DE20110719U1 - Device for monitoring and regulating fermentation processes - Google Patents

Description

BU/mo 010782G
29 June 2001

Device for monitoring and controlling fermentation processes

The invention relates to a device for determining the density of fermentation liquids and a device for the continuous monitoring and control of fermentation processes.

When producing beverages obtained through alcoholic fermentation, such as wine or beer, sugar is converted into alcohol in the fermentation process. For reasons of quality assurance, it is particularly desirable in wine production that the fermentation process is as controlled as possible, i.e. the conversion of sugar into alcohol should take place evenly over a certain period of time at a sugar degradation rate (g/day) specified by the winemaker. This requires continuous monitoring of the fermentation process based on the sugar and/or alcohol content in order to adjust the fermentation conditions, such as the must temperature, if necessary.

Especially in smaller wineries, the monitoring of the fermentation process is usually done manually.

This is usually done by the winemaker checking the temperature of the grapes at regular intervals using a thermometer.

Temperature and using an Oechsle scale to measure the approximate sugar content of the must. An Oechsle scale is a hydrometer that indicates the specific gravity of grape or fruit juice for a certain temperature, for example 15°C. The approximate sugar content of the must can be determined based on the measured specific gravity of the must. However, this value is not exact and is only suitable for a rough control of the fermentation process.

US 5,204,262 discloses a method for computer-controlled fermentation control in which the fermentation process is determined by continuously measuring the alcohol content using a diffusion-controlled ethanol sensor. The disadvantage of the method described is the high technical complexity and the associated costs. Another disadvantage is that it is not possible to draw conclusions about the biological acid degradation.

Attempts have also been made to control the fermentation process using continuous density measurements. For example, a density probe is known that is sold by the company Liquosystems in Germany and described in more detail in their company brochure "Density probe as of 2001". This is hung in the fermentation tank and electronically measures the absolute pressure at three different measuring points in the fermentation tank. The density of the must is continuously determined from the individual pressure measurements. The disadvantage of this density probe is that changes in the filling level and the depth of immersion of the density probe in the fermentation tank lead to changes in the absolute pressure.

which are many times greater than the pressure differences to be measured. The density values measured with the help of the probe are therefore susceptible to interference factors and therefore do not allow any precise conclusions to be drawn about the exact sugar content and fermentation process.

The object of the invention is to create a device for the continuous, precise, simple and inexpensive determination of the density of a fermentation liquid, which does not have the aforementioned disadvantages known from the prior art. The density value determined by the device should be suitable for the precise and continuous calculation of control variables such as sugar and alcohol content during the fermentation process and thus enable automatic monitoring and control of the fermentation process.

This object is achieved according to the invention by a device for determining the density of fermentation liquids, which

(a) a fermentation vessel for holding fermentation liquid and

(b) a piezoresistive differential pressure sensor for measuring the pressure difference in the fermentation liquid between two measuring points located at different heights in the fermentation vessel

includes.

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Preferably, the device further comprises a thermal sensor arranged in the fermentation vessel, which serves to measure the temperature of the fermentation liquid.

The piezoresistive differential pressure sensor provided in the device is surprisingly well suited to measuring densities in fermentation liquids. In contrast to density probes known from the prior art, which work according to the absolute pressure measurement method, the differential pressure sensor used according to the invention enables an exact density measurement that is essentially independent of disturbances and environmental changes. The density measurement is so exact that - as will be described in more detail below - it can be used as a measurement variable for continuous monitoring of the fermentation process, which allows direct conclusions to be drawn about the sugar, alcohol and acid content of the fermentation liquid. The device according to the invention is simple in design and can be manufactured inexpensively. It is therefore also suitable for use in smaller wineries, which generally refrain from using complex fermentation control systems for cost reasons.

The device can be used to measure density in any fermentation process, for example in the production of wine and beer. In particular, the device can be used in both continuous and batch processes. The device according to the invention is preferably used in a container intended for batch fermentation processes.

