Method of improving shelf life of fruits and vegetables

Abstract

To provide a method of improving the shelf life of fruits and vegetables.SOLUTION: The method of improving the shelf life of fruits and vegetables comprises a step of storing fruits and vegetables under refrigeration while they are in contact with a water-absorbent sheet impregnated with a citric acid solution.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for improving the shelf life of fruits and vegetables. [Background technology]

[0002] In recent years, the expansion of the global agricultural market has led to an increase in the volume of Japanese fruit and vegetable exports overseas. Low-temperature management is the most effective method for preserving the quality of fruit and vegetables. Currently, cold chain technology systems have been developed, and long-term, long-distance overseas transport is also conducted via sea transport via cold chains. However, fruit, in particular, suffers from chilling damage during and after long-term cold storage, resulting in problems such as softening, browning, poor ripening, small skin depressions, off-flavors, and spoilage. Chilling damage is thought to occur due to membrane structure changes associated with the phase transition of membrane fatty acids, increased permeability, changes in membrane enzymes, abnormalities in respiratory metabolism, and abnormalities in membranes and enzyme proteins due to reactive oxygen species generated by cold stress. Therefore, quality deterioration due to chilling damage is caused by a different mechanism than normal quality deterioration. For example, treatment with 1-methylcyclopropene (1-MCP), an ethylene inhibitor reported to have quality-preserving effects in various fruits, has been reported to reduce chilling damage but not sufficiently prevent fruit softening (Non-Patent Document 1).

[0003] Known countermeasures against low-temperature damage include low-oxygen and modified atmosphere packaging (MA) technology. The applicant has also discovered that immersing persimmon fruit in a citric acid solution can prevent softening after low-temperature storage, and has already filed a patent application (Patent Document 1). However, in major overseas production areas, packaging in cardboard boxes is practically essential, so in order to export fresh produce overseas, there is a need for consistent quality preservation techniques that are less time-consuming and less costly, and that also include shelf life in local stores. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2024-31798 [Non-patent literature]

[0005] [Non-Patent Document 1] Wanli, Z. et al. Food Frontiers 2023, 4(3), 1127. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention relates to a method for improving the shelf life of fruits and vegetables. [Means for solving the problem]

[0007] The inventors have conducted various studies into technologies for preventing quality deterioration of fruits and vegetables due to low-temperature damage, and have found that if fruits and vegetables are placed in contact with an absorbent sheet material impregnated with an aqueous citric acid solution and then stored in a refrigerator, quality deterioration due to low-temperature damage after being returned to room temperature can be prevented.

[0008] That is, the present invention provides a method for improving the shelf life of fruits and vegetables, which comprises a step of refrigerating and storing the fruits and vegetables in a state in which the fruits and vegetables are in contact with a water-absorbent sheet material impregnated with an aqueous citric acid solution. [Effects of the Invention]

[0009] According to the method of the present invention, deterioration in the quality of fruits and vegetables after refrigerated storage can be suppressed, thereby maintaining the quality of fruits and vegetables even after long-term or long-distance transportation overseas, etc., and extending the sellable period of fruits and vegetables. [Brief explanation of the drawings]

[0010] [Figure 1] Graph showing the change in the percentage of softened fruit after room temperature shelving. [Figure 2] Photographic record of persimmon fruit observations. DETAILED DESCRIPTION OF THE INVENTION

[0011] The method of the present invention for improving the shelf life of fruits and vegetables includes a step of refrigerating and storing the fruits and vegetables in a state in which the fruits and vegetables are in contact with a water-absorbent sheet material impregnated with an aqueous citric acid solution.

[0012] In the present invention, examples of fruits and vegetables include vegetables, fruits, wild plants, mushrooms, etc. Among these, cold-sensitive fruits and vegetables are preferred because they are more likely to provide the effects of the present invention. Examples of cold-sensitive fruits and vegetables include cucumber, watermelon, tomato, eggplant, avocado, persimmon, apple, pear, peach, plum, banana, avocado, lychee, orange, pineapple, mango, etc. From the same perspective, the fruits and vegetables are preferably persimmon, apple, plum, banana, avocado, pineapple, mango, etc., more preferably persimmon, peach, pear, and even more preferably persimmon.

