阅读说明：本技术 一种蓝莓鲜果的保鲜方法 (Preservation method of fresh blueberry fruits ) 是由 郑亚琴 徐蒙 于军香 于 2021-09-23 设计创作，主要内容包括：本发明公开一种蓝莓鲜果的保鲜方法,属于农产品贮藏保鲜技术领域。本发明保鲜方法包括选果、涂膜、采摘、辐照杀菌、打包贮藏5个环节。本发明使用山竹皮提取物和苹果多酚作为复合天然保鲜剂,成分健康安全无残留；本发明将有效物质山竹皮提取物和苹果多酚使用多孔淀粉颗粒有效包裹,实现有效成分的持续稳定释放,减少有效成分的挥发,大大延长天然保鲜剂的作用时间；本发明还辅以低剂量的辐照杀菌,可以有效杀死依附在蓝莓果实表面的细菌等微生物,进一步起到保鲜防腐的效果；本发明保鲜剂蓝莓贮藏80d,腐烂率低于15％,可实现长久高效的保鲜。(The invention discloses a preservation method of fresh blueberry fruits, and belongs to the technical field of storage and preservation of agricultural products. The fresh-keeping method of the invention comprises 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging and storage. The mangosteen bark extract and the apple polyphenol are used as the compound natural preservative, so that the components are healthy, safe and residue-free; according to the invention, the active substances of the mangosteen bark extract and the apple polyphenol are effectively wrapped by the porous starch granules, so that the continuous and stable release of the active ingredients is realized, the volatilization of the active ingredients is reduced, and the action time of the natural preservative is greatly prolonged; the blueberry fruit preservative also assists in low-dose irradiation sterilization, so that microorganisms such as bacteria attached to the surfaces of blueberry fruits can be effectively killed, and the effects of preservation and corrosion prevention are further achieved; the blueberry preservative disclosed by the invention is stored for 80 days, the rotting rate is lower than 15%, and long-term and efficient preservation can be realized.)

1. A fresh-keeping method of blueberry fresh fruits is characterized by comprising 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging and storage.

2. The fresh-keeping method for the fresh blueberries according to claim 1, wherein the fruit selection is to select the fruits of disease-free blueberry plants, and the fruits are healthy blueberries with the ripeness of 8-9.

3. The fresh-keeping method of the fresh blueberry fruits as claimed in claim 1, wherein the method of the coating step is as follows:

(1) preparing coating liquid: adding starch into sodium hydroxide solution, heating and stirring to obtain transparent paste, and cooling to room temperature to obtain

To starch paste; sequentially adding apple polyphenol 0.5 wt% of starch paste and cortex Garciniae 0.5 wt% of starch paste, and extracting

Adding oleum Olivarum 20% by weight of starch paste, Tween 80 1% by weight of starch paste and sodium trimetaphosphate 0.1-0.5% by weight of starch paste, stirring at high speed or homogenizing for 30-60 min, centrifuging, washing with anhydrous ethanol

Washing for 1-2 times to obtain solid particles;

(2) uniformly dispersing solid particles in water to form a suspension with the mass fraction of 5%, and homogenizing the suspension by a sprayer

Uniformly spraying the mixture on the surfaces of the blueberries.

4. The fresh-keeping method of fresh blueberry fruits as claimed in claim 3, wherein the preparation method of the mangosteen bark extract in the step (1) is as follows: drying, crushing and grinding fresh mangosteen pericarp, weighing 10g of dried mangosteen pericarp powder, placing in a container, adding 50mL of ethanol with the volume fraction of 70%, refluxing in water bath for 2h, filtering and centrifuging, taking supernatant, performing rotary evaporation at 40 ℃, then diluting to a constant volume of 10mL with 70% ethanol, taking 5mL, diluting to 50mL with distilled water, and preparing the mangosteen pericarp extract.

5. The fresh-keeping method for the fresh blueberries according to claim 1, wherein in the picking step, after the coating is finished, the blueberries are picked after being naturally dried in the sun.

6. The fresh-keeping method of fresh blueberry fruits according to claim 1, wherein the irradiation sterilization is performed by irradiating the picked blueberry fruits with gamma rays, and the irradiation dose is 0.1-0.5 kGy.

7. The fresh blueberry fruit preservation method according to claim 1, wherein the packing and storage are implemented by putting the irradiated blueberry fruits into a preservation box, wrapping the blueberry fruits by using a preservative film, and immediately bagging the blueberry fruits for long-term storage after fully precooling the blueberry fruits.

