AU2010237973B2 - Method of lowering moisture content of leaf vegetables and device of lowering moisture content - Google Patents

Abstract

Provided is a method of lowering the moisture content of leaf vegetables wherein a required moisture content can be attained instantaneously. A method of lowering the moisture content of leaf vegetables is characterized in that at least the hard-to-dry parts of loosened leaf vegetables are crushed, and the crushed leaf vegetables are conduction heated. Preferably, the method is done with a device equipped with parallel rollers having a gap width of 0.1-0.4 mm.

Description

1 DESCRIPTION METHOD OF LOWERING MOISTURE CONTENT OF LEAF VEGETABLES AND DEVICE FOR LOWERING MOISTURE CONTENT 5 TECHNICAL FIELD [00011 The present invention relates to a method of lowering the moisture content of leaf vegetables, which can 10 instantly lower the moisture content of leaf vegetables such as live tea leaves to a desired moisture content, and a device for lowering moisture content for carrying out the method. 15 BACKGROUND ART [0002] Green tea can be produced, for example, by steaming plucked tea leaves, rolling the steamed tea leaves while drying the steamed tea leaves, and drying the rolled tea 20 leaves, to produce Aracha tea, and subjecting this Aracha tea to a finishing process such as firing, and the like. In addition as the rolling process, various rolling processes such as tea leaf limping, rough rolling, rolling, secondary drying, refined rolling and the like need to be 25 conducted.

2 As described above, since green tea was produced through various processes as described above, it took about 3 to 4 hours to prepare Aracha tea from plucked tea leaves. [00031 5 In an attempt to reduce the production time of green tea, a device that can dry tea leaves instantly and can reduce the production time by moving tea leaves while inserting the tea leaves between a heated belt and drum has been developed (refer to Patent Documents 1 described 10 below). (0004] In addition, a device that heats and dries tea leaves between two rollers instantly to produce a powder tea, or the like has been also developed (refer to Patent Documents 15 2 and 3 described below). CITATION LIST PATENT DOCUMENTS [0005] Patent Documents 1: Japanese Patent Application Laid 20 Open (JP-A) No. H11-169076 Patent Documents 2: Japanese Patent Application Publication (JP-B) No. H5-70410 Patent Documents 3: JP-A No. H8-173038 25 DISCLOSURE OF INVENTION 3 PROBLEMS TO BE SOLVED BY THE INVENTION [0006] However, the rolling in production of a green tea is a critical process since the rolling is performed not only 5 to evaporate and dry the moisture of the tea leaves, but also to boost the flavor, and thus the flavor is adjusted by carrying out various rolling processes. The device disclosed in Patent Documents 1 described above allows the production of a green tea by instantly 10 drying tea leaves, but cannot produce a green tea having excellent flavor since the device produces the green tea without rolling. Furthermore, a rigid, thick portion of a tea such as the stem portion is hard to dry, and thus the device 15 described above has unevenly dried the tea leaves, which has harmful effects on the flavor or luster of color. In addition, the devices described in Patent Documents 2 and 3 described above and the like produce a powder tea, and instantly dry the tea leaves to a state 20 close to 0% of the moisture content. Thus, the devices described in Patent Documents 2 and 3 were not used in production of green tea. [0007] If the moisture content of live tea leaves can be 25 lowered instantly to a moisture content that is suitable 4 for rolling without unevenness, the production time of a green tea can be reduced and a green tea having an excellent flavor can be produced. Therefore, the purpose of the present invention is to provide a method of lowering moisture content of leaf vegetables, which can instantly lower the moisture content of leaf vegetables such as live tea leaves to a desired moisture content, and a device for lowering moisture content for carrying out the method. MEANS FOR SOLVING THE PROBLEMS [0008] The method of lowering moisture content of tea leaves of the present invention is characterized by pushing and crushing at least a hard-to-dry portion of unraveled tea leaves with pressing bodies, which are rollers and arranged in parallel having a gap width of about 0.1 mm to 0.4 mm and conductively heating the pushed and crushed tea leaves with a heating body at a range of 1000C to 160 0 C for 5 to 30 seconds. [0008a] In an aspect of the invention there is provided a method of lowering the moisture content of tea leaves, the method comprising the steps of: a) pushing and crushing at least a hard-to-dry portion of unraveled tea leaves with pressing bodies comprising rollers that are arranged in parallel and having a gap width of about 0.1 mm to 0.4 mm; and b) conductively heating the pushed and crushed tea leaves to a temperature in the range of about 1000C to about 1600C for about 5 to 30 seconds with at least one heating body.

