NONDESTRUCTIVE ANALYSIS TO MONITOR POTATO QUALITY DURING COLD STORAGE

Samples of potatoes were harvested in 2007 in Friuli Venezia Giulia (Italy) and were stored at 6.5C for 6 months to assess quality characteristics, mainly related to the sprouting trend of tubers. The quality changes during cold storage were monitored using conventional measures (i.e., weight, visual appearance, morphological control, number and length of buds, degrees Brix) and nondestructive methods (fluorometry and colorimetry). Among 17 cultivars, seven were stored at a lower temperature (0C) for 4 months and then 10C for 15 days to verify the reversible interconversion between starch and sugar induced by the storage temperature. The most important results were given by fluorometric analysis, which provided useful information for predicting the sprouting trend of tubers, as well as other objective analytical tests: the quantum yield had in most cultivars the minimum value in predicting sprouting time. After the low-temperature storage, the quantum yield was irreversibly reduced. Practical Applications Nondestructive techniques based on chlorophyll fluorescence measurements are used to monitor quality changes during post harvest storage of fruit and vegetables. Fluorometric values give indications not only about the chlorophyll amount, but also on the physiological state of photosynthetic apparatus. Even if potato tubers in good storage conditions don't produce chlorophyll, they possess a photosynthetic apparatus whose physiological state can be measured by fluorometry. Potatoes stored at low temperatures are subject to the sweetening process, but starch is synthesized again when potatoes are transferred to normal temperatures. The photosynthetic apparatus is damaged by low temperatures, as indicated by the decrease of fluorometric values, and this process is not reversible. The fluorometric indexes can be measured in order to check if potatoes were properly stored and evaluate differences of behavior in storage. The nondestructive method will enhance monitoring of potatoes quality during storage, thus minimizing both time and food wastages.