WO2006015626A1

WO2006015626A1 - Cleaning of vegetable processing units

Info

Publication number: WO2006015626A1
Application number: PCT/EP2004/051777
Authority: WO
Inventors: Thomas Tyborski; Thomas Altmann
Original assignee: Ecolab Inc.
Priority date: 2004-08-12
Filing date: 2004-08-12
Publication date: 2006-02-16

Abstract

The present invention refers to the use of an alkaline aqueous cleaning solution containing a) one or more peroxide compounds, b) one or more surfactants and c) one or more sequestering agents for cleaning one or more inner surfaces of a vegetable processing unit which were in contact with the vegetable. Moreover, the present invention refers to the use of a process comprising contacting one or more inner surfaces of a vegetable processing unit which were in contact with the vegetable, with an aqueous alkaline cleaning solution as described above for cleaning said one or more inner surfaces of the vegetable processing unit.

Description

Cleaning of vegetable processing units

[0001] The present invention relates to the use of an alkaline aqueous cleaning solution containing one or more peroxide compounds, one or more sur¬ factants and one or more sequestering agents for cleaning one or more inner surfaces of a vegetable processing unit which were in contact with the vegetable. Moreover, the present invention relates to the use of a process comprising contacting one or more inner surfaces of a vegetable processing unit which were in contact with the vegetable, with an aqueous alkaline cleaning solution as men¬ tioned above for cleaning said one or more inner surfaces of the vegetable proc- essing unit.

[0002] When processing vegetables, especially carrots, often a colored cover is formed on the inner surfaces of components of a vegetable processing unit getting into contact with the vegetable. Such, for example, orange covers generally are comparatively thin and uniform and essentially are composed of carbohydrates (sugar and pectins) as well as proteins. The orange color is due to pigments, carotenoid (i. e. carotene).

[0003] Of course, beside their cleaning properties cleaning solutions used for cleaning vegetable processing units have to be toxicologically harmless. More¬ over, cleaning solutions which are appropriate to clean vegetable processing units have to be able to remove the specific soil remaining after processing. Depending on the respective soil component the demands on the cleaning solution tremen¬ dously varies.

[0004] As mentioned above carbohydrates represent a main component of the residues adhering to the inner unit surfaces. With respect to the cleaning demands carbohydrates may be divided into three groups. [0005] The compound class of the sugars (monosaccharides) generally is easily soluble in water and does not make high demands on the cleaning process as experience shows. With respect to the oligosaccharides (di-, tri- to decasaccha- ride) the solubility in water decreases with an increasing number of saccharide moieties. However, oligosaccharides can be easily removed using confectioned, alkaline cleaning agents. Yet, the group of polysaccharides (macromolecular carbon compounds like starch or cellulose) are highly demanding with regard to the cleaning process.

[0006] Beside carbohydrates vegetable, like carrots, generally contains pigments. These as well make high demands to the cleaning properties of the cleaning solutions. The pigments included in vegetables in most cases represent organic pigments. When processing for example carrots carotenoid represents the most relevant pigment.

[0007] Organic pigments have a smaller density than water. This is why they accumulate at the surface of aqueous compositions. Moreover, the surface tension of the water supports said accumulation which makes the cleaning even more difficult.

[0008] Generally, surfactants are used in the cleaning compositions to improve the cleaning performance if compounds containing large amounts of fat have to be removed from processing units. By forming micells those surfactant containing cleaning agents dissolve the fatty residues from the surfaces of the processing units, stably emulsify the fatty residues in the cleaning solution and thereby remove the fatty residues from the processing unit. However, surfactants are not appropriate to remove pigments since the pigments can not be dissolved by the surfactants in form of micells. Thus, to eliminate residues containing carbo¬ hydrates and insoluble pigments as can be found in vegetable processing units the cleaning performance of common surfactant compositions does not suffice. [0009] In such cases even after thorough cleaning with alkaline or acidic surfactant cleaning compositions the film of pigments remaining on the surface to be cleaned has to be manually removed by means of wiping with a cloth. How¬ ever, such processing units have to be cleaned regularly to prevent microbiological growth and guarantee hygienic conditions. Correspondingly, this requires much personal effort and is time and cost intