KR102054271B1 - A method of increasing bioactive compounds isolated from onion skin using subcritical water with carbon dioxide - Google Patents

Abstract

By adding carbon dioxide to the subcritical water, an onion extract with increased physiologically active ingredients can be obtained, and quercetin is thermally decomposed at high temperature to prevent conversion into protocatechuic acid, which has low antioxidant activity. Increased onion extract can be obtained and can be utilized in various industries such as development of functional foods using onions, development of food materials, development of cosmetic materials.

Description

A method of increasing bioactive compounds isolated from onion skin using subcritical water with carbon dioxide}

The present invention relates to a method of increasing the physiologically active component separated from onion peel using subcritical water added with carbon dioxide.

Onion is a perennial plant belonging to the family Liliaceae, and due to the phenolic compound contained in a large amount, there are various physiological activities such as antioxidant, anticancer, antihypertensive, blood lipid improvement, anti-inflammatory. The major phenolic compounds in onions are quercetin and quercetin glycosides, with quercetin glycosides accounting for about 80% of the total phenolic compounds, and the content of quercetin in non-planted onion peels is 208.8 mg% It contains 92 times more than 2.26mg% of onion flesh, which is a edible part.

Phenolic compounds in onion husks were 44.2%, 20.9% free form, esterified form, and insoluble bound form combined with insoluble fiber, polysaccharide, lignin, etc., respectively. It is present at a rate of 34.9%, and this type of phenolic compound is mainly extracted with an organic solvent such as methanol or hydrolyzed using an acid or an alkali for the purpose of component analysis. However, this extraction and hydrolysis method has a problem that can not be used when the main purpose of the development of processed foods using onion peel due to the toxicity of the solvent used, there was a demand to solve this problem.

Republic of Korea Patent Publication No. 10-2015-005247

One object of the present invention is to provide a method for increasing the bioactive component separated from onions using subcritical water to which carbon dioxide is added.

Another object of the present invention is to provide an antioxidant food composition comprising a subcritical water extract of onion peel obtained by the above method or a bioactive component isolated from the onion peel extract.

Another object of the present invention to provide a health functional food comprising the antioxidant food composition.

Still another object of the present invention is to provide an antioxidant cosmetic composition comprising a subcritical water extract of onion peel obtained by the above method or a bioactive component isolated from the onion peel extract.

In order to achieve the above object, the present invention provides a step of injecting onion skin and water into a reaction tank of a subcritical water extraction device, removing nitrogen by passing nitrogen through the reaction tank, and carbon dioxide (CO ₂ ). Injecting the reactor at a pressure of 50 to 80 bar, heating the reactor, extraction for 3 to 13 minutes at a temperature of 105 to 125 ℃ and pressure of 80 to 300 bar to obtain a subcritical water extract of onion peel It provides a method of increasing the bioactive component separated from the onion by using a subcritical water added carbon dioxide, comprising the step of separating the bioactive component from the subcritical water extract of the onion peel.

The term "onion peel" of the present invention refers to the outer shell of onion which is a perennial plant belonging to the family Liliaceae. The onion peel may be dried, it may be dried using a drying method such as hot air drying, freeze drying, vacuum drying. The onion peel may be pulverized to increase the extraction area by increasing the contact area with the extraction solvent as the extraction process proceeds to the maximum, 4 to -20 until the extraction step for the purpose of maintaining the antioxidant active material to the maximum Can be stored at ℃.

The term “subcritical water” of the present invention is water in the liquid state at a temperature of 100 to 374 ° C. and a pressure of 4 to 400 bar. In general, the water has a boiling point of 100 ° C at 1 atmosphere. At high pressure, liquid water is called a subcritical water even when the temperature is raised. When the temperature is raised above 374 ° C, the water becomes supercritical. The dielectric constant (ε) according to the temperature of the subcritical water is in the range of 15 to 50, similar to organic solvents such as methanol (ε = 32) and ethanol (ε = 24), and thus have similar dissolution characteristics as organic solvents. Dielectric constant of water at room temperature and atmospheric pressure is ε = 79, so that materials that are not soluble in water at room temperature and atmospheric pressure can be dissolved and extracted in subcritical water.

The term "extraction" of the present invention is obtained by melting only a specific component in a substance consisting of various components, such as plants and minerals. In the present invention, a subcritical water in which carbon dioxide is added to an onion peel is used as a solvent to form a bioactive substance in the onion peel. It means to melt and extract.

As shown in FIG. 1, the subcritical water extraction device of the present invention includes a band heater, a cooling tank, a carbon dioxide tank, a nitrogen tank, a check valve, an inline filter, a high pressure pump, a pressure gauge, a reaction tank, a safety valve, a temperature gauge, and a temperature It includes a regulator and an on / off valve.

"Step of adding the onion skin and water to the reaction tank of the subcritical water extraction device" of the present invention is a step of adding the onion shell and water to the reaction tank (RV), the water can be used distilled water, onion peel in distilled water After dispersing, it may be added to the reactor (RV).

