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Microwave-Assisted Inactivation of Carbohydrases from Aspergillus niger by Continuous-flow Processing

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  076103.(doi:10.13031/2013.23327)
Authors:   Judith D Espinoza-Perez, Luz M Ramos-Ponce, Angel U Valdez-Peña, Ana C Saucedo-Suárez, Cecilia Balvantín-García, Dennis P Wiesenborn, Juan C Contreras-Esquivel
Keywords:   Inulinase, invertase, inulin, sucrose

Microwave energy has been widely applied in food processing as an alternative technology of pasteurization, such as to inactivate pectin-methylesterase in the production of orange juice and other citrus products. In this study, microwave irradiation in a continuous-flow reactor was used to evaluate enzyme inactivation. Fructozyme, a commercial enzyme preparation, was used as a model. The power and pressure applied were 800 W and 20 bar, respectively. The measured flow rate was 1.25 ml s -1. Samples were irradiated at different durations (5, 10, 15, 20, 30 and 35 min), and constant temperatures of 75, 100, 125 and 150 °C. Inulinase and invertase activities in the irradiated samples were evaluated by the reducing-sugars technique. The inactivation rate constants at the different temperatures were evaluated from a first-order equation by nonlinear regression. Inactivation energies for both enzymes were also calculated. Continuous microwave irradiation under the experimental conditions at 150 °C had a greater effect on the inulinase activity, with an inactivation rate constant of 0.45 min -1 compared with the inactivation rate constant of invertase, 0.21 min -1. Inactivation energies for inulinase and invertase were 22 and 13 kJ mol -1, respectively. The results showed that microwave-assisted processing under continuous-flow effectively inactivated inulinase and invertase.

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