RAW-MATERIAL CONCENTRATE WITH ENHANCED FLAVOR AND PREPARATION METHOD THEREFOR

Abstract

The present application relates to a raw-material concentrate with enhanced flavor and a novel preparation method therefor. According to the preparation method of the present application, it is possible to provide a raw-material concentrate that has a high extraction yield of active ingredients extracted from raw materials and is economical, and has good flavor as well as less nutrition destruction, and thus has excellent productivity. This raw-material concentrate can be utilized as a food material.

Claims

1. A method for preparing a raw-material concentrate, the method comprising: concentrating raw-material juice by thin-film concentration; and concentrating the thin film-concentrated raw-material juice by plate-concentration.

2. The method of claim 1, wherein the solid content of the raw-material juice after the thin film-concentration is 20 Brix° to 50 Brix°.

3. The method of claim 1, wherein the solid content of the prepared raw-material concentrate is 60 Brix° or more.

4. The method of claim 1, wherein the raw material is at least one selected from the group consisting of fruits, fruit vegetables, and vegetables.

5. The method of claim 1, wherein the method increases the content of a sulfur-containing compound through the thin film-concentration and the plate-concentration, and inhibits the generation of a furan-based compound or a pyrazine-based compound.

6. The method of claim 1, wherein the thin film-concentration is performed through heat treatment such that an evaporation temperature reaches 20° C. to 50° C.

7. The method of claim 1, wherein the plate-concentration is performed through heat treatment such that an evaporation temperature reaches 30° C. to 35° C.

8. The method of claim 1, wherein the raw-material juice has a turbidity of 1600 NTU or less with respect to the solid content of 7 to 8 Brix°.

9. An onion concentrate containing 600 μg/ml or more of thiosulfinate.

10. The onion concentrate of claim 9, wherein the onion concentrate comprises 600 μg/ml or more of thiosulfinate with respect to the total solid content of 60 Brix°.

11. The onion concentrate of claim 9, wherein the onion concentrate comprises at least one compound selected from the group consisting of dimethyltrisulfide, methylpropyltrisulfide, and 1,3-dithiane.

12. The onion concentrate of claim 11, wherein in the onion concentrate, when measured through GC/MS, the content of at least one furan-based compound selected from the group consisting of 3-methylfuran, 2-methylfuran, 2-ethylfuran, 2,5-dimethylfuran, and 2-(1-pentenyl)furan is 0.1 parts by weight or less with respect to 100 parts by weight of an onion concentrate volatile component, or the content of at least one pyrazine-based compound selected from the group consisting of methylpyrazine, 2,6-dimethylpyrazine, and 2-ethenyl-6-methylpyrazine is 0.1 parts by weight or less with respect to 100 parts by weight of an onion concentrate volatile component.

13. A food comprising the onion concentrate of claim 9.

14. A method for enhancing the flavor of a raw-material concentrate, the method comprising: concentrating raw-material juice by thin-film concentrating; and concentrating the thin film-concentrated raw-material juice by plate-concentration.

15. The method of claim 14, wherein the raw-material concentrate is an onion concentrate.

16. A food comprising the onion concentrate of claim 10.

17. A food comprising the onion concentrate of claim 11.

18. A food comprising the onion concentrate of claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0103] FIG. 1 shows a configuration of preparation processes of onion juice according to an example embodiment of the present application.

MODE FOR CARRYING OUT THE INVENTION

[0104] Hereinafter, the present invention will be described in more detail with reference to the following Examples. However, these Examples are for illustrative purposes only to describe the present invention, and are not intended to limit the scope of the present invention.

Preparation Example 1. Preparation of Raw-Material Juice

[0105] 1-1 Preparation of Raw Material

[0106] Raw-material onions harvested from Jeju Special Self-Governing Province were purchased and used. Peeled onions were washed in running water until dirt was completely removed, then packaged and kept refrigerated at 10° C. or less to use the onions as raw materials.

[0107] 1-2 Pretreatment and Juicing

[0108] The initial number of bacteria was controlled by treating the raw-material onions with non-acidic electrolyzed water (HOCl, pH 5.0, 20 ppm) for 30 minutes instead of heating the raw-material onions to keep the flavor of fresh onions. Next, the raw-material onions were primary-crushed and juiced using a juicer (HSJ-120, HANSUNG Co., Kr) to prepare raw-material juice.