"Step of removing dissolved oxygen" of the present invention opens the valve (V2) connected to the nitrogen tank of the subcritical water extraction device and the valve (V4) connected to the reaction tank (RV) to inject nitrogen gas from the reaction tank (RV) It means the step of removing the dissolved oxygen. The nitrogen injection pressure may be 50 bar, and there is an advantage of preventing oxidation of the bioactive substance by dissolved oxygen when removing dissolved oxygen of the subcritical water.

In the step of injecting carbon dioxide of the present invention, at room temperature in a carbon dioxide tank, the liquid carbon dioxide is opened at a valve V1 connected to the carbon dioxide tank and a valve V4 connected to the reactor, and then injected into the reactor using a high pressure pump (HPP). It's a step. Injection pressure is 50 to 80 bar, the injection pressure can be measured through a pressure gauge connected to the valve (V4) connected to the reaction vessel.

"Step of heating the reactor" of the present invention refers to the step of heating the band heater formed on the outside of the reactor to increase the temperature of the reactor or to maintain a constant temperature. The temperature gauge is connected to the inside of the reactor and the band heater, respectively, and the temperature gauge provides temperature information of the reactor or the band heater to the temperature controller connected to the band heater, and the band heater is heated to the set temperature of the temperature controller connected to the band heater. To adjust the extraction temperature of the reactor.

In the step of obtaining a subcritical water extract of the present invention, the temperature inside the reactor was maintained at a temperature of 105 to 125 ° C., the pressure inside the reactor was measured by a pressure gauge connected to the inside of the reactor, and the extraction was performed at 80 to 80 ° C. A constant pressure of 300 bar was maintained. When the pressure inside the reactor was higher than the target pressure, the gas was discharged through the valve (V5), and the extraction time was measured for 0 minutes after reaching the target temperature, and extracted for 3 to 13 minutes. After cooling the reactor to obtain an extract. It may also further comprise the step of filtering the extract.

In an embodiment of the present invention, the contents of quercetin and protocatechuic acid of subcritical water extracts not injected with carbon dioxide and subcritical water extracts injected with carbon dioxide were measured at the same extraction temperature and extraction time conditions. In the injection of carbon dioxide, both the content of quercetin and protocatechuic acid were increased, but when extracted at 110 ° C. for 5 minutes, quercetin was increased 2.89 times, but protocatechuic acid was increased. The increase in the content of protocatechuic acid was found to be the smallest by 1.58 times. It was confirmed that injection of 65 bar of carbon dioxide inhibits the conversion of quercetin into protocatechuic acid.

Therefore, by the injection of carbon dioxide, it is possible to suppress the production of protocatechuic acid.

In one embodiment of the present invention, the content of the bioactive substance of onion peel extract according to the extraction temperature and extraction time of the subcritical water extract injected with carbon dioxide 65 bar. As a result of measuring the contents of the bioactive substances quercetin-3,4'-diglucoside, quercetin-4'-glucoside and quercetin, 110 Quercetin-3,4'-diglucoside, quercetin-4'-glucoside (quercetin-4'-) from the extract extracted at 5 ° C. for 10 minutes and the extract extracted at 120 ° C. for 5 minutes. glucoside) and quercetin were excellent. In addition, the contents of the total phenolic compounds and the total flavonoids were excellent in the contents of the total phenolic compounds and the total flavonoids were extracted for 5 minutes to 10 minutes at 110 ℃ and extracts extracted at 120 ℃ for 5 minutes.

Therefore, the extraction of the present invention may be performed for 5 to 10 minutes of extraction time at the extraction temperature 110 ℃, or 5 minutes at the extraction temperature 120 ℃ under pressure conditions of 80 to 300 bar.

In addition, the bioactive component of the present invention is composed of quercetin-3,4'-diglucoside, quercetin-4'-glucoside and quercetin It may be a total phenolic compound or a total flavonoid compound including one or more selected from the group.

In another aspect of the present invention, there is provided an antioxidant food composition comprising a subcritical water extract of onion peel obtained by the method or a bioactive component isolated from the subcritical water extract of onion peel.

In one embodiment of the present invention, the antioxidant effect was confirmed by confirming the DPPH free radical scavenging activity and FRAP activity of the extract according to the extraction temperature and extraction time of the subcritical water extract added with carbon dioxide. As a result of measuring DPPH free radical scavenging activity and FRAP activity, the extract extracted for 5 to 10 minutes at the extraction temperature of 110 ° C. and the extract extracted for 5 minutes at 120 ° C. showed excellent DPPH free radical scavenging activity and FRAP activity, and showed an excellent antioxidant effect. It was.

Therefore, the subcritical water extract of onion peel of the present invention or the bioactive component isolated from the subcritical water extract of onion peel may be used as a food composition for antioxidant.

The antioxidant food composition may further include ingredients commonly added during food manufacturing, for example, proteins, carbohydrates, fats, nutrients, seasonings and flavoring agents.

Examples of such carbohydrates are monosaccharides such as glucose, fructose and the like; Disaccharides such as maltose, sucrose, oligosaccharides and the like; And sugars such as conventional sugars such as polysaccharides such as dextrin, cyclodextrin and the like and xylitol, sorbitol, erythritol. As flavoring agents, natural flavoring agents (tauumatin, stevia extract (for example rebaudioside A, glycyrrhizin, etc.)) and synthetic flavoring agents (saccharin, aspartame, etc.) can be used.