The density is determined using the device according to the invention according to the following principle: First, the pressure difference that exists between at least two measuring points at different heights in the fermentation liquid is measured. The pressure difference is measured using a piezoresistive differential pressure sensor. Such sensors are generally known to those skilled in the art and are described, for example, in US 4,411,158, US 3,764,950, US 3,820,401, US 3,930,412 and US 3,918,019. The piezoresistive sensor is preferably a sensor that is subjected to pressure from two sides. Any pressure sensors that work according to the piezoresistive principle can be used, without being limited to the aforementioned sensors described in the prior art.

The differential pressure measurement can be carried out, for example, in such a way that the differential pressure sensor is connected to connecting elements such as pipes or hoses that lead to the respective measuring point in the fermentation liquid. The connecting elements can be filled, for example, with a transmission medium such as a liquid or a gas that transmits the pressure prevailing in the fermentation liquid at the respective measuring point to the sensor in a measurable manner. The connecting elements are preferably filled with a gas, in particular with air. In order to ensure consistent measurement accuracy, it is preferably ensured during the process that the connecting elements are always filled to a constant level with the transmission medium. The connecting elements are preferably completely filled, i.e. up to the

outer end, filled with the transfer medium. Especially when using liquids as a transfer medium, it is advisable to arrange a separating membrane between the transfer medium and the fermentation liquid.

According to a preferred embodiment of the invention, the ratio of height difference between the measuring points (in cm) to the measuring range of the differential pressure sensor (in mbar) is 0.75 to 1.0, in particular 0.8 to 0.9. This achieves optimum measuring accuracy, especially for the purposes of determining the density of fermentation liquids.

For example, the height difference between the measuring points in differential pressure measurement can be about 60 cm and/or the differential pressure sensor can have a measuring range of 0-70 mbar.

According to a further embodiment of the invention, the measurement accuracy of the density measurement can be further increased by connecting a differential amplifier downstream of the differential pressure sensor, which amplifies the measuring range of the differential pressure sensor from a lower limit to an upper limit. Such differential amplifiers are generally known to those skilled in the art and are described, for example, in US Pat. No. 4,174,639. Any differential amplifiers can be used that are suitable for amplifying the measuring range of the differential pressure sensor in a desired range, without being limited to the differential amplifiers described in the aforementioned prior art.

Preferably, the differential amplifier is selected such that the measuring range to be amplified by it has a lower limit (in mbar) which corresponds approximately to the product of the height difference between the measuring points (in cm) and a factor of 0.80 to 1.10, in particular of 0.90 to 1.00.

Preferably, the differential amplifier is selected such that the measuring range to be amplified by it has a lower limit (in mbar) which corresponds approximately to the product of the height difference between the measuring points (in cm) and a factor of 1.0 to 1.3, in particular 1.10 to 1.20.

By selecting the aforementioned limits for the differential amplification, an optimal measurement accuracy is achieved especially for the purposes of determining the density of fermentation liquids.

Based on the measured pressure difference Δρ, the acceleration due to gravity g and the preferably constant height difference Δ�EEgr; of the measuring points, the density d of the fermentation liquid can be calculated using the following formula:

d =

&Dgr;&EEgr;-g

According to a preferred embodiment of the invention, the temperature of the fermentation liquid is also measured. The measurement can be made, for example, via a thermal sensor

Based on the measured temperature, the density can be converted to any temperature. Preferably, the density is calculated standardized to 2O ⁰ C.

The device for measuring the pressure difference and/or the thermal sensor can either be permanently installed in the fermentation tank or can be detachable, particularly as a hand-held measuring device. In the latter case, it must be ensured that the measurement is always carried out at the same height between the measuring points. This is best achieved by using rigid pipes that lead away from the differential pressure sensor and whose ends extend downwards into the liquid at different heights. In order to ensure accurate measurements, the hand-held measuring device must also be attached or held in the fermentation tank in such a way that the height between the two measuring points does not change during the measurement.

It is understood that the calculation of the density can be carried out with the aid of a microprocessor, in particular a microcomputer, and/or can be displayed on a display element such as an LCD display or a monitor.