[0109] 1-3 Filtration Process

[0110] A two-step filtration process of primary filtration using a filter press (JUNGDO 1000, JUNGDO Co., Kr) and secondary filtration using a 5 μm MF filter was performed to effectively remove impurities of various sizes in the raw-material juice.

[0111] Specifically, 5 wt % of diatomaceous earth was added to the raw-material juice with respect to the total weight of the raw-material juice to cause mucous polysaccharide materials to agglomerate on the diatomaceous earth, and then the resultant was filtered through filter press cloth (15 cc) to remove low molecular weight fibers. The raw-material juice subjected to the primary filtration was subjected to secondary filtration using a 5 μm MF filter to further remove residual diatomaceous earth and fine substances, thereby preparing the raw-material juice in a clarified state.

[0112] 1-4 Measurement of Turbidity

[0113] The turbidity of the filtered raw-material juice was measured to check how much suspended matters were removed after the filtration process. Specifically, the turbidity was measured using a turbidimeter (HACH 2001N TURBIDIMETER).

[0114] The concentration of the raw-material juice after the two-step filtration process of the present invention was maintained at a low level of 7.3 Brix° and turbidity of 154 NTU.

[0115] 1-5 Quick Freezing and Storage

[0116] The filtered raw-material juice was cooled to 20° C. or lower, packaged by 15 kg each, and then quick-frozen at 18° C. or lower and stored.

Examples 1 to 4. Combined Process in which Thin Film-Concentration Process and Plate-Concentration Process are Linked

[0117] The raw-material onion juice prepared through the method of Preparation Example 1 was concentrated using a combination of a thin film-concentration method and a plate-concentration method.

[0118] Specifically, a centrifugal thin film concentrator (CEP-1, OKAWARA CO., Japan) was set to an evaporation temperature of 30° C. to 35° C., a heating medium temperature of 100° C., a vacuum degree of 4.0 kPa, and a drum speed of 1500 rpm for optimization.

[0119] Initial onion juice was concentrated up to the solid content of 20 Brix° (Example 1), 30 Brix° (Example 2), 40 Brix° (Example 3), and 50 Brix° (Example 4). The above process was repeated up to a target concentration.

[0120] Thereafter, the plate-concentration was optimized at an evaporation temperature of 30° C. to 35° C., a heating medium temperature of 60° C. or less, and a vacuum degree of 2.0 kPa, and performed up until the concentration of a finally prepared onion concentrate reached 60 Brix°.

[0121] The finally prepared raw-material onion concentrate was stored at 20° C. or less, and the content of active ingredients and main quality characteristics according to the concentration methods and concentration conditions were checked.

Comparative Example 1. General Vacuum Concentration Process

[0122] A raw-material onion concentrate was prepared using a general concentrate preparation method.

[0123] Raw-material onion juice was prepared by heat-juicing. Specifically, the same raw material as in Preparation Example 1-1 was extracted at 90° C. to 100° C. for 60 minutes, and then subjected to filtration (80 mesh), cooling (20° C. or less), packaging, and quick freezing (−18° C. or less) to prepare raw-material onion juice. The juice had a concentration of 7.7 Brix° and a turbidity of 549 NTU.

[0124] The prepared onion raw-material juice was vacuum-concentrated using a commonly used batch-type vacuum concentrator (PILOT, Seo kang, Co., Kr). Specifically, the vacuum concentrator was set to an evaporation temperature of 45° C. to 50° C., a heat medium temperature of 60° C. or higher, and a vacuum degree of 9.0 kPa, and then the prepared raw-material onion juice was stirred to prepare raw-material onion concentrate.

Comparative Example 2. Optimized Thin Film-Concentration Process

[0125] The raw-material onion juice prepared through the method of Preparation Example 1 was put into a centrifugal thin film concentrator to obtain a raw-material onion concentrate.

[0126] Equipment using a centrifugal thin film concentrator, temperature, and the like were set in the same manner as in Example, and the concentrate was recycled until the concentrate reached a concentration of 40 Brix° to prepare a raw-material onion concentrate.

Comparative Example 3. Optimized Plate-Concentration Process

[0127] The raw-material onion juice prepared through the method of Preparation Example 1 was put into a plate-concentrator to obtain a raw-material onion concentrate.

[0128] Specifically, the plate-concentration process was performed under the same conditions in equipment and temperature as in Example, and a raw-material onion concentrate of 60 Brix° was prepared.