For example, when the food composition of the present invention is prepared with a drink, citric acid, liquid fructose, sugar, glucose, acetic acid, malic acid, fruit juice, tofu extract, jujube extract, licorice extract and the like may be further included.

As another aspect of the present invention, it may be a health functional food comprising the food composition for antioxidant.

Health functional food of the present invention is a beverage containing the food composition (including alcoholic beverages), fruits and processed foods thereof (e.g. canned fruit, canned food, jam, marmalade, etc.), fish, meat and processed foods thereof (e.g. : Ham, sausage, corned beef, breads and noodles (e.g. udon noodles, soba noodles, ramen noodles, spaghetti, macaroni, etc.), fruit juices, various drinks, cookies, candy, dairy products (e.g. butter, cheese, etc.), food plants Oil, margarine, vegetable protein, retort food, frozen food, various seasonings (eg, miso, soy sauce, sauce, etc.).

In addition, the health functional food of the present invention may be formulated into tablets, pills, powders, granules, powders, capsules, liquid formulations and the like. These may be formulated further comprising one or more of carriers, diluents, excipients and additives.

Specific examples of the carrier, excipient, diluent and additives include, but are not limited to, lactose, dextrose, sucrose, sorbitol, mannitol, erythritol, starch, acacia rubber, calcium phosphate, alginate, gelatin, calcium phosphate, calcium Silicates, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, polyvinylpyrrolidone, methylcellulose, water, sugar syrup, methylcellulose, methyl hydroxy benzoate, propyl hydroxy benzoate, talc, magnesium stearate And at least one selected from the group consisting of mineral oils.

As another aspect, the present invention provides a cosmetic composition for antioxidant comprising a subcritical water extract of onion peel obtained by the above method or a bioactive component isolated from the subcritical water extract of onion peel.

The antioxidant cosmetic composition may further include conventional adjuvants and carriers such as stabilizers, solubilizers, vitamins, pigments and flavorings.

Cosmetic compositions of the invention may be prepared in any formulation conventionally prepared in the art, for example, solutions, suspensions, emulsions, pastes, gels, creams, lotions, powders, soaps, surfactant-containing cleansing , Oils, powder foundations, emulsion foundations, wax foundations and sprays, and the like, but are not limited thereto. More specifically, it may be prepared in the form of a nourishing cream, astringent lotion, a flexible lotion, a lotion, an essence, a nourishing gel or a massage cream.

When the formulation of the present invention is a paste, cream or gel, animal oils, vegetable oils, waxes, paraffins, starches, tragacanths, cellulose derivatives, polyethylene glycols, silicones, bentonites, silicas, talc or zinc oxide are used as carrier components. Can be.

Toss, talc, silica, aluminum hydroxide, calcium silicate or polyamide powder may be used as the carrier component when the formulation of the present invention is a powder or a spray, and in particular in the case of a spray, additionally chlorofluorohydrocarbon, propane Propellant such as butane or dimethyl ether.

When the formulation of the present invention is a solution or emulsion, a solvent, solubilizer or emulsifier is used as the carrier component, such as water, ethanol, isopropanol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1 Fatty acid esters of, 3-butylglycol oil, glycerol aliphatic ester, polyethylene glycol or sorbitan.

When the formulation of the present invention is a suspension, a liquid diluent such as water, ethanol or propylene glycol, suspending agents such as ethoxylated isostearyl alcohol, polyoxyethylene sorbitol ester and polyoxyethylene sorbitan ester, and microcrystals are used as carrier components. Sung cellulose, aluminum metahydroxy, bentonite, agar or tragacanth and the like can be used.

By adding carbon dioxide to the subcritical water, an onion extract with increased physiologically active ingredients can be obtained, and quercetin is thermally decomposed at high temperature to prevent conversion into protocatechuic acid, which has low antioxidant activity. Increased onion extract can be obtained and can be utilized in various industries such as development of functional foods using onions, development of food materials, development of cosmetic materials.

1 is a schematic diagram of a subcritical water extraction device (BH: band heater, CB: cooling tank, CO ₂ TK: CO ₂ tank, CV: check valve, F: inline filter, HPP: high pressure pump, N ₂ TK: nitrogen tank , P: pressure gauge, RV: reactor, SV: safety valve, T: temperature gauge, TC: thermostat, V: on / off valve.
2 is a result of measuring the content of the phenolic compound of the extract after extraction for 5 minutes at the extraction temperature 100 ~ 150 ℃ in the subcritical water extraction device (a: protocatechuic acid, b: quercetin-3,4 '-Diglucoside (quercetin-3,4'-diglucoside), c: quercetin-4'-glucoside, d: quercetin, e: total phenolic compound (total).
3 is the result of measuring the content of the phenolic compound of the extract extracted by the onion peel extraction temperature in the subcritical water extraction apparatus 110 to 130 ℃, the extraction time by 5 to 20 minutes (a: protocatechuic acid ( protocatechuic acid), b: quercetin-3,4'-diglucoside, c: quercetin-4'-glucoside, d: quercetin, e: total phenolic compound (total)).
4 shows the extraction temperature of the onion peel subcritical water extraction apparatus 110 to 130 ℃, the extraction time by varying the extraction time to 5 to 20 minutes (A) content of the total phenol, (B) the content of the total flavonoids, (C) DPPT free radical scavenging activity and (D) FRAP activity were measured.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples.

