Abstract
The effect of dried apple varieties on their rehydration characteristics was investigated. Four varieties of apples, Champion, Cortland, Grey Reinette and Ligol, were taken into consideration. Rehydration properties and color of apples were investigated. In order to examine the influence of apple variety on its rehydration properties, the process of rehydration was modeled. The model parameters obtained for investigated apple varieties were compared. Apple cubes were dried in a tunnel dryer (air temperature 60 °C and air velocity 2 m/s) and next rehydrated in distilled water at temperature: 20, 45 and 70 °C. Mass, dry matter mass, volume and color attributes of apples (raw, dried and rehydrated) were measured. The process of rehydration was modeled using empirical (Peleg and Weibull models) and theoretical (the Fick’s second law) models. Results of the analysis showed that the apple variety affects values of mass and volume increase, dry matter decrease and color of the rehydrated apple. Discussed parameters were also affected by rehydration temperature. Fick’s second law model can be considered as the most appropriate. Apple variety and rehydration temperature influenced the values of the model’s constants. Obtained values enabled attempts of the explanation of the rehydration course. It can be stated that apple var. Champion showed a greater rate of water absorption during the entire process of rehydration than other investigated varieties.
Highlights
Rehydration belongs to one of the most significant quality properties of dehydrated foods.The quick and complete process of rehydration can lead to a reduction of labor costs and floor-space requirements and, very importantly, to improving the efficiency of production [1]
The highest value, 52.93 g, demonstrated Cortland variety rehydrated at 20 ◦ C, the lowest 39.13 g Ligol one at 20 ◦ C
The results suggest that the rate of water absorption during the early stage of the rehydration at 20 ◦ C was the highest for Champion and the lowest for Cortland (Figure 1a) and, the discussed rate became higher at a higher temperature of rehydration
Summary
Rehydration belongs to one of the most significant quality properties of dehydrated foods. The quick and complete process of rehydration can lead to a reduction of labor costs and floor-space requirements and, very importantly, to improving the efficiency of production [1]. Some of the dried food products are consumed after their rehydrating (in milk or fruit juices). A better understanding of the discussed process can cause the quality improvement of both dried and rehydrated products [2,3]. Rehydration is a complex process intended to restore the properties of the raw food product by contacting the dried product with liquid [4]. The kinetics of the mass transfer mechanisms depends on the rehydrating liquid [5,6]
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