METHOD FOR TREATING PLANT LEAVES AND METHOD FOR PRODUCEING A FERMENTED PRODUCT FROM PICKED PLANT LEAVES COMPLETING CONDITIONING THE PLANT LEAVES BY APPLYING AN ELECTRIC FIELD

Description

[0001] The present invention relates to a method for treating plant leaves, for example tea or tobacco leaves, particularly in the context of producing a fermented product, as well as to plant leaves produced by this method. The method comprises the steps of wilting the plant leaves and a mechanical cell disruption process of the plant leaves.

[0002] The invention further relates to a method for producing a fermented product from picked plant leaves, for example a tea product or tobacco product, comprising the steps: optionally fermenting the plant leaves and drying the plant leaves.

[0003] A number of fermented products are made from plant leaves, for example tea and tobacco products, or herbs and spices.

[0004] A variety of products are made from the tobacco plant, especially its leaves, such as smoking or snuff tobacco, as well as concentrates and extracts for use in e-cigarettes, vaporizers and similar products.

[0005] From the tea plant ( Camellia sinensis ), especially their leaves are used to produce a variety of tea products, such as leaf tea, tea drinks, concentrates or a dried powder made from a tea leaf extract or a tea drink.

[0006] Leaf tea can be produced as green leaf tea or black leaf tea. To make black leaf tea, fresh tea leaves are withered (gently dried), then crushed, fermented, and subsequently dried. During fermentation, enzymes in the tea leaf are exposed to atmospheric oxygen to oxidize various substances and produce a brown-colored product. Green leaf tea does not undergo the fermentation process. Partial fermentation can also be used to produce an intermediate type of tea known as "oolong" tea.

[0007] In the production of tea, especially black tea, the fermentative enzymes and their substrates are released within the leaves. This occurs mechanically, and two main methods are used.

[0008] The first, so-called "orthodox" production method involves rolling withered tea leaves before the fermentation step. During rolling, the leaves are broken open using press spindles or rollers, allowing cell sap to escape.

[0009] The second method is CTC (Cut-Tear-Curl), in which the tea leaves are broken, torn, and rolled in a single step after withering. The resulting finely cut product is characterized by a fast brewing time and intense color.

[0010] A method for producing fragrant tieguanyin tea is known from CN 107 212 110 A.

[0011] A. Zderic ET AL: "Breakage of cellular tissue by pulsed electric field : extraction of polyphenols from fresh tea leaves", Chemical Engineering Transactions, June 5, 2013, CN103859079A and CN103535451B disclose a method for treating tea leaves, wherein the tea leaves are conditioned by applying a pulsed electric field.

[0012] RU2553217C1 discloses a method for fermenting sugar beet leaves, wherein the leaves are conditioned by applying a pulsed electric field.

[0013] MUSTAFA FINCAN: "Extractability of phenolics from spearmint treated with pulsed electric field", JOURNAL OF FOOD ENGINEERING, Vol. 162, April 14, 2015 discloses a method for treating mint leaves, wherein the leaves are conditioned by applying an electric field.

[0014] For the purposes of this application, the treatment step of rolling includes both orthodox manufacturing and the CTC process.

[0015] The tea production process is generally very time-consuming, energy-intensive, and costly.

[0016] The withering process can take up to 24 hours. While it can be accelerated by aerating and, if necessary, heating the picked tea leaves with fans, which can shorten the withering time, this only results in considerable energy consumption.

[0017] The process steps of rolling, fermenting, and drying also require a considerable amount of time and energy. The same applies to the production of tobacco products. It is therefore the object of the present invention to provide a method for treating plant leaves or a method for producing a fermented product from picked plant leaves, which reduces the time, cost, and energy expenditure of the conventional method.

[0018] This problem is solved according to the invention by a method for treating plant leaves, particularly in the context of producing a fermented product, in which the plant leaves are conditioned by applying a non-thermal electric field before and / or during the wilting step. The aforementioned method for producing a fermented product from picked plant leaves solves this problem by further conditioning the plant leaves according to the inventive method for treating plant leaves, i.e., by applying a non-thermal electric field before and / or during the wilting step.

[0019] The present invention has surprisingly demonstrated that conditioning plant leaves by applying an electric field accelerates the wilting process and allows for control of the oxidation level, and thus the color, taste, and aroma of the product. Furthermore, it has been surprisingly observed that the time and energy required for subsequent production steps can be significantly reduced.

[0020] The invention can be further improved by the following developments and advantageous embodiments, each of which is advantageous in itself and can be combined with each other as desired.

