阅读说明：本技术 一种高温季节采收叶菜的真空预冷保鲜技术 (Vacuum precooling preservation technology for harvesting leaf vegetables in high-temperature season ) 是由 李鹏霞 安容慧 李国锋 周宏胜 于 2021-02-05 设计创作，主要内容包括：本发明提供了一种高温季节采收叶菜的真空预冷保鲜技术,在真空预冷设备的预冷室添加雾化设备和自动补气阀；将从田间采收的叶菜立即装筐置于预冷室,预冷过程分为降压,保压和复压三部分,保压过程开启配有保鲜液的雾化系统,复压时通入含有氦气和氢气的混合气；当真空室内压强恢复到1标准大气压,取出叶菜进行装筐入库低温贮藏或直接运输上市销售。本发明简便易行,高效,安全,通过在预冷保压环节对叶菜进行保鲜液的雾化,解决了在预冷降压过程中叶菜失水的问题,起到了杀菌延缓衰老的作用；使用氦气和氢气的混合气复压,降低了压力对叶菜的损伤,同时提高了组织的抗氧化能力,延长了叶菜的贮藏期,对高温季节叶菜的采后保鲜具有重要意义。(The invention provides a vacuum precooling and fresh-keeping technology for harvesting leafy vegetables in high-temperature seasons, wherein atomization equipment and an automatic air supply valve are added in a precooling chamber of vacuum precooling equipment; immediately loading the leaf vegetables collected from the field into a basket and placing the basket in a pre-cooling chamber, wherein the pre-cooling process comprises three parts of pressure reduction, pressure maintaining and re-pressure, an atomization system provided with a fresh-keeping liquid is started in the pressure maintaining process, and a mixed gas containing helium and hydrogen is introduced in the re-pressure process; when the pressure in the vacuum chamber is restored to 1 standard atmospheric pressure, the leaf vegetables are taken out to be subjected to basket loading and storage at low temperature or directly transported to market for sale. The method is simple, convenient and easy to implement, efficient and safe, and can be used for atomizing the preservation solution for the leaf vegetables in the precooling and pressure maintaining link, so that the problem of water loss of the leaf vegetables in the precooling and pressure reducing process is solved, and the effects of sterilization and senescence delaying are achieved; the mixed gas of helium and hydrogen is used for repressing, so that the damage of pressure to the leaf vegetables is reduced, the oxidation resistance of tissues is improved, the storage period of the leaf vegetables is prolonged, and the method has important significance for postharvest fresh-keeping of the leaf vegetables in high-temperature seasons.)

1. A vacuum precooling preservation technology for harvesting leaf vegetables in high-temperature seasons is characterized by comprising the following steps:

step 1: placing the freshly harvested leaf vegetables without diseases and insect pests in a vacuum pre-cooling chamber for pre-cooling;

step 2: carrying out pressure maintaining atomization treatment on the precooled leaf vegetables, wherein the atomized liquid after the atomization treatment is a fresh-keeping liquid;

and step 3: supplementing air and repressing the leaf vegetables subjected to pressure maintaining atomization treatment to 1 standard atmospheric pressure;

and 4, step 4: storing or transporting the re-pressed leaf vegetables at low temperature.

2. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: the leaf vegetables in the step 1 are bright in color and have no yellow leaves and diseases within 2 hours after being harvested.

3. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: the pre-cooling parameters preset in the vacuum pre-cooling chamber in the step 1 are as follows: the final temperature is 6 ℃, the final pressure is 800-900 Pa, and the time is 30-40 min.

4. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: and 2, the atomization system for atomization treatment is arranged in the center of the top of the vacuum chamber and is in a circular radiation mist-like state, the particle diameter is 30-40 mu m, and the atomization time is 5 min.

5. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: in the step 2, the preservation solution is an epsilon-polylysine solution with the concentration of 0.2-0.4 g/L.

6. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: in the step 2, the fresh-keeping solution is the taxifolin with the concentration of 6-10 mg/L.

7. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: in the step 2, the fresh-keeping solution is tannin with the concentration of 1-7 mg/L.

8. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: in the gas supplementing process in the step 3, the supplemented gas is helium mixed gas with the concentration of 40-60% or hydrogen mixed gas with the concentration of 20-60 mu L/L.

9. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: in the step 2, the fresh-keeping liquid is 0.4g/L epsilon-polylysine +8mg/L taxifolin +4mg/L tannin, and in the air supplementing process in the step 3, the supplemented gas is helium gas with the concentration of 50% and hydrogen gas with the concentration of 45 mu L/L.

10. The vacuum precooling preservation technology for the leaf vegetables harvested in the high-temperature season as claimed in claim 1, characterized in that: the low-temperature storage temperature in the step 4 is 0-5 ℃; the transportation condition is that the transportation is carried out for 1-3 days at the low temperature of 0-5 ℃, or for 1 day at the normal temperature of 20-25 ℃.

Technical Field

The invention relates to a vacuum precooling preservation technology for harvesting leafy vegetables in high-temperature seasons, belonging to the technical field of vegetable preservation.

Background

The leaf vegetables contain various nutrient components and are popular with consumers. However, the leaf vegetables harvested in high-temperature seasons have a large amount of field heat, so that roots of the leaf vegetables carry a large amount of bacteria, and due to the characteristics of large leaf surface area, vigorous respiration and the like, the growth and propagation speed of microorganisms is accelerated, so that the leaf vegetables are rapidly yellowed, rotted and aged, and the shelf life at normal temperature is only 1-2 days. Therefore, it is important to find an effective preservation technology for harvesting the leafy vegetables in high-temperature seasons.

Vacuum precooling is a common leaf vegetable fresh-keeping technology. Vacuum cooling (vacuum cooling) is a principle of evaporating and absorbing heat by reducing the pressure of a vacuum chamber to reduce the boiling point of water on the surface and in the tissue of vegetables. The vacuum precooling cooling time is short, the cooling is uniform, the field heat of the picked leaf vegetables can be quickly eliminated, and the temperature of the leaf vegetables is quickly reduced to the preset temperature. When the vacuum precooler works, the three processes are mainly carried out: a pressure reduction process, wherein after starting up, the vacuum pump continuously pumps air, and the pressure in the vacuum chamber is gradually reduced; maintaining the pressure, namely maintaining the pressure at constant low pressure for a period of time after the temperature reaches the set temperature; and in the re-pressing process, starting a vacuum pump, and pumping air into the vacuum chamber to quickly restore the pressure of the vacuum chamber to 1 standard atmospheric pressure. However, vacuum precooling easily causes the loss of the quality of the leaf vegetables and seriously affects the freshness of the leaf vegetables. The traditional vacuum precooling method usually adopts a method of spraying or soaking before precooling to reduce the water loss of the leaf vegetables, but the treatment wastes time and labor; or atomizing equipment is adopted in the precooling and depressurization process, but the vacuum pump can take away part of moisture in the air exhaust process, so that the working efficiency of the vacuum pump is influenced. Therefore, the problem that the vacuum precooling technology is urgently needed to solve is to reduce the water loss rate of the leaf vegetables in a better way and prolong the storage period of the leaf vegetables.

Epsilon-Polylysine (epsilon-PL) is a functional polypeptide which is mainly extracted after being separated from metabolite of streptomyces, and belongs to natural preservative. Because of the characteristics of good water solubility, wide antibacterial range, strong heat stability and the like, the preservative has been widely applied to the field of preservation of foods such as rice, meat products, aquatic products, fruit juice and the like at present. Research indicates that the storage period of fresh-cut Hangzhou Chinese cabbage and spinach can be delayed by the epsilon-polylysine soaking treatment, but the application of the epsilon-polylysine soaking treatment in the aspect of vacuum precooling technology is not reported.

