KR102862012B1 - Method for Softening Root Vegetables - Google Patents

Abstract

The present disclosure relates to a method for softening root vegetables. More specifically, the present disclosure describes a method that maximizes the softening effect of root vegetables in a short period of time, while minimizing color change and/or nutritional loss, through a two-step process combining a decompressive enzyme treatment followed by a carbonate and/or bicarbonate solution treatment.

Description

Method for Softening Root Vegetables

The present disclosure relates to a method for softening root vegetables. More specifically, the present disclosure relates to a method for maximizing the softening effect of root vegetables in a short period of time, while minimizing color change and/or nutritional loss, through a two-step process combining treatment with a decompressive enzyme followed by treatment with a carbonate and/or bicarbonate solution.

Due to the recent rapid aging of the population, the elderly population is rapidly increasing both domestically and internationally. According to the most recent Population and Housing Census, those aged 65 and older in Korea account for 16.4% of the total population, and the aging index has reportedly increased to 132.9%. Notably, Korea is projected to enter a super-aged society by 2025 (with the elderly population projected to account for 20.3%).

In general, aging is characterized by a decline in the physiological reserve and homeostatic control of each organ system of the body without disease, which leads to a decrease in appetite, weakening of teeth, or difficulty in consuming hard foods due to the use of dentures.

In this way, it is difficult for the elderly to maintain good health as not only their sense of taste and smell is dulled, but their chewing ability is weakened, which leads to a decrease in appetite and a decrease in food intake, which leads to a lack of nutritional intake.

As mentioned above, interest in senior-friendly foods is rapidly increasing due to changing demographic trends, and there is a high need for manufacturing customized foods that reflect the dietary habits of the elderly. The food manufacturing industry is also promoting senior-friendly foods and releasing related products, and is expanding its base to include products that soften meat, fish, and vegetables in addition to powder or porridge forms. In response, the Korea Industrial Standard (KS) for senior-friendly foods, operated and managed by the Ministry of Agriculture, Food and Rural Affairs, was established in 2017. The required hardness (N/㎡) for Level 1 (consumable by teeth), Level 2 (consumable by gums), and Level 3 (consumable by tongue) is 50,000 to 500,000, 20,000 to 50,000, and less than 20,000, respectively.

In general, leafy vegetables, such as potatoes, pumpkins, eggplants, and mushrooms, have a soft texture or can be cooked to a relatively soft texture, making them easier to consume. On the other hand, root vegetables, also known as root vegetables, tend to retain their hardness even when finely chopped and cooked due to their inherently hard nature. Examples of such root vegetables include radish (root), carrot, burdock, balloon flower, bonnet bellflower, beet root, lotus root, and ginseng.

Currently, various methods have been reported for softening root vegetables.

Freeze-impregnation is a method of rapidly injecting materials by combining two processes: slow freezing and decompression. It utilizes the phenomenon in which ice crystals are formed during the slow freezing process and tissue is cut by the formed ice crystals (e.g., Innov. food Sci. Emerg. Technol. 16: 267-276 (2012)). After the freeze-thaw process is completed, additional enzyme treatment is typically performed.

It is known that high-pressure processing technology can inhibit microorganisms and suppress the occurrence of bitter tastes or off-flavors caused by enzyme action through enzyme inactivation without changing the taste, flavor, or nutritional content of food (e.g., Food Sci. Ind. 48: 28-36 (2015)).

In addition, in the case of superheated steam processing, high-temperature steam transfers heat to food in a short period of time, which minimizes the loss of nutrients compared to long-term cooking, and it is reported to have a good microbial sterilization effect while maintaining the food's unique aroma, taste, texture, and color (e.g., J. Cereal Sci. 83: 96-100 (2018)).

In addition, a method of treating with enzymes under reduced pressure (or vacuum) is known, which mainly uses enzymes such as pectinase to break down and soften pectin in vegetables.

Among the aforementioned methods, physical processing can have undesirable effects on the appearance of vegetables, such as their color. Therefore, enzyme-based softening techniques, particularly for root vegetables, are attracting significant attention. However, relying solely on enzymes can lead to liquefaction, which can lead to nutritional loss.

In this regard, a method for softening vegetable ingredients using a softening composition comprising an enzyme, trisodium citrate, and sodium bicarbonate is known (e.g., Korean Patent Publication No. 2020-77690). This method uses a combination of an enzyme and a sodium salt to shorten fibers, and the sodium bicarbonate penetrates between the shortened fibers to expand them, thereby providing a softening effect. However, the enzyme does not fully penetrate the interior of the vegetable, which can result in uneven hardness between the interior and exterior of the vegetable. Therefore, a method that can overcome the limitations of the prior art is needed.

One specific example of the present disclosure is intended to overcome the limitations of the above-mentioned prior art and provide a method for effectively softening root vegetables in a short period of time while minimizing color change and/or loss of nutrients.

According to one specific example of the present disclosure,

a) a step of providing a suspension of softening enzyme;

b) a step of immersing root vegetables in the enzyme suspension provided in step a), and forming enzyme-containing root vegetables by permeating the softening enzyme into the root vegetables through at least one depressurization treatment, and simultaneously and/or subsequently performing an enzymatic reaction by the softening enzyme in the enzyme-containing root vegetables; and

c) a step of immersing the root vegetables that have undergone the enzymatic reaction in step b) in a solution of carbonate and/or bicarbonate and heat-treating them;

A method for softening root vegetables including .

According to an exemplary embodiment, the step a) may be performed by adding a softening enzyme to a buffer solution and suspending the solution.

According to an exemplary embodiment, the buffer solution may be at least one selected from the group consisting of a weakly acidic buffer solution, a phosphate buffer solution, and a citric acid buffer solution.

According to an exemplary embodiment, the concentration of the buffer solution may be in the range of 0.01 to 50 M, and the pH may be set in the range of 1 to 8.

