EA041335B1 - METHOD FOR OBTAINING PRODUCTS FROM BLACK TEA - Google Patents

Description

Technical field

The present invention relates to a method for preparing black tea products, in particular to a method for producing black tea extracts.

State of the art

Tea has been consumed as a beverage for over 2,000 years and, with the exception of water, is the most popular beverage consumed by humans. The tea is very refreshing, can be served hot or cold, and has been commercially available for many years.

Packaged ready-to-drink (RTD) tea beverages such as iced tea are popular with consumers (eg as an alternative to carbonated soft drinks). These drinks are usually made from tea extracts. Unfortunately, such beverages often form haze and/or sediment upon storage, making their appearance less attractive. The formation of haze in RTD beverages not only affects the appearance of the product, giving the impression that the beverage has gone bad, but also accelerates the loss of both flavor and color.

For fruit-flavored RTD beverages, acidification is necessary to produce formulations with the desired flavor balance. Acidification may also be beneficial in improving the microbiological stability of RTD tea beverages. Unfortunately, precipitation of solids from such acidified beverages is particularly noticeable and can occur after storage periods ranging from one week to 6-12 weeks.

Thus, the present inventors have recognized that there is still a need to produce beverages containing tea polyphenols that have good organoleptic properties and do not suffer from the disadvantages of haze and/or settling.

Brief description of the invention

The present invention relates to a method for producing a black tea extract, comprising extracting black leaf tea particles with an acidic solution at a temperature of less than 35°C, wherein the black leaf tea particles have a particle size of less than 250 μm.

The present invention relates to a low temperature extraction process for black leaf tea (sometimes referred to as cold brewing). Without wishing to be bound by any theory, the present inventors believe that the use of a relatively low extraction temperature improves the organoleptic properties of the black tea extract, especially in terms of imparting an authentic tea flavor and aroma to the extract. It is also contemplated that the process will require less energy than conventional methods in which the extraction solvent is heated to a relatively high temperature (typically about 90°C).

In order to achieve the desired extraction efficiency at such low temperatures, the particle size of the leaf tea particles is controlled so that the particle size of the leaf tea is less than 250 µm.

The present inventors have surprisingly found that extracting leaf tea in an acidic solution produces a tea extract that has less haze than a method in which leaf tea is extracted under neutral conditions and then acidified. This effect is more pronounced for black leaf tea with a small particle size.

Black tea extract can be used to prepare a ready-to-drink beverage (RTD). Because such RTDs are typically acidified, the present method does not require the addition of any ingredients that are not normally present in the final product. In this way, a tea extract having less haze can be obtained without the need for any additional ingredients other than those normally present in the final product based on such extracts.

Detailed description of the invention

The present invention relates to a method in which black leaf tea particles are extracted at low temperature under acidic conditions to obtain a black tea extract. More specifically, the invention relates to a method for producing a black tea extract, comprising extracting black leaf tea particles with an acidic solution at a temperature of less than 35°C, wherein the black leaf tea particles have a particle size of less than 250 μm.

As used herein, the term leaf tea refers to leaf and/or stem material from Camellia sinensis van sinensis and/or Camellia sinensis van assamica in unbrewed form (ie, material that has not been subjected to a solvent extraction step). The so-called black leaf tea essentially refers to fermented leaf tea. For example, black leaf tea is usually obtained by harvesting the leaves of the Camellia sinensis plant and withering, maceration, enzymatic oxidation (fermentation), heat treatment and sorting. Black leaf tea is commonly sold at tea auctions.

The black leaf tea particles used in the present method have a particle size (ie, largest diameter) of less than 250 µm, preferably less than 200 µm, more preferably less than 150 µm, and most preferably less than 100 µm. Although there is no particular restriction on the lower limit of the particle size range, the black leaf tea particles preferably have a particle size of

- 1 041335 more than 5 microns, more preferably more than 10 microns, even more preferably more than 20 microns.

If a particle size is specified, then at least 85% by weight of the leaf tea starting material has this particle size, more preferably at least 90% by weight, even more preferably at least 95% by weight, and most preferably at least 99% by weight. .%. The weight percentage of particles having a particular particle size can be determined by sorting into fractions by particle size (eg, sieving) and then weighing the fractions. When determining particle size, the leaf tea particles are in dried form and have a moisture content of less than 30% by weight (typically 1 to 10% by weight).