[0129] That is, Comparative Example 3 skipped thin film-concentration process unlike Example.

Experimental Example 1 Observation of Changes in Turbidity, Browning, and pH of Raw-Material Concentrates According to Concentration Process

[0130] Changes in turbidity, browning, and pH of various raw-material onion concentrates prepared through the methods of Examples and Comparative Examples were checked.

[0131] Turbidity was measured using a turbidimeter (HACH 2100N TURBIDIMETER), and browning was measured using a spectrophotometer (U-2900, HITACHI, Co., Japan) for absorbance at 420 nm, and pH was measured using a pH meter (METTLER TOLEDO).

TABLE-US-00001 TABLE 1 Turbidity Browning Concentration method (NTU) (Abs) pH Comparative Example 1 1778 2.051 5.39 (Vacuum Concentration, 60 Brix°) Comparative Example 2 1283 1.554 5.60 (Thin film-concentration, 40 Brix°) Comparative Example 3 1120 1.896 5.36 (Plate-concentration, 60 Brix°) Example 1 (20 Brix°->60 Brix°) 814 1.875 5.43 Example 2 (30 Brix°->60 Brix°) 960 1.897 5.59 Example 3 (40 Brix°->60 Brix°) 1050 1.920 5.59 Example 4 (50 Brix°->60 Brix°) 1394 1.965 5.39

[0132] As shown in Table 1, the results indicated that turbidity and browning changed depending on concentration methods, and the combined concentration (Examples 1 to 4) had a decrease in turbidity and browning compared to vacuum concentration (Comparative Example 1), which is a conventional concentration method.

Experimental Example 2. Observation of Changes in Chromaticity of Raw-Material Concentrate According to Concentration Process

[0133] The chromaticity of various raw-material onion concentrates prepared through the methods of Examples and Comparative Examples was measured through Hunter's method.

[0134] In the chromaticity measurement of raw-material concentrates, lightness (L, lightness), redness (a, redness), yellowness (b, yellowness), and ΔE values indicating overall color difference were measured using a colorimeter (SA-2000, NIPPON Denshoku Co., Japan), and the measurement was repeated three times for each sample and expressed as an average value. The standard white plate used for this measurement had an L value of 98.01, an a value of 2.27, and a b value of 1.13.

TABLE-US-00002 TABLE 2 Concentration method L a b ΔE Comparative Example 1 6.41 4.31 4.02 78.02 (Vacuum Concentration, 60 Brix°) Comparative Example 2 41.93 4.46 9.54 42.69 (Thin film-concentration, 40 Brix°) Comparative Example 3 9.75 2.93 5.43 76.20 (Plate-concentration, 60 Brix°) Example 1 (20 Brix°->60 Brix°) 11.41 3.66 6.45 74.12 Example 2 (30 Brix°->60 Brix°) 10.06 3.05 5.56 75.49 Example 3 (40 Brix°->60 Brix°) 9.52 3.23 5.42 76.04 Example 4 (50 Brix°->60 Brix°) 7.51 2.24 4.27 78.08

[0135] As shown in Table 2, the results indicated that the raw-material concentrates (Examples 1 to 4) prepared through the combined concentration had higher brightness, lower redness, higher yellowness, and relatively lower ΔE value indicating the overall color difference than that of the conventional concentration method (Comparative Example 1). The lower the ΔE value, the less the color deviation, and the higher the DE value, the greater the deviation, and thus the results indicate that the raw-material concentrates prepared through the combined concentration had less changes in color upon the concentration process.

Experimental Example 3. Observation of the Content of Each Amino Acid by Type in Raw-Material Concentrate According to Concentration Process

[0136] The content of amino acid in various raw-material onion concentrates prepared through the methods of Examples and Comparative Examples was analyzed and is shown in Table 3 below.

[0137] For amino acid content analysis, 9.9 mL of distilled water was added to 0.1 mL of a sample solution, thoroughly mixed, and centrifuged (10,000 rpm, 10 min, 4° C.), and the resultant supernatant was filtered using a 0.25 μm syringe filter. Measurement of amino acid for the filtrate was analyzed using a High Speed Amino Acid Analyzer (L-8900, Hitachi Co., Japan).