According to an exemplary embodiment, the concentration of the enzyme in the buffer solution can be adjusted in the range of 0.1 to 2% (w/v).

According to an exemplary embodiment, the amount of root vegetables in the enzyme suspension in step b) can be determined in the range of 1 to 50% (w/v).

According to an exemplary embodiment, the root vegetable may be at least one selected from the group consisting of radish, carrot, burdock, bellflower root, deodeok, lotus root, ginseng, beet, taro, and radish.

According to an exemplary embodiment, the depressurization treatment can be performed under pressure conditions controlled at 50 kPa or less.

According to an exemplary embodiment, the decompression treatment in step b) is performed multiple times, wherein the interval between the decompression treatments is adjusted in the range of 1 to 5 minutes, and the decompression treatment time per time can be adjusted in the range of 0.5 to 2 minutes.

According to an exemplary embodiment, the enzymatic reaction can be performed at 30 to 60°C for 30 to 90 minutes.

According to an exemplary embodiment, the carbonate may be sodium carbonate, and the bicarbonate may be at least one selected from the group consisting of potassium bicarbonate and sodium bicarbonate.

According to an exemplary embodiment, the solution concentration of the carbonate and/or bicarbonate can be adjusted in the range of 0.5 to 5% (w/v).

According to an exemplary embodiment, the heat treatment in step c) may be performed at 65 to 110°C for 1 to 30 minutes.

According to a specific example of the present disclosure, in order to soften vegetables with a uniquely hard texture, such as root vegetables, to a state that is easy to consume not only by the elderly but also by patients and infants, a two-step process combining a pressure-reducing enzyme impregnation treatment and a carbonate and/or bicarbonate solution treatment in that order is applied, root vegetables can be effectively softened in a short period of time, and difficulties in maintaining appearance, induction of a softening phenomenon, color change and/or loss of nutrients that may occur during the process can be suppressed as much as possible. In addition, compared to existing softening methods, especially a pressure-reducing enzyme treatment method after freeze-thawing, it is advantageous in that the softening effect of root vegetables can be maximized while minimizing destruction of cell walls and cell membranes.

FIG. 1 is a drawing schematically illustrating the sequence of a method for softening root vegetables according to an exemplary embodiment of the present disclosure;
Figure 2a is a graph comparing the hardness of raw carrots before treatment with the hardness of raw carrots after decompression enzyme treatment alone, decompression enzyme treatment after heating, decompression enzyme treatment after freeze-thaw, and decompression enzyme treatment followed by sodium bicarbonate treatment;
Figure 2b is a graph comparing the hardness of raw carrots treated with sodium bicarbonate alone, treated with decompression enzyme alone, treated with sodium bicarbonate followed by decompression enzyme, and treated with decompression enzyme followed by sodium bicarbonate;
Figure 3 is a scanning electron microscope (SEM) photograph showing the microstructural changes in carrots with and without decompression enzyme treatment, and after subsequent heat treatment, freeze-thaw treatment, or sodium bicarbonate treatment; and
Figure 4 is a graph showing the change in maximum hardness of carrots according to the concentration of sodium bicarbonate (0.5 to 2.5%) and the depressurization treatment interval (1 to 5 minutes).

The present invention can be fully achieved by the following description. It should be understood that the following description describes preferred embodiments of the present invention and is not necessarily limited thereto. Furthermore, the attached drawings are provided to aid understanding and are not intended to limit the present invention. Details regarding individual components can be appropriately understood based on the specific intent of the related descriptions described below.

The terms used in this specification may be defined as follows.

"Vegetable" means any living organism within the plant kingdom, which may be eaten raw, cooked, or preserved in any form, or any part thereof, and may include leaves, seeds, roots, tubers, bulbs, flowers, fruits, stems, shoots, nuts, etc.

"Root vegetables" may refer to vegetables whose parts that are consumed or eaten grow underground.

"Enzyme" may be generally understood to mean a compound, specifically a protein, that functions as a catalyst for a chemical reaction during a biochemical process (e.g., hydrolyzing complex carbohydrates such as xylan chains of cellulose, hemicellulose, pectin, hemicellulose, etc. and/or pentose polymers into pentoses, hexaseeds, etc.).

"Softening" may refer to a process that reduces the mechanical properties of raw vegetables, such as shear stiffness or hardness.

Terms such as "on" or "upper side" and "lower side" or "below" can be understood to describe the relative positional relationship between components or members, and the terms "located above" or "located below" can be understood to express the relative positional relationship not only in a state of contact with a specific object but also in a state of not being in contact with it.

When a numerical range is specified herein with lower and/or upper limits, it is understood that any sub-combination within that numerical range is also disclosed. For example, when "1 to 5" is described, it can include 1, 2, 3, 4, and 5, as well as any sub-combination therebetween.

Where any component or member in this specification is described as being "connected" to another component or member, unless otherwise stated, it is to be understood that this includes not only the case where it is directly connected to said other component or member, but also the case where it is connected through the intervention of said other component or member.

Similarly, the term "contact" may be understood to include not only direct contact but also contact under the intervention of other components or absences.

When we say that something "includes" something, we mean that it may also include other components, unless otherwise stated.

According to one specific example of the present disclosure, root vegetables can be processed into a softened state suitable for consumption by the elderly and others through a specific sequence of two-step processes of treatment with a decompressive enzyme followed by treatment with a carbonate and/or bicarbonate solution, while at the same time minimizing the loss of the vegetable's inherent color and/or nutritional components.

The sequence of the method for softening root vegetables according to an exemplary embodiment of the present disclosure is schematically illustrated in FIG. 1.

Manufacturing (providing) of softening enzyme suspension

Referring to the above drawing, a step of preparing a softening enzyme suspension is first performed.

