Wasabi rhizome with reduced quality deterioration

Abstract

To provide a horseradish rhizoma whose quality reduction can be suppressed, and a preservation method and a production method therefore.SOLUTION: There is provided a horseradish rhizoma in which a surface thereof is subjected to trimming processing and is preserved for 5 days at 0°C, after the preservation, phenylalanine ammonia lyase activity per 1 mg of protein is less than 0.04 U / mg protein. There are also provided a preservation method for preserving the horseradish rhizoma at a temperature of -5°C or greater and 10°C or lower, and a production method of the horseradish rhizoma comprising (1-1) a step for immersing in the water whose temperature is greater than 40°C and less than 60°C, the horseradish rhizoma, and / or (1-2) a step for immersing the horseradish rhizoma in an ethanol solution, the production method producing the horseradish rhizoma whose quality reduction can be inhibited.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to wasabi rhizomes and a method for preserving the same. The present invention also relates to a method for producing wasabi rhizomes in which quality deterioration is suppressed. [Background technology]

[0002] Wasabi (Eutrema japonicum (Miq.) Koidz., also known as "hon-wasabi") is a spice that has been widely used since ancient times as a seasoning for fish and meat. The pungent taste of wasabi comes from isothiocyanates (mainly allyl isothiocyanate) produced by the enzymatic reaction of glucosinolates (mainly sinigrin) contained in wasabi with myrosinase. In particular, grated fresh wasabi rhizomes have excellent pungent taste and flavor, making them highly valuable. However, fresh wasabi rhizomes easily discolor at the cut surface during storage, reducing their commercial value, making it difficult to commercially distribute fresh wasabi rhizomes.

[0003] Patent Document 1 discloses a method for freezing and preserving spicy vegetables, characterized by adjusting the moisture content of spicy vegetables such as real wasabi after harvest to a range of 20% to 50%, and then freezing and preserving them at a temperature of -16°C or below. Patent Document 1 states that this method solves the problem that spicy vegetables cannot be preserved while maintaining their original color, aroma, and flavor when stored at room temperature using a complete drying method or at low temperatures using a drying method that is close to complete drying.

[0004] Patent Document 2 describes a method for long-term storage of wasabi root (wasabi rhizomes) by enclosing fresh wasabi root in wax or solid paraffin that can maintain plasticity at temperatures below 42°C, and a product produced using the method.

[0005] Patent Document 3 describes a wasabi root preservation device that can preserve and distribute wasabi in an environment equivalent to the wasabi cultivation environment in order to prevent quality deterioration of wasabi root (wasabi rhizome) during distribution.

[0006] Non-Patent Document 1 describes that the evaluation criteria for the freshness of fruits and vegetables differ depending on the type of fruit and vegetable, and there are no standards for evaluating freshness that can be applied to all vegetables and can be quantified.

[0007] Non-Patent Document 2 describes that when cut lettuce was immersed in 50°C hot water for 90 seconds, cooled in 4°C cold water, and then stored in a refrigerator at 4°C for 6 days, browning progressed over time in lettuce without hot water treatment, but browning hardly occurred in lettuce treated with hot water. Non-Patent Document 2 cites that the reason why browning of lettuce was suppressed by hot water treatment is that the hot water treatment reduced the activity of phenylalanine ammonia lyase (PAL), an enzyme involved in the synthesis of polyphenols, which are substrates for browning substances. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 3-98532 [Patent Document 2] Japanese Patent Application Publication No. 8-173026 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-124826 [Non-patent literature]

[0009] [Non-Patent Document 1] "Postharvest Physiology of Fruit and Vegetable Freshness" Food Science and Technology 56, 43-66, 2018 [Non-patent document 2] M. Murata, et al. “Quality of cut lettuce treated by heat shock” Biosci. Biotechnol. Biochem., 68(3), 501-507, 2004 Summary of the Invention [Problem to be solved by the invention]

[0010] As described in Patent Documents 1 to 3, methods for suppressing quality deterioration of wasabi rhizomes during storage have been investigated, but no fully satisfactory method has yet been provided. Therefore, an object of this specification is to provide wasabi rhizomes in which quality deterioration is suppressed, a method for preserving the same, and a method for producing the same. [Means for solving the problem]

