阅读说明：本技术 一种即食甜玉米的自发性气体休眠保鲜方法 (Spontaneous gas dormancy preservation method for instant sweet corn ) 是由 肖凯军 程祖鑫 罗青文 吴圆月 朱良 于 2021-01-21 设计创作，主要内容包括：本发明公开了一种即食甜玉米的自发性气体休眠保鲜方法,所述方法如下：将甜玉米进行预处理后,包装获得包装物,对包装物进行等离子体杀菌处理,然后以PP/SPEEK复合膜进行密封包装物,并置于0～4℃低温贮藏。本发明将甜玉米休眠保鲜和低温处理相结合,有效降低甜玉米的呼吸作用,维持甜玉米最低呼吸强度,使甜玉米长期处于休眠状态,减少营养物质消耗,延长甜玉米的保藏期至20天以上,甜玉米依然新鲜、色泽发亮、果粒饱满、营养成分高,感官及口感上佳。本发明所述的即食甜玉米的自发性气体休眠保鲜方法,操作简单且绿色安全。(The invention discloses a spontaneous gas dormancy preservation method of instant sweet corn, which comprises the following steps: the method comprises the steps of pretreating sweet corns, packaging to obtain a package, carrying out plasma sterilization treatment on the package, sealing the package by using a PP/SPEEK composite membrane, and storing at a low temperature of 0-4 ℃. According to the invention, the sweet corn dormancy preservation and low-temperature treatment are combined, so that the respiration of the sweet corn is effectively reduced, the minimum respiration intensity of the sweet corn is maintained, the sweet corn is in a dormant state for a long time, the nutrient consumption is reduced, the storage period of the sweet corn is prolonged to more than 20 days, the sweet corn is still fresh, the color and luster are bright, the fruit grains are full, the nutrient content is high, and the sense and the taste are good. The spontaneous gas dormancy preservation method for the instant sweet corn is simple to operate, green and safe.)

1. A spontaneous air dormancy fresh-keeping method of instant sweet corn is characterized by comprising the following steps:

the method comprises the steps of pretreating sweet corns, packaging to obtain a package, carrying out plasma sterilization treatment on the package, sealing the package by using a PP/SPEEK composite membrane, and storing at a low temperature of 0-4 ℃.

2. The spontaneous air dormancy fresh-keeping method for the instant sweet corn according to claim 1, wherein the PP/SPEEK composite membrane is prepared by coating a solution of ether sulfonated polyether ketone on the surface of a PP membrane and drying.

3. The spontaneous gas dormancy fresh-keeping method for the instant sweet corn according to claim 1, wherein the thickness of the PP/SPEEK composite membrane is 45-55 μm, and the thickness of the SPEEK layer is 25-35 μm.

4. The spontaneous gas dormancy preservation method for the instant sweet corn according to claim 2, wherein the sulfonation degree of the sulfonated polyether ether ketone is 75-80%.

5. The spontaneous gas dormancy fresh-keeping method for the instant sweet corn according to claim 1, characterized in that the plasma sterilization treatment is a plasma gas phase sterilizer placed in a package; the plasma gas phase sterilization treatment conditions are as follows: positive and negativeThe ion concentration is 200 to 500 ten thousand per cm³The time is 5-10 minutes.

6. The spontaneous gas dormancy fresh-keeping method for the instant sweet corn according to claim 1, wherein the relative humidity of the low-temperature storage is 90-95%.

7. The spontaneous gas dormancy fresh-keeping method for the instant sweet corn according to claim 1, characterized in that the packaging material used for packaging is PP or PET packaging box.

8. The spontaneous gas dormancy preservation method for the instant sweet corn according to claim 2, characterized in that the PP/SPEEK composite membrane is prepared by the following steps: dissolving a sulfonated polyether-ether-ketone polymer in a solvent, centrifuging, taking the upper layer solution for defoaming to obtain a SPEEK membrane casting solution, uniformly coating the membrane casting solution on the surface of a PP membrane, and drying at the temperature of 40-45 ℃ to obtain a PP/SPEEK composite membrane; the concentration of the sulfonated polyether ether ketone polymer dissolved in the solvent to form a solution is 10-15 wt%.

9. The spontaneous gas dormancy fresh-keeping method for the instant sweet corn according to claim 1, characterized in that the rotation speed of the centrifugation is 4000-6000 r/min, and the time is 5-10 min; the defoaming treatment adopts an ultrasonic defoaming mode; the drying time is 10-14 h.

