Effect of drying on respiration of apple slices

Apple tissue not pretreated before drying was subjected to convective drying and freeze-drying. Osmotic dewatering was also used as a method of water removal from the plant tissue. Respiration of apple tissue was measured in the fresh state and at different degrees of dryness. Moreover, respiration of rehydrated samples was measured. Respiration of apple tissue decreased with increasing dry matter content and at contents higher than 60% ceased completely. Rehydration led to some restoration of the respiratory activity. The degree of restoration was dependent on the amount of water removed during drying. Freeze-drying affected less respiration pathways in apple tissue than convective drying. Osmotic dewatering affected respiration in a different way than convective drying. During the initial stages of osmotic dewatering the respiration increased substantially due to the increase in substrate concentration. At later stages of osmotic treatment increased concentration of solubles and changes in cell structure caused a decrease of respiration. (C) 2001 Elsevier Science Ltd. All rights reserved.