Method for Preservation of Fresh Plants by Vacuum Pre-Cooling Synchronously Combined with Modified Atmosphere Technique

Abstract

A method for the preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique includes: (1) screening field-picked fresh plants, and selecting individuals with uniform size, consistent maturity, and no obvious defects; (2) placing the screened individuals in a vacuum pre-cooler for pre-cooling; (3) after the plants are pre-cooled to the final temperature, the device automatically shuts down the refrigerator and vacuum pump, and the pre-configured mixed gas is introduced from the intake air inlet into the vacuum chamber for re-pressing; and (4) taking the re-pressed fresh plants out of the pre-cooler, and performing modified atmosphere packaging and refrigerating. A specific mixed gas can be filled during the vacuum pre-cooling and re-pressure stages, and the re-pressure process after pre-cooling is closely integrated with the modified atmosphere technique to reduce the respiration metabolism of the plant to a suitable low level, significantly prolonging the shelf life of the product.

Claims

1. A method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique, the method comprising: (1) screening field-picked fresh plants, and selecting individuals with uniform size, consistent maturity, and no obvious defects; (2) placing the screened individuals in a vacuum pre-cooler for pre-cooling; (3) after the plants are pre-cooled to the final temperature, the vacuum pre-cooler automatically shuts down a refrigerator and a vacuum pump, and pre-configured mixed gas is introduced from an intake air inlet into a vacuum chamber for re-pressing; and (4) taking the re-pressed fresh plants out of the pre-cooler, and performing modified atmosphere packaging and refrigerating.

2. The method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique according to claim 1, wherein the fresh plants described in the step (1) refer to vegetables or edible fungi.

3. The method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique according to claim 2, wherein: the vegetables described in the step (1) are Chinese cabbage, Chinese kale, lettuce, green pepper or broccoli; or the edible fungi described in the step (1) are shiitake, straw mushroom or boletus of steppes.

4. The method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique according to claim 1, wherein the pre-cooling in the step (2) refers to pre-cooling for 8-30 min to a temperature of 1 C. to 15 C.

5. The method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique according to claim 2, wherein: the pre-configured mixed gas described in the step (3) refers to a mixed gas composed of O.sub.2, CO.sub.2 and N.sub.2; when the fresh plants described in the step (1) are vegetables, the proportion of the gas filled in the modified atmosphere described in the step (3) is O.sub.2 3% to 5%, CO.sub.2 3% to 7%, and N.sub.2 for the balance; when the fresh plants described in the step (1) are edible fungi, the proportion of the gas filled in the modified atmosphere described in the step (3) is O.sub.2 1% to 2%, CO.sub.2 10% to 20%, and N.sub.2 for the balance.

6. The method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique according to claim 1, wherein the re-pressing described in the step (3) refers to re-pressing for 1-3 min.

7. The method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique according to claim 2, wherein: the gas filled in the modified atmosphere described in the step (4) is a mixed gas composed of O.sub.2, CO.sub.2 and N.sub.2; when the fresh plants described in the step (1) are vegetables, the proportion of the gas filled in the modified atmosphere described in the step (4) is O.sub.2 3% to 5%, CO.sub.2 3% to 7%, and N.sub.2 for the balance; when the fresh plants described in the step (1) are edible fungi, the proportion of the gas filled in the modified atmosphere described in the step (3) is O.sub.2 1% to 2%, CO.sub.2 10% to 20%, and N.sub.2 for the balance.

8. The method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique according to claim 1, wherein the refrigerating described in the step (4) refers to refrigerating at 1 C. to 12 C.

9. The method for preservation of fresh plants by vacuum pre-cooling synchronously combined with modified atmosphere technique according to claim 2, wherein when the fresh plants described in the step (1) are edible fungi, the pre-cooling described in the step (2) refers to pre-cooling for 10-20 min to a final temperature of 1 C. to 5 C., and the refrigerating described in the step (4) refers to refrigerating at 2 C. to 4 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 is a schematic diagram of a vacuum pre-cooling device used in an example of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The present invention will be further described in detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

EXAMPLE 1

[0050] Lettuce was selected that had uniform size, consistent maturity, and no obvious defects. Pre-cooling was performed within 3 hours after harvesting. The lettuce was stacked neatly in the sample basket and placed in a vacuum chamber of a pre-cooling vacuum machine (VC-1601 from Dongguan Kemeisi Refrigeration Equipment Co., Ltd.) to be pre-cooled. The operation screen was used to set the pre-cooling time to 8 min, the pre-cooling final temperature to 1 C., and the re-pressure time to 1 min. After the pre-cooling final temperature was reached, re-pressure was performed: the pre-configured mixed gas was introduced from the intake air inlet (Dansensor gas mixer, from Danish Dansensor, MAP Mix ProV 3-Gas), having a specific content proportion of O.sub.2 3%, CO.sub.2 4% and N.sub.2 93%. After 1 min of re-pressure, the lettuce was taken out for modified atmosphere packaging, with the gas introduced having a content proportion of O.sub.2 3%, CO.sub.2 4% and N.sub.2 93%. The product was refrigerated at 1 C. after being packaged.

