Department of NEUROFARBA, University of Florence, Via Ugo Schiff, 6, 50019 Sesto Fiorentino FI, Florence, Italy.
QuMAP Laboratory, PIN Polo Universitario Città di Prato, Piazza Giovanni Ciardi, 25, 59100 Prato PO, Italy.
Molecules. 2020 Jan 18;25(2):408. doi: 10.3390/molecules25020408.
Onion is widely used worldwide in various forms for both food and medicinal applications, thanks to its high content of phytonutrients, such as flavonoids and volatile sulfur compounds. Fresh onion is very perishable and drying is widely applied for extending shelf-life, thus obtaining a very easy-to-use functional food ingredient. The flavonoid and volatile fractions of different onion cuts (flakes, rings) prepared through different drying cycles in a static oven, were characterized by high-performance liquid chromatography with a diode-array detector HPLC-DAD, Head Space-Solid Phase Micro Extraction followed by Gas Chromatography coupled with Mass Spectrometry (HS-SPME-GC-MS) and Head-Space Solid Phase Micro Extraction followed by comprehensive two-dimensional Gas-Chromatography (HS-SPME-GC×GC-TOF). Onion flakes showed a significantly higher flavonoid content (3.56 mg g) than onion rings (2.04 mg g). Onion flakes showed greater amount of volatile organic compounds (VOCs) (127.26 mg g) than onion rings (42.79 mg g), with different relative amounts of di- and trisulfides-disulfides largely predominate the volatile fraction (amounts over 60% on the total volatile content), followed by trisulfides and dipropyl disulfide and dipropyl trisulfide were the most abundant VOCs. HS-SPME-GC×GC-TOF allowed for the detection of the presence of allylthiol, diethanol sulfide, 4,6-diethyl1,2,3,5-tetrathiolane, not detected by HS-SPME-GC-MS, and provided a fast and direct visualization and comparison of different samples. These results highlight different nutraceutical properties of dried onion samples processed otherwise, only differing in shape and size, thus pointing out potentially different uses as functional ingredients.
洋葱因其富含类黄酮和挥发性硫化合物等植物营养素，以各种形式在全球范围内被广泛用于食品和药用。新鲜洋葱极易腐烂，干燥广泛应用于延长保质期，从而获得非常易于使用的功能性食品成分。通过在静态烘箱中进行不同干燥周期制备的不同洋葱切片（薄片、环）的黄酮类化合物和挥发性部分，采用高效液相色谱法与二极管阵列检测器（HPLC-DAD）、顶空固相微萃取后气相色谱-质谱联用（HS-SPME-GC-MS）和顶空固相微萃取后全二维气相色谱（HS-SPME-GC×GC-TOF）进行了表征。洋葱薄片的类黄酮含量（3.56mg/g）明显高于洋葱环（2.04mg/g）。洋葱薄片显示出更多的挥发性有机化合物（VOCs）（127.26mg/g），而洋葱环（42.79mg/g），二硫化物和三硫化物的相对含量较大，大量占挥发性部分（总量超过 60%），其次是三硫化物和二丙基二硫化物和二丙基三硫化物是最丰富的 VOCs。HS-SPME-GC×GC-TOF 允许检测到烯丙基硫醇、二乙硫醇、4,6-二乙基-1,2,3,5-四硫杂环戊烷的存在，这些物质不能通过 HS-SPME-GC-MS 检测到，并提供了不同样品的快速直接可视化和比较。这些结果突出了以不同方式加工的干洋葱样品的不同营养特性，仅在形状和大小上有所不同，因此指出了作为功能性成分的潜在不同用途。
