Six varieties of garlic grown in different geographical locations in Gujarat, India were analysed for their proximate composition including volatile oil content. Twenty nine compounds were identified in the volatile oils by gas chromatography and gas chromatography - mass spectrometry, among which 15 were new compounds hitherto not reported to be components of garlic. The relative concentrations of 13 major components in the volatile oils of all six varieties are also presented.
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B RAGHAVAN, P G PRABHAKARA RAO, L JAGANMOHAN RAO,

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Journal of Spices and Aromatic Crops 8 (1) . 41-47 (1999) Chemical composition of essential oils of garlic (Allium sativum L.) P G PRABHAKARA RAO, L JAGANMOHAN RAO & B RAGI-IAVAN Department of Plantation Products, Spices and Flavour Technology Central Food Technological Research Instittde Mysore - 570 013, India. Abstract Six varieties of garlic grown in different geographical locations in Gujarat, India were analysed for their proximate composition including volatile oil content. Twenty nine compounds were identified in til<> volatile oils by gas chromatography and gas chromatography - mass spectrometry, among which 15 were new compounds hitherto not reported to be components of garlic. The relative concentrations of 13 major COTIlpOnents in the volatile oils of all six varieties are also presented. Key words: Allium sativU/n, essential oil, garlic. Abbreviations GC : Gas chromatography GC-MS : Gas chromatography - mass spectrometry Introduction Garlic (Allium sativU/n L.) is used widely in food and pharmaceutical prepa-rations. In India, Gujarat and Madhya Pradesh are major producers of garlic. Earlier reviews (Abraham et al. 1976; Whitaker 1976; Raghavan et al. 1983; Fenwick & Hanley 1985) provide ex-haustive information on the chemistry of garlic. Data on essential oil, reducing sugars, protein and fibre (Artik & Poy-razoglu 1993) and proximate composi-tion of garlic are also available (Abraham 1976). Yu et al. (1989) identified 28 vol-atile compounds by capillary GC and GC-MS analysis, of which 13 were rep-orted for the first time. The volatile compounds suspended in the aqueous phase were also identified. Pino et al. (1991) employed high resolution GC. GC-MS and eluate sniffing and identi-fied for the first time (Z)- and (E)-I-propenyl 2- propenyl disulphide (0.7 anel 1.6% respectively), 1, 2, 3-trithi-4-ene (0.2%) . and 2-propenyl tetrasulphiele (0.3%). The volatile components of crushed garlic of Mediterranean origin were anH-lysed by Mazza et al. (1992) and three compounds namely, methyl-(Z)-prop-l-enyl disulphide, allyl-(Z)- prop-I-eny! disulphide and allyl-(E)-prop-I-enyl disulphide were identified for the first time. This paper deals with screening of six varieties of garlic grown in different 42 districts of Gujarat in India so as to find their suitability for processing and product development. Further, the chemical composition of the volatile oils obtained and the relative concentra-tions of the flavour constitu~nts were computed. Materials and methods. Proxilnate composition Five geographical varieties of garlic namely, Rajkot, Gondal, Jamnagar, Junagadh and Amreli and one variety grown in Gujarat, were procured. The samples were kept in netlon bags and stored in a well ventilated room. The bulbs were broken with a wooden mal-let for separating the cloves. The tight inner skin encasing