JPH0218044B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing instant black tea, and more particularly to a method for producing instant black tea having a porous structure by extracting water-soluble substances from black tea and freeze-drying the extracted water-soluble substances. Conventionally, hot water was poured into black tea to extract it, and the extract was dried by spray drying, drum drying, freeze drying, etc., and powdered to obtain instant black tea. However, even if the instant black tea was reconstituted by pouring hot water, the result was a black tea beverage with poor flavor. In addition, since the instant black tea obtained as described above has a very large apparent specific gravity,
When reconstituted into a tea drink using a spoonful,
It will not give you the flavor equivalent to a bowl of black tea, but half a spoon will give you the flavor equivalent to a bowl of black tea. Therefore, it is difficult to measure accurately in general households. Furthermore, a large amount of proteins, caffeine, and tannins contained in the tea leaves are transferred to the extract obtained by extracting black tea with hot water, so when the extract is cooled, so-called cream down is produced. The tea becomes cloudy and precipitates, resulting in uneven quality of the final instant tea product. Moreover, when the final product is reconstituted with hot water, it has a strong astringent taste, which is undesirable. JP-A-47-7777 discloses that an aqueous extract of tea or coffee containing at least 30% solids by weight is added to the extract until ice crystals form in the extract.
cooling to a temperature between 5°C and its freezing point and subjecting the cooled extract to a vacuum of not more than 500 microns;
A method is disclosed whereby the extract is expanded, frozen, the frozen extract is ground, and lyophilized. However, in this method, the frozen extract is pulverized without being thawed, so it is necessary to use a pulverizer equipped with refrigeration equipment, resulting in a large amount of equipment. Furthermore, after freezing and crushing,
The final freeze-dried porous structure product contains polysaccharides,
Since there are few skeletons such as sugars, there is a tendency for the product to lose its shape during filling into packaging containers or during transportation. As a result of intensive research in order to overcome the above-mentioned defects, the present inventors soaked black tea in water and centrifuged it to obtain an extract with a concentration of Bx4 to Bx6. 12 After concentration under reduced pressure, dextrin with a DE of about 7 to 20 is added and dissolved to bring the Bx to about 20 to 30, then lyophilized and coarsely crushed to 3.5 to 30 mesh (Japanese Industrial Standards).The final product is obtained by It has been found that it has excellent shape retention, and that when a spoonful of it is reconstituted with hot or cold water, the flavor is equivalent to that of a bowl of black tea. Also,
The reconstituted black tea beverage was found to be comparable in color tone and flavor to black tea beverages prepared from regular tea bags. The present invention was completed based on this knowledge. The black tea used in the present invention is not particularly limited, and examples thereof include fermented and dried black tea from India, Sri Lanka, Indonesia, Pakistan, Kenya, Malawi, etc., and these can be used alone or in combination. It can be used. To soak black tea in water, soak black tea in water at a temperature of 20 to 32℃ for 12 to 30 minutes.
This is done by soaking for 48 hours. Immersion temperature is 32
If the temperature exceeds ℃, proteins, caffeine, tannins, etc. are extracted from the tea leaves more than necessary, and when the final product, instant black tea, is reconstituted with water, cream down is produced, and cloudiness or precipitates occur. Moreover, it gives an astringent taste, which is undesirable. Also, 20
If the temperature is less than 0.degree. C., the extraction will take longer than necessary, and the flavor of the extract may change during the extraction. If the tea leaves are immersed in water for less than 12 hours, the extraction concentration will be as described below.
Bx4 cannot be achieved, and the subsequent steps of vacuum concentration and freeze-drying require more time than necessary, making it uneconomical, and the flavor of the reconstituted black tea beverage compared to the final product, instant black tea, is bitter and tasteless. In addition, even if tea leaves are soaked in water for more than 48 hours, the concentration of the extract will not increase significantly, and the flavor may deteriorate.In addition, in the summer, the surface of the extract may become moldy or ferment, causing deterioration. There is a risk that The extraction concentration of black tea is measured using a hand-held refractometer.
