Effects of Harvest Time and Storage Duration on Some Physical and Biochemical Indices in Pomegranate (Punica granatum L.) Fruits

Background and Objectives Preharvest and harvest conditions can affect quality and biochemical composition of fruit during storage. Pomegranate (Punica granatum L.) is a non-climactric fruit and there is no clear physiological index to determine the proper harvest time. Lack of standard maturity index results in prolonged period of picking pomegranate fruit within the season. The effects of different physical or chemical treatments on postharvest quality of pomegranate fruit have been investigated in many studies, but our knowledge on the pre-harvest and harvest aspects that influence pomegranate fruit postharvest physiology is scarce. The objective of the present experiment was to determine how qualitative indices of pomegranate fruit in ‘Bagmalek’ (Khuzestan, southwest of Iran) are affected by maturity stages at harvest and storage duration.
Materials and Methods A factorial design including three harvesting times and three storage durations with three replications was used for statistical analysis. Fruits of ‘Malas Post Zard’ as an important pomegranate cultivar were harvested from a commercial orchard in ‘Bagmalek’ (150 Km Ahwaz, Khuzestan, southwest of Iran). Fruits were harvested at three harvest times at 14-day intervals (14 September, 29 September and 13 October 2011) and stored for 40 and 80 days at oC. Some physical (weight, surface color, decay and shriveling) and biochemical characteristics (ascorbic acid, total soluble solids, titratable acidity, pH, anthocyanin index and browning index) were evaluated. The factors were evaluated at harvest time and after 40 and 80 days.
Results Regardless of storage durations, pomegranate fruit showed significant variations in total soluble solids, titratable acidity, pH and anthocyanins. Interactions of the harvest time and storage duration (for 40 and 80 days) were significant on gravity, surface color changes, shriveling, ascorbic, acid, pH, titratable acidity and fruit juice pigments (anthocyanin index and browning index). Results showed that the period 29 September until 13 October 2011 and storage duration for 40 days are the best treatments to maintaining postharvest quality of ‘Malas Post Zard’ fruits in ‘Bagmalek’ (Khuzestan, Iran).
Discussion Results showed that quantity and quality indices of the pomegranate could be improved through the selection of proper harvesting time. Harvest of pomegranate fruit at different maturity stages altered fruit appearance quality indices and biochemical characteristics under ‘Bagmalek’ geographic condition, and at early harvest time (14 September), it reduced fruit quality but did not make its consumption unacceptable. More research needs to assess the effect of different climatic parameters such as temperature and light intensity on the postharvest quality of pomegranate fruits in Khuzestan.