HTST puffing in order to produce crispy banana - The effect of the step-down treatment prior to air-drying

Banana snacks were produced by HTST puffing. Experiments were performed as follows: an initial pulse at 150 °C for 15 min + step-down treatment from 150 to 70 °C + air-drying at 70 °C. The aim of this work was to study the effect of this step-down treatment on banana snack attributes: crispness, shrinkage, color and structural morphology. Two variables were evaluated. The first was the magnitude of temperature reduction, named as amplitude. The second was the residence time at this temperature, named as cycle time. Results showed that an amplitude of 10 °C and cycle time of 7.5 or 10 min, lead to a gradual reduction of temperature. Banana snacks from these step-down treatments resulted in a highly porous structure, higher number of peaks in the force-deformation curve (an indicative parameter of crispness), less volume loss and, less color degradation. Thus, these treatments were shown to be an adequate alternative in relation to the conditions with the sudden reduction of temperature.