4a (0009] In the method of lowering moisture content of leaf vegetables of the present invention, a hard-to-dry portion of the leaf vegetables is pushed and crushed in order to easily evaporate the moisture, and the leaf vegetables are conductively heated in order to instantly dry the leaf vegetables to a desired moisture content without unevenness. [0009b] Comprises/comprising and grammatical variations thereof when used in this specification are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof 5 BRIEF DESCRIPTION OF THE DRAWINGS [0010] FIG. 1 is a perspective view that represents one example of the device for conducting the method of lowering 5 moisture content of the present invention. FIG. 2 is a lateral view that schematically represents the operation state of the device of FIG. 1. FIG. 3 is a perspective view that represents one example of a vibration conveyor that can be used in the 10 method of lowering moisture content of the present invention. FIG. 4 is a lateral view of the vibration conveyor of FIG. 3. 15 BEST MODES FOR CARRYING OUT THE INVENTION [0011] Hereinafter, one embodiment of the method of lowering the moisture content of leaf vegetables of the present invention will be explained. However, the scope of the 20 present invention is not limited to this embodiment. [0012] The present method of lowering moisture content is characterized by pushing and crushing at least a hard-to dry portion of unraveled leaf vegetables with pressing 6 bodies, and conductively heating the pushed and crushed leaf vegetables with a heating body. [0013] As the leaf vegetables, live tea leaves, green goods 5 such as perilla, Spinacia oleracea, baby leaf, mulukhiya and kale, and the like may be used. The leaf vegetables may be previously steamed. The hard-to-dry portion of leaf vegetables represent a portion which is rigid and thick and hard to dry such as 10 the stem portion, the core portion and the like. [0014] In the present method of lowering the moisture content, first, tangled leaf vegetables are unraveled. It may be possible to unravel leaf vegetables by manual 15 operations, but a vibration conveyor is preferably used. By using a vibration conveyor, it is possible to convey leaf vegetables while automatically unraveling the leaf vegetables. At this time, the vibration of the vibration conveyor is preferably applied at 5 mm to 20 mm, preferably 20 7 mm to 15 mm of the amplitude in a longitudinal direction and at 450 to 700 times/minute. [0015] Then, at least a hard-to-dry portion of leaf vegetables are pushed and crushed with pressing bodies to a 25 degree that the leaf vegetables are not broken apart. By 7 doing this, it is possible to eliminate a hard to evaporate portion, and easily lower the moisture content. As the pressing bodies, for example, rolls in parallel or two pieces of metal plates and the like having 0.1 mm to 0.4 mm, 5 preferably 0.2 mm to 0.3 mm of the gap width may be used. {0016] Then, leaf vegetables are conductively heated by being brought into contact with a heating body. By doing this, it is possible to instantly lower the moisture 10 content. Such heating depends on the kind of leaf vegetable, but the leaf vegetables are heated at a range of 1000C to 1600C, preferably 1100C to 1500C, more preferably 1200C to 1400C for 5 to 30 seconds, preferably 10 to 20 seconds. When the leaf vegetables are live tea leaves, the 15 moisture content is preferably adjusted to 30% to 70%, particularly 40% to 60%. As the heating body, for example, heated rolls or heated metal plates and the like may be used. The moisture content of leaf vegetables may be 20 measured by the ambient-pressure dry method. [0017] In carrying out the present method of lowering the moisture content, for example, a device 1 for lowering the moisture content shown in FIG. 1 may be used to carry out 25 the present method. Hereinafter, a method of lowering the 8 moisture content of steamed tea leaves (steamed live tea leaves) 2 using the device 1 for lowering the moisture content will be explained. [0018] 5 As shown in FIG. 1 or 2, the device for lowering the moisture content 1 is a device of pushing and crushing unraveled, steamed tea leaves 2 with two rolls 3, and conductively heating the steamed tea leaves with the peripheral surfaces 31 of the rolls in order to lower 10 moisture content. [0019] This device 1 has two rolls 3 disposed in parallel, and these rolls 3 are formed with a diameter of 300 mm to 1500 mm, preferably 1000 mm to 1500 mm, and disposed in 15 parallel having a gap width of 0.1 mm to 0.4 mm, preferably 0.2 mm to 0.3 mm, and are set to inbound-rotate at I rpm to 10 rpm of the rotation number. The peripheral surfaces 31 of the rolls 3 are heated to a range of 100 0 C to 1600C, preferably 1100C to 1500C, 20 more preferably 120 0 C to 1400C by supplying vapor and the like to the inside of the rolls 3. The peripheral surfaces 31 of the roll 3 are preferably smooth surfaces which have about 0,01 pm to 4 pm of surface roughness (Ra), in order for the tea leaves 2 to 25 easily attach and uniformly dry.

