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Communication

Characterization of the Volatile Substances and Aroma Components from Traditional Soypaste

1
Central Research Institute of Ting Hsin International Group, Tianjin 300457, China
2
College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China
*
Author to whom correspondence should be addressed.
Molecules 2010, 15(5), 3421-3427; https://doi.org/10.3390/molecules15053421
Submission received: 2 March 2010 / Revised: 9 April 2010 / Accepted: 21 April 2010 / Published: 11 May 2010

Abstract

:
In this study, the flavor substances of soypaste were extracted by a simultaneous distillation method and identified by GC-MS. The characteristic aroma components of soypaste were determined by the GC-O technique and the FD value of the characteristic aroma components was determined by AEDA method. It could be inferred that the aroma of the soypaste should be attributed to the presence of heterocyclic compounds and organic acids, with the heterocyclic compounds playing a prominent role.

1. Introduction

Soypaste is a kind of special seasoning produced by microbial fermentation using soybean and wheat flour as the main raw materials. Traditional soypaste has a unique aroma due to the natural fermentation production method. However, the production of the soypaste suffers from a long production cycle, high costs and low output. Many soypaste manufacturers use artificial fermentation installations and other industrial fermentation processes to expand the scale of production and reduce the cost, but significant differences in aroma are noted by the consumers, which has also become a major factor in markg acceptance. Thus, the aroma of soypaste is considered as one of the important indicators to evaluate the quality of soypaste.
Until recently, soypaste aroma research of was still in the development. The research was focused on the identification and the extraction methods of aroma components [1,2,3,4] and the results only showed the aroma substances in the samples by similar methods such as solid-phase micro-extraction and the direct distillation method, which could not further specify which were the main flavor ingredients. As a result, it was difficult to establish the industrial standard from the aspect of the characristic aroma and the functions of different favor components in traditional soypaste still could not be determined. In this study, the flavor substances of soypaste were extracted by simultaneous distillation method and identified by GC-MS. Then the characteristic aroma components in the soypaste were determined by the GC-O analysis technique and the FD values of the characteristic aroma components were measured by the AEDA method. The results obtained could be used to understand the aroma of traditional soypaste and help standardize the modern product of soypaste.