[0051] The control group used the lettuce of the same quality. Pre-cooling was performed within 3 hours after harvesting. The lettuce was stacked neatly in the sample basket and placed in the vacuum chamber of the pre-cooling vacuum machine (VC-1601 from Dongguan Kemeisi Refrigeration Equipment Co., Ltd.) to be pre-cooled. The operation screen was used to set the pre-cooling time to 8 min and the pre-cooling final temperature to 1 C. The re-pressure process after the pre-cooling final temperature was reached included conventionally filling air for the re-pressure time of 1 min. After the re-pressure, the lettuce was taken out of the vacuum chamber for modified atmosphere packaging. The proportion of the filled gas was O.sub.2 3%, CO.sub.2 4% and N.sub.2 93%. All the lettuce was packaged within 15 minutes after it was taken out and then refrigerated at 1 C.

[0052] The shelf life of the lettuce in the control group was 27 days, while the quality of the lettuce stored by this method was slowly declined such that the shelf life was 35 days. Compared with the existing advanced methods, the shelf life was extended by 8 days, and the preservation effect was good.

EXAMPLE 2

[0053] Green peppers were selected as raw materials that had consistent maturity, were clean, fresh and crisp, had no rot, odor, cold injury, frost damage or mechanical injury. Pre-cooling was performed within 3 hours after harvesting. The green peppers were stacked neatly in the sample basket and placed in the vacuum chamber of the pre-cooling vacuum machine (VC-1601 from Dongguan Kemeisi Refrigeration Equipment Co., Ltd.) to be pre-cooled. The operation screen was used to set the pre-cooling time to 30 min, the pre-cooling final temperature to 15 C., and the re-pressure time to 3 min. After the pre-cooling final temperature was reached, re-pressure was performed: the pre-configured mixed gas was introduced from the intake air inlet (Dansensor gas mixer, from Danish Dansensor, MAP Mix ProV 3-Gas), having a specific content proportion of O.sub.2 5%, CO.sub.2 3% and N.sub.2 92%. After 3 min of re-pressure, the green peppers were taken out for modified atmosphere packaging, with the gas introduced having a content proportion of O.sub.2 5%, CO.sub.2 3% and N.sub.2 92%. The green peppers were refrigerated at 12 C. after being packaged.

[0054] The control group used the green peppers of the same quality. Pre-cooling was performed within 3 hours after harvesting. The green peppers were stacked neatly in the sample basket and placed in the vacuum chamber of the pre-cooling vacuum machine (VC-1601 from Dongguan Kemeisi Refrigeration Equipment Co., Ltd.) to be pre-cooled. The operation screen was used to set the pre-cooling time to 30 min and the pre-cooling final temperature to 15 C. The re-pressure process after the pre-cooling final temperature was reached included conventionally filling air for the re-pressure time of 3 min. After the re-pressure, the green peppers were taken out of the vacuum chamber for modified atmosphere packaging. The proportion of the filled gas was O.sub.2 5%, CO.sub.2 3% and N.sub.2 92%. The green peppers were refrigerated at 12 C. after being packaged.

[0055] The shelf life of the green peppers in the control group was 22 days, while the quality of the green peppers treated by this preservation method was slowly declined such that the shelf life was 30 days. Compared with the existing preservation method, the shelf life was extended by 8 days, and the preservation effect was good.

EXAMPLE 3

[0056] Broccoli was selected that had consistent maturity, uniform size, uniform color, no obvious defects, no mechanical injury or blight, and was stacked neatly in the sample basket. The broccoli was pre-cooled within 3 hours after being harvested, and was placed in the vacuum chamber of the pre-cooling vacuum machine (VC-1601 from Dongguan Kemeisi Refrigeration Equipment Co., Ltd.) to be pre-cooled. The operation screen was used to set the pre-cooling time to 18 min, the pre-cooling final temperature to 5 C., and the re-pressure time to 2 min. After the pre-cooling final temperature was reached, re-pressure was performed: the pre-configured mixed gas was introduced from the intake air inlet (Dansensor gas mixer, from Danish Dansensor, MAP Mix ProV 3-Gas), having a specific content proportion of O.sub.2 3%, CO.sub.2 7% and N.sub.2 90%. After 2 min of re-pressure, the broccoli was taken out for modified atmosphere packaging, with the gas introduced having a content proportion of O.sub.2 4%, CO.sub.2 3% and N.sub.2 93%. The broccoli was refrigerated at 5 C. after being packaged.

