Method for preserving litchi fruits by using sucrose and application
阅读说明：本技术 一种利用蔗糖保鲜荔枝的方法及应用 (Method for preserving litchi fruits by using sucrose and application ) 是由 朱世江 曲姗姗 李萌萌 王光 于 2020-12-31 设计创作，主要内容包括：本发明提供了一种利用蔗糖保鲜荔枝的方法及应用,将1～10μmol/L的蔗糖水溶液喷布在荔枝果实表面,然后采用聚乙烯塑料薄膜袋包装、储藏,可降低荔枝的多酚氧化酶活性和活性氧含量,从而有效控制荔枝果皮褐变和腐烂的发生,本发明的保鲜方法操作简单、成本低、绿色安全、施用效率高,有效延长荔枝的贮藏期,减少荔枝在流通环节的经济损失。(The invention provides a method for preserving litchi fruits by using sucrose and application thereof, wherein 1-10 mu mol/L sucrose aqueous solution is sprayed on the surfaces of litchi fruits, and then the litchi fruits are packaged and stored by polyethylene plastic film bags, so that the polyphenol oxidase activity and the active oxygen content of the litchi fruits can be reduced, and the browning and the decay of litchi peel can be effectively controlled.)
1. The litchi preservative is characterized by being a sucrose aqueous solution with the concentration of 1-10 mu mol/L.
2. A litchi fresh-keeping method is characterized in that a sucrose aqueous solution is sprayed on the surfaces of litchi fruits, and the concentration of the sucrose aqueous solution is 1-10 mu mol/L.
3. The method according to claim 1, wherein the concentration of the sucrose aqueous solution is 5 to 10 μmol/L. Most preferably 10. mu. mol/L.
4. The method of claim 1 or 2, wherein the preservation is a reduction in browning of litchi pericarp and/or a reduction in litchi fruit decay.
5. The method of claim 1 or 2, wherein the litchi is not harvested or not more than 24 hours after harvesting.
6. The method of claim 5, wherein the non-harvested litchi is litchi to be harvested within 1-40 days.
7. The method as claimed in claim 1 or 2, wherein the litchi fruits are sprayed with the sucrose aqueous solution, and then packed in polyethylene plastic film bags and stored at 20-25 ℃.
8. The method according to claim 7, wherein the polyethylene plastic film bag has a thickness of 0.02 to 0.04 mm.
9. The method according to claim 1 or 2, wherein the water is distilled water, tap water, well water, mineral water or purified water.
10. Use of the method of any one of claims 1 to 9 for the preservation of litchi.
Technical Field
The invention relates to the technical field of fruit preservation, and particularly relates to a method for preserving litchi chinensis Sonn by using sucrose and application of the method.
Background
Litchi (lichi chinensis Sonn.) is a soapberry family, belongs to evergreen arbor fruit trees, is one of the important fruits in tropical and subtropical zones of China, is mainly distributed in the provinces of Hainan, Guangdong, Guangxi, Fujian and the like of China, belongs to the noble fruits in the subtropical zones, is one of the four famous fruits in Lingnan, and is known as 'Lingnan good fruit'. It is native to the south of China and has a cultivation history of more than 2000 years. At present, litchi is the first big fruit in tropical and subtropical areas of China, ranks fifth in fruit industry in China, is a big post industry of agricultural economy in south China, and is also an important source of economic income of local farmers. Litchi is a subtropical good fruit which is popular in China in ancient times, because the litchi is unique in shape, has stigmatic and raised peel, and is bright red in color and pleasant to the eyes when ripe. However, litchi is ripe in summer, and is in a hot weather in the market season, and the litchi is easy to rot after being harvested, so that the litchi has a saying of color change in one day, taste change in two days and mildew in three days. Under the condition of normal temperature, the litchi peels are easy to brown, and once the litchi peels are brown, the commercial value of the litchi peels is lost even if the pulp is edible. Moreover, the quality of the flesh is quickly deteriorated after the litchi is browned. The reason is that the main reason for browning of litchi is that the peel loses water, the disease resistance of the dehydrated peel is reduced, and the litchi is easy to be infected by diseases and rotten, so that flesh is driven to be rotten.