[0011] This specification discloses one or more of the following embodiments as means for solving the above problems. [1] Wasabi rhizome, A wasabi rhizome characterized in that the phenylalanine ammonia-lyase activity per mg of protein after surface trimming and storage at 0°C for 5 days is less than 0.04 U / mg of protein (1 U refers to the activity of producing 1 μmol of cinnamic acid from L-phenylalanine per hour at 41°C). [2] A method for preserving the wasabi rhizome according to [1], comprising storing the wasabi rhizome according to [1] at a temperature of -5°C or higher and 10°C or lower. [3] A method for producing wasabi rhizomes in which quality deterioration is suppressed, (1-1) Immersing wasabi rhizomes in water at a temperature of more than 40°C and less than 60°C, and / or (1-2) Immerse wasabi rhizomes in an ethanol solution. A method comprising: [4] The method according to [3], wherein (1-1) is a step of immersing wasabi rhizomes in water at a temperature higher than 40°C and lower than 60°C for a period of 5 minutes to 180 minutes. [5] The method according to [3] or [4], wherein (1-2) is a step of immersing wasabi rhizomes in an ethanol solution of 45 v / v% or more and 90 v / v% or less for 1 minute or more and 10 minutes or less. [6] (2) After (1-1) and / or (1-2), the wasabi rhizomes are refrigerated. The method according to any one of [3] to [5], further comprising: [7] The method according to [6], wherein (2) is a step of storing the wasabi rhizome at a temperature of -5°C or higher and 10°C or lower. [8] A method for producing wasabi rhizomes with suppressed quality deterioration, comprising: (3) Decreasing the phenylalanine ammonia-lyase activity in wasabi rhizomes A method comprising: [9] The method according to [8], wherein (3) is a step of reducing the phenylalanine ammonia-lyase activity of wasabi rhizome so that the phenylalanine ammonia-lyase activity per mg of protein after surface trimming and storage at 0°C for 5 days is less than 0.04 U / mg protein (1 U refers to the activity of producing 1 μmol of cinnamic acid from L-phenylalanine per hour at 41°C).

[10] (4) After (3), store the wasabi rhizome in a refrigerator. The method according to [8] or [9], further comprising:

[11] The method according to

[10] , wherein (4) is a step of storing wasabi rhizomes at a temperature of -5°C or higher and 10°C or lower. [Effects of the Invention]

[0012] The wasabi rhizomes disclosed in this specification are resistant to quality deterioration such as discoloration even when stored under refrigerated conditions for an extended period of time. According to the method for preserving wasabi rhizomes disclosed in this specification, deterioration in the quality of wasabi rhizomes during storage can be suppressed. According to the method for producing wasabi rhizomes disclosed in the present specification, wasabi rhizomes can be produced that are inhibited from deteriorating in quality during refrigerated storage. [Brief explanation of the drawings]