Bx4 to 6 is appropriate. If the concentration is less than about Bx4, as mentioned above, the subsequent steps of vacuum concentration and freeze-drying will take longer than necessary, making it uneconomical.
Moreover, when concentrating under reduced pressure, the aroma of the low boiling point part undergoes a type of steam distillation under reduced pressure for a long time and dissipates into the atmosphere as an azeotrope. The flavor of the food becomes lighter and it becomes less delicious. Additionally, in order to obtain an extract with a concentration exceeding Bx6 using a hand-held refractometer, the steeping temperature of black tea must exceed 32°C, which results in extraction of proteins, caffein, tannins, etc. in excess of what is necessary. As a result, when the extract is cooled, creaminess occurs, and when the extract is drunk, it has an unpleasant astringent taste, which is undesirable. In addition, during the subsequent freeze-drying process, the product is pre-frozen and then partially thawed during transport into the freeze-dryer, foams when the pressure is reduced, and the apparent specific gravity becomes smaller than the expected value. Next, the tea leaf steeping liquid obtained above is passed through a centrifugal sedimentation machine.
The tea leaves and the extract are separated using a centrifugal dehydrator, centrifuge, etc. The extracted liquid after fractionation is concentrated under reduced pressure using a vacuum concentrator such as a stationary type or a rotary type at a temperature of about 120 Torr or less and a temperature of about 55°C or less. 55℃
Vacuum concentration at temperatures that exceed this level will cause the aroma of the low boiling point to dissipate through a type of steam distillation, making the final product, the tea beverage obtained from the instant black tea, less delicious. Concentration at a reduced pressure of more than about 120 torr is undesirable because it requires a longer concentration time than necessary and aroma components, saccharides, proteins, etc. may be denatured during concentration. This vacuum concentration process reduces the processing time to a single hour as much as possible in the subsequent freeze-drying process.
and is necessary to obtain the desired apparent specific gravity in the final product. Concentration under reduced pressure is performed so that the value measured with a hand-held refractometer is approximately Bx7-12. If it is less than about Bx7, the subsequent freeze-drying takes more time than necessary, which is energy-uneconomical, and the cavities in the porous structure of the final product, the instant black tea, are too large and the apparent specific gravity after coarse crushing is It becomes small. Therefore, when a spoonful of the product is reconstituted into a black tea beverage, it does not become as strong as a bowlful of black tea, but only after about 8 minutes. In addition, if it exceeds about Bx12, aroma components will be lost due to excessive heating during concentration, foaming will occur during vacuum concentration, making concentration processing difficult, and complete freezing will occur when pre-freezing with dextrin added. In addition, the frozen product partially thaws during transportation to the freeze-drying equipment after freezing or during depressurization, resulting in foaming during freeze-drying, reducing the yield, and staining the shelves and inner walls of the freeze-drying machine. The apparent specific gravity of the freeze-dried product before coarse crushing is not uniform. Next, add dextrin to the above Bx7-12 concentrate, dissolve and mix, and final Bx before pre-freezing.
