Abstract: Date palm fruits (Phoenix dactylfera L.) cv. Barhi and Medjool were harvested at the khalal stage at three different harvesting dates. Fruits were treated or not with 100% CO2 in 20 L air tight glass jars for one or two days. Results for gene expression involved in PAs biosynthesis (PAL, CHI and C4H) indicate that tannins synthesis is reduced in late stage of fruit development and at harvest. However, different CO2 durations treatments had significantly different effects on Barhe and Medjool fruits for final color index, firmness, acetaldehyde and ethanol. Whereas, Internal Ethylene Content (IEC) and total soluble solids were not significantly affected. In contrast, tannin content in date fruit decreased significantly under CO2 duration compared to the control which was pronounced on enhancement of Barhe fruit edibility compared to Medjool fruit, especially at the 48 h CO2 duration.