An attempt to the nondestructive investigation of photo-induced potato postharvest quality degradation – Preliminary results

Abstract

Among improper harvest and/or postharvest storage conditions, the effect of direct sunlight plays an important role in quality degradation of potato resulting in the development of green surface color based on chlorophyll formation associated with the formation of poisonous chemicals – glycoalcaloids – known as a -chaconine and a -solanine. Yellow skinned and fleshed potatoes with or without visible initial marks of green surface color were stored at normal room temperature under direct natural (sun)light conditions for almost two months. The aim of this study was the preliminary investigation of the sunlight induced formation of chlorophyll related compounds in potato indirectly by the detection of chlorophyll development. This attempt was based on nondestructive determination of chlorophyll related spectral and fluorescence indices for both sunlight exposed and unexposed potato sides. For both potato groups the chlorophyll content related DA-index ® and chlorophyll fluorescence characteristics (F 0 , F m , F v and F v /F m ) increased during the storage period representing chlorophyll formation. In the case of F m , F v and F v /F m values, the yellow samples reached the values of the initial spotted green samples by the 7 th – 9 th days. From this time, the chlorophyll fl uorescence values changed only minimally. After storage day 34, in the case of both at day 0 yellow and green spotted potatoes, the sunny side ’ s F 0 value was lower than that of shaded side. Close relationship was found between the results of Walz monitoring-PAM (Pulse Amplitude-Modulated) chlorophyll fl uorometer and the PSI (Photon Systems Instruments) chlorophyll fl uorescence imaging device (e.g. F v R 2 5 0.7226). According to our preliminary results, the Vis/NIR DA-meter ® , the monitoring-PAM and the chlorophyll fl uorescence imaging fl uorometers were found to be suitable nondestructive devices for further investigations concerning the postharvest chlorophyll formation based greening phenomena, which is associated with solanine development in potato.