10. The method for preserving instant sweet corn by spontaneous gas dormancy as claimed in claim 1, wherein the pretreatment comprises cleaning sweet corn, draining, trimming dead and yellow bracts, trimming tassel, and pre-cooling; the pre-cooling temperature is 0-4 ℃, and the pre-cooling time is 20-24 hours; the relative humidity of the precooling environment is 90-95%.

Technical Field

The invention belongs to the technical field of corn preservation, and particularly relates to a spontaneous gas dormancy preservation method for instant sweet corn.

Background

The sweet corn is native to America and introduced into China later, and is one of the favorite foods of China. It has thin skin, fresh and tender, much juice, sweet taste, rich nutrition, high starch content and good taste, and can be eaten both cooked and raw, so it is also called fruit corn and vegetable corn. The sweet corn is good in appearance, good in quality and excellent in flavor, is rich in soluble sugar, protein, dietary fiber, amino acid, vitamins and other nutrient substances, is easy to absorb by a human body, has a certain cholesterol-reducing effect, has the functions of nutrition and health care, and is popular with consumers.

The phenomena of withered and yellow bracts, shrunken seeds after water loss, fragrance loss and the like of the sweet corn can occur after the sweet corn is harvested, and the commodity value of the sweet corn is greatly reduced. In addition, the nutritional indexes such as moisture, soluble sugar, soluble protein and the like of the sweet corn are reduced in different degrees in the storage process, the respiratory intensity is increased, and the nutrient substances are consumed too fast, so that the use quality and the nutritional value of the corn are directly influenced. Therefore, the research on the sweet corn preservation technology has important significance for the development of the corn industry.

At present, the preservation method of the corn mainly comprises the methods of modified atmosphere preservation, refrigeration preservation and the like. For example, CN 109362877A, sweet corn is placed in liquid nitrogen for 5-10 s, then the sweet corn is frozen and baked at low temperature to obtain baked corn with the water content of 15-20%, then the baked corn is respectively placed in edible acetic acid solution, hydrogen peroxide solution, solution containing tea polyphenol and chitosan and kumquat extract for soaking for a certain time, and finally the baked corn is sterilized and disinfected, and is placed in a freshness protection package filled with a smell isolating and freshness preservation agent for preservation at-20 to-18 ℃. The product preserved by the method is baked corn, the operation is complicated, the original flavor of the sweet corn is damaged by freezing and low-temperature baking, and the edible safety needs to be studied by adopting a chemical preservative. CN 102524384A is prepared by peeling sweet corn, removing stigma, cleaning, placing into PE bag, vacuumizing, placing into outer packaging bag, charging nitrogen gas, sealing after expanding the outer bag, sterilizing the packaged sweet corn in counter-pressure sterilization pot, and taking out and storing at below 25 deg.C. The method can keep the sweet corn fresh at normal temperature for 10-12 months, but the method needs to fill nitrogen gas for high-temperature and high-pressure sterilization, and loses the special flavor of the fresh corn. CN 107873832A firstly carries out pretreatment, peeling and cleaning on sweet corn, the sweet corn is placed into a high-temperature pot with the temperature of 104-107 ℃ for heating for 10-13 s, the sweet corn is cooled after being taken out and sterilized by an ultraviolet lamp, then the sweet corn is dried at a low temperature, then the sweet corn is frozen at the temperature of-14 to-10 ℃, and the sweet corn is dried at the low temperature until the water content is 22-24%. Spraying a protective film agent on the baked sweet corns, baking for 5-6 min at 36-40 ℃, repeating for 3-4 times, wrapping, and finally refrigerating the wrapped sweet corns. Although the method can store the sweet corn for a long time, the moisture content of the sweet corn prepared by the method is greatly reduced, and the flavor and the quality of the sweet corn are not effectively maintained. CN 109892388A is prepared by cleaning sweet corn, draining, spraying antistaling agent on the surface of the outer skin, putting into vacuum bag, vacuum sealing with vacuum device, freezing in refrigerator, and periodically adjusting temperature. The technical method is simple and convenient to operate, but the method adopts vacuum and freezing treatment, so that the sweet corn is easy to freeze and has no oxygen damage.