Leaf tea contains material with different particle sizes obtained from a conventional manufacturing process. Indeed, loose leaf tea is usually sorted into different grades (eg, whole leaf, cut leaf, seed, and dust) before being sold at auction. One way to sort tea is by particle size sorting. For example, loose leaf tea can be passed through a series of vibrating screens where different varieties are held and collected. In this way, leaf tea particles having a size of less than 250 µm can be separated. For example, particles that passed through a Tyler sieve with a mesh size of 60 mesh (250 microns) would have the appropriate particle size.

While it is possible to obtain black leaf tea particles from commercially available black leaf tea by sifting (as described above), this is not very efficient since only a small portion of the leaf tea will be of a suitable size. Thus, the method preferably includes the step of pulverizing black leaf to obtain black leaf tea particles to increase the proportion of leaf tea having an appropriate particle size. For example, leaf tea can be ground using impact mills, hammer mills, ball mills, jet mills, cone mills, roller mills, stone mills, and the like. The ground leaf tea can optionally be passed through a series of vibrating sieves as described above to select fractions having a certain particle size.

Without wishing to be bound by any theory, the present inventors believe that leaf tea particles having a particle size of more than 250 µm have a negative effect on extraction efficiency due to the fact that they have a lower surface area to volume ratio compared to smaller leaf tea particles. tea. Since leaf tea particles larger than 250 µm are easily removed after grinding and/or sifting, only a small amount of particles of this size can be ensured. Preferably, the amount of leaf tea particles having a particle size greater than 250 µm is less than 15 wt.%, more preferably less than 10 wt.%, even more preferably less than 5 wt.%, and most preferably less than 1 wt.%.

Particles of black leaf tea are extracted with an acidic solution. Extraction of black leaf tea particles with an acidic solution provides a black tea extract with low turbidity. It has been noted that adding an equivalent amount of acid to the tea extract (i.e. acidification after extraction) does not have the same effect. Indeed, post-extraction acidification actually increases the level of turbidity in the tea extract.

The acid solution preferably contains an organic acid such as citric acid, malic acid, tartaric acid, ascorbic acid. The acid solution may contain a mixture of two or more of these organic acids. Typically, the acid concentration in the acid solution will be 0.01 to 2% by weight, more preferably 0.05 to 1.5% by weight, even more preferably 0.1 to 1% by weight. The pH range of the acid solution is not fundamentally important. However, it is usually between 2 and 3.5 and preferably between 2 and 3. Unless otherwise stated, the pH is measured at 20°C.

The black tea extract obtained by this method may have a different pH from the extracting solvent. Without wishing to be bound by any theory, it is believed that the extractable solids have a buffering effect and thus the pH of the extract is generally higher than the pH of the extracting solvent. Preferably, the black tea extract has a pH (at 20°C) of less than 5, more preferably 2.5 to 4.5, even more preferably 2.5 to 4.

The black tea extract can be used to make a ready to drink (RTD) drink, so it is preferred that the acid solution contains a food grade acid. The acidic solution preferably contains citric acid, since this acid is commonly used as an acidifier in RTD beverages. In order to obtain a particularly well balanced taste RTD drink formulation from black tea extract, the acidic solution preferably contains citric acid and additionally contains malic acid and/or ascorbic acid.

Particles of black leaf tea are extracted at a temperature of less than 35°C. Without wishing to be bound by any theory, it is believed that the use of a relatively low extraction temperature improves the organoleptic properties of the black tea extract, especially in terms of imparting an authentic tea flavor and aroma to the extract. It is also contemplated that the process will require less energy than conventional methods in which the extraction solvent is heated to a relatively high temperature (typically about 90°C). The extraction temperature is preferably 10 to 30°C, more preferably 15 to 25°C.

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There are no particular restrictions on the duration of the extraction step. However, a relatively short extraction time is preferred. For example, black leaf tea particles are preferably extracted with the acidic solution for less than 20 minutes, more preferably less than 10 minutes. One skilled in the art will appreciate that a particular minimum extraction time is necessary to allow the tea solids to be recovered from the loose leaf tea particles. Thus, the extraction time is preferably at least 1 minute, more preferably at least 2 minutes.

The method preferably includes an additional and subsequent step of separating black leaf tea particles from the tea extract. This can be achieved by passing the tea extract through a filter. The filter will have the appropriate pore size to remove black leaf tea particles. For example, a 0.45 µm PES filter can be used. Because the black leaf tea particles tend to swell during extraction, the pore size of the filter should not be as small as the smallest leaf tea particles used as process feedstock.

