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ε-fructosil-lysine in milk

ε-fructosil-lysine in milk

Furosine and lactulose value are used to determine the effects of thermal treatment applied to milk or the addition of UHT or powdered milk to raw or pasteurized milk.
Through furosine it is determined the intensity of the initial phase of Maillard reaction that is responsible of the browning of heated milk. This reaction is linked to the thermal processes carried out in milk.

ε-fructosil-lysine is the first stable product of Maillard reaction and is converted into furosine determining the acid hydrolysis of milk. Then, furosine is measured using HPLC method. This method is very complex, expensive and takes a lot of time. Hence, the chemical test of e-fructosil-lysine, the first stable product of Maillard reaction and furosine precursor, can give the same indications given by furosine test.

Instrument

FoodLab

Comparative test

Parmalat® and CDR have collaborated in a study on e-fructose-lysine to evaluate the possibility of using it as an index of thermal treatment in milk.

Parallel assessments between furosine and e-fructose-lysine were preformed on various typologies of milk samples.
Through these results it was possible to align the results obtained with e-fructose-lysine test with those determined on furosine.
A good correlation between the two tests (R2 = 0.95) was verified.

E-fructose-lysine test has a good linearity (R2 = 0.99) and a good sensibility: it is possible to discriminate the addition of 10% of powdered milk into the raw milk.

A study was also performed on various types of milk with the goal of identifying, through the values of e-fructose-lysine, different classes of milk related to the thermal treatment received. E-fructose-lysine test permits to discriminate between: raw, pasteurized, direct UHT and indirect UHT milk, as it is done using furosine.

Reagents

Reagent R1 ( pre filled in test tube): Basic buffer - 10 g/L
Reagent R2 (in bottle): tetrazolium salt - 0,1 g/L

Test method

Test type: kinetic
Colour reading at 545 nm
Test time: 6 minutes
Calibration can be performed by aligning the test to reference values.

Test principle

The principle of the method is based on a redox reaction in which tetrazolium salt reacts with the e-fructose-lysine forming a purple complex whose intensity, measured at 545 nm, is proportional to the concentration of the e-fructose-lysine in milk.

Sample

Milk as is.

Kit

The reagents are provided in sealed bags, each containing 10 test tubes. They have a 12 months duration, starting from the production date. Stocking requirements are described on the bag label.
Reagents do not contain dangerous solvents and are ready for use.