9 [0020] The peripheral surfaces 31 of the rolls 3 abut onto the apex of a scraper 4 that has a sharply-formed apex as shown in FIG. 2, in order to scratch off the steamed tea 5 leaves 2 attached to the peripheral surfaces 31. [0021] In lowering the moisture amount of the steamed tea leaves 2 using the device 1, first, the steamed tea leaves 2, which are often tangled, are unraveled. In unraveling 10 the steamed tea leaves, a vibration conveyor 5 as shown in FIG. 3 or 4 is preferably used. The vibration conveyor 5 is constituted so that plural board springs 52 are obliquely installed in parallel on a trestle 51, and a conveying board 53 having a length 15 of 1 m to 10 m is fixed on the board springs, and steamed tea leaves 2 are loaded on the upper surface of the conveying board 53. On the undersurface of the conveying board 53, at one end a crank 54 is fixed as shown in FIG. 4, and a pulley 55 which is fixed on the other end of the 20 crank 54 is rotated by a motor 56 and a belt 57, in order to reciprocally move the crank 54, and by this motion of the crank and the board springs 52, vibration is applied to the conveying board 53, and thus the steamed leaves 2 loaded on the conveying board 53 are conveyed whiling being 25 unraveled. At this time, the vibration of the vibration 10 conveyor 5 is set to 5 mm to 20 mm, preferably 7 mm to 15 mm of the amplitude in a longitudinal direction and this vibration is preferably applied at 450 to 700 times/minute. In addition, plural dimples are preferably formed on 5 the upper surface of the conveying board 53 so that the steamed tea leaves 2 do not attach thereto by the moisture thereof. [0022] As described above, the unraveled, steamed tea leaves 10 2 are put into the gap of the rolls 3 from above, and as shown in FIG. 2, the hard-to-dry portions such as the stem of the steamed tea leaves 2 are pressed between the gap of the rolls 3 to be pushed and crushed. The degree of the pushing and crushing may be adjusted by changing the 15 diameter, the gap width, the rotation rate and the like of the rolls 3. The pushed and crushed steamed tea leaves 2 are discharged from below the gap, attached to the peripheral surfaces 31, and conveyed. At this time, since the steamed 20 tea leaves 2 are in direct contact with the peripheral surfaces 31, the steamed tea leaves 2 are conductively heated and the moisture is evaporated. The steamed tea leaves 2 attached to the peripheral surfaces 31 are scratched off and dropped by a scraper 4. 25 [0023] 11 At this time, the steamed tea leaves 2 are conductively heated by being brought into contact with the peripheral surfaces 31 preferably for 5 to 30 seconds, more preferably 10 to 20 seconds. This heating time may be 5 adjusted by the position of the scraper 4, the rotation rate of the rollers 3, and the like. By doing this, the moisture content of the steamed tea leaves 2 can be adjusted to 30% to 70%, preferably 40% to 60%. [0024] 10 The steamed tea leaves 2 dropped from the peripheral surface 31 are collected, and these steamed tea leaves 2 are further suitably subjected to rolling processes such as rolling, secondary drying and refined rolling, drying and the like, to produce green tea product. At the time, tea 15 leaf limping or rough rolling may be skipped, and rolling processes such as rolling, secondary drying and refined rolling may be carried out for a short time. Therefore, it is possible to produce green tea in a short time in comparison with a conventional method, and produce green 20 tea which has excellent flavor. In addition, when tea leaf limping or rough rolling is carried out, small fragments of steamed tea leaves fly, fall and accumulate on the periphery of a machine carrying out the processes. However, such things hardly happen with 25 the device 1 described above.