[0057] The control group used the broccoli of the same quality. Pre-cooling was performed within 3 hours after harvesting. The broccoli was stacked neatly in the sample basket and placed in the vacuum chamber of the pre-cooling vacuum machine (VC-1601 from Dongguan Kemeisi Refrigeration Equipment Co., Ltd.) to be pre-cooled. The operation screen was used to set the pre-cooling time to 18 min and the pre-cooling final temperature to 5 C. The re-pressure process after the pre-cooling final temperature was reached included conventionally filling air for the re-pressure time of 2 min. After the re-pressure, the broccoli was taken out of the vacuum chamber for modified atmosphere packaging. The proportion of the filled gas was O.sub.2 4%, CO.sub.2 3% and N.sub.2 93%. The broccoli was refrigerated at 5 C. after being packaged.

[0058] The shelf life of the broccoli in the control group was 15 days, while the quality of the broccoli treated by this preservation method was slowly declined such that the shelf life was 20 days. Compared with the existing preservation method, the shelf life was extended by 5 days, and the preservation effect was good.

EXAMPLE 4

[0059] Shiitake was harvested, and fruiting bodies that were intact and had no obvious defects were selected, with inedible parts removed. Pre-cooling was performed within 3 hours after harvesting. The shiitake was stacked neatly in the sample basket and placed in the vacuum chamber of the pre-cooling vacuum machine (VC-1601 from Dongguan Kemeisi Refrigeration Equipment Co., Ltd.) to be pre-cooled. The operation screen was used to set the vacuum pre-cooling time to 10 min, the pre-cooling final temperature to 5 C. and the re-pressure time to 2 min. After the pre-cooling final temperature was reached, re-pressure was performed: the pre-configured mixed gas was introduced (Dansensor gas mixer, from Danish Dansensor, MAP Mix ProV 3-Gas), having a specific content proportion of O.sub.2 1%, CO.sub.2 15% and N.sub.2 84%. After 2 min of re-pressure, the shiitake was taken out for modified atmosphere packaging, with the gas introduced having a content proportion of O.sub.2 1%, CO.sub.2 15% and N.sub.2 84%. The shiitake was stored at 2 C. after being packaged.

[0060] The control group used shiitake of the same batch, and selected fruiting bodies that were intact and had no obvious defects, with inedible parts removed. Within 3 hours after being harvested, the shiitake was put into a 2 C. cold store for pre-cooling and storage.

[0061] The shelf life of the control group was 10 days. The shiitake treated by this preservation method had a shelf life of 18 days, a water loss rate of 18%, and Vc content reduced by 55%. The shiitake treated by this preservation method had flexible pilei, normal color and mushroom odor. Compared with the control group, the shiitake treated by this preservation method was significantly extended in the shelf life by 8 days.

EXAMPLE 5

[0062] Boletus of steppes was harvested, and fruiting bodies that were intact and had no obvious defects were selected, with inedible parts removed. Pre-cooling was performed within 3 hours after harvesting. The boletus of steppes was stacked neatly in the sample basket and placed in the vacuum chamber of the pre-cooling vacuum machine (VC-1601 from Dongguan Kemeisi Refrigeration Equipment Co., Ltd.) to be pre-cooled. The operation screen was used to set the vacuum pre-cooling time to 20 min and the pre-cooling final temperature to 1 C. After the pre-cooling final temperature was reached, re-pressure was performed: the pre-configured mixed gas was introduced (Dansensor gas mixer, from Danish Dansensor, MAP Mix ProV 3-Gas), having a specific content proportion of O.sub.2 2%, CO.sub.2 15% and N.sub.2 83%. After 2 min of re-pressure, the boletus of steppes was taken out for modified atmosphere packaging, with the gas introduced having a content proportion of O.sub.2 2%, CO.sub.2 15% and N.sub.2 83%. The boletus of steppes was refrigerated at 4 C. after being packaged.

[0063] The control group used boletus of steppes of the same batch, and fruiting bodies that were intact and had no obvious defects were selected, with inedible parts removed. Within 3 hours after being harvested, the boletus of steppes was put into a 4 C. cold store for pre-cooling and storage.

[0064] The shelf life of the boletus of steppes in the control group was 32 days, while the quality of the boletus of steppes treated by this preservation method was slowly declined such that the shelf life was 45 days. Compared with the existing preservation method, the shelf life was extended by 13 days, and the preservation effect was good.

[0065] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the foregoing embodiments, and any other alterations, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should all be equivalent replacement methods and included in the protection scope of the present invention.