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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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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
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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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