JP5822171B2 - Method for preventing browning of green vegetables and low-temperature steam heating apparatus used therefor - Google Patents

Description

  TECHNICAL FIELD The present invention relates to maintaining the freshness of green vegetables such as lettuce, and more particularly to a method for preventing browning of green vegetables and extending the shelf life of green vegetables, and a low-temperature steam heating apparatus used therefor.

Providing consumers with fresh vegetables is the most considered in each case of production, distribution, and sales, and various attempts have been made for this purpose.

  As this type of prior art, for example, the treated hot water is controlled at a hot water temperature of 47.5 ± 10 ° C. by applying a stirring flow, and the controlled low temperature hot water flow is used for at least 10 minutes. There is a method in which heat treatment is performed at low temperature, and the waxy substance on the surface is dissolved together with washing to remove fungi and sterilize (Patent Document 1).

  In addition, a method in which vegetables are immersed in an alkaline aqueous solution and then heated in hot water or steam at about 80 to 100 ° C. for about 0.5 to 20 minutes has been attempted (Patent Document 2).

JP 2002-119207 A JP 2006-296325 A

  However, the prior art described in Patent Document 1 is excellent in terms of cleaning, sterilization, and shelf life, but it is necessary to immerse the vegetables in hot water for at least 10 minutes. There was a problem that the removal of the axe progressed and the whole became watery, and the original taste of lettuce was impaired.

  The prior art described in Patent Document 2 is a method of heating in hot water or steam at about 80 to 100 ° C. for about 0.5 to 20 minutes. It is effective for fading prevention and sterilization, but if the same heat treatment is applied to vegetables that eat leaf parts such as lettuce, the leaf parts will be shrunken or discolored, or the original taste of the vegetables will be lost. There was a problem that it was greatly damaged.

  The present invention was devised to solve the above-described problems in the prior art, and is excellent in washing and disinfecting and improving the effect of preventing browning and discoloration without deteriorating the original taste of vegetables. It is an object to create a method for preventing browning of vegetables and a low-temperature steam heating device used therefor.

  Among the means for solving the above-mentioned problems, the main configuration of the method for preventing browning of green vegetables according to the first invention is to place the green vegetables after the primary washing in hot water at least at 45 to 55 ° C. It is characterized by having a soaking treatment step of immersing for 2 minutes and a low-temperature steam heating treatment step of exposing the green vegetables after the soaking treatment step in a steam atmosphere of 40 to 50 ° C. for 18 to 22 minutes. .

  In the main invention described above, cleaning and sterilization are performed in the pickling process step after removing relatively large dirt adhering to the periphery of green vegetables such as mud in the primary cleaning, and then the green vegetables are subjected to a predetermined water vapor atmosphere. By exposing to the inside and performing low-temperature steam heat treatment, it is possible to achieve more effective cleaning and sterilization without restraining or discoloring the leaf portion by suppressing the degree of progress of the release.

  Moreover, the other structure of 1st invention sets the initial hot water temperature which immerses a green vegetable in said main structure to said main structure to 51-53 degreeC, and the hot water temperature which takes out the said green vegetable is 47-49 degreeC. Is added.

In the main configuration, washing and sterilization of green vegetables can be achieved under optimum hot water temperature.

  Moreover, the other structure of 1st invention adds the structure that the immersion time which immerses the green vegetable in an immersion process process shall be 50 to 70 second to one of the said structures.

  In this configuration, by performing cleaning and sterilization within a limited time of 50 to 70 seconds, it is possible to suppress the degree of progress of unloading and effectively prevent leaf portion contraction and discoloration.

Moreover, the other structure of 1st invention adds the structure that the weight ratio of the green vegetable soaked in the immersion treatment process and the hot water for immersion is set to 1:12 or more to any of the above structures. is there.

In this configuration, it is possible to achieve the hot water temperature of 47 to 49 ° C. when the green vegetable is immersed in the initial hot water temperature of 51 to 53 ° C. for 50 to 70 seconds and taken out.

  Moreover, the other structure of 1st invention adds the structure that the temperature of water vapor | steam shall be 47-49 degreeC in the low-temperature-steam-heat-treatment process to one of the said structures.