In this regard, the softening enzyme may be selected from a type that performs the function of decomposing the cell wall of plants. According to exemplary specific examples, as the softening enzyme, exo-1,4-α-d-glucosidase, cellulase, glucoamylase, α-amylase, xylanase, β-glucanase, pectin lyase, polygalacturonase, endo-1-4-β-xylanase, pullulanase, heat-stable α-amylase, hemicellulase, arabanase, etc. can be exemplified, and at least one of these can be selected and used. These enzymes are commercially available, for example, AMG ^® 300L (Exo-1,4-α-d-glucosidase), Celluclast ^® 1.5L (Cellulase), Dextrozyme ^® DX 1.5X (Glucoamylase), Diazyme ^® FA (α-Amylase), Fungamyl ^® Super AX (α-Amylase, xylanse), Laminex ^® BG2 (β-Glucanase), Liquozyme ^® Supra (α-Amylase), Maltogenase ^® L (α-Amylase), Novozym ^® 33095 (Pectin lyase, polygalacturonase), Pectinex ^® Ultra AFP (Pectin lyase, polygalacturonase), Pentopan ^® 500 BG (Endo-1-4-β-xylanase), Promozyme ^® D2 (Pullulanase), Termamyl ^® 120L (Heat-stable α-amylase), Viscoflow ^® MG (β-Glucanase, xylanase, cellulase, hemicellulase, α-amylase), Viscozyme ^® L (Arabanase, cellulase, β-glucanase, hemicellulose, xylanase), etc. Specifically, Viscozyme ^® L can be used, and since it has an enzyme that breaks down complex plant cell walls, it has the advantage of being applicable to the softening treatment of various root vegetables.

In an exemplary embodiment, a softening enzyme suspension can be prepared by adding a softening enzyme to a buffer solution and suspending the solution. The buffer solution can maintain pH during the enzymatic reaction and also provide a function of inducing pectin decomposition in root vegetables. As an example, the buffer solution can exhibit weak acidity, and can typically be an acetic acid buffer solution, a phosphate buffer solution, a citric acid buffer solution, etc., and at least one of these can be used.

According to an exemplary embodiment, the concentration of the buffer solution may be determined in a range of, for example, about 0.01 to 50 M, specifically about 0.03 to 1 M, and more specifically about 0.05 to 0.5 M, taking into account the influence of acidic and basic substances on the sensory characteristics. However, the concentration of the buffer solution may be changed depending on the types of acids and salts contained therein.

In addition, the pH of the buffer solution can be determined in a range of about 1 to 8 in general, about 3 to 6 in particular, about 4 to 5.5 in particular, about 5 to 5.5 in particular, and the pH range can change depending on the type of buffer solution.

For example, the pH of the phosphate buffer solution may typically be in the range of about 6 to 8 or about 1 to 3.5, and the pH of the acetate buffer solution may typically be set in the range of about 3.5 to 6.

According to an exemplary specific example, the concentration (or amount added) of the enzyme in the softening enzyme suspension can be determined in consideration of the type of enzyme and the type of root vegetable, and can be, for example, in the range of about 0.1 to 2% (w/v), specifically about 0.5 to 1.5% (w/v), and more specifically about 0.8 to 1.3% (w/v). In this regard, if the enzyme is added in an excessive amount, it may be difficult to maintain the appearance due to excessive enzyme action on the root vegetable, whereas if the enzyme concentration is excessively low, it may be difficult to sufficiently secure the softening effect. However, the concentration of the enzyme can be changed depending on the type of enzyme and root vegetable.

Decompression enzyme treatment

Once the suspension of softening enzyme is prepared or provided, root vegetables are added thereto and immersed (or impregnated).

In an exemplary embodiment, the root vegetables are not particularly limited as long as they are root vegetables known in the art, and may include, for example, radish, carrot, burdock, bellflower root, deodeok, lotus root, ginseng, beet, taro, radish, etc., and one or more types of these may be added to the enzyme suspension. In addition, the amount of the root vegetables added to the softening enzyme suspension may be determined in a range of, for example, about 1 to 50% (w/v), specifically about 5 to 25% (w/v), and more specifically about 10 to 15% (w/v). However, the amount added may vary depending on the type and properties of the root vegetables.

As described above, after the introduction and immersion of the root vegetables, a reduced pressure or vacuum is applied (reduced pressure treatment). In this regard, the reduced pressure treatment may be performed at least once, specifically at least twice (multiple times). At this time, the applied pressure may be determined in consideration of a level capable of sufficiently removing the gas inside the root vegetables, and may be adjusted within the range of, for example, about 50 kPa or less, specifically about 30 kPa or less, and more specifically about 10 to 20 kPa. Since a phenomenon of the tissue of the root vegetables collapsing may be induced when the applied pressure exceeds a certain level, it may be desirable to appropriately adjust it within the aforementioned range. In addition, it may be advantageous to perform the reduced pressure treatment until the suspension concentrations inside and outside the immersed root vegetables reach an equilibrium state.

According to a specific embodiment, the depressurization treatment may be performed multiple times (i.e., for example, about 2 to 10 times, specifically about 3 to 6 times, more specifically 4 to 5 times), and when the depressurization treatment is performed multiple times in this manner, the suspension can be efficiently infiltrated even by a short depressurization (vacuum) treatment.

In addition, the interval between multiple depressurization treatments may be determined in consideration of the time for the suspension to sufficiently penetrate, and may be, for example, in the range of about 1 to 5 minutes, specifically about 2 to 4 minutes, and more specifically about 2.5 to 3.5 minutes. In addition, the depressurization treatment time per treatment may be, for example, in the range of about 0.5 to 2 minutes, specifically about 0.8 to 1.8 minutes, and more specifically about 1 to 1.5 minutes. However, the above-described treatment conditions may be changed depending on the type of root vegetable, etc.