Comparative Example 1 Preparation of Phenol Compound Extract of Onion Peel Using Subcritical Water

Onions were purchased from commercial marts, washed, and then lyophilized by separating the pulp and the skin, and then frozen and stored. 2 g of lyophilized onion skin and 100 ml of distilled water were added to a 300 ml reactor (RV), the lid was closed, and nitrogen was passed through to remove dissolved oxygen in the sample solution, using a band heater (BH) at a temperature of 100 to 150 ° C. The mixture was heated to and extracted for 5 to 20 minutes, and then cooled to room temperature using tap water after extraction. After opening the lid of the reactor (RV), the valve (V6) under the reactor (RV) was opened to recover the extract, and then filtered to 100ml and used for component analysis.

Extraction temperature and extraction time of Comparative Example 1 were extracted as shown in Table 1.

Sample name Extraction temperature (℃) Extraction time (minutes) CO2 pressure (bar) Comparative Example 1-1 100 5 0 Comparative Example 1-2 110 5 0 Comparative Example 1-3 110 10 0 Comparative Example 1-4 110 15 0 Comparative Example 1-5 110 20 0 Comparative Example 1-6 120 5 0 Comparative Example 1-7 120 10 0 Comparative Example 1-8 120 15 0 Comparative Example 1-9 120 20 0 Comparative Example 1-10 130 5 0 Comparative Example 1-11 130 10 0 Comparative Example 1-12 130 15 0 Comparative Example 1-13 130 20 0 Comparative Example 1-14 140 5 0 Comparative Example 1-15 150 5 0

<Experimental method 1> Analysis of individual phenolic compounds of the extract

The content of individual phenolic compounds was analyzed using high performance liquid chromatography (HPLC). The extract was diluted two-fold and then filtered through a syringe filter. The peak was separated using an Inertsil ODS-3V column (5 μm, 4.6 × 250 mm), the column temperature was 30 ° C., the flow rate was 1.0 mL / min, and the sample injection amount was 10 μl. 0.5% formic acid aqueous solution and acetonitrile were used as solvent B for solvent A, and the solvent gradient for peak separation was 0 min, 15% B; 15 minutes, 30% B; 30 minutes, 35% B; 32 min, 70% B; 35 minutes, 15% B. The separated peaks were detected using a PDA detector, and the analysis wavelengths were 280 nm and 360 nm.

<Experiment 2> Analysis of total phenol and total flavonoid content

The total phenol content was measured by the following method. The extracts of Comparative Examples 1-1 to 1-15 were diluted 8-fold, 100 μl, distilled water 900 μl, and 100 μl of Folin-Ciocalteau's phenol reagent, followed by reaction at room temperature for 5 minutes. 300 μl of 20% Na ₂ CO ₃ and distilled water were added thereto, and the volume was adjusted to 2 ml. After the reaction at 25 ° C. for 1 hour, the absorbance was measured at 760 nm. The total flavonoid content was measured by the following method. 800 µl of ethanol and 60 µl of 5% NaNO _{2 were} added to 200 µl of the extract stock solution, followed by reaction at room temperature for 5 minutes. 60 µl of 10% AlCl ₃ was added to the solution, followed by reaction for 5 minutes at room temperature, and 400 µl of 1M NaOH solution was added for 1 minute at room temperature. Thereafter, 500 µl of distilled water was added to homogenize and the absorbance was measured at 415 nm.

Experimental Method 3 Measurement of Antioxidant Activity

DPPH free radical scavenging activity and ferric reducing antioxidant power (FRAP) were measured to determine the antioxidant activity. After reacting for 30 minutes by adding 2.0 ml of 0.2 mM DPPH solution to 0.1 ml of 4-fold extract, the absorbance was measured at 517 nm to measure DPPH free radical scavenging activity, and FRAP was measured by the following method. FRAP solution consists of 20 mM FeCl ₃ · 6H ₂ O solution, 300 mM acetate buffer, 10 mM 2,4,6-tripyridyl-s-triazine (TPTZ) solution (in 40 mM HCl) in a volume ratio of 1: 1: 10. Prepared by mixing at (v / v). 3 ml of the FRAP solution and 0.3 ml of distilled water were added to 0.1 ml of the diluted extract, followed by reaction at 37 ° C. for 30 minutes, and the absorbance was measured at 595 nm.

<Comparative Experiment 1> Measurement of the content of individual phenolic compounds in onion peel using subcritical water according to extraction temperature and extraction time

Protocatechuic acid, quercetin-3,4'-diglucoside, and quercetin-4'-glucoside, which are individual phenolic compounds of the extracts of onion skin extracted with subcritical water 4'-glucoside), quercetin and quercetin and total phenolic compounds (total) in order to determine the extraction temperature of the high, protocatechuic acid, quercetin-3,4 The content of quercetin-3,4'-diglucoside, quercetin-4'-glucoside and quercetin is measured, and the sum of their contents is used to determine the total phenolic compounds. Calculated as (total).