8. The fresh-keeping method for the fresh blueberries according to claim 7, wherein the precooling conditions are 0-5 ℃ and 0.5-1 h;

the temperature for long-term storage is 1-3 deg.C.

Technical Field

The invention belongs to the technical field of storage and preservation of agricultural products, and particularly relates to a preservation method of fresh blueberry fruits.

Background

Blueberry, also known as dragon fruit, kokui etc., is shrub or shrub of Vaccinium of Ericaceae, its fruit is fresh and tender, the mouthfeel is unique, nutritious, the active material contained is mainly polyphenols, its functional component mainly contains anthocyanin, phenolic acid, ursolic acid, superoxide dismutase, pectic substance, vitamin and some mineral substances. Has good health-care effect on human body, and mainly has the effects of resisting oxidation, enhancing immunity, protecting cardiovascular and cerebrovascular vessels, reducing blood fat, relieving visual fatigue and the like.

However, in summer when the blueberry fruits are ripe at high temperature and raininess, the problems of dehydration, decay, pulp softening, quality deterioration and the like are easy to occur after the blueberry fruits are picked, so that the storage, preservation and deep processing of the blueberries after the blueberry fruits are picked are particularly important.

The method for blueberry preservation mainly comprises the methods of low temperature, air conditioning, coating, UV radiation and the like, and the method is widely applied to low temperature air conditioning and high oxygen technology. However, the method has the defects of high cost, incapability of ensuring safety and health, poor fresh-keeping quality and the like, is limited in storage of fresh blueberries and is difficult to effectively regulate and control.

In addition, a common method is an irradiation method, which is to utilize the radiation energy of rays to perform sterilization, disinsection, disinfection, mildew prevention and other processing treatments on food or raw materials, reduce the number of spoilage microorganisms and other organisms in the food, and prolong the post-maturation period and storage period of fresh food. Improper irradiation can cause damage to the material itself, and the damage is more serious with larger doses.

Therefore, at present, the blueberry storage and preservation technology mainly adopts a mode of combining physical preservation with chemical preservation, and the chemical preservative and the bactericide can effectively maintain the quality of the picked blueberries and reduce the disease incidence, but reagent residues are easy to cause and influence the health of human bodies. Due to the problem of food safety, the use of chemical preservatives and bactericides is increasingly limited, new food preservation technologies are researched, and green, environment-friendly and non-toxic preservation methods are developed to prolong the storage period of blueberries.

The natural plant preservative has the advantages of high safety, good sterilization effect, simple operation and the like, and is deeply concerned by researchers in recent years. The clove essential oil coated paper box can prolong the shelf life of the juicy peaches and has good mould inhibition effect on peach fruits. The chitosan coating treatment can obviously improve the quality of fresh Jinzao fruits and keep the good fruit rate of the Jinzao fruits. Although reports about the preservation of blueberries also exist, the natural compound preservative is concentrated on the soaking treatment after the blueberry is picked. If the fruit airing effect after soaking treatment is not good, the storage quality of the large-scale blueberry preservation is difficult to guarantee.

How to realize the green, efficient, healthy and quick preservation of blueberry fruits, the storage time of blueberries is prolonged to the maximum extent on the premise of ensuring the quality of the blueberries, and the method is an important way for realizing the economic value of the blueberries.

Disclosure of Invention

Aiming at the defects of the existing blueberry preservation technology, the invention provides a green and efficient blueberry preservation and storage method, which can effectively prolong the storage time of blueberries and keep the color, the fragrance and the taste of the blueberries, particularly the stability of nutrient substances.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:

a fresh-keeping method for blueberry fruits comprises 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging storage.

Further, in the fruit selection link, disease-free blueberry plants are screened, and healthy blueberry fruits with fruits of 8-9 are ripe.

