胡萝卜丁中维生素C在热风辅助射频干燥过程中降解的动力学模型

Mathematical modeling of vitamin C thermal degradation kinetics in carrot cubes during hot air-assisted radio frequency drying

中文关键词:  射频  动力学  脱氢抗坏血酸  抗坏血酸  活化能

英文关键词:radio frequency  kinetics  dehydroascorbic acid  ascorbic acid  activation energy

中文摘要:

      目的 研究热风辅助射频(hot air-assisted radio frequency, HA-RF)干燥过程中维生素C随温度变化的降解动力学模型。方法 在6.5 cm极板间距和60 ℃热风系统条件下进行HA-RF干燥, 重点研究胡萝卜丁中维生素C在干燥过程中的降解动力学, 包括脱氢抗坏血酸(dehydroascorbic acid, DHAA)和抗坏血酸(ascorbic acid, AA)。总维生素C含量采用2,4-硝基苯肼分光光度法测定, AA采用2,6-二氯吲哚酚滴定法测定。结果 HA-RF干燥过程中维生素C的降解规律符合一级可逆模型, 其降解活化能为40.54 kJ/mol。DHAA活化能为35.83 kJ/mol, 表明DHAA的稳定性低于AA。结论 本研究使用的干燥温度为62.5~77.5 ℃, 较高的干燥温度下维生素C降解速率较高, 较低处理温度下的降解过程具有更好的模型适应度(R2>0.98)。

英文摘要:

      Objective To study the degradation kinetic model of vitamin C with temperature changes during the hot air-assisted radio frequency (HA-RF) drying process. Methods HA-RF drying was carried out under the conditions of 6.5 cm plate spacing and 60 ℃ hot air system, focusing on the degradation kinetics of vitamin C in carrots during the drying process, including dehydroascorbic acid (DHAA) and ascorbic acid(AA). Total vitamin C content was determined by 2,4-nitrophenylhydrazine spectrophotography method and AA was assayed by 2,6-dichloroindophenol titrimetric method. Results The degradation of vitamin C during HA-RF drying was in accordance with the first-order reversible model, the degradation with activation energy of 40.54 kJ/mol. Besides, the activation energy of DHAA was 35.83 kJ/mol which indicated that DHAA had lower stability compared with AA. Conclusion The drying temperature used in this study was 62.5?77.5 ℃. The degradation rate of vitamin C is higher at higher drying temperature, and the degradation process at lower treatment temperature has better model fitness (R2>0.98).