the influence of opportune harvesting on the fruit quality of pomegranate cvs. shekar, shirin and sangak

background and objectives: pomegranate, belonging to punicaceae family, is native of subtropical regions of iran and its neighborhood countries. iran has the richest germplasm resource of pomegranate and the first grade in cultivation area and production worldwide. physical and chemical properties of pomegranate cultivars vary in different developmental stages and have a large impact on the nutritional values of the fruit. these attributes have not been evaluated yet in details in iranian pomegranate cultivars during maturation stages. this study aimed to investigate the influence of harvesting time on fruit quality in three pomegranate cultivars.materials and methods: in this experiment, three native pomegranate cultivars of kolbad region, located between province golestan and province mazandaran, including shekar, shirin and sangak, were studied at two stages of the fruit maturation, including the early harvest (early days of traditional harvesting season on 20/6/91) and opportune harvest (last days of traditional harvesting season on 20/8/91). the experiment was conducted in a factorial design in three replication. in each replication, four fruits were used to measure some physiochemical traits. the analysis of variance was done using sas version 9.1 and the means were compared using lsd. results: the results showed that there were some significant differences in physicochemical attributes between these two harvesting times and among the three cultivars. in all cultivars, most of the physical properties were highest in the opportune harvest, except for the thickness and the percent of the fruit peel. among the cultivars, shekar had heavier and larger fruits. in contrast, shirin had heavier and larger arils. shekar had the highest percent of fruit juice, while there was no difference between shirin and sangak. the results showed that there was not any significant difference between the harvesting times and among the cultivars in fruit crown length and fruit density. in all cultivars, ph, total soluble solids, total phenol, total antocyanin, and total sugar were highest in the opportune harvest, while ec (electrical conductivity), titratable acidity, and vitamin c were lowest. shekar had the highest fructose and vitamin c; while shirin had the highest glucose and antioxidant activity. conclusion: in general, the results showed that from early harvesting time to opportune harvesting time most of the physical and chemical characteristics were changed in fruits of the studied cultivars. opportune harvest may highly improve the nutritional values of pomegranate fruits; therefore, in this part of the country and other parts the pomegranate fruits must be harvested in the correct time.