Further, the method of the coating step comprises the following steps:

(1) preparing coating liquid: adding starch into sodium hydroxide solution, heating and stirring to obtain transparent paste, and cooling to room temperature to obtain starch paste; sequentially adding apple polyphenol accounting for 0.5 percent of the mass of the starch paste, mangosteen bark extract accounting for 0.5 percent of the mass of the starch paste, olive oil accounting for 20 percent of the mass of the starch paste, tween 80 accounting for 1 percent of the mass of the starch paste and sodium trimetaphosphate accounting for 0.1 to 0.5 percent of the mass of the starch paste, stirring at a high speed or homogenizing for 30 to 60 minutes, performing centrifugal separation, and washing for 1 to 2 times by using absolute ethyl alcohol to obtain solid particles;

(2) and uniformly dispersing the solid particles in water to form a suspension with the mass fraction of 5%, and uniformly spraying the suspension on the surface of the blueberry fruit through a sprayer.

Further, the mass ratio of the starch to the sodium hydroxide solution in the step (1) is 1:20, and the mass concentration of the sodium hydroxide solution is 5%. The heating and stirring temperature is 40-45 ℃.

Further, the preparation method of the mangosteen bark extract in the step (1) comprises the following steps: drying and crushing fresh mangosteen pericarp, weighing 10g of dried mangosteen pericarp powder, placing in a container, adding 50mL of ethanol with the volume fraction of 70%, refluxing in water bath for 2h, filtering and centrifuging, taking supernatant, performing rotary evaporation at 40 ℃, then diluting to a constant volume of 10mL with ethanol with the volume fraction of 70%, taking 5mL, diluting to 50mL with distilled water, and preparing into the mangosteen pericarp extract.

Further, in the picking link, after the film coating is finished, the blueberries are picked after being naturally dried in the sun. When in collection, the user wears clean soft gloves or finger sleeves. The fruit powder is picked and placed lightly to avoid mechanical damages such as fruit base tearing, collision, pressing, grinding and the like, and the integrity of the fruit powder is kept as much as possible.

The picking container is required to be suitable in size, smooth in inner surface or soft in liner, damaged fruits, soft fruits, malformed fruits, immature fruits and insect-resistant fruits are removed at any time during picking.

Furthermore, the radiation sterilization is to irradiate the picked blueberry fruits by gamma rays, and the irradiation dose is 0.1-0.5 kGy.

Further, the packing and storage are that the blueberry fruits after irradiation are put into a preservation box, wrapped by a preservative film, and immediately packed for long-term storage after being fully precooled.

Further, the precooling condition is 0-5 ℃, and 0.5-1 h; the temperature for long-term storage is 1-3 deg.C.

The apple polyphenol is purchased from Shaanxi Yimin plant science and technology limited company, the polyphenol content is 50 percent, and other raw materials are commercially available.

The mangosteen flesh is juicy and fresh and sweet, is rich in nutrient substances such as cellulose, fat, protein and the like, and has the reputation of queen in fruit. The mangosteen skin accounts for 52 to 68 percent of the fresh weight of the mangosteen fruits, is rich in natural active substances such as total phenols, flavonoid compounds and the like, and has better functions of oxidation resistance, aging resistance, bacteria resistance and the like. The mangosteen skin is used for preparing the preservative, so that waste utilization is realized, and meanwhile, the natural antibacterial and antioxidant substances are safe and green and can replace chemical preservatives.

Apple polyphenol is similar to common chitosan, belongs to a natural preservative, and has the advantages of edible quality, low price and easy obtainment. The apple polyphenol is a secondary metabolite widely existing in apples, and has strong oxidation resistance and good antibacterial and color protection capabilities. The apple polyphenol has better bacteriostatic effect than that of the lactic acid streptococcus, and has stronger bacteriostatic action.

According to the invention, the mangosteen skin bioactive substances are efficiently extracted to replace a chemical preservative, and apple polyphenol is added, so that the efficient preservation of the blueberries is realized under the synergistic effect of the mangosteen skin bioactive substances and the apple polyphenol, the components are green and healthy, the nutrition and the flavor of the blueberries are maintained for a long time, and the use of the chemical preservative is completely replaced.

Advantageous effects

(1) The mangosteen bark extract and the apple polyphenol are used as the compound natural preservative, so that the components are healthy, safe and residue-free;

(2) according to the invention, the active substances of the mangosteen bark extract and the apple polyphenol are effectively wrapped by the porous starch granules, so that the continuous and stable release of the active ingredients is realized, the volatilization of the active ingredients is reduced, and the action time of the natural preservative is greatly prolonged;

(3) the blueberry fruit preservative also assists in low-dose irradiation sterilization, so that microorganisms such as bacteria attached to the surfaces of blueberry fruits can be effectively killed, and the effects of preservation and corrosion prevention are further achieved;

(4) the blueberry preservative disclosed by the invention is stored for 80 days, the rotting rate is lower than 15%, and long-term and efficient preservation can be realized.