The method aims at solving the problems that the sweet corn has short preservation period after being picked and serious loss of flavor and nutrient components, and the existing treatment modes such as high-temperature and high-pressure sterilization, freezing preservation, chemical antistaling agent and the like can damage the tissue structure of the sweet corn, so that the flavor is deteriorated, the edible safety is high and the like. The invention adopts a spontaneous gas dormancy fresh-keeping method and combines a plasma sterilization technology to store and keep the sweet corn at a low temperature, so that the sweet corn can reach and maintain the lowest respiratory intensity as soon as possible, the sweet corn is induced to enter a dormant state, the freezing injury and the high-temperature transpiration are avoided, the original flavor and the tissue structure of the sweet corn are kept as much as possible, and the shelf life of the sweet corn is prolonged.

Disclosure of Invention

Aiming at the problems of high water content, strong physiological metabolism and difficult preservation of sweet corn, high cost, complex process and the like of the existing preservation technology, the invention aims to provide a spontaneous gas dormancy preservation method of instant sweet corn.

The purpose of the invention is realized by the following technical scheme:

a spontaneous air dormancy preservation method for instant sweet corn comprises the following steps:

the method comprises the steps of pretreating sweet corns, packaging to obtain a package, carrying out plasma sterilization treatment on the package, sealing the package by using a PP/SPEEK composite membrane, and storing at a low temperature of 0-4 ℃.

Preferably, the pretreatment is to clean and drain the sweet corn, trim the withered and yellow bract, finish the silk and then pre-cool the silk. The pre-cooling temperature is 0-4 ℃, and the pre-cooling time is 20-24 hours. The relative humidity of the precooling environment is 90-95%.

Preferably, the packaging material used for the packaging is a PP or PET packaging box.

Preferably, the plasma sterilization treatment refers to placing a plasma gas phase sterilizer in the package; the positive and negative ion concentration of the plasma gas phase sterilizer is 200-500 ten thousand/cm³(ii) a The plasma sterilization treatment time is 5-10 minutes.

Preferably, the PP (polypropylene)/SPEEK (sulfonated polyether ether ketone) composite membrane has a thickness of 45-55 μm, wherein the SPEEK layer has a thickness of 25-35 μm.

Preferably, the PP (polypropylene)/SPEEK (sulfonated polyether ether ketone) composite membrane is obtained by coating a SPEEK (sulfonated polyether ether ketone) solution on the surface of a PP membrane and drying.

More preferably, the PP (polypropylene)/SPEEK (sulfonated polyether ether ketone) composite membrane is prepared by the following method: dissolving the SPEEK polymer in a solvent, centrifuging, taking the upper layer solution for defoaming to obtain a SPEEK membrane casting solution, uniformly coating the membrane casting solution on the surface of a PP membrane, and drying at the temperature of 40-45 ℃ to obtain the PP/SPEEK composite membrane.

Most preferably, the SPEEK polymer is dissolved in a solvent to form a solution having a concentration of 10 to 15 wt%.

Most preferably, the rotating speed of the centrifugation is 4000-6000 r/min, and the time is 5-10 min.

Most preferably, the defoaming treatment adopts an ultrasonic defoaming mode.

Most preferably, the drying time is 10-14 h.

Most preferably, the SPEEK (sulfonated polyether ether ketone) has a sulfonation degree of 75-80%.

Preferably, the relative humidity of the low-temperature storage is 90-95%.

According to the invention, the sweet corn dormancy preservation and low-temperature treatment are combined, so that the respiration of the sweet corn is effectively reduced, the minimum respiration intensity of the sweet corn is maintained, the sweet corn is in a dormant state for a long time, the consumption of nutrient substances is reduced, and the storage period of the sweet corn is prolonged.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the invention aims at the physiological characteristics of sweet corn and adopts CO₂The PP/SPEEK composite membrane with good permeability spontaneously reduces the oxygen concentration and improves the carbon dioxide concentration, can quickly induce the sweet corn to enter a dormant state, avoids the problems of vigorous high-temperature metabolism, freezing and supercooling damage and the like of the sweet corn, and greatly prolongs the storage period of the sweet corn.