2. Results and Discussion

The GC profile of the volatile components extracted from the soypaste by SDE (simultaneous distillation and extraction) is shown in Figure 1. One hundred and eight eight components were detected in soypaste extracts, among which 103 compounds were identified by searching the MSDChem NIST02.1 MS library (similarity ratio >75%). Through the data processing system of the MSDChem ChemStation, the relative contents of the various components in the volatile oil were determined by the peak area normalization method and the identified compounds thus accounted for over 80% of the overall aroma components.
In accordance with the order of the peaks, the main identified compounds were as follows: 2-methyl propionaldehyde (0.6568%), ethyl acetate (0.9856%), 3-butyraldehyde (4.4674%), ethanol (16.0962%), 2-methyl-1-propanol (0.5181%), formic acid ester (0.1137%), heptanal (0.0137), iso-amyl alcohol (1.5799%), 2-pentylfuran (0.1063%), 2,5-dimethylpyrazine (0.2044%), 2,6-dimethylpyrazine (0.1038%), ethyl lactate (0.2514%), dimethyl trisulfide (0.1145%), 3-methylpyrazine (0.1862%), acetic acid (2.1983%), 3-methylthiopropionaldehyde (0.168%), furfural (7.5069%), 2-acetylfuran (0.2062%), benzaldehyde (0.9816%), 2-methylpropionic acid (0.9689%), 5-methylfurfural (0.7121%), phenyl-acetaldehyde (6.5578%), furfuryl alcohol (2.1997%), 3-methyl-pentanoic acid (7.0269%), ethyl phenylacetate (0.188%), guaiacol (0.6268 %), phenethyl alcohol (0.7545%), 2-acetylpyrrole (0.9778%), 4-ethylguaiacol (3.2858%), 4-ethylphenol (0.2072%) and palmitic acid ethyl ester (0.8126%).
In this study, 103 volatile compounds were identified in traditional soypaste, mainly esters, alcohols, aldehydes, acids, ketones, and heterocyclic compounds. The contents of alcohols and acids were the highest, followed by the contents of esters and aldehydes. Although the contents of alcohols were high, they had a relatively high threshold, which made their contribution to the flavor small. Esters were the main component present in the soypaste aroma volatile components, providing sweet bean paste, fruit fragrance, and a variety of floral aromas. The aldehydes and ketones had the lowest thresholds and produced fruit fragrances and nut aromas. The heterocyclic compounds were the main component of the cconstituted the main body of the baking aroma. High contents of some compounds such as ethyl acetate, benzoin aldehyde, 5-methylfurfural, benzene, acetaldehyde, furfural, 3-butyric aldehyde, 2,3,5-trimethylpyrazine, etc., some of which had been identified as flavor compounds, have been detected in the soypaste.
The characteristic aroma components of the soypaste were determined by the GC-O technique. During the GC-O analysis, there were three professional evaluators to detect 22 kinds of odor active volatile compounds (Log3 FD> 1). These compounds were classified according to the sequence in Table 1, Table 2, Table 3, Table 4 and Table 5. Many different odors were sniffed at the GC-O sniffing port, including coke flavor, fried potato flavor, fruit fragrance, flower fragrance, butter flavor and so on. All the compounds could be detected in GC-MS. The Log3 FD values of 18 compounds were more than 3. Of these 2,3,5-trimethyl-pyrazine (a strong aroma of fried potatoes), isovaleric (smelly sock smell), 4-ethylguaiacol (slightly sweet herbal incense), acetic acid Ding esters (strong fruit aroma), ethyl phenylacetate (similar to honey fragrant ester), phenethyl alcohol (sweet floral aroma), 3-methyl-pentanoic acid (sour herb smell, slightly green grass aroma), 2,6-dimethylpyrazine (roasted coffee, peanuts, potato aroma), furfural (sweet, roasted, woody), maltol (with butter, sugar, like a special focus fragrant aroma), lactic acid (mild cream aroma), benzaldehyde (bitter almond aroma), ethyl lactate (baked apple aroma), n-octanol (green fragrance, fruit, incense), 4-ethylphenol (phenolic wood aroma, slightly sweet aroma), 2,5-dimethyl-pyrazine (a strong focus scent), 2-acetylpyrrole (bread aroma) all had very high FD values (Log3 FD ≥ 4 ), which could account for the overall flavor of soypaste. Among them, the FD values of 2,3,5-trimethylpyrazine, isovalerate and 4-ethylguaiacol were as high as 2187 (Log3 FD = 7), which formed the bean flavor of the special paste aroma. According to the other similar studies [5], 2,3,5-trimethyl-pyrazine and 4-ethylguiacol were thought to be the characteristic compounds in the fermented bean aroma. It could be broadly inferred that the characteristic aroma of the soypaste should be attributed to the heterocyclic compounds and the organic acids. The role of heterocyclic compounds was particularly prominent, constituting the basis of the soy flavor. The results of this study should help us to control the fermentation process and improve the aroma of soypaste.

3. Experimental

3.1. Materials and chemicals

Soypaste was obtained from Fang Yuan Food Ltd. Company of Lan Yang City, Shang Dong Province. Other chemical were of analytical grade.

3.2. Fermentation process

After removing the impurities, the soybeans and wheat were cooked, cooled and mixed in a ratio of 6:4. The obtained mixture was used as the starter-material and fermented in a fermentation tank for six months. After the fermentation, it was collected as the soypaste.

3.3. SDE Preparation of aroma components from soypaste

The bean paste (200 g) was mixed with distilled water (300 mL) and a small amount of zeolite in a 1000 mL round-bottomed flask. The mixture was placed in a simultaneous distillation extraction instrument (Anhui Tianchang Excellent Letter Electrical Equipment Co., Ltd.) and extracted at 40 °C for 3 h. The extract was concentrated and dried by sodium sulfate for the subsequent GC-O and GC analysis.

3.4. Analysis of GC and GC-MS

GC-MS analysis was performed on an Agilent 6890NGC-5973IMS GC-MS. The gas chromatograph was equipped with a HP-INNO Wax Polyethylene Glycol capillary column 60 m × 0.25 mm coated with 0.25 μm film thickness. Carrier gas (helium) at flow rate of 1 mL/min. Column temperature program was 40 °C (3 min) isotherm, increased to 130 °C at a rate of 3 °C/min, maintained at 130 °C for 2 min, then increased to 200 °C at a rate of 4 °C/min and held at 200 °C for 5 min. The mass spectrometer was used in EI scan mode with a scan range of masses from 33 to 450 m/z. Ionization was set at 70 eV. Injector temperature was 250 °C. The compounds were identified by searching NIST02.1 database of the MSDChem workstation.
GC-O analysis was performed on an Agilent 7980 gas chromatograph interfaced to an ALPHA-MOS sniffer sniffing device (France ALPHA-MOS Corporation). The gas chromatograph was equipped with an Rtx-WAX capillary column 30 m × 0.25 mm coated with 0.25 μm film thickness (Agilent, USA). Carrier gas (helium) at flow rate of 1 mL/min. Column temperature program was 40 °C (3 min) isotherm, increased to 130 °C at a rate of 3 °C/min, maintained at 130 °C for 2 min, then increased to 200 °C at a rate of 4 °C/min and held at 200 °C for 5 min. The split ratio of the effluent into the FID and the ALPHA-MOS sniffer was 1:1.

