e-fructosyl-lysine (Furosine) test in milk
The analisys of e-fructosil-lisine is an innovative method studied in CDR’s research laboratories to assess the effects of milk thermal treatments or or the addition of powder milk or UHT to crude or pasteurized milk that can be determined by using indicators like furosine and lactulose.
The laboratory of PARMALAT S.P.A. conduct a study realized the reliability and applicability of the test of e-fructosil-lisine made by CDR concluding that the result are equivalent to those obtained through determination of furosine
Analyzers for determining e-fructosyl-lisine (Furosine) 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.
Method
Test type: kinetic
Reading color a 545 nm
Time test: 6 minutes
Calibration can be performed by aligning the test to reference values.
Test principle
The effects of milk thermal treatments or the addition of powder milk or UHT to crude or pasteurized milk can be determined by using indicators like furosine and lactulose.
The determination of furosine enables to assess the intensity of the initial phase of Maillard’s reaction (that causes heated milk to develop a brownish color), which is in turn linked to milk thermal processes.
The e-fructosyl-lysine is the first stable product of Maillard’s reaction and can be converted into furosine by subjecting milk to an acid hydrolysis. Furosine is then analyzed with the HPLC method, which is rather long, complex and expensive. Thus the efructosyl-lysine, which is the first stable product of Maillard’s reaction and a precursor of furosine, can provide the same information resulting from the furosine test.
e-fructosyl-lysine + tetrazol salt 
purple complex
The test principle is based on a Redox reaction during which the tetrazol salt reacts with efructosyllysine forming a purple compound whose intensity, measured at 545 nm is directly proportional to the concentration of efructosyl-lysine
Calibration curve
Parmalat® and CDR have collaborated in a study on e-fructosyl-lysine to evaluate the possibility of using it as an index of thermal treatment in milk. Furosine and e -fructosyl-lysine tests were carried out in parallel on several types of milk samples. The correlation between the two tests (R=0.95) is good. These results indicate that e-fructosyl-lysine and furosine values can be aligned.
The e fructose-lysine test has a good linearity (R2 = 0.99).
An internal CDR study on several types of milks enabled to determine the different classes of thermal treatments by using the e-fructosyl-lysine values. The e-fructosyl-lysine test, like the furosine test, enables to distinguish the main types of thermal treatments and between crude, pasteurized and UHT milk.
The discriminating limit values for the single classes shown in the table below are indicative. Users of the test should always define internal references to be able to assess the quality of the thermal treatment with a greater accuracy.
| Type of milk | e-fructosyl-lysine delta x 1000 |
|---|---|
| Raw | < 30 |
| Pasteurized | 30 – 80 |
| UHT | > 80 |
The linearity of the e-fructosyl-lysine test was also checked by adding incremental quantities of powder milk to whole pasteurized milk. As for furosine, the trend was linear (R furosine=0.997, R e-fructosyl-lysine=0.993) and sensitivity was good because the test was able to identify a 10% addition of powder milk in the pasteurized milk.
Reagent 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 *300400, Suitable for 100 tests
Reagent test kit *300404, Suitable for 10 tests
The reagents have a shelf-life of 12 months.
Processing – Sample Volume – Measuring range
Sample
Use milk as is
| Measuring range Delta x 1000 | Sample Volume | Resolution Delta x 1000 | Repeatability |
|---|---|---|---|
| 10-1000 | 150 µL | 1 | 50 U/L |
