WO2003052405A1

WO2003052405A1 - Method of determining the cleanness of a surface

Info

Publication number: WO2003052405A1
Application number: PCT/DK2002/000864
Authority: WO
Inventors: Per Famme
Original assignee: Cleansolve Holding Aps
Priority date: 2001-12-17
Filing date: 2002-12-17
Publication date: 2003-06-26
Also published as: AU2002351738A1

Abstract

The present invention relates to a method of determining the cleanness of a surface comprising the steps of treating the surface with a solvent comprising a reactive component, so as to cause the reactive component to react with contaminants, if any, being present on the surface, measuring the concentration of the reactive component after having reacted with any contaminants and determining the cleanness by comparing the measured concentration with a preselected concentration of a reactive component in the solvent. The present invention further relates to a use of the method for determining the cleanness of a surface in any apparatus.

Description

Method of determining the cleanness of a surface

The present invention relates to a method of determining the cleanness of a surface. The present invention further relates to a use of the method for determining the cleanness of a surface in any apparatus.

Production of food, drink, tobacco and any other kind of food, biotechnological products, and pharmaceuticals takes increasingly place in closed process apparatuses under the totally essential prerequisite that the production surfaces in the process apparatuses are clean at the start of the production. The requirement, as to the cleanness of the surfaces in process apparatuses and consequently the efficiency of the preceding cleaning, is that a product contacting the surfaces is not contaminated by contaminants stemming from the preceding production.

To be able to measure and document the cleanness of the surfaces in process apparatuses, the efficiency of the cleaning performed and the ease of cleaning of the individual parts of the system, a large number of methods have been developed. These methods fall within the fields of gravimetrical, physico/chemical, microbiological and physical methods (Fat.Sci.Technol., December 1989, p. 621 -624).

From Danish patent no. 155 627 it is known to detect contamination in closed production systems by measuring the conductivity of the cleaning liquid.

It is common to all these methods that none of the methods alone offer any qualitative picture of the cleanness of the production surfaces in a closed process apparatus in terms of an unambiguous assessment of the risk of contamination of the next production.

Danish published application no. 0992/92 discloses a method for qualitative and quantitative cleanness control of closed process systems. This method is based on the principle that the presence of organic substance residues on surfaces in closed production apparatuses can be demonstrated by measuring the concentration of a tracer (e.g. erythrosine) added to the rinsing water, which reacts with and binds to organic contaminations in the apparatus so that a reduction of the concentration of the tracer added to the circulating rinsing water is an expression of the degree of cleanness of the apparatus.

This method is vitiated by the quite general weakness that the chemical reaction or reactions between organic substance residues on the surfaces and the tracer added to the water entail(s) that the tracer bound to the organic contaminant represents a new and undesirable contaminant, for which reason the method presupposes extraordinary cleaning after each cleanness control, which cleaning may be difficult to perform and very time- consuming.

The technology currently known and available for cleanness control of the internal surfaces of closed process apparatuses with a view to controlling and optimizing the hygiene is not useful for cleanness control with the called for adequate sensitivity and fairly short measuring period - independently of the selected technique or combination of known techniques. In addition, the technologies are associated with drawbacks and costs which make them unuseful in general.

Thus, there is a great need for new technologies by means of which it may be documented quickly, uniformly and in a completely reproducible manner and with exact imitations of operating conditions that process apparatuses operate optimally, in that the internal surfaces are completely clean, so that a product contacting the surfaces is not contaminated by/with contaminants from the preceding production.

The object of the present invention is to provide a method of determining the cleanness of a surface. Moreover it is an object of the present invention to provide a use of the method for determining the cleanness of a surface in an apparatus. These objects are achieved by the invention as defined in the claims.

By the method according to the invention a simple, quick, cheap and reliable technology is provided, and according to which it is possible to determine the 5 cleanness of a surface in an apparatus or parts hereof.

In addition, the method according to the invention has the advantages that by carrying out the method a reduction of the current degree of contamination of the surfaces takes place, and simultaneously a disinfection is performed of l o the surfaces subjected to cleanness control.

The present invention relates to a method of determining the cleanness of a surface comprising the steps of: i) treating the surface with a solvent comprising a reactive 15 component, so as to cause the reactive component to react with contaminants, if any, being present on the surface, ii) measuring the concentration of the reactive component after having reacted with any contaminants, iii) determining the cleanness by comparing the measured 20 concentration with a preselected concentration of a reactive component in the solvent.