Drawings

FIG. 1 is a graph showing the relationship between the decay rate and hardness index of blueberries and the mass concentration of suspension;

fig. 2 is a chart of blueberry preservation effect.

Detailed Description

The technical solution of the present invention is further described below with reference to specific embodiments, but is not limited thereto.

Example 1

A fresh-keeping method for blueberry fruits comprises 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging storage.

In the fruit selection step, disease-free blueberry plants are screened, and healthy blueberry fruits with fruits of 8-9 are ripe.

The method of the coating step comprises the following steps:

(1) preparing coating liquid: adding starch into sodium hydroxide solution, heating and stirring to obtain transparent paste, and cooling to room temperature to obtain starch paste; sequentially adding apple polyphenol accounting for 0.5 percent of the mass of the starch paste, mangosteen bark extract accounting for 0.5 percent of the mass of the starch paste, olive oil accounting for 20 percent of the mass of the starch paste, tween 80 accounting for 1 percent of the mass of the starch paste and sodium trimetaphosphate accounting for 0.1 percent of the mass of the starch paste, stirring at a high speed or homogenizing for 30min, performing centrifugal separation, and washing for 1-2 times by using absolute ethyl alcohol to obtain solid particles;

(2) and uniformly dispersing the solid particles in water to form a suspension with the mass fraction of 5%, and uniformly spraying the suspension on the surface of the blueberry fruit through a sprayer.

The mass ratio of the starch to the sodium hydroxide solution in the step (1) is 1:20, and the mass concentration of the sodium hydroxide solution is 5%. The heating and stirring temperature is 40-45 ℃.

The preparation method of the mangosteen bark extract in the step (1) comprises the following steps: drying and crushing fresh mangosteen pericarp, weighing 10g of dried mangosteen pericarp powder, placing in a container, adding 50mL of ethanol with the volume fraction of 70%, refluxing in water bath for 2h, filtering and centrifuging, taking supernatant, performing rotary evaporation at 40 ℃, then diluting to a constant volume of 10mL with ethanol with the volume fraction of 70%, taking 5mL, diluting to 50mL with distilled water, and preparing into the mangosteen pericarp extract.

In the picking step, after the film coating is finished, the blueberries are picked after being naturally dried in the sun.

The irradiation sterilization is to irradiate the picked blueberry fruits by gamma rays, and the irradiation dose is 0.1 kGy.

The packing storage is to pack the irradiated blueberry fruits into a preservation box, wrap the blueberry fruits by using a preservative film, and immediately tie bags for long-term storage after full precooling.

The precooling condition is 3 ℃ and 0.5 h; the temperature for long-term storage was 3 ℃.

Example 2

A fresh-keeping method for blueberry fruits comprises 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging storage.

In the fruit selection step, disease-free blueberry plants are screened, and healthy blueberry fruits with fruits of 8-9 are ripe.

The method of the coating step comprises the following steps:

(1) preparing coating liquid: adding starch into sodium hydroxide solution, heating and stirring to obtain transparent paste, and cooling to room temperature to obtain starch paste; sequentially adding apple polyphenol accounting for 0.5 percent of the mass of the starch paste, mangosteen bark extract accounting for 0.5 percent of the mass of the starch paste, olive oil accounting for 20 percent of the mass of the starch paste, tween 80 accounting for 1 percent of the mass of the starch paste and sodium trimetaphosphate accounting for 0.5 percent of the mass of the starch paste, stirring at a high speed or homogenizing for 60min, performing centrifugal separation, and washing for 1-2 times by using absolute ethyl alcohol to obtain solid particles;

(2) and uniformly dispersing the solid particles in water to form a suspension with the mass fraction of 5%, and uniformly spraying the suspension on the surface of the blueberry fruit through a sprayer.

The mass ratio of the starch to the sodium hydroxide solution in the step (1) is 1:20, and the mass concentration of the sodium hydroxide solution is 5%. The heating and stirring temperature is 40-45 ℃.

