Low-temperature storage and preservation method for litchis

Abstract

The invention discloses a low-temperature storage and preservation method for litchis. The method comprises the following steps of: removing branches and leaves of fresh litchis which are 80-90% mature, and reserving bare litchis; the fruits pass through a sorting line, and defective fruits are picked out; and soaking the lychee in an ergothioneine and mannitol solution, draining water, packaging the lychee with a moisture-permeable and air-permeable functional fresh-keeping bag, and storing the lychee at the temperature of-1 DEG C to 5 DEG C. According to the fresh-keeping method combining ergothioneine, mannitol and a moisture-permeable and air-permeable functional fresh-keeping bag, the fresh-keeping period of the litchis can be effectively prolonged through natural oxidation resistance and hydration and by matching with humidity adjustment and gas exchange, and the flavor, texture and nutritional ingredients of the litchis are kept. The method not only meets green and environment-friendly requirements, but also can remarkably reduce loss of litchis in transportation and storage, reduce food waste and improve food safety, and is an advanced and efficient fruit fresh-keeping technology.

Description

Technical Field

[0001] The invention relates to a fruit preservation technology, and in particular to a method for preserving lychees based on ergothioneine, mannitol and a moisture-permeable and breathable fresh-keeping bag, which is used for low-temperature storage of lychees, prevents peel browning, reduces fruit rot and prolongs the shelf life. Background Art

[0002] Lychee (Litchi chinensis Sonn.) belongs to the Sapindaceae family, a typical tropical and subtropical fruit, and is one of the most competitive fruits in the international market. my country has a long history of lychee cultivation and rich cultural heritage, with a cultivated area of ​​about 8 million mu, an output of about 2.3 million tons, accounting for about 77% of the world's output, and an output value of about 30 billion yuan. In recent years, the lychee industry has been rapidly improved due to its unique flavor and high water content, which has been deeply loved by consumers around the world. Because lychees mature in high temperature and high humidity seasons, and the lychee fruit itself has a fast metabolism, the quality deteriorates very quickly after harvesting, and it is extremely difficult to store and transport to keep fresh, and the harvest period of lychees is very short. Therefore, it brings great pressure to the sales of lychees, and also seriously restricts the circulation and trade of fresh lychees, affecting the overall benefits of the industry. According to incomplete statistics, the loss of lychees in the circulation process after harvesting exceeds 30%, and the annual loss is about 5 billion yuan.

[0003] Lychees are prone to rot at room temperature. Low-temperature storage can slow down the loss of water, decomposition of nutrients, reduce respiration, slow down the oxidation process of the peel, effectively inhibit the reproduction of certain pathogens, and help maintain the color, taste and nutritional value of lychees, and reduce the quality degradation caused by long storage time. Therefore, low-temperature storage is a good way to preserve lychees.

[0004] In recent years, with the rapid increase in the proportion of litchi e-commerce sales and the nationwide e-commerce logistics, low-temperature storage and transportation has provided a new way for the sale of litchi, realizing "door-to-door" service; however, there are also new problems such as no unified standards for post-harvest processing, low-temperature damage, and serious losses during low-temperature circulation, which have profoundly affected consumers' impression and confidence in litchi. At the same time, in terms of export, some European countries require litchi to be stored in an environment of 0.99℃ for more than 15 days to eliminate quarantine pests. If litchi that has been treated in this way is not treated for freshness, it is easy to cause the peel to turn brown or black, bacteria and mold to multiply, and the commodity value to deteriorate. At present, most of the sulfur treatment technology used at home and abroad to protect the color and preserve the freshness of litchi has problems such as excessive sulfur dioxide, poor pulp flavor, and environmental impact. Therefore, the development of sulfur dioxide-free litchi color preservation technology is an urgent problem to be solved by the litchi industry.

[0005] Ergothioneine is a derivative of L-histidine, a natural metabolite of histidine with antioxidant properties. It is commonly found in plants and animals and is present in many human foods. Using ergothioneine to preserve lychees has the following effects: 1) Antioxidant effect. Ergothioneine can effectively remove free radicals in the body, reduce oxidative stress, and protect cells from oxidative damage; 2) Cell protection effect: It can protect cells from various harmful factors through antioxidant effects; 3) Avoid the occurrence of chilling damage. The use of ergothioneine can effectively prevent chilling damage to lychees during low-temperature storage, and can effectively protect the color of the lychee peel during low-temperature storage. Even after thawing for a period of time, the color of the lychee peel is still brighter.

[0006] As a sugar alcohol, mannitol has a good osmotic protection effect. It can reduce the water loss of litchi under low temperature conditions and effectively inhibit the occurrence of chilling injury. The protective film formed by mannitol in the cells helps to maintain the crisp and tender taste of litchi and avoid softening during storage.

