Litchi fresh-keeping liquid and application thereof

Abstract

The invention belongs to the technical field of fruit preservation, and particularly relates to a litchi preservation solution and application thereof, the litchi preservation solution comprises the following components by weight: 0.5-2% of chitosan, 0.05-0.3% of plant essential oil, 0.05-0.2% of L-cysteine, 0.05-0.2% of gamma-polyglutamic acid, 0.5-3% of citric acid, 0.5-2% of calcium chloride, 0.5-4% of a surfactant, 1-5% of ethylene glycol, and the balance of water. The plant essential oil is composed of lemon essential oil, ginger essential oil and clove essential oil, and the mass ratio of the lemon essential oil to the ginger essential oil to the clove essential oil is (1-4): (1-4): (1-4). The litchi fresh-keeping liquid prepared by the invention is safe and non-toxic, and has an excellent fresh-keeping effect on harvested litchis.

Description

Technical Field

[0001] The invention belongs to the technical field of fruit preservation, and specifically relates to a litchi preservation liquid and application thereof. Background Art

[0002] Litchi is a specialty fruit in South my country. It has high nutritional quality and economic value and is deeply loved by consumers. my country ranks first in the world in terms of litchi cultivation area and total output. However, litchi production and harvesting are in high temperature and high humidity seasons, which are prone to pests and diseases. The use of pesticides has become an important means of preventing and controlling pests and diseases, but unscientific use of pesticides can easily lead to excessive residues, causing certain risks of consumption. Moreover, litchi is a seasonal fruit. After harvest, it has vigorous respiratory metabolism and is easy to rot at room temperature. It has a short shelf life and turns from red to brown during storage, which greatly affects its appeal to consumers. Litchi is a non-respiratory climacteric fruit and is harvested at the fully ripe stage. However, it is very easy to brown and lose color after harvesting. It is also susceptible to infection by pathogens, causing browning of the peel and pathological rot, resulting in a decline in product quality, which seriously restricts its circulation as a commodity and industrial development.

[0003] At present, the commonly used means of post-harvest antibacterial preservation of litchi are physical control, chemical control and biological control. The main physical preservation methods are room temperature storage preservation, low temperature storage preservation, radiation preservation, vacuum preservation, controlled atmosphere preservation, heat treatment preservation, ultrasonic preservation, etc. Among the physical preservation methods, controlled atmosphere preservation and cold storage are the best means to delay the browning and discoloration of fruits and vegetables during post-harvest storage. However, because it requires a lot of equipment and special conditions, it has higher requirements for capital and technical level, and it is difficult to be well applied in rural areas and decentralized processing and management conditions in my country. Chemical preservatives in the storage process of fruits and vegetables in my country are plant growth substances, chemical coatings, fumigation preservatives, natural plant extracts, etc. The advantages of chemical preservation methods are reflected in energy saving and consumption reduction, low equipment investment, low cost of use, simple and easy operation and high safety. This method has a profound impact on preventing and controlling browning and aging of fruits. Biological preservation technology includes four types: plant-based preservatives, animal-based preservatives, microbial-based preservatives, and enzyme-based preservatives. Biological preservatives themselves also have antibacterial effects, preventing fruits from being infected by pathogens and becoming corrupt. Biological preservatives have application advantages such as being biodegradable, safe and non-toxic, and having no side effects.

[0004] This study aims to develop an alternative and safer preservative formula to provide certain technical support for the research and development of post-harvest preservation technology for litchi, which is of great significance to reducing post-harvest losses of litchi and the sustainable and healthy development of the entire litchi industry. Summary of the invention

[0005] The object of the present invention is to provide a litchi preservative liquid and its application. The specific technical scheme is as follows:

[0006] A litchi preservative liquid comprises the following components in percentage by weight: 0.5-2% chitosan, 0.05-0.3% plant essential oil, 0.05-0.2% L-cysteine, 0.05-0.2% gamma-polyglutamic acid, 0.5-3% citric acid, 0.5-2% calcium chloride, 0.5-4% surfactant, 1-5% ethylene glycol, and 100% water;

[0007] Preferably, the plant essential oil is one or more of lemon essential oil, ginger essential oil and clove essential oil;

[0008] Preferably, the plant essential oil is composed of lemon essential oil, ginger essential oil and clove essential oil, and the mass ratio of lemon essential oil, ginger essential oil and clove essential oil is 1-4:1-4:1-4. Preferably, the mass ratio of lemon essential oil, ginger essential oil and clove essential oil is 1-2:1-2:1-2. Preferably, the mass ratio of lemon essential oil, ginger essential oil and clove essential oil is 1:1:1.