[0013] [Figure 1] Figure 1 shows photographs of the overall appearance of wasabi rhizomes that were trimmed after harvesting, but not treated with hot water, and stored at 0°C for four weeks, before (top) and after (bottom) storage. After four weeks of storage, the cut surface of the petiole scar had turned black. [Figure 2]Figure 2 shows photographs of the base of the petiole and the cut surface of the lower part of the rhizome before (top) and after (bottom) storage of wasabi rhizomes that were trimmed after harvest and stored at 0°C for four weeks without hot water treatment. After four weeks of storage, the base of the petiole had wilted and new shoots had grown. The cut surface of the lower part of the rhizome had turned black. [Figure 3] Figure 3 shows photographs of the overall appearance of wasabi rhizomes that were trimmed after harvest, treated with hot water under condition 7 (45°C for 30 minutes), and stored at 0°C for four weeks, before (top) and after (bottom) storage. Even after four weeks of storage, there was no discoloration and the green color was maintained. [Figure 4] Figure 4 shows photographs of the base of the petiole and the cut surface of the lower rhizome of wasabi rhizomes that were trimmed after harvest, treated with hot water under condition 7 (45°C for 30 minutes), and stored at 0°C for four weeks, taken before (top) and after (bottom) storage. After four weeks of storage, the base of the petiole had not wilted and no new buds were present. The cut surface of the lower rhizome also remained green with no discoloration. [Figure 5] FIG. 5 shows photographs of the appearance of wasabi rhizomes that were trimmed after harvest, treated with hot water under condition 10 (50°C, 10 minutes), and then stored for a certain period of time at 0°C, 5°C, or 15°C. [Figure 6] In Figure 6, the PAL activity per mg of protein in wasabi rhizomes that had been treated with hot water and stored at 0°C for two weeks, immediately after re-trimming, and three, five, and seven days later, is shown by open squares, and the PAL activity per mg of protein in wasabi rhizomes that had not been treated with hot water and stored at 0°C for two weeks, immediately after re-trimming, and three, five, and seven days later, is shown by open circles. [Figure 7] In Figure 7, the PAL activity per mg of protein in wasabi rhizomes that had been treated with hot water and stored at 0°C for 6 weeks, immediately after re-trimming, and 3, 5, and 7 days later, is shown by open squares, and the PAL activity per mg of protein in wasabi rhizomes that had not been treated with hot water and had been stored at 0°C for 6 weeks, immediately after re-trimming, and 3, 5, and 7 days later, is shown by open circles. [Figure 8]The top row of Figure 8 shows photographs of the appearance of alcohol-treated wasabi rhizomes at various time points during storage at 0°C. The bottom row of Figure 8 shows photographs of the appearance of hot water-treated wasabi rhizomes at various time points during storage at 0°C. [Figure 9] In Figure 9, the PAL activity per mg of protein in alcohol-treated wasabi rhizomes is shown by open squares immediately after re-trimming, and 3 days, 1 week, 2 weeks, and 4 weeks later, while the PAL activity per mg of protein in control wasabi rhizomes that were not alcohol-treated is shown by open circles immediately after re-trimming, and 3 days, 1 week, 2 weeks, and 4 weeks later. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Wasabi rhizomes and their preservation methods> A wasabi rhizome according to a first embodiment of the present invention is characterized in that after the surface is trimmed and storage at 0°C for 5 days, the phenylalanine ammonia-lyase activity per mg of protein is less than 0.04 U / mg protein (1 U refers to the activity of producing 1 μmol of cinnamic acid from L-phenylalanine per hour at 41°C).

[0015] The wasabi rhizome according to this embodiment has the unexpected effect of retaining its pre-refrigerated green color for a long period of time, typically four weeks or more, without discoloration when stored in a refrigerator. The wasabi rhizome according to this embodiment also has myrosinase activity, and when the tissue is destroyed by processing such as grating, it can express the aroma and spiciness characteristic of fresh wasabi rhizome.

[0016] The reason why quality deterioration is suppressed in the wasabi rhizomes according to this embodiment is presumed to be because the activity of phenylalanine ammonia lyase (PAL) is reduced, thereby suppressing the production of polyphenols, which serve as substrates for substances that cause browning (blackening), but the mechanism by which quality deterioration is suppressed is not limited.

[0017] The method for measuring PAL activity will now be described in detail.

[0018] The "trimming treatment" of the surface of a wasabi rhizome for measuring PAL activity refers to a treatment in which the entire surface of the wasabi rhizome is scraped off using a peeler. The thickness of the surface portion to be scraped off is not particularly limited, but is, for example, in the range of 0.5 mm to 2.0 mm. The wasabi rhizome before being subjected to the trimming treatment may be a wasabi rhizome in which the petiole scar and the lower part of the rhizome have been cut in advance to expose the cut surface. When the treatment of cutting the petiole scar and the lower part of the rhizome to expose the cut surface is referred to as the "primary trimming treatment," the surface trimming treatment for measuring PAL activity will be referred to as the "secondary trimming treatment" to distinguish it from the primary trimming treatment.

[0019] The present inventors have found that in wasabi rhizomes in which quality deterioration is suppressed, the PAL activity per mg of protein does not increase and is less than 0.04 U / mg protein, preferably less than 0.03 U / mg protein, when stored at 0°C for 5 days after surface trimming, whereas in wasabi rhizomes in which quality deterioration is not suppressed (for example, untreated wasabi rhizomes), although the PAL activity does not increase immediately after surface trimming, the PAL activity per mg of protein increases to 0.04 U / mg protein or more when stored at 0°C for 5 days after trimming.

[0020] PAL activity per mg of protein can be calculated by taking a 0.5 g measurement sample from the surface of a wasabi rhizome that has been trimmed and stored at 0°C for 5 days, obtaining a purified enzyme solution from the measurement sample using the method described in Experiment 2, and measuring the PAL activity and protein amount of the purified enzyme solution using the method described in Experiment 2. The purified enzyme solution can be obtained from the measurement sample by the method described in Experiment 2 according to the following procedure.

