated technique: at least 2 h).
-
Evaporation of the solvent
After the extraction distil the solvent off from the flask on a sand or water bath; remove the last traces, if necessary with a stream of air.
-
Drying to constant mass
Dry the flask for 1 h at 103 °C, cool it in a desiccator and weigh it to the nearest 0.001 g. Repeat the heating, cooling and weighing until two successive weighings do not differ by more than 0.1 % of the mass of the test portion (m2).
-
Check of the completeness of the extraction
Put a second flask in place and extract for a further 1 h with a fresh portion of solvent; the increase in mass must not exceed 0.1 % of the mass of the test portion.
-
Calculation and test report
wf = (m2 − m1)/m0 × 100 %; give the result to one decimal place, the method of sampling, the method used and all the departures from the standard. The difference between two results under conditions of repeatability should not exceed r = 0.05 + 0.06·wf.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Homogeniser | A high-speed rotary knife or a mincer with a plate with holes not larger than 4 mm | — |
| Continuous or semi-continuous extraction apparatus | Of the Soxhlet type; systems for the simultaneous extraction of several samples, for example Soxtec, are permitted | — |
| Extraction thimble | Of filter paper, degreased; degreased cotton wool | — |
| Sand or water bath | Electrically heated or another suitable device | — |
| Drying oven | Electrically heated, controlled at 103 ± 2 °C | — |
| Analytical balance and desiccator | An accuracy of 0.001 g; a desiccator with an effective drying agent, for example silica gel | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| n-Hexane | 110-54-3 | The extraction solvent; a bromine number below 1, a residue after complete evaporation of not more than 0.002 g per 100 ml |
| Light petroleum | — | An alternative solvent, distilling in the range 40–60 °C, with the same requirements of purity |
| Boiling regulators | — | Placed in the flask of the extraction apparatus; weighed together with the flask |
Health and safety (OHS)
- n-Hexane and light petroleum are highly flammable — the extraction and the evaporation under a fume hood, away from sources of ignition, the bath electrically heated
- The vapours of the solvents act on the nervous system — ventilation and a tight apparatus
- A hot flask from the drying oven at 103 °C — tongs and gloves; cool it in a desiccator
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-ISO 1444:2000 — “Meat and meat products — Determination of free fat content”.
How does this method work?
A test portion of 5–8 g of the prepared sample (weighed to the nearest 0.001 g) is dried in accordance with ISO 1442; the dried test portion from the determination of the moisture may also be used.
What is the measuring range and accuracy?
Test portion: 5–8 g, weighed to the nearest 0.001 g; the minimum content of free fat in the test portion not less than 0.05 g; Solvent: n-hexane or light petroleum distilling at 40–60 °C, bromine number < 1, residue after evaporation ≤ 0.002 g per 100 ml; Time of extraction: At least 6 h (Soxhlet); at least 2 h in a Soxtec or another automated system; Drying of the flask: 1 h at 103 ± 2 °C, to constant mass (a difference ≤ 0.1 % of the mass of the test portion).
How long does the test take?
The times given for the individual stages add up to approximately 9 h. The procedure comprises 9 steps.
What equipment is required?
Homogeniser, Continuous or semi-continuous extraction apparatus, Extraction thimble, Sand or water bath, Drying oven, Analytical balance and desiccator.
Where is this test used?
Determination of the fat content in raw meat and meat products (cured meats, canned meat); The basic chemical composition of muscles in scientific and technological studies; Control of conformity with the specification and with the declared nutritional value; The list of testing procedures of the QAFP quality system for canned meat.
What safety precautions apply?
n-Hexane and light petroleum are highly flammable — the extraction and the evaporation under a fume hood, away from sources of ignition, the bath electrically heated; The vapours of the solvents act on the nervous system — ventilation and a tight apparatus; A hot flask from the drying oven at 103 °C — tongs and gloves; cool it in a desiccator.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-ISO 1444.