[0138] For the analysis, a 2622SC-PH ion exchange column (4.6×60 mm, Hitachi, Co., Japan) was used as a column. A mobile phase was set to gradient mode, and in Pump1, sodium acetate buffer (MCI buffers PH1, PH4, RG) was used at a column temperature of 57° C. and a flow rate of 0.4 mL/min, and in Pump 2, a ninhydrin solution (R1 and R2) was used at a flow rate of 0.35 mL/min. 10 μL of injection volume was injected and as for a detector, Channel 1:UV-570 nm and Channel 2:UV-440 nm were used as dual channels for analysis.

TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Element Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Example 4 Aspartic ND ND ND ND ND ND ND acid Serine 547.2 384.0 457.3 565.2 299.5 ND 560.8 Glutamic 1806.3 1355.3 1556.6 2037.3 1907.6 1907.2 1808.1 acid Glycine 86.5 59.9 64.0 53.9 89.2 82.9 68.7 Alanine 658.0 465.7 532.2 625.9 748.0 734.8 655.7 Cysteine ND ND ND ND ND ND ND Valine 347.7 289.1 310.0 358.2 362.3 342.7 376.1 Methionine 75.5 75.5 66.8 30.2 68.4 61.2 48.7 Isoleucine, 168.2 120.8 138.2 184.2 149.9 136.4 199.5 Leucine 517.3 397.0 445.4 476.3 526.8 497.7 591.8 Tyrosine 396.3 302.5 318.9 390.7 353.3 337.4 407.4 Phenylalanine 436.9 297.4 342.4 300.1 361.2 345.8 411.4 Lysine 787.5 631.5 751.9 859.7 735.3 237.4 947.4 Histidine 161.0 121.1 150.4 185.7 204.3 197.2 204.1 Arginine 4825.9 3431.7 4142.3 5235.6 5557.6 5376.9 5441.8 Total 10814.3 7931.3 9276.4 11134.0 11363.2 10257.6 11721.5 (Unit: mg/L)

[0139] As shown in Table 3, the results indicated that the raw-material concentrates prepared through the combined concentration, had a greater content of amino acid in total than the conventional concentration method (Comparative Example 1) and the single concentration (Comparative Examples 2 and 3).

[0140] In addition, it was confirmed that, compared to Comparative Examples, Examples showed a decrease in the content of phenylalanine, which gives a bitter taste and an increase in the content of glutamic acid, which gives a savory taste in the raw-material concentrates to enhance the flavor of the raw-material concentrates, and Examples showed an increase in the content of histidine and arginine, which are antioxidants, in the raw-material concentrates. The changes in the content of these amino acid components seem to indicate that some heat-labile amino acids are continuously exposed to heat to react with other components or decompose to produce volatile flavor components, or to be converted into other types of amino acids, and it seems that the increase in the content of some amino acids is caused by the release of amino acids that are not sufficiently released during the concentration process.

Experimental Example 4. Observation of Flavor Enhancement Index Component in Raw-Material Concentrate According to Concentration Process

[0141] Pyruvic acid, which is a pungent indicator component of garlic and onion, is lost by heat, and thiosulfinate, a sulfur-containing compound of onion and an antioxidant, is also known to decrease its characteristic component by heat. The content of thiosulfinate and pyruvic acid in various raw-material onion concentrates prepared through the methods of Examples and Comparative Examples was analyzed and is shown in Table 4 below.

[0142] Measurement of the Content of Thiosulfinate

[0143] 0.5 mL of 50 mM N-(2-Hydroxyethyl)piperazine-N′-(2-ethane sulfonic acid) (HEPES, pH 7.5, Sigma, U.S.A.) including 2 mM cysteine (Sigma, U.S.A.), 0.1 mL of an extract, and 4.4 mL of 50 mM HEPES were mixed to make a total of 5 mL (0.2 mM cysteine/mL) subjected to a reaction at 27° C. for 10 minutes, thereby collecting 1 mL, and then 1 mL of 0.4 mM 5,5′-dithio-bis(2-nitrobenzoic acid) (DTNB, Sigma, U.S.A.) prepared with 50 mM HEPES buffer (pH7.5) was added thereto and subjected to a reaction at 27° C. for 10 minutes to measure absorbance at 412 nm, thereby identifying the content of residual cysteine. The standard curve was plotted by mixing 1 mL of 0.05 to 0.3 mM cysteine prepared with 50 mM HEPES buffer (pH 7.5) and 1 mL of 0.4 mM DTNB to make the mixture react at 27° C. for 10 minutes, thereby measuring absorbance at 412 nm. The content of cysteine was identified from the standard curve to see the total content of thiosulfinate through [Equation 1], and in a control group, a buffer solution was added instead of an extract solution to develop color, and samples affected by pigment were measured by adding the extract solution of the samples instead of DTNB, which is a coloring agent, and subtracted from the absorbance in which the samples were added and reacted.