The preparation method of the mangosteen bark extract in the step (1) comprises the following steps: drying and crushing fresh mangosteen pericarp, weighing 10g of dried mangosteen pericarp powder, placing in a container, adding 50mL of ethanol with the volume fraction of 70%, refluxing in water bath for 2h, filtering and centrifuging, taking supernatant, performing rotary evaporation at 40 ℃, then diluting to a constant volume of 10mL with ethanol with the volume fraction of 70%, taking 5mL, diluting to 50mL with distilled water, and preparing into the mangosteen pericarp extract.

In the picking step, after the film coating is finished, the blueberries are picked after being naturally dried in the sun.

The irradiation sterilization is to irradiate the picked blueberry fruits by gamma rays, and the irradiation dose is 0.5 kGy.

The packing storage is to pack the irradiated blueberry fruits into a preservation box, wrap the blueberry fruits by using a preservative film, and immediately tie bags for long-term storage after full precooling.

The precooling condition is 0 ℃ and 1 h; the temperature for long-term storage was 3 ℃.

Example 3

A fresh-keeping method for blueberry fruits comprises 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging storage.

In the fruit selection step, disease-free blueberry plants are screened, and healthy blueberry fruits with fruits of 8-9 are ripe.

The method of the coating step comprises the following steps:

(1) preparing coating liquid: adding starch into sodium hydroxide solution, heating and stirring to obtain transparent paste, and cooling to room temperature to obtain starch paste; sequentially adding apple polyphenol accounting for 0.5 percent of the mass of the starch paste, mangosteen bark extract accounting for 0.5 percent of the mass of the starch paste, olive oil accounting for 20 percent of the mass of the starch paste, tween 80 accounting for 1 percent of the mass of the starch paste and sodium trimetaphosphate accounting for 0.5 percent of the mass of the starch paste, stirring at a high speed or homogenizing for 60min, performing centrifugal separation, and washing for 1-2 times by using absolute ethyl alcohol to obtain solid particles;

(2) and uniformly dispersing the solid particles in water to form a suspension with the mass fraction of 5%, and uniformly spraying the suspension on the surface of the blueberry fruit through a sprayer.

The mass ratio of the starch to the sodium hydroxide solution in the step (1) is 1:20, and the mass concentration of the sodium hydroxide solution is 5%. The heating and stirring temperature is 40-45 ℃.

The preparation method of the mangosteen bark extract in the step (1) comprises the following steps: drying and crushing fresh mangosteen pericarp, weighing 10g of dried mangosteen pericarp powder, placing in a container, adding 50mL of ethanol with the volume fraction of 70%, refluxing in water bath for 2h, filtering and centrifuging, taking supernatant, performing rotary evaporation at 40 ℃, then diluting to a constant volume of 10mL with ethanol with the volume fraction of 70%, taking 5mL, diluting to 50mL with distilled water, and preparing into the mangosteen pericarp extract.

In the picking step, after the film coating is finished, the blueberries are picked after being naturally dried in the sun.

The irradiation sterilization is to irradiate the picked blueberry fruits by gamma rays, and the irradiation dose is 0.5 kGy.

The packing storage is to pack the irradiated blueberry fruits into a preservation box, wrap the blueberry fruits by using a preservative film, and immediately tie bags for long-term storage after full precooling.

The precooling condition is 0 ℃ and 1 h; the temperature for long-term storage was 1 ℃.

The solid particles are uniformly dispersed in water to form a suspension with the mass fraction of about 5% for coating, so that the concentration is effective and economic, the fresh-keeping effect can be effectively exerted by about 5% of the addition amount, the fresh-keeping effect can be reduced by excessive addition amount, and the cost can be increased.

Based on the embodiment, the mass fraction of solid particles dispersed in water, namely the mass concentration of the suspension is changed, and the index of the blueberry preserved for 80 days is measured according to the performance test part, as shown in fig. 1, the rotting rate gradually decreases along with the increase of the content, and tends to be stable after 5-6%, the hardness of the fruit gradually increases along with the increase of the content, and increases to a certain degree or has a tendency of slow decrease, because the starch particles are excessive, the oxidation of the surface of the fruit is accelerated, the preservation is not facilitated, and meanwhile, the cost is increased due to excessive addition of the preservative, and because of comprehensive consideration, the addition of 5-6% is the most suitable addition.

Comparative example 1

A fresh-keeping method for blueberry fruits comprises 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging storage.

In the fruit selection step, disease-free blueberry plants are screened, and healthy blueberry fruits with fruits of 8-9 are ripe.