According to this specific example, a softening enzyme is infiltrated into the root vegetables through the above-described decompression treatment. In this way, an enzymatic reaction can be performed on the root vegetables containing the softening enzyme. At this time, the enzymatic reaction can be performed during the decompression infiltration process, or can be performed after the decompression infiltration process is completed. In some cases, a part of the enzymatic reaction can be performed during the decompression infiltration process, and an additional enzymatic reaction can occur after the decompression treatment. According to an exemplary specific example, a change in the cell wall structure can occur inside the root vegetables through the enzymatic reaction. As an example, the temperature of the enzymatic reaction can be determined in consideration of the activation temperature of the enzyme used, the type of enzyme, etc., and can be, for example, in the range of about 30 to 60°C, specifically about 35 to 55°C, and more specifically about 40 to 50°C, but this can be understood as an exemplary temperature. Additionally, the enzyme reaction time can be adjusted within a range of, for example, about 30 to 90 minutes, specifically about 45 to 75 minutes, and more specifically about 55 to 65 minutes. However, the reaction temperature and time can be changed depending on the type of enzyme and root vegetable.

Meanwhile, if the enzymatic reaction exceeds a certain level, the problem of the outer appearance becoming deteriorated may arise, so subsequent enzyme inactivation treatment may be performed (optional step). For example, the enzymatic reaction may be stopped by heating at about 90 to 105°C (specifically, about 95 to 100°C) for about 5 to 15 minutes (specifically, about 5 to 7 minutes).

In this way, root vegetables that have undergone pressure-reducing enzyme treatment are initially in a softened state, and the hardness of root vegetables after pressure-reducing enzyme treatment is, for example, 250,000 N/㎡ or more, specifically, about 270,000 to 360,000 N/㎡, more specifically, about 290,000 to 330,000 N/㎡, which still does not reach the level of 50,000 N/㎡ or less, which is the second stage of the Korean Industrial Standard for Senior-Friendly Foods. In addition, the nutritional component retention rate of root vegetables after pressure-reducing enzyme treatment may be, for example, about 70% or more, specifically about 75% or more, more specifically about 79% or more. In this way, pressure-reducing enzyme treatment alone still does not exhibit properties that satisfy the second stage of the Korean Industrial Standard.

Carbonate and/or bicarbonate treatment

Referring back to Figure 1, after the decompression enzyme treatment, a step is performed in which the root vegetables are immersed in a solution of carbonate and/or bicarbonate.

In this regard, performing carbonate and/or bicarbonate treatment after the decompression enzyme treatment has a significant impact on softening of root vegetables as well as suppressing color change and/or loss of nutrients. For example, if the decompression enzyme treatment is performed in a different order than the carbonate and/or bicarbonate treatment, the sodium bicarbonate solution may not sufficiently penetrate into the root vegetables, making it difficult to achieve the desired level of hardness reduction effect, and the color change and/or nutrient retention rate is also lower than in the present specific example. Although the present disclosure is not bound by a particular theory, it is believed that when softening is performed in the order of the decompression enzyme treatment and the carbonate and/or bicarbonate treatment, a sufficient softening effect can be achieved through a mechanism in which the carbonate and/or bicarbonate sufficiently penetrate into the root vegetables and expand during the heat treatment process, and further, the metal components that form salts, particularly the sodium components, can minimize the leaching of nutrients and color components.

Meanwhile, sodium carbonate can be used as a representative carbonate in carbonate and/or bicarbonate treatments. Furthermore, representative examples of bicarbonates include potassium bicarbonate and/or sodium bicarbonate. In a specific embodiment, the compound used is sodium bicarbonate, which can be particularly advantageous in increasing nutrient retention and minimizing color change.

According to an exemplary embodiment, the concentration of the carbonate and/or bicarbonate solution can be adjusted in consideration of the swelling characteristics, and may be, for example, in the range of about 0.5 to 5% (w/v), specifically about 0.7 to 4% (w/v), and more specifically about 1 to 3% (w/v). In a specific embodiment, the concentration of the solution may be about 1.2 to 2% (w/v), particularly about 1.5% (w/v). In this regard, if the concentration of the carbonate and/or bicarbonate solution is too high, the root vegetables may tend to soften or break, whereas if it is too low, the softening effect by the carbonate and/or bicarbonate may be minimal. Therefore, it may be advantageous to adjust within the above-mentioned range. However, the present embodiment is not limited thereto, and may be changed depending on the type of root vegetables, etc.

Additionally, according to exemplary embodiments, the pH of the carbonate and/or bicarbonate solution may be in the range of, for example, about 7 to 12, specifically about 7.5 to 9, more specifically about 8 to 8.5, which may be understood to be exemplary in nature.

According to an exemplary embodiment, the decompressed enzyme-treated root vegetables may be placed in a carbonate and/or bicarbonate solution and immersed for a predetermined period of time, for example, about 30 to 90 minutes, specifically about 45 to 60 minutes, so that the carbonate and/or bicarbonate may sufficiently penetrate the inside of the root vegetables. Thereafter, the expanded action of the penetrated carbonate and/or bicarbonate may be induced through heat treatment. In this regard, the heating temperature may be controlled in a range of, for example, about 65 to 110°C, specifically about 75 to 105°C, and more specifically about 95 to 100°C. In addition, the heat treatment time may be controlled in a range of, for example, about 1 to 30 minutes, specifically about 5 to 15 minutes, and more specifically about 5 to 10 minutes. However, the above-described heat treatment conditions may be understood to be exemplary.

Meanwhile, according to a specific example, the decompression enzyme treatment and the carbonate and/or bicarbonate treatment are all factors that affect the hardness of root vegetables, and since each treatment condition affects the other, the individual steps can be optimized by taking this into consideration.

