The effect of harvest time on quality characteristics pistachios fruit during storage at freezing temperatures

Pistachio has many nutrients that changed in various stages of kernel development. Pistachio nut used dry normally because of the physical structure and the lack of appropriate methods for keeping fresh fruit and fresh consumption is limited to the harvest season. In this study, the changes in some qualitative indicators Ahmdaqaii pistachio in five stages of fruit development and its storage in five layers plastic bags on freezing temperature with vacuum conditions were studied.  The results showed the improvement of the nutritional value at ripening stage. The amount of fat (57.6%) and protein (23.5%) in the fourth stage and carbohydrates (14.22%) in the fifth stage of harvest were maximum. With kernel development, amount of unsaturated fatty acids, especially oleic acid (58.04%) was increased, whereas saturated fatty acids declined with maturity advancement (11.49%). Despite the amount of kernel calcium (149 mg/kg) and mesocarp (73 mg/kg), the kernel nitrogen (3.83%) and mesocarp (1.41%) was uptrend during development. The results of storage harvested pistachios at -18 °C indicated pistachio appearance characteristics, endocarp and kernel were not acceptability in first, second and third stage of harvest. But flavor and texture of kernel in this stage of harvest were better than forth stage of harvest. Although water loss and off flavor is one of the disadvantages of frost temperature, pistachios harvested in the fourth stage have final accept. According to the results, the fourth phase of harvest has the highest quality pistachio that coincides with the 70 percent of ripening. Therefore, we can suggest this stage of ripening for the best time to harvest and storage of Ahmadaqaii pistachio in Rafsanjan geographic area.