[0013] In the present invention, the persimmon (Diospyros kaki Thunb.) is a fruit tree of the genus Diospyros in the family Ebenaceae. Persimmon varieties include astringent persimmons such as Hiratanenashi, Tonewase, Nakataniwase, Taiten, Koshuhyakume, Hachiya, Fuji, Atago, and Yamato; imperfectly sweet persimmons such as Nishimurawase and Fude; and sweet persimmons such as Jiro, Fuyu, Taishu, and Soshu. While any of these varieties can be used in the present invention, it is preferable to use Tonewase and Hiratanenashi.

[0014] Fruits and vegetables may be treated with 1-methylcyclopropene (1-MCP) after harvest to slow the ripening process. 1-MCP treatment can be achieved by exposing persimmons to a maximum concentration of 1 ppm of 1-MCP for 12 to 24 hours under sealed conditions. 1-MCP treatment is typically carried out using the commercially available Smart Fresh fumigant (available from AgroFresh Japan, LLC). If the persimmon is an astringent persimmon, it may be subjected to astringency removal treatment. Examples of astringency removal treatment include known methods such as carbonic acid removal treatment and alcohol removal treatment. 1-MCP treatment and astringency removal treatment may be performed simultaneously.

[0015] The aqueous citric acid solution used in this step is an aqueous solution in which citric acid or a salt thereof is dissolved, and examples of the salt of citric acid include alkali metal salts such as monosodium citrate, trisodium citrate, and tripotassium citrate. Citric acid or a salt thereof may be a solvate (e.g., a hydrate) or a non-solvate, and both are included. In the present invention, it is preferable to use citric acid or a sodium salt thereof. The citric acid concentration of the aqueous citric acid solution is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, from the viewpoint of the amount required to exhibit the effect and the operability of the treatment.

[0016] The water-absorbent sheet material is a sheet-like material that can be impregnated with an aqueous citric acid solution. Examples of the water-absorbent body that constitutes the water-absorbent sheet material include water-absorbent polymers, pulp, cotton, paper, woven fabric, nonwoven fabric, and mixtures thereof, and the water-absorbent sheet material may be single-layered or multi-layered. From the viewpoint of workability of the packaging material, when cardboard is used, the water-absorbent sheet material is preferably composed of, in order from the side that contacts the fruit or vegetable, a hydrophilized nonwoven fabric, a water-absorbent body, and a back sheet for preventing liquid wetting. On the other hand, when a container such as plastic is used, the presence or absence of a back sheet for preventing liquid wetting is not important. From the viewpoint of the retention performance of the citric acid aqueous solution, the water-absorbent body preferably contains a water-absorbent polymer.

[0017] The hydrophilized nonwoven fabric is preferably a liquid-permeable nonwoven fabric whose surface has been hydrophilized. Examples of the nonwoven fabric include spunbonded nonwoven fabric, spunlace nonwoven fabric, thermal-bonded nonwoven fabric, needle-punched nonwoven fabric, and stitch-bonded nonwoven fabric. Examples of the fibers constituting the nonwoven fabric include natural fibers, synthetic fibers, and semi-natural fibers.

[0018] The water-absorbent polymer is a polymer having water-absorbing properties, and examples thereof include polyacrylic acid or a salt thereof, a crosslinked polyacrylate, a poly(vinyl alcohol / acrylate) copolymer (crosslinked), a starch-acrylate graft copolymer (crosslinked), a polyvinyl alcohol-polymaleic anhydride graft copolymer (crosslinked), a crosslinked carboxymethyl cellulose salt, etc. Examples of the "salt" constituting the water-absorbent polymer include alkali metal salts (sodium salt, potassium salt, lithium salt, etc.), alkaline earth metal salts (calcium salt, magnesium salt, barium salt, etc.), ammonium salts (quaternary ammonium salt, quaternary alkylammonium salt, etc.), etc.

[0019] The liquid-wet-preventing back sheet is liquid-impermeable, and examples thereof include a polyethylene or polypropylene sheet.

[0020] The basis weight (grammage) of the water-absorbent sheet material is not particularly limited, but is preferably 50 to 300 g / m 2 is. The thickness is not particularly limited, but is preferably 0.1 to 5 mm.