Total thiosulfinate (mM/mL)=[Ab−(As−Ac)]×25  [Equation 1]

[0144] Ab: Content of cysteine in control group (mM/mL)

[0145] As: Content of cysteine with extract solution (mM/mL)

[0146] As: Content of cysteine affected by pigment contained in extract solution (mM/mL)

[0147] Measurement of the Content of Pyruvic Acid

[0148] 4 mL of 0.0125% DNPH (2,4-dinitrophenylhydrazine) was added to 80 μL of supernatant of a raw onion concentrate, and the mixture was shaken, and subjected to a reaction at 37° C. for 10 minutes. 8 mL of 0.6 N NaOH solution was added to measure absorbance at 485 nm, and the concentration of pyruvic acid was converted using a standard curve. The standard curve was plotted with sodium pyruvate solution concentrations of 2, 4, 6, 8, and 10 mg/mL.

TABLE-US-00004 TABLE 4 Thiosulfinate Pyruvic acid Concentration method (ug/mL) (mol/L) Comparative Example 1 296.5 3.61 (Vacuum Concentration, 60 Brix°) Comparative Example 2 477.5 3.46 (Thin film-concentration, 40 Brix°) Comparative Example 3 582.4 3.78 (Plate-concentration, 60 Brix°) Example 1 (20 Brix°->60 Brix°) 638.0 3.05 Example 2 (30 Brix°->60 Brix°) 713.9 4.02 Example 3 (40 Brix°->60 Brix°) 658.2 3.89 Example 4 (50 Brix°->60 Brix°) 646.5 3.10

[0149] As a result, as shown in Table 4, it is shown that while thiosulfinate, which is a standard of a sulfur-containing compound, was included in an amount of 296.5 μg/mL in Comparative Example 1, thiosulfinate was included in an amount of 638 μg/mL to 713.9 μg/mL in the raw material concentrates prepared through the combined concentration method, indicating that the concentration efficiency was more than twice that of Comparative Example 1. In addition, while pyruvic acid, which is an indicator of a spicy taste, was contained in an amount of 3.61 mol/L in Comparative Example 1, in the combined concentration, pyruvic acid was included in an amount of 3.89 mol/L to 4.02 mol/L in the raw material concentrates prepared through the plate-concentration at a point where the solid content reached 30 Brix° to 40 Brix° by thin film-concentrating the raw-material juice, indicating an increase in the amount of pyruvic acid compared to Comparative Example 1. This is, considering the level of heat transferred per unit time and the concentration efficiency when the concentration is performed in large amounts, it is shown that compared to Comparative Examples 1 to 3, when the raw-material juice is concentrated through the combined concentration method of Examples, changes in quality of raw-material onions may be minimized.

Experimental Example 5. Observation of Flavor Enhancement Index Component in Raw Material Concentrate According to Concentration Process

[0150] Sulfur-containing compounds, which are said to be a main flavor component of onions, are known to be lost by heat. The flavor components in various raw-material onion concentrates prepared through the methods of Examples and Comparative Examples were analyzed through GC/MS and are shown in Tables 5 to 8 below. The analysis of volatile flavor substances was performed as follows.

[0151] Volatile Substance Analysis Method

[0152] The following method was used to identify flavor components of an extract. The adsorption for the analysis of volatile substances was pretreated using DVB/CAR/PDMS (50/30 μm) for SPME (Solid Phase Microextraction Fiber Holder, Supelco., Bellefonte, Pa., USA). 1 mL of the pre-treated extract was placed in a 20 mL EPA vial and capped with PTFE/Silicon. A SPME needle was inserted into the vial to which the extract was added, and the obtained was used for GC/MS analysis after adsorption at 60° C. for 30 minutes.

[0153] Agilent gas chromatograph (GC2010 plus, Agilent, USA) was used for GC/MS analysis, and DB-5MS (thickness: 0.25 μm, length: 30 m, diameter: 0.25 mm) was used for column. He was used as a carrier gas, and analysis was performed after conditions were set to a column oven temperature of 100° C., an injection temperature of 200° C., a total flow of 1.10 mL/min, and a total program time of 37 min.

