EP0990154A1

EP0990154A1 - Apparatus adapted to perform a plurality of determinations on wine samples or the like

Info

Publication number: EP0990154A1
Application number: EP98917605A
Authority: EP
Inventors: Marco Mascini; Andrea Cagnini
Original assignee: Biofutura Srl
Current assignee: Biofutura Srl
Priority date: 1998-04-15
Filing date: 1998-04-15
Publication date: 2000-04-05
Also published as: WO1999053312A1

Abstract

An apparatus performs a plurality of determinations on wine samples or the like thanks to a sample (8), which is based on a combined pH probe (8, 14, 16); this probe comprises a membrane (17), which is flat, gas permeable, with a thickness comprised into a range of 5-100 micron and which co-operates with an electrochemical glass bulb (16). In order to allow the diffusion of gaseous compounds of a wine sample through the glass bulb (16) into an internal solution a substantially complete adhesion of the membrane (17) is obtained on the flat surface of the glass bulb (16), which protrudes with a projection (H) allowing a stretching action of the membrane (17) on such flat surface.

Description

Apparatus adapted to perform a plurality of determinations on wine samples or the like.

The present invention relates to an apparatus adapted to perform a plurality of determinations on wine samples or the like, comprising probing means for analysing a sample, means for containing at least one sample to be analysed and automatic instruments for performing said determinations.

It's well known that an alcoholic drink such as the wine contains a plurality of substances, which maybe are not all yet been well identified, as well as it comprises a plurality of physical-chemical data, which could define its gifts, its endowments and their evolution with time. The organoleptic properties of the wine are subject to a continuous evolution with time, too. It is sufficient to reflect that the ageing of at least certain wines can define their quality and therefore their not only commercial value. Therefore it is from time immemorial that the mankind intended to analyse the wine, as well as other alcoholic or not alcoholic drinks (cognac, brandy, beer, fruit juices, etc.) thanks to the utilization of processes and apparatuses, which were developped with the time and which are based on more and more sophisticated methods of the chemical and biological technology.

At present the apparatuses which are available on the market mainly for the analysis of the wines belong to three different classes:

- apparatuses which are typical of laboratories of public and private R&D centers. For these laboratories the main factor of the analysis is not only the cost, but mainly the exactnes ofthe results obtained by the analysis, as well as the experimental control of the new technologies, which could be applied in the future in the market of the users; - apparatuses, which utilize chemical-physical methods, which set low pourchasing costs against high running expenses, because they employ highly skilled personnel;

- typical apparatuses of big producers and/or distributors of wines or similar drinks.

Up to now and also at present time the market is missing an apparatus, which can perform, according to a rapid and low-cost process, analyses of the parameters of wines or the like in order to satisfy the requirements of small or middle-size companies, which are involved in the production or in the distribution of such drinks. Indeed, up to now said companies have been obliged to rely for the analysis of their wines on outer laboratories with the drawback to sustain the weight of high costs and long - not always acceptable - times for obtain the results of said analyses, as well as of their not always acceptable reliability.

Indeed these laboratories are not the laboratories belonging to the above mentioned R&D centers, because they are the so-called "outside contractor" laboratories, which can operate on request of the various producers/distributors of small-middle size companies. These latter are not in the conditions to utilize the apparatuses which are available on the market not only because of their high purchasing costs but also because of their high running costs due to the skilled people, which are necessary for their operation. Potential users of apparatuses are present in the market, which don't require neither substantial purchasing investments, nor heavy running costs, in the sense that said apparatuses should be operated by everyone without any especial skillness. Such users could be small-middle size producers and/or distributors of wines, which were up to now damaged by the substantially high purchasing and running costs of the apparatuses for the analysis of wine or the like (alcoholic or not alcoholic drinks) parameters. It is to be repeated that the big producers/distributors of wines have at their disposal analysis laboratories provided with very expensive apparatuses, which are operated by skilled (and therefore expensive) people. The requirements which are to be satisfied by said companies are really connected to their dimensions. Indeed said apparatuses:

- should operate a high number of analyses within substantially short times;

- should be handled thanks to a mindedness typical of a big company, which can amortize also big investments in substantially short times;

- shouldn't modify their operation working programs, which were previously decided, because of not only economical drawbacks, and so on.