[0007] Functional fresh-keeping bags play several key roles in the low-temperature storage of lychees: 1. Controlling humidity and reducing water loss so that water vapor can penetrate appropriately, thereby preventing the bag from being too humid or dry. An overly humid environment may cause the lychees to rot, while excessive water loss will cause the flesh to shrivele and lose its original taste; 2. Regulation of oxygen and carbon dioxide. Excessive carbon dioxide may cause the lychees to respire too quickly, prompting aging and decay. Breathable bags can delay respiration and slow down the aging process of fruits; 3. Temperature stability and protection against chilling damage Lychees are prone to chilling damage at low temperatures due to their high moisture content and cell structure. If the skin turns black and the flesh softens, the breathable fresh-keeping bag can help regulate the microclimate inside the bag and reduce the risk of chilling damage to lychees; Keep the temperature stable: Through gas exchange and humidity control inside the bag, the fresh-keeping bag can buffer the impact of external temperature fluctuations on lychees to a certain extent, help maintain temperature stability, and avoid fruit damage caused by excessive temperature differences; 4. Reduce the growth of bacteria and molds. Excessively high humidity environments easily provide breeding conditions for bacteria and molds, while breathable fresh-keeping bags can effectively prevent excessive accumulation of moisture inside the bag, reduce the growth space of bacteria or molds, and thus effectively inhibit the decay of lychees. 5. Delay the aging process Ethylene is an important hormone in the aging process of plants. The breathable fresh-keeping bag can reduce the accumulation of ethylene by regulating gas exchange, delaying the ripening and aging process of lychees. Proper gas circulation helps maintain the physiological activity of lychees and prolong their freshness. Maintain color and texture: By controlling the humidity and gas composition in the environment, the moisture-permeable and breathable fresh-keeping bag can effectively maintain the color, hardness and freshness of litchi, and prevent the skin from browning and the flesh from softening. Summary of the invention

[0008] The invention provides a method for storing and preserving litchi at a low temperature (-1 DEG C to 5 DEG C) by combining ergothioneine and mannitol and packaging them in a functional fresh-keeping bag.

[0009] Ergothioneine can inhibit the oxidation reaction of the peel and pulp cells, reduce the browning of litchi and extend the storage period. Mannitol can maintain the loss of water from the peel during storage and replenish water in time to prevent the peel from browning. The treated litchi is packed into a moisture-permeable and breathable functional fresh-keeping bag to avoid water evaporation and perform micro-atmosphere adjustment in the storage environment. In a low-temperature environment, the browning and aging process of the litchi peel is inhibited, water loss is reduced, its shelf life is extended, and its original flavor, nutrition and texture are maintained.

[0010] The low-temperature storage and fresh-keeping method of litchi of the present invention comprises the following steps:

[0011] Take 80-90% ripe fresh lychees, remove branches and leaves, and keep the bare fruits; pass through the sorting line to pick out the defective fruits; then soak them in ergothioneine and mannitol solution, drain the water, pack the lychees in moisture-permeable and breathable functional fresh-keeping bags, and store them at -1℃ to 5℃.

[0012] Preferably, the soaking is in a solution containing 0.05% to 0.5% ergothioneine and 0.1% to 1% mannitol by mass fraction.

[0013] Preferably, the soaking time is 3-5 minutes.

[0014] The storage temperature is preferably 0±1°C.

[0015] Advantages of the present invention:

[0016] 1. Extend the shelf life of litchi

[0017] Ergothioneine is a natural antioxidant that can effectively inhibit oxidation reactions, delay the aging process of litchi at low temperatures, and prevent the fruit from discoloring and deteriorating.

[0018] Mannitol can reduce the water loss of litchi during low-temperature storage, maintaining the moisture and crisp texture of the pulp.

[0019] The moisture-permeable and breathable fresh-keeping bag prevents litchi from rotting due to excessive moisture or water and delays aging by regulating humidity and air circulation.

[0020] 2. Prevent low temperature damage

[0021] Lychees are prone to chilling damage at low temperatures. If black spots appear on the skin and the flesh softens, moisture-permeable and breathable fresh-keeping bags can help prevent this chilling damage by regulating the internal microenvironment.

[0022] This fresh-keeping bag can prevent moisture accumulation on the surface and flesh of litchi due to condensation, thereby reducing damage to the fruit caused by low temperature.

[0023] 3. Maintain the original flavor and texture

[0024] Mannitol not only prevents water loss, but also helps maintain the original flavor and texture of lychees and prevents the fruit from drying out or becoming soft due to lack of water.

[0025] By adjusting the humidity and gas exchange in the bag, the moisture-permeable and breathable fresh-keeping bag can maintain the appearance and taste of litchi, avoiding excessive dehydration and deterioration of taste.

[0026] The preservation method combining ergothioneine, mannitol and moisture-permeable and breathable fresh-keeping bags can effectively extend the shelf life of litchi and maintain its flavor, texture and nutrients through natural antioxidant and hydration effects, humidity regulation and gas exchange. This method not only meets green environmental protection requirements, but also significantly reduces the loss of litchi during transportation and storage, reduces food waste, and improves food safety. It is an advanced and efficient fruit preservation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the experimental result of control group 1;

[0028] Figure 2 This is the experimental result of control group 2;

[0029] Figure 3 This is the experimental result of control group 3;

[0030] Figure 4 It is the experimental result of Example 1;

[0031] Figure 5 It is the experimental result of Example 2;

[0032] Figure 6 This is the experimental result of Example 3. Specific embodiments

[0033] The following examples are provided to further illustrate the present invention, rather than to limit the present invention.