to about 20 to 30. Adding dextrin is necessary to adjust the apparent specific gravity of the final product, and is different from the method of forcibly mixing air bubbles into the concentrate to adjust the apparent specific gravity of the final product. Moreover, the dextrin forms the skeleton of the final product, thereby preventing the product from deforming during filling operations into packaging containers or during transportation to remote locations. The dextrin to be added has a DE (reducing sugar measured and expressed as glucose, calculated as a percentage of the solid content) of about 7 to 20. this
Dextrin with a DE of about 7 to 20 is added to the concentrate to give a Bx of about 20 to 30. When it exceeds about Bx30,
Temperatures lower than necessary for prefreezing, e.g. -45°C
It requires an even lower temperature and requires larger refrigeration equipment, making it uneconomical. Moreover, even if such a concentrated liquid is frozen, it will partially melt and foam during transport to the freeze dryer or during the depressurization operation, reducing the yield. Furthermore, it will not only stain the shelves and inner walls of the freeze dryer, but also cause roughness. The apparent specific gravity of the freeze-dried product before crushing is not uniform, and when the particle size distribution of the final product after crushing treatment is measured, a large amount of fine powder is mixed in, which is undesirable. Also,
If it is less than about Bx20, freeze-drying takes more time than necessary and is uneconomical in terms of energy, and the cavities in the porous structure of the freeze-dried product before coarse crushing become large, resulting in a particle size distribution after coarse crushing. In this case, a large amount of fine powder is mixed in, which is undesirable. Furthermore, if a dextrin with a DE of less than about 7 is used, its solubility in water is poor, and when the above-mentioned dextrin is added to a concentrated solution treated under reduced pressure to achieve a Bx of about 30, a portion of the dextrin is difficult to dissolve, and the final product is reconstituted with water. When preparing a black tea beverage, the dextrin is difficult to completely dissolve. on the other hand,
Dextrin with a DE of more than about 20 is hygroscopic and adheres to the inner wall of the mortar or the circumferential surface of the roll during the crushing process in a mortar, oni roll, etc., resulting in poor yield and poor workability. Certain instant teas tend to absorb moisture. Therefore, in order to package such products, it is necessary to use a packaging machine equipped with a dehumidifying device and to select packaging materials with low or no moisture permeability, which increases the cost of packaging materials. Pour the concentrate with a Bx of 20 to 30 obtained above into a shallow tray to a thickness of 1 to 5 cm, and quickly pre-freeze it at about -20 to -40°C to obtain fine ice crystals. If the thickness of the poured concentrate exceeds about 5 cm, it will be too thick and require a long time to prefreeze and freeze dry. On the other hand, if the thickness is less than about 1 cm,
Since the number of trays used increases, the usable space becomes large, which is not economical. Pre-freezing temperature is -20℃
If the temperature is higher than about -40°C, it will take time to complete freezing, and freezing equipment will be too large to obtain a temperature lower than about -40°C, which is not economical. Next, the frozen product that has been pre-frozen is immediately carried into a freeze dryer and freeze-dried, and the freeze-drying is completed when the temperature is maintained at about 0.5 torr or less. If freeze-drying is terminated when the temperature exceeds about 0.5 torr, drying will not be sufficient and the water content will be high, making subsequent crushing difficult. Next, the freeze-dried product is roughly crushed using a mortar, Oni Roll, etc., and sieved within the range of 3.5 to 30 mesh according to Japanese Industrial Standards, with an apparent specific gravity of 0.21 to 0.26 g/
Obtain cc of coarsely ground instant black tea. If the sieve exceeds the above sieve range, the final product may be bottled or
Due to vibrations caused by transportation after being filled into a container such as a bag, the final product is classified inside the container into coarse products at the top and fine products at the bottom, which is inconvenient. It becomes easy to deviate from the expected apparent specific gravity, that is, the range of 0.21 to 0.26 g/cc. Instant black tea with an apparent specific gravity of 0.21 to 0.26 g/cc within the range of 3.5 to 30 mesh as described above has the same deliciousness as conventional regular tea bags, and can be prepared by spray drying, drum drying, etc. It tastes much better than what I got. Furthermore, since the product of the present invention has an apparent specific gravity of 0.21 to 0.26 g/cc, a spoonful of the reconstituted black tea beverage corresponds to the strength of a bowl of black tea, making it an extremely easy-to-measure product for ordinary households. . Next, the present invention will be explained in detail with reference to examples. Example 1 500 g of black tea from Sri Lanka and 500 g of black tea from Kenya were mixed, 5 kg of water at 32°C was added, and the mixture was soaked for 12 hours while maintaining the temperature. Next, the tea leaves were separated by centrifugal dehydration using a basket-type centrifugal dehydrator with a diameter of 610 mm at 1600 rpm for 30 minutes to obtain 4.5 kg of extract. The Bx of this extract was measured with a hand-held refractometer and was found to be 6. 100 until the extract obtained above reaches Bx12.
