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| DETERMINATION OF CHLORIDE ON FOODSTUFF (MILK, VEGETABLE PURÉES) USING FOODLAB |
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Chloride testing makes it possible to identify any additions of salt water to the milk. Furthermore, the animal affected by mastitis shows chloride values that are significantly higher in just-milked milk.
With the FoodLab system, it is possible to determine the concentration of chlorides in just a few minutes in whole or skim, raw or pasteurized milk, without any previous treatment of the sample.
Furthermore, the FoodLab analyzer, using previously dispensed, non-returnable (disposable) cuvettes, requires neither specialized personnel nor reagent preparation.
The method's reliability and precision are guaranteed by a calibration system that makes it possible to align the instrument using known milk samples.
The FoodLab system was compared to the Mohr Method (reference method). |
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| MATERIALS AND CORRELATION METHODS |
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The FoodLab method is based on a colorimetric reaction in which the chloride ions react with the mercuric thiocyanate and with the Fe (II), forming an orange complex whose 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 color, eliminating the interferences due to milk's turbidity.
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| RESULTS AND DISCUSSION |
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The whole and skim milk values obtained by calibrating the FoodLab with the milk samples tested using the reference method are shown in the figures ( Fig. 1 - skim milk and Fig. 2 - whole milk). The regression line correlation coefficient (r > 0.99) indicates that the FoodLab system is in perfect agreement with the reference method.
The values obtained from the daily calibration of FoodLab are shown in the tables ( Tab.1 - skim milk and Tab.2 - whole milk). The instrument aligns itself with the reference every day, maintaining r > 0.99. This guarantees the repeatability of the data as is also confirmed by the standard deviation and by the VC computed for each reference sample. |
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| Fig.1 -
Correlation between FoodLab method and reference method - skim milk
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| Fig.2 -
Correlation between FoodLab method and reference method - whole milk
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| Tab 1 -
Daily calibration with FoodLab system using known ¹ milk samples used to verify the accuracy. Skim milk |
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Ref
mg/dL |
149 |
163 |
174 |
186 |
192 |
200 |
204 |
220 |
r |
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148 |
166 |
177 |
190 |
187 |
196 |
202 |
217 |
0,990 |
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147 |
162 |
175 |
188 |
190 |
205 |
205 |
222 |
0,997 |
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146 |
165 |
170 |
183 |
190 |
200 |
201 |
216 |
0,996 |
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152 |
166 |
177 |
185 |
193 |
198 |
208 |
220 |
0,996 |
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MEAN |
147,8 |
163,8 |
174,4 |
187,4 |
189,8 |
199,0 |
202,8 |
218,6 |
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SD |
2,49 |
2,68 |
2,97 |
3,36 |
2,17 |
3,74 |
3,83 |
2,41 |
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CV,% |
1,7 |
1,6 |
1,7 |
1,8 |
1,1 |
1,9 |
1,9 |
1,1 |
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r Linear regression correlation coefficient computed on the values obtained by the automatic calibration of FoodLab
1 Frozen aliquots of known milk (reference method), thawed out every morning for calibration of the instrument.
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| Tab 2 -
Daily calibration with FoodLab system using known ¹ milk samples used to verify the accuracy. Whole milk |
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Ref
mg/dL |
145 |
157 |
160 |
172 |
185 |
189 |
202 |
215 |
r |
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147 |
161 |
159 |
175 |
183 |
189 |
204 |
218 |
0,996 |
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148 |
159 |
159 |
178 |
181 |
192 |
206 |
215 |
0,991 |
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146 |
156 |
163 |
170 |
187 |
188 |
200 |
213 |
0,997 |
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153 |
161 |
160 |
175 |
185 |
193 |
205 |
218 |
0,995 |
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MEAN |
147,8 |
159,0 |
160,8 |
173,6 |
183,0 |
189,8 |
203,4 |
214,8 |
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SD |
3,11 |
2,12 |
2,05 |
3,51 |
3,16 |
2,59 |
2,41 |
3,42 |
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CV,% |
2,1 |
1,3 |
1,3 |
2,0 |
1,7 |
1,4 |
1,2 |
1,6 |
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r Linear regression correlation coefficient computed on the values obtained by the automatic calibration of FoodLab
1 Frozen aliquots of known milk (reference method), thawed out every morning for calibration of the instrument.
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| SHORT TABLE |
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Linearity |
Accuracy |
Repeat. |
R2 |
Sensitivity |
Total
analysis
time |
Test/hour |
400 mg/dL |
± 2% |
CV < 2,5% |
r > 0,99 |
50 mg/dL |
5 - 8 min |
70 |
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