The influence of blanching pretreatments on the quality of dehydrated broccoli stems/ Influencia del tipo de escaldado en la calidad de tallos de bróculi deshidratados

Different blanching treatments were applied to sliced broccoli stems prior to dehydration in order to improve product quality. The pretreatments used were a conventional blanching in water at 100°C, and a stepwise blanching using different temperatures for the first step (50, 55, 60, 65 and 70°C). Five rehydration temperatures were used (25, 40, 55, 65 and 80 °C). Rehydration rate, chlorophyll content and texture of the rehydrated product were evaluated. Rehydration was modeled based on Fick's diffusion equation. A good agreement between the model and the experimental data was obtained when D _eff and W _e values were identified for each temperature (average percent variation 99.3). Samples stepwise blanched at 60 °C showed, on average, the lowest W _e and E_a values. Stepwise blanching at 60 and 65 °C and rehydration at 25, 40 and 55 °C were the combinations that gave the firmest product. Stepwise blanching at 50 °C and rehydration between 25 and 65 °C was the combination that preserved the highest chlorophyll content. From these results, it seems difficult to obtain firm samples with high chlorophyll content without any chemical additive.