Regensburg 1998 – scientific programme

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AOE: Agrar- und Ökosystemphysik

AOE 4: Poster

AOE 4.13: Poster

Tuesday, March 24, 1998, 17:00–19:00, Posterbereich C

Luminescence, EPR and IR Methods for Sensing Quality of Fruits — •Hans J. Hellebrand², Gertz I. Likhtenshtein¹, Evgeniya Shutyaeva¹, Alexander Shames³, and Kalman Hideg⁴ — ¹Ben-Gurion University of the Negev, Dept. of Chemistry, P.O.B. 653, Beer-Sheva 84105, Israel — ²Institute of Agricultural Engineering Bornim, Max-Eyth-Allee 100, D-14469 Potsdam — ³Ben-Gurion University of the Negev, Dept. of Physics, P.O.B. 653, Beer-Sheva 84105, Israel — ⁴The Chemico-Medical University, Pecs, Hungary

Quality of fruits depends, in particular, on moisture and vitamin C content. The evaluation of infrared remission at different wavelengths (water band and outside of water band) is a well known principle for surface water detection. Knowing the correlation between surface and the moisture distribution of the solid concerned, fast moisture analysis is possible by IR sensing. This principle fails at low moisture contents. In this cases, luminescence is more sensitive for moisture content determination. The quantitative analysis of ascorbic acid in liquids, fruits and vegetables is based upon the application of hybrid molecules consisting of a fluorescent chromophore and a nitroxide radical. The nitroxide is a strong quencher of fluorescence of the chromophore fragment. Reduction of the nitroxide results in enhancement of chromophore fluorescence and in decrease of EPR signal. Fluorophore-nitroxide probes react with ascorbic acid. The rate constant of this reduction is proportional to the concentration of ascorbic acid. Therefore, the vitamin C content can be determined by luminescence technique.