  In this configuration, cleaning and sterilization can be achieved without causing contraction or discoloration of the green vegetables during the low-temperature steam heat treatment process.

  In addition, in another configuration of the first invention, a configuration in which the processing time of the low-temperature steam heat treatment step exposed to the steam atmosphere is 18 to 22 minutes is added to any of the above configurations.

  In this configuration, the low-temperature steam heat treatment process can be achieved more reliably.

  According to another configuration of the first invention, in any one of the above configurations, the primary cleaning includes a cleaning step with running water, a cleaning step with a sodium hypochlorite diluent, and a cleaning step with a neutral detergent. Is added.

  In this configuration, it is possible to achieve the effect of the cleaning and sterilization treatment in the subsequent secondary cleaning by removing in advance the relatively large dirt adhering to the periphery of the green vegetable such as mud.

  Moreover, the other structure of 1st invention adds the structure that a green vegetable is lettuce to one of the said structures.

  With this configuration, it is possible to achieve more effective cleaning and sterilization of lettuce.

Moreover, the main structure of the low temperature steam heating apparatus of the green vegetable which is 2nd invention among the means for solving the said subject is the water tank part which stores water at least in the sealed process chamber, and the water in this water tank part A heater that heats the water, a pump that pumps out the water in the water tank, a lead-in pipe that guides the pumped water to a position above the water tank, and a position that is provided at the end of the pipe and from the position above the water tank It has a spray nozzle part that spouts water toward the water in the water tank part, and a net shelf part on which green vegetables are placed above the spray nozzle part, and is heated to a predetermined temperature by a heater A low-temperature steam heating device in which green vegetables placed on the net shelf are heated by water vapor generated when water is sprayed from the spray nozzle to the water in the water tank ,
It is said that a condensate plate is provided at the ceiling in the processing chamber to collect water vapor, condense it into water, and return it to the water tank .

In the main configuration of the second invention, water vapor is generated when the hot water sprayed from the nozzle is mixed with the hot water in the tank portion vigorously. The green vegetables placed in the net shelf in the path can be heated at a low temperature.
In addition, the ceiling part of the processing chamber is provided with a condensing plate that collects water vapor, condenses it into water, and returns it to the water tank part. Efficient use of water in the device can be achieved.

  In addition, another configuration of the second invention is the same as the main configuration of the second invention, except that the pump is sent from the water tank section to the injection nozzle section via the lead-in pipe, sprayed from the injection nozzle section, and returned to the water tank section again. The structure that water is circulated along is added.

  In this configuration, by circulating water (hot water), low-temperature heat treatment can be efficiently performed without supplying water.

  In another configuration of the second invention, the heater is controlled so that the water temperature in the water tank unit matches the temperature in the processing chamber, in addition to any of the above configurations. .

  In this configuration, the temperature in the processing chamber can be kept constant.

  In addition, another configuration of the second invention is obtained by adding a configuration in which the pump is controlled so as to be able to adjust the amount of water flowing in the drawing pipe to any one of the above configurations.

  In this configuration, the humidity and temperature in the processing chamber can be kept constant.

  In another configuration of the second aspect of the present invention, in any one of the configurations described above, a carry-in port provided at one of the left and right ends of the processing chamber, a carry-out port provided at the other end, and the carry-in port toward the carry-out port. And a conveying means that moves, and is configured to heat the green vegetable while being conveyed by the conveying means.

With this configuration, it is possible to efficiently heat a large amount of green vegetables at a low temperature.

  Furthermore, the other structure of 2nd invention adds the structure that lettuce is made into object as a green vegetable to one of the said structures.

  In this configuration, it is possible to achieve cleaning and sterilization of the lettuce by low-temperature heat treatment.

  Since the present invention has the above-described configuration, the following effects can be obtained.

In the method for preventing browning of green vegetables according to the first invention, cleaning and sterilization are performed in a pickling process step after removing relatively large dirt adhering to the periphery of green vegetables such as mud in the primary cleaning, By exposing the green vegetables to a predetermined water vapor atmosphere and performing a low-temperature steam heat treatment, the green vegetables can be more effectively washed and sterilized. Thereby, the shelf life of green vegetables can be extended by 2 to 3 days or more. And since it becomes possible to suppress that unloading is performed more than necessary, it can prevent that the original taste of vegetables is impaired.