3.5. Analysis of AEDA [6]

The extract was diluted according to the volume ratios of 1:3, 1:9, 1:81, 1:243, respectively. The obtained sample (2 μL) was injected for the GC-O analysis until the evaluators at the GC-O terminal could not feel the smell. The obtained highest dilution ratio was defined as the FD factor. There were three professional evaluators from Central Research Institute of Ting Hsin International Group who performed the AEDA.

4. Conclusions

In this study, the flavor substances of soypaste were extracted by simultaneous distillation method and subjected to standard analysis by GC-MS. The characteristic aroma components of soypaste were determined by the GC-O technique, and at the same time the FD values of the characteristic aroma components were determined by the AEDA method. The results could be used to evaluate the quality of soypaste.

References and Notes

  1. Yu, A.; Yang, C.; Han, D.; Han, K. Extraction Study on Aroma Compounds of Bacteria-fermented Soybean (in Chinese). Food Sci. 2002, 23, 98–100. [Google Scholar]
  2. Zhao, J.; Gu, X.; Liu, Y.; Wang, Li. Study on the volatile flavor compounds of the traditional Chinese soybean paste (in Chinese). Food Sci. 2006, 27, 684–687. [Google Scholar]
  3. Qin, L.; Ding, X. Investigations on the volatile flavor compounds in the traditional long-ripenned Douchiba (DCB) and the Mold-fermented Douchi (DC) (in Chinese). Food Sci. 2005, 26, 275–280. [Google Scholar]
  4. Giri, A.; Osako, K.; Okamoto, A.; Ohshima, T. Olfactometric characterization of aroma active compounds in fermented fish paste in comparison with fish sauce, fermented soy paste and sauce products. Food Res. Int. 2010, in press. [Google Scholar] [CrossRef]
  5. Seo, J.; Chang, H.; Ji, W.; Lee, E.; Choi, M.; Kim, H.; Kim, J. Aroma Components of Traditional Korean Soy Sauce and Soybean Paste Fermented with the Same Meju. J. Microbiol. Biotechn. 1996, 6, 278–285. [Google Scholar]
  6. Grosch, W. Detection of potent odorants in food by aroma extract dilution analysis. Trends Food Sci. Technol. 1993, 4, 68–73. [Google Scholar] [CrossRef]
Sample Availability: Samples of the compounds are available from the authors.
Figure 1. GC profile of the volatile components extracted from the soypaste by SDE.
Figure 1. GC profile of the volatile components extracted from the soypaste by SDE.
Molecules 15 03421 g001
Table 1. Aldehyde and ketone components from the volatile compounds of soypaste.
Table 1. Aldehyde and ketone components from the volatile compounds of soypaste.
NameRISmell descriptionLog3 FD
WAXDB-5
12-Butyraldehyde910650Nut odor1
23-Butyraldehyde914664Apple odor3
3Hexanal1074809Aldehyde odor<1
4Heptaldehyde1174909Fruit flavor, rose oil odor, perilla oil odor3
55-n-Octyl aldehyde12781014Fruits, fat aroma and citrus odor<1
6Nonanal13801102Citrus and vinegar smell2
73-Methylthiopropionaldehyde1392925Potato and sauce smell2
8Furfural1442841Sweet, roasted, woody, bread aroma5
9Benzaldehyde1498966Bitter almonds, woody odor4
105-Methylfurfural1014771Thick, sweet, spicy odor,2
11Phenylacetaldehyde16231059Ocean narcissus elegant aroma, a strong wind letter sub-aroma, cherry flavor2
122,3-Butanedione973606Sweet cream, butter aroma3
132,3-Pentanedione1074702Sweet odor, cream odor.2
143-Penten-2-one1121Fruit and spicy aroma<1
Table 2. Alcohol or phenolic components from the volatile compounds of soypaste.
Table 2. Alcohol or phenolic components from the volatile compounds of soypaste.
NoNameRISmell descriptionLog3 FD
WAXDB-5
1Ethanol930 2
2iso-propyl carbinol1080Artificial musk aroma<1
33-Methylbutanol1205739Wines and ether smell<1
4Hexanol1349889Fruit flavor<1
51-Octen-3-ol1443978Mushrooms, lavender, rose and hay aroma2
6Octanol15501086Citrus, sweet orange, aldehydes fragrant, sweet floral, fragrant aroma and green incense4