Figure 2 after extracting the onion peel in subcritical water extraction apparatus for 5 minutes at 100 to 150 ℃ extraction temperature as shown in Table 2, the protocatechuic acid (quetocetin acid), quercetin-3,4'- diglucoside (quercetin -3,4'-diglucoside), quercetin-4'-glucoside (quercetin-4'-glucoside), quercetin (quercetin) and the content of these phenolic compounds (total) is measured.

Sample name Extraction temperature (℃) Extraction time (minutes) Comparative Example 1-1 100 5 Comparative Example 1-2 110 5 Comparative Example 1-6 120 5 Comparative Example 1-10 130 5 Comparative Example 1-14 140 5 Comparative Example 1-15 150 5

The total phenolic content increased with increasing extraction temperature from 100 ℃ to 130 ℃, and it was 3.13 times higher than 100 ℃ with 15.00mg / g dry sample at extraction temperature of 130 ℃. The acid continuously increased with increasing extraction temperature and was the highest as 9.69 mg / g dry sample at 150 ℃. The content of quercetin-3,4'-diglucoside was highest at 0.41 mg / g dry sample at 120 ℃ and the content of quercetin-4'-glucoside at 2.35 and 2.24 mg / g dry sample at 120 ℃ and 130 ℃, respectively. High. The content of quercetin was highest at 5.56 mg / g dry sample at 130 ℃ and 3.19 times higher than 100 ℃. In particular, the content of protocatechuic acid continued to increase with increasing extraction temperature because part of the quercetin was converted to protocatechuic acid at high temperatures.

The antioxidant activity of protocatechuic acid is known to be 2.1 to 3.9 times lower than quercetin. Therefore, the higher the quercetin content and the lower the content of protocatechuic acid, the better the extraction condition.

The content of quercetin-3,4'-diglucoside was high at 110-130 ℃, the content of quercetin-4'-glucoside and quercetin was high at 120-130 ℃, and the content of protocatechuic acid was low at 100-120 ℃. .

In conclusion, it was confirmed that the high content of quercetin-3,4'-diglucoside, quercetin-4'-glucoside, quercetin, and low content of protocatechuic acid at 110-130 ° C resulted in a small conversion of quercetin to protocatechuic acid. It was confirmed that the subcritical water extraction of onion peel from to 130 ℃.

Next, to determine the optimal extraction conditions of individual phenolic compounds (protocatechuic acid, quercetin-3,4'-diglucoside, quercetin-4'-glucoside, quercetin) according to the extraction temperature and extraction time of subcritical water of onion peel, The content of protocatechuic acid, quercetin-3,4'-diglucoside, quercetin-4'-glucoside, and quercetin of the extract extracted by adjusting the extraction time at 5 to 20 minutes at the temperature of 110 to 130 ° C. identified as the extraction temperature were measured. The sum of these contents was calculated as the total phenolic compound (total).

Figure 3 is a result of measuring the content of the phenolic compound of the extract extracted for 5 to 20 minutes, the onion peel as the extraction temperature 110 to 130 ℃ in subcritical water extraction apparatus as shown in Table 3.

Sample name Extraction temperature (℃) Extraction time (minutes) Comparative Example 1-2 110 5 Comparative Example 1-3 110 10 Comparative Example 1-4 110 15 Comparative Example 1-4 110 20 Comparative Example 1-6 120 5 Comparative Example 1-7 120 10 Comparative Example 1-8 120 15 Comparative Example 1-9 120 20 Comparative Example 1-10 130 5 Comparative Example 1-11 130 10 Comparative Example 1-12 130 15 Comparative Example 1-13 130 20

At the extraction temperature of 110 ℃, the total phenolic compound content was 20.38 mg / g dry sample at 15 min extraction time, 2.46 times higher than the 5 min extraction time, and the content of protocatechuic acid increased continuously with the extraction time. The content of 3,4'-diglucoside, quercetin-4'-glucoside and quercetin was the highest at 15 min of extraction time, and the content of quercetin was 8.37 mg / g dry sample at 15 min of extraction time, 2.70 compared to 5 min of extraction time. It was twice as high.

The total content of phenolic compounds at the extraction temperature of 120 ℃ was 21.64 mg / g dry sample at the extraction time of 10 minutes. Protocatechuic acid showed the same content at the extraction time of more than 10 minutes, and quercetin-3,4'- Diglucoside, quercetin-4'-glucoside and quercetin content were highest at 10 min extraction time. The quercetin content was 8.73 mg / g dry sample at 10 min extraction time and 1.73 times higher than the 5 min extraction time.

At the extraction temperature of 130 ℃, all of the extracts except for potocatechuic acid decreased rapidly with increasing extraction time.

From the above results, it was confirmed that the total phenolic compound and the quercetin extraction yield of the whole phenolic compound of onion peel subcritical water extract was the highest when extracted at 120 ℃ for 10 minutes.

<Comparative Experiment 2> Determination of total phenolic content, total flavonoids content and antioxidant activity of onion peel using subcritical water according to extraction temperature and extraction time

Next, to measure the amount of physiologically active component of subcritical water onion peel extract according to extraction temperature and extraction time, total phenol content and total flavonoid content were measured, and DPPH free radical scavenging activity and FRAP Was measured.

