Antioxidant, physical, and flow properties of dried date paste (Phoenix dactylifera L.) determined using a hybrid convection infrared dryer

Abstract

Dates are difficult to dry into a powdered material with a specific degree of caramelization. Thus, the evaluation of (IR) drying was performed for various IR intensities (0.076, 0.152, and 0.228 Wcm−2), airflow velocities (0.5, 1.0, and 1.5 m/s), and maltodextrin concentration (MD) (0 %, 20 %, 40 %) on the qualitative properties of ‘Sukkari’ cv. date paste. Data analysis revealed that the shortest drying time was obtained at 0.5 m/s air velocity, which approximated 25–95 min by decreasing the IR intensity from 0.228 W/m2 to 0.076 W/m2 at MD of 40 %. Lower IR intensity at high air velocity and MD% resulted in a higher lightness (L) (82.68), lower visible color change (ΔE) (25.15) from medium light to light red (a) (4.78), and yellowness (b) value of 25.84. However, the bulk density of dried date samples did not significantly change under different operation conditions (0.64–0.77 g/cm3). Flowability properties showed the lowest Hausner’s ratio and cohesion index ranged (0.22–2.53 and 2.89–10.13), respectively, at 1.5 m/s and 40 % MD. However, the sample dried at higher IR intensity levels with 0.5 m/s air velocity and 0 % MD concentration had higher antioxidant properties, viz., phenolic content (14.35 mg GAE/g WD) and DPPH inhibition (63.20 %). The results showed that the infrared drying condition significantly affected numerous quality parameters, and the optimal drying condition for color and flow properties of the Sukkari cultivar is 0.0.076 W/cm2 and 1.5 m/s with 40 % maltodextrin; however, for antioxidant activity is 0.228 W/cm2 and 0.5 m/s without maltodextrin which is suitable for storage powder.