Morphological characteristics and sulfur-containing compounds analyses in 30 garlic (Allium sativum) cultivars
Date Issued
2008
Date
2008
Author(s)
Chang, Dai-Yu
Abstract
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.
Subjects
volatile sulfur-containing compounds
solid-phase microextraction (SPME)
solvent-extraction
gas chromatography/mass spectrometry(GC/MS)
cluster analysis of garlic cultivars
Type
thesis
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