Flavour Characterization of Sumach (Rhus Coriaria L.) by Means of GC/MS and Sensory Flavour Profile Analysis Techniques

Abstract

The flavour characteristics of sumach (Rhus coriaria L.) from the southeastern region of Turkey were investigated by using GC/MS and sensory flavour profile analysis techniques. Three different extraction methods for the isolation of volatiles were applied prior to GC/MS analysis. A total of 55, 17 and 28 volatiles were identified from the sumach sample by using liquid-liquid extraction, SC-CO₂ extraction and distillation techniques, respectively. Malic acid was detected to be responsible for the sour taste of sumach. β-caryophyllene (spicy, woody), cembrene (woody) and caryophyllene oxide (spicy) which were detected by using the three different isolation techniques seem to have an important contribution to sumach flavour. Sensory flavour profile analysis revealed oil and acid aroma and dried lemon balm, cellulose/woody, spicy, earthy and astringent flavour characters as common descriptors in grinded sumach, SC-CO₂ extract, and water extract of sumach samples examined in this study.

Keywords:

• Sumach
• Sumach flavour
• Gas chromatography (GC)/mass spectrometry analysis (MS) of sumach
• Flavour profile of Sumach

INTRODUCTION

Sumach (Rhus coriaria, Lindl.) a member of the Anacardiaceae family is a shrub used in pharmaceutical and cosmetic preparations, food colouring or preservations, veterinary practices and leather processing technologies.[1] The fruits of the Sumach plant are reddish brown colour and contain one seed, and the plant reaches 3–4 m in height in the wild.[2] General distribution of this plant is in Mediterranean countries and Canary Islands, reaching Iran and Afghanistan in the East. It is found naturally growing in the Aegean, Mediterranean, southeastern, central and northern regions of Turkey. R. coriaria has economic importance in the leather industry, pharmacy and food technology. The powdered leaves of sumach were used as a tanning agent because of its high tannin content.[3,4] In Turkey, the leaves and twigs are used as a black dye, and the bark as a yellow dye for wool or cotton. Because of their astringent properties, sumach fruits are used in folk medicine for diarrhea, diabetes, for mouth and throat diseases, to staunch bleeding and to treat intestinal diseases.[2,3,5,6] The sumach fruits are either used whole or with the dried pericarp separated from the hard seed, while the coarsely ground fruit is mixed with salt to season roasted meat or the boiled up extract is used to flavour salads and vegetables. The fruits contain tannins, volatile oil, various organic acids (malic, citric, pyruvic), anthocyanins and fixed oil. The overall flavour involves fatty aldehydic notes, which are reminiscent of meat bouillon, and herbaceous, spicy, having slightly cumin-like aspects.[2,3] There are several studies on chemical composition of essential oil,[2,3,7,9] antibacterial activity,[10–12] antioxidant activity,[13–15] extraction of tannins,[4,16] mineral contents,[17] and traditional medicinal effects[5,6] of sumach. In a study on the essential oil of Rhus coriaria fruits from wild habitats and various provinces of Turkey by using a modified Karlsruhe apparatus and GC/MS technique, several terpenoids and aliphatic compounds have been identified. In the same study, sensory evaluation of water vapor volatiles of tanner's sumach fruits which were gathered from wild habitats in five different provinces of Turkey was conducted by using the gas chromatographic sniffing technique to determine the components with the highest odour impressions. Aldehydic components, along with naphthalene and the terpenes and sesquiterpenes were found to compose the typical aroma of sumach.[2]

In the present study, the efficiency of three different techniques for isolation of volatiles in sumach fruits from the southeastern region of Turkey was compared prior to GC/MS analysis. The sensory flavour attributes of sumach fruits were identified and rated by using the flavour profile analysis technique.

MATERIALS AND METHODS

Materials

Sumach fruits were obtained from Diyarbakir area that is located in the southeastern region of Turkey. The fruits were collected from the mountains during the harvest period in the year 2003. The samples were packaged under vacuum in 500 g polypropylene (BOPP) bags and stored in the refrigerator at 4 ± 2°C until used for analysis.

