Fig. 1. Three-dimensional fluorescence spectra of milk
(a): Whole milk C; (b): Skim milk C

Fig. 2. Fluorescence emission spectra of casein solution and 9 kinds of milk (excitation wavelength is 291 nm)

Fig. 3. Time resolved fluorescence spectra of 9 kinds of milk and casein solution

Fig. 4. Molecular structure of tryptophan, tyrosine and phenylalanine

Fig. 5. The normalized fluorescence emission spectra of whole milk C, skim milk and whole milk C after centrifugation (excitation wavelength is 291 nm)

Fig. 6. Full fluorescence emission spectrum of whole milk C and skimmed milk C (excitation wavelength is 291 nm)

Fig. 7. The light transmittance curve of 9 kinds of milk