[0021] 0.5 g of the measurement sample was mixed with 2.3 mL of 0.2 M boric acid-NaOH buffer (pH 8.8) containing 5 mM 2-mercaptoethanol (0.2 M BB incl. ME), and 0.075 g of polyvinylpolypyrrolidone. The mixture was disrupted for a total of 30 seconds using a Multi-Beads Shocker (Yasui Kikai) (disruption conditions: 3000 rpm). The resulting disrupted solution was transferred to a 1.5 mL tube and centrifuged to collect only the supernatant. The collected supernatant was centrifuged again and the supernatant was recovered. This supernatant was used as the crude enzyme solution.

[0022] A total of 10 mL of 0.2 M BB incl. ME was loaded onto a desalting column, PD MiniTrap G-25 (Cytiva), to equilibrate it. 500 μL of the crude enzyme solution was then loaded onto the equilibrated column, followed by elution with 1 mL of 0.2 M BB incl. ME. The resulting eluate was used as the purified enzyme solution.

[0023] The PAL activity of the purified enzyme solution can be measured by the method described in Experiment 2 according to the following procedure.

[0024] The reaction is initiated by mixing 750 μL of 0.5 M boric acid-NaOH buffer (pH 8.8), 100 μL of 10 mM L-phenylalanine solution, and 150 μL of purified enzyme solution. The reaction temperature is set to 41°C. The absorbance at 290 nm of the reaction solution is measured 5 minutes and 65 minutes after the start of the reaction, and the increase in absorbance between 5 and 65 minutes after the start of the reaction is measured. The absorbance at 290 nm of cinnamic acid solutions with concentrations of 0 μM, 1 μM, 2.5 μM, 10 μM, 25 μM, 50 μM, and 100 μM is measured, and a calibration curve is created. Based on the calibration curve, the amount of cinnamic acid produced by the purified enzyme solution in 1 hour is calculated from the increase in absorbance. One unit is defined as the activity producing 1 μmol of cinnamic acid per hour at 41°C.

[0025] The protein amount of the purified enzyme solution can be measured by the method described in Experiment 2 according to the instructions attached to the 2-D Quant kit (Cytiva).

[0026] The second embodiment of the present invention relates to a method for preserving wasabi rhizomes according to the first embodiment of the present invention, which method comprises storing the wasabi rhizomes at a temperature of -5°C to 10°C. This method suppresses quality deterioration when the wasabi rhizomes are stored for an extended period of time, for example, for four weeks or more. The temperature is preferably -1°C to 6°C, and particularly preferably 0°C to 5°C.

[0027] <First manufacturing method for wasabi rhizomes with reduced quality deterioration> A third embodiment of the present invention comprises: A method for producing wasabi rhizomes in which quality deterioration is suppressed, (1-1) Immersing wasabi rhizomes in water at a temperature of more than 40°C and less than 60°C, and / or (1-2) Immerse wasabi rhizomes in an ethanol solution. The present invention relates to a method comprising:

[0028] The present inventors have discovered that wasabi rhizomes treated with (1-1) (hot water treatment) or (1-2) (alcohol treatment) retain myrosinase activity while reducing PAL activity, and that this has the unexpected effect of suppressing quality deterioration such as discoloration and wilting when stored in a refrigerator for an extended period of time, for example, four weeks or more. The wasabi rhizomes can retain the aroma and pungency characteristic of fresh wasabi rhizomes even after refrigerated storage.

[0029] In (1-1) and (1-2), the wasabi rhizome used as the raw material may be a fresh wasabi rhizome. The wasabi rhizome used as the raw material may be a fresh wasabi rhizome that has been subjected to a primary trimming process in which the petiole scar and the lower part of the rhizome are cut to expose the cut surface. When using fresh wasabi rhizomes that have been subjected to a primary trimming process, it is preferable to carry out the treatments (1-1) and / or (1-2) as soon as possible after the primary trimming process, specifically within 6 hours, preferably within 3 hours, and particularly preferably within 2 hours after the primary trimming process.

[0030] In the hot water treatment (1-1), the temperature of the water is preferably 41°C or higher, more preferably 42°C or higher, more preferably 43°C or higher, more preferably 44°C or higher, more preferably 45°C or higher, and preferably 59°C or lower, more preferably 58°C or lower, more preferably 57°C or lower, more preferably 56°C or lower, more preferably 55°C or lower, more preferably 54°C or lower, more preferably 53°C or lower, more preferably 52°C or lower, more preferably 51°C or lower.