[0021] According to one embodiment, the plant leaves can be tea leaves, tobacco leaves, herb leaves, or spice leaves. The resulting product would then be a tea product, a tobacco product, an herb product, or a spice product.

[0022] According to one embodiment, a pulsed electric field can be applied during conditioning, causing cell disruption. This results in electroporation, in which the application of an electric field, particularly a pulsed electric field, eliminates the semipermeability of the plant cell membrane. The elimination of semipermeability and the associated cell disruption improves mass transport within the cell structures. The elimination of cell membrane semipermeability can be reversible or irreversible, with irreversible electroporation being preferred because the permanent elimination of semipermeability allows for greater flexibility in the sequence of process steps.

[0023] Conditioning by applying a pulsed electric field, hereinafter also referred to as PEF (Pulsed-Electric-Field), induces cell disruption, resulting in faster wilting and softening of plant leaves, such as tea or tobacco leaves. Furthermore, PEF-induced cell disruption promotes the release of endogenous enzymes from the plant leaf cells, thus accelerating fermentation, i.e., enzymatic oxidation. For example, the conditioning according to the invention promotes the formation of polyphenols relevant for color development, as well as the hydrolysis of leaf proteins into peptides and amino acids, which are relevant for flavor development.

[0024] Furthermore, a predetermined degree of cell disruption in the plant leaves can be achieved through conditioning according to the invention. Thus, a PEF treatment according to the invention allows for the targeted control of cell disruption and the activity of endogenous enzymes, enabling shorter fermentation and oxidation times and allowing a desired degree of oxidation, for example from 5% to 100%, to be controlled quickly and energy-efficiently.

[0025] According to a further embodiment, the conditioning step can partially replace the wilting step and / or completely or partially replace the rolling step. The conditioning process according to the invention achieves cell disruption that can at least partially replace mechanical cell disruption methods such as crushing, tumbling, breaking, or rolling, thus saving time and energy. Furthermore, it has surprisingly been found that PEF treatment, followed by rolling of the plant leaves (which also serves to shape them), results in a reduced tendency to break, so that the process according to the invention improves product quality.

[0026] During conditioning, an energy input of at least 0.1 kJ / kg, preferably 0.1 kJ / kg to 10 kJ / kg, and particularly preferably 0.5 to 3 kJ / kg, can be applied to the plant leaves. An energy input of this magnitude is well suited to carry out irreversible electroporation and to achieve cell disruption during conditioning.

[0027] Furthermore, it has been shown that applying an electric field of 0.1 kV / cm to 10 kV / cm, preferably 0.5 kV / cm to 2 kV / cm, is advantageous. Such field strengths can be achieved with commercially available industrial capacitors and prevent undesirable thermal effects during the conditioning of plant leaves, which would lead to unwanted changes in the leaves.

[0028] The electric field, and in particular the electric pulses, can be generated either through direct contact of the capacitor or its electrodes with the plant leaves, or via conductive fluids, with the plant leaves being wholly or partially immersed in the conductive fluids. Various electrode shapes can be used, such as plate, ring, grid, hollow, or flow electrodes.

[0029] Conditioning can be carried out in both batch and continuous operation. Continuous conditioning can be performed, for example, in a water bath using conveyor belts to transport the plant leaves, or, to reduce water input, by using a screw conveyor with an integrated electrode system.

[0030] A high-voltage pulse generator, for example, can be used as a pulse generator. This generator produces electric fields in the form of short pulses in the micro- to millisecond range at high voltages in the kilovolt range. Marx generators can also be used as high-voltage pulse generators.

[0031] In order to optimize time and energy, the plant leaves can be conditioned with at least 10 electrical pulses, preferably 10 to 200 electrical pulses and particularly preferably 30 to 50 electrical pulses.

[0032] The applied electric field is a non-thermally acting electric field, the energy limit of which is such that essentially no heating of the food occurs in the sense of ohmic heating. In this way, the inventive method can break down the plant leaves during conditioning in a non-thermally and non-mechanically manner and prepare the plant leaves for a subsequent processing step of withering, rolling, fermenting and / or drying.

[0033] In one embodiment of the inventive method for producing a fermented product from picked plant leaves, the plant leaves can wilt for less than 8 hours, particularly if the plant leaves are conditioned before wilting, which represents a significant reduction in time and energy compared to conventional methods.

[0034] According to another embodiment, the plant leaves can be rolled for less than 30 minutes, preferably less than 15 minutes and particularly preferably less than 10 minutes, especially if the plant leaves are conditioned either before wilting and / or before rolling.