Methods

Extraction of flavour compounds for GC/MS analysis

The flavour compounds of the sumach fruits were isolated by using liquid-liquid extraction[18] supercritical carbon dioxide extraction (SC-CO₂);[19–21] and distillation[22] techniques prior to GC/MS analysis. In the liquid-liquid extraction technique; sumach seeds were grinded and sieved (Fritsch Analysette 3, Electromagnetic Laboratory Sieve Shaker) to remove hard seeds of the fruit. 25 g of sample was slurried with 100 ml of ethanol in a Waring blender and the slurry was transferred into the sample tube of the extractor. The volatile compounds were collected in 75 ml of hexane while the extraction continued for six hours and hexane was concentrated to approximately 5 ml under nitrogen gas.

In the supercritical carbon dioxide extraction technique, grinded sumach samples were isolated by using a SFE lab-type apparatus (SFE Process System Model #9925, Applied Separations Inc.) consisting of 1 L stainless steel solid sample extractor and 2 L stainless steel liquid extractor, and a separator. The dynamic extraction at 51°C and 135 bar and extraction period of 155 minutes were used. The above-mentioned parameter values were selected after a number of experiments and were considered as the optimum conditions for obtaining acceptable yield. The distillation technique was applied by distilling 50 g of grinded sumach sample for four hours in the distillation apparatus as described in ISO 6571.[22]

GC/MS Analysis

Separation and identification of the volatiles was performed by using a Perkin Elmer Autosystem XL GC gas chromatograph with a 30m × 0.25 mm ID × 0.25 μm film thickness 5MS capillary column. The column temperature was programmed as follows: 60 °C for 1 min; 5°C min⁻¹ to 260°C, held for 24 min. The carrier gas was helium at 1 ml min⁻¹ flow rate. The injector and detector temperatures were set at 260°C and 280°C, respectively. The electron voltage was 70 eV and the mass range was m/z 35–350. Wiley and Nist libraries were used as MS library.

Sensory Flavour Profile Analysis

Flavour profile analysis technique[23] was applied to grinded sumach, SC-CO₂ extract and concentrated water extract of grinded sumach samples. Concentrated water extract of sumach was prepared by mixing the grinded and sieved sumach sample with water (sumach: water-1: 5) as suggested by Bayram,[24] the mixture was stirred in a shaker for 24 h at room temperature and filtered. The filtrate was evaporated to 27 Brix and the concentrate was used for sensory flavour profile analysis.

Samples were judged by seven assessors aged 25–36 years who were previously tested for their sensitivity to major tastes and odours. Seven one-hour training sessions were conducted prior to the formal evaluation of sumach samples by providing the reference standards. The sensory term equivalents of the volatiles[25,26] that were detected by GC/MS and reference standards (Table 1) were used during the training sessions. Formal evaluation of sumach fruits was performed in a total of 20 sessions. The sumach samples were presented to the judges at room temperature (20–23°C) in 50 ml beakers covered with aluminium foil. The judges identified and rated the intensity of each character on a 0–5 cm unstructured scale. Spider web diagrams were obtained by using Microsoft Excel 5.0.

Table 1 Reference samples and descriptive terms used during training sessions

Descriptive terms	References
Sour	0.43 g/L citric acid solution
Oil	Linseed oil
Oleastar	Oleastar fruit
Tobacco	Tobacco (Drum, Premium quality handrolling tobacco, UK)
Cellulose/Woody	Wood
Medicinal bitter	0.195 g/L caffein solution
Sweet	5.76 g/L sucrose solution
Dried lemon balm flavour	Dried lemon balm
Dried basil flavour	Dried basil
Apple-like	Green apple
Grape molasses	Grape molasses
Henna	Henna (Amar's, Hennex, India)
Green walnut skin	Green walnuts
Flowery	No reference used
Astringent	No reference used
Spicy	No reference used
Earthy	No reference used

Statistical Analysis

GC/MS and descriptive flavour profile analysis were performed in triplicates for each sumach sample. Differences between samples according to the common volatiles detected by GC/MS and common characters identified by sensory flavour profile analysis were evaluated by Least Significant Difference (LSD) test at 99 % confidence level.[27]