To this end, optimized conditions can be predicted using statistical analysis, specifically response surface design (RSM). Specifically, regression analysis can be performed by selecting independent variables X _i and X _j as the decompression treatment interval (minutes) and the concentration (%) of carbonate and/or bicarbonate, respectively, and selecting the dependent variable Y as hardness (10 ⁴ N/㎡), according to the second-order regression equation represented by the following mathematical equation 1.

[Mathematical Formula 1]

In the above equation, Y is the dependent variable, hardness (10 ⁴ N/㎡); X _i and X _j are the independent variables, decompression treatment interval (minutes) and concentration of carbonate and/or bicarbonate (%), respectively; b ₀ is the intercept coefficient; b _i is the linear coefficient; b _ii is the square coefficient; and b _ij is the interaction coefficient.

Regression analysis can be performed using commercially available statistical software, for example, the SAS program (as specifically exemplified in the examples described below).

Through the above-described regression analysis, it is possible to derive or predict conditions under which the softening effect (i.e., hardness reduction) of root vegetables is optimized by controlling the interval between multiple decompression enzyme treatments and the concentration of carbonate and/or bicarbonate solutions, respectively.

According to an exemplary embodiment, the hardness of root vegetables that have undergone carbonate and/or bicarbonate treatment after the decompression enzyme treatment may be, for example, about 80,000 N/㎡ or less, specifically about 50,000 N/㎡ or less, and more specifically in the range of about 43,000 to 47,000 N/㎡. However, the hardness may vary depending on the type of root vegetables. At this time, the hardness reduction rate compared to the hardness of the root vegetables before treatment may be, for example, at least about 90%, specifically at least about 93%, and more specifically in the range of about 95 to 99%, but this may be understood as an exemplary intent.

In addition, as described above, in the exemplary embodiment, color change and/or loss of nutrients can be minimized by controlling the decompression treatment interval (minutes) and the bicarbonate concentration (%) during the softening process of the root vegetables. As an example, the color difference (ΔE) between the root vegetables before treatment and the root vegetables after the two-step treatment can be, for example, in a range of about 9 or less, specifically about 8 or less, more specifically about 7 or less, and particularly specifically about 6 or less. In addition, the retention rate (or maintenance rate) of nutrients in the root vegetables after the two-step treatment compared to the root vegetables before treatment can be, for example, in a range of at least about 70%, specifically at least about 72%, and more specifically at least about 75%.

The present invention can be more clearly understood by the following examples, which are provided merely for the purpose of illustrating the present invention and are not intended to limit the scope of the invention.

Example

The materials used in this example are as follows.

- Viscozyme L (a mixture of beta-glucanases, pectinases, hemicellulases, and xylanases) commercially available from Novoxymes was used as a softening enzyme.

- Acetic acid buffer solution (0.05 M, pH 5) was purchased from Sigma-Aldrich and used.

- Sodium bicarbonate was purchased from Sigma-Aldrich and used.

Experimental procedure

A. Hardness measurement and analysis

The hardness of carrots uniformly formulated into 1 x 2.5 x 2.5 cm thick pieces was measured using a Texture Analyzer (TA-XT2; Stable Micro Co., Surrey, UK) according to the puncture test procedure. The experimental conditions were set to 25 kg load cell, pre-test speed 2.0 mm/s, test speed 1.0 mm/s, and post-test speed 2.0 mm/s, respectively, and a cylindrical probe with a diameter of 3 mm was used at 70% strain. Each sample was repeated six times, and the average value was calculated.

B. Internal microstructure analysis

All samples subjected to different processing conditions were freeze-dried, spread thinly on carbon-coated carbon tape, and then coated with platinum. The samples were observed using environmental scanning electron microscopy (FE-SEM, Verios G4UC, Thermo Fisher Scientific CO., Waltham, USA) at an accelerating voltage of 15.0 kV.

D. Color analysis

The L ^* (brightness), a ^* (redness), and b ^* (yellowness) values of each sample were based on a standard white plate (L ^* = 96.86, a ^* = -0.02, b ^* = 1.99), and the total color difference (ΔE) was calculated using the following mathematical equation 2.

[Equation 2]

In the above formula, L ₁ , a ₁ and b ₁ are the values of the control group (raw carrot), and L ₂ , a ₂ and b ₂ are the values of the treated sample.

A. Beta-carotene extraction and content analysis

- For beta-carotene extraction, 21 mL of ethanol-hexane (4:3) solution was added to 0.25 g of the sample, and the mixture was ground at 1,200 rpm for 5 minutes using a homogenizer. The solvent containing the sample was extracted in a shaking water bath (LSB-045S; Lab tech biomedic Co., Gyeonggi-do, Korea) for 30 minutes, and then the extraction solvent was separated from the sample. The extraction was repeated under the same conditions until the sample was completely extracted. The extracted solvents were mixed, and 5 mL of distilled water was added to the mixed solvent, which was then allowed to stand for 5 minutes to perform phase separation. The volume of the separated hexane phase was recorded so that the beta-carotene content could be calculated subsequently. After obtaining the hexane phase, it was dissolved in the mobile phase and used for HPLC analysis.

- The beta-carotene content in the samples was measured using an HPLC system (Waters Co., Milford, MA, USA) equipped with a WatersTM 486 tunable absorbance detector and a Waters 515 pump. Capcell pak C18 (250 x 4.6 mm, 5 μm, Shiseido, Tokyo, Japan) was used as the analytical column. The mobile phase was acetonitrile-methanol (10:90, v/v) at a flow rate of 1 mL/min. 20 μL of the extract containing beta-carotene was injected, and measurements were repeated three times per sample under UV 450 nm, and the average value was calculated.