The acid solution may contain additional ingredients. For example, the acid solution may contain common RTD beverage ingredients such as sweeteners, flavors, preservatives, and the like. Alternatively, these ingredients may be added to the black tea extract after extraction.

Although the black leaf tea particles need to be extracted with the acid solution, it is not necessary to prepare the acid solution and the black leaf tea particles separately. For example, it is contemplated that black leaf tea particles and acid may be mixed as dry ingredients followed by the addition of a solvent (usually water). This would be advantageous as it would allow the dry ingredient mixture to be prepared in one location and then sent to a second location where the extraction process could take place. Black leaf tea can also be ground in the presence of an acid, either by mixing black leaf tea and acid as dry ingredients and then grinding the mixture, or by grinding black leaf tea in the presence of an acidic solution (e.g., wet grinding black leaf tea).

As used herein, the term containing encompasses the terms consisting essentially of and consisting of. If the term comprising is used, the steps or options listed are not meant to be exhaustive.

Unless otherwise noted, numeric ranges expressed in x to y format are to be understood as including x and y. When specifying any range of values or amounts, any specific upper value or amount may be associated with any specific lower value or amount. Except for examples and comparative experiments, or where expressly stated otherwise, all numbers are to be understood as modified by the word approximately. All percentages and ratios contained herein are by weight unless otherwise noted.

The various features of the present invention mentioned in the individual sections above apply, if necessary, to other sections with the necessary modifications (mutatis mutandis). Therefore, the features specified in one section may be combined with the features specified in other sections, as appropriate. Any section headings are added for convenience only and are not intended to limit disclosure in any way.

The following examples are intended to illustrate the invention and are not intended to limit the invention to these examples as such.

Examples

Example 1

Black leaf tea was the standard grade material PF1. It was obtained through the usual processing of tea in a Kenyan plant, including collection, withering, maceration, fermentation, drying and sizing.

a) Grinding

A 160UPZ impact mill (Hosokawa Micro UK) was used to grind standard grade PF1 material into fine particles with a relatively broader size distribution. The apparatus was operated at a speed of 6000 rpm at a feed rate of 60 kg/h. The crushed particles were then screened using an ATS600 sorter (Allgaier GmbH) for different fractions with narrower sizes:

less than 26 microns, from 26 to 53 microns (fraction 1), from 150 to 250 microns (fraction 2) and more than 250 microns.

b) Extraction conditions.

g of the corresponding sample of leaf tea (grade PF1, fraction 1 or fraction 2) was extracted using 300 g of solvent for 5 min at 20°C. The solvent used to extract the leaf tea samples was either water or an aqueous citric acid solution. Four different concentrations of citric acid solution were used: 0.08% (0.24 g in 300 g of water);

- 3 041335

0.17% (0.5 g in 300 g of water); 0.67% (2 g in 300 g of water); 1% (3 g in 300 g of water). In table. 1 shows the extraction conditions. After extraction was completed, a 0.45 μm PES filter (Nalgene) was used to remove the extracted tea particles from the extraction liquid.

_____________________________________ Table 1

Sample Leaf tea Extracting solvent 1a water 1b 0.08% citric acid solution 1s faction 1 0.17% citric acid solution 1d 0.67% citric acid solution 1e 1% citric acid solution 2a water 2b 0.08% citric acid solution 2s faction 2 0.17% citric acid solution 2d 0.67% citric acid solution 2nd 1% citric acid solution Behind water 3b 0.08% citric acid solution Zs Grade PF1 0.17% citric acid solution 3d 0.67% citric acid solution Ze 1% citric acid solution

In addition, samples were prepared in which the extraction liquid obtained after extraction with water was acidified using the same four concentrations of citric acid that were used as extracting solvents. In table. 2 shows acidification conditions after extraction.

_________________________________________________________ Table 2

Sample Leaf tea Extracting solvent Citric acid added to 300 g of extraction liquid 1f faction 1 water 0.24 g 1d 0.5 g 1h 2 g 1i Zg 2f faction 2 water 0.24 g 2d 0.5 g 2h 2 g 2i Zg Sample Leaf tea Extracting solvent Citric acid added to 300 g of extraction liquid 3f Grade PF1 water 0.24 g zd 0.5 g 3h 2 g 3i Zg

c) Analysis of the extraction liquid.

