title: Effect of the electric field frequency on ascorbic acid degradation during thermal treatment by ohmic heating.
abstract: In this work, the influence of the electric field frequency and solids content on the degradation kinetics of ascorbic acid during ohmic heating of acerola pulp and acerola serum was investigated. The degradation percentage of ascorbic acid in the pulp after 120 min of heating varied between 12 and 17%. For the serum, the degradation percentage was in the range of 13 and 18%. The results were fitted to the first-order model, and the kinetic rate constants ranged from 1.1 to 1.6×10(-3) min(-1) and from 1.1 to 1.5×10(-3) min(-1) for pulp and serum, respectively. D values ranged between 1480 and 2145 min for the pulp and between 1524 and 1951 min for the serum. A distinct behavior between the kinetic parameters of the pulp and serum in electric field frequencies ranging from 10 to 1000 Hz indicates that the presence of distinct amounts and types of solids might affect the rate of the electron transfer in electrochemical reactions. These variables may also affect the polarization process stimulated by the oscillating electric field. The non-achievement of the equilibrium of the polarization process may have an influence on oxidation reactions, affecting the predisposition to hydrogen donation from the ascorbic acid molecule.
authors.affiliation: Chemical Engineering Department, Federal University of Rio Grande do Sul , Rua Engenheiro Luiz Englert s/n, Porto Alegre, Rio Grande do Sul 90040-040, Brazil.
authors.forename: Giovana Domeneghini
authors.initials: GD
authors.lastname: Mercali
authors.forename: Steven
authors.initials: S
authors.lastname: Schwartz
authors.forename: Ligia Damasceno Ferreira
authors.initials: LD
authors.lastname: Marczak
authors.forename: Isabel Cristina
authors.initials: IC
authors.lastname: Tessaro
authors.forename: Sudhir
authors.initials: S
authors.lastname: Sastry
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D003296:Cooking / Q000295:instrumentation / Q000379:methods*; D006358:Hot Temperature; D007700:Kinetics; D029581:Malpighiaceae / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*
chemical_list: D010936:Plant Extracts; D001205:Ascorbic Acid