It is also advantageously provided that the measured and/or calculated values are stored on a storage medium in a database.

The invention further relates to a device for the continuous monitoring and control of fermentation processes, comprising at least:

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(a) a piezoresistive differential pressure sensor for measuring the pressure difference in a fermentation liquid between two measuring points located at different heights in a fermentation vessel;

(b) a thermal sensor;

(c) a microcomputer connected to the differential pressure sensor and the thermal sensor and having access to a storage medium comprising

a first database in which the initial data of the fermentation liquid determined experimentally at the beginning of the fermentation process, such as sugar, alcohol and acid content, yeast quantity, yeast type, filling quantity, non-sugar content and/or information on the intended fermentation process such as the intended sugar degradation rate, are stored, and/or

a second database in which specific correction factors are stored for certain input materials and process conditions, and/or

a third database in which the measured and calculated values are stored,

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The microcomputer is equipped with an algorithm which allows the calculation and evaluation of fermentation process-specific control parameters based on the measured and stored data.

Such a device is suitable for carrying out the method described in more detail below, which comprises the following steps:

(a) determining the density of a fermentation liquid by continuous differential pressure measurement during the fermentation process as previously described;

(b) Determining the difference between the density determined at the beginning of the fermentation process and the current density determined during the ongoing fermentation process.

(c) Determining a current control parameter such as sugar or alcohol content of the fermentation liquid by correlating the density difference determined according to step (b) with the initial value of the control parameter which was determined at the beginning of the fermentation process.

Based on the density of the fermentation liquid determined by differential pressure measurement, targeted monitoring and control of the fermentation process is possible.

For example, at the beginning of the fermentation process, the density of the fermentation liquid can be increased above the aforementioned

•t ·

• · · . &iacgr;♦ ·*■

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Differential pressure measurement is used. At the beginning of the fermentation process, at least one reference variable of the fermentation liquid, such as sugar, alcohol, non-sugar or acid content, is determined analytically or in some other way. These initial values are recorded and serve as a correlation value for calculating the reference variables at a later point in the fermentation process.

A density difference is then calculated from the density determined at the start of the fermentation process and the density determined at any later point in the fermentation process. This difference is preferably determined continuously at equal time intervals throughout the entire fermentation process. By correlating the density difference with the value of the reference variable determined at the start of the fermentation process, the value of the reference variable can be determined at the later point in time and thus continuously tracked throughout the entire fermentation process. Continuous monitoring is preferably carried out using the sugar content as the reference variable.

Accurate values for the control variables can be obtained if the determination of the density in step (a), the density difference in step (b) and/or the control parameter in step (c) is calculated taking into account correction factors specific to the respective fermentation process.

The consideration of the correction factors in the individual steps (a), (b) and/or (c) takes into account the fact that not a linear but a

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There is a dynamic dependency between the determined density and the actual value of the control variable such as sugar content, which is influenced by a large number of parameters in the fermentation process. In order to obtain exact values for the control variables, it is therefore advisable to adjust the calculated values using correction factors. The correction factors used are specific to the respective fermentation process and include the following factors:

Yeast content and activity, process temperature,

Solids content,

Content of dissolved and undissolved carbonic acid, alcohol increase during the fermentation process, content of dissolved and undissolved carbonic acid, acid degradation,

Non-sugar components.

The correction factors can be taken into account statically or dynamically. In the case of static correction factors, the value of the correction factor remains the same throughout the entire fermentation process. In the case of dynamic correction factors, the value of the correction factor is adapted to the fermentation process and may change during the fermentation process. The most accurate values are achieved by including dynamic correction factors.

The individual values, reference variables and/or correction factors are recorded by the microcomputer, calculated, stored on a storage medium, evaluated, monitored and/or displayed on a display element.

The microcomputer has access to one or more databases in which the data required for the calculation is stored.