4 is a total phenolics contents (total phenolics contents, TPC), the total flavonoids of the extract extracted by changing the onion peeling temperature in the subcritical water extraction apparatus 110 to 130 ℃, extraction time 5 to 20 minutes as shown in Table 3 The results were obtained by measuring the amount of (total flavonoid contents, TFC) and antioxidant activity. The change of total phenol content and total flavonoid content of subcritical water extract with extraction time at 110 ℃ and 120 ℃ showed similar tendency to change pattern of individual phenolic compounds.

At the extraction temperature of 110 ℃, the total phenol content increased with the extraction time, and the highest value was 56.5 and 56.7mg gallic acid equivalents (GAE) / g dry sample at 15 and 20 minutes. The total flavonoid content increased with increasing extraction time, and the highest value was 34.3 and 35.3mg quercetin equivalents (QE) / g dry sample at 15 and 20 minutes.

At the extraction temperature of 120 ℃, the total phenol content and total flavonoid content were the highest at 6 min of extraction time, 62.4mg GAE / g dry sample and 34.8mg QE / g dry sample, respectively.

At extraction temperature of 130 ℃, TPC and TFC were the highest with 37.8mg GAE / g dry sample and 23.0mg QE / g dry sample at 5 min extraction time, respectively.

Antioxidant activity with extraction time was similar to that of TPC and TFC. DPPH free radical scavenging activity and FRAP at 110 ° C extraction temperature increased with increasing extraction time and 41.1mg ascorbic acid equivalents (AAE) / g dry sample and 78.8mmol Fe ²⁺ at 15 minutes of extraction time, respectively. The highest DPPH free radical scavenging activity and FRAP at extraction temperature of 120 ℃ were 43.9mg AAE / g dry sample and 80.2mmol Fe ²⁺ / 100g dry sample, respectively. , DPPH free radical scavenging activity at extraction temperature of 130 ℃ increased with increasing extraction time, and FRAP showed a peculiar phenomenon that decreased with increasing extraction time. Is due.

From the above results, the subcritical water extract extracted at 120 ° C for 10 minutes has a high total phenolics contents (TPC) and total flavonoid contents (TFC), which is excellent in bioactive components It was confirmed that the activity is excellent.

Example 1 Preparation of Phenolic Compound Extract of Onion Peel Using Subcritical Water Added Carbon Dioxide

The subcritical water was expected to increase the extraction of phenolic compounds, especially nonpolar quercetin as much as possible, but in the comparative experiments, a significant amount of quercetin produced by extraction and hydrolysis was compared with quercetin due to high temperature subcritical water treatment. It was found to be converted to protocatechuic acid with relatively low antioxidant activity. Therefore, it is necessary to lower the optimal extraction temperature and extraction time to prevent the conversion of quercetin to protocatechuic acid. To this end, CO ₂ was added to the subcritical water to prepare an extract of onion peel.

When CO ₂ is added to water, carbonic acid is produced, and when the carbonic acid is dissociated, hydrogen ions are released to lower the pH of the solution, thereby promoting hydrolysis of the bound phenolic compound or quercetin glycoside.

Therefore, an example was prepared by extracting 5 to 10 minutes at 110 to 120 ° C. in order to check the temperature at a lower temperature and a shorter time than when extracted for 10 minutes at 120 ° C., which was confirmed as an excellent extraction condition in Comparative Examples.

Injecting liquid carbon dioxide at room temperature into a reaction tank (RV) using a high pressure pump (HPP) at 65 bar, the onion peel extract was prepared in the same manner as in Comparative Example 1 except that the extraction temperature and time were different, Example 1 Extraction temperature and extraction time of the extract was prepared as shown in Table 4.

Sample name Extraction temperature (℃) Extraction time (minutes) CO2 pressure (bar) Example 1-1 110 5 65 Example 1-2 110 10 65 Example 1-3 120 5 65 Example 1-4 120 10 65

Experimental Example 1 Measurement of the Contents of Individual Phenolic Compounds in Onion Peel Using Carbon Dioxide Subcritical Water According to Extraction Temperature

Individual phenolic compounds, protocatechuic acid, quercetin-3,4'-diglucoside, quercetin-4'-glucoside, quercetin, and all of these phenolic compounds, which were extracted from onion skin with subcritical water containing carbon dioxide according to extraction temperature and extraction time To check the extraction temperature and the extraction time with a high content of total), the protocatechuic acid, quercetin-3,4'-diglucoside, quercetin-4'- Glucoside, quercetin and the total content of these phenolic compounds (total) were measured.

Comparative Examples was added to distilled water, the CO ₂ to 65bar at room temperature without addition of CO ₂ in the onionskin extract and process the same conditions for at 110 ℃ and 120 ℃ 5 minutes and 10 minutes protocatechuic acid, quercetin-3,4'-diglucoside , quercetin-4'-glucoside, quercetin and the total content of these phenolic compounds (total) are shown in Table 5.