Example 1

Sodium bicarbonate treatment after pressure-reducing enzyme treatment

An enzyme suspension (concentration: 1% (w/v)) was prepared by adding 1% (v/v) Viscozyme L to 0.05 M acetic acid buffer solution (pH 5.0). Carrot samples (raw carrots) were added to the prepared enzyme suspension at a ratio of 1:10 (w/v) and transferred to a vacuum chamber (J-DV01; Jisco Co., Seoul, Korea) at 25°C. Subsequently, depressurization treatment (applied pressure: 10 kPa) was performed for 1 minute at 3-minute intervals for a total of 12 minutes.

After depressurization, the sample was taken out of the enzyme suspension and subjected to an enzymatic reaction at 50°C for 1 hour. After the enzymatic reaction was completed, the sample was immersed in a 1.5% (w/v) sodium bicarbonate solution for 1 hour and then heated for 5 minutes.

Comparative Example 1

Decompression enzyme treatment

A suspension (concentration: 1% (w/v)) was prepared by adding 1% (v/v) Viscozyme L to 0.05 M acetic acid buffer solution (pH 5.0). Carrot samples (raw carrots) were added to the prepared enzyme suspension at a ratio of 1:10 (w/v) and transferred to a 25°C vacuum chamber (J-DV01; Jisco Co., Seoul, Korea). Subsequently, depressurization treatment (applied pressure: 10 kPa) was performed for 1 minute at 3-minute intervals for a total of 12 minutes. After depressurization, the sample was taken out of the enzyme suspension, reacted at 50°C for 1 hour, and then heated for 5 minutes.

Comparative Example 2

Decompression enzyme treatment after heat treatment

Carrot samples (raw carrots) were boiled in water for 5 minutes, cooled in cold water, and left at room temperature for 10 minutes. Then, 1% (v/v) Viscozyme L was added to 0.05 M acetic acid buffer solution (pH 5.0) to prepare a suspension (concentration: 1% (w/v)). The carrot sample was added to the prepared enzyme suspension at a ratio of 1:10 (w/v) and transferred to a 25°C vacuum chamber (J-DV01; Jisco Co., Seoul, Korea). Thereafter, the sample was subjected to depressurization for 1 minute at 3-minute intervals for a total of 12 minutes (applied pressure: 10 kPa). After depressurization, the sample was taken out of the enzyme suspension, reacted at 50°C for 1 hour, and then heated for 5 minutes.

Comparative Example 3

Freeze-thaw and then decompressed enzyme treatment

Carrot samples (raw carrots) were heat-treated for 5 minutes, then frozen at ??20℃ for 24 hours, and then thawed at room temperature for 3 hours.

Next, 1% (v/v) Viscozyme L was added to 0.05 M acetic acid buffer solution (pH 5.0) to prepare a suspension (concentration: 1% (w/v)). Carrot samples were added to the prepared enzyme suspension at a ratio of 1:10 (w/v) and transferred to a 25°C vacuum chamber (J-DV01; Jisco Co., Seoul, Korea). Thereafter, depressurization treatment (applied pressure: 10 kPa) was performed for 1 minute at 3-minute intervals for a total of 12 minutes. After depressurization, the sample was taken out of the enzyme suspension, reacted at 50°C for 1 hour, and then heated for 5 minutes.

Comparative Example 4

Sodium bicarbonate treatment

Carrot samples (raw carrots) were soaked in a 1.5% (w/v) sodium bicarbonate solution for 1 hour and then heated for 5 minutes.

Comparative Example 5

Sodium bicarbonate treatment followed by pressure-reducing enzyme treatment

Carrot samples (raw carrots) were soaked in a 1.5% (w/v) sodium bicarbonate solution for 1 hour and then heated for 5 minutes.

Next, 1% (v/v) Viscozyme L was added to 0.05 M acetic acid buffer solution (pH 5.0) to prepare a suspension (concentration: 1% (w/v)). Carrot samples previously treated with sodium bicarbonate were added to the prepared enzyme suspension at a ratio of 1:10 (w/v) and transferred to a 25°C vacuum chamber (J-DV01; Jisco Co., Seoul, Korea). Subsequently, depressurization treatment (applied pressure: 10 kPa) was performed for 1 minute at 3-minute intervals for a total of 12 minutes. After depressurization, the sample was taken out of the enzyme suspension, reacted at 50°C for 1 hour, and then heated for 5 minutes.

Comparative Example 6

Simultaneous sodium bicarbonate treatment and enzyme treatment under reduced pressure conditions

Carrot samples (raw carrots) were added to a suspension (concentration: 1% (w/v)) prepared by adding 1% (v/v) Viscozyme L to a mixed solution of 1.5% (w/v) sodium bicarbonate solution and 0.05 M acetate buffer solution (pH 5.0), and transferred to a 25°C vacuum chamber (J-DV01; Jisco Co., Seoul, Korea). Subsequently, depressurization treatment (applied pressure: 10 kPa) was performed for 1 minute at 3-minute intervals for a total of 12 minutes. After depressurization, the sample was taken out of the enzyme suspension, reacted at 50°C for 1 hour, and then heated for 5 minutes.

In this experiment, the phenomenon of the mixed solution overflowing due to the foaming characteristics of sodium bicarbonate during the processing process was induced, so the experiment could not be conducted smoothly.

Results and Discussion

- The results of comparing the hardness of raw carrots before treatment with the hardness of raw carrots in the cases of decompression enzyme treatment alone (Comparative Example 1), decompression enzyme treatment after heating (Comparative Example 2), decompression enzyme treatment after freezing and thawing (Comparative Example 3), and decompression enzyme treatment followed by sodium bicarbonate treatment (Example 1) are shown in Figure 2a.

According to the above drawing, the hardness (323.62±20.12 10 ⁴ N/㎡) of raw carrots was significantly reduced in both Example 1 and Comparative Examples 1 to 3. Among these, it was confirmed that the hardness of carrots was reduced the most in the case of decompression enzyme treatment after freeze-thaw (Comparative Example 3) and decompression enzyme treatment followed by sodium bicarbonate treatment (Example 1; hardness reduction rate: 97.54%).