For example, a first database can store the initial data of the fermentation liquid determined experimentally at the beginning of the fermentation process, such as sugar, alcohol and acid content, yeast quantity, yeast type, filling quantity, non-sugar components, etc. and/or information on the intended fermentation process, such as the intended sugar degradation rate or certain temperature specifications.

For example, a second database can store the correction factors specific to certain input materials and process conditions.

For example, a third database can store measured and calculated values such as density, temperature, sugar, alcohol and acid content.

If the computer detects deviations from the values specified for the fermentation process, the user is informed preferably by a warning device, e.g. an acoustic signal, and can then intervene in and regulate the fermentation process manually, ζ. β. by changing the must temperature.

Preferably, this control of the fermentation process is automatic and is automatically stopped by the microcomputer in case of deviation from the specified fermentation parameters.

and/or depending on the values determined in steps (a), (b) and/or (c).

The fermentation process can be controlled, for example, by changing the fermentation temperature. This can be done conveniently by cooling the fermentation liquid using a cooling plate or cooling jacket, a sprinkling device or by heating the fermentation liquid using a heating rod or a heat exchanger plate.

Another possibility for regulating the fermentation process is the controlled bubbling of gases into the fermentation liquid (flotation).

The invention is explained in more detail below using an embodiment, with reference to the accompanying drawing.

In the drawing, the only figure shows a device for the continuous monitoring and control of fermentation processes with a fermentation vessel 1, a piezoresistive differential pressure sensor 2 and a thermal sensor 3. The differential pressure sensor 2 measures the pressure difference that exists between two measuring points 5,6 in the fermentation liquid 1a that are arranged at a certain height distance 7 from each other. In order to transmit the respective pressure to the differential pressure sensor 2, the latter is connected via rigid pipes 3,4 that lead into the fermentation vessel and have downwardly angled ends that represent the measuring points 5,6, whereby the pipes 3,4 are completely filled with air to transmit the pressure. The pressure measured by the differential pressure sensor at

• t · ·

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The electrical signal generated by the pressure measurement is transmitted via an electrical line 2a to a microcomputer 9, which records and further processes the signal.

The fermentation tank 1 is further equipped with a thermal sensor 8 which leads from the outside into the fermentation tank 1 and measures the temperature of the fermentation liquid 1a. The electrical signal generated by the thermal sensor 8 is transmitted via an electrical line 8a to the microcomputer 9, which records the signal and processes it further.

The microcomputer 9 has access to various databases 14, 15, 16 in which various data, previously explained by way of example, are stored that are important for calculating and monitoring the fermentation process. Using the measured data and the data stored in the databases 14, 15, 16, the microcomputer 9 calculates certain control variables such as the current sugar content of the fermentation liquid la and compares the calculated value with a predetermined target value for the sugar breakdown. The target value is either fixed by the user or calculated dynamically by the microcomputer based on the data available in the databases 14, 15, 16 in accordance with the fermentation process. If the calculated value does not correspond to the target value, the microcomputer 9 initiates steps that regulate the fermentation process. In the embodiment shown, the control takes place in that the microcomputer 9 sends electrical signals to a control valve 10 via an electrical line 9a and either opens or closes this. The control valve 10 regulates the cold and/or hot water supply 11 for a

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1 provided heat exchanger plate 13, which cools the fermentation liquid la if the fermentation is too fast and thus slows down the fermentation process or heats it if the fermentation is too slow and thus accelerates the fermentation process. The cooling water flows out of the cooling plate 13 via a pipe.

Claims (16)