The method for preventing and treating the browning of the litchi peels is researched at home and abroad and comprises the steps of plastic bag packaging, heat treatment, low-temperature treatment, film coating and the like, and the application of chemical preservatives, biological preservatives and the like or the adoption of sulfur dioxide fumigation or slow release technology and the like. However, these methods have significant disadvantages, for example, the browning caused by water loss can be reduced by packaging with plastic film bags, but since the humidity of the air in the bags is increased, which is beneficial to the growth and infection of pathogenic bacteria, if the bags are not sterilized with chemical bactericides, the bags are easy to rot, but if the bags are sterilized with chemical bactericides, the bags can cause pesticide residue. In addition, although the effect of controlling browning through low-temperature treatment, storage and transportation is good, the cold-chain logistics conditions are limited at present, and the method cannot be popularized in various places and is difficult to popularize; moreover, the low-temperature treatment technology must be combined with the packaging of plastic film bags, the good effect can be achieved only by continuously maintaining the low-temperature condition, and the lichees are still easy to brown and rot after returning to the normal-temperature condition from the low temperature. The effect of preventing browning by sulfur dioxide fumigation or slow release technology is good, but the color is required to be compounded by acid treatment, the color of the litchi peel after being compounded is not bright enough, and the acceptance degree of consumers is reduced. The effects of heat treatment, film coating, biological antistaling agent and the like on preventing browning are unstable, and the popularization and application in production are difficult. For example, patent CN103734290B provides a litchi preservative, which is an aqueous solution prepared from lignin, sucrose ester, sodium sorbate, citric acid, potassium chloride, calcium stearate, and chitin, and can prolong the preservation period by 20-30 days after litchi is soaked. Therefore, the preservative has more components, is inconvenient to prepare for most fruit growers, belongs to a chemical preservative, and has certain side effects inevitably.
Therefore, a green, safe, simple and effective fresh-keeping method for controlling browning and rotting of litchi is found, and is quite necessary for promoting the healthy development of the litchi industry.
Disclosure of Invention
The invention aims to overcome the defects of the existing litchi preservation technology and provides a method for preserving litchi by utilizing cane sugar and application thereof.
The invention aims to provide a litchi preservative.
The invention also aims to provide a litchi fresh-keeping method.
The invention further aims to provide the application of the method in litchi preservation.
The above purpose of the invention is realized by the following technical scheme:
the invention provides a litchi preservative which is a sucrose aqueous solution with the concentration of 1-10 mu mol/L.
Sucrose, alternative name of english: d- (+) -Sucrose, a type of disaccharide, is prepared by condensing and dehydrating a molecule of hemiacetal hydroxyl group of glucose and a molecule of hemiacetal hydroxyl group of fructose with each other. Molecular formula C12H22O11The molecular weight is 342.297, sucrose is a sugar widely synthesized in plants, and glucose synthesized by plant photosynthesis needs to be converted into sucrose to be transported to other parts.
During the storage period of litchi, the peel tissue is gradually aged, so that the endomembrane system is damaged, and meanwhile, the activities of polyphenol oxidase and peroxidase are improved along with the time, and are contacted with anthocyanin serving as a substrate, so that anthocyanin of the litchi peel is degraded and oxidized into black quinone substances, and the litchi peel is browned. The method sprays the sucrose aqueous solution on the surface of the litchi fruits, can effectively reduce the activity of polyphenol oxidase and reduce the degradation and oxidation of anthocyanin, thereby reducing the content of generated black quinone substances. When the concentration of the sucrose solution is 1-10 mu mol/L, the polyphenol oxidase is the lowest, the anthocyanin is degraded the least, and the browning of the litchi peel can be effectively controlled; meanwhile, when the concentration of the sucrose solution is 1-10 mu mol/L, the content of free radicals (including superoxide anions and hydrogen peroxide) in the litchi peels is the lowest, so that the active oxygen content of the litchi can be effectively reduced, cell membranes are protected, the peel aging is delayed, the disease resistance of the peels is kept, and the browning and the rotting of the litchi peels are effectively controlled.