The method of the coating step comprises the following steps:

(1) preparing coating liquid: adding starch into sodium hydroxide solution, heating and stirring to obtain transparent paste, and cooling to room temperature to obtain starch paste; sequentially adding cortex Garciniae extract 0.5% of the mass of starch paste, adding oleum Olivarum 20% of the mass of starch paste, Tween 80 1% of the mass of starch paste and sodium trimetaphosphate 0.5% of the mass of starch paste, stirring at high speed or homogenizing for 60min, centrifuging, and washing with anhydrous ethanol for 1-2 times to obtain solid particles;

(2) and uniformly dispersing the solid particles in water to form a suspension with the mass fraction of 5%, and uniformly spraying the suspension on the surface of the blueberry fruit through a sprayer.

The mass ratio of the starch to the sodium hydroxide solution in the step (1) is 1:20, and the mass concentration of the sodium hydroxide solution is 5%. The heating and stirring temperature is 40-45 ℃.

The preparation method of the mangosteen bark extract in the step (1) comprises the following steps: drying and crushing fresh mangosteen pericarp, weighing 10g of dried mangosteen pericarp powder, placing in a container, adding 50mL of ethanol with the volume fraction of 70%, refluxing in water bath for 2h, filtering and centrifuging, taking supernatant, performing rotary evaporation at 40 ℃, then diluting to a constant volume of 10mL with ethanol with the volume fraction of 70%, taking 5mL, diluting to 50mL with distilled water, and preparing into the mangosteen pericarp extract.

In the picking step, after the film coating is finished, the blueberries are picked after being naturally dried in the sun.

The irradiation sterilization is to irradiate the picked blueberry fruits by gamma rays, and the irradiation dose is 0.5 kGy.

The packing storage is to pack the irradiated blueberry fruits into a preservation box, wrap the blueberry fruits by using a preservative film, and immediately tie bags for long-term storage after full precooling.

The precooling condition is 0 ℃ and 1 h; the temperature for long-term storage was 1 ℃.

This comparative example is the same as example 3 except that apple polyphenol is not added.

Comparative example 2

A fresh-keeping method for blueberry fruits comprises 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging storage.

In the fruit selection step, disease-free blueberry plants are screened, and healthy blueberry fruits with fruits of 8-9 are ripe.

The method of the coating step comprises the following steps:

(3) preparing coating liquid: adding starch into sodium hydroxide solution, heating and stirring to obtain transparent paste, and cooling to room temperature to obtain starch paste; sequentially adding apple polyphenol accounting for 0.5 percent of the mass of the starch paste, adding olive oil accounting for 20 percent of the mass of the starch paste, tween 80 accounting for 1 percent of the mass of the starch paste and sodium trimetaphosphate accounting for 0.5 percent of the mass of the starch paste, stirring at a high speed or homogenizing for 60min, performing centrifugal separation, and washing for 1-2 times by using absolute ethyl alcohol to obtain solid particles;

(4) and uniformly dispersing the solid particles in water to form a suspension with the mass fraction of 5%, and uniformly spraying the suspension on the surface of the blueberry fruit through a sprayer.

The mass ratio of the starch to the sodium hydroxide solution in the step (1) is 1:20, and the mass concentration of the sodium hydroxide solution is 5%. The heating and stirring temperature is 40-45 ℃.

In the picking step, after the film coating is finished, the blueberries are picked after being naturally dried in the sun.

The irradiation sterilization is to irradiate the picked blueberry fruits by gamma rays, and the irradiation dose is 0.5 kGy.

The packing storage is to pack the irradiated blueberry fruits into a preservation box, wrap the blueberry fruits by using a preservative film, and immediately tie bags for long-term storage after full precooling.

The precooling condition is 0 ℃ and 1 h; the temperature for long-term storage was 1 ℃.

This comparative example is the same as example 3 except that no extract of mangosteen bark is added.

Comparative example 3

A fresh-keeping method for blueberry fruits comprises 5 links of fruit selection, film coating, picking, irradiation sterilization and packaging storage.

In the fruit selection step, disease-free blueberry plants are screened, and healthy blueberry fruits with fruits of 8-9 are ripe.