[0021] The absorbent sheet material can be manufactured by a known manufacturing method, or commercially available care sheets or pet sheets can be used, such as "Absorbent Sheet" and "Super Absorbent Mat" from Hakujuji Co., Ltd., "Deo Sheet" from Unicharm Corporation, "Neo Sheet" from Kocho Co., Ltd., and "Clean Pet Sheet" from Iris Ohyama Co., Ltd.

[0022] The amount of citric acid solution impregnated into the absorbent sheet material is preferably such that the liquid will not return to the packaging material due to the weight of the fruits and vegetables being stored. 2 When the weight is applied for 30 minutes, the weight is preferably 20 to 300 mg. In this specification, the amount of liquid return can be measured by the following method. * Liquid return amount measurement test For the liquid return test, an absorbent sheet is used after being soaked in an aqueous solution and left to stand for 30 minutes. A filter paper (ADVANTEC, No. 1, 55 mm) is placed on top of the sheet, and a 200 g / 20 cm 2 After applying the weight for 30 minutes, measure the weight of the filter paper. The weight of the filter paper after applying the weight minus the weight before applying the weight is the amount of liquid returning.

[0023] In this step, it is preferable to impregnate the water-absorbent sheet material with eugenol in addition to the aqueous citric acid solution from the viewpoint of improving the shelf life of fruits and vegetables. Eugenol has the chemical formula C 10 H 12 It is one of the essential oil components represented by O2 and is found in plant essential oils such as clove oil and cinnamon oil. These can also be used in place of eugenol. The amount of eugenol impregnated into the water-absorbent sheet material is preferably 0.1 to 10 mM in the aqueous citric acid solution. The mass ratio of eugenol to citric acid [eugenol / citric acid] is preferably 0.001 to 0.1:1.

[0024] In this step, means for contacting the fruits and vegetables with the water-absorbent sheet material impregnated with an aqueous citric acid solution include a method of leaving the fruits and vegetables stationary on the water-absorbent sheet material, a method of covering the fruits and vegetables with the water-absorbent sheet material, a method of individually packaging each piece of fruit and vegetables in the water-absorbent sheet material, etc. Among these, the method of leaving the fruits and vegetables stationary on the water-absorbent sheet material is preferred from the viewpoint of packaging workability. The part of the fruit or vegetable that is to be brought into contact with the water-absorbent sheet material may be any part, such as the whole fruit, the top of the fruit, the calyx (the part where the fruit is attached to the branch), etc. Among these, the calyx is preferred from the viewpoint of transport stability of the fruit after packaging.

[0025] The temperature during refrigerated storage of fruits and vegetables is preferably 0 to 5°C, more preferably 0 to 2°C, and most preferably 0°C. The humidity during refrigerated storage of fruits and vegetables is preferably 70 to 99%.

[0026] In this step, the period for which the fruits and vegetables are kept in contact with the water-absorbent sheet material impregnated with the citric acid aqueous solution and refrigerated is not particularly limited and can be selected as appropriate, but in terms of making it easier to enjoy the effects of the present invention, the period is preferably 10 to 45 days, and more preferably 14 to 30 days.

[0027] In the present invention, the fruits and vegetables are preferably stored in a refrigerated container with low moisture permeability in order to prevent drying.

[0028] After this step, it is preferable to separate the fruits and vegetables from the water-absorbent sheet material. Thus, as shown in the Examples below, fruits and vegetables that have undergone the processes of the present invention have improved shelf life when stored at room temperature after refrigeration. In this specification, improving the shelf life of fruits and vegetables includes the concepts of maintaining the quality of fruits and vegetables and preventing, suppressing, or delaying deterioration in the quality of fruits and vegetables. In the present invention, improving the shelf life of fruits and vegetables preferably refers to preventing, suppressing, or delaying softening, browning, poor ripening, small depressions in the skin, off-flavors, decay, and the like caused by chilling damage to fruits and vegetables, and more preferably refers to preventing, suppressing, or delaying softening and browning of fruit.

[0029] The method for improving the shelf life of fruits and vegetables of the present invention may further include a step of storing the fruits and vegetables at room temperature after the above step. The temperature at which fruits and vegetables are stored at room temperature is preferably 10 to 30°C, and more preferably 15 to 25°C. The storage period at room temperature is not particularly limited, but is preferably 3 days or more, more preferably 7 days or more, and even more preferably 10 days or more, in order to easily enjoy the effects of the present invention.