[0009] The litchi fresh-keeping liquid of the present invention comprises the following components in percentage by weight: 1% of chitosan, 0.05% of lemon essential oil, 0.05% of ginger essential oil, 0.05% of clove essential oil, 0.1% of L-cysteine, 0.1% of gamma-polyglutamic acid, 1.5% of citric acid, 1% of calcium chloride, 2% of surfactant, 3% of ethylene glycol, and 100% of water.

[0010] The surfactant in the litchi fresh-keeping liquid is Tween 80.

[0011] The lychee fresh-keeping liquid of the present invention is used for preserving lychees after harvest and can be used to delay browning and weight loss of lychee fruits.

[0012] Compared with the prior art, the present invention achieves the following beneficial technical effects:

[0013] Chitosan has good antibacterial effect and can destroy microbial cell membranes through electrostatic action, causing changes in membrane permeability and leading to osmotic imbalance inside microbial cells. This chitosan can form a thin film on the surface of fruits and vegetables, reducing the contact area between lychee and air, inhibiting the respiratory metabolism of lychee, thereby reducing water loss, preventing oxidation and spoilage, and maintaining quality.

[0014] The use of the preservative solution of the present invention to treat litchi fruit can effectively delay the browning and weight loss process of litchi fruit. In particular, compared with treatment BX2-8, treatment BX1 delays the browning and weight loss process of litchi fruit more significantly, and has significant differences from other treatments.

[0015] The compounding of chitosan with plant essential oils (lemon essential oil, ginger essential oil, clove essential oil), L-cysteine, γ-polyglutamic acid, citric acid and calcium chloride can significantly inhibit the browning and decay of litchi fruit and improve the storage quality. DETAILED DESCRIPTION

[0016] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0017] The present invention is further explained below in conjunction with specific implementation modes.

[0018] Example 1: Effects of different preservative solution formulations on the preservation of harvested litchi fruits

[0019] Test materials: glutinous rice cake and litchi

[0020] Experimental agents: chitosan, lemon essential oil, ginger essential oil, clove essential oil, L-cysteine, γ-polyglutamic acid, citric acid, calcium chloride, Tween 80, ethylene glycol; all purchased from the market; the formula of the preservative solution is shown in Table 1.

[0021] Table 1: Preservative liquid formula

[0022]

[0023]

[0024] Note: The content is in percentage by weight.

[0025] Experimental method: Select lychee fruits of uniform size, bright appearance, no mechanical damage, diseases and insect pests, and randomly group them. Soak the lychees in each group of preservative solution and the control group for 5 minutes, take them out and air-dry them at room temperature, and then put them into polyethylene PE self-sealing bags, with 25 per bag and one replicate, and 4 replicates per treatment. Store them in a constant temperature incubator at (28±0.5)℃ and relative humidity of 90%-95%, and measure relevant indicators at storage time points of 0d, 4d, and 8d.

[0026] Test indicators:

[0027] Determination of the browning index of the fruit: The browning of the fruit skin is regarded as a browning grade of 0-4 according to the browning area covering the surface of the fruit. The grading standards for browning of the fruit skin are as follows:

[0028] Level 0: The browning of the peel surface accounts for 0%;

[0029] Level 1: Browning of the fruit skin accounts for 0-5% of the surface area;

[0030] Level 2: Browning accounts for 5-25% of the fruit surface area;

[0031] Level 3: Browning accounts for 25-50% of the fruit surface area;

[0032] Level 4: Browning accounts for 50-100% of the fruit surface area;

[0033] Litchi peel browning index = Σ(browning grade × number of samples of each grade) / (4 × total number of fruits).

