Article pubs.acs.org/JAFC
Identification of Ginger (Zingiber of f icinale Roscoe) Volatiles and Localization of Aroma-Active Constituents by GC−Olfactometry Xueli Pang,* Jianmin Cao, Dabin Wang, Jun Qiu, and Fanyu Kong* Laboratory of Quality & Safety Risk Assessment for Tobacco, Ministry of Agriculture, Tobacco Research Institute of Chinese Academy of Agricultural Sciences, Qingdao, China 266001 ABSTRACT: For the characterization of chemical components contributing to the aroma of ginger, which could benefit the development of deep-processed ginger products, volatile extracts were isolated by a combination of direct solvent extraction− solvent-assisted flavor evaporation and static headspace analysis. Aroma-impact components were identified by gas chromatography−olfactometry−mass spectrometry, and the most potent odorants were further screened by aroma extract dilution analysis (AEDA) and static headspace dilution analysis (SHDA). The AEDA results revealed that geranial, eucalyptol, βlinalool, and bornyl acetate were the most potent odorants, exhibiting the highest flavor dilution factor (FD factor) of 2187. SHDA indicated that the predominant headspace odorants were α-pinene and eucalyptol. In addition, odorants exhibiting a high FD factor in SHDA were estimated to be potent aroma contributors in AEDA. The predominant odorants were found to be monoterpenes and sesquiterpenes, as along with their oxygenated derivatives, providing minty, lemon-like, herbal, and woody aromas. On the other hand, three highly volatile compounds detected by SHDA were not detected by AEDA, whereas 34 highpolarity, low-volatility compounds were identified only by AEDA, demonstrating the complementary natures of SHDA and AEDA and the necessity of utilizing both techniques to accurately characterize the aroma of ginger. KEYWORDS: ginger (Zingiber off icinale Roscoe), aroma-active components, aroma extract dilution analysis (AEDA), static headspace dilution analysis (SHDA), gas chromatography−olfactometry (GC−O)
■
INTRODUCTION
(GC−O), to accurately characterize the chemical components that contribute to ginger aroma. To the best of our knowledge, only one study on the characterization of aroma-active compounds in fresh ginger has been reported.4 Unfortunately, direct solvent extraction was applied, possibly leading to the loss of some highly volatile components and the production of artificial components due to multiple solvent removal steps. In addition, previous studies utilized a single extraction method, such as hydrodistillation,9 solid-phase microextraction (SPME),10−13 direct solvent extraction (DSE),4 supercritical fluid extraction (SCFE),14 or microwave distillation combined with solid-phase microextraction (MD-SPME);15 hence, it would have been difficult in these studies to comprehensively obtain all of the volatiles with different properties from a complex natural matrix such as ginger, as each method has its own limitations. Thus, multiple complementary extraction methods are recommended for obtaining a more complete, accurate volatile profile of ginger. Hence, the present study aimed to first obtain a more comprehensive volatile profile of fresh ginger by using two complementary extraction techniques, namely, static headspace analysis (SHA), which is efficient in isolating highly volatile compounds, and solvent-assisted flavor evaporation (SAFE), which is sensitive to semivolatile compounds. The aroma-active compounds were then screened and identified using gas chromatography−olfactometry (GC−O) and gas chromatog-
Ginger (Zingiber off icinale Roscoe; family Zingiberaceae), an edible and medicinal plant, has long been grown in several tropical and subtropical areas of Southern Asia, including China, which is one of the main producers.1 Among several factors affecting the quality of ginger, its typical flavor, which is a combination of pungent taste and aroma, is one of the major determinants for consumer acceptance. Because of its unique flavor properties, ginger is widely used in the food industry to enhance tang and zest2 and is currently applied in perfumes, room sprays, and cosmetic products.3 Currently, nonvolatile phenolic compounds, such as [6]-, [8]-, and [10]-gingerol, are well-known to give ginger its pungent taste, whereas its characteristic aroma is provided by essential oils4 and has