Relation between storage temperature and phenolic compounds in date fruits (Phoenix dactylifera L.)

The literature suggest that date palm cultivars are a promising source of beneficial compounds, of which many cultivars around the world are gaining increasing interest due to their important biological properties. Hence, there is a need to be further investigated in Algerian date palm cultivars. The purpose of this study was to identify the effect of the storage temperature variation on the content of phenolic compounds in dates for some Algerian cultivars (Deglet Nour, Ghars, Mech Degla, Degla Baidha). The fruits of the four cultivars were preserved in varying degrees of temperature (4°C and ambient temperature). To determine the effect of the varying degrees of storage temperature on the content of phenolic compounds, the total phenols, flavonoids and total tannins were measured. The differences were noted for the five studied parameters. We found that there was a storage temperature effect on the pH parameter with a value of 6.17 (±0.04), and low effect on electric conductivity. Determination of total polyphenols in dates shows high degrees in Degla Baidha cultivar stored at 4 °C (574.46 mg EAG/100 g) compared to those of Mech Degla, Ghars and Deglet Nour (564.46, 554.35 and 526.39 mg EAG/100 g respectively), and for the same cultivars stored in high temperature, the total polyphenols content was found lower. The total tannin and flavonoid content show a significant difference for date cultivars, where the best estimated levels of the two components in Degla Baidha cultivar at 4 °C (110.43 mg EAT/100 g and 4.51 mg QE/100 g respectively). The results revealed that there was insignificant effect of variation in storage temperatures on flavonoids and total tannins, but the effect was strong, with respect to total polyphenols. Considerable quantities of these compounds were recorded at a temperature of 4 °C. These findings reveal the richness of these Algerian cultivars in phenolic compounds compared to others.