[0034] Determination of fruit weight loss rate: 10 fixed litchi fruits were selected and the weight of each fruit was weighed on the electronic scale at 0, 4 and 8 days, and the difference method was used to calculate:

[0035] Weight loss rate (%) = [(initial single fruit weight at 0 days - single fruit weight at the time of measurement) / initial single fruit weight at 0 days] × 100%.

[0036] Results and Analysis

[0037] The browning index of litchi fruits stored at 28°C within 0-8 days is shown in Table 2. The browning of litchi fruits in the control group intensified after 4 days of storage, showing a continuous upward trend, and the browning index reached 0.734 at 8 days; the litchi fruits in the treatment group began to brown at 4 days of storage, and the browning index showed an upward trend with the extension of storage time, but the growth rate of the browning index of the fruit was slower than that of the control group; the use of the preservative solution of the present invention to treat litchi fruits can effectively delay the browning process of litchi fruits. In particular, compared with treatment BX2-8, treatment BX1 delayed the browning process of litchi fruits particularly significantly, and there was a significant difference between other treatments.

[0038] Table 2: Browning index of fruits

[0039] deal with 0d 4d 8d BX1 0 0.115 0.295 BX2 0 0.236 0.541 BX3 0 0.228 0.535 BX4 0 0.230 0.552 BX5 0 0.205 0.483 BX6 0 0.212 0.492 BX7 0 0.191 0.466 BX8 0 0.195 0.470 CK 0 0.285 0.734

[0040] The weight loss rate of litchi fruit in the control group and the treatment group during 0-8 days gradually increased with the extension of storage time. The weight loss rate of fruit in the treatment group was lower than that of fruit in the control group. In particular, compared with treatments BX2-8, treatment BX1 delayed the weight loss process of litchi fruit significantly, which was significantly different from other treatments.

[0041] Table 3: Fruit weight loss rate determination

[0042] deal with 0d 4d 8d BX1 0 2.54 5.85 BX2 0 4.51 7.93 BX3 0 4.40 7.86 BX4 0 4.38 7.80 BX5 0 4.18 8.02 BX6 0 4.10 7.92 BX7 0 4.59 8.46 BX8 0 3.95 7.68 CK 0 6.14 12.85

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit it.

Claims

1. A litchi preservative liquid, characterized in that: The invention comprises the following ingredients in percentage by weight: chitosan 0.5-2%, plant essential oil 0.05-0.3%, L-cysteine ​​0.05-0.2%, gamma-polyglutamic acid 0.05-0.2%, citric acid 0.5-3%, calcium chloride 0.5-2%, surfactant 0.5-4%, ethylene glycol 1-5%, and water to make up 100%; The plant essential oil consists of lemon essential oil, ginger essential oil and clove essential oil, and the mass ratio of the lemon essential oil, the ginger essential oil and the clove essential oil is 1-4:1-4:1-4.

2. The lychee fresh-keeping liquid according to claim 1, characterized in that The mass ratio of lemon essential oil, ginger essential oil and clove essential oil is 1-2:1-2:1-2.

3. The lychee preservative liquid according to claim 2, characterized in that The mass ratio of lemon essential oil, ginger essential oil and clove essential oil is 1:1:

1.

4. The lychee fresh-keeping liquid according to claim 1, characterized in that The invention comprises the following ingredients in percentage by weight: 1% chitosan, 0.05% lemon essential oil, 0.05% ginger essential oil, 0.05% clove essential oil, 0.1% L-cysteine, 0.1% gamma-polyglutamic acid, 1.5% citric acid, 1% calcium chloride, 2% surfactant, 3% ethylene glycol, and 100% water.

5. The lychee fresh-keeping liquid according to any one of claims 1 to 4, characterized in that: The surfactant was Tween 80.

6. Use of the litchi fresh-keeping liquid according to any one of claims 1 to 4 for preserving litchi after harvest.

7. The use according to claim 6, characterized in that Used to delay browning and weight loss of litchi fruit.

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