L-Lactic acid in milk
Lactic acid is produced by the fermentation of lactose mainly through microbial activity. Its concentration depends on the total bacterial count and can be a useful indicator of the good state of preservation. In addition, the heat treatment at high temperatures, such as UHT milk, reduces the microbial load but does not alter the concentration of lactic acid, which thus becomes an indicator of the “history” of the product. The test can also be run on derivatives in powder (whey, milk, additives) after reconstitution in water.
Analyzers for determining L-Lactic acid in milk and dairy products
 CDR FOODLAB® |  CDR FOODLAB® JUNIOR | |
|---|---|---|
| Analyses | e-Fructosyl Lisine L-Lactic Acid Ammonia Chloride Alkaline phosphatase (ALP) Peroxidase Hydrogen peroxide Milk Urea Nitrogen (MUN) Lactose Peroxide value (PV) Free Fatty Acids (FFA) | Configuration with tailored panel of analyses |
| Simultaneous Sample Analyses | 16 | 3 |
| Multiple Analyses on a Sample |  | – |
It is not necessary skilled staff nor a laboratory for the analysis.
Results are correlated with reference method results.
It is free of service and maintenance cost.
With the same analyzers you can also perform analysis of egg, tomato, vegetable purees, cheeses and fats.
Methods
Test type: End Point
Time of test: 8 minutes:
It is possible to carry out several test sessions with a maximum of 16 samples.
Test principle
Ac.L-Lactic + der. Fenolico 
chinoneimina + H2O
L-Lactic acid is oxidized to pyruvate by an enzymatic reaction that produces H2O2. H2O2, in the presence of peroxidase and a phenolic derivate, forms a colored complex whose intensity was read at 545nm and is directly proportional to the concentration of L-lactic acid in the sample.
Calibration curve
Comparative tests on samples of whole milk between the reference method and the CDR FoodLab® method, performed in a leading company in production of milk, confirmed a very good alignment between the two systems.
Reagents Test Kits
The reagents are packaged in foil pouches containing 10 tubes useful to perform 10 analyses.
This is the minimum package that allows the use of CDR systems even to those who need to make a few analyses, thus not wasting reagents.
There are also boxes of 100 tests, however, packaged in 10 bags of 10 tubes containing the reagent.
Reagent test kit *300075 suitable for 100 tests
Reagent test kit *300076, suitable for 20 tests
The reagents have a shelf-life of 12 months.
Sample Handling
Use milk as is
Diluted samples: yogurt.
Homogenized samples in a diluted soda solution: cheese, mozzarella, ricotta.
Measuring range
| Analisys | Measuring range | Sample volume | Resolution | Repeatability |
|---|---|---|---|---|
| L-lactic acid milk | 2 – 250 ppm | 100 µL | 1 ppm | 5 ppm |
| L-lactic acid cream | 1,5 – 150 ppm | 100 µL | 1 ppm | 3 ppm |
| L-lactic acid ricotta | 0,02 – 0,43 g/100g | 50 µL | 0,01 g/100g | 0,03 g/100g |
| L-lactic acid mozzarella | 0,1 – 1,5 g/100g | 100 µL | 0,1 g/100g | 0,05 g/100g |
| L-lactic acid yogurt | 0,01 – 1,75 g/100g | 100 µL | 0,01 g/100g | 0,05 g/100g |
For samples with a value of lactic acid >200 ppm (milk) or >150 ppm (cream) use half of the sample volume (50 μL) and multiply the result by 2.