12 [0025] In collecting the steamed tea leaves 2 dropped from the peripheral surfaces 31, as shown in FIG. 1 or 2, the steamed tea leaves 2 may be conveyed and collected by the 5 conveyor 6. This conveyor 6 is divided into three portions, and in the center, steamed tea leaves 2 which are heated for a shorter time gather together, and on the lateral sides, appropriately heated steamed tea leaves 2 gather together. It is preferable to put back the steamed tea 10 leaves 2 which are heated for a shorter time between the gap of the rollers 3, and heat them again. EXAMPLES [0026] Hereinafter, examples of the present invention will 15 be explained. However, the present invention is not limited to the examples. [0027] <Test 1> Aracha teas 1 to 5 were prepared, and the moisture 20 content was measured, and sensory evaluations for luster of color and flavor were conducted. [0028] (Steamed tea leaves) Live tea leaves were steamed using a conveying belt 25 type steamer with zero pressure vapor for 30 seconds and 13 then these live tea leaves were blown to be cooled to room temperature to prepare steamed tea leaves. The moisture content of these steamed tea leaves was measured with ambient-pressure dry method, and the average value of five 5 time measurements was 79.6%. [0029] (Aracha tea 1) The steamed tea leaves described above were loaded and unraveled on a vibration conveyer having the same 10 configuration as the vibration conveyor shown in FIGS. 3 and 4, and the unraveled steamed tea leaves were put into the gap of rolls of a device having the same configuration as the device shown in FIG. 1, to reduce the moisture content of the steamed tea leaves. These steamed tea 15 leaves were further subjected to rolling, secondary drying and refined rolling, and then drying at 80 0 C until the core water in the steamed tea leaves (moisture in the core of leaves) came out, to prepare an Aracha tea. For the vibration conveyor used, the length of the 20 conveying board was set to 2 m, and vibration of 10 mm amplitude was applied at 600 times/minute. In addition, for the rolls of the device used, the diameter was 1000 mm, the gap width was 0.3 mm, the temperature on the peripheral surface was 120 0 C, and the rotation number was 2.2 rpm. 25 The heating time measured was about 20 seconds.