  Further, the low-temperature steam heating apparatus according to the second invention can provide a low-temperature steam heating apparatus suitable for the low-temperature steam heat treatment step, whereby the low-temperature steam heat treatment for green vegetables can be performed in an environment such as an appropriate temperature and humidity. It is possible to perform reliably.

It is the whole process figure which shows the browning prevention method of the green vegetable which is this invention. It is process drawing which shows the detail of primary washing | cleaning among all the processes of the browning prevention method. It is a test result table | surface which shows the result of having performed the bacteria test | inspection and the external appearance test | inspection about cut lettuce. It is a block diagram which shows the outline of the low temperature steam heating apparatus which is this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Hereinafter, an example in which lettuce is used as a green vegetable will be described.

  FIG. 1 is an overall process diagram showing the method for preventing browning of green vegetables according to the present invention, and FIG. 2 is a process diagram showing details of primary cleaning among all the steps of the browning prevention method.

  As shown in FIG. 1, the method for preventing browning of green vegetables of the present invention removes relatively large dirt adhering to the periphery of lettuce such as mud by primary cleaning (step S1), and then secondary cleaning ( By providing a two-stage processing step of performing step S2), the cleaning / sterilization effect and the browning prevention effect are enhanced.

  As shown in FIG. 2, the primary cleaning (step S1) includes eight processing steps from steps S1-1 to S1-8.

  That is, in the primary cleaning (step S1), the hole lettuce is washed with running water for about 5 minutes to remove dirt such as mud and then the hole lettuce is washed with sodium hypochlorite. A processing step (step S1-2) of sterilizing using a sterilizing agent such as a diluent and washing with a neutral detergent for about 5 minutes is performed. Subsequently, after washing for about 5 minutes with running water to wash away the disinfectant and neutral detergent used in step S1-2 (step S1-3), the hole lettuce is centered and an appropriate size is obtained. A processing step (step S1-4) for cutting is performed. And after performing the process (step S1-5) which wash | cleans a cut lettuce with a neutral detergent for about 5 minutes and removes a fine stain, it wash | cleans for about 5 minutes using running water, and the process of washing away a neutral detergent (Step S1-6) is performed, followed by a treatment step (Step S1-7) for sterilizing cut lettuce for about 3 minutes using a bactericide such as sodium hypochlorite diluted solution, and then cutting using running water A treatment step (step S1-8) is performed in which the lettuce is washed for about 2 minutes to wash away the disinfectant. Thus, by washing and sterilizing most of the dirt and bacteria adhering to the lettuce in advance in the primary washing (step S1), the washing and sterilizing effect in the secondary washing can be enhanced.

  The next secondary cleaning (step S2) consists of four processing steps from the following steps S2-1 to S2-4.

  First, in step S2-1, the cut lettuce subjected to the primary cleaning process is immersed in hot water for sterilization (immersion process step). The hot water temperature at this time is preferably 45 to 55 ° C, and more preferably 51 to 53 ° C. Further, the immersion time is preferably about 0.5 to 2 minutes, and the more preferable immersion time is 50 to 70 seconds.

  Most preferably, the cut lettuce is taken out when the hot water temperature falls to 47-49 ° C. after being put into the hot water at 51-53 ° C. The time is 50 to 70 seconds. The amount of hot water for realizing this is preferably 12 liters or more with respect to 1 kg of cut lettuce, that is, an amount of hot water of 1:12 or more by weight ratio.

  In the next step S2-2, the cut lettuce after the immersion treatment process is placed in a treatment chamber of a low-temperature steam heating apparatus, which will be described later, and is subjected to sterilization and browning prevention treatment by exposure to a steam atmosphere (low-temperature steam heat treatment process). The preferred temperature in the water vapor atmosphere is 40-50 ° C, more preferably 47-49 ° C. The low temperature steam heating time exposed to the steam atmosphere is preferably 18 to 22 minutes.

