405 nm-Excited Fluorescence Spectra of the Juice of the Lemon (Citrus x Limon)

A 405 nm diode laser is used to excite fluorescence of juices of raw and ripe lemons. Emission bands appear approximately at 520 nm and 670 nm. Fluorescence intensity ratio F520/F670 is determined for the two stages. Variation in the fluorescence intensity ratio is observed during the process of ripening or growth of the fruit. Time-resolved spectra at this excitation wavelength reveal two decay times at both the stages at the emission wavelength of 520 nm, and two decay times at the raw stage and one decay time at the ripe stage at 670 nm.