[0034] Comparative Example 1:

[0035] Take 80-90% ripe fresh lychees, remove branches and leaves, and keep the bare fruits; pass through the sorting line to pick out the defective fruits; then soak in water for 3-5 minutes, pass through the drain conveyor belt; after draining the water, pack the lychees in moisture-permeable and breathable functional fresh-keeping bags, store at 0±1℃, take out the lychees after 20 days, and place them at room temperature for 30 minutes. The peel turns brown by 95%, and the flesh is slightly self-dissolved and the sugar is obviously lost ( Figure 1 ).

[0036] Comparative Example 2:

[0037] Take 80-90% ripe fresh lychees, remove branches and leaves, and keep the light fruits; pass through the sorting line to pick out the defective fruits; then soak in a 0.15% mannitol solution for 3-5 minutes, and pass through a drain conveyor belt; after draining the water, pack the lychees in a moisture-permeable and breathable functional fresh-keeping bag, store at 0±1℃, take out the lychees after 20 days, and after leaving at room temperature for 30 minutes, the peel is 67% brown, and the flesh is slightly self-dissolved and sugar is lost ( Figure 2 ).

[0038] Comparative Example 3:

[0039] Take 80-90% ripe fresh lychees, remove branches and leaves, and keep the light fruits; pass through a sorting line to pick out defective fruits; then soak in a 0.15% ergothioneine solution for 3-5 minutes, and pass through a drain conveyor belt; after draining the water, pack the lychees in a moisture-permeable and breathable functional fresh-keeping bag, store at 0±1°C, take out the lychees after 20 days, and after being placed at room temperature for 30 minutes, the peel turns brown by 55%, and the pulp is slightly autolyzed ( Figure 3 ).

[0040] Embodiment 1:

[0041] Take 80-90% ripe fresh lychees, remove branches and leaves, and keep the light fruits; pass through a sorting line to pick out defective fruits; then soak in a solution of 0.05% ergothioneine and 0.1% mannitol by mass for 3-5 minutes, and pass through a draining conveyor belt; after draining the water, pack the lychees in a moisture-permeable and breathable functional fresh-keeping bag, store at 0±1°C, take out the lychees after 20 days, and after being placed at room temperature for 30 minutes, the browning of the peel is less than 5%, the flesh maintains a good taste and flavor, and there is no sugar fading and autolysis phenomenon ( Figure 4 ).

[0042] Embodiment 2:

[0043] Take 80-90% ripe fresh lychees, remove branches and leaves, and keep the light fruits; pass through a sorting line to pick out defective fruits; then soak in a solution of 0.5% by mass ergothioneine and 0.1% by mass mannitol for 3-5 minutes, and pass through a draining conveyor belt; after draining the water, pack the lychees in a moisture-permeable and breathable functional fresh-keeping bag, store at 0±1°C, take out the lychees after 20 days, and after being placed at room temperature for 30 minutes, the browning of the peel is less than 3%, the flesh maintains a good taste and flavor, and there is no sugar fading and autolysis phenomenon ( Figure 5 ).

[0044] Embodiment 3:

[0045] Take 80-90% ripe fresh lychees, remove branches and leaves, and keep the light fruits; pass through a sorting line to pick out defective fruits; then soak in a solution of 0.5% ergothioneine and 1% mannitol by mass for 3-5 minutes, and pass through a draining conveyor belt; after draining the water, pack the lychees in a moisture-permeable and breathable functional fresh-keeping bag, store at 0±1°C, take out the lychees after 20 days, and after being placed at room temperature for 30 minutes, the peel browns by 4%, and the flesh maintains a good taste and flavor, and there is no sugar fading and autolysis phenomenon ( Figure 6 ).

Claims

1. A method for storing and preserving litchi at low temperature, characterized in that: The following steps are involved: Take 80-90% ripe fresh lychees, remove branches and leaves, and keep the bare fruits; pass through the sorting line to pick out the defective fruits; then soak them in ergothioneine and mannitol solution, drain the water, pack the lychees in moisture-permeable and breathable functional fresh-keeping bags, and store them at -1℃ to 5℃.

2. The method for low temperature storage and fresh-keeping of litchi according to claim 1, characterized in that: The soaking is soaking in a solution with a mass fraction of 0.05%-0.5% ergothioneine and a mass fraction of 0.1%-1% mannitol.

3. The method for low temperature storage and fresh-keeping of litchi according to claim 1, characterized in that: The soaking time is 3-5 minutes.

4. The method for low temperature storage and fresh-keeping of litchi according to claim 1, characterized in that: The storage temperature is 0±1°C.

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