可可发酵过程中蛋白质降解与吡嗪类化合物变化分析

Analysis of Protein Degradation and Pyrazine Content Change during Cocoa Fermentation

采用固相微萃取(SPME)对发酵干燥和焙炒的可可豆挥发性成分进行萃取,以气相色谱/质谱联用仪(GC/MS)对挥发性成分进行分析,并对发酵过程中蛋白质的含量和氨基酸进行测定。结果表明:发酵过程中,蛋白质发生了大幅度降解,减少了50%;氨基酸组成也发生了一些变化,特别是游离氨基酸大幅度增加,其中疏水性氨基酸增加较多,这些物质的生成对可可香气的形成具有重要贡献。发酵后干燥可可豆中含氮杂环化合物含量比较低,而烘烤可可豆中的含氮杂环化合物,如吡嗪的含量有了大幅度的增加,特别是发酵干燥后焙炒过程中2,5-二甲基吡嗪、2,3,5-三甲基吡嗪、2,3,5,6-四甲基吡嗪都有明显增加,这表明发酵中蛋白质水解促进了这类可可特征香气成分的形成。

The volatile flavor components obtained from dried and roasted cocoa at specific intervals during fermentation were analyzed with headspaee solid-phase microextraction-gas chromatography/mass spectrometry （SPME-GC/MS）, and the changes of protein and free amino,Jacids during fermentation were investigated. Analysis indicated that the free amino acids were greatly generated during the partial hydrolysis of cocoa protein and took part in the formation of volatile compounds. The kinds of pyrazines were also identified at low concentrations for fermented cocoa beans, but they were found with high quantity for roasted cocoa beans after fermentation, especially 2,5-dimethyl-, 2,3,5-trimethylpyrazine and 2,3,5,6-tetramethylpyrazine were distinctly formed at the stage of roasting.