1. Device for determining the density of a fermentation liquid, comprising at least a) a fermentation tank (1) for holding fermentation liquid and b) a piezoresistive differential pressure sensor ( 2 ) for measuring the pressure difference in the fermentation liquid (1a) between two measuring points ( 5 , 6 ) located at different heights in the fermentation vessel (1); 2. Device according to claim 1, characterized in that a thermal sensor ( 8 ) arranged in the fermentation container (1) is provided for measuring the temperature of the fermentation liquid (1a). 3. Device according to claim 1 or 2, characterized in that for transmitting the pressures from the respective measuring points ( 5 , 6 ) to the membrane of the piezoresistive differential pressure sensor ( 2 ), pipes and/or hoses ( 3 , 4 ) filled with gas or liquid are provided, which are arranged at a certain height distance ( 7 ) from one another in the fermentation tank (1) in such a way that they come into contact with the fermentation liquid (1a). 4. Device according to one of claims 1 to 3, characterized in that the ratio of height difference ( 7 ) between the measuring points ( 5 , 6 ) (in cm) to measuring range span of the differential pressure sensor ( 2 ) (in mbar) is 0.75 to 1.00, in particular 0.80 to 0.90. 5. Device according to one of claims 1 to 4, characterized in that the differential pressure sensor ( 2 ) is followed by a differential amplifier ( 2b ) which amplifies the measuring range of the differential pressure sensor ( 2 ) from a lower limit to an upper limit. 6. Device according to claim 5, characterized in that the lower limit (in mbar) corresponds approximately to the product of the height difference ( 7 ) between the measuring points ( 5 , 6 ) (in cm) and a factor of 0.80 to 1.10, in particular of 0.90 to 1.00. 7. Device according to claim 5 or 6, characterized in that the upper limit (in mbar) corresponds approximately to the product of the height difference ( 7 ) between the measuring points ( 5 , 6 ) (in cm) and a factor of 1.00 to 1.30, in particular of 1.10 to 1.20. 8. Device according to one of claims 1 to 7, characterized in that it comprises a microprocessor ( 9 ) which is connected to at least the piezoresistive differential pressure sensor ( 2 ) and/or the thermal sensor ( 8 ). 9. Device according to claim 8, characterized in that it comprises a storage medium which is connected to at least the microprocessor and stores the measured and/or calculated values in a database ( 14 , 15 , 16 ). 10. Device according to one of claims 1 to 9, characterized in that it comprises a display element ( 17 ) which is connected to the differential pressure sensor ( 2 ), the thermal sensor ( 8 ), the storage medium and/or the microprocessor ( 9 ) and displays the measured, calculated and/or stored values. 11. Device for monitoring and controlling fermentation processes, comprising at least: a) a piezoresistive differential pressure sensor ( 2 ) for measuring the pressure difference in a fermentation liquid (1a) between two measuring points ( 5 , 6 ) located at different heights in a fermentation vessel (1); b) a thermal sensor ( 8 ) for measuring the temperature of the fermentation liquid (1a) and c) a microcomputer ( 9 ) connected to the differential pressure sensor ( 2 ) and the thermal sensor ( 8 ) and having access to a storage medium comprising - a first database ( 14 ) in which the initial data of the fermentation liquid determined experimentally at the beginning of the fermentation process, such as sugar, alcohol and acid content, yeast quantity, yeast type, filling quantity and/or information on the intended fermentation process such as the intended sugar degradation rate, are stored, and/or - a second database ( 15 ) in which specific correction factors are stored for certain input materials and process conditions, and/or - a third database ( 16 ) in which the measured and calculated values are stored, whereby the microcomputer ( 9 ) is equipped with an algorithm which allows the calculation and evaluation of fermentation process-specific control parameters on the basis of the measured and stored data. 12. Device according to claim 11, characterized in that the differential pressure sensor ( 2 ) has the features mentioned in one of claims 3 to 7. 13. Device according to claim 11 or 12, characterized in that the microcomputer ( 9 ) is connected to an input means ( 18 ) and a display element ( 17 ). 14. Device according to one of claims 11 to 13, characterized in that a warning device is provided which emits acoustic or optical warning signals in the event of a deviation of the control parameters from the predetermined fermentation process. 15. Device according to one of claims 11 to 14, characterized in that at least one control element is provided which influences the process conditions such as fermentation temperature in the event of a deviation of the control parameters from the predetermined fermentation process. 16. Device according to claim 15, characterized in that the control element is a cooling or heating plate ( 13 ) immersed in the fermentation liquid or a cooling or heating jacket provided on the outside of the fermentation vessel or a sprinkling device.