Several measurements of extraction solutions were carried out. Turbidity was measured using a turbidimeter (2100P Turbidimeter, HACH) and pH was measured using a titrator (DL28 Titrator, Mettler Toledo). Brix was measured using a refractometer (refractometer RFM 340+, Bellingham + Stanley).

The concentration of tea solids in the extraction liquids was calculated from the Brix value of the extraction liquid (Brix _{tea solids} ) using the following equation:

Conc, tea solids (%) = 0.76 x Brix tea solids

For extraction liquids containing citric acid, the Brix value was measured before extraction ( _solvent Brix) and then measured again after extraction ( _liquid Brix). For these Brix samples _{, tea solids} were calculated as follows:

ΒγΪΧ tea solids ⁼ VpXliquid ^- VpXsolvent

The extraction yield was calculated using the following equation:

Yield (%) = conc. solid in-in tea (%) x 30

In table. 3 shows experimental data relating to tea solids concentration and extraction yield for the extraction liquids of samples 1a-1e, 2a-2e and 3a-3e (i.e. samples extracted with water or aqueous citric acid solution). The data demonstrate that smaller particle size is associated with a higher extraction yield and that water provides a higher

- 4 041335 extraction yield than aqueous solutions of citric acid for a given particle size.

___________________________________________________________ Table 3

Sample Extraction solvent Extraction liquid pH PVC solvent Conc, solids in tea (%) Exit (%) 1a 5.8 0 0.87 26.1 1b 2.8 0.02 0.86 25.8 1s 2.6 0.09 0.84 25.2 1d 2.3 0.58 0.82 24.6 1e 2.2 0.87 0.82 24.6 2a 5.7 0 0.77 23.1 2b 2.8 0.08 0.72 21.6 2s 2.6 0.16 0.70 21.0 2d 2.3 0.59 0.67 20.1 2nd 2.2 0.88 0.67 20.1 Behind 5.7 0 0.44 13.2 3b 2.8 0.05 0.42 12.6 Zs 2.6 0.12 0.43 12.9 3d 2.2 0.56 0.38 11.4 Ze 2.1 0.85 0.37 11.1

Color can be expressed using CIE 1976 L*a*b* color space coordinates. The CIE L*a*b* color space is built in cubic form. The L* axis runs from top to bottom. The maximum value for L* is 100 (representing an ideal reflective diffuser) and the minimum value for L* is 0 (representing black). The a* and b* axes do not have specific numerical restrictions. The a* axis continues from green (-a*) to red (+a*) and the b* axis from blue (-b*) to yellow (+b*).

The color of the extraction liquid (expressed using the CIE L*a*b* color space) was measured using a spectrophotometer (CM-5 spectrophotometer, Konica Minolta) in accordance with the ISO CIE joint standard (ISO 11664-4:2008(CE); CIE S 014-4/E:2007).

In table. 4 shows the color of the infusion samples (determined using the CIE L*a*b* color space), as well as data regarding turbidity, pH and Brix _{of the liquid}

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Sample Brix liquid pH Turbidity L* a* b* 1a 1.14 5.0 12.9 67.58 32.67 100.28 1b 1.15 4.2 7.8 77.11 23.21 101.65 1s 1.20 3.8 6.4 79.78 19.75 99.03 1d 1.66 3.0 5.1 82.51 16.69 94.10 1e 1.95 2.8 4.3 82.45 17.36 93.91 1f 1.21 3.9 18.5 72.57 28.62 104.42 ig 1.28 3.5 27.6 73.39 27.67 104.19 1h 1.75 2.8 29.9 74.57 25.78 102.83 1i 2.04 2.6 29.1 75.11 24.96 102.5 2a 1.01 5.0 7.4 69.88 29.66 99.94 2b 1.03 4.2 4.5 79.15 19.17 98.45 2c 1.08 3.8 3.1 82.11 15.00 94.61 2d 1.47 3.0 1.7 85.98 9.56 86.56 2e 1.76 2.8 1.5 86.26 9.52 85.17 2f 1.09 3.9 10.0 74.56 25.72 103.45 2g 1.16 3.5 14.0 75.67 24.36 103.22 2h 1.57 2.8 24.1 77.19 21.82 101.96 2i 1.88 2.6 24.5 77.85 20.83 101.49 3a 0.58 5.1 2.4 83.39 10.35 77.48 3b 0.60 4.0 1.6 89.78 2.15 63.78 3c 0.69 3.6 1.1 90.55 1.40 61.24 3d 1.06 2.8 0.6 92.86 -0.41 48.75 3e 1.34 2.6 0.6 93.13 -0.47 47.10 3f 0.65 3.8 3.0 86.21 6.97 75.72 3g 0.74 3.3 3.8 87.28 5.58 73.53 3h 1.14 2.7 4.6 88.29 4.36 70.53 3i 1.43 2.5 5.1 88.40 4.28 69.63