Sample name Temperature (℃) / time (min) / pressure (bar) Content of phenolic compounds (mg / g dry sample) Protocatechuic acid Quercetin-
3,4'-diglucoside Quercetin-
4'-glucoside Quercetin Total Comparative Example 1-2 110/5/0 3.30 ± 0.19 ^d 0.34 ± 0.03 ^e 1.52 ± 0.06 ^e 3.10 ± 0.18 ^d 8.26 ± 0.46 ^f Example 1-1 110/5/65 5.24 ± 0.25 ^c 0.62 ± 0.02 ^a 3.62 ± 0.09 ^ab 8.96 ± 0.31 ^a 18.43 ± 0.66 ^c Comparative Example 1-3 110/10/0 5.62 ± 0.29 ^c 0.44 ± 0.02 ^c 2.46 ± 0.13 ^d 5.97 ± 0.32 ^b 14.48 ± 0.76 ^d Example 1-2 110/10/65 6.88 ± 0.11 ^b 0.59 ± 0.02 ^a 3.50 ± 0.03 ^bc 9.23 ± 0.05 ^a 20.20 ± 0.19 ^b Comparative Example 1-6 120/5/0 5.30 ± 0.19 ^c 0.41 ± 0.03 ^cd 2.35 ± 0.10 ^d 5.12 ± 0.21 ^c 13.18 ± 0.50 ^e Example 1-3 120/5/65 6.68 ± 0.23 ^b 0.61 ± 0.02 ^a 3.72 ± 0.13 ^a 9.01 ± 0.25 ^a 20.01 ± 0.60 ^b Comparative Example 1-7 120/10/0 8.86 ± 0.48 ^a 0.52 ± 0.02 ^b 3.39 ± 0.11 ^c 8.87 ± 0.29 ^a 21.64 ± 0.86 ^a Example 1-4 120/10/65 6.73 ± 0.17 ^b 0.39 ± 0.03 ^d 2.41 ± 0.06 ^d 5.53 ± 0.23 ^c 15.07 ± 0.47 ^d

The total phenolic compound content was 2.23 times higher than 8.26 mg / g dry sample when no CO ₂ was added to 18.43 mg / g dry sample when CO ₂ was added and extracted at 110 ° C. for 5 minutes. At 110 ℃ in 10 minutes and 120 ℃ 5 bun in the amount of the total phenolic compounds were 1.39 times and 1.51 times respectively, than would not have the addition of CO _2, when the addition of CO _2. This is because the addition of CO ₂ lowers the pH of the subcritical water, which increases the hydrolysis of the bound phenolic compounds and extracts more phenolic compounds due to the lower pH.

When the content of the individual phenolic compound, when extracted for 5 minutes at extraction temperature 110 ℃ in subcritical water extraction by the addition of _{CO 2, protocatechuic acid, quercetin-} 3,4'-diglucoside, the content of quercetin and quercetin-4'-diglucoside Silver increased 1.58, 1.82, 2.38, and 2.89 times, respectively, when CO ₂ was not added. Among them, quercetin showed the highest increase of 2.89 times and protocatechuic acid showed the lowest increase of 1.58 times. As a result, it was confirmed that the conversion of quercetin to protocatechuic acid was prevented by the addition of CO ₂ to the subcritical water.

When was the amount at the time when extracted for 10 minutes at extraction temperature 110 ℃ in subcritical water extraction by the addition of CO ₂ to the individual phenolic compound than when no addition of CO ₂ 1.22 to 1.54 times higher, extracted for 5 minutes at 120 ℃, The content of the individual phenolic compounds was 1.26 to 1.75 times higher than when CO ₂ was not added. In particular, the content of quercetin was the highest at 9.23 mg / g in onion peel extract extracted at 110 ℃ for 10 minutes. In this case, the increase rate of quercetin was the highest and the rate of growth of protocatechuic acid was the lowest. Therefore, the addition of 65 bar of CO ₂ prevented the conversion of quercetin to protocatechuic acid in subcritical water extraction.

In addition, the rate of increase in the content of phenol compounds by CO ₂ addition is extracted for 5 minutes at 110 ℃ is I was higher than other extraction temperature and extraction time, which is the amount of the phenol compound to be hydrolyzed and extracted from the low-temperature smaller extraction with CO ₂ is added Yield improvement was relatively large.

In conclusion, the addition of CO ₂ to the subcritical water can reduce the optimal extraction temperature of quercetin and these glycosides from 120 ° C to 110 ° C, reduce the optimal extraction time from 10 minutes to 5 minutes, and break down quercetin and the protocatechuic acid. Conversion can be prevented and phenolic compounds, which are bioactive substances, can be increased in onion peel extracts.

Experimental Example 2 Contents of Total Phenolics, Total Flavonoids, and Antioxidant Activity of Onion Peel by Subcritical Water Added with Carbon Dioxide According to Extraction Temperature and Extraction Time

CO ₂ and the reaction mixture in distilled water to 65bar at room temperature at 110 ℃ and 120 ℃ 5 minutes and 10 minutes onion skin treated with the extract, and the content of total phenolic comparative example without addition of CO ₂ under the same conditions for the content of total flavonoids, antioxidants The activity (DPPH free radical scavenging activity, FRAP) is shown in Table 6.