The invention also provides a litchi fresh-keeping method, which comprises the step of spraying the sucrose aqueous solution on the surfaces of litchi fruits, wherein the concentration of the sucrose aqueous solution is 1-10 mu mol/L.
After the litchi fruits sprayed with the sucrose aqueous solution are harvested or the litchi fruits sprayed with the sucrose aqueous solution are packaged by a polyethylene plastic film bag with the thickness of 0.02-0.04 mm, the polyphenol oxidase activity and the free radical content of the litchi can be effectively reduced, and therefore browning and rotting of litchi peels can be effectively controlled. The invention has the advantages of simple operation, low cost, high application efficiency, safety and innocuity to the ecological environment and human health, and good fresh-keeping effect.
The normal-temperature shelf life of the litchi fruits preserved by adopting the prior art is only 3-5 days, and the postharvest loss of the litchi fruits is about 20%. By adopting the method for preserving the litchi chinensis Sonn, the storage period of the litchi chinensis Sonn can be prolonged to 7-10 days, and the postharvest loss of the litchi chinensis Sonn is reduced. The annual litchi yield of China is about 200 ten thousand tons, the postharvest loss caused by various factors is about 40 ten thousand tons every year, and the postharvest loss caused by pericarp browning and rotting is about 20 ten thousand tons; by adopting the technology of the invention, the direct economic benefit can be generated by 12 hundred million yuan per kilogram of litchi by 6 yuan per kilogram. Meanwhile, the technology prolongs the storage period of the litchi, can effectively reduce the economic loss of circulation loop, can solve the problem of difficult fruit selling of farmers, is beneficial to increasing the income of the farmers, can increase the litchi export, and earns more foreign exchanges for the country.
Preferably, the concentration of the sucrose aqueous solution is 5-10 mu mol/L.
Most preferably, the concentration of the aqueous sucrose solution is 10. mu. mol/L.
Preferably, the freshness preservation refers to the reduction of litchi pericarp browning and/or the reduction of litchi fruit decay.
Preferably, the litchi is not harvested or is not more than 24 hours after harvesting.
Preferably, the non-harvested litchi is litchi to be harvested within 1-40 days.
Preferably, the litchi fruits are sprayed with the sucrose aqueous solution, packaged by polyethylene plastic film bags and stored at 20-25 ℃.
Preferably, the thickness of the polyethylene plastic film bag is 0.02-0.04 mm.
Preferably, the water is distilled water, tap water, well water, mineral water or purified water.
The invention also protects the application of the method in litchi preservation.
Compared with the prior art, the invention has the beneficial effects that:
the method for controlling normal-temperature storage of litchi fruits by using sucrose can reduce polyphenol oxidase activity and active oxygen content of litchi fruits by only spraying 1-10 mu mol/L sucrose solution on the surfaces of litchi fruits, thereby effectively controlling browning and rotting of litchi peels, and having the advantages of safety, no toxicity to ecological environment and human health and good preservation effect.
The litchi chinensis juice and litchi chinensis juice preparation method is simple to operate, low in cost, green, safe and high in application efficiency, prolongs the storage period of litchi chinensis, and can effectively reduce economic loss in a circulation link.
Drawings
FIG. 1 is a graph showing the effect of sucrose treatment on litchi preservation in example 1.
Detailed Description
The invention will be further described with reference to the drawings and the detailed description, which are not intended to limit the invention in any way. The starting reagents employed in the examples of the present invention are, unless otherwise specified, those that are conventionally purchased.