[0035] According to another embodiment, the plant leaves can be fermented for less than 60 minutes, preferably less than 40 minutes, and particularly preferably less than 20 minutes, especially if the plant leaves are conditioned before wilting and / or rolling and / or fermentation. According to another embodiment, fermentation can take place during the steps following conditioning, particularly during rolling and / or drying. In this embodiment, a separate fermentation step can be omitted.

[0036] According to another embodiment, the plant leaves can be dried for less than 30 minutes, preferably less than 15 minutes and particularly preferably less than 10 minutes, especially if the plant leaves are conditioned before wilting and / or before rolling and / or before fermenting and / or before drying.

[0037] The invention is explained in more detail below by way of example with reference to advantageous embodiments and the drawings and subsequent experimental examples. The advantageous developments and embodiments presented are independent of each other and can be combined as required in any application.

[0038] They show: Fig. 1 a flow diagram of the process steps in the treatment of picked tea leaves in the production of a tea product; Fig. 2 a flow diagram of an embodiment of a process according to the invention; Fig. 3 a flow diagram of another example that is not part of the invention; Fig. 4 a flow diagram of a second embodiment of the process according to the invention; Fig. 5 the color change of lemon balm leaves (top) and mint leaves (bottom) as a function of the energy input during conditioning according to the invention; Fig. 6 the color change of a mint leaf extract as a function of the energy input (W) during conditioning; and Fig. 7 the color difference between an unconditioned tea leaf extract (U) and a tea leaf extract conditioned according to the invention (PEF).

[0039] The following describes a conventional method for treating tea leaves or for producing a tea product from picked tea leaves, with reference to the flow chart of the Fig. 1 The conventional methods for manufacturing tobacco products are very similar. The present invention is explained below by way of example using the treatment of tea leaves.

[0040] The flowchart of Fig. 1 outlines the sequence of process steps using the example of a traditional black tea production.

[0041] After picking, the tea leaves undergo the following treatment stages: withering, rolling, fermenting and drying.

[0042] During the withering process, moisture is removed from the picked tea leaves to soften them. In conventional withering, the tea leaves are exposed to temperatures of around 20°C for a period of 18 to 24 hours.

[0043] The wilting process is followed by the rolling treatment step. Rolling, as defined in the present invention, encompasses both the initially orthodox method, in which the leaves are broken open using press spindles or rollers so that the released cell sap mixes with atmospheric oxygen, and the CTC treatment, in which the leaves are first broken, then torn, and finally rolled. Conventional rolling typically takes at least 30 minutes.

[0044] Black tea is made by fermenting the rolled tea leaves. Fermentation is an oxidation process in which, at elevated humidity and often temperatures above room temperature (21°C), oxidation and fermentation processes are initiated, giving the black tea leaves their coppery-red to brown color and developing their characteristic aromas.

[0045] The fermentation is stopped by drying the leaf material at high temperatures above 80 °C for 20 minutes or longer.

[0046] Further processing steps, such as sieving, sorting and / or mixing of tea leaves, may follow the drying process.

[0047] The inventive method according to a first embodiment, which is shown in the flowchart of the Fig. 2The method shown was characterized by the fact that the tea leaves are conditioned by applying an electric field before wilting.

[0048] For conditioning, for example, an electric field of 0.1 kV / cm to 10 kV / cm can be applied, whereby at least 10 electrical pulses, preferably 10 to 200 electrical pulses and particularly preferably 30 to 50 electrical pulses can be introduced into the tea leaves, which corresponds to an energy input of, for example, 0.1 kJ / kg to 10 kJ / kg into the tea leaves during conditioning.

[0049] According to one embodiment, conditioning can be carried out using a PEF process, in which a pulsed electric field is applied, causing cell disruption. During conditioning, a predetermined degree of disruption of the tea leaves can be set, thereby controlling the oxidation level of the tea leaves during subsequent fermentation, and reducing the treatment duration and temperatures in the subsequent withering, rolling, fermentation, and / or drying stages.

[0050] An example of another method that is not part of the invention is shown in the flowchart of the Fig. 3 depicted.

[0051] The exemplary procedure of Fig. 3 essentially corresponds to the method of the first embodiment from Fig. 3 However, it differs in that in the example from Fig. 3The step of conditioning the tea leaves takes place not before, but after the withering step and before the rolling step.

[0052] In the flowchart of Fig. 4 An exemplary second embodiment of a method according to the invention is shown.

[0053] The method of the second embodiment is characterized in that the tea leaves are conditioned by applying an electric field during withering.

[0054] It is equally conceivable to do this with the tea leaves during rolling, or during or before any treatment stage prior to drying.