The apparatuses, which are utilized by said big companies, are usually based on distillation technologies and can provide data mainly in the direction of alcoholic degrees, volatile acidity, etc. In addition they are extremely rapid for performig the analyses, as they require just some minutes and about a hundred millilitres of liquid to be distilled.

It is possible to find in the market also further apparatuses: spectrophotometers, chromatographs, which are based on gases, liquids but their purchasing costs and running espenses (due to skilled operators, who should operate them) allow them to be operated just in central laboratories at the level of R&D University and/or big Companies centers. It is to be added that the most above described apparatuses usually require pre-treatment processes of the drinks to be analysed, whereby analysis times and costs are increasing.

It seems possible at present on the light of recent discoveries in the field of chemical analyses and particularly of bio-medical applications, to proceed on the road of apparatuses, which should assembly the following advantages:

- low production costs and consequently low purchasing prices;

- substantially simple analysis processes, therefore low running costs due to the fact that skilled people for their control are not necessary;

- small quantity of the samples to be analysed (usually lower than about a hundred of millilitres);

- substantially short times necessary for obtaining the results of the analyses;

- at last the guarantee that the analysis results are substantially precise and reliable, i.e. their precision doesn't vary during the time.

Some apparatuses are well known, which are comprising a glass bulb, where the glass should be permeable to ions. Such apparatuses are defined "combined pH probes", because they are just adapted to gauge the pH of a solution.

It is possible today realize some further simple apparatuses, which use in a combined pH probe the membrane technology in order to obtain quantitative and reliable results useful, for instance, for the wine, spirit and the like production and technology. A membrane probe should be present, where the membrane is sensitive to gas. Said probe is substantially made of a combined pH electrode, which is separated from the sample by means of a membrane.

A problem is arising whenever a pH probe is utilized for requirements, which go beyond the PH solution gauging, for instance for the determination of wine parameters: the kind of the material of the membrane, its particular thickness, as well as the absolute requirement of a substantially perfect adhesion of the membrane to the glass bulb. Said problem is solved by the apparatus according to the invention, which is characterized in that it is based on a combined pH probe, said probe being adapted to comprise a substantially flat, gas permeable, having a thickness comprised into a (5-100 micron) range membrane, said membrane being co-operating with an electrochemical pH glass bulb, means being provided for obtaining a substantially complete adhesion of said membrane on a flat surface of the glass bulb in order to allow the diffusion of gaseous compounds from a sample solution to an internal solution. These and further features will be apparent from the following description and from the alleged drawings, where: Fig.l represents a perspective view of the apparatus according to the invention;

Fig.2 represents a sectional view of an electrochemical PH probe comprised in the apparatus according to the invention.

The apparatus according to the invention comprises a keyboard with a key 1 (Fig.l) which is adapted, as it will be explain later on, to gauge the pH, a key 2 for gauging the total acidity, a key 3 for gauging the volatile acidity, a key 4 for gauging the sulphur dioxide free and a key 5 for gauging the sulphur dioxide bound, all these substances belonging, for instance, to a wine sample. On a display 6 it is possible to read the values of all these gauges, as it will be explained later on.

All of such five gauges can be realized, according a way known per se, thanks to a system assisted by a microprocessor, not represented in the drawings and with an electrochemical pH glass probe schematically represented in Fig.2. This pH glass probe comprises a housing 7, which contains a specific probe 8. Such a probe is adapted to be inserted into the housing 7 after filling it, as it will be apparent later on, with a so-called "internal solution". A sleeve 9 is adapted to be screwed in correspondence of the bottom ot the housing 7. A glass container 10 is adapted to contain a small quantity of the liquid to be analised. The probe 8 internally contains a room 11 for a working electrode, whereas in its upper portion it contains a room 12 for a reference electrode, the working electrode and the reference electrode being adapted to satisfy a requirement, such as the gauge of a potential difference, which could be translated into a value of some potential parameters for instance of a wine or the like. Two circular plates 13 should avoid that the liquid contained into the working electrode 11 could pour out. The internal chamber of the probe 8 tapers into a ring 14, which is usually made of teflon, whereas a cylindrical glass probe 16 is hermetically sealed within the circular room of the ring 14. The glass probe 16 represents what is usually called "indicator electrode" and what is per se an electrochemical pH glass probe, but, when it cooperates with a membrane 17, it could become a tool adapted to perform multiple determinations, for instance on wine (or spirit or similar drinks) samples. In the case such a requirement should be satisfied, the membrane 17 should separate the sample, which is contained in the container 10, from the glass probe 16. Many kinds of membranes could used, but all these membranes must satisfy the following requirement: they shouldn't be wettable whenever they come into contact with liquid of the sample, as well as they should be permeable to gas. The active surface of the indicator electrode 16 is put in contact with the membrane 17, in such a way that a substantially thin layer of electrolytic solution (i.e. of the "internal solution") is formed between the membrane 17 and the electrode 16 surface. The gas spreads from the sample through the membrane up to the internal solution layer and then takes part to the acid-base equilibrium, as it will be explained later on. The so obtained variation is directly gauged by the indicator electrode 16. If the internal solution composition is modified, different gaseous both basic and acid species could be gauged.