The mixture was concentrated under reduced pressure at 50° C. to obtain 2.25 kg of a concentrated solution. To this concentrated solution, 0.61 kg of DE8 standard NSD238 (trade name), which is a dextrin manufactured by Nippon Shiso Kogyo Co., Ltd., was added to obtain a solution of Bx30. The solution was poured into a shallow tray to a thickness of 5 cm and pre-frozen at -40°C. This was carried into a DF-05 special freeze dryer manufactured by Japan Vacuum Technology Co., Ltd., and freeze-dried at 0.6 to 0.3 torr, and finished at 0.3 torr. After freeze-drying, coarsely crush in a mortar to 3.5 to 30 mesh (Japanese Industrial Standards sieve)
It was sieved within the range of . Product moisture was 2.5% by weight. The apparent specific gravity of the obtained product was 0.21 g/cc,
A spoonful (2.3 g) of this tea was enough to prepare a tea bowl (170 c.c.), and the flavor was also evaluated as satisfactory as described below. A panel of 30 experts conducted a taste preference survey using a two-point preference test method on the black tea beverages reconstituted with boiling water as described above and the black tea beverages prepared from commercially available teabags. As a result, 15 people said that the product of this example was good, and 15 people said that the commercially available product was good, and there was no significant difference in the risk rate of 5%. Example 2 9 kg of water at 20° C. was added to 2 kg of Indian black tea, and the mixture was soaked for 48 hours while maintaining the temperature. Next, centrifugal dehydration was performed in the same manner as in Example 1 to obtain 8 kg of extract.
The Bx of this extract was measured using a hand-held refractometer and was found to be 4. 90 torr until the extract obtained above reaches Bx7, 45
It was concentrated under reduced pressure at °C to obtain 4.57 kg of concentrated liquid. Add dextrin manufactured by Matsutani Chemical Industry Co., Ltd. to this concentrated solution to DE18~
A Bx21 solution was obtained by adding 0.8 kg of 20 standard Pine Index No. 4 (trade name). The solution was poured into a shallow tray to a thickness of 2 cm, and the tray was pre-frozen at -30°C. Next, it was carried into a TFD-10LF ₅ type freeze dryer manufactured by Toyo Giken Co., Ltd., and freeze-dried at 0.6 to 0.3 torr, and was finished while maintaining the temperature at 0.3 torr. After freeze-drying, it was crushed using an ice crusher model IC-1 manufactured by Hosokawa Iron Works Co., Ltd. in the same manner as in Example 1 to obtain a product within the range of 3.5 to 30 meshes. This product had a moisture content of 2.8% by weight. This product had an apparent specific gravity of 0.26 g/cc, and one spoonful (2.5 g) of the product produced a bowlful (170 c.c.) of black tea beverage. As a result of conducting the same taste preference survey as in Example 1 regarding this product and commercially available T-bags, there was a significant difference at a risk rate of 5% between 13 people who preferred this product and 17 who preferred the commercial product. I was bored. Example 3 2.5 kg of water at 25° C. was added to 0.5 kg of Sri Lankan black tea, and the mixture was immersed while being maintained at that temperature for 24 hours. This immersion liquid was centrifugally dehydrated in the same manner as in Example 1, and the extract was
Obtained 2.25Kg. When this extract was measured with a hand-held refractometer, Bx was 5. 100 torr until the extract obtained above reaches Bx8,
It was concentrated under reduced pressure at 48°C to obtain 1.40 kg of concentrated liquid. Add dextrin manufactured by Matsutani Chemical Industry Co., Ltd. to this concentrated solution to DE7~
0.25kg of 8 standard Pinedex No. 1 (product name)
In addition, I made it Bx22. Next, the liquid was poured into a shallow tray to a thickness of 3 cm. After preliminarily freezing the tray at -35°C, it was carried into a freeze dryer model RL-50MB manufactured by Kyowa Shinku Gijutsu Co., Ltd. and freeze-dried at 0.6 to 0.1 torr. This was finished while maintaining a pressure of 0.1 Torr, and then coarsely crushed in the same manner as in Example 2 to obtain a product of 3.5 to 30 mesh. The apparent specific gravity of this product was 0.24 g/cc, and one spoonful (2.5 g) of the product yielded a black tea beverage equivalent to one bowl of black tea (170 c.c.). As a result of conducting the same taste preference survey as in Example 1 regarding this product and commercially available T-bags, there was a significant difference at a risk rate of 5% between 14 people who preferred this product and 16 who preferred the commercial product. I was bored. Test Example 1 The particle size distribution of the final products obtained in Examples 1, 2, and 3 was measured, and the results are shown in Table 1.