In the next S step 2-3, the cut lettuce after the low-temperature steam heat treatment is washed with running water to remove the rough heat (cooling process), and in the final step S2-4, the water is drained (dehydration process) and then stored. To do.

  Here, the test results for the cut lettuce subjected to the above-described processing will be described. FIG. 3 is a list of test results showing the results of a bacterial test and an appearance test for cut lettuce.

  In FIG. 3, Comparative Examples 1 to 4 are inspection results of cut lettuce subjected to only primary cleaning, and Examples 1 to 4 are inspection results of cut lettuce subjected to secondary cleaning following the primary cleaning. . In addition, Comparative Examples 1 to 3 and Examples 1 to 3 are inspection results regarding lettuce for outdoor cultivation, and Comparative Examples 4 and Examples 4 to 6 are inspection results for lettuce for hydroponics. Note that hydroponic lettuce originally has fewer bacteria than open field lettuce.

Further, D + 1 in FIG. 3 means that one day has passed after washing, D + 2 means that two days have passed after washing, that is, (D + numerical value) means the number of days that have passed after washing. The number in the “Bacteria Audit” indicates the number of detected bacteria (general live bacteria and coliforms), and 10 ⁵ is a threshold value, less than 10 ⁵ is good, and 10 ⁵ or more is judged as impossible. In FIG. 3, the unusable part is shown in light ink color.

  “Appearance audit” indicates the quality of cut lettuce on the appearance, browning or discoloration (hereinafter referred to as “browning etc.”) or browning to the extent that there is no problem with the product. The case where the case is good (◯) and the case where it is not appropriate to make a product due to browning or the like is not possible (×).

  In the case of lettuce grown in the open field, as shown in Comparative Examples 1 to 3, the shelf life in the “bacteria test” in the case of only the primary cleaning is about 2 days after the cleaning, about 3 days at the most. It can be seen that lettuce after 4 days is not suitable as a product, and that the number of days in the “visual inspection” is 3 days after washing. In addition, as shown in Examples 1 to 3, lettuce that has been subjected to the secondary cleaning following the primary cleaning has a shelf life of 6 days or more after the cleaning in the “visual inspection”, and the shelf life in the “bacteria inspection” is cleaned. It can be seen that the last three days are the lowest, usually about four days.

  On the other hand, in the case of hydroponics, as shown in Comparative Example 4, in the case of only the primary cleaning, the shelf life in the “visual inspection” is 4 days after the cleaning, but the shelf life in the “bacteria inspection” is washed. It can be seen that lettuce that is three days later and four days after washing is not appropriate to be a product. Further, as shown in Examples 4 to 6, it can be seen that the shelf life of the lettuce subjected to the secondary cleaning subsequent to the primary cleaning is 6 days or more after the cleaning in both “bacterial inspection” and “appearance inspection”.

  Compared to the case of only the primary cleaning as described above, when the secondary cleaning is performed after the primary cleaning, both the “bacteria inspection” and the “appearance inspection” are both in the case of lettuce grown in the open field. It is possible to extend the shelf life for about 1 day or 2 days. In the case of hydroponic lettuce, it is possible to extend the shelf life for 3 days or more.

  Next, the low temperature steam heating apparatus will be described.

  FIG. 4 is a configuration diagram showing an outline of a low-temperature steam heating apparatus according to the present invention.

  The low-temperature steam heating apparatus 1 is used in the above step S2-2, and includes a processing chamber 3 for performing browning prevention processing on green vegetables. The processing chamber 3 shown in this embodiment is provided inside a box-shaped housing 2, and a door (not shown) is attached to the front surface of the housing 2 so as to be openable and closable. It comes to be taken in and out through.

  A water tank part 4 for storing water is provided at the lowermost part of the processing chamber 2, and a heater 5 for warming the water and converting it into hot water is attached in the water tank part 4. A lead-in pipe 6 is provided between the water tank part 4 and the injection chamber 7 provided at a position above the water tank part 4. One end 6a of the lead-in pipe 6 is connected to the bottom of the water tank section 4, the other end 6b is piped to the injection chamber 7 above the water tank section 4 through the side surface of the housing 2, and the injection nozzle section 9 is connected to the tip thereof. Yes.