But a particular problem is frequently arising: if the membrane 17 doesn't perfectly adhere to the indicator electrode 16, the thin layer of the electrolytic solution couldn't be shaped, whereby no significant and actual potential difference could be gauged. Consequently, for instance, the acetic acid, which is contained in a wine sample, should pass through the membrane 17 and the apparatus according to the invention should gauge this value just if the membrane 17 is properly stretched on the flat surface of the glass probe 16. This result could be achieved just if the glass probe 16 protrudes with its flat surface on the ring 14 thanks to a projection H. Furthermore the stretching action of the membrane 17 on the glass probe 16 is obtained by screwing the housing 7 on the sleeve 9 after interposing the membrane 17 between the housing 7 and the sleeve 9. The thickness of the membrane should be comprised within a range of (5-100 micron), its material could be made of polyethylene, polypropilene, teflon or similar porous plastics, with porosity comprised within a range of (0,01-2) micron in order to allow the diffusion of gaseous compounds from a sample solution to the "internal solution". As it will be explained later on, the "internal solution" of the gas membrane probe should be changed every time in order to obtain a probe, for instance, for acetic acid (volatile acidity) and sulphur dioxide (free or bound).

The apparatus according to the invention could be utilized for gauging the pH of a solution. In such a case, the apparatus resembles to a simple pHmeter, where no membrane is necessary on the glass probe 16. According to a way known per se the apparatus through the display 6 shows the result of this gauging operation. As for the gauging operation of the total acidity of the sample, the user will be provided with 20 ml. of a buffer solution of Na CO₃ 0,012 M/NaHCOs 0.012 M in 0.3 M of KC1; the buffer is basic (pH = 9,94) and by addition of 1 ml of the sample to such a solution all weak acids will be neurtralized. The apparatus gauges the mV. values before the addition and after the addition. The microprocessor calculates the content of the acidity of the sample expressing it as g/1. of tartaric acid. Simple messages guide according a way known per se the operator to the gauging operations and to the addition, providing in such a way the final result.

For the volatile acidity (i.e. the acetic acid content of the sample) the above mentioned probe is assembled for such measurement. Therefore the "internal solution" is prepared with few millilitres of a solution of sodium acetate 1 M and the glass probe 16 is fitted against the flat gas membrane 17. In such a way the pH probe before described is converted into an acetic acid probe. Such probe is immersed into 8 ml. of H2SO 1 M under stirring: the mV. value so obtained is recorded. Then 1 ml. of sample/standard is added. The mV. value is recorded and the microprocessor of the apparatus according to the invention directly calculates the content of acetic acid in the sample. The measurement of sulphur dioxide can be obtained with the same already described gas probe by changing the internal electrolyte of the gas electrode (the "internal

_3 solution") with Na^SaOa 5x10 M with NaCl 0,5 M. Usually such solution is protected against oxidation with compounds like ascorbic acid 0,01 M or similar antioxidants. The so assembled probe is immersed into a suitable solution, i.e. NaOH 0,1 M in order to stabilize it. Then it can be immersed into 10 ml. of standard/sample solution, the corresponding mV. value is taken and 1 ml. of H2SO4 10 M is added. After a suitable time, e.g. three minutes, the potential value is recorded and the microprocessor directly calculates the content of SO2 free.