[0031] The hot water treatment in (1-1) is preferably a step of immersing the fabric in water at the above temperature for 5 to 180 minutes, preferably 8 minutes or more, more preferably 9 minutes or more, more preferably 10 minutes or more, and preferably 150 minutes or less, more preferably 140 minutes or less, more preferably 130 minutes or less, more preferably 120 minutes or less.

[0032] The concentration of the ethanol solution used in the alcohol treatment (1-2) is not particularly limited, but is preferably 45 v / v% or more and 90 v / v% or less. The ethanol solution is preferably an aqueous ethanol solution. Examples of ethanol solutions of this concentration include alcohol preparations containing 77 v / v% ethanol, which are commercially available as food additives, and diluted solutions of the alcohol preparations. The diluted solution is preferably a solution diluted with water.

[0033] The time for the alcohol treatment in (1-2) is not particularly limited, but is preferably 1 minute or more, more preferably 2 minutes or more, more preferably 3 minutes or more, and is preferably 10 minutes or less, more preferably 7 minutes or less, more preferably 5 minutes or less.

[0034] A method for producing wasabi rhizomes with suppressed quality deterioration according to a third embodiment of the present invention comprises: (2) After (1-1) and / or (1-2), the wasabi rhizomes are refrigerated. It is preferable that it further comprises

[0035] Refrigerated storage typically refers to storage at a temperature of −5° C. or higher and 10° C. or lower. The temperature is preferably −1° C. or higher and 6° C. or lower, and particularly preferably 0° C. or higher and 5° C. or lower. Wasabi rhizomes that have been treated in (1-1) and / or (1-2) retain myrosinase activity but have reduced PAL activity, and therefore quality deterioration is suppressed when stored for long periods of time, for example, for four weeks or longer.

[0036] <Second method for producing wasabi rhizomes with reduced quality deterioration> A fourth embodiment of the present invention is A method for producing wasabi rhizomes in which quality deterioration is suppressed, (3) Decreasing the activity of phenylalanine ammonia-lyase (PAL) in wasabi rhizomes The present invention relates to a method comprising:

[0037] The present inventors have discovered that wasabi rhizomes to which wasabi rhizome PAL activity has been added have the unexpected effect of suppressing quality deterioration such as discoloration and wilting when stored in a refrigerator for a long period of time, for example, for four weeks or more.

[0038] (3) is preferably a step of reducing the PAL activity of wasabi rhizomes so that the PAL activity per mg of protein after surface trimming and storage at 0°C for 5 days is less than 0.04 U / mg protein, and more preferably a treatment of reducing PAL activity while retaining myrosinase activity, and specifically, is (1-1) and / or (1-2) above.

[0039] A method for producing wasabi rhizomes in which quality deterioration is suppressed according to a fourth embodiment of the present invention includes: (2) After (3), store the wasabi rhizomes in a refrigerator. It is preferred that it further comprises:

[0040] Refrigerated storage typically refers to storage at a temperature of -5° C. or higher and 10° C. or lower. The temperature is preferably -1° C. or higher and 6° C. or lower, and particularly preferably 0° C. or higher and 5° C. or lower. Wasabi rhizomes that have been treated in (3) are prevented from deteriorating in quality when stored for a long period of time, for example, for four weeks or longer. [Example]

[0041] <Experiment 1: Preserving freshness through hot water treatment> Immediately after harvesting the wasabi rhizomes, the petiole scars and the lower part of the rhizomes were cut to expose the cut surface, followed by primary trimming. The base of the petiole growing from the wasabi rhizome was left intact.

[0042] After the first trimming process, the wasabi rhizomes were immersed in warm water (warm water treatment). After the warm water treatment, the water on the surface of the wasabi rhizomes was wiped off, wrapped in paper, then wrapped in a polypropylene bag, and placed in an expanded polystyrene container. The rhizomes were then stored at temperatures of 0°C, 5°C, or 15°C for 2, 4, 6, or 9 weeks, and their condition after storage was observed.

[0043] For comparison, wasabi rhizomes after the first trimming treatment were similarly stored in a refrigerator without being subjected to hot water treatment, and the condition after storage was observed.

[0044] The table below shows the water temperature and time of the hot water treatment, as well as the results of observing the appearance of the wasabi rhizomes under each condition after storing them at 0°C for 4 weeks. Three wasabi rhizomes were treated under each condition.