Table 4

When considering the color of an extraction liquid, the L* value is of interest, with lower L* values indicating a darker liquid color (and higher L* values indicating a lighter liquid color). The a* value is also of interest, with higher a* values indicating a redder liquid. The data in the table. 4 show that acidification after extraction is related to the color of the solution, which is darker and more red than that obtained after extraction with an acidified aqueous solution. However, acidification after extraction leads to a higher level of turbidity, which is an undesirable property for consumers. This effect is more pronounced at low pH values, especially for leaf tea fractions with a smaller particle size. This is a problem because acidification is beneficial both in improving the microbiological stability of RTD tea beverages and in formulating formulations with the desired aroma balance (especially for fruit flavored RTD tea beverages).

In contrast, extraction of leaf tea with an aqueous citric acid solution has been found to produce extraction liquids having a significantly reduced level of turbidity. Particularly low levels of turbidity have been associated with extractive solvents having a low pH.

Extraction liquors prepared from the standard grade PF1 material had a low level of turbidity (regardless of whether acidification occurred before or after extraction). However, the liquids had an unfortunate color (both in terms of darkness and redness), especially when the extraction was carried out using an aqueous acidic solution. It has surprisingly been found that extraction liquors made from cuts 1 or 2 (ie, reduced particle size loose leaf tea) have a much more acceptable color than those made from standard material grade PF1. However, only the extraction liquids resulting from the extraction of these fractions with an aqueous acidic solution had a sufficiently low level of turbidity.

The production of extraction liquids with acceptable color characteristics and low levels of turbidity from these fine particle size fractions is particularly advantageous because these liquid properties are associated with a relatively high extraction yield (see Table 3).

Thus, it has been shown that a method in which black leaf tea particles having a relatively small particle size (i.e., a particle size of less than 250 µm) is extracted with an acidic

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Claims (13)

solution, has a high extraction yield and results in an extraction solution with good color and low turbidity, even at low pH. CLAIM 1. A method for producing a black tea extract, comprising extracting black leaf tea particles with an acidic solution at a temperature of less than 35°C, wherein the black leaf tea particles have a particle size of less than 250 μm. 2. A method for producing a tea extract according to claim 1, wherein the acidic solution contains citric acid. 3. The method according to claim 2, wherein the acidic solution further comprises malic acid and/or ascorbic acid. 4. The method according to any one of paragraphs. 1-3, in which the acidic solution has a pH of 2 to 3. 5. The method according to any one of claims 1 to 4, wherein the black leaf tea particles have a particle size of 5 to 200 µm, preferably 10 to 100 µm. 6. The method according to any one of claims 1 to 5, wherein the temperature is from 10 to 30°C, preferably from 15 to 25°C. 7. The method according to any one of claims 1 to 6, wherein the method includes the step of grinding black leaf tea to obtain black leaf tea particles. 8. The method of claim 7 wherein the black leaf tea is ground in the presence of an acidic solution. 9. The method according to any one of claims 1 to 7, wherein the black leaf tea particles and the acid are mixed in the form of dry ingredients and the solvent is added in the next step. 10. The method according to any one of claims 1 to 9, wherein the black leaf tea particles are extracted with an acidic solution for less than 20 minutes, preferably less than 10 minutes. 11. The method of claim 10 wherein the black leaf tea particles and sweetener are mixed in the form of dry ingredients and the solvent is added in the next step. 12. The method according to any one of claims 1 to 11, wherein the black tea extract has a pH less than 5 and preferably has a pH of 2.5 to 4.5. 13. A method according to any one of claims 1 to 12, comprising the additional and subsequent step of separating the black leaf tea particles from the tea extract. Eurasian Patent Organization, EAPO Russia, 109012, Moscow, Maly Cherkassky per., 2