7Furfuryl alcohol1660Bitter and spicy smell2
83-Methylthiopropanol14361099A strong aroma and taste of meat and broth, a strong smell of garden onions and meat, butter flavor when diluted1
92-Methoxyphenol, guaiacol18591102Aromatic smell<1
10Phenylethanol18851131Sweet, floral aroma, and fruit, fat taste, rose aroma6
11Phenol1920Special smell, sweet smell<1
124-Ethyl-2-methoxyphenol,2032Barbecue flavour7
134 - Ethylphenol2086Wood phenol aroma, slightly sweet aroma4
14Maltol19681108butter, sugar, coke special aroma incense, strawberry flavor5
Table 3. Ester components in the volatile compounds of soypaste.
Table 3. Ester components in the volatile compounds of soypaste.
NoNameRISmell descriptionLog3 FD
WAXDB-5
1Ethyl acetate885<600Ether fragrance, sweet fruit such as pineapple3
2Ethyl 2-methylbutyrate1051845Strong apple skin, pineapple skin and immature sweet aroma of plum skin<1
3n-Butyl acetate1070820Strong fruit aroma, similar to pear, banana aroma6
4Ethyl 3-methylbutyrate1134Similar to apple, bananas aromas and sweet and sour smell<1
5Ethyl caproate1235996Fragrant fruits like pineapple and wine4
6Ethyl lactate1293825Sweet, fruit, roasted, old rum aroma, wine aroma
7Octanoic acid ethyl ester14311209Brandy aroma, wax incense, milk and cream, fruit, wine<1
8Ethyl benzoate16471188Fruit, medicine fragrant aroma1
9Ethyl phenylacetate17651258Strong and sweet fragrance of honey. Significant and sweet incense rose6
10Ethyl palmitate>2000Incense wax smell, butter aroma2
Table 4. Heterocyclic components in the volatile compounds of soypaste.
Table 4. Heterocyclic components in the volatile compounds of soypaste.
NoNameRISmell descriptionLog3 FD
WAXDB-5
12-Pentylfuran1225996bean aroma, fruity, green fragrance, vegetables, fragrant soil, root incense aroma2
22,5-Dimethylpyrazine1316925Pungent aroma of fried flowers and chocolate, butter odor, roasted barley aroma, fried potatoes, fried potato chips4
32,6-Dimethylpyrazine1319925Roasted, coffee, peanuts, potato aroma and chocolate flavor6
42,3,5-Trimethyl-pyrazine1391999Baked goods, roasted barley, cocoa, coffee and pork, beef, popcorn, baked potatoes, roasted peanut odor7
53-Ethyl-2, 5-dimethyl- pyrazine14391071Fried barley, cocoa products, coffee, peanut, hazelnut, soybean odor3
62-Acetylfuran1497Almonds, nuts, fermented aroma, milk and sweet caramel-like aroma1
71-Methoxy-4-(1- propenyl)-benzene, anethole16821244A special aroma of fennel<1
82-Acetylpyrrole1952Bread aroma, bakery aroma4
Table 5. Acidic components from the volatile compounds of soypaste.
Table 5. Acidic components from the volatile compounds of soypaste.
NoNameRISmell descriptionLog3 FD
WAXDB-5
1Acetic acid1413671Acetic, vinegar odor2
22-Methylpropionic acid1468Pungent odor, rancid oil odor 3
3Butyric acid1546Milk, cream, butter, cheese, fruity aroma2
43-Methylpentanoic acid1597882Sour herbal aroma, slightly green grass aroma6
5Isovaleric acid1638966Old sock odor7
6Hexanoic acid18261209Strong rancid cheese aroma 1
7Lactic acid>20001296Mild and pleasant cheese aroma5
8Nonanoic acid>20001308Fats, wax, cheese, coconut fragrance<1

Share and Cite

MDPI and ACS Style

Zhang, Y.; Li, X.; Lo, C.-K.; Guo, S.-T. Characterization of the Volatile Substances and Aroma Components from Traditional Soypaste. Molecules 2010, 15, 3421-3427. https://doi.org/10.3390/molecules15053421

AMA Style

Zhang Y, Li X, Lo C-K, Guo S-T. Characterization of the Volatile Substances and Aroma Components from Traditional Soypaste. Molecules. 2010; 15(5):3421-3427. https://doi.org/10.3390/molecules15053421

Chicago/Turabian Style

Zhang, Yan, Xin Li, Chih-Kang Lo, and Shun-Tang Guo. 2010. "Characterization of the Volatile Substances and Aroma Components from Traditional Soypaste" Molecules 15, no. 5: 3421-3427. https://doi.org/10.3390/molecules15053421

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