  The injection nozzle unit 9 has a plurality of nozzles 9a arranged at predetermined intervals on the lower surface of the pipe, and the nozzle 9a can inject water (hot water) toward the water tank unit 4.

  A net shelf 10 is provided at an intermediate height position of the housing 2. The net shelf 10 shown in the present embodiment has a five-stage structure, and a stainless steel net 11 is attached to each stage.

  A condenser plate 12 is provided at the top of the processing chamber 3. The condensate plate 12 has a triangular roof shape formed by bending a metal flat plate at the central portion. Both ends of the lowermost part of the condensate plate 12 are fixed to the inner surfaces of both sides of the casing 2 constituting the processing chamber 3, and the water vapor reaching the inner surface of the condensate plate 12 becomes water droplets as the condensate plate 12. From both ends of the casing 2 along the both side inner surfaces 2a, 2a of the housing 2, and finally returns to the water tank section 4. Therefore, it is possible to prevent the water vapor adhering to the ceiling surface of the processing chamber 3 from becoming water droplets and falling onto the cut lettuce placed on each wire net 11, and reliably performing low-temperature heating. It has become.

  The cut lettuce is placed directly on the wire mesh 11 of each stage constituting the wire mesh unit 10 from the door on the front surface of the housing 2 or placed in a mesh basket.

  The heater 5 heats the water in the water tank unit 4 to make hot water at a predetermined temperature. Then, the pump 8 sends hot water in the water tank part 4 to the injection nozzle part 9 through the lead-in pipe 6. The hot water sent to the injection nozzle unit 9 is ejected vigorously from the plurality of nozzles 9 toward the water tank unit 4, and the hot water sprayed at this time is mixed with the hot water in the water tank unit 4, thereby causing water vapor in the injection chamber 7. Will occur. The steam generated in the injection chamber 7 rises in the processing chamber 3 and reaches the uppermost condensate plate 12, but in the middle of the cut lettuce placed on each net shelf 11 in the net shelf 10. Is heated (low-temperature steam heat treatment).

  Here, a water thermometer is provided in the water tank unit 4, and a thermometer is attached to the wire mesh unit 10 in the processing chamber 2. A control unit (not shown) constantly monitors the temperature data of the water temperature meter and the thermometer, and the heater 5 so that the hot water temperature of the water tank unit 4 matches the temperature of the wire mesh unit 10 (temperature in the processing chamber) 47 to 49 ° C. And the output of the pump 8 is controlled.

  Thereby, a cut lettuce is always heat-processed with the low temperature steam of 47-49 degreeC, and a disinfection process and a browning prevention process are performed. Therefore, it is possible to obtain a cut lettuce that has a longer shelf life and a crispy texture than before and that does not impair the original taste of lettuce.

  A control unit (not shown) controls the amount of water in the pump 8, and controls the humidity in the treatment room 3 by adjusting the amount of hot water (water amount) flowing through the drawing pipe 6 and the amount of water vapor generated. Is going. This makes it possible to always provide an optimum environment for low-temperature heat treatment.

  As mentioned above, although the structure of this invention and its effect were demonstrated along the Example, embodiment of this invention is not limited to the said Example.

  For example, in the above embodiment, lettuce is illustrated as a green vegetable. However, the present invention is not limited to the above embodiment, and the same is true for other leafy vegetables such as cabbage, spinach, Chinese cabbage, and chingsai. is there.

  In the above embodiment, the case where the cut lettuce is manually placed on the net shelf 10 by opening the door of the housing 2 has been described. However, the present invention is not limited to the above embodiment. By forming a carry-in port and a discharge port on both the left and right sides of the body 2 and providing transport means such as a belt conveyor that flows from the carry-in port toward the discharge port, low temperature steam heating is performed while automatically transporting green vegetables. You may do it. Thereby, it becomes possible to heat-process a lot of green vegetables efficiently at low temperature.

  The browning prevention method for green vegetables according to the present invention and the low-temperature steam heating apparatus used therein can be used in a wider area in the field of processing green vegetables and using them as foods.