RESULTS AND DISCUSSION

GC/MS Analysis

Tables 2, 3, and 4 show that a total of 54, 27, and 17 signals were identified in the studied sumach samples by liquid-liquid extraction, SC-CO₂ and distillation techniques, respectively. The major volatiles detected in liquid-liquid extraction were malic acid (sour), β-caryophyllene (spicy, woody), N-nonadecane (kerosene), succinic acid (acidic), phenol (medicinal-astringent), cembrene (woody, spicy), trans-2,4-decadienal (geranium), hexadecanoic acid (oily), stearic acid (oily), octadecane, decane, undecane, eicosanoic acid (oily), 9-octadecanoic acid (oily), hexadecanoic acid ethyl ester (oily), (z)-cis (α-bergamoten, and linoleic acid (oily). Total peak area of the mentioned volatiles was calculated to be approximately 78%. N-nonadecane, phenol, octadecane, β-caryophyllene, cembrene, hexadecanoic acid, caryophyllene oxide (spicy), eicosanoic acid and linoleic acid were observed to be the major volatiles by SC-CO₂ technique, whereas β-caryophyllene, malic acid, cembrene, caryophyllene oxide, α-pinene (pine, resinous), and α-humulene (woody) are the main volatiles detected by the distillation technique. Total peak area of the mentioned volatiles determined by SC-CO₂ and distillation techniques were 86 and 51%, respectively. β-caryophyllene, caryophyllene oxide, caryophyll 4(12), cembrene, α-humulene, 2-pentadecanone and farnesol (oily) were found to be common volatiles by using the three isolation techniques. Cembrene and β-caryophyllene were also detected at significant amounts in Sumach from Diyarbakır province of Turkey in the study conducted by Brunke et al.[2] The differences between the percentages of common compounds in sumach samples detected by three techniques were found to be statistically significant (p ≤ 0.01) for 2-pentadecanone, α-humulene and β-caryophyllene. Volatiles such as limonene (citrus) and α-pinene (pine, resinous) were only detected by using distillation and liquid-liquid extraction techniques in the present study. Brunke et al.[2] also revealed high quantities of monoterpene hydrocarbons such as limonene and α-pinene in sumach essential oil isolated by steam distillation.

Table 2 Volatile compounds in sumach isolated by liquid-liquid extraction technique and detected by GC/MS

Retention time	Volatile compounds	% Area
5.843	α-Pinene	0.13 ± 0.02
6.045	2,5 Furandion, 3-methyl	0.64 ± 0.06
7.824	Decane	1.55 ± 0.01
8.740	Benzene	0.09 ± 0.01
8.887	1-Limonene	0.08 ± 0.01
9.382	Limonene	0.15 ± 0.01
9.529	2,5 Furandion, dehydro 3-methyl	0.19 ± 0.02
9.987	Benzene, 1-ethyl-2,3-dimethyl	0.16 ± 0.02
10.152	Hexane	0.68 ± 0.03
10.519	Undecane	1.51 ± 0.12
10.677	Nonanal	0.52 ± 0.14
10.849	Naphthalene	0.09 ± 0.03
11.857	Azulene	0.07 ± 0.01
12.444	Succinic acid	6.74 ± 0.83
12.792	Dodecane	0.21 ± 0.02
12.920	2-Decanal, (E)	0.25 ± 0.02
13.122	Nonanoic acid	0.37 ± 0.01
13.764	Trans-2,4-decadienal	2.91 ± 0.26
14.937	Malic acid	23.42 ± 6.58
15.872	2-Undecanal	0.16 ± 0.01
16.349	β-Caryophyllene	11.51 ± 0.01
16.642	(z)-cis (α-Bergamoten	1.25 ± 0.03
17.192	α-humulene	0.69 ± 0.03
17.999	Hexadecane	0.15 ± 0.01
18.531	2-Butendioic acid	0.98 ± 0.02
20.291	Caryophyllene oxide	0.64 ± 0.04
22.069	Caryophyll 4 (12)	0.13 ± 0.02
24.636	Tetradecanoic acid	0.28 ± 0.02
25.314	Octadecane	0.05 ± 0.0
26.066	2-Pentadecanone	0.26 ± 0.01
26.414	Pentadecanoic acid	0.09 ± 0.01
27.313	2-Heptadecanone	0.23 ± 0.01
27.459	Farnesol	0.11 ± 0.01
27.679	Cembrene	3.32 ± 0.12
28.834	Hexadecanoic acid	2.86 ± 0.42
29.164	Hexadecanoic acid, ethyl ester	1.41 ± 0.06
31.163	Camphen	0.09 ± 0.01
31.914	7,10 Hexadecadienoic acid	0.38 ± 0.07
32.061	Linoleic acid	1.00 ± 0.13
32.538	9-Octadecanoic acid	1.49 ± 0.22
34.738	Ethyl linoleate	0.17 ± 0.02
36.039	Octadecanoic acid	2.34 ± 0.44
36.333	1-Octadecene	0.41 ± 0.08
36.425	Tricosane	0.15 ± 0.03
37.689	1-Pentadecene	0.05 ± 0.01
38.056	Eicosanoic acid	1.51 ± 0.27
38.460	Tetracosane	0.48 ± 0.10
39.211	5-Eicosene, (E)	0.51 ± 0.13
40.091	Heptadecene-(8)-carbonic acid	0.05 ± 0.01
41.173	Phenol	5.07 ± 1.13
42.768	1,2-Benzendicarboxylic acid	0.62 ± 0.17
44.913	N-nonadecane	9.17 ± 2.45
50.560	Octadecane	1.59 ± 0.47
59.727	Hexadecane, 2,6,11,15-tetra methyl	0.17 ± 0.06