[0154] In the GC/MS analysis, the detection limit was confirmed to be 1 ppm (weight ratio).

TABLE-US-00005 TABLE 5 Comparative Comparative Comparative Element Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Example 4 Sulfur-containing 114,341 419,695 216,719 207,986 213,129 207,165 199,741 compounds 1,2,4-Trithiolane, ND 57,561 6,471 8,374 4,017 ND 9,261 3,5-diethyl- Trisulfide, 1,784 28,168 11,047 9,149 12,411 11,492 10,056 dipropyl Disulfide, methyl 3,091 5,222 1,754 1,588 1,988 1,968 1,671 2-propenyl Thiirane, methyl- 9,649 35,318 13,763 13,225 17,505 16,939 13,565 Disulfide, dimethyl 13,279 16,409 8,397 8,956 9,879 8,868 6,940 Dimethyl trisulfide 60,809 175,167 115,116 108,689 106,796 107,172 102,084 Trisulfide, methyl 25,729 101,850 60,171 58,004 60,534 60,726 56,165 propyl 1,3-Dithiane 326 29,592 24,347 29,657 26,155 35,054 22,666 (Unit: peak area/10000)

[0155] As shown in Table 5 above, it is seen that the sulfur compound had a lower strength in the vacuum concentration method of Comparative Example 1, and the onion concentrate concentrated through the combined concentration of Example had some differences depending on the time of the combination, but had an increase or a decrease in some sulfur-containing compounds.

TABLE-US-00006 TABLE 6 Comparative Comparative Comparative Element Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Example 4 Heterocyclic 34,094 109,418    94,378 83,193   94,244   69,929   88,440   compounds Furan, 3-methyl- 33 ND ND ND ND ND ND Furan, 2-methyl- 52 ND ND ND ND ND ND Furan, 2-ethyl- 260 ND ND ND ND ND ND Furan, 2,5- 145 ND ND ND ND ND ND dimethyl- 2,4-Dimethylfuran 3,334 3,723    3,284 4,325   3,329   3,149   3,448   Furan, 2-pentyl- 783 730   413 218 376 267 208 Furan, 2-(1- 545 ND ND ND ND ND ND pentenyl)-, (E)- Furan, 2-methyl-5- 1,420 ND 12,429 ND 12,817   ND 8,639   (methylthio)- Furan, 2,5- 187 ND ND 388 147 ND 166 dihydro-2,5- dimethyl- Pyrazine, methyl- 382 ND ND ND ND ND ND Pyrazine, 2,6- 2,445 ND ND ND ND ND ND dimethyl- Pyrazine, 2- 362 ND ND ND ND ND ND ethenyl-6-methyl- Thiophene, 2,5- 534 999   406 448 525 470 485 dimethyl- Thiophene, 2,4- 468 4,796    2,153 1,777   2,550   2,177   2,211   dimethyl- Thiophene, 3,4- 19,123 58,589   42,114 48,709   47,872   40,538   45,749   dimethyl- Thiophene, 3,5- 1,907 ND ND ND ND ND ND dimethyl-2- (methylthio)- Thiophene, 2- 187 ND ND ND 223 ND ND methyl- Thiophene, 2- 987 ND 12,429 10,606   9,981   9,661   8,303   methoxy-5-methyl- Thiophene, 2,3- 891 ND ND ND ND ND ND dimethyl- Thiophene, 48 ND ND ND ND ND ND tetrahydro-3- methyl- Thiophene, 2- ND 40,581   20,798 15,540   15,635   13,140   18,902   nitro- Thiophene, 3- ND ND   353 346 535 110 331 methoxy- Thiophene, 3- ND ND ND 193 ND 105 ND methyl- Thiophene ND ND ND 643 253 312 ND (Unit: peak area/10000)

[0156] The heterocyclic compound shown in Table 6 is a compound produced by the Maillard reaction that occurs between an amino acid and a reducing sugar, and in Comparative Example 1, a variety of furan-based compounds and pyrazine-based compounds, which are typical heat-induced reaction materials, were detected. On the other hand, pyrazine-based compounds were not detected in the onion concentrates of Comparative Examples 2 to 3 and Examples, and only some of the furan compounds were detected in small amounts. The furan compounds with values having a peak area/10,000 value of about 1,000 or less were included in an amount of about 0.1 part by weight out of 100 parts by weight of a volatile component, indicating that a fairly small amount was included.