The method of the coating step comprises the following steps:

(3) preparing coating liquid: adding starch into sodium hydroxide solution, heating and stirring to obtain transparent paste, and cooling to room temperature to obtain starch paste; sequentially adding oleum Olivarum 20% by mass of starch paste, Tween 80 1% by mass of starch paste and sodium trimetaphosphate 0.5% by mass of starch paste, stirring at high speed or homogenizing for 60min, centrifuging, and washing with anhydrous ethanol for 1-2 times to obtain solid particles;

(4) and uniformly dispersing the solid particles in water to form a suspension with the mass fraction of 5%, and uniformly spraying the suspension on the surface of the blueberry fruit through a sprayer.

The mass ratio of the starch to the sodium hydroxide solution in the step (1) is 1:20, and the mass concentration of the sodium hydroxide solution is 5%. The heating and stirring temperature is 40-45 ℃.

In the picking step, after the film coating is finished, the blueberries are picked after being naturally dried in the sun.

The irradiation sterilization is to irradiate the picked blueberry fruits by gamma rays, and the irradiation dose is 0.5 kGy.

The packing storage is to pack the irradiated blueberry fruits into a preservation box, wrap the blueberry fruits by using a preservative film, and immediately tie bags for long-term storage after full precooling.

The precooling condition is 0 ℃ and 1 h; the temperature for long-term storage was 1 ℃.

The comparative example does not add apple polyphenol nor mangosteen bark extract, and the rest raw materials and processes are the same as example 3.

Testing and testing

Blueberry preservation tests are carried out by the methods of examples 1-3 and comparative examples 1-3 of the invention, and indexes such as fruit rot rate, hardness, nutrient content and the like are tested.

The test varieties are as follows: blueberry (Pink blue)

Test site: linyi university agricultural teaching demonstration garden

The test method comprises the following steps:

the blueberry is preserved according to the method of the embodiment 1, the blueberry is stored at 125 g/box, the storage temperature is 3 ℃, and the relative humidity is 85-95%;

keeping the blueberry fresh according to the method of the embodiment 2, wherein the blueberry is stored at 125 g/box, the storage temperature is 3 ℃, and the relative humidity is 85-95%;

keeping the blueberry fresh according to the method in the embodiment 3, wherein the blueberry is stored at 125 g/box, the storage temperature is 1 ℃, and the relative humidity is 85-95%;

the blueberry is preserved according to the method of comparative example 1, the blueberry is stored at a temperature of 1 ℃ and a relative humidity of 85-95 percent in 125 g/box;

keeping the blueberry fresh according to the method of comparative example 2, wherein the blueberry is stored at a temperature of 1 ℃ and a relative humidity of 85-95% in a box of 125 g;

keeping the blueberry fresh according to the method of comparative example 3, wherein the blueberry is stored at a temperature of 1 ℃ and a relative humidity of 85-95% in a box of 125 g;

test index

Measuring each index every 20 days, repeating each treatment for 3 times, and averaging

1. Determination of decay Rate

Measuring the blueberries by adopting a counting method, and calculating a formula: rotting rate is equal to rotten fruit number/investigation total fruit number multiplied by 100%

2. Hardness of

And (4) measuring by using a texture analyzer. Selecting a P/50 type probe with the diameter of 50mm, and testing at the speed of 1 mm/s; the compression deformation was 30%, the peak height of the first peak was the maximum force, which was the measured hardness value in g.

3. Soluble solid

Measured by an automatic potentiometric titrator

4. Vitamin C

Determination by molybdenum blue colorimetry

5. Anthocyanins

6. Measured by pH differential method

The test results are shown in Table 1

TABLE 1 measurement results of Properties

As can be seen from the data in Table 1, the blueberry fruits obtained by the preservation method of the embodiments 1-3 of the invention have the lowest rotting rate of 11.9 percent in 80 days, higher levels of hardness, soluble solid solution, vitamin C and anthocyanin content and slower reduction speed. The comparative examples 1 to 3 which change the components of the preservative show higher rotting rate and the indexes of various nutrient substances show the tendency of accelerated decline. The addition of the two natural preservatives ensures the high-efficiency preservation effect, and the two natural preservatives have synergistic effect, so that the chemical preservatives can be replaced. FIG. 2 shows the storage effect of blueberries, compared examples 1-3 show a large amount of dark and red fruits after being stored for 80 days, the reduction of frost is obvious, and example 3 still keeps high freshness and the frost is obvious.

It should be noted that the above-mentioned embodiments are only some of the preferred modes for implementing the invention, and not all of them. Obviously, all other embodiments obtained by persons of ordinary skill in the art based on the above-mentioned embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.