Table 3 Volatile compounds in sumach isolated by SC-CO₂ extraction technique and detected by GC/MS

Retention time	Volatile compounds	A (% Area)
12.205	Succinic acid	0.32  ± 0.04
12.700	Dodecane	0.21  ±  0.05
13.709	Trans-2,4-decadienal	0.21  ±  0.06
16.239	β-Caryophyllene	5.03  ±  0.73
17.137	α-humulene	0.16  ±  0.03
20.236	Caryophyllene oxide	1.83  ±  0.37
21.556	Caryophyll 4 (12)	0.14  ±  0.01
26.011	2-Pentadecanone	0.17  ±  0.04
27.257	2-Heptadecanone	0.10  ±  0.02
27.404	Farnesol	0.11  ±  0.01
27.587	Sembrene	2.49  ±  0.74
28.669	Hexadecanoic acid	1.94  ±  0.43
31.786	7,10 Hexadecadienoic acid	0.36  ±  0.09
31.951	Linoleic acid	1.26  ±  0.25
32.391	9-Octadecanoic acid	0.82  ±  0.13
34.683	Ethyl linoleate	0.11  ±  0.02
35.874	Octadecanoic acid	0.97  ±  0.07
36.498	Tricosane	0.10  ±  0.01
37.763	1-Pentadecene	0.15  ±  0.01
37.983	Eicosanoic acid	1.83  ±  0.08
38.386	Tetracosane	0.62  ±  0.04
39.083	5-Eicosene, (E)	0.12  ±  0.01
41.100	Phenol	17.16  ±  0.2
42.676	1,2-Benzendicarboxylic acid	1.55  ±  0.01
44.858	N-nonadecane	46.83  ±  1.1
50.413	Octadecane	8.12  ±  0.42
59.415	Hexadecane, 2,6,11,15-tetra methyl	0.54  ±  0.04

Table 4 sisolated by distillation technique and detected by GC/MS

Retention time	Volatile compounds	% Area
6.057	α-Pinene	0.94  ±  0.01
9.980	Limonene	0.36  ±  0.02
10.860	Nonanal	0.05  ±  0.01
12.024	Trans-2-nonenal	0.32  ±  0.05
12.840	α-terpineol	0.07  ±  0.02
13.362	Decanal	0.32  ±  0.12
14.536	2-Decanal, (E)	0.12  ±  0.04
15.609	Malic acid	13.86  ±  2.61
16.929	β-Caryophyllene	28.52  ±  0.23
17.570	α-humulene	0.86  ±  0.02
18.946	2-Butendioic acid	0.32  ±  0.01
20.522	Caryophyllene oxide	1.8  ±  0.06
22.612	Caryophyll 4 (12)	0.47  ±  0.08
24.922	Tetradecanoic acid	0.13  ±  0.05
26.187	2-Pentadecanone	0.55  ±  0.01
27.507	Farnesol	0.11  ±  0.01
27.948	Sembrene	4.96  ±  0.18

