Optical sensing of tea aroma using n-tetraphenyl porphine manganese (III) chloride thin films

The aroma emerging from food samples gives specific information on quality, freshness and flavours. This paper reports the use of a porphyrin derivative, n-tetraphenyl porphine manganese (III) chloride thin films for detection of tea aroma. The thin films were deposited on a glass substrate by the Langmuir-Blodgett technique. The experiments were performed using optical fiber reflectance with three different color LEDs, i.e. red (/spl lambda/=650 nm), yellow (/spl lambda/=585 nm) and green (/spl lambda/=563 nm), as light sources. The sensing sensitivity was measured based on the change in the optical absorption spectra of the reflected light from the film. The reflected light from the thin films was sensitive to the tea aroma. The intensity of the reflected light decreased in the presence of the aroma.