Sorption isotherm properties of date (Majhoul variety)

Sorption isotherm properties of date (Majhoul variety).

problematic Materials and methods Results and discussions conclusion.

In the processing and storage of foods, the sorption isotherm of materials is very important, to protect their organoleptic and physicochemical quality though long storage . Morocco is a powerful producer of dates, which requires good storage to preserve its quality. The adsorption isotherms of dates is important in establishing date attitude during the storage ..

SORPTION ISOTHERMS Definition The aw activity of water in a product depends mainly on its water content X and its temperature T. The curve representing for a given temperature T the water content X of a product as a function of the value of water activity aw or the relative humidity of the air in equilibrium the water activity aw or the relative humidity of the air in equilibrium HR is called : Adsorption isotherm if it has been determined experimentally starting from a dry product. Desorption isotherm if it has been determined experimentally starting from a product saturated in water..

The dates ( Majhoul variety ) used in this work came from the Er-Rachidia province, the latter is considered among the noble dates of Morocco..

Concentration (%vol/vol) Température de la solution de l’air (C) 30C 40C 10 0.9427 0.9562 25 0.8736 0.8785 40 0.5656 0.5748 55 0.2605 0.2675 70 0.0453 0.0497 85 0.0018 0.0023.

method : The dates are cut into thin slices with a length of 2 cm and a thickness of 1 to 2 mm. The samples of about 30g are put in a previously weighed stainless steel capsule, the latter is put in a glass jar containing sulfuric acid with different concentrations ranging from 10% up to 85% to maintain the activity water . the glass jar is closed and placed in the oven ..

The curves of isotherms of adsorption in two temperatures (30C and 40) of the Moroccan dates variety MAJHOUL have a sigmoidal form of type II, this type is curve is known by the fruits rich in carbohydrates. Water adsorption is important when water activity is highest. At low water activities the adsorption is also low. This is noticed for both temperatures (30C and 40)..

30 °C 0.94269999999999998 0.87360000000000004 0.56559999999999999 0.26050000000000001 4.53E-2 1.8E-3 46.4 14.7 5.7 3.5 3.4 40°C 0.95620000000000005 0.87849999999999995 0.57479999999999998 0.26750000000000002 4.9700000000000001E-2 2.3E-3 51.2 15.1 6 2.2999999999999998 2.1 2.2000000000000002.

Conclusion. For the two temperature values of 30°C and 40°C, the water content varies similarly to the water activity . The experimental results obtained allowed us to : Describe the behavior of dates according to humidity and temperature Determine the parameters of the mathematical models used for the adjustment of the isotherms Determine the content of the monomolecular layer for the good conservation of MAJHOUL variety dates.

Merci pour votre attention.

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