Department of Safety and Quality of Fruit and Vegetables, Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Karlsruhe, Germany.
J Sep Sci. 2024 Oct;47(19):e202400305. doi: 10.1002/jssc.202400305.
The distinctive aroma of onions, consisting primarily of sulfur-containing compounds, is one of the reasons for the popularity of the vegetable. The rapid enzymatic and chemical reactions that occur after the destruction of onion bulb tissue render the analysis of the volatile profile challenging. Therefore, sample preparation is a crucial step in the analysis of the onion volatilome, but it often does not receive the necessary attention in the literature. In this work, we focused on two aspects: Firstly, we compared different sample preparation approaches to maximize the volatile yield and to enable the description of the onion volatile profile as it would emerge after a solid-phase microextraction (SPME) Arrow sampling procedure. For headspace (HS)-gas chromatography-mass spectrometry analysis, onion juice with the addition of an ammonium sulfate solution proved to be the best option. Secondly, we optimized the HS sampling and desorption parameters (enrichment time, enrichment temperature, agitator speed, desorption time) for onion volatiles using the efficient design of experiments (DoE) approach. The optimal conditions for the analysis with HS-SPME Arrow were an enrichment time of 75 min at 60°C with an agitator speed of 713 rpm and a desorption time of 120 s.
洋葱的独特香气主要来源于含硫化合物，这也是这种蔬菜广受欢迎的原因之一。洋葱鳞茎组织破坏后会迅速发生酶促和化学反应，这使得对挥发性成分谱进行分析具有挑战性。因此，样品制备是分析洋葱挥发物组的关键步骤，但在文献中往往没有得到应有的重视。在这项工作中，我们重点关注了两个方面：首先，我们比较了不同的样品制备方法，以最大限度地提高挥发性物质的产量，并能够描述固相微萃取 (SPME) Arrow 采样程序后出现的洋葱挥发性成分谱。对于顶空 (HS) - 气相色谱 - 质谱分析，添加硫酸铵溶液的洋葱汁被证明是最佳选择。其次，我们使用高效实验设计 (DoE) 方法优化了 HS 采样和解析参数（富集时间、富集温度、搅拌速度、解析时间），以用于洋葱挥发物的分析。使用 HS-SPME Arrow 进行分析的最佳条件是在 60°C 下富集 75 分钟，搅拌速度为 713 rpm，解析时间为 120 秒。
