In this study, different drying processes (hot‐air convective drying, microwave drying, ultrasonically assisted convective drying, freeze‐drying, and infrared drying) were applied to dry the eggplant slices. Therefore, the Newton (infrared drying), Page (hot‐air convective drying, freeze‐drying, and microwave drying), and modified Page (ultrasonically assisted convective drying) are the best models to describe the drying kinetics of eggplant slices. Furthermore, the effective moisture diffusivities (Deff) varied significantly from 1.16 × 10−10 (freeze‐drying) to 3.31 × 10−8 m2/s (microwave drying) (p < .05). Besides, the highest and lowest activation energy values were observed in the samples treated with freeze‐drying (38.80 kJ/mol) and ultrasonically assisted convective drying (23.87 kJ/mol), respectively. Moreover, the effect of the drying processes on the kinetic degradation and formation of bioactive compounds, HMF, enzymatic browning index, color parameters as well as on the antioxidant activity was investigated. Then, the Weibull model was proven be the best to better fit the polyphenols and flavonoids data.
Novelty impact statement
Five drying processes were applied to dry Tunisian eggplant slices.
The ascorbic acid, anthocyanin, polyphenol and flavonoid amounts were determined during the drying of Tunisian eggplant slices.
The freeze‐drying process was selected as the best method to preserve the dried eggplant.
This study investigated the physicochemical, rheological and textural properties of nine types of honey from different regions of southern Tunisia. Principal component and cluster analyses were used to classify the honeys into groups. The physicochemical results (water, proteins, total soluble solids, pH, free acidity, water activity, electrical conductivity, invertase activity, Hydroxymethylfurfural (HMF), vitamin C, lycopene and anthocyanins) were in accordance with those of the standards Established by the Codex Alimentarius. The invertase activity varied from 62.58 units/kg to 110.24 units/kg. The HMF values of the different types of honey ranged from 11.48 mg/kg in prickly pear honey to 25.56mg/kg in heather honey. Anthocyanin contents, lycopene and vitamin C contents ranged between 8.38 and 24.86 μg/L, 1.08 to 6.17 mg/kg and 30.71 to 129.38 mg/kg, respectively. The flow test confirmed the Newtonian behavior of all honeys, and their textural properties had very high extrusion forces varying from 113.50 g to 131.05 g. Cluster analysis (CA) and the biplot generated through PCA recognized four groups of honeys based on either the physicochemical parameters or textural attributes and only three groups based on color and sugar.
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