Structural and physical properties of dried Anaheim chilli peppers modified by low-temperature blanching

The effect of low-temperature blanching and drying processes on the ultrastructural and physical properties of Anaheim chilli pepper was studied and optimum conditions to provide a final product with maximum firmness were determined. Lots of Anaheim pepper were blanched in water for 4 min at 48, 55, 65, 75 and 82degreesC and maintained for hold times of 35, 45, 60, 75 and 85 min, blanched again for 4 min at 96degreesC and dehydrated at 53, 60, 70, 80 and 87degreesC. After treatment the samples were rehydrated in water at 30degreesC. Rehydration ratio, texture and structural changes were evaluated. Optimisation used a second-order rotatable central composite design. Texture and rehydration ratio were affected by blanching temperature and the interaction of blanching temperature with hold time (p less than or equal to 0.05); drying temperature did not show a significant effect. The best results, ie those which gave greatest firmness, were obtained by blanching at 64degreesC for 4 min, holding for 55 min after blanching, followed by a second blanching at 96degreesC for 4 min and then drying at 70degreesC. Evaluation of the rehydrated dried pepper by microscopy showed that low-temperature blanching close to the optimum conditions provided a protective effect in maintaining cell wall integrity. The results of processing increased firmness in the rehydrated product by a factor of 1.97. (C) 2003 Society of Chemical Industry.