[0030] In relation to the above-described embodiment, the present invention further discloses the following aspects.

[0031] <1> A method for improving the shelf life of fruits and vegetables, comprising a step of refrigerating and storing the fruits and vegetables in a state where the fruits and vegetables are in contact with a water-absorbent sheet material impregnated with an aqueous citric acid solution.

[0032] <2> The fruit or vegetable is preferably a cold-sensitive fruit or vegetable, more preferably a persimmon, an apple, a plum, a banana, an avocado, a pineapple, or a mango, even more preferably a persimmon, a peach, or a pear, and even more preferably a persimmon. <1> The method for improving the shelf life of fruits and vegetables described in the above. <3> The fruits and vegetables are preferably those that can be stored at room temperature. <1> or <2> The method for improving the shelf life of fruits and vegetables described in the above. <4> The citric acid concentration of the aqueous citric acid solution is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. <1> ~ <3> 2. The method for improving the shelf life of fruits and vegetables according to claim 1, wherein the <5> The amount of citric acid solution impregnated into the water-absorbent sheet material is preferably 200 g / 20 cm in terms of the amount of liquid return. 2 When weighted for 30 minutes, the result is 20 to 300 mg. <1> ~ <4> 2. The method for improving the shelf life of fruits and vegetables according to claim 1, wherein the <6> The water-absorbent sheet material is preferably composed of a hydrophilized nonwoven fabric, a water-absorbent body, and a back sheet for preventing liquid wetting. <1> ~ <5> 2. The method for improving the shelf life of fruits and vegetables according to claim 1, wherein the <7> The water-absorbing sheet material is further impregnated with eugenol. <1> ~ <6> 2. The method for improving the shelf life of fruits and vegetables according to claim 1, wherein the <8> The mass ratio of eugenol to citric acid [eugenol / citric acid] is preferably 0.001 to 0.1:1. <7> The method for improving the shelf life of fruits and vegetables described in the above. <9> The contact of the fruits and vegetables with the water-absorbent sheet material is preferably carried out by placing the fruits and vegetables on the water-absorbent sheet material, by covering the fruits and vegetables with the water-absorbent sheet material, or by individually wrapping each fruit and vegetable in the water-absorbent sheet material, and more preferably by placing the fruits and vegetables on the water-absorbent sheet material. <1> ~ <8> 2. The method for improving the shelf life of fruits and vegetables according to claim 1, wherein the <10> The temperature during refrigerated storage of fruits and vegetables is preferably 0 to 5°C, more preferably 0 to 2°C, and even more preferably 0°C. <1> ~ <9> 2. The method for improving the shelf life of fruits and vegetables according to claim 1, wherein the <11> The refrigerated storage period of the fruits and vegetables is preferably 10 to 45 days, more preferably 14 to 30 days. <1> ~ <10> 2. The method for improving the shelf life of fruits and vegetables according to claim 1, wherein the <12> The improvement in the shelf life of fruits and vegetables is preferably the prevention, suppression or delay of softening, browning, poor ripening, small depressions in the skin, off-flavors or decay due to chilling damage of fruits and vegetables, and more preferably the prevention, suppression or delay of softening or browning of fruits. <1> ~ <11> 2. The method for improving the shelf life of fruits and vegetables according to claim 1, wherein the <13> After the step, a step of storing the fruits and vegetables at room temperature is included. <1> ~ <12> 10. The method for improving storage stability according to claim 1, wherein [Example]

[0033] Examples 1 to 2 and Comparative Examples 1 to 3 Test sample Tone Wase (produced in Nara Prefecture), outdoor-grown Aohide M size persimmons were used for the test, excluding fruits that were extremely ripe after arrival. The persimmons used were subjected to a carbon dioxide removal treatment (CO2 concentration of 95% or more, 25°C, 16 hours) on the same day of harvest. The persimmon fruit weighed 160-200g, the color of the top surface of the fruit was 3.5-4 (standard fruit color value board for fruit, "Fruit Color Chart: General Persimmons", Japan Horticultural Agricultural Cooperative Association), and the softening level was 1 as judged by touch as described below.

[0034] Test conditions On the day of arrival, the product was treated with the agent and stored in a refrigerator (0°C, 20 days), then stored at room temperature and monitored (21±2°C). For the immersion treatments, except for the sheet treatment, all groups were divided into three cardboard boxes.