Plant senescence is closely related to oxidative damage caused by reactive oxygen species, and with the accumulation of reactive oxygen species, the senescence process of tissues is accelerated. Taxifolin (TFL) is a natural polyphenol compound found in plants, is commonly present in various plants such as fruits and vegetables, and is an important natural antioxidant which is necessary to be supplemented by human bodies. It has strong antioxidant capacity, and can effectively remove free radicals, protect and repair cells, and prevent vitamin C from being oxidized. Tannin is an important plant secondary metabolism polyphenol product, can be combined with alkaloid, polysaccharide, protein, metal ions and the like, and has the active effects of capturing free radicals, inhibiting bacteria, resisting oxidation, participating in derivatization reaction and the like. Both substances have strong free radical scavenging ability and have wide application prospect in the anti-aging application of leaf vegetables.

Hydrogen (Hydrogen, H)₂) Is a plant endogenous signal molecule, and researches show that H₂Relates to a plant hormone signal transduction path, participates in defense response, flowering and seed germination under abiotic stress of plants, and can delay the maturation and the aging of fruits and vegetables. Helium (Helium, He), the most inert element, is one of the rare gases. Helium is a colorless, odorless inert gas that is generally not curable at standard atmospheric pressure, is chemically inert, and is generally difficult to react with other substances. Helium is non-corrosive and can be stored by any general material at normal temperature. At present, no study on the aspect of leaf vegetable preservation by helium is reported.

Disclosure of Invention

The invention discloses a vacuum precooling preservation technology for leafy vegetables harvested in high-temperature seasons, which aims to solve the problems of etiolation and aging caused by water loss and serious shortening of transportation and shelf life of the leafy vegetables harvested in high-temperature seasons.

The invention discloses a vacuum precooling preservation technology for harvesting leafy vegetables in high-temperature seasons, which comprises the following steps:

step 1: placing the freshly harvested leaf vegetables without diseases and insect pests in a vacuum pre-cooling chamber for pre-cooling;

step 2: carrying out pressure maintaining atomization treatment on the precooled leaf vegetables, wherein the atomized liquid after the atomization treatment is a fresh-keeping liquid;

and step 3: supplementing air and repressing the leaf vegetables subjected to pressure maintaining atomization treatment to 1 standard atmospheric pressure;

and 4, step 4: storing or transporting the re-pressed leaf vegetables at low temperature.

Further: the leaf vegetables in the step 1 are bright in color and have no yellow leaves and diseases within 2 hours after being harvested.

Further: the pre-cooling parameters preset in the vacuum pre-cooling chamber in the step 1 are as follows: the final temperature is 6 ℃, the final pressure is 800-900 Pa, and the time is 30-40 min.

Further: and 2, the atomization system for atomization treatment is arranged in the center of the top of the vacuum chamber and is in a circular radiation mist-like state, the particle diameter is 30-40 mu m, and the atomization time is 5 min.

Further: in the step 2, the preservation solution is an epsilon-polylysine solution with the concentration of 0.2-0.4 g/L.

Further: in the step 2, the fresh-keeping solution is the taxifolin with the concentration of 6-10 mg/L.

Further: in the step 2, the fresh-keeping solution is tannin with the concentration of 1-7 mg/L.

Further: in the gas supplementing process in the step 3, the supplemented gas is helium mixed gas with the concentration of 40-60% or hydrogen mixed gas with the concentration of 20-60 mu L/L.

Further: in the step 2, the fresh-keeping liquid is 0.4g/L epsilon-polylysine +8mg/L taxifolin +4mg/L tannin, and in the air supplementing process in the step 3, the supplemented gas is helium gas with the concentration of 50% and hydrogen gas with the concentration of 45 mu L/L.

Further: the low-temperature storage temperature in the step 4 is 0-5 ℃; the transportation condition is that the transportation is carried out for 1-3 days at the low temperature of 0-5 ℃, or for 1 day at the normal temperature of 20-25 ℃.