[0045] [Table 1]

[0046] When wasabi rhizomes that had turned yellow after hot water treatment under conditions 13, 14, and 15 and storage at 0°C for four weeks were eaten, the aroma and spiciness characteristic of fresh wasabi rhizomes were not detected. It was speculated that this was because the enzyme myrosinase, which is responsible for the expression of spiciness, was inactivated by the hot water treatment.

[0047] Figures 1 and 2 show photographs of the appearance of wasabi rhizomes stored at 0°C for four weeks without hot water treatment (condition 1), before (top row of Figure 1, top row of Figure 2) and after (bottom row of Figure 1, bottom row of Figure 2) storage. After storage, the cut surfaces of the wasabi rhizomes had browned and turned black, and the base of the petiole was noticeably wilted. New shoots were also growing from the base of the petiole.

[0048] Figures 3 and 4 show photographs of the appearance of wasabi rhizomes treated with hot water under condition 7 (45°C, 30 minutes) and stored at 0°C for four weeks, taken before (top row in Figure 3, top row in Figure 4) and after (bottom row in Figure 3, bottom row in Figure 4). After storage, the wasabi rhizomes showed no discoloration on the cut surface and maintained their green color. Furthermore, the base of the petiole did not wilt after storage and maintained the same firmness as before storage. No growth of new shoots was observed after storage.

[0049] Figure 5 shows photographs of the appearance of wasabi rhizomes treated with hot water under condition 10 (50°C, 10 minutes) and then stored for a certain period of time at 0°C, 5°C, or 15°C. After 2, 4, and 6 weeks of storage at 0°C, the wasabi rhizomes showed no discoloration and maintained their green color. Although not shown, no discoloration was observed on the cut surface of the wasabi rhizomes treated with hot water under condition 10, even after 9 weeks of storage at 0°C. No discoloration was observed in the wasabi rhizomes after 2 and 4 weeks of storage at 5°C. After 6 weeks of storage at 5°C, black discoloration was observed. After 2 weeks of storage at 15°C, the discoloration turned black.

[0050] Wasabi rhizomes treated with hot water under conditions 5 to 12 retained the aroma and spiciness characteristic of fresh wasabi rhizomes even after 4 weeks of storage at 0°C, confirming that the myrosinase activity involved in the expression of spiciness remained.

[0051] <Experiment 2: Measurement of PAL activity in wasabi rhizomes treated with hot water> The inventors speculate that the reason why the hot water-treated wasabi rhizomes in Experiment 1 did not turn black after refrigerated storage for more than four weeks is that the hot water treatment inactivates PAL (phenylalanine ammonia-lyase), which produces polyphenols that serve as substrates for the substances that cause browning (blackening).

[0052] Using the same procedures as in Experiment 1, wasabi rhizomes were subjected to a primary trimming process immediately after harvest, then to a hot water treatment under Condition 10 (50°C, 10 minutes), and then stored at 0°C for two or six weeks. For comparison, wasabi rhizomes were subjected to a primary trimming process immediately after harvest, and then to a hot water treatment at 0°C for two or six weeks. Ten wasabi rhizomes were prepared for each condition.

[0053] The PAL activity of the wasabi rhizomes thus obtained after hot water treatment and storage at 0°C for 2 or 6 weeks, and of the wasabi rhizomes after storage at 0°C for 2 or 6 weeks without hot water treatment, was measured using the following procedure.

[0054] (Re-cropping) After storage at 0°C for 2 or 6 weeks, the entire epidermis of the wasabi rhizomes was peeled off with a peeler. This operation was called "retrimming treatment."

[0055] Immediately after the re-trimming process, and after storage at 0°C for 3, 5, and 7 days after the re-trimming process, 0.5 g of the surface layer of the wasabi rhizome was collected using a peeler and used as a sample.

[0056] (enzyme extraction) 2-Mercaptoethanol was added to 0.2 M boric acid-NaOH buffer (pH 8.8) to a final concentration of 5 mM (hereinafter referred to as 0.2 M BB incl. ME).

[0057] 0.5 g of the sample, 2.3 mL of 0.2 M BB incl. ME, and 0.075 g of polyvinylpolypyrrolidone were mixed and crushed for a total of 30 seconds using a Multi-Beads Shocker (Yasui Kikai) (crushing conditions: 3000 rpm). The disrupted solution was transferred to a 1.5 mL tube and centrifuged to collect the supernatant. The collected supernatant was centrifuged again and the supernatant was collected. The collected supernatant was used as the crude enzyme solution.