It can be observed from the Table 3 that the numbers of volatiles isolated by SC-CO₂ extraction are lower in comparison with the liquid-liquid extraction technique. This result can be due to the lack of entrainer port in the SC-CO₂ apparatus used in the present study Thus, apolar compounds could be easily extracted by CO₂, whereas polar volatiles could not be detected. In a study conducted on the yield of total valerinic acids from valerian root, it was detected that the same amount of valerinic acid obtained by addition of 5% methanol or ethanol as entrainer to the supercritical CO₂ extraction resulted in the same yield as percolation (liquid extraction).[28] Further studies by using methanol or ethanol as entrainers can also be conducted for improving the conditions during SC-CO₂ extraction of sumach volatiles.

Sensory flavour profile analysis showed that (Table 5 and Figure 1) oil and acidic aroma and dried lemon balm, cellulose/woody, spicy, earthy and astringency flavour descriptors were detected in all 3 samples (grinded sumach sample, SC-CO₂ extract, and water extract of sumach) examined in the study. Results of variance analysis and LSD test demonstrated that there were significant (p ≤ 0.01) differences between the samples according to the common sensory characters perceived. Beside the common characters, grinded sumach sample involved henna odour, dried basil, green walnut skin, flowery, sour, tobacco, oleastar, and oily flavour descriptors. Grape molasses odour was detected only in water-extract of sumach, while medicinal odour was detected only in SC-CO₂ extract. The medicinal odour perceived in the SC-CO₂ extract can be the result of the high percentage of phenol (%17.16) as detected by GC/MS (Table 2). Malic acid, the component that is responsible from the sour taste of sumach fruit was detected at a significant level in liquid-liquid isolation technique and distillation techniques (Table 2), whereas this volatile could not be observed by SC-CO₂ extraction. Sour character was not observed in SC-CO₂ extract during sensory analysis (Table 5, Figure 1) as well.

Figure 1 Flavour profiles of grinded sumach, SC-CO₂ and water extracts of sumach.

Table 5 Sensory characters of sumach samples and mean intensity scores

	Grinded sumach	SC-CO2 extract	Water extract
Odour notes
Henna	2.1	3.3	0
Oil	1.1	1.6	0.5
Medicinal	0	0.8	0
Acidic	0.8	0.3	0.4
Grape molasses	0	0	1.1
Flavour notes
Green walnut skin	0.9	0.1	0
Flowery	0.7	0.1	0
Dried basil	1.4	0.8	0
Dried lemon balm	0.3	0.8	0.4
Sour	4.2	0	4.8
Cellulose/Woody	3.1	2.2	3.1
Tobacco	0.1	0	0.1
Oleastar	1.1	0	0.4
Oily	1.1	4.2	0
Spicy	0.6	0.6	0.6
Earthy	1.7	1.7	1.3
Astringency	2.3	0.6	1.4

The evaluation of GC/MS and sensory data revealed some of the sumach volatiles responsible for specific aroma characters as acidic (succinic acid), flavour characters as; dried lemon balm (limonene and 1-limonene), sour (malic acid,) tobacco (azulene); flowery (2-decenal); cellulose/woody (cembrene, β-caryophyllene and α-humulene), spicy (caryophyllene oxide, β-caryophylene), oily (nonanal, linoleic acid, eicosanoic acid, farnesol), medicinal and astringent (phenol).

CONCLUSION

The isolation of volatiles in sumach by liquid-liquid extraction technique was observed to be more efficient than the other two techniques in terms of the number of volatiles determined. The volatiles that make up approximately 60% of sumach volatile oil determined by liquid-liquid extraction were malic acid (23.42%), β-caryophyllene (11.51%), N-nonadecanol (9.17%), succinic acid (6.74%), phenol (5.07%), and cembrene (3.32%). Among these volatiles, malic acid and succinic acid are used as acidity regulators; succinic acid is also added as a flavour enhancer to foods. Succinic acid had been used as a natural antibiotic while phenol is a carbolic acid that has been used as an antiseptic. Thus, the presence of these volatiles can have an important contribution to the medicinal effect of sumach, as well as to its flavour.

ACKNOWLEDGMENTS

The authors especially thank the TUBITAK Marmara Research Center, Food Institute employees for participating as panelists in this research.