Has the advantages that: the vacuum precooling preservation technology for harvesting the leaf vegetables in the high-temperature season solves the problem of water loss of the leaf vegetables caused by the vacuum precooling technology, and simultaneously achieves the purposes of effectively sterilizing, removing free radicals and delaying the aging process. The technology is simple, convenient and easy to implement, efficient and safe, and provides technical reference for postharvest treatment and subsequent preservation of the leaf vegetables in the production area.

Detailed Description

The present invention is further illustrated by the following examples, which are intended to be purely exemplary and are not intended to limit the scope of the invention, as various equivalent modifications of the invention will occur to those skilled in the art upon reading the present disclosure and fall within the scope of the appended claims.

The invention relates to a vacuum precooling preservation technology for harvesting leafy vegetables in high-temperature seasons, which specifically comprises the following steps:

step 1: placing the freshly harvested leaf vegetables without diseases and insect pests in a vacuum pre-cooling chamber for pre-cooling, wherein the leaf vegetables are bright-colored and have no yellow leaves and diseases within 2 hours after harvesting, and pre-cooling parameters preset in the vacuum pre-cooling chamber are as follows: the final temperature is 6 ℃, the final pressure is 800-900 Pa, and the time is 30-40 min;

step 2: carrying out pressure-maintaining atomization treatment on the precooled leaf vegetables, wherein atomization liquid of the atomization treatment is fresh-keeping liquid, an atomization system of the atomization treatment is arranged in the center of the top of a vacuum chamber and is in a round radial mist state, the diameter of particles is 30-40 mu m, the atomization time is 5min, the fresh-keeping liquid is epsilon-polylysine solution with the concentration of 0.2-0.4 g/L or taxifolin with the concentration of 6-10 mg/L or tannin with the concentration of 1-7 mg/L, and the most preferable fresh-keeping liquid is 0.4g/L epsilon-polylysine +8mg/L taxifolin +4mg/L tannin;

and step 3: supplementing air to the leaf vegetables subjected to pressure maintaining atomization treatment and repressing to 1 standard atmospheric pressure, wherein the supplemented gas is helium mixed gas with the concentration of 40-60% or hydrogen mixed gas with the concentration of 20-60 mu L/L, and the most preferable supplemented gas is helium with the concentration of 50% and hydrogen mixed gas with the concentration of 45 mu L/L;

and 4, step 4: storing or transporting the re-pressed leaf vegetables at a low temperature of 0-5 ℃; the transportation condition is that the transportation is carried out for 1 to 3 days at the low temperature of 0 to 5 ℃, or for 1 day at the normal temperature of 20 to 25 ℃.

Example 1

The embodiment provides a vacuum precooling and fresh-keeping technology for harvesting leaf vegetables in high-temperature seasons, which is characterized in that Shanghai green vegetables which are bright in color and have no yellow leaves and diseases are harvested from the field, the Shanghai green vegetables are bagged and placed in a vacuum precooling chamber, a temperature sensor is inserted into the center of a vegetable heart, and the final precooling temperature is set to be 6 ℃. Precooling is started, when the temperature is reduced to 6 ℃, the pressure is kept constant at 800-900 pa, an atomization system provided with epsilon-polylysine (0.2, 0.3 and 0.4g/L) solution is started, atomization is stopped after 5min, and then air is introduced to return to 1 standard atmospheric pressure. And (3) after pre-cooling is finished, the time is about 30-40 min, the Shanghai green is taken out and placed into a basket, and the Shanghai green is stored at a low temperature (0-5 ℃).

Example 2

The atomization system was fitted with a solution of taxifolin (6, 8 and 10mg/L) and the other procedure was the same as in example 1.

Example 3

The atomization system was equipped with tannin (1, 4 and 7mg/L) solutions and the other methods were the same as in example 1.

