Time resolved fluorescence of milk powders - A pilot study

The investigation of the authenticity and classification of milk powder is particularly important. The use of time-resolved fluorescence could help develop a new method to assist milk powder classification and assess composition. This study used static and time-resolved fluorescence to differentiate powder milk samples. We observed fluorescence lifetimes of (in ns) 1.5 ± 0.2, 3.5 ± 0.2 and 6.0 ± 0.2 for skimmed; 1.3 ± 0.2, 3.3 ± 0.2 and 6.0 ± 0.4 for whole; and 1.4 ± 0.2, 3.4 ± 0.3 and 6.0 ± 0.4 for semi-skimmed powder milk at 270/335 nm excitation/emission. In addition, we observed fluorescence lifetimes of (in ns) 1.4 ± 0.1, 6.4 ± 0.2 and 14.8 ± 1.1 for skimmed; 1.6 ± 0.2, 6.8 ± 0.2 and 29.5 ± 1.7 for whole; and 1.7 ± 0.1, 6.8 ± 0.2 and 26.1 ± 1.3 for semi-skimmed powder milk at 315/468 nm excitation/emission. Employing analysis of variance, we differentiated all powder samples and achieved accuracy of 100% by discriminant analysis at 315/468 nm excitation/emission fluorescence. These results indicate that time-resolved fluorescence can assist in the classification of powder milk and its composition.