Abstract
‘Piarom’ date (Phoenix dactylifera) is one of the semi-arid and commercially important cultivars in Iran. In Ahvaz region of Iran, most of the date cultivars, including ‘Piarom’, turn sour and fall prematurely, during the rutab stage, due to high moisture content, leading to a major yield reduction. Therefore, the purpose of this study was to investigate different methods of artificial ripening of ‘Piarom’ dates in the khalal and rutab stages. The treatments included immersing the ‘Piarom’ fruit in acetic acid (1% and 2%) and NaCl (1%and 2%) solutions and freezing treatments for three times of 24, 48, and 72 hours. Harvesting of Khalal was done at three different times from the beginning of Khalal stage and once every two weeks. Fruit receiving an acidic acid application at 2% in all immersion and harvest treatments had the highest speed and percentage of transformation of khalal to rutab. Crop with a 2% acidic acid immersing treatment at the first and third harvests had the highest desirable fruit-finish. The highest percentage of desirable dates in the first and second harvests was related to 72- and 24-hours freezing treatments, respectively. By delaying the harvesting time, the moisture content of the khalals decreased significantly. The moisture content percentage of fruit obtained from chemical and physical treatments was higher than that of natural dates. There was no significant difference among different harvesting times regarding soluble solids concentration (SSC), titratable acidity (TA) and percentage of reducing sugar of khalal fruit. In general, the SSC of artificially ripened fruit was lower than that of natural ‘Piarom’ dates. During all three harvest times, the TA level of date fruit obtained from chemical treatments was significantly affected by the treatments. In all three harvests, there was no significant difference among chemical treatments regarding of reducing sugars percentage. In all three harvests, the reducing sugar content of frozen fruit was lower than that of natural dates. According to the study, acetic acid at 2% was more successful than other treatments if it did not have a bad effect on the taste and aroma of the fruit. Thus, we suggest that the impact of other acid-containing compounds, but without the poor taste of acidic acid, such as acid extracts from other fruit be experimented for the ripening of ‘Piarom’ date in the future.