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| DETERMINATION OF L-LACTIC ACID ON FOODSTUFF USING FOODLAB |
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Lactic Acid is the product of lactose fermentation, mainly the result of microbial activity. Its concentration is correlated to the total bacterial charge and can be a useful indicator of good state of preservation of certain food products like milk, vegetable purées, cheese and other dairy product
The FoodLab system (www.foodlab.cdr-mediared.it) makes it possible to determine in just a few minutes the concentration of lactic acid in whole or skim, raw or pasteurized milk and puree, without any previous treatment of the sample, thus lowering the risk of possible contamination during handling.
Otherwise the preparation of the sample of cheese, ricotta or mozzarella 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. 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 tested through recovery tests. |
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| MATERIALS AND CORRELATION METHODS |
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The FoodLab method is based on an enzymatic reaction that leads to the formation of a violet complex whose intensity, measured at 545 nm, is directly proportional to the concentration of lactic acid in the sample.
Recovery tests were carried out on a sample of fresh milk without lactic acid: a standard solution of lactic acid in various concentrations was added to 5 aliquots of milk, which were then tested with FoodLab.
Five (5) repeatability tests were also carried out for each sample. |
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| RESULTS AND DISCUSSION |
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| With the FoodLab system, a practically total recovery of lactic acid at the various concentrations is possible. The reference values and the tests carried out using the FoodLab system are compared in Tab. 1. The values are perfectly comparable and the repeatability of the data is very good, as seen from the standard deviation and from the VC (Variation Coefficient) computed for each sample. In Fig. 1, the regression line correlation coefficient (r = 0.998) confirms the optimum agreement of the instrument with the reference method. |
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| Fig.1 - Correlation between FoodLab method and reference method |
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| Tab 1 - Repeatability tests with the FoodLab system |
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Ref
ppM |
5,0 |
7,2 |
8,4 |
15,2 |
23,2 |
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4,5 |
7,9 |
7,9 |
16,0 |
25,1 |
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4,6 |
7,5 |
7,8 |
15,5 |
24,5 |
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4,8 |
6,9 |
8,2 |
16,2 |
25,3 |
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4,5 |
7,6 |
8,0 |
16,5 |
25,5 |
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MEAN |
4,7 |
7,5 |
8,0 |
16,0 |
24,9 |
SD |
0,25 |
0,37 |
0,16 |
0,38 |
0,52 |
CV,% |
5,4 |
4,9 |
2,0 |
2,4 |
2,1 |
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| SHORT TABLE |
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Linearity |
Accuracy |
Repeat. |
R2 |
Sensitivity |
Total
analysis
time |
Test/hour |
60 ppM |
± 10% |
CV < 6% |
r > 0,99 |
2 ppM |
7-12 min |
60 |
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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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| Application Sheet |
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