Recommendations on harvesting time based on the changes of physico-chemical fruit parameters in cv. 'Mollar' pomegranate

Abstract

The development of any reliable maturity indices could be done by correlating changes in fruit physic-chemical attributes during maturation with optimum eating quality and postharvest storage performance of fruit. Pomegranate growers and the fruit industry are in pursuance of an objective and simple determination of pomegranate fruit maturity index. So, it is necessary to establish parameters for determinate the right harvesting time when fruits have reach commercial maturity index based on the available scientific information. The present study was carried out under the agro-ecological conditions of Alicante (Spain), during the late stages of fruit development and maturation pomegranate cv Nollar' from September 10th (at 100 days after full bloom, DAFB) to October 14th (134 DAFB). Physico-chemical parameters selected were soluble solids concentration (SSC), pH, acidity, maturity index (TSS/TA) and as color is an important factor affecting marketability and consumer preference of fruit, the peel and juice color (CIELab*). Twenty fruits samples were taken weekly for analysis. During this period, when fruits are ripening on the tree, total soluble solids (TSS), increased significantly from 14.9 to 17.8. The TSS content (increased mainly at first and last period and remained constant the rest). The pH of the juice increased with maturity, reaching a maximum value of 4.0- 4.3 at the full-ripe stage. Titratable acidity (TA), an important quality attribute of pomegranate juice, decreased from 0.27 to 0.21 %. The ratio TSS/TA varied considerably from 56 to 89. We observed no correlation between development of the color of peel and the color of arils, inside fruit. Whereas, the CIE a* (redness pigmentation) juice color had significant changes during the last week, a* value increased continuously in fruit skin during ripening, the luminosity (L*), * yellow values b* decreased concurrently. Based on the changes of these parameters during fruit development, we considered <0.25% TA of juice and Hue<50 peel color parameter as the most satisfactory maturity standards due to the fruits had optimum maturity and the quality also agreed with market and consumer acceptability. To facilitate this task a harvesting color chart is proposed.