each clove was rem-oved without damaging the tissues of the garlic cloves. The samples were analysed for constituents like moisture, volatile oil, total ash, acid insoluble ash, reducing sugars, crude starch, crude fibre, crude protein and crude fat by standard methods (ASTA 1985; AOAC 1984) Volatile oil The volatile oil from fresh garlic was collected by hydrosteam distillation method (ASTA 1985) and dried over anhydrous sodium sulphate. GC - MS analysis GC-MS analysis was carried out for one of the garlic oil samples (Gondal) using a Shimadzu 17 GC coupled with a quadrapole MS (QP 5000). The condi-tions of analysis are as follows: Column Column dimension: Film thickuess Fused silica cap-illary, SPB'l'M-l 30 m x 0.32 mm i. d. 0.25 flm coated with poly dimethyl siloxane Ran et al. Carrier gas Helium (lml/min) Split ratio 1:30 Injection port temperature 250°C Detector block temperature (FID) : 250°C Oven temperature: Progrmnmcd, 60°C (2) - 2°/min _ 250°C (5) Sample injection Ifll of 25 X in acetone. GC analysis The volatile oils of six garlic samples were analysed using a GC (Shimadzu GC 15 A) fitted with SS column (1 O'X 0.125"OD) filled with 10% SE 30 Oil Chromosorb W. Nitrogen waH W-H-'rl [1~ tlw carriC'f g':lS (~Ollll/Jllin!. The injec-tion port and deledo .. block (FlD) were . maintained at 200-C and 250"C, respec-tively. The column temperature waH programmed as 75°C (2) - 4°/min -220°C (8). The volatile oils were diluted (1 to 20) in acetone and Ifll was injected. Results and discussion The results of the proximate analysis of the six varieties of garlic are given in Table 1. Volatile oil is an importaht con-stituent determining the flavour quality of garlic. Volatile oil was maximum in two varieties n"mely, Gondal and Jamnagar. One olthese was chosen for GC-MS analysis for identification of the flavouring components. The total ion chromatogram of the garlic oil (Gondal! is provided in Fig 1. Twenty nine compounds were identified (Table 2) based on the retention indices (Yu et ai. 1994) and by matching the fragmenta-tion patterns with those of the mass spectral data (NIST Library). Of Essential oils of garlic 43 Table 1. Proximate composition of garlic varieties Constituent Variety Rajkot Gondal Jamnagar Junagadh AmI'cli l\leclicinal Moisture 60.25 60.62 Volatile oil 0.65 0.85 Total ash 3.08 2.83 Acid insoluble ash 0.06 0.06 Reducing sugars 3.31 3.93 Crude starch 45.75 44.03 Crude fibre 6.41 8.87 Crude protein 20.15 23.98 Crude fat 2.10 2.15 60.00 61.87 0.87 0.79 2.93 2.87 0.06 0.02 3.63 3.40 45.15 44.16 7.10 9.52 20.82 22.23 2.00 1.78 58.1~~ 0.76 2.71 0.03 2.14 44.55 7.56 18.7f5 2.42 64.2~ 0.1'1 !"i.07 (i.OO j,J.GO 22.97 :J.(iO All vEducs are pcrcentflges (means of triplicate 3mdyses) on dry weight basis - Not carried out due to non availability of sample those identified, 26 were organa sulphur compounds, 2 were monoterpenes and 1, an ester. It is well known that when fresh garlic is macerated the cells are ruptured and the enzyme alliinase comes into contact with the precursor alliin (S-allyl cysteine sulphoxide) leading to the formation of sulphur containing rli-. tri- and tctrR " " c " ." C '" .Q « 5 9 ,11 12 1~ '1 .. ,19 20 ~~l6 76 C..J IJJ..fw w.. sulphides. In recent studies (Mazza cl aZ. 1992; Yu et al. 1994) it has been concluded that the possibility of invoivc-ment of other precursors, namely, rne-thyl, propyl and prop-1-enyi cystcinc sulphoxides cannot be ruled out. In our study, we have identified 15 new compounds in garlic which arc rwt hithcrto I'I:,pnrtccl. It is quit{' pns:-;ihlc 25 2~ J .2l,28 2'1 Retention Time (min) Fig. I. C;C' -\ I S pml i Ie or g',lrl ic oil (Gonda]) 44 Table 2. Identification of volatile components in garlic oil+ Peak No. Ret. time (min.) 1 3.05 2 3.28 3 3.43 4 3.55 5 4.08 6 4.55 7 6.10 8 6.63 9 7.80 10 8.20 11 8.48 12 10.37 13 10.62 14 10.90 ]5 11.08 16 11.58 17 11.78 18 12.90 19 13.08 20 19.10 21 19.40 22 19.68 23 19.95 24 20.15 25 22.35 26 31.83 27 34.92 28 35.37 29 . 