(2) The PP/SPEEK composite membrane sealing low-temperature storage and preservation method of the invention ensures that the sweet corn reaches the lowest respiratory intensity, O, on the 12 th day of storage₂The content is reduced from 20.3 percent to 10.6 percent, and CO is added₂The content is increased from 0.3% to 9.8%, and sweet corn stored in PE film, PP film and SPEEK film sealing mode reaches the lowest respiratory intensity on day 13. The PP/SPEEK composite membrane has a remarkable effect on rapidly inducing sweet corn to enter a resting period, after the sweet corn is stored for 20 days, the mass loss rate of the sweet corn is only 1.70%, and the kernel hardness is increased by 0.264kg/cm²The content of soluble solid matters is reduced by 1.1 percent, the content of water is reduced by 0.82 percent, and the freshness and the edibility of the sweet corn are kept to the utmost extent.

(3) The technology of the invention can prolong the shelf life of the sweet corn to more than 20 days, the sweet corn is still fresh, the fruit grains are mellow and full, the color is bright, the taste and flavor are good, and the microbial spoilage phenomenon does not occur. The common sweet corn preserved by the PE preservative film on the market has wrinkled skin and bad edible flavor after being stored for about 10 days under the same condition.

(4) The method adopts the spontaneous composite air-conditioned membrane and sterilizes the sweet corn through the plasma, so that the method is green and safe, avoids the residue of chemical bactericide and has high edible safety.

(5) The spontaneous gas dormancy fresh-keeping technology for sweet corns, disclosed by the invention, is green, convenient and simple to operate, and is suitable for large-scale production.

Drawings

FIG. 1 is a graph showing the change in respiration rate of sweet corn during storage in example 1 and comparative examples 2 to 4; FIG. 1a corresponds to comparative example 2, FIG. 1b corresponds to comparative example 3, FIG. 1c corresponds to comparative example 4, and FIG. 1d corresponds to example 1.

FIG. 2 shows the results of the change in the mass loss rate of sweet corn obtained in example 1 and comparative examples 1 to 4; a 1-a 5 correspond to comparative examples 1-4 and example 1, respectively.

FIG. 3 shows the results of the kernel hardness changes of the sweet corn obtained in example 1 and comparative examples 1 to 4; a 1-a 5 correspond to comparative examples 1-4 and example 1, respectively.

FIG. 4 is the results of the change in soluble solids content of the sweet corn obtained in example 1 and comparative examples 1-4; a 1-a 5 correspond to comparative examples 1-4 and example 1, respectively.

FIG. 5 shows the results of varying the moisture content of sweet corn obtained in example 1 and comparative examples 1 to 4; a 1-a 5 correspond to comparative examples 1-4 and example 1, respectively.

FIG. 6 shows the results of the sensory and sensory evaluation of sweet corn obtained in example 1 and comparative examples 1 to 4; a 1-a 5 correspond to comparative examples 1-4 and example 1, respectively.

FIG. 7 is an appearance image chart of sweet corn in example 1 and comparative examples 1-4 with preservation time of 0d, 5d, 10d, 15d, 20 d.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

Those who do not specify specific conditions in the examples of the present invention follow conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like which are not indicated for manufacturers are all conventional products which can be obtained by commercial purchase.

The preparation method of the PP/SPEEK composite membrane in the embodiment of the invention comprises the following steps:

accurately weighing a certain amount of SPEEK solid with the sulfonation degree of 77.3%, dissolving the SPEEK solid in an N, N-dimethylformamide solvent at the temperature of 60 ℃, continuously stirring until the SPEEK solid is completely dissolved to obtain a uniform polymer solution with the concentration of 10 wt%, centrifuging the uniform polymer solution for 10min at the speed of 4000r/min, and taking the upper layer solution for ultrasonic defoaming to obtain the homogeneous SPEEK membrane casting solution.

And (2) placing the PP membrane on a glass plate, uniformly coating the SPEEK membrane casting solution on the surface of the PP membrane by using an adjustable scraper, wherein the coating thickness is 30 +/-5 mu m, drying at the temperature of 40 ℃ for 12h, peeling in deionized water, washing with the deionized water for multiple times, and drying in the shade at normal temperature to obtain the PP/SPEEK composite membrane. The thickness of the obtained PP/SPEEK composite film is 48 μm.

Comparative example 1: film-free sealed storage of sweet corn

Modified atmosphere packaging pretreatment: pruning withered and yellow bracts of the sweet corn, finishing silks, washing, draining, and precooling for 24 hours at the temperature of 4 ℃ and the relative humidity of 90%. Selecting 4 precooled sweet corns with similar mass, respectively placing the corns in a PP packaging box to obtain a packaging material, placing a plasma gas phase sterilizer in the packaging material, and sterilizing for 10min, wherein the positive and negative ion concentration of the plasma gas phase sterilizer is 300 ten thousand/cm³。

The blank group was stored at a low temperature, designated a1, without membrane sealing treatment, in an environment at a temperature of 4 ℃ and a relative humidity of 90%. And measuring the quality loss rate, the grain hardness, the soluble solid content and the moisture content of the sweet corn every five days, and tasting the steamed sweet corn to evaluate the sense and the taste of the steamed sweet corn.