According to the method in step i) a solvent comprising a reactive component is treated with the surface to be subjected to determine the cleanness. The 25 treatment consists in a reaction between the reactive component and contaminants, if any, being present on the surface. By treating is meant that the solvent comprising a reactive component is brought into close contact with the surface or applied onto the surface. By the treating the reactive component reacts and dissolves the contaminants.

30

In principle, the solvent is a liquid which is poured onto the process apparatus to be subjected to determine the cleanness, by which the liquid is brought into contact with the surfaces of the process apparatus. When the solvent is in close contact with the surface, the reactive component will react preferably oxidatively with contaminants on the surface, by which the reactive component will be converted or decomposed as function of the amount of contaminants. During a given period of time, within which the oxidative processes have taken place, the concentration or a residual concentration of the reactive component in the solvent is measured. The measured concentration is an expression of the degree of contamination of the surface being subjected to cleanness control. If the preselected starting concentration and the measured concentration are identical, this implies that no reaction has taken place and that the surface is free of contaminants. If the surface is not free of contaminants, the steps i) to iii) may be repeated one or more times in order to confirm the result.

In a preferred embodiment the method further comprises a step of rinsing the surface with a liquid, if the measured concentration is not the same as the preselected concentration of a reactive component in the solvent, and then repeating the steps i) to iii). The liquid is preferably water or an organic solvent. The step of rinsing the surface with a liquid is useful in order to remove the contaminants.

Incidentally, establishment of the connection between degree of contamination and measured concentration of the reactive component can be done by experiments that are routine to the skilled person.

In one embodiment the method further comprises a step of adding tensides, wetting agents, buffers and other excipients to the solvent prior to step i). These additions may further contribute to the favourable effects of the method, as they may have a cleaning effect; pH-adjusting importance; or amplify the reaction between contaminating substances and the reactive component.

In another embodiment the method further comprises a step of adding an internal standard to the solvent prior to step i). The internal standard can be used as reference for measurements of the starting concentration and final concentration of the reactive component. As internal standard, an inert substance is preferred, e.g. inorganic salts and colouring agents. The use of an internal standard can be particularly advantageous, when the solvent is recirculated in the process apparatus and used as rinsing water.

In the method according to the invention it is preferred that the solvent is water. Hereby the method uses a cheap, readily available and environmentally friendly solvent. Furthermore, the solvent can hereby also act as rinsing water in the cleaning process, by which a process step may be saved.

In special situations, other solvents may be used, e.g. ethanol and other organic solvents. In the vast majority of situations, water is preferred.

In the method it is preferred that the reactive component is selected from a group consisting of permanganates, peroxides, chlorates, bromates and iodates. These preferred compounds all react oxidatively with contaminants, whereafter the changes in the concentration can be measured.

The concentration of the reactive component is preferably measured by a measuring means as a function of time. The concentration is preferably measured continuously or intermittently. The concentration of the reactive component is measured by measuring the reduction potential, oxidation potential, pH, colohmetry or titration.

According to the method, the preselected or starting concentration of the reactive component in the solvent depends on the type of reactive component and measuring methods used for measuring changes in the concentration so as to ensure that the measuring results will be reliable and reproducible.

In a preferred embodiment of the method according to the invention, the reactive component is potassium permanganate or sodium permanganate. In aqueous solution, potassium permanganate has a strong red colour, and the red colour will fade if potassium manganese reacts with contaminants. Hereby, there is obtained a simple method of detecting contamination on surfaces and hereby determining the cleanness of the surface. The contaminant is revealed by a colour shift in the solution, which can either be established visually or by known optical methods. In the embodiment it is thus preferred that the concentration of potassium permanganate or sodium permanganate is measured by colorimetry.

In a preferred embodiment of the method according to the invention, the cleanness control is performed by using an oxidative, autocatalytic reaction chemistry. An oxidating chemical (potassium permanganate and/or sodium permanganate) is added to the rinsing water, which chemical reacts oxidatively with all forms of contaminants, but not with the other components of the process apparatus. At the reaction with organic contaminants, slightly soluble manganese dioxide and/or divalent mangan ions are formed which subsequently catalyze the cleavage of permanganate, by which the concentration of the amount of permanganate added to the process apparatus is reduced as function of the degree of contamination of the internal surfaces due to the direct oxidative reaction between permanganate and organic contaminations and the autocatalytic cleavage of permanganate caused by the manganese dioxide and/or divalent mangane compounds formed.