[Front] Yuon
Test Example 2 The temperature of the tea steeping liquid was maintained at 35°C, and the following Example 1
2.3 g of the final product obtained in the same manner as above was taken, dissolved in 170 c.c. of boiling water, placed in a transparent glass cup, and cooled to 10°C in a refrigerator. On the other hand, the black tea beverage obtained in Example 1 was also placed in a transparent glass cup and cooled to 10° C. in the refrigerator as described above. Appearance testing of both samples by a panel of 30 experts showed that black tea beverages prepared from the final product obtained from steeping liquid at 35°C formed a precipitate at the bottom of the transparent glass cup when cooled. There were 25 people who recognized that there was a problem with the appearance. On the other hand, the black tea beverage obtained by the method of Example 1 was good with no precipitation observed even after cooling. This is a 1% risk rate.
This shows that it is significant. Test Example 3 DE25 manufactured by Sanmatsu Kogyo Co., Ltd. was added to the concentrated liquid after vacuum concentration.
Add SLD-25 and treat in the same manner as in Example 2,
Obtained the final product. In the crushing process of this product, similar to Example 2, the product was crushed using an ice crusher model IC-1 manufactured by Hosokawa Iron Works Co., Ltd., and the yield at that time was determined. compared with yield. The results are shown in Table 2. Table 2 Example 2 Test Example 3 Yield 99% by weight 90% by weight In addition, as a result of disassembling the crusher that processed the product of Test Example 3, it was found that a large amount of instant black tea had absorbed moisture and adhered to the surface of the demon roll. Ta. Test Example 4 A black tea beverage obtained by the method of Example 3 and a commercially available tea bag were immersed in 170 c.c. boiling water for 3 minutes and then taken out. The color was measured using a model ND-101D (manufactured by Co., Ltd.). The results are shown in Table 3. In the table, the larger the value of L (lightness), the brighter the color, the larger the value of a (hue), the more reddish the color, and the larger the value of b (color), the more yellowish the color.

[Table] Both samples were poured in the same volume into a white tea bowl of the same volume, and a panel of 30 experts conducted a two-point preference test regarding color tone. As a result, 16 people preferred the commercially available product, and 14 people preferred the commercial product. The product of Example 3 was preferred. Therefore, no significant difference between the two samples was observed at a risk of 1%. Test Example 5 1 kg of Sri Lankan black tea was soaked in water and treated in the same manner as in Example 3 using an extract with a value of Bx3 measured by a hand-held refractometer to obtain instant black tea. Black tea beverages were prepared using this instant black tea and the instant black tea obtained in Example 3 in the same manner as in Example 3, and a two-point preference test was conducted by a panel of 30 experts. The preference of people for the black tea beverage obtained according to Example 3 was significant at a risk rate of 5%. In addition, the reason why they preferred the black tea beverage obtained over the instant black tea of Example 3 was that the product of Example 3 had a better aroma. As is clear from the attached gas chromatogram, the above results are in the low boiling point region of the gas chromatogram (Figure 1) obtained from the black tea beverage of Example 3 (the boiling point increases toward the right from arrow A). The amount of is Bx3
This is also supported by the fact that the amount is higher than that in the low boiling point region of the gas chromatogram (Figure 2) obtained from instant black tea prepared from the steeping liquid. The above gas chromatogram can be obtained by the following method. A heat-resistant glass tube with an inner diameter of 3 mm and a length of 17 cm is filled with a weakly polar polymer bead filler based on 2,6-diphenyl-para-phenylene oxide (manufactured by AKZO Research Labs., trade name: Tenax GC). Make a sample collection tube,
Next, dissolve 5 g of instant black tea in 168 g of hot water and place it in the constant temperature sample storage bottle 1 shown in Fig. 3, and pass nitrogen gas from the nitrogen gas cylinder 2 into the sample storage bottle 1 at a constant flow rate to fill the volatile substance. The sample is introduced into a sample collection tube 4 filled with the agent 3 and collected. Next, after attaching a syringe needle 5 to the tip of the sample collection tube 4, a carrier gas conduit 6 is connected, and the sample collection tube 4 is then placed in a heating furnace 7.
