Softening of Overdried ‘Deglet Nour’ Dates to Obtain High-Standard Fruits: Impact of Rehydration and Drying Processes on Quality Criteria

Abstract

The postharvest hydrothermal treatment of date palm fruit was studied in order to enhance the quality and consumer acceptance of ‘Deglet Nour’ hard dates, because these dates are unfit for direct consumption. Hot water hydration was performed by soaking at 25, 45, and 65°C and convective hot air drying at 35, 45, 60, 75, and 85°C at various levels of air humidity. Numerous quality parameters—i.e., texture, color, moisture and sugar contents—were investigated. Artificial maturation due to the softening of texture and the equilibration of sugars was achieved using the hydration pretreatment. A 6-h soaking at 45°C could be the best option to obtain a product of highest quality, but the moisture content would exceed that required for safe storage. Drying and quality tests led to the selection of a pretreatment step of soaking at 30°C for 8 h, followed by drying at an intermediate temperature (60°C) as the optimum condition to obtain a final product of high quality with the standard moisture content of 0.35 kg/kg d.b.

Keywords:

• Color
• Postharvest treatments
• Soaking
• Sugars
• Texture

Notes

^a Ambient air humidity at about 10 g/kg⁻¹ dry air.