After the blank group is stored for 20 days, the mass loss rate of the sweet corn is increased from 0 percent to 36.43 percent, and the kernel hardness is increased from 1.502kg/cm²Rising to 1.963kg/cm²The soluble solid content is reduced from 14.5 percent to 11.6 percent, the moisture content is reduced from 77.58 percent to 74.26 percent, and the sweet corn is dull in color and luster, not full in granules, wrinkled in epidermis and can not be eaten.

Comparative example 2: PE film sealed storage of sweet corn

Performing modified atmosphere packaging pretreatment on sweet corns according to the method of the comparative example 1, selecting 4 sweet corns with similar quality and subjected to pretreatment, respectively placing the sweet corns in a PP packaging box to obtain a package, then performing sterilization treatment, sealing by using a PE film, and preserving at low temperature, wherein the conditions of sterilization and low-temperature preservation are the same as those of the comparative example 1 and are marked as a 2. Measuring the respiratory intensity every day, measuring the quality loss rate, the grain hardness, the soluble solid content and the moisture content every five days, and tasting the steamed sweet corn to evaluate the sense and the taste of the sweet corn.

The sweet corn sealed in PE film reached respiratory equilibrium on day 13, O₂The content is reduced from 20.3 percent to 10.1 percent, and CO is added₂The content is increased from 0.3% to 9.1%. After 20 days of storage, the mass loss rate is increased from 0 percent to 1.89 percent, and the kernel hardness is increased from 1.502kg/cm²Rise to 1.855kg/cm²The soluble solid content is reduced from 14.5% to 13.0%, the water content is reduced from 77.58% to 75.81%, the color is dark, the plumpness is general, the skin is wrinkled, and the edible mouthfeel is poor.

Comparative example 3: PP film sealed storage sweet corn

Performing modified atmosphere packaging pretreatment on sweet corns according to the method of the comparative example 1, selecting 4 sweet corns with similar quality and subjected to pretreatment, respectively placing the sweet corns in a PP packaging box to obtain a package, then performing sterilization treatment, sealing by using a PP film, and preserving at low temperature, wherein the conditions of sterilization and low-temperature preservation are the same as those of the comparative example 1 and are marked as a 3. Measuring the respiratory intensity every day, measuring the quality loss rate, the grain hardness, the soluble solid content and the moisture content every five days, and tasting the steamed sweet corn to evaluate the sense and the taste of the sweet corn.

Sweet corn placed in PP film seal reached respiratory equilibrium, O, on day 13₂The content is reduced from 20.3 percent to 10.2 percent, and CO is₂The content is increased from 0.3% to 10.3%. After 20 days of storage, the mass loss rate is increased from 0 percent to 1.79 percent, and the kernel hardness is increased from 1.502kg/cm²Rising to 1.848kg/cm²The soluble solid content is reduced from 14.5% to 12.9%, the water content is reduced from 77.58% to 75.75%, the color is uniform, the granules are full, the skin is wrinkled, and the taste is common。

Comparative example 4: SPEEK membrane sealed storage sweet corn

Performing modified atmosphere packaging pretreatment on sweet corns according to the method of the comparative example 1, selecting 4 sweet corns with similar quality and subjected to pretreatment, respectively placing the sweet corns in a PP packaging box to obtain a packaging material, then performing sterilization treatment, sealing by using a SPEEK film, and preserving at low temperature, wherein the conditions of sterilization and low-temperature preservation are the same as those of the comparative example 1 and are marked as a 4. Measuring the respiratory intensity every day, measuring the quality loss rate, the grain hardness, the soluble solid content and the moisture content every five days, and tasting the steamed sweet corn to evaluate the sense and the taste of the sweet corn.

Sweet corn placed in a SPEEK membrane seal reached respiratory equilibrium on day 13, O₂The content is reduced from 20.3 percent to 9.0 percent, and CO is added₂The content is increased from 0.3% to 12.6%. After 20 days of storage, the mass loss rate is increased from 0 percent to 1.92 percent, and the kernel hardness is increased from 1.502kg/cm²Rising to 1.852kg/cm²The soluble solid content is reduced from 14.5% to 12.5%, the water content is reduced from 77.58% to 76.52%, the color is dark, the granules are full, the skin is wrinkled, and the taste is poor.

