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Effect of Dehydration on the Physiological Activity and the Quality of Carrot
Drying as a method of food preservation causes many physical, chemical, and biochemical changes in processed materials. Effects of these changes are dependent on predrying treatments, drying methods and parameters as well as rehydration procedures. Considering drying as a method of preservation it is worth noting that some dehydration methods are aimed at obtaining materials with uninjured biochemical pathways, while others lead to products in which the viability of cells is not an important issue. Drying of seed grain, powder starters or active baker’s yeast are the examples of those drying processes in which preservation of viability of cells and undamaged biochemical activity are the aims of the process. On the other hand, drying of fruits, vegetables, meat, eggs is undertaken in order to obtain shelf-stable products with preserved sensory and nutritional attributes. Moreover, observing changes of respiratory activity can roughly understand the activity of tissue cells. The aim of this study was to observe changes of respiratory activity of cube carrot tissue subjected to different drying ways and subsequent rehydration. In this work, respiration of carrot tissue was measured in the fresh state and at different degrees of dryness after treated with different drying methods. Moreover, respiration of rehydration samples was measured. Measurement of water holding capacity, firmness and scanning electron microscopic examination can further understand the relationship between structural damages and respiratory activity.
Results showed that dehydration of carrot tissue caused substantial changes in cell structure and organization. It was manifested by a decrease in respiration activity. Most of the injury to tissue structure and respiration pathways was done at the initial stages of drying. Freeze drying caused less and tender damage to the structural and respiratory activity of carrot samples. In freeze drying, lower pre-freezing temperature and shorter pre-freezing time would make carrot tissue have higher respiratory activity after rehydration. Osmotic dewatering also affected respiration of carrot tissue but the mechanism of injury seemed different from that occurring during convective drying and freeze drying. After osmotic treatment, the dried carrot would possess higher respiratory activity after rehydration. Moreover, the results of water holding capacity, firmness, and scanning electron microscopic examination were similar to the results of respiratory activity experiment.
|Appears in Collections:||食品暨應用生物科技學系|
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