[0058] A total of 10 mL of 0.2 M BB incl. ME was applied to a desalting column, PD MiniTrap G-25 (Cytiva), to equilibrate it. 500 μL of the crude enzyme solution was then added to the equilibrated column, followed by elution with 1 mL of 0.2 M BB incl. ME. The resulting eluate was used as the purified enzyme solution.

[0059] (PAL (phenylalanine ammonia lyase) activity measurement) The reaction was initiated by mixing 750 μL of 0.5 M boric acid-NaOH buffer (pH 8.8), 100 μL of 10 mM L-phenylalanine solution, and 150 μL of purified enzyme solution. The reaction temperature was set at 41°C.

[0060] The absorbance at 290 nm of the reaction solution was measured 5 minutes and 65 minutes after the start of the reaction, and the increase in absorbance between 5 and 65 minutes after the start of the reaction was measured.

[0061] The absorbance at 290 nm of cinnamic acid solutions with concentrations of 0 μM, 1 μM, 2.5 μM, 10 μM, 25 μM, 50 μM, and 100 μM was measured, and a calibration curve was prepared. Based on the prepared calibration curve, the amount of cinnamic acid produced by the purified enzyme solution in 1 hour was calculated from the increase in absorbance. The activity required to produce 1 μmol of cinnamic acid per hour at 41° C. was defined as 1 Unit.

[0062] (protein quantification) The protein amount of the purified enzyme solution was measured according to the instructions attached to the 2-D Quant kit (Cytiva).

[0063] The PAL activity per mg of protein (U / g = μmol / h / mg) of the purified enzyme solution extracted from each sample was calculated.

[0064] (result) In Figure 6, the PAL activity per mg of protein for wasabi rhizomes that had been treated with hot water and stored at 0°C for two weeks, immediately after re-trimming, and three, five, and seven days later, is shown by open squares, and the PAL activity per mg of protein for wasabi rhizomes that had not been treated with hot water and stored at 0°C for two weeks, immediately after re-trimming, and three, five, and seven days later, is shown by open circles.

[0065] In Figure 7, the PAL activity per mg of protein for wasabi rhizomes that had been treated with hot water and stored at 0°C for 6 weeks, immediately after re-trimming, and 3, 5, and 7 days later, is shown by open squares, and the PAL activity per mg of protein for wasabi rhizomes that had not been treated with hot water and stored at 0°C for 6 weeks, immediately after re-trimming, and 3, 5, and 7 days later, is shown by open circles.

[0066] In wasabi rhizomes that had been treated with hot water under condition 10 (50°C for 10 minutes) and then stored at 0°C for 2 or 6 weeks, PAL activity did not increase at any time point after re-trimming.

[0067] On the other hand, in wasabi rhizomes stored at 0°C for 2 or 6 weeks without hot water treatment, PAL activity increased 3, 5, and 7 days after re-trimming. Five and seven days after re-trimming, the PAL activity per mg of protein was 0.03 U / mg or higher in all samples.

[0068] These results support the conclusion that the inactivation of PAL (phenylalanine ammonia lyase) activity by treating wasabi rhizomes with hot water is the reason why discoloration of hot water-treated wasabi rhizomes during refrigerated storage is suppressed.

[0069] <Experiment 3: Preserving freshness with alcohol treatment> As in Experiment 1, immediately after harvesting the wasabi rhizomes, the petiole scars and the lower part of the rhizome were cut to expose the cut surface, and a primary trimming process was performed. The base of the petiole growing from the wasabi rhizome was left intact.

[0070] After the first trimming, the wasabi rhizomes were immersed in an alcohol preparation (food additive) (containing 77% ethanol) for 3 minutes. After immersion, they were washed with water, the water on the surface of the wasabi rhizomes was wiped off, wrapped in paper, then wrapped in a polypropylene bag, and placed in a foam polystyrene container. They were then stored at 0°C for 4 weeks, and their condition was observed before storage, and after 2 and 4 weeks.

[0071] For comparison, similar to Experiment 1, wasabi rhizomes after the first trimming were immersed in 50°C warm water for 10 minutes and stored at 0°C for four weeks, and their condition was observed before storage and after two and four weeks.