39.58 + Gondal variety :I: Heportcd for the first time " Identified tentatively Compound Allyl methyl disulphide Methyl (Z) prop-I-enyl disulphide Methyl (E) prop-I-enyl dlsulphide Dithia cyclopentane Dimethyl trisulphide Ocinlene* Linlonene* Allyl propyl disulphide Diallyl disulphide Allyl (Z) prop-I-enyl disulphide Allyl (E) prop-I-enyl disulphide Allyl methyl trisulphide Methyl propyl trisulphide* Methyl (Z) prop-I-enyl trisulphide* Methyl (E) prop-I-enyl trisulphide* 'I'rithia cyclo hexane* 3-Vinyl-4H-l, 2-dithine 2-Vinyl-4H-l, 3-dithine Dimethyl tetra sulphide* Diallyl trisulphide Allyl propyl trisulphide* Allyl (Z) prop-I-enyl trisulphide'" Allyl (E) prop-I-enyl trisulphide* Tetrathiacyc1oheptane~'n Allyl methyl tetra sulphide* Diallyl tetra sulphide Allyl (Z) prop-I-enyl tetra sulphide" Allyl (E) prop-l-enyl tetrasulphide ':t Cinnamyl tiglate* Rao et HI. KI M' SPB-l 903 120 915 120 922 120 928 104 949 126 969 D6 1021 136 1037 148 1069 146 1079 146 1086 146 1126 J G2 1130 152 1139 ]52 1139 ]52 1147 laC) 1151 144 1170 144 1171 158 1270 178 1275 ]80 1279 178 128:3 178 1286 ]70 1322 ]H4 1472 210 1522 210 153(j 21U 1599 216 that the new components identified in this study (Fig 2), namely, methyl propyl trisulphide (1), methyl (Z)-prop-I-enyl trisulphide (2) and its (E) isomer (3), dimethyl tetra sulphide (4), allyl (Z)-prop-l-enyl tetra sulphide (5) and its (E) isomer (6), allyl (Z)-prop-l-enyl trisulphide (7), and its (E) isomer (8), allyl propyl trisulphide (9) and allyl methyl tetra sulphide (10) might have formed from the corresponding unstable thiosulphonates through decomposition and rearrangement of alliin (S-allyl cysteine sulphoxide) (11), S-propyl cysteine sulphoxide (12), S-methyl cystine sulphoxide,.(l3), S-(E)-l-propenyl cysteine sulphoxide (14) and their pre-cursors y-glutamyl alkenyl cysteine,; "0 these are reported by Yu (1996) to IX' present in intact garlic. Tv.ro other sulphur volatiles, trithia cyclohexene (15) and tetra thia cycloheptHne (16) might have formed from alliin. Limonen" and ociinene 111ight have formed in a monoterpene paihway, WhC'I'CRS cinnamyl tiglate shows the presence of' -~ 'I .ij >1 I I j ., . J ..  J ES8cnUal nils of ,f.!(fdic 1 2 3 4 5 8 10 11 12 NH, ~ HOOC~~ () 13 14 15 16 11 --... ~ .. 15,16 12,13 --....... 1 11,12 --....... 9 13 11,13 --..... , :. 10 13,14 11,14 cinnamyl unit from shikimic acid metabolites and tiglyl unit from mevalonic acid metabolites. These ob-servations al'e interesting and needs further confirmation. Based on peak areas obtained through GC analyses of the six garlic oils, the relative concentration of 13 major com-ponents are computed (Table 3), It may be noted that the combined percentages orE and Z isomers of methyl prop-I-enyl disulphide and E and Z isomers of allyl prop-I-enyl disulphide are furnished in the table since they could not be resolved in the GC column under the --.~ 4 --....... 