(heating introduction device FLS-3 type of gas chromatograph odor analysis additional device manufactured by Shimadzu Corporation) and inserted into the sample vaporization chamber 8 of the gas chromatograph. Filler 3 for collecting sample volatile substances by heating heating furnace 7
After more volatile substances are removed, a carrier gas is flown to introduce the volatile substances into the sample vaporization chamber 8 of the gas chromatograph and perform a gas chromatogram. The gas chromatograph used is an Okura gas chromatograph MDEL-701, the detector is a hydrogen flame ionization type, the carrier gas is nitrogen gas, and the column is a Silicon OV-101 (Ohio
A silica capillary column coated with silica (manufactured by Valley, Inc.) is used, and the column temperature is raised from 50°C to 180°C at a rate of 2°C/min. Test Example 6 1 kg of Sri Lankan black tea was soaked in water and treated in the same manner as in Example 3 using an extract with a value measured by a hand-held refractometer of Bx8 to obtain instant black tea. Using this instant black tea and the instant black tea obtained in Example 3, black tea beverages were prepared in the same manner as in Example 3, respectively. 2 by a panel of 30 experts on this tea beverage.
As a result of a point preference test, 24 people preferred the black tea beverage obtained in Example 3, which was significant at a risk rate of 5%. Also, the reason why I preferred the instant black tea in Example 3 was
The black tea beverage obtained from the Bx8 extract was evaluated as having a slightly astringent taste and lacking in aroma. This evaluation is evident from the gas chromatograms processed in the same manner as in Test Example 5, as shown in Figure 1 obtained from the black tea beverage of Example 3 and Figure 5 obtained from the black tea beverage prepared from the extract of Bx8. The area ratio of is 1:
0.85, which is also supported by the fact that the black tea beverage of Example 3 has more volatile components.

[Brief explanation of drawings]

Figure 1 is a gas chromatogram of instant black tea obtained from a black tea extract with an extraction concentration of Bx5, and Figure 2 is the above.
Gas chromatogram of instant black tea obtained from Bx3 extract, Figure 3 is a vertical cross-sectional view of the sample collection device, Figure 4 is a vertical cross-sectional view of the sample vaporizer, Figure 5 is a black tea extract with an extraction concentration of Bx8. This is a gas chromatogram of instant black tea obtained from 1...Sample storage bottle, 2...Nitrogen gas cylinder, 3
... filler, 4 ... sample collection tube, 5 ... syringe needle,
6...Carrier gas conduit, 7...Heating furnace, 8...
Sample vaporization chamber.

Claims (1)

[Claims] 1. Extract concentration obtained by soaking black tea in water and centrifuging it
Bx4-6 extract at a temperature below 55℃
After concentrating under reduced pressure to about Bx7 to 12, add and dissolve dextrin with DE7 to about 20 to make Bx about 20 to 30,
A method for producing instant black tea, which is then freeze-dried. 2. The method according to claim 1, wherein the tea is immersed in water at a temperature of about 20 to 32°C. 3. The method according to claim 1, wherein the freeze-drying is followed by coarse crushing using a crusher.