Sample name Temperature (℃) / time (min) / pressure (bar) Total phenolic content
(mg GAE / g) Total flavonoid content
(mg QE / g) DPPH
(mg AAE / g) FRAP
(mmol Fe ²⁺ / 100 g) Comparative Example 1-2 110/5/0 21.1 ± 0.2 ^f 13.6 ± 1.1 ^g 17.8 ± 0.5 ^e 31.8 ± 1.3 ^g Example 1-1 110/5/65 67.0 ± 1.6 ^a 40.4 ± 1.0 ^a 44.2 ± 0.6 ^a 80.9 ± 1.2 ^b Comparative Example 1-3 110/10/0 33.8 ± 0.5 ^d 22.4 ± 1.4 ^e 26.2 ± 0.7 ^d 49.7 ± 1.1 ^e Example 1-2 110/10/65 66.5 ± 0.8 ^a 40.0 ± 0.8 ^a 44.5 ± 0.4 ^a 84.5 ± 1.3 ^a Comparative Example 1-6 120/5/0 30.1 ± 1.1 ^e 19.0 ± 0.8 ^f 25.7 ± 0.4 ^d 42.4 ± 1.7 ^f Example 1-3 120/5/65 65.9 ± 2.2 ^a 39.9 ± 1.2 ^a 44.4 ± 1.2 ^a 82.5 ± 1.5 ^ab Comparative Example 1-7 120/10/0 62.4 ± 3.8 ^b 34.8 ± 0.5 ^c 43.9 ± 1.1 ^a 80.2 ± 2.5 ^b Example 1-4 120/10/65 45.7 ± 1.5 ^c 28.3 ± 1.0 ^d 35.3 ± 0.3 ^c 62.6 ± 1.3 ^d

When 65 bar of CO ₂ was added, the total phenol content, total flavonoid content, DPPH free radical scavenging activity, and FRAP activity were 3.17 times when extracted at 110 ° C for 5 minutes than when CO ₂ was not added. 2.97 times, DPPH free radical scavenging activity increased 2.48 times, FRAP increased 2.54 times, TPC increased 1.96 times, TFC 1.78 times, DPPH free radical scavenging activity 1.69 times, FRAP increased 1.70 times when extracted at 110 ℃ for 10 minutes. When extracted at 120 ° C. for 5 minutes, TPC 2.18 times, TFC 2.10, DPPH free radical scavenging activity was 1.72, and FRAP was 1.94 times increased. The increase in TPC and TFC by CO ₂ addition was due to the carbonic acid produced by the added CO ₂ acting as an acid catalyst to promote the hydrolysis of the bound phenolic compound, and thus the antioxidant effect (DPPH free radical scavenging activity, FRAP) also increased.

The increase of TPC, TFC, DPPH free radical scavenging activity and FRAP activity by CO ₂ addition was the highest in the extract extracted at 110 ° C for 5 minutes. Compared with the extraction condition at 5 ° C. for 5 minutes, the amount of extraction and hydrolysis of the phenolic compound is small, and thus the effect of CO ₂ addition is relatively large. Therefore, when CO ₂ was added to the subcritical water, high TPC and TFC were obtained at the lower extraction temperature and extraction time, which resulted in a high antioxidant activity (DPPH free radical scavenging activity, FRAP).

As described above, when the extraction method using subcritical water containing CO ₂ of the present invention is carried out under specific conditions, the contents of phenolic compounds and flavonoids, which are bioactive substances of onion peel extract, are increased, and eco-friendly and non-toxic solvents are used. As a result, no additional process for solvent removal occurs and no environmental problems occur. In addition, the extraction temperature can be lowered, and the extraction time can be reduced, extract cost is reduced and economical. In addition, since the method of the present invention can efficiently obtain quercetin and its glycosides, which are excellent in various functional substances including antioxidant activity, using onion shells obtained from onions distributed throughout the country, using onions It is expected to be used in various industries such as functional food development, food material development, and cosmetic material development.

Claims (7)

Injecting the onion skin and water into the reactor of the subcritical water extraction apparatus;
Passing nitrogen through the reactor to remove dissolved oxygen;
Injecting carbon dioxide into the reactor at a pressure of 50 to 80 bar and heating the reactor;
Extracting subcritical water extract of onion peel by extracting 5 minutes to 10 minutes at 110 ° C. or 5 minutes at 120 ° C. under a pressure of 80 to 300 bar; And
Separating the bioactive component from the subcritical water extract of the onion peel, using the subcritical water added carbon dioxide method of increasing the bioactive component isolated from the onion. delete The method of claim 1,
Inhibiting the production of protocatechuic acid by injecting carbon dioxide. In claim 1,
The physiologically active ingredient is i) quercetin-3,4'-diglucoside, quercetin-4'-glucoside, and quercetin. Total phenolic compounds comprising at least one selected; Or ii) a total flavonoid compound. An antioxidant food composition comprising a subcritical water extract of onion peel obtained by the method of claim 1 or a bioactive component isolated from the subcritical water extract of onion skin. Health functional food comprising the antioxidant food composition of claim 5. Antioxidant cosmetic composition comprising a subcritical water extract of onion peel obtained by the method of claim 1 or a bioactive component isolated from the subcritical water extract of onion peel.

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