Evaluation of the Index of Absorbance Difference (IAD) to Determine Optimal Harvest Time of Peach Fruit

Establishing the optimal harvest time is critical in peach production. Since fruit shelf-life potential and quality are closely related to the ripening stage at harvest, determining the right time for harvesting peaches is of utmost importance to everyone in the fruit growing and distribution chain: growers, distributors and consumers. The predominant way to establish optimal harvest time is by fruit size and ground color development which can vary from year to year and does not always coincide with best fruit quality. A newly developed, non-destructive device that estimates fruit ripeness by measuring chlorophyll content (I_AD index) in the fruit, shows promise for both applied and scientific applications. This tool makes it possible to accurately establish the optimal harvest time by monitoring fruit ripening on the tree, and consequently, to reduce the variability that is present in packinghouse fruit. In this research the I_AD device was evaluated for its usefulness to non-destructively determine optimal harvest time by comparing the measured I_AD index to standard fruit quality parameters such as fruit firmness, soluble solids content, and titratable acidity so to verify the accuracy of the I_AD to grade peach fruit into ripening classes, characterized by different shelf-life potential and consumer acceptance. During the 2009 and 2010 harvest seasons, 5 and 11 different peach cultivars, respectively, were analyzed for I_AD variability at harvest, and fruits were separated into three groups based on I_AD index where each I_AD fruit group has been further subjected to fruit quality testing. Data show there was variability of I_AD index between genotypes and among harvested fruit. Results of a blind consumer survey using fruit from two cultivars sorted by I_AD index revealed higher appreciation and willingness to pay for more ripe fruit, corresponding to the fruits in the lower IAD category. Broad application potential in fruit production and distribution as well as in scientific research will be discussed.