2,3 conditions employed. It may also b" noted that the di- and tri-sulphides together account for more than 9Qf;fr: of all the samples analysed and diallyl disulphide is the major character im-pact compound in garlic. Acknowledgements This work is part of a sponsored prnj"c( funded by Spices Board, Kochi. Th" authors thank the spons'ors ft)r funding and procurement and supply of' authen-tic samples of garlic. They also [lwok Dr. V Prakash, Director, CFTRI, Myso]'!) for his keen interest in the work. 46 Roo ct :11. Table 3. Relative concentrations of garlic oil constituents Component Ret.time Variety (min) A B C D E F Diallyl sulphide 6.628 2.43 2.08 1.39 2.4] 1.15 1.2!) Allyl methyl sulphide 8.328 11.96 10.86 8.28 11.41 7.32 4.44 Methyl (Z) prop-I-enyl 9.132 0.07 1.09 0.94 1.27 0.97 O.O(i disulphide and its (E) isomer Dimethyl trisulphide 10.470 0.63 2.24 1.88 1.84 1.77 n.!) 1 Diallyl disulphide 14.173 38.49 34.35 36.20 41.71 27.06 4G.8!1 Allyl (Z) prop-I-enyl 14.897 4.66 5.24 5.84 5.28 7.20 5.;-36 disulphide and its (El isomer Allyl methyl 16.298 lLl3 17.42 16.35 14.70 18.20 8.:10 trisulphide 2-Vinyl-4H-l, 3-dithin 18.810 0.56 0,67 0.85 0.59 0.76 1.7(i Diallyl trisulphide 22.133 29.34 24.70 27.36 19.93 34.05 :Hl.fi7 Allyl methyl 24.060 0.04 0.40 0.16 0.14 0.3:) 0.S7 tetrasulphide Diallyl tetrasulphide 29.890 0.66 0.91 0.74 0.69 l.](i OR2 A : Ra,jkot; B : Gondal; C : J amnagar; D : J unagadh; E : Amreli; F : Medicinal References Abraham K 0 1976 Studies on sulphur flavour constituents in asafoetida and the alliums. Ph D Thesis, University of Mysore, Mysore. Abraham K 0, Shankaranaryana M L, Raghavan B & Natarjan C P 1976 Alliums - varieties, chemistry and analysis. Lebensm. Wiss. Techno!. 9 : 193-200. Artik N & Poyrazoglu E S 1994 Study on chemical composition of garlic grown in Kastamonu city. Gida 19 (1) : 3-9; cf. FSTA 1995 27 : 7T44. Association of Official Analytial Chem-ists (AOAC) 1984 Official Methods of Analysis 14th Ed. Washington. American Spice Trade Association (ASTA) 1985 Official Analytical Methods 3rd Ed. Englewood Cliffs, New Jersey. Fenwick G R & Hanley A B 1985 The genus Allium - Part 1. CEC Crit. Rev. Food Sci. Nuh-i. 22 (3) : 199-271. Mazza G, Ciaravolo S, Chiricosta G & Celli S 1992 Volatile flavour com 1'0-nents from ripening and Inature garlic bulbs. Flav. Fragr. J. 7 111-116. Pino .J, Rosado A & Gonzalez A 1991 Volatile flavour components of gaJ'-11c essential oi!. Acta Aliment. 20 (3/ 4) : 163-171; cf. FSTA 1903 25 : 2T54. " Raghavan B,' Abraham K 0 & Shankaranarayana M L 1983 Chem-istry of garlic and garlic products. J. Sci. Ind. Res. 42 : 401-409. Whitaker J R 1976' Development of flavor, odor and pllngency in onion and garlic. Adv. Food Res. 22 73-133. Essential oils of garlic Yu T H 1996 Contribution of nonvolatile sulfur-containing flavor precursors of the genus Allium to the flavor of thermally processed Allium vege· tables In : Risch S J & Ho C T (Eds) Spices: Flavour Chemistry and An· tioxidant Properties (pp. 53·64) ACS Symposium Series 660, American Chemical Society, Washington DC. 47 Yu T H, Wu C M & Liou Y C 1989 Volatile compounds from garlic. J. Agric. Food Chem. 37 : 725·730. Yu T H, Lin L Y & Ho C T 1994 Volatile compounds of blanched, fried blanched and baked blanched garlic slices. J. Agric. Food Chem. 42 1342·1347. 

Chemical composition of essential oils of garlic (Allium sativum L.)

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Chemical composition of essential oils of garlic (Allium sativum L.)

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