Changes in the quality of dehydrated broccoli stems during storage

Dehydrated broccoli stems were studied during storage at different temperat ures, namely 5, 15, 25 and 40 degrees C. The parameters studied were rehydr ation capacity, texture of the rehydrated product and chlorophyll content. A diffusional model was used to study the rehydration process, yielding goo d agreement with the experimental data when the equilibrium moisture and th e effective diffusivity were identified. Samples stored at 5 degrees C show ed little change in any of the parameters studied during the storage time c onsidered (427 days). At 15 and 25 degrees C the equilibrium moisture and t he effective diffusivity varied linearly. At 40 degrees C, sharp changes we re observed up to 115 days, the equilibrium moisture decreasing and the eff ective diffusivity increasing. From this time on, both values showed modera te changes. With reference to texture, samples stored at 5, 15 and 25 degre es C showed a similar trend without significant changes during the whole pe riod, the textural values increasing with temperature. At 40 degrees C the texture suffered a sharp increase up to 145 days, then changes were negligi ble. Chlorophyll content degradation was increased with temperature. As a r esult of a calorimetric study a second-order transition was observed at 34 +/- 1 degrees C. This fact can contribute to the interpretation of the diff erent tendencies observed in all the parameters studied at 40 degrees C. (C ) 2000 Society of Chemical Industry.