1: Low-temperature steam heating device 2: Case 2a: Both side inner surfaces 3: Processing chamber 4: Water tank 5: Heater 6: Retraction pipe 7: Injection chamber 8: Pump 9: Injection nozzle 9a: Nozzle 10: Net shelf 11: Wire mesh 12: Condensate plate

Claims (14)

  An immersion treatment step (S2-1) for immersing the green vegetables after the first washing (S1) in at least 45 to 55 ° C. hot water for 0.5 to 2 minutes, and after the immersion treatment step (S2-1) A low-temperature steam heat treatment step (S2-2) in which the green vegetables are exposed to a steam atmosphere of 40 to 50 ° C. for 18 to 22 minutes, and a method for preventing browning of the green vegetables.   The browning of the green vegetable according to claim 1, wherein the initial hot water temperature for immersing the green vegetable in the immersion treatment step (S2-1) is 51 to 53 ° C, and the hot water temperature for taking out the green vegetable is 47 to 49 ° C. Prevention method.   The method for preventing browning of green vegetables according to claim 1 or 2, wherein the immersion time for immersing the green vegetables in the immersion treatment step (S2-1) is 50 to 70 seconds. The method for preventing browning of a green vegetable according to any one of claims 1 to 3, wherein the weight ratio of the green vegetable to be immersed in the immersion treatment step (S2-1) and the hot water for immersion is 1:12 or more.   The method for preventing browning of green vegetables according to any one of claims 1 to 4, wherein the temperature of the water vapor in the low-temperature steam heat treatment step (S2-2) is 47 to 49 ° C.   The method for preventing browning of green vegetables according to any one of claims 1 to 5, wherein the treatment time of the low-temperature steam heat treatment step (S2-2) exposed to a steam atmosphere is 18 to 22 minutes. 1 Tsugiarai Kiyoshi is as washed Engineering by running water, the green vegetables according to any one of claims 1 to 6 as cleaning Engineering by hypochlorite sodium diluent is intended to include as cleaning Engineering by 及 beauty neutral detergent Browning prevention method.   A green vegetable is lettuce, The browning prevention method of the green vegetable as described in any one of Claims 1 thru | or 7. In a sealed processing chamber (3), at least a water tank part (4) for storing water, a heater (5) for heating water in the water tank part (4), and water in the water tank part (4) A pump (8) for pumping, a lead-in pipe (6) for guiding the pumped water to a position above the water tank part (4), and an end of the pipe (6) and the water tank part (4 ) And an ejection nozzle part (9) for ejecting water from the position above the water tank part (4) toward the accumulated water, and green vegetables are placed above the ejection nozzle part (9). A net shelf (10),
Water that has been heated to a predetermined temperature by the heater (5) is sprayed onto the water in the water tank (4) from the spray nozzle (9), and steam is generated in the net shelf (10). It is a low-temperature steam heating device in which the mounted green vegetables are heated ,
A low-temperature steam heating device comprising a condensate plate (12) for collecting water vapor, condensing it into water, and returning it to the water tank (4) at the ceiling in the processing chamber (3)   The pump (8) is sent from the water tank section (4) to the injection nozzle section (9) via the lead-in pipe (6), sprayed from the injection nozzle section (9), and returned to the water tank section (4) again. The low-temperature steam heating apparatus according to claim 9, wherein water is circulated along the line. The low-temperature steam heating device according to claim 9 or 10 , wherein the heater (5) is controlled so that the water temperature in the water tank section (4) matches the temperature in the processing chamber (3). The low-temperature steam heating device according to any one of claims 9 to 11 , wherein the pump (8) is controlled so as to be able to adjust an amount of water flowing in the drawing pipe (6). The processing chamber (3) has a carry-in port provided at one of the left and right ends, a carry-out port provided at the other end, and a conveying means that moves from the carry-in port toward the carry-out port, The low temperature steam heating apparatus according to any one of claims 9 to 12 , wherein the apparatus is configured to be heated while being conveyed by the conveying means. The low-temperature steam heating apparatus according to any one of claims 9 to 13 , which is intended for lettuce as a green vegetable.