Evaluation of Relationship between Moisture Loss in Grapes and Chlorophyll Fluorescence Measured as F0 (F-α) Reading

Chlorophyll fluorescence was studied as a rapid technique to detect weight loss of table grape cultivars "Thompson and Flame seedless" under air storage conditions (20°C) and in a 0ºC cold room. Grape clumps (ca. 1kg) were divided into 12 groups (six for each cul-tivar) and initial fresh weight, soluble solid content, titratable acidity, pH and color values were recorded. Three groups were placed inside ventilated baskets with a HarvestWatch sensor facing down on the grapes and placed in a 20ºC room in front of a forced air fan. These samples were used to generate continuous recording of F-α. The other groups were handled in a similar manner and were used to generate weight loss. The control treat-ments were held in a 0ºC cold room and constantly measured by a HarvestWatch sensor. F-α (F0) ratio curve for Thompson generally declined over times, and the rate of reduction was maximal between days 1 and 6 which is equal to ca. 20 percent in weight loss. The re-sponse for Flame grapes was almost the same as for the Thompson cultivar. There were good relationships between F-α values and weight loss values for both cultivars. From these relationships it appears that, for both cultivars, at about 20% weight loss (equal to 0.8 weight loss ratio), the F-α value stopped its decline. The other fruit quality such as SSC, TA, pH and color value indicated that the drying treatment affected these responses, compared with the fruit in the control treatment. Our results indicated that chlorophyll fluorescence techniques can detect weight loss in grapes after harvest, and thus has a po-tential as a rapid and non-destructive method for monitoring fruit weight loss and senes-cence in grape during storage.