Example 1 litchi preservation method
1. Adding distilled water into sucrose to prepare 1 mu mol/L sucrose aqueous solution;
2. spraying 1 μmol/L sucrose water solution on the surface of freshly harvested fructus litchi fruits, packaging with 0.03 mm polyethylene plastic film bag, and storing in 20 deg.C storage.
Example 2 litchi preservation method
1. Adding distilled water into sucrose to prepare a sucrose aqueous solution with the concentration of 3 mu mol/L;
2. spraying 3 mu mol/L sucrose water solution on the surface of litchi fruits 18 hours after harvesting, packaging the litchi fruits after spraying with 0.03 mm polyethylene plastic film bags, and storing in a storage at 20 ℃.
Embodiment 3 litchi preservation method
1. Adding distilled water into sucrose to prepare a sucrose aqueous solution with the concentration of 5 mu mol/L;
2. spraying 5 mu mol/L sucrose water solution on the surface of litchi fruits 24 hours after harvesting, packaging the litchi fruits after spraying with 0.02 mm polyethylene plastic film bags, and storing in a storage at 25 ℃.
Example 4 litchi preservation method
1. Adding distilled water into sucrose to prepare a sucrose aqueous solution with the concentration of 7 mu mol/L;
2. spraying 7 μmol/L sucrose water solution on the surface of litchi fruit harvested after 5 days, packaging litchi fruit with 0.03 mm polyethylene plastic film bag after harvesting, and storing in 20 deg.C storage.
Example 5 litchi preservation method
1. Adding distilled water into sucrose to prepare 10 mu mol/L sucrose aqueous solution;
2. spraying 10 μmol/L sucrose water solution on the surface of fructus litchi 12 hr after harvesting, packaging with 0.04mm polyethylene plastic film bag, and storing in 22.5 deg.C storage.
Example 6 litchi preservation method
1. Adding distilled water into sucrose to prepare 10 mu mol/L sucrose aqueous solution;
2. spraying 10 μmol/L sucrose water solution on the surface of litchi fruit harvested after 40 days, packaging litchi fruit with 0.04mm polyethylene plastic film bag after harvesting, and storing in 22.5 deg.C storage.
EXAMPLES 1 to 6 effects
After 8 days of storage, the peel browning index and the rotting rate of the litchis sprayed with 1-10 mu mol/L sucrose aqueous solution in examples 1-6 were respectively tested, and the control treatment group consisted of spraying the litchis with distilled water, packaging with 0.04mm polyethylene plastic film bags, and storing in a storage warehouse at 22.5 ℃. The results are shown in Table 1.
TABLE 1
Note: assessment of the severity of browning of the pericarp reference is made to the method of Scott et al (1982). The browning degree of the litchi peels is classified into 1-5 grades. Level 1: the peel is all red; and 2, stage: the ratio of the browning area to the total area is less than 25 percent; and 3, level: the browning area accounts for 25 to 50 percent; 4, level: the browning area accounts for 50 to 75 percent; and 5, stage: the browning area is greater than 75% to complete browning. The browning index is ∑ (number of browning fruit at each stage × number of browning stages)/total number of investigation fruits;
storing the collected litchi for 8 days; the difference of the surfaces of different letters after the number is extremely obvious (P is less than or equal to 0.01).
The reduction in browning index and the reduction in decay rate were both compared to the control treatment group.
From the results in table 1, it can be seen that litchi fruits harvested for no more than 24 hours after being sprayed with 1-10 μmol/L sucrose aqueous solution, or litchi fruits harvested within 1-40 days after being sprayed with the sucrose aqueous solution are then packaged in polyethylene plastic film bags and stored at 20-25 ℃, and the browning and the decay of litchi fruits can be remarkably controlled. Compared with the conventional distilled water spraying method for preservation, the preservation method disclosed by the invention has the advantages that the browning index is reduced by 50-90.6% and the rotting rate is reduced by 30-84% after the preservation is carried out for 8 days under the same condition.
FIG. 1 is a graph showing the effect of litchi treatment according to example 1.
