(北京工商大学 食品与健康学院/北京市食品添加剂工程技术研究中心, 北京 100048)
(School of Food and Health, Beijing Technology and Business University/Beijing Engineering and Technology Research Center of Food Additives, Beijing 100048, China)
Mono Trap具有萃取量大、操作简便等特点,在西瓜汁气味化合物萃取上具有一定优势。采用Mono Trap、热脱附结合气相色谱-嗅闻-质谱萃取分析热处理前后西瓜汁气味化合物变化。使用RGC18、RSC18、RGPS这3种吸附材料从鲜榨和热处理西瓜汁样品中分别鉴定出50种和71种气味化合物。通过实验对比这3种吸附材料的萃取效果,结果显示,RGC18对西瓜汁气味化合物的萃取效果最好,利用RGC18从鲜榨和热处理西瓜汁中分别萃取到41种和53种气味化合物。西瓜汁在热处理后,风味物质发生了很大变化,呈现苦杏仁味、皂化味和酸刺味的2-甲基丁醛、糠醛、辛醛、癸醛、(E)-2-庚烯醛、乙酸和甲酸等化合物的香气活力值增大；呈现清香、柠檬气味的己醛、β-环柠檬醛和(E,E)-2,4-壬二烯醛不能被嗅闻到。这些气味化合物的变化是导致西瓜汁热处理后出现异味的重要原因。
Mono Trap has the characteristics of large extraction amount and simple operation. It has the advantages in the extraction of odor compounds in watermelon juice. Mono Trap and thermal desorption combined with gas chromatography-olfactory-mass spectrometry were used to extract and analyze the odor compounds of watermelon juice before and after thermal treatment. The three adsorbent materials, RGC18, RSC18 and RGPS, were used and identified 50 and 71 odor compounds from fresh and heated watermelon juice, respectively. The comparison results of the extraction effects of these three adsorbent materials showed that RGC18 had the best extraction effect on the odor compounds of watermelon juice. 41 and 53 odor compounds were extracted by RGC18 from fresh and heated watermelon juice, respectively. After the thermal treatment, the odor compounds of watermelon juice have changed greatly. The odor activity value of compounds exhibited bitter almond, soapy, and sharp acidic flavors, such as 2-methylbutanal, furfural, octanal, decanal, (E)-2-heptenal, acetic acid and formic acid increased, while hexanal, β-cyclic citral and (E,E)-2,4-nonadienal with green and lemon odor cannot be smelled. The changes of these compounds were the important reasons for the off-flavor of watermelon juice after thermal treatment.