TABLE-US-00007 TABLE 7 Comparative Comparative Comparative Element Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Example 4 Miscellaneous 4,122 5,879 2,946 3,621 4,495 2,038 1,834 compounds 2-Pentenal, 2- 2,615 5,879 2,946 3,621 4,495 2,038 1,834 methyl- 1-Propanone, 1-(2- 371 ND ND ND ND ND ND furanyl)- Butanal, 3-methyl- 1,135 ND ND ND ND ND ND (Unit: peak area/10000)

[0157] In addition, as shown in Table 7 above, it is seen that 2-methyl-2-Pentenal, which is a main flavor component of raw onions, showed low strength in Comparative Example 1, resulting in reduced characteristics of the raw onions, while the flavor of the raw onions was specifically increased in the onion concentrates of Examples in which the combined concentration was performed at an appropriate time point. In addition, 1-(2-furanyl)-1-Propanone, which is known as heated odor of onions, and 3-methyl-butanal produced by oxidative decomposition of fat were produced only in Comparative Example 1, and were not produced in Comparative Examples 2-3 and Examples.

[0158] Therefore, in each concentration process for achieving unique flavor of a raw material, the thin film-concentration process of Comparative Example 2 does not generate the intensity of flavor and thermal reaction-inducing materials, but is expected to produce the thermal reaction materials at a higher concentration, and thus is not suitable for high concentration, and the plate-concentration process of Comparative Example 3 designed to optimize the conditions for combined concentration seems to have no significant difference from the combined concentration process due to less change in quality than commercialization conditions, but considering the concentration efficiency per unit time, it is determined that the combined concentration process of Examples is most advantageous for achieving the unique flavor of a raw material.

[0159] Meanwhile, the sulfur-containing compound was quantitatively analyzed to identify the content of each component of the sulfur-containing compound contained in the raw-material onion concentrate, and is shown in Table 8.

[0160] The sulfur-containing compound was quantified by adding 100 μL of 100 mg/L n-butylbenzene as an internal standard to 1.0 g of a sample and calculating the content of volatile flavor components in the sample with comparative relative quantification.

TABLE-US-00008 TABLE 8 Comparative Comparative Comparative Element Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Example 4 1,2,4-Trithiolane, ND ND ND ND ND ND ND 3,5-diethyl- Trisulfide, 1.00 19.88 11.16 8.59 12.32 12.47 7.97 dipropyl Disulfide, methyl 0.85 2.19 1.28 1.18 1.32 1.25 1.05 2-propenyl Thiirane, methyl- 0.52 5.12 13.46 10.02 11.75 9.09 10.7 Disulfide, dimethyl 1.51 7.65 6.31 5.64 7.41 7.60 5.39 Dimethyl trisulfide 9.32 108.84 109.73 110.26 120.36 115.71 105.59 Trisulfide, methyl 7.19 75.02 59.57 57.08 64.59 64.34 54.14 propyl Disulfide, methyl 0.00 0.47 0.59 0.42 0.82 0.67 0.43 1-propenyl Thiophene, 2,4- 0.09 1.72 2.49 2.02 2.48 1.92 2.33 dimethyl- Thiophene, 2,5- 3.13 0.66 0.75 0.70 0.69 0.62 0.72 dimethyl- 1,3-Dithiane 1.01 39.08 39.90 31.34 46.48 40.78 36.23 disulfide, dipropyl ND ND ND ND 2.150 ND 0.23 Thiophene, 3- ND ND ND ND ND ND ND methyl- Diallyl disulphide ND ND 1.34 0.87 1.50 1.58 1.01 Diallyl sulfide ND ND ND ND 0.09 3.99 0.23 Total 24.99  261.2 247.04 228.52 272.40 260.62 226.36 (Unit: ppm)

[0161] The content of each component of the sulfur-containing compound showed a similar tendency to the results of identifying flavor components. In the sulfur-containing compound, methyl trisulfide, dimethyl trisulfide, and 1,3-dithiane, which are major flavor components, were observed to have the highest content in the raw-material onion concentrates of Examples, and the onion concentrate prepared through the vacuum concentration process of Comparative Example 1 was observed to have a relatively low content.