红枣干制过程中Vc含量测定分析

Analysis of the Content of Vitamin C in the Dying Process of Red Jujube

[目的]测定不同干燥方法处理红枣的Vc含量。[方法]分别采用自然晒干、微波干燥、电热恒温干燥的方法处理样品,用草酸提取各样品中Vc,37℃时与2,4-二硝基苯肼反应,用分光光度方法于波长490 nm处测定吸光度。[结果]鲜枣中含Vc 324.64 mg/100 g,随着自然日晒天数的增多Vc含量迅速减少;电热恒温干燥的样品Vc含量21.63 mg/100 g;微波干燥样品Vc含量93.25 mg/100 g。微波干燥处理的红枣Vc含量显著高于自然晒制20 d和电热恒温干燥的样品。自然干燥过程中前7 d果实Vc含量下降幅度较小,8 d后果实Vc含量显著下降,约2周后果实Vc的含量变化不大。[结论]3种红枣干制方法中,以微波干燥处理的红枣Vc含量最高。

[Objective] The research aimed to determine the content of Vitamin C in red jujube treated by different drying methods.[Method] The samples were treated by the methods of natural drying,microwave drying and electrothermal constant-temperature drying and Vitamin C was extracted from all kinds of samples with oxalic acid.It reacted with 2,4-dinitrophenylhydrazine at 37 ℃.Its absorbency was determined at the wavelength of 490 nm by spectrophotometric method.[Result] There were 324.64 mg/100 g Vitamin C in fresh jujube and it rapidly decreased with the increasing of sun-drying days.The content of Vitamin C in red jujube treated by electrothermal constant-temperature drying was 21.63 mg/100 g and that by microwave drying was 93.25 mg/100 g.The content of Vitamin C in red jujube treated by microwave drying was significantly higher than that by nature drying for 20 d and by electrothermal constant-temperature drying.The decreasing extent of Vitamin C in fruit was smaller in the 7th d of natural drying process,the content of Vitamin C in fruit decreased significantly after the 8th d and it changed little after 2 weeks.[Conclusion] Among 3 drying methods of rd jujube,the content of Vitamin C in red jujube treated by microwave drying was highest.