Water absorption, texture, and color kinetics of air-dried chestnuts during rehydration

Rectangular prisms of chestnuts (dimensions 10 x 10 x 15 mm) previously dried at 65 degrees C were rehydrated at different moisture contents (0.15, 0.24, 0.33, and 0.66 kg water/kg d.b.) by immersion in water during different periods of time (up to 180 min) and temperatures (25, 45, 70, and 100 degrees C). Rehydration kinetics were monitored by measuring their weights at regular intervals and were characterized using several rehydration indexes such as dry basis holding capacity (DHC), water absorption capacity (WAC), and rehydration ability (RA). Simultaneously, other properties that determine quality such as volume recovery, texture (by means of compression tests), and color during rehydration were experimentally determined. Peleg's model was successfully applied to experimental data and the corresponding parameters were obtained and correlated with temperature. Leaching flow was important only at high temperatures and dried samples at low moisture content gave satisfactory results for rehydration indexes. Texture kinetics was satisfactorily described by means of second-order kinetic model and the corresponding constant rate showed an Arrhenius relationship with temperature. Color was not recovered during rehydration. The results indicate that the use of low temperatures is more than adequate for preserving this property. Globally, during rehydration, chestnut showed acceptable rehydration rates taking into account the low porosity of the product, but rehydrated samples were softer and darker than fresh samples. Low-temperature rehydration and high initial moisture content of sample give better global properties for the rehydrated product. (C) 2007 Elsevier Ltd. All rights reserved.