been previously described as warm but fresh-woody, spicy, and with a peculiar resemblance to the aroma of orange, lemongrass, and coriander seed oil in its initial, fresh top notes, whereas the sweet and heavy undertone is tenacious, sweet, and almost balsamic-floral.5 Several studies have been carried out to reveal the composition of ginger essential oil.3,6−10 However, most of these studies reported qualitative and quantitative analyses of the volatile components, whereas the identities of the volatile compounds that contribute to the ginger aroma have not yet been reported. It is well accepted that only a limited number of volatile compounds with concentrations greater than their odor thresholds (also called aroma-active compounds) contribute to the overall aroma. Hence, it is crucial to perform further studies on the aroma-active compounds of fresh ginger by using odorant location techniques, such as gas chromatography−olfactometry © 2017 American Chemical Society
Received: Revised: Accepted: Published: 4140
February 6, 2017 April 8, 2017 April 10, 2017 April 10, 2017 DOI: 10.1021/acs.jafc.7b00559 J. Agric. Food Chem. 2017, 65, 4140−4145
Article
Journal of Agricultural and Food Chemistry Table 1. Aroma-Active Compounds in Fresh Ginger Juice Determined by Aroma Extract Dilution Analysis LRIc no.a
name
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
methylbenzenef ethyl butanoatef styrenef heptan-2-olf 4,6,6-trimethylbicyclo[3.1.1]hept-3-ene/α-pinenef 3,3-dimethyl-2-methylidenebicyclo[2.2.1]heptane/camphenef unknowng 6,6-dimethyl-4-methylidenebicyclo[3.1.1]heptane/β-pinenef 7-methyl-3-methylideneocta-1,6-diene/β-myrcenef octanalf 2-methyl-5-propan-2-ylcyclohexa-1,3-diene/α-phellandrenef 3-methylidene-6-propan-2-ylcyclohexene/β-phellandrenef heptyl acetatef 2,2,4-trimethyl-3-oxabicyclo[2.2.2]octane/eucalyptol f (E)-oct-2-enalf 1-methyl-4-propan-2-ylcyclohexa-1,4-diene/γ-terpinenef 2-[(2S,5S)-5-ethenyl-5-methyloxolan-2-yl]propan-2-ol/linalool oxide IIh 1-methyl-4-propan-2-ylidenecyclohexene/terpinolenef (1R,4S)-4-methyl-1-propan-2-ylbicyclo[3.1.0]hexan-4-ol/trans-sabinene hydrateh 3,7-dimethylocta-1,6-dien-3-ol/β-linaloolf unknowng (1S,4S)-1-methyl-4-propan-2-ylcyclohex-2-en-1-ol/cis-2-p-menthen-1-olh 3,7-dimethyloct-6-enal/citronellalf 2,2,3-trimethylbicyclo[2.2.1]heptan-3-ol/camphene hydrateh 1,7,7-trimethylbicyclo[2.2.1]heptan-6-ol/endoborneolf 4-methyl-1-propan-2-ylcyclohex-3-en-1-ol/terpinen-4-olf 2-(4-methylcyclohex-3-en-1-yl)propan-2-ol/α-terpineolf (2Z)-3,7-dimethylocta-2,6-dienal/neralf (2E)-3,7-dimethylocta-2,6-dien-1-ol/geraniolf
30 31 32 33 34 35 36 37 38 39 40 41 42 43
(2E)-3,7-dimethylocta-2,6-dienal/geranialf (2,2,4-trimethyl-3-oxabicyclo[2.2.2]octan-5-yl) acetate/2-acetoxy-1,8-cineolef (4,7,7-trimethyl-3-bicyclo[2.2.1]heptanyl) acetate/bornyl acetatef (3R,4R)-4-ethenyl-4-methyl-1-propan-2-yl-3-prop-1-en-2-ylcyclohexene/δ-elemeneh 3,7-dimethyloct-6-enyl acetate/citronellyl acetatef (1S,2S,4R)-1-ethenyl-1-methyl-2,4-bis(prop-1-en-2-yl)cyclohexane/β-elemenef 1,1,4,7-tetramethyl-1a,2,3,4,4a,5,6,7b-octahydrocyclopropa[e]azulene/α-gurjunenef 1-methyl-4-(6-methylhept-5-en-2-yl)benzene/α-curcumenef (1Z,6Z)-1-methyl-5-methylidene-8-propan-2-ylcyclodeca-1,6-diene/germacrene Dh (5R)-2-methyl-5-[(2S)-6-methylhept-5-en-2-yl]cyclohexa-1,3-diene/zingiberenef (4S)-1-methyl-4-(6-methylhepta-1,5-dien-2-yl)cyclohexene/β-bisabolenef (3E,6E)-3,7,11-trimethyldodeca-1,3,6,10-tetraene/(E,E)-α-farnesenef 3-(6-methylhept-5-en-2-yl)-6-methylidenecyclohexene/β-sesquiphellandrenef (1S,4R)-4-methyl-1-(6-methylhept-5-en-2-yl)bicyclo[3.1.0]hexan-4-ol/ cis-sesquisabinene hydrateh (6E)-3,7,11-trimethyldodeca-1,6,10-trien-3-ol/(E)-nerolidolf
44
odorb
DB-5
DB-WAX
glue, paint fruity balsamic, cool coco water, sweet sweet, pine camphor apple-like dry woody fruit, geranium citrus, sweet mint, pepper mint, terpentine fenugreek fruity minty, medicine-like nut, agreeable oily, woody, bitter floral, fresh pine, plastic woody, nutty, floral, sweet woody, camphor herb, spicy camphoreous, soapy menthol, bitter camphor, balsamic wood, earth woody, apple-like citrus, sweet ginger-like, lemon peel ginger-like, minty woody, galangal-like ginger-like, woody sweet, herbal ginger-like, woody sweet woody, medicine-like herb, lemon-like woody, spice spice, minty balsamic, woody citrus, herbal herbal, fruity woody