Comparative example 1
1. Adding distilled water into sucrose to prepare a sucrose aqueous solution with the concentration of 15 mu mol/L;
2. spraying 15 mu mol/L sucrose water solution on the surface of litchi fruits 12 hours after harvesting, packaging the litchi fruits after spraying with 0.04mm polyethylene plastic film bags, and storing in a storage warehouse at 22.5 ℃.
Comparative example 2
1. Adding distilled water into sucrose to prepare 0.1 mu mol/L sucrose aqueous solution;
2. spraying 0.1 μmol/L sucrose water solution on the surface of fructus litchi 12 hr after harvesting, packaging with 0.04mm polyethylene plastic film bag, and storing in 22.5 deg.C storage.
Comparative example 3
1. Adding distilled water into sucrose to prepare 10 mu mol/L sucrose aqueous solution;
2. spraying 10 μmol/L sucrose water solution on the surface of fructus litchi fruit 30 hr after harvesting, packaging with 0.04mm polyethylene plastic film bag, and storing in 22.5 deg.C storage.
Comparative example 4
1. Adding distilled water into sucrose to prepare 10 mu mol/L sucrose aqueous solution;
2. spraying 10 μmol/L sucrose water solution on the surface of fructus litchi fruit harvested after 45 days, packaging with 0.04mm polyethylene plastic film bag, and storing in 22.5 deg.C storage.
Comparative example 5
1. Adding distilled water into sucrose to prepare a sucrose aqueous solution with the concentration of 20 mu mol/L;
2. spraying 20 mu mol/L sucrose water solution on the surface of litchi fruits 12 hours after harvesting, packaging the litchi fruits after spraying with 0.04mm polyethylene plastic film bags, and storing in a storage at 22.5 ℃.
Comparative example 6
1. Adding distilled water into sucrose to prepare 10 mu mol/L sucrose aqueous solution;
2. spraying 10 mu mol/L sucrose water solution on the surface of litchi fruits 12 hours after harvesting, packaging the litchi fruits after spraying for 6 hours by using 0.04mm polyethylene plastic film bags, removing the polyethylene plastic film bags, airing the litchi fruits, and storing the litchi fruits in a storage warehouse at 22.5 ℃.
Comparative examples 1 to 6 effects
After 8 days of storage, peel browning indexes and rotting rates of litchis sprayed with the sucrose aqueous solution in comparative examples 1-6 were respectively tested, and the control treatment group consisted of spraying litchis with distilled water, packaging with 0.04mm polyethylene plastic film bags, and storing in a 22.5 ℃ storage warehouse. The results are shown in Table 2.
TABLE 2
Note: assessment of the severity of browning of the pericarp reference is made to the method of Scott et al (1982). The browning degree of the litchi peels is classified into 1-5 grades. Level 1: the peel is all red; and 2, stage: the ratio of the browning area to the total area is less than 25 percent; and 3, level: the browning area accounts for 25 to 50 percent; 4, level: the browning area accounts for 50 to 75 percent; and 5, stage: the browning area is greater than 75% to complete browning. The browning index is ∑ (number of browning fruit at each stage × number of browning stages)/total number of investigation fruits;
storing the collected litchi for 8 days; the difference of the surfaces of different letters after the number is extremely obvious (P is less than or equal to 0.01).
The reduction in browning index and the reduction in decay rate were both compared to the control treatment group.
As can be seen from Table 2, compared with the preservation schemes of examples 1-6, 1) too high (comparative example 1) or too low (comparative example 2) sucrose concentration can weaken the effect of controlling browning and decay; 2) when the sucrose concentration is in the optimum range, but the spraying time is too late (comparative example 3) or too early (comparative example 4), the effect of controlling browning and decay is also reduced; 3) when the sucrose concentration was too high (comparative example 5), the effect of controlling browning and decay was not obtained at all; 4) the sucrose concentration and the spraying time are in the optimum range, but the package is removed midway during the storage period, and the browning and the decay are aggravated.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.