For the measurement of sulphur dioxide bound 10 ml. of the sample are treated with 1 ml. of NaOH 5M and kept at room temperature for at least 15 minutes. The probe is immersed into such treated sample after the stabilization period in NaOH 0.1 M (the same procedure as for sulphur dioxide free is followed) and then 2 ml. of H2SO4 are added. The potential difference value is recorded as before. Then the microprocessor calculates the total sulphur dioxide taking care of the diluition realized.

Claims

C L A I M S

1. Apparatus adapted to perform a plurality of determinations on wine samples or the like, comprising probing means (8) for analysing a sample, means (10) for containing at least one sample to be analysed and automatic instruments for performing said determinations, characterized in that it is based on a combined pH probe (8,14,16), said probe being adapted to comprise a substantially flat, gas permeable, with a thickness comprised into a (5-100 micron) range membrane (17), said membrane being cooperating with an electrochemical glass bulb (16), means (7,9) being provided for obtaining a substantially complete adhesion of said membrane (17) on a flat surface of the glass bulb (16) in order to allow the diffusion of gaseous compounds from a sample solution to an internal solution.

2. Apparatus according to Claim 1, characterized in that the glass bulb (16) is adapted to protrude on the ring (14) with a projection H, allowing in such a way a stretching action of the membrane (17) on the flat surface of the glass bulb (16) and consequently the shaping of a thin layer of the electrolytic solution on the flat surface of the glass bulb (16), the projection H co-operating with the action of the sleeve (9) on the housing (7).

3. Apparatus according to Claim 1, characterized in that said membrane (17) could be made of material like polyetilene, polypropilene, teflon or the like similar porous plastics with a porosity comprised into a (5-100 micron) range, with a porosity of (0,01- 2 micron) range in order to allow diffusion of gaseous compounds from a sample solution to an internal solution.

4. Apparatus according to Claims 1,2, characterized in that the membrane should be permeable to gas of the sample to be analysed, whereby it shouldn't be wettable whenever it comes into contact with liquid of the sample, as well as it should be substantially stretched on the flat surface of the glass probe (16) nthanks to the action of a sleeve (9) on the housing (7).

5. Process for performing a plurality of determinations on wine samples or the like, said process being performed by the apparatus according to the Claims 1-3, characterized in that:

- for the gauging operation of the total acidity of the sample, the user will be provided with 20 ml. of a buffer solution of Na_CO₃ 0,012 M/NaHCO. 0.012 M in 0.3 M of KC1 with the buffer basic (pH = 9,94) and by addition of 1 ml of the sample to such a solution all weak acids will be neurtralized; the apparatus gauges the mV. values before the addition and after the addition; the microprocessor calculates the content of the acidity of the sample expressing it as g/1. of tartaric acid; suitable messages guide the operator to the gauging operations and to the addition, providing in such a way the final result;

- for the gauging operation of the volatile acidity (i.e. the acetic acid content of the sample) the probe (7,8) is suitably assembled for such measurement: the "internal solution" is prepared with few millimetres of a solution of sodium acetate 1 M and the glass probe (16) is fitted against the flat gas membrane (17); the pH probe is therefore converted into an acetic acid probe (7,8,14,16,17), which is immersed into 8 ml. of H2SO4 1 M under stirring: the mV. value so obtained is recorded. Then 1 ml. of sample/standard is added. The mV. value is recorded and the microprocessor of the apparatus according to the invention directly calculates the content of acetic acid in the sample;

- for the gauging operation of sulphur dioxide the internal electrolyte of the gas

_3 electrode (the "internal solution") should be changed with Na-S-O_ 5x10 M with NaCl 0,5 M. Usually such solution is protected against oxidation with compounds like ascorbic acid 0,01 M or similar antioxidants; the so assembled probe is immersed into a suitable solution, i.e. NaOH 0,1 M in order to stabilize it; then it can be immersed into H2SO4 10 M is added; after a substantially suitable time, e.g. three minutes, the potential value is recorded and the microprocessor directly calculates the content of SO2 free; - for the measurement of sulphur dioxide bound 10 ml. of the sample are treated with 1 ml. of NaOH 5M and kept at room temperature for at least 15 minutes. The probe is immersed into such treated sample after the stabilization period in NaOH 0.1 M (the same procedure as for sulphur dioxide free is followed) and then 2 ml. of H2SO4 are added; the potential difference value is recorded as before; then the microprocessor calculates the total sulphur dioxide taking care of the diluition realized.