[0072] The top row of Figure 8 shows photographs of the appearance of alcohol-treated wasabi rhizomes at various time points after storage at 0°C. The bottom row of Figure 8 shows photographs of the appearance of hot water-treated wasabi rhizomes at various time points after storage at 0°C. Like the hot water-treated wasabi rhizomes, the alcohol-treated wasabi rhizomes did not turn black even after 4 weeks of storage at 0°C.

[0073] The alcohol-treated wasabi rhizomes retained the aroma and spiciness characteristic of fresh wasabi rhizomes even after 4 weeks of storage at 0°C, confirming that the myrosinase activity involved in the expression of spiciness remained.

[0074] <Experiment 4: Measurement of PAL activity in alcohol-treated wasabi rhizomes> In experiment 3, three wasabi rhizomes were prepared that had been treated with alcohol for 3 minutes. As a control, three wasabi rhizomes were prepared that had been subjected to the primary trimming treatment immediately after harvest.

[0075] The entire epidermis of each wasabi rhizome was scraped off with a peeler. This operation was designated the "re-trimming treatment." Unlike Experiment 2, the wasabi rhizomes were not refrigerated prior to the re-trimming treatment.

[0076] Immediately after the retrimming process, and after storage at 0°C for 3 days (0.43 weeks), 7 days (1 week), 14 days (2 weeks), and 28 days (4 weeks), 0.5g of the surface layer of the wasabi rhizome was collected using a peeler and used as a sample. According to the procedure described in Experiment 2, the PAL activity per mg of protein (U / mg = μmol / h / mg) of the purified enzyme solution extracted from each sample was calculated.

[0077] In Figure 9, the PAL activity per mg of protein in the alcohol-treated wasabi rhizomes immediately after re-trimming, and 3 days, 1 week, 2 weeks, and 4 weeks later is shown by open squares, and the PAL activity per mg of protein in the control wasabi rhizomes that were not alcohol-treated immediately after re-trimming, and 3 days, 1 week, 2 weeks, and 4 weeks later is shown by open circles.

[0078] In alcohol-treated wasabi rhizomes, PAL activity did not increase at any time point after re-trimming.

[0079] On the other hand, in the control wasabi rhizomes that had not been treated with alcohol, PAL activity increased 3 days, 1 week, and 2 weeks after re-trimming.

Claims

1. A green fresh wasabi rhizome, A fresh green wasabi rhizome, characterized in that after the surface is trimmed and stored at 0°C for 5 days, the phenylalanine ammonia-lyase activity per mg of protein is less than 0.04 U / mg protein (1 U refers to the activity of producing 1 μmol of cinnamic acid from L-phenylalanine per hour at 41°C).

2. 2. A method for preserving the green fresh wasabi rhizome according to claim 1, comprising storing the green fresh wasabi rhizome according to claim 1 at a temperature of -5°C or higher and 10°C or lower.

3. A method for producing wasabi rhizomes in which quality deterioration is suppressed, (1-1) Immersing wasabi rhizomes in water at a temperature of 45°C or higher and 58°C or lower, or (1-2) Immersing wasabi rhizomes in an ethanol solution A method comprising:

4. The method according to claim 3, wherein (1-1) is a step of immersing wasabi rhizomes in water at a temperature of 45°C or higher and 58°C or lower for 5 minutes to 120 minutes.

5. The method according to claim 3 or 4, wherein (1-2) is a step of immersing wasabi rhizomes in an ethanol solution of 45 v / v % or more and 90 v / v % or less for 1 minute or more and 10 minutes or less.

6. (2) After (1-1) or (1-2), store the wasabi rhizomes in a refrigerator. The method of any one of claims 3 to 5, further comprising:

7. The method according to claim 6, wherein (2) is a step of storing wasabi rhizomes at a temperature of −5° C. or higher and 10° C. or lower.

8. A method for producing fresh green wasabi rhizomes in which quality deterioration is suppressed, (3) A step of reducing the phenylalanine ammonia-lyase activity of wasabi rhizomes so that the phenylalanine ammonia-lyase activity per mg of protein after trimming the surface of the wasabi rhizomes and storing them at 0°C for 5 days is less than 0.04 U / mg protein (1 U refers to the activity of producing 1 μmol of cinnamic acid from L-phenylalanine per hour at 41°C). A method comprising:

9. (4) After (3), store the wasabi rhizomes in a refrigerator. The method of claim 8 further comprising:

10. The method according to claim 9, wherein (4) is a step of storing the wasabi rhizome at a temperature of −5° C. or higher and 10° C. or lower.

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