LABORATORY CATALOGUE for milk analysis - Labochema

3.14 ... in mayonnaise acc. to Roeder’s meth. (weighing meth.)
Use of butter butyrometer according to Roeder’s method.
1 g of mayonnaise is weighed out into glass beaker situated in the stopper and transferred
into the butyrometer. Sulphuric acid (density: 1.522 +/- 0.005 g/ml) is poured
through the upper opening of the butyrometer until it reaches just over the upper edge
of the glass beaker. After sealing, the butyrometer is placed in a 70°C water bath for 30
minutes and shaken repeatedly until the protein is completely dissolved. Sulphuric acid
is poured in until it reaches the beginning of the scale, followed by 1 ml of amyl alcohol.
The butyrometer is sealed, shaken, and placed in the 70°C water bath for an additional
5 minutes. This process is followed by 10 minutes of centrifuging and approximately 5
minutes of tempering in a 65°C water bath. The value is read off at 65°C at the lower
meniscus. The read-off value is multiplied by 5 to obtain the correct fat content.
3.15 butyrometric determination of the fat content of
meat and sausage acc. to Gerber’s method (Van Gulik)
According to the recommended methodology of “Pohja and Associates“.
Instruments:
1. Butyrometer
Cheese butyrometer according to Van Gulik’s method
2. Centrifuge
Milk centrifuge with an RCF (relative centrifugal force)
of 350 g +/- 50 g
(e.g. SuperVario-N or Nova Safety)
3. Water bath
Shaking water bath with a temperature of
65°C +/- 2°C
4. Precision scale
5. Appliances for sampling preparation
A mixer or the like is recommended for reducing
or homogenising the sample.
Chemicals:
1. Sulphuric acid
Density of (1,818 +/- 0,003) g ml-1 at 20°C, colourless
or only slightly discoloured and free from any substances
which might influence the outcome
2. Amyl alcohol
Density of (0,811 +/- 0,003) g ml -1 at 20°C
Procedure:
Firstly, the perforated glass cylinder (cheese beaker) of the
cheese butyrometer is fitted into the butyrometer stopper
(this stopper is fashioned with a hole). Then, exactly 2,500 g
of the homogenised sample is weighed and introduced into
the glass cylinder (“cheese beaker”). The cheese beaker and
stopper are attached to the body of the butyrometer. 10 ml of
sulphuric acid, diluted with water in a volume ratio of 1:1, is
poured into the small opening on the upper end of the butyrometer.
The small opening is sealed with the small compatible
stopper and placed in a shaking water bath, where it is left
at 65°C for approximately 30 to 40 minutes, until all proteins
are dissolved. Then, 1 ml of amyl alcohol is pipetted into the
butyrometer and, after renewed sealing, is shaken powerfully.
Afterwards, sulphuric acid is added until the overall fluid
level is at about 30% on the scale. Then the butyrometer is
centrifuged for 5 minutes at 350 g. Note: the centrifuge must
be loaded evenly. I.e. one butyrometer cannot be centrifuged
alone – this leads to an unbalance and the risk of glass breaking.
The butyrometers are then placed in the water bath to
be tempered, i.e. the shaking mechanism is turned off. The
reading should be taken immediately after the specimens
are taken out of the water bath as the fat column diminishes
significantly at very small temperature decreases, resulting
in too low fat content read-off values. The butyrometers are
dimensioned for samples of 3,000 g, meaning that the determined
values are to be assessed at this substance amount
(increase by 16.666 %).
Laboratory catalogue for milk analysis
23