Fluorescence indices for monitoring the ripening of tomatoes in pre- and postharvest phases

Abstract

Greenhouse and climate chamber experiments were carried out to evaluate the ability of a portable multiparametric fluorescence sensor to monitor the ripening of tomato fruits (cultivar Cappricia) in pre- and postharvest phases. Fluorescence recordings were validated against established non-invasive optical methods based on reflection and remittance and against a visual colour classification scheme. Fruit ripening, as influenced by water supply (pre-harvest) and light quality (postharvest), was monitored by chlorophyll fluorescence indices (red and far-red fluorescence) after red and UV, red and green, or green and UV excitation. Chlorophyll breakdown was indicated by the fluorescence index NBI_R, which showed a negative and strong correlation with the reflection index a*/b* (R2=−0.798) and the remittance based stage-index (R2=−0.754). Characteristic curve patterns of the indices NBI_G, FLAV and Anth_RG enabled the pink (NBI_G, FLAV) and light red (Anth_RG) ripening stages to be defined and were well suited to detecting time-shifts in the ripening process. The potential of this technique for improved ripening monitoring and quality attribute determination in tomatoes is discussed.