[0035] [Table 1]

[0036] How to carry out treatment (i) Soaking treatment: 5 L of 1% by mass citric acid (CA) aqueous solution was prepared in a 10 L plastic bucket, and 20-40 persimmons were soaked in it for 30 minutes, then lightly wiped with a Kimtowel and dried at room temperature for 60 minutes (Comparative Example 2).

[0037] (ii) Absorbent sheet treatment: A commercially available absorbent sheet, Salva Super Absorbent Mat 19116 (45 × 60 cm) [Hakujuji Co., Ltd.], was folded in half to fit the size of the cardboard shipping boxes used for persimmons and used as a liner inside the moisture-proof cardboard boxes. The absorbent sheet was impregnated with 250 mL of tap water (Comparative Example 3), 250 mL of a 1% by mass citric acid solution (Example 1), and 250 mL of a 1% by mass citric acid + 1 mM eugenol mixed solution (Example 2), and the calyx surface of the persimmon was brought into contact with the citric acid solution. The amount of liquid wetting out of the absorbent sheet materials in Examples 1 and 2 was measured and found to be 36 to 47 mg. The absorbent sheet was used as a bedding material during refrigerated storage and then removed when it was allowed to cool to room temperature.

[0038] Refrigerated storage practices The persimmons were packed in moisture-proof cardboard boxes (Rengo Co., Ltd.), 20 pieces per box, 40 pieces per box, and a small temperature and humidity logger (Hygrochron, KN Laboratories) was enclosed.The persimmons were then refrigerated and stored in a low-temperature incubator FMU-380I-HC (Fukushima Galilei Co., Ltd.) with the HC mode set to 0.0°C.

[0039] Determining softening and measuring hardness Firmness was measured by tactile evaluation. According to previous reports, fruits with a tactile evaluation index of 3 or higher were judged to be softened, and the softening rate was calculated as the number of softened fruits / total number of fruits x 100%.

[0040] Tactile judgment 1: Stiff enough 2: Overall it's quite soft, but still firm. 3: When pressed with your fingers, it tends to crumble, or some of the flesh becomes waterlogged. 4: Very soft or part of the skin has burst.

[0041] Fruit color The standard fruit color value chart for fruits, "Fruit Color Chart: General Persimmons" [Publisher: Japan Horticultural Agricultural Cooperative Association], was used to judge the color between 3.0 and 10.

[0042] The change in the percentage of softened fruit after shelving at room temperature in the examples and comparative examples is shown in FIG. 1, and photographic records of the observation of persimmon fruit on the 7th, 11th, and 18th days after shelving at room temperature are shown in FIG.

[0043] As shown in Figure 1, no softening of fruit was observed in any of the examples during refrigerated storage up to 20 days, but in Comparative Examples 1 to 3, the fruit began to soften from the third day after being shelved at room temperature from a low temperature. In contrast, in Examples 1 and 2, no softening of fruit was observed until the seventh day after being shelved at room temperature. In particular, in Example 2, the proportion of softened fruit remained at 5% even seven days after being shelved at room temperature.

Claims

1. A method for improving the shelf life of fruits and vegetables, comprising a step of refrigerating and storing the fruits and vegetables in a state where the fruits and vegetables are in contact with a water-absorbent sheet material impregnated with an aqueous citric acid solution.

2. 2. The method for improving the shelf life of a food product according to claim 1, wherein the absorbent sheet material is further impregnated with eugenol.

3. 2. The method for improving the shelf life of claim 1, wherein the contact between the fruit or vegetable and the water-absorbent sheet material is carried out in a state where the fruit or vegetable is left stationary on the water-absorbent sheet material.

4. 2. The method for improving storage stability according to claim 1, wherein the water-absorbent sheet material comprises a hydrophilized nonwoven fabric, a water-absorbent body, and a back sheet for preventing liquid wetting.

5. 2. The method for improving the shelf life of claim 1, wherein the fruits and vegetables are those that are stored at room temperature.

6. The method for improving the shelf life according to claim 1 , further comprising the step of storing the fruits and vegetables at room temperature after the step.

7. The method for improving the shelf life according to any one of claims 1 to 6, wherein the fruit or vegetable is a persimmon (Diospyros kaki).

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