Optimization of Convective Dehydration of Beta vulgaris for Color Retention
2012
Gokhale, S. V. | Lele, S. S.
Beta vulgaris or beet root powder is a good natural food colorant since beet contains significant amount of red-colored betalain pigments. This paper reports the process optimization of drying conditions to get beet root powder with maximum retention of red color. Response surface method was used with three factors: five-level central composite design to arrive at optimum drying temperature, sample thickness, and hot air recirculation. Beet powder was evaluated to assess color retention with respect to fresh beet as a control. A 53 °C temperature and 7-mm thickness with 63% air recirculation ratio gave the best product, with 90% retention of red color having acceptable rehydration ratio and final moisture content. Using optimum sample thickness and air recirculation rate, drying process was further improved to reduce drying time and energy consumption. At different temperatures (50 to 120 °C), drying characteristics were studied. Thus, drying time of 6 h was further reduced to 4 h by applying sequential temperature gradient during drying (initial 120 °C gradually reduced to 53 °C) that also resulted in energy savings with the same degree of color retention.
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