Prediction of Optimum Humidity Condition for Storage of Some Egyptian Dry Fruits and its Effect on Physical Properties of Fruits

Elbaz, Abeir M. F.; El-Kady, Amgad A. M.; Mohamed, Entsar Noureldin

doi:10.21608/ejchem.2025.345508.11009

Prediction of Optimum Humidity Condition for Storage of Some Egyptian Dry Fruits and its Effect on Physical Properties of Fruits

Document Type : Original Article

Authors

Food Engineering and Packaging Department, Food Technology Research Institute, Agriculture Research Center, 12613 Giza, Egypt

10.21608/ejchem.2025.345508.11009

Abstract

This work aimed to establish sorption isotherms curves for the dry fruits of apricots, raisins and Saidi dates and their relationship to the expected shelf life, color and hardness of the tested fruits. Results showed that the ob-tained sorption curves are of sigmoidal shape and that content and type of sugars in the fruits is crucial for the level of equilibrium moisture content (Me) at water activity level of 0.11 to 0.85 at 25±5℃, whereby sucrose rich fruits (apricots) recorded Me – values lower than those of high levels in reducing sugars (raisins and Saidi dates). GAB and Halsey isotherms equations were suitable for presenting sorption curves of raisins and dates (Relative deviation percent” P” <10%), while Henderson – equation gave a high R2 – value of 0.93 for apricot, s sorption data but with patterned residual (P%). Monolayer moisture content Mm was in the range of 0.0547 (apricots) and 0.119 to 0.147 g H2O/ gDM for raisins and dates. Expected shelf life of the tested dry fruits was estimated from the slope of multilayer portion of the sorption curves to be 7.16 to 7.40 months at 25℃ and 70% relative humidity in the surrounding atmosphere outside a polyethylene package containing the dried fruits and it could be extended to 10-11 months if surrounding relative humidity maintained at 50% level. At water activity levels 0.11 and 0.22, the fruits showed high hardness values of 1738 to 1412 N/m2 for dry apricots and raisins, while dates showed values of 198 to 84 N/m2 . Increasing aw – level to 0.85 drastically reduced hardness values. L, b, chroma and Hue◦- values of the dried fruits were decreased by increasing aw – level from 0.11 to 0.85, while red-ness (a-values) were increased. Browning reached a maximum at o.7 to 0.75 aw – level and decreased at lower aw – values.

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