On raw milk - 2025

Introduction

The proficiency testings and criteria marked with an ♦ are covered by the « accréditation n° 1-2473, comparaisons interlaboratoires, portée disponible sur www.cofrac.fr »/« n° 1-2473 accreditation, interlaboratory comparisons, scope available on www.cofrac.fr », and detailed flexible scope available there

Methods / Analytes

- fat determined using the Gerber method♦: 10 samples with fat varying from 15 to 49 g/l

- fat determined using the extraction♦ ethero-ammoniacal (or ethero-chlorhydric) or alternative methods (RMN): 10 samples with fat varying from 14.5 to 48g/kg

- true protein determined using the Amido Black method♦: 10 samples with protein varying from 24 to 37g/l

- total and non-protein nitrogen♦ determined using the Kjeldahl, Dumas or any other method:
- Total nitrogen : 10 samples with nitrogen varying from 3.5 to 6.5 g N/l
- Non-protein nitrogen: 3 samples of milk (NPN about 0.2 to 0.3 g N/l)
- 1 tryptophan solution
- 1 glycine solution in which the nitrogen concentration is equivalent to that of milk
- 1 tryptophan solution
- 1 ammonium sulphate solution
The nitrogen concentration of the solutions is equivalent to that of milk

- non-casein nitrogen determined using the Kjeldahl or any other method: 5 samples with casein varying from 0.7 to 1.2 g N/l

- lactose♦ (any method): 10 samples with lactose varying from 4.6 to 5.1 % + 1 lactose solution at a concentration equivalent to that of milk

- freezing point determined using the cryoscopic method♦: 10 samples with freezing point varying from -0.550 to -0.480 °C + 2 standard NaCl solutions for calibration

- dry matter♦ (any method): 10 samples with dry matter varying from 10 to 15 %

- urea♦ (any method except infrared): 10 samples with urea varying from 100 to 700 mg/l

- somatic cells♦ for all methods used: 10 samples containing between 50 000 and 1 600 000 cells/ml + 1 control sample

Number of samples

-1 set of 10 samples which are the same for the Gerber and Amido Black methods
-1 set of 10 samples which are the same for the Kjeldahl and Röse-Gottlieb methods
-1 set of 5 samples specific to the determination of casein
-1 set of 10 samples which are the same for the determination of dry matter and lactose, as well as cryoscopic measurements.
-1 set of 10 samples specific to the determination of urea
-1 set of 10 samples specific to the determination of somatic cells + 1 control sample

Packaging

- 30 ml polyethylene screw-capped vials with airtight seals for casein, urea and somatic cells, as well as the solutions

- 60 ml polyethylene screw-capped vials with airtight seals for all the other criteria

Preservation

addition of Bronopol to the samples (final concentration: 0.02 % and 0.05 % for somatic cells) (except for Kjeldahl and cryoscopic solutions)

Dispatch

in insulated box with ice packs by express carrier (see regulation for shipping times)

Storage in the laboratory

at 4 (± 2) °C

Validity of the samples

testing must be carried out 5 days after the date of dispatch for somatic cells and 10 days for the other criteria

Calendar of dispatch :

Subscription at least 10 days before each dispatch

Special conditions :

• For groups from 10 to 24 participating laboratories: 10 % discount,
• For groups from 25 participating laboratories: 15 % discount

Payment conditions :

within 1 month of receiving invoice