14 [00301 (Aracha tea 2) The steamed tea leaves described above were loaded and unraveled on a vibration conveyer having the same 5 configuration as the vibration conveyor shown in FIGS. 3 and 4, and the unraveled steamed tea leaves were loaded on a metal board heated to 1200C for 20 seconds, to reduce the moisture content of the steamed tea leaves. These steamed tea leaves were further subjected to rolling, secondary 10 drying and refined rolling, and then drying at 800C until the core water in the steamed tea leaves (moisture in the core of leaves) came out, to prepare an Aracha tea. For the vibration conveyor used, the length of the conveying board was set to 2 m, and vibration of 10 mm 15 amplitude was applied at 600 times/minute. [0031] (Aracha tea 3) The steamed tea leaves described above were put into the gap of the rolls of a device having the same 20 configuration as the device shown in FIG. 1 without being unraveled, to reduce the moisture content of the steamed tea leaves. These steamed tea leaves were further subjected to rolling, secondary drying and refined rolling, and then drying at 800C until the core water in the steamed 15 tea leaves (moisture in the core of leaves) came out, to prepare an Aracha tea. For the rolls of the device used, the diameter was 1000 mm, the gap width was 0.3 mm, the temperature on the 5 peripheral surface was 1200C, and the rotation number was 2.2 rpm. The heating time measured was about 20 seconds. [0032] (Aracha tea 4) The steamed tea leaves described above were loaded on 10 a metal board heated to 120 0 C for 20 seconds without being unraveled, to reduce the moisture content of the steamed tea leaves. These steamed tea leaves were subjected to rolling, secondary drying, refined rolling, and then drying at 80 0 C until the core water in the steamed tea leaves 15 (moisture in the core of leaves) came out, to prepare an Aracha tea. [0033] (Aracha tea 5) The steamed tea leaves described above were subjected 20 to tea leaf limping, and rough rolling, and further to rolling, secondary drying and refined rolling, and then drying at 80 0 C until the core water in the steamed tea leaves (moisture in the core of leaves) came out, to prepare an Aracha tea. 25 [0034] 16 (Moisture content) For Aracha teas 1 to 5, the moisture content (%) of steamed tea leaves discharged from the rolls was measured by the ambient-pressure dry method, and the average value 5 of five time measurements and the standard deviation (STD) were calculated. The results are shown in Table 1. [0035] (Evaluation for luster of color) The luster of color of Aracha teas 1 to 5 were 10 visually evaluated, and 5 step evaluations as described below were conducted wherein those of bright green color were given a "5", "Very good", and those of being reddish, darkish and stained were given a "1", "Poor". The results are shown in Table 1. 15 5: Very good 4: Good 3: Fair 2: Somewhat poor 1: Poor 20 [0036] (Evaluation for flavor) Using Aracha teas 1 to 5, 200 mL of 1000C hot water was added to 3 g of each of the Aracha teas, and the Aracha tea was extracted for 60 seconds, and evaluation for the 25 flavor was conducted by tasting the extraction liquid. 10 17 Step evaluations as described below were conducted wherein those moderately extracted having a well balance of delicious and bitter taste were given a 11101", "Very good", and those having an unusual odor such as stuffy odor and 5 those extracted insufficiently and weakly were given a "1", "Poor". The results are shown in Table 1. [0037] (Total evaluation) The total points for the luster of color and the 10 flavor were calculated, and total evaluations were conducted in which those of 12 or higher points were given "(", those of 9 to 11 points were given "o", those of 6 to 8 points were given " A ", and those of 5 or less points were given " x". The results are shown in Table 1. 15 [00381 [Table 1] Aracha Aracha tea Aracha tea Aracha tea Aracha tea tea 1 2 3 4 5 Unraveli Presence Presence Absence Absence ng Pushing and Presence Absence Presence Absence Crushing Heating 20 20 Seconds 20 Seconds 20 Seconds 30 minutes 18 time Seconds (tea leaf limping+rol ling) Avera Avera Avera Avera Avera Moisture STD STD STD STD STD ge(%) ge(%) ge(%) ge(%) ge(%) content 49.6 1.09 59.7 4.15 48.9 7.71 58.5 7.59 59.9 2.35 Luster 5 2 3 1 3 of color Flavor 9 4 6 3 8 Sum 14 6 9 4 11 Total evaluati @ A 0 x 0 on 1 [0039) (Result) Aracha tea 1 was scored well in both the luster of color and in the flavor. 5 It was found that Aracha tea 2 had a high moisture content and scored poorly in the luster of color and the flavor as a result of not pushing and crushing the steamed tea leaves, and a hard-to-dry portion remained. It was found that Aracha tea 3 had a high variation 10 of the moisture content, and was scored fairly as a result of not unraveling the steamed tea leaves.

