Influence of Drying Procedure on Colour and Rehydration Characteristic of Wild Asparagus

The objective of this research was to examine the influence of different drying procedures on the colour quality and rehydration capacity of wild asparagus (Asparagus maritimus L.). Wild asparagus samples were dried using convective (40 degrees C, 50 degrees C, 60 degrees C, and 70 degrees C at the airflow velocity of 2.75 m/s), natural, and freeze (-20 degrees C and -40 degrees C) drying procedures. Rehydration and colour characteristics were used as indicators of the quality of the dried asparagus samples. Convective drying of asparagus resulted in the smallest colour change of the fresh material, whereby drying at 60 degrees C presented the optimum. The best rehydration ratio was achieved when the samples were freeze dried at -40 degrees C. Naturally dried asparagus samples resulted in a very low rehydration ratio compared to the other procedures investigated. The rehydration and appearance of the dried asparagus are two important physical factors that need special attention when designing or selecting a drying procedure. Furthermore, the influence of drying on other quality characteristics of wild asparagus, such as the content of active ingredients or microbial count, should be investigated in further studies. The investigation of economic parameters of different drying procedures should be considered as well.