COMPARATIVE STUDY ON THE USE OF A NON-DESTRUCTIVE OPTICAL SENSOR (MULTIPLEX3®) FOR THE MONITORING OF THE ANTHOCYANINS CONTENT IN RED BERRY FRUITS

The preliminary results of a comparative study on the determination of the anthocyanins content in red berry fruits by a portable fluorescence- based optical sensor (Multiplex 3®) are reported. Commercially available Multiplex 3® was used to measure the “Fluorescence Excitation Ratio Anthocyanin Relative Index” (FERARI index) in red plums (Prunus domestica, L., cv Nero Sardo, Dore A., Stanley) and red grapes (Vitis vinifera, L., cv Monica and Cagnulari). In both species the FERARI index was related to the total anthocyanins content, such variable was determined by UV-Vis spectrophotometry and was expressed as mg/100 g of peel of malvidin 3-glucoside, and as mg/100 g of peel of cyanidin 3-glucoside, for grapes and plums, respectively. A good correlation between fluorescence index and peel anthocyanins content in all the plum cultivars was observed. On the contrary, only for one grape cultivar (Cagnulari) was found a correlation. Moreover, FERARI index and anthocyanins content showed a linear relationship in plums, whereas it was logarithmic in grapes. Finally, the Multiplex 3® allowed to detect a larger range of anthocyanins content in plums than in grape. Preliminary results showed that the fluorimetric-based optical sensor Multiplex 3® can be an effective tool for monitoring anthocyanins content in the peel of red plums. Moreover, a marked difference in its use depending on the species observed.