30種大蒜的園藝性狀及含硫化合物質量分析

Abstract

大蒜為世界上重要的香辛蔬菜，由於含有特殊氣味常用以食物調味，其氣味來源多屬含硫揮發性或半揮發性含硫化合物。本研究利用固相微萃取-氣相層析質譜儀（SPME-GC/MS）及溶劑萃取-GC/MS兩種方法，分析由台中區農業改良場所提供之大蒜品種30種，其中包括22個大陸品種、4個台灣品種、2個韓國品種和2個越南品種的揮發性成分，各品種進行了型態調查。蒜球周徑介於10.17 cm- 18.27cm，蒜瓣數介於6 ~ 23。供試品種4種為軟骨蒜，26種為硬骨蒜。型態特徵上，‘和美’與‘大片黑’比與‘宜蘭白’或‘芳苑’有較多相似。使用SPME-GC/MS分析‘和美’、‘大片黑’和‘宜蘭白’三個品種葉齡20、40及60天之葉片含硫化合物種類及含量，皆表現葉片隨著葉齡增加、揮發性含硫化合物的種類及含量逐漸減少。分析葉身、葉鞘及鱗莖三個不同部位的結果顯示，‘和美’和‘宜蘭白’兩品種表現相同的趨勢，即葉片中的揮發性含硫化合物最少，葉鞘中的含硫化合物種類較多，而以蒜球中的含硫化合物種類最多。在含硫化合物的相對含量上，以發育中的蒜球最高，其次為葉鞘，而葉片中的含量最低。‘大片黑’以葉鞘中的含硫化合物種類最多，多數含硫化合物的相對含量也以葉鞘最高，葉片的含硫化合物種類最少，含量最低。分析‘和美’和‘大片黑’ 蒜瓣和蒜皮中的揮發性含硫化合物組成及相對含量都同樣以蒜皮中的揮發性含硫化合物遠較蒜瓣為少，量也較低。以SPME-GC/MS分析30個大蒜品種葉片及鱗莖，各偵測到17和20種揮發性化合物，葉片氣味主要由一硫（1種）、二硫（5種）及三硫（2種）化合物組成，鱗莖中化合物種類及含量較葉片多，四硫（1種）化合物亦為主要化合物之一。以溶劑-GC/MS分析30個大蒜品種鱗莖，共偵測到18種揮發性化合物，成分皆為一硫（1種）、二硫（6種）及三硫（1種）化合物；相較於SPME所得之結果，溶劑法偵測到的化合物中除了3-vinyl-1,2-dithiacyclohex-4-ene和3-vinyl-1,2-dithiacyclohex-5-ene兩個環狀化合物含量大量增加外，其他成分皆顯著減少，並且增加了2-vinyl-1,3-dithiane，而這三種化合物應為萃取時產生之人為產物。以SPME-GC/MS分析大蒜葉片、鱗莖和溶劑萃取-GC/MS分析大蒜鱗莖的群聚分析結果，各品種依化合物的種類及成分含量高低而可分群。由SPME分析，台灣四個品種中‘和美’歸為葉片及鱗莖含硫化合物種類及含量均少的一群，‘大片黑’ 歸為葉片及鱗莖含硫化合物種類均少的一群，‘芳苑花蒜’葉片中含硫化合物種類多，但鱗莖屬於化合物種類少的一群，‘宜蘭白’屬於葉片及鱗莖含硫化合物種類均多的一群。以溶劑萃取分析，四個品種之鱗莖，除‘芳苑花蒜’外，其餘三品種皆屬硫化合物種類多的一群。比較兩個不同生產地的‘和美’蒜球揮發性化合物，有產地差異，但兩個不同產地的‘大片黑’則成分相似。

Garlic (Allium sativum L.) is an important vegetable of the world for its culinary value as a flavoring agent. Its volatile or partially-volatile sulfur-containing compounds contribute to the characteristic flavors. In this study both solid-phase microextraction -gas chromatography/mass spectrometry (SPME-GC/MS) and solvent extraction-GC/ MS are employed to analyze the flavor compounds of 30 garlic cultivars. All cultivars are grown at Taichung District Agricultural Research and Extension Station, Chang-Hua, including 4 cultivars of Taiwan, 22 of China, 2 of Korea and 2 from Vietnam. The result of field plant characters of 30 garlic cultivars indicated that 4 cultivars are soft-neck with the rest being hard-neck which produced a flower stalk. The perimeter of the bulb ranges from 10.17 to 18.27 cm and the cloves number from 6 to 23. Morphologically, cvs. ‘He-Mei’ and ‘Large-Black-Leaf’ showed more similarities than they are to either ‘Fan-Yuan’ or ‘Yi-Lan White’. Both the number and amount of arising sulfur-containing volatiles collected by SPME- GC/MS in leaf blades decreased with leaf age increasing from 20 d, 40 d to 60 days after labeling in cvs. ‘He-Mei’, ‘Large-Black-Leaf’, and ‘Yi-Lan-White’. Both cvs. ‘He-Mei’ and ‘Yi-Lan-White’ had the least volatile sulfur-containing compounds in leaf blades followed by leaf sheath and the developing bulb having the most and the highest content of sulfur volatiles, while cv. ‘Large-Black-Leaf’ had the most and highest amount of total volatile compounds in leaf sheath and the least in leaf blades. The cloves had more and higher amount of sulfur-containing volatiles than clove peels did in both cvs. ‘He-Mei’ and ‘Large-Black-Leaf’ tested. In SPME-GC/MS analyses, 17 and 20 volatile compounds were detected in leaf blades and cloves of 30 cultivars, respectively. The major compounds of leaf blades were sulfide (one compound), di-sulfide (5 compounds) and tri-sulfide (one compound). In addition to these compounds, the cloves contain also tetra-sulfide and with higher contents of sulfur volatiles than those of leaf blade. In solvent-GC/MS analyses, 18 volatile compounds were detected in garlic cloves. The major ones were di- and tri-sulfide with contents being much decreased as compared with the results of SPME-GC/MS, except for 3-vinyl-1,2-dithiacyclohex-4-ene and 3-vinyl-1,2-dithiacyclohex-5-ene. Compound of 2-vinyl-1,3-dithiane was only detected in solvent-GC/MS. These latter three compounds might be artifacts. The dendrogram based on leaf or bulb sulfur-containing volatiles extracted either by SPME- GC/MS or solvent-extraction GC/MS indicate that all 30 garlic cultivars can be grouped by the number and level of compounds they contain. From the results of SPME-GC/MS, ‘He-Mei’, the early variety in Taiwan is low in volatile sulfur-containing compounds in both leaves and bulbs; ‘Large-Black-Leaf’, the main bulb variety of Taiwan follows and contains relatively low volatile sulfur compounds in both leaves and bulbs. In comparison with ‘Large-Black-Leaf’, ‘Fang-Yuan’ has more volatile compounds in number in leaves but not in cloves. Cultivar ‘Yi-Lan-White’ is high in volatile-sulfur containing compounds in both leaves and in bulbs. The results of solvent-extraction GC/MS indicates garlic cultivars of Taiwan, except cv. ‘Fang-Yuan’ contain high number of volatile sulfur compounds. Variations in volatile sulfur compounds were detected in cv. ‘He-Mei’ but not in ‘Large-Black-Leaf’ of two different sources.