[0055] Multiple conditioning processes using an electric field to specifically prepare the tea leaves for the subsequent treatment stage are also conceivable. Experimental examples

[0056] Exemplary experiments are presented below, demonstrating that the inventive method advantageously leads to improved plant leaf products. Experiment 1

[0057] In a first experiment, herb leaves were conditioned as plant leaves with varying levels of energy input. In experimental example 1, lemon balm leaves and mint leaves were conditioned.

[0058] The Fig. 5 shows the color change depending on the energy input.

[0059] As in Fig. 5As can be observed, the higher the energy input, the darker the plant leaves become. This is related to enzymatic (browning) oxidation, when the intra- and extracellular components react with oxygen. The present experiment shows that the inventive method for treating plant leaves accelerates this browning process, and it is noteworthy that enzymatic browning begins even at a very low energy input of 0.05 to 0.1 kJ / kg. The same effect was demonstrated for a number of other plant leaves, for example, tea leaves.

[0060] It has therefore surprisingly turned out that the inventive method for treating plant leaves accelerates the enzymatic oxidation process. Experiment 2

[0061] In a further experiment, plant leaves (lemon balm leaves, mint leaves, and tea leaves) treated, fermented, and dried according to the invention were extracted in boiling water. For this purpose, 1 g each of the treated leaves of lemon balm, mint, and tea were placed in a tea bag and extracted in a measuring beaker containing 50 g of boiling water (100°C) for 10 minutes. After the extraction process, the resulting samples were examined and compared.

[0062] The experimental results are expressed as color differences of dried mint leaves depending on the energy input. Fig. 6 to see.

[0063] Fig. 7 represents the color difference between untreated and fermented tea leaves treated according to the invention.

[0064] The Figs. 6 and 7show that the inventive method accelerates the extraction of color and flavor-giving ingredients from the plant leaves, which is reflected in a stronger browning of the plant leaf extract.

[0065] The higher the specific energy input, the better the ingredients of the tea leaf product can be extracted.

[0066] The visual results were also confirmed in a sensory taste test, which showed that conditioning according to the invention leads to a more intense flavor of the plant leaf extract. The higher the specific energy input, the more intense the flavor of the plant leaf product.

[0067] The higher the specific energy input, the better the ingredients of the tea leaf product can be extracted.

[0068] The visual results were also confirmed in a sensory taste test, which showed that conditioning according to the invention leads to a more intense flavor of the plant leaf extract. The higher the specific energy input, the more intense the flavor of the plant leaf product.

Claims

1. Method for processing plant leaves, in particular in the context of producing a fermented product, comprising the steps of: - withering said plant leaves, and - mechanical cell disruption of said plant leaves, wherein said plant leaves are conditioned prior to or during the step of withering by applying a non-thermally acting electric field.

2. Method according to claim 1, wherein said plant leaves are tea leaves, spice leaves, herb leaves or tobacco leaves.

3. Method according to claim 1 or 2, wherein an electric field of 0.1 kV / cm to 10 kV / cm is applied during conditioning and / or where an energy input of 0.1 kJ / kg to 10 kJ / kg is effected into said plant leaves during conditioning.

4. Method according to any one of the claims 1 to 3, wherein a pulsed electric field is applied during conditioning which causes cell disruption.

5. Method according to any one of the claims 1 to 4, wherein a predetermined degree of disruption of said plant leaves is adjusted during conditioning.

6. Method according to any one of the claims 1 to 5, wherein conditioning disrupts said plant leaves non-thermally and prepares said plant leaves for a subsequent processing step of withering, mechanical cell disruption, fermenting and / or drying.

7. Method according to any one of the claims 1 to 6, wherein the mechanical cell disruption is shredding, tumbling, breaking or rolling, in particular rolling of the plant leaves.

8. Method for producing a fermented product from plucked plant leaves comprising the steps of: - optionally fermenting said plant leaves, and - drying said plant leaves, wherein said plant leaves are further conditioned according to the method of any one of the claims 1 to 7.

9. Method according to claim 8, wherein the step of conditioning replaces in part the step of withering.

10. Method according to any one of the claims 8 to 9, wherein said plant leaves wither less than 8 hours, and / or wherein said plant leaves are mechanically disrupted less than 30 minutes, preferably less than 15 minutes and most preferably less than 10 minutes.

11. Method according to any one of the claims 8 to 10, wherein said plant leaves are fermented less than 60 minutes, preferably less than 40 minutes and most preferably less than 20 minutes, and / or wherein said plant leaves are dried less than 30 minutes, preferably less than 15 minutes and most preferably less than 10 minutes.