- The results comparing the hardness of raw carrots treated with sodium bicarbonate alone (Comparative Example 4), treated with decompression enzyme alone (Comparative Example 1), treated with sodium bicarbonate followed by decompression enzyme treatment (Comparative Example 5), and treated with decompression enzyme followed by sodium bicarbonate treatment (Example 1) are shown in Table 1 and Figure 2b, respectively.

division Hardness (10 ⁴ N/㎡) Comparative Example 4 71.39±7.66 Comparative Example 1 31.20±4.12 Comparative Example 5 13.15±1.92 Example 1 7.93±0.88

According to the above table and drawings, in the case of the two-step process of pressure reducing enzyme treatment and sodium bicarbonate treatment (Example 1), the hardness of carrots was significantly reduced compared to the one-step process such as sodium bicarbonate treatment alone (Comparative Example 4) and pressure reducing enzyme treatment alone (Comparative Example 1).

Moreover, it is noteworthy that when pressure-reducing enzyme treatment was performed after sodium bicarbonate treatment (Comparative Example 5), the hardness reduction effect was low as a result of combining two steps with different time-course factors than in Example 1. This indicates that an unexpected effect was achieved by proceeding with a two-step process of pressure-reducing enzyme treatment followed by sodium bicarbonate treatment.

- The color change (ΔE) measured in each of the cases of decompression enzyme treatment alone (Comparative Example 1), decompression enzyme treatment after heating (Comparative Example 2), decompression enzyme treatment after freezing and thawing (Comparative Example 3), and decompression enzyme treatment followed by sodium bicarbonate treatment (Example 1) compared to the color of the raw carrot before treatment is shown in Table 2 below.

division L ^* a ^* b ^* ΔE raw carrots 51.00±0.74 23.22±0.78 42.09±0.90 - Comparative Example 1 47.29±0.86 15.82±1.08 42.82±1.49 8.65±1.40 Comparative Example 2 46.47±0.51 15.67±0.74 38.00±0.93 9.75±0.60 Comparative Example 3 45.43±0.55 16.11±0.93 39.74±0.94 9.43±1.28 Example 1 46.71±0.81 20.70±1.20 45.09±0.44 6.23±0.70

Referring to the table above, color changes were observed in all treatment groups compared to raw carrots. In particular, the group treated with sodium bicarbonate after decompression enzyme treatment (Example 1) exhibited the smallest ΔE (color difference).

Considering the above results, it is believed that performing sodium bicarbonate treatment after decompression enzyme treatment can not only effectively reduce the hardness of carrots, but also effectively maintain the unique color of carrots.

- The retention rate of beta-carotene was measured in each of the cases where decompression enzyme treatment was performed alone (Comparative Example 1), decompression enzyme treatment after heating (Comparative Example 2), decompression enzyme treatment after freezing and thawing (Comparative Example 3), and decompression enzyme treatment was performed followed by sodium bicarbonate treatment (Example 1), and the results are shown in Table 3 below.

division Beta-carotene (㎍/1 g) Retention rate (%) raw carrots 2090±151.81 100 Comparative Example 1 1671.40±59.72 79.95 Comparative Example 2 1492.27±31.41 71.38 Comparative Example 3 1295.52±63.14 61.97 Example 1 1517.73±16.40 72.60

Referring to the table above, beta-carotene loss was observed across all treatment groups. In this regard, significantly higher beta-carotene loss occurred in the freeze-thaw and decompression enzyme treatment (Comparative Example 3) compared to the other treatment groups. This is believed to be due to the oxidation of beta-carotene during the freeze-thaw process, which destroys the cell wall and cell membrane, leading to a loss of nutrients.

- The changes in the microstructure of carrots with and without decompression enzyme treatment, and after subsequent heat treatment, freeze-thaw treatment, or sodium bicarbonate treatment are shown in Fig. 3.

According to the above diagram, freeze-thaw treatment created wide pores in carrots, but cell walls were destroyed, affecting their structure. In contrast, carrots treated with sodium bicarbonate formed relatively wide pores as cell wall bonds were loosened, and no cell wall destruction was observed.

In this way, it is presumed that when sodium bicarbonate treatment is performed after decompression enzyme treatment, the softening effect of carrots can be maximized while minimizing destruction of cell walls and cell membranes compared to when decompression enzyme treatment is performed after freeze-thawing.

- Optimization of pressure-reducing enzyme treatment and sodium bicarbonate treatment

The change in maximum hardness of carrots according to the concentration of sodium bicarbonate (0.5 to 2.5%) and the depressurization treatment interval (1 to 5 minutes) is shown in Figure 4.

Referring to the above drawing, the pressure reducing enzyme treatment was followed by sodium bicarbonate treatment, and the pressure reducing treatment interval and sodium bicarbonate concentration were each adjusted. At this time, as the pressure reducing treatment interval increased to 2.83 minutes, the hardness tended to decrease, and after 2.83 minutes, the hardness was observed to increase again. In addition, when the concentration of sodium bicarbonate increased to 2.00%, the hardness of the carrots decreased, but it was confirmed that the hardness increased again at concentrations above 2.00%.

Considering the above results, regression analysis was performed to derive optimized results by adjusting the decompression treatment interval and the concentration of sodium bicarbonate, respectively.

The optimal conditions were derived using the mathematical expression 1 described above, and at this time, 10 points were selected using the central composite design method (X _i = X ₁ ; X _j = X ₂ ).

In the above equation, X ₁ was set to a range of 1 to 5 minutes, and X ₂ was set to a range of 0.5 to 2.5%, and each was coded in 5 steps (-2, -1 0, 1, and 2). In the case of X ₁ , 1 minute, 2 minutes, 3 minutes, 4 minutes, and 5 minutes were coded as -2, -1, 0, 1, and 2, respectively, and in the case of X ₂ , 0.5%, 1%, 1.5%, 2%, and 2.5% were coded as -2, -1, 0, 1, and 2, respectively. The decompression interval (minutes), concentration of sodium bicarbonate (%), and hardness (10 ⁴ N/㎡) at 10 measured points are shown in Table 4 below.