Example 1: PP/SPEEK composite membrane sealed storage sweet corn

Performing modified atmosphere packaging pretreatment on sweet corns according to the method of the comparative example 1, selecting 4 sweet corns with similar quality and subjected to pretreatment, respectively placing the sweet corns in a PP packaging box to obtain a packaging material, then performing sterilization treatment, sealing by using a PP/SPEEK composite membrane, and preserving at low temperature, wherein the sterilization and low temperature preservation conditions are the same as those of the comparative example 1 and are marked as a5, measuring the respiratory intensity every day, measuring the quality loss rate, the grain hardness, the soluble solid content and the water content every five days, tasting the sweet corns after being steamed, and evaluating the sense and the taste of the sweet corns.

The sweet corn sealed by the PP/SPEEK composite membrane reaches the respiratory balance on day 12, and O₂The content is reduced from 20.3 percent to 10.6 percent, and CO is added₂The content is increased from 0.3% to 9.8%. After 20 days of storage, the mass loss rate is increased from 0 percent to 1.70 percent, and the kernel hardness is increased from 1.502kg/cm²Rises to 1.766kg/cm²The soluble solid content is reduced from 14.5% to 13.4%, the water content is reduced from 77.58% to 76.76%, the color is uniform, the granules are full, the skin is micro-wrinkled, and the taste is good.

The freshness-retaining effect test of example 1 and comparative examples 1 to 4 is shown in FIGS. 1 to 6.

FIG. 1 is a graph showing the change in respiration rate of sweet corn during storage in example 1 and comparative examples 2 to 4; FIG. 1(a)/(b)/(c)/(d) corresponds to comparative examples 2 to 4 and example 1, respectively; FIG. 2 shows the results of the change in the mass loss rate of sweet corn obtained in example 1 and comparative examples 1 to 4; FIG. 3 shows the results of the kernel hardness changes of the sweet corn obtained in example 1 and comparative examples 1 to 4; FIG. 4 is the results of the change in soluble solids content of the sweet corn obtained in example 1 and comparative examples 1-4; FIG. 5 shows the results of varying the moisture content of sweet corn obtained in example 1 and comparative examples 1 to 4; FIG. 6 shows the results of the sensory and sensory evaluation of sweet corn obtained in example 1 and comparative examples 1 to 4; in FIGS. 2 to 6, a1 to a5 correspond to comparative examples 1 to 4 and example 1, respectively. FIG. 7 is an appearance image chart of sweet corn in example 1 and comparative examples 1-4 with preservation time of 0d, 5d, 10d, 15d, 20 d.

The results of the embodiment 1 and the comparative examples 1-4 show that the PP/SPEEK composite membrane can spontaneously adjust the concentration of oxygen and carbon dioxide in a packaging box to a certain extent, shorten the time for the sweet corn to reach the respiratory equilibrium and enable the sweet corn to enter the dormant state as soon as possible. The PP/SPEEK composite membrane is adopted to seal and package the sweet corn at low temperature, so that the loss of the quality, the content of soluble solid and the water content of the sweet corn can be effectively reduced, and the hardness, the flavor and the mouthfeel of the sweet corn grains are kept. The sweet corns are stored for 12 days and then enter a dormant state, the oxygen content is 10.6 percent, the carbon dioxide content is 9.8 percent, and the sweet corns stored in other membrane sealing modes in the comparative example enter the dormant state on the 13 th day of preservation. Example 1 after 20 days of storage, the mass loss rate of sweet corn was 1.70%, and the kernel hardness was increased by 0.264kg/cm²The content of soluble solid matters is reduced by 1.1 percent, and the content of water is reduced by 0.82 percent, which shows that the freshness of the sweet corn can be effectively maintained and the quality guarantee period of the sweet corn can be prolonged by the PP/SPEEK composite membrane which is stored at low temperature in a sealing way. The common PE air-conditioning film is sealed and kept fresh at low temperature,the sweet corn is dark in color and has wrinkled epidermis after about 10 days, and the preservation method of the invention is prolonged to 20 days, so that the sweet corn still has uniform color and plump grains, and the eating taste is good.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.