Example 4

The atomization system was fitted with distilled water and repressurized with helium (40, 50 and 60%). The other methods were the same as in example 1.

Example 5

The atomization system was fitted with distilled water and repressurized with hydrogen (20, 45 and 60. mu.L/L) in the same manner as in example 1.

Comparative example 1

The atomization system was not installed, and the other method was the same as in example 1.

Comparative example 2

The atomization system was provided with distilled water and the other method was the same as in example 1.

The treated Shanghai green of examples 1-5 and comparative examples 1-2 was stored at a low temperature (0-5 ℃) and the maximum number of days of storage was recorded.

TABLE 1 fresh-keeping Effect of examples 1 to 5 and comparative examples 1 to 2 in different groups

Based on the results of examples 1-5 and comparative examples 1-2, the formulations of the preservative solution and the gas mixture were further optimized

Example 6

The embodiment provides a vacuum precooling and fresh-keeping technology for harvesting leaf vegetables in high-temperature seasons, which is characterized in that Shanghai green vegetables which are bright in color and have no yellow leaves and diseases are harvested from the field, the Shanghai green vegetables are bagged and placed in a vacuum precooling chamber, a temperature sensor is inserted into the center of a vegetable heart, and the final precooling temperature is set to be 6 ℃. Precooling is started, when the temperature is reduced to 6 ℃, the pressure is constant at 800-900 pa, an atomization system with 0.4g/L epsilon-polylysine, 8mg/L taxifolin and 4mg/L tannin fresh-keeping liquid is started, atomization is stopped after 5min, and then mixed gas containing 50% helium and 45 mu L/L hydrogen is introduced for recompression. And after precooling is finished, taking out the Shanghai green, placing the Shanghai green into a basket, and storing or transporting for sale at a low temperature (0-5 ℃).

Comparative example 3

Air repressurization was used in the same manner as in example 6.

Comparative example 4

The atomization system was charged with distilled water and repressurized with a mixture of 50% helium and 45. mu.L/L hydrogen, in the same manner as in example 6.

A part of the treated Shanghai Qing in example 6 and comparative examples 3-4 was stored at a low temperature (0-5 ℃) and the other part was directly transported for shelf sale, and the maximum number of days for storage was recorded.

TABLE 2 fresh-keeping Effect of example 6 and comparative examples 3 to 4 in different groups

As can be seen from Table 1, the longest period of the storage in the open sea can be obtained by the concentration screening of the fresh-keeping liquid and the gas, wherein the storage period is 0.4g/L of epsilon-polylysine or 8mg/L of taxifolin or 4mg/L of tannin by atomization treatment, and the storage period is 50% helium or 45 muL/L of hydrogen by recompression treatment.

As can be seen from Table 2, the low-temperature storage period and the shelf life of the Shanghai green can be remarkably prolonged by atomizing the Shanghai green in the vacuum precooling process by using 0.4g/L epsilon-polylysine, 8mg/L taxifolin and 4mg/L tannin preservation solution and then carrying out recompression treatment by combining 50% helium and 45 mu L/L hydrogen.

In conclusion, the invention aims to provide a vacuum precooling preservation technology for harvesting leaf vegetables in high-temperature seasons, the method uses 0.4g/L epsilon-polylysine +8mg/L taxifolin +4mg/L tannin preservation solution to atomize the Shanghai green in the precooling and pressure maintaining process, and 50% helium +45 mu L/L hydrogen is introduced in the repressing process, so that the problem of water loss of the leaf vegetables caused by the vacuum precooling technology is solved, meanwhile, the vacuum precooling technology can effectively sterilize, remove free radicals, delay the aging of the leaf vegetables, and obviously prolong the storage period, the transportation period and the normal-temperature shelf life of the leaf vegetables. The technology is simple, convenient and easy to implement, efficient and safe, and provides technical reference for postharvest treatment and subsequent preservation of the leaf vegetables in the production area.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.