No X ₁ X ₂ Decompression treatment interval
(minute) Sodium bicarbonate concentration
(%) hardness
(10 ⁴ N/m ² ) 1 1 1 4.0 2.0 5.46±0.89 2 1 -1 4.0 1.0 19.76±2.71 3 -1 1 2.0 2.0 3.74±1.45 4 -1 -1 2.0 1.0 16.37±2.27 5 0 0 3.0 1.5 8.37±1.46 6 0 0 3.0 1.5 7.55±1.24 7 2 0 5.0 1.5 25.09±1.62 8 -2 0 1.0 1.5 18.02±1.30 9 0 2 3.0 2.5 9.55±0.78 10 0 -2 3.0 0.5 41.27±0.22

Using the SAS program, the results shown in Table 5 below were obtained.

Effect Estimate Stand error t Ratio Significance (P) Model 0.0038** Intercept 65.000859 15.499685 4.19 0.0138** X ₁ -35.041497 10.165140 -3.45 0.0261* X ₂ -17.982772 6.285522 -2.86 0.0459* X ₁ ² 9.319603 1.809965 5.15 0.0067** X ₁ X ₂ -0.839395 2.990962 -0.28 0.7929 X ₂ ² 3.474058 0.719454 4.83 0.0085* Lack of Fit 0.1226

*: means significant (p<0.05)

**: means highly significant (p＜0.01)

At this time, the hardness was calculated as in the following mathematical formula 3.

[Equation 3]

The predicted and measured values derived as described above are shown in Table 6 below.

Sodium bicarbonate concentration (%) Decompression treatment interval (minutes) Hardness (10 ⁴ N/m ² ) Predicted value Actual value 2.00 2.83 4.38 4.61±1.99

According to the above table, when the decompression treatment interval and the concentration of sodium bicarbonate were 2.83 minutes and 2.00%, respectively, the minimum hardness value was predicted to be 4.38 x 10 ⁴ N/㎡, and the actual hardness value was confirmed to be 4.61 x 10 ⁴ N/㎡. From this, the result of R ² = 0.9699 was derived, indicating that the above equation has a high suitability.

Simple modifications or changes of the present invention can be easily utilized by those skilled in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (17)

a) a step of providing a suspension of softening enzyme;
b) a step of immersing root vegetables in the softening enzyme suspension provided in step a), and forming enzyme-containing root vegetables by permeating the softening enzyme into the root vegetables through at least one depressurization treatment, and simultaneously and/or subsequently performing an enzymatic reaction by the softening enzyme in the enzyme-containing root vegetables; and
c) a step of immersing the root vegetables that have undergone the enzymatic reaction in step b) in a solution of carbonate and/or bicarbonate and heat-treating them at 65 to 110°C;
Includes,
At this time, the above depressurization treatment is a method for softening root vegetables, which is performed under pressure conditions controlled at 50 kPa or less. A method characterized in that in the first paragraph, step a) is performed by adding a softening enzyme to a buffer solution and suspending it. A method according to claim 2, characterized in that the buffer solution is a weakly acidic buffer solution and is at least one selected from the group consisting of an acetic acid buffer solution, a phosphate buffer solution, and a citric acid buffer solution. A method characterized in that in the second paragraph, the concentration of the buffer solution is in the range of 0.01 to 50 M, and the pH is set in the range of 1 to 8. A method characterized in that in the second paragraph, the concentration of the enzyme in the buffer solution is controlled in the range of 0.1 to 2% (w/v). A method according to claim 1, characterized in that the softening enzyme is at least one selected from the group consisting of exo-1,4-α-d-glucosidase, cellulase, glucoamylase, α-amylase, xylanase, β-glucanase, pectin lyase, polygalacturonase, endo-1-4-β-xylanase, pullulanase, heat-stable α-amylase, hemicellulase, and arabanase. A method characterized in that in the first paragraph, the amount of root vegetables in the enzyme suspension in step b) is determined in the range of 1 to 50% (w/v). A method according to claim 1, characterized in that the root vegetables are at least one selected from the group consisting of radish, carrot, burdock, bellflower root, deodeok, lotus root, ginseng, beet, taro, and radish. delete A method characterized in that, in the first paragraph, the decompression treatment in step b) is performed multiple times, wherein the interval between the decompression treatments is adjusted in the range of 1 to 5 minutes, and the decompression treatment time per time is adjusted in the range of 0.5 to 2 minutes. A method according to claim 1, characterized in that the enzymatic reaction is performed at 30 to 60°C for 30 to 90 minutes. A method characterized in that, in claim 1, further comprising a step of stopping the enzymatic reaction by heating at 90 to 105°C for 5 to 15 minutes after completion of the enzymatic reaction. A method according to claim 1, wherein the carbonate is sodium carbonate, and the bicarbonate is at least one selected from the group consisting of potassium bicarbonate and sodium bicarbonate. A method characterized in that in the first paragraph, the solution concentration of the carbonate and/or bicarbonate is controlled in the range of 0.5 to 5% (w/v). A method characterized in that in the first paragraph, the heat treatment in step c) is performed for 1 to 30 minutes. A method characterized in that, in the first paragraph, the hardness of the root vegetables that have undergone the step c) is 80,000 N/㎡ or less, and the hardness reduction rate of the root vegetables is at least 90%. A method characterized in that, in the first paragraph, the color difference (ΔE) between the root vegetables added in step b) and the root vegetables that have undergone step c) is 9 or less, and the retention rate of nutrients in the root vegetables that have undergone step c) compared to the root vegetables added in step b) is at least 70%.