Use of oxidative, autocatalytic substances of the type permanganate has the advantage that the measurable conversion of permanganate to manganese dioxide and/or divalent mangane ions at the reaction between permanganate and organic contaminant is significantly amplified by the catalytic effect of the product residue, by which the sensitivity of the measurement of organic contaminant is significantly increased.

Furthermore, the method according to the invention does not call for subsequent cleaning as the product residue (manganese dioxide and/or divalent mangane ions) is totally unharmful and, as it is, is naturally occurring in the rinsing water, just as the degree of already existing contamination is smaller than before performing the control due to the oxidative nature of the process, which also means that the cleanness control can replace the traditionally finalizing chemical disinfection as the method represents an effective disinfection of the surfaces of the process apparatus

The invention relates to a method of determining the cleanness of a surface preferably of a heat exchanger, centrifuge, spray-drier, tank, separator, sheer, evaporator, washing machine and filtration apparatus

The invention also relates to the use of a method according to the patent claims for determining the cleanness of a surface in an open or closed process apparatus Generally, the method is useful on all surfaces used for production of foodstuffs or for processing liquid and where cleanness control is required

The invention will now be described in the folllowing example

Example

Object

To determine the cleanness of a surface treated with a solvent comprising potassium manganate

Method

a) Carefully cleaned steel plates (ANSI 316, 26 mm^*76 mm) are heated to 103 °C, immersed in skimmed milk, rinsed and dried at 103 °C The plates are immersed 1 and 3 times, respectively, rinsing and drying between each immersion The plates are weighed before and after establishment of coating

Carefully cleaned steel plates without coating are used for blind experiments

b) The plates are now separately positioned in 1000 ml approx 0,01 % potassium permanganate solution under magnet stirring c) The absorbance at 526 nm is measured at intervals.

Results:

Appear from table and figure. The absorbance in blind experiments almost does not decrease; the absorbance at 1 time immersion decreases, and at 3 times immersion decreases more strongly. Note that even within the repetitions (same number of immersions), the amount of dirt correlates with the observed reduction of absorbance.

Potassium permanganate - absorbance

ι,00 5,00 10,00 15,00 20,00 25,00 30,00

Time, minutes

Claims

Patent Claims:

1. A method of determining the cleanness of a surface comprising the steps of: iv) treating the surface with a solvent comprising a reactive component, so as to cause the reactive component to react with contaminants, if any, being present on the surface, v) measuring the concentration of the reactive component after having reacted with any contaminants, vi) determining the cleanness by comparing the measured concentration with a preselected concentration of a reactive component in the solvent.

2. A method according to claim 1 , wherein steps i) to iii) are repeated one or more times.

3. A method according to claim 1 or 2, wherein said method further comprises a step of rinsing the surface with a liquid, if the measured concentration is not the same as the preselected concentration of a reactive component in the solvent, and then repeating the steps i) to iii).

4. A method according to claim 3, wherein said liquid is water or an organic solvent.

5. A method according to any one of the preceding claims, wherein said method further comprises a step of adding tensides, wetting agents, buffers and other excipients to the solvent prior to step i).

6. A method according to any one of the preceding claims, wherein said method further comprises a step of adding an internal standard to the solvent prior to step i).

7. A method according to claim 6, wherein said internal standard is an inorganic salt or a colouring agent.

8. A method according to any one of the preceding claims, wherein the treatment consists in a reaction between said reactive component and contaminants.

9. A method according to any one of the preceding claims, wherein said reactive component reacts oxidatively with contaminants.

10. A method according to any one of the preceding claims, wherein said reactive component reacts and dissolves the contaminants.

11. A method according to any one of the preceding claims, wherein the solvent is water.

12. A method according to any one of the preceding claims, wherein the reactive component is permanganates, peroxides, chlorates, bromates and iodates.

13. A method according to claim 12, wherein the permanganate is potassium permanganate or sodium permanganate.

14. A method according to any one of the preceding claims, wherein the concentration is measured by a measuring means as a function of time.

15. A method according to any one of the preceding claims, wherein the concentration is measured continuously or intermittently.

16. A method according to any one of the preceding claims, wherein the concentration of the reactive component comprising potassium manganate or sodium permanganate is measured by colorimetry.

17. A method according to any one of the preceding claims, wherein the concentration of the reactive component is measured by measuring the reduction potential, oxidation potential, pH, colorimetry or titration.

18. A method according to any one of the preceding claims, wherein said surface is a surface of a heat exchanger, centrifuge, spray-drier, tank, separator, slicer, evaporator, washing machine and filtration apparatus.

19. Use of a method according to claims 1-18 for determining the cleanness of a surface of any apparatus.