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| DETERMINATION OF CHLORIDES ON CHEESE BY
FOODLAB |
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In the
industrial preparation of certain cheeses, such as mozzarella, it is
important to check that the quantity of salt added is of an optimum
concentration.
In a few minutes, the FoodLab system permits the
determination of the concentration of sodium chloride in homogenised cheese.
The preparation of the sample is extremely simplified in respect of the
official method (FIL-IDF 17 A). The sample is homogenised in a solution of
NaOH 0,25 N. It is not necessary to filter it, centrifuge it and nitric acid
is not utilised. The reliability and the precision of the method are
guaranteed by a calibration system that permits the alignment of the
instrument utilising well-known solutions.
The FoodLab system has been tested via recuperation
tests.
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| MATERIALS
AND CORRELATION METHODS |
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The FoodLab
method is based upon a colourmetric reaction in which the chloride ions
react with the mercury thiocyanate and with Iron ++ forming an orange
substance: its intensity, measured at 505 nm, is directly proportional to
its concentration in the sample. The FoodLab instrument is capable of
measuring the intensity of the colour by eliminating the interferences
caused by the turbidity of the solution.
A sample of mozzarella was homogenised in a solution of NaOH 0,25N and
analysed by the FoodLab instrument: 4 aliquots of samples were added with a
standard solution of sodium chloride of different concentrations and
analysed by the FoodLab instrument.
Furthermore,
five repeatability tests were carried out on each
sample.
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| RESULTS
AND DISCUSSION |
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| The FoodLab
system permitted an almost total recuperation of sodium chloride in the
various concentrations. The reference values and the tests carried out
utilising the FoodLab system are compared in Tab.1. The values are
comparable and the repeatability of the data is very good, as can be seen by
the standard deviation and by the VC calculated for each sample. In Fig.1,
the correlation coefficient of the straight line of regression (r = 0,998)
confirms the optimum alignment of the instrument to the reference
values. |
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| Fig.1
- Correlation between FoodLab method and reference method |
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| Tab.1 - Repeatability test using the FoodLab
system
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Ref
g NaCl |
0,67 |
1,1 |
1,9 |
2,5 |
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0,65 |
1,15 |
1,88 |
2,45 |
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0,67 |
1,1 |
1,92 |
2,5 |
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0,69 |
1,12 |
1,85 |
2,52 |
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0,63 |
1,08 |
1,86 |
2,55 |
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MEAN |
0,66 |
1,12 |
1,89 |
2,51 |
SD |
0,02 |
0,03 |
0,04 |
0,04 |
CV,% |
3,63% |
2,42% |
1,89% |
1,52% |
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| SHORT
TABLE |
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Linearity |
Accuracy |
Repeat. |
R2 |
Sensitivity |
Total
analysis
time
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Test/hour |
3,5 g % |
±5% |
CV < 5% |
r > 0,99 |
0,2 g % |
5 - 8 min |
70 |
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| Foodlab¬ |
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»A new concept in quality analysis of
food.
Foodlab is a quick, reliable and practical system for chemical tests on
olive oil, seed oils, alimentary fats, vegetable purées, milk, cheese
and other dairy products. |
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