19 It was found that Aracha tea 4 had a high moisture content and a high variation of the moisture content, and scored poorly in the luster of color and the flavor of the steamed tea leaves as a result. 5 Aracha tea 5 was relatively good in the luster of color and in the flavor, but it took a long time to be produced. [0040] <Test 2> 10 By changing the heating temperature and the heating time, changes of sensory evaluations for the luster of color and the flavor, and the moisture content were measured. [0041] 15 (Preparation of Aracha tea) Live tea leaves were steamed using a conveying belt type steamer with zero pressure vapor for 30 seconds and then these live tea leaves were blown to be cooled to room temperature to prepare steamed tea leaves. The moisture 20 content of these steamed tea leaves was measured with ambient-pressure dry method, and the average value of five time measurements was 79.6%. These steamed tea leaves were loaded and unraveled on a vibration conveyor having the same configuration as the vibration conveyor shown in FIGS. 25 3 and 4, and the unraveled steamed tea leaves were put into 20 the gap of rolls of a device having the same configuration as the device shown in FIG. 1, to reduce the moisture content of the steamed tea leaves. These steamed tea leaves were further subjected to rolling, secondary drying 5 and refined rolling, and then drying at 800C until the core water in the steamed tea leaves (moisture in the core of leaves) came out, to prepare an Aracha tea. For the vibration conveyor used, the length of the conveying board was set to 2 m, and vibration of 10 mm 10 amplitude was applied at 600 times/minute. In addition, for the rolls of the device used, the diameter was 1000 mm, the gap width was 0.3 mm, the temperatures of the peripheral surface was set to those shown in Table 2 or 3 below, and the heating times were adjusted to those shown 15 in Table 2 or Table 3 below by adjustment of the rotation number. [0042] (Evaluation) For the Aracha teas prepared, sensory evaluations for 20 the luster of color and the flavor, and total evaluations were conducted in the same manner as those of Test 1. In addition, the moisture content (%) of steamed tea leaves discharged from the rolls was measured. The results are shown in Table 2 or Table 3. 25 [0043] 21 [Table 2] 1000 100* 120* 130* 140* 150* 1600 1650 950 C C C C C C C C C Luster of 1 1 1 1 2 1 1 1 1 color 3 Flavor 1 2 3 3 3 3 3 2 1 Seconds Sum 2 3 4 4 5 4 4 3 2 Total x x x x x x x x x evaluation Luster of 1 2 2 2 2 2 2 3 color 5 Flavor 2 4 7 7 7 7 6 5 2 Seconds Sum 3 6 9 9 9 9 8 8 3 Total x o o o o x evaluation Luster of 1 2 3 5 5 4 3 2 1 color 10 Flavor 2 5 6 9 8 8 5 4 2 Seconds Sum 3 7 9 14 13 12 8 6 3 Total evaluation 20 Luster of 2 2 4 5 5 5 3 2 1 Seconds color Flavor 2 6 6 9 8 7 5 4 1.

22 Sum 4 8 10 14 13 12 6 6 2 Total x AL 0 @ @ @ o A evaluation Luster of 2 3 4 4 3 3 3 2 1. color 30 Flavor 2 5 7 7 7 6 5 4 1 Seconds Sum 4 8 11 11 10 9 8 6 2 Total A o o A A x evaluation Luster of 1 1 1 1 1 1 1 1 ~1 color 40 Flavor 3 4 4 3 2 1 1 1 1 Seconds Sum 4 5 5 4 3 2 2 2 2 Total x x x x x x x x x evaluation [0044] [Table 3] 950C 100 0 C 110 0 C 1200C 130 0 C 140 0 C 150 0 C 1600C 165 0 C 3 Seconds 78.4 72.8 70.6 70.1 69.2 65.7 51.3 40.5 35.8 5 Seconds 76.2 69.4 67.5 65.2 63.1 52.4 41.6 35.5 29.4 10 Seconds 73.3 58.5 54.9 50.5 46.3 41.4 36.4 31.6 26.8 20 Seconds 72.8 57.3 51.2 46.6 41.2 37.5 33.8 28.5 23.1 30 Seconds 71.4 51.4 45.1 41.2 35.8 33.5 33.1 24.9 18.6 40 Seconds 70.9 42.8 37.4 26.7 18.4 16.3 14.1 12.4 10.7 23 [0045] (Result) It was found that the Aracha tea obtained by heating the steamed tea leaves at a range of 100 0 C to 160 0 C for 5 5 to 30 seconds had excellent luster of color and flavor. EXPLANATION OF LETTERS AND NUMERALS [0046] 1 Dry device 2 Steamed tea leaves 10 3 Roll 31 Peripheral surface 4 Scraper 5 vibration conveyor 6 Conveyor

Claims (3)

1. A method of lowering the moisture content of tea leaves, the method comprising the steps of: a) pushing and crushing at least a hard-to-dry portion of unraveled tea leaves with pressing bodies comprising rollers that are arranged in parallel and having a gap width between the rollers of about 0.1 mm to 0.4 mm; and b) conductively heating the pushed and crushed tea leaves to a temperature in the range of about 100 0 C to about 1600C for about 5 to 30 seconds with, at least one heating body.

2. The method of lowering the moisture content of tea leaves according to claim 1, wherein the tea leaves are unraveled using a vibration conveyor.

3. The method of lowering a moisture content of tea leaves according to claim 1 or 2, wherein the at least one heating body is located on the peripheral surface of the rollers. ITO EN, LTD. WATERMARK PATENT AND TRADE MARKS ATTORNEYS P35277AU00