ANNEX IIMETHODS OF ANALYSIS RELATING TO THE COMPOSITION OF EDIBLE CASEINS AND CASEINATES
METHOD 5
DETERMINATION OF ASH (including P2O5)
1.SCOPE AND FIELD OF APPLICATION
This method determines the ash (including P2O 5) content of:
rennet casein
2.DEFINITION
The ash (including P2O5) content: the content of ash as determined by the method specified.
3.PRINCIPLE
A portion of the sample is incinerated at 825 oC ± 25 oC to constant mass. The residue is determined by weighing and calculated as a percentage by mass of the sample.
4.APPARATUS
4.1. Analytical balance
4.2. Silica or platinum dish, about 70 mm diameter and 25 to 50 mm deep.
4.3. Electrical furnace with air circulation, capable of being controlled at 825 oC ± 25 oC.
4.4. Desiccator, containing freshly activated silica gel with a water content indicator or an equivalent desiccant.
5.PROCEDURE
5.1. Preparation of the test sample
As described in Section 1.2 of the General Provisions.
5.2. Preparation of the dish
Heat the dish (4.2) in the electrical furnace (4.3), controlled at 825 oC ± 25 oC, for 30 minutes. Allow the dish to cool somewhat and then place in the desiccator (4.4) to the temperature of the balance room and weigh to the nearest 0,1 mg.
5.3. Test portion
Weigh, to the nearest 0,1 mg approximately 3 grams of the test sample (5.1) directly into the prepared dish.
5.4. Determination
Heat the dish with its contents on a low flame, a hot plate or an I/R lamp until the test portion is completely charred, taking care that it does not burst into flame.
Transfer the dish to the electrical furnace (4.3), controlled at 825 oC ± 25 oC, and heat for at least one hour until all carbon has disappeared from the dish. Allow the dish to cool somewhat and then place in the desiccator (4.4) to the temperature of the balance room and weigh to the nearest 0,1 mg.
Repeat the operations of heating for approximately 30 minutes, in the electrical furnace (4.3), cooling and weighing, until the mass remains constant to within 1 mg or begins to increase. Record the minimum mass.
6.EXPRESSION OF RESULTS
6.1. Method of calculation and formula
The ash content of the sample, including P2O5, as a percentage per mass, is given by:
where:
is the mass, in grams, of the test portion;
is the mass, in grams, of the dish and residue;
is the mass, in grams, of the prepared dish.
Calculate the final result to the nearest 0,01 %.
6.2. Repeatability
The difference between the results of two determinations carried out simultaneously or in rapid succession on the same sample, by the same analyst, under the same conditions, shall not exceed 0,15 grams of ash per 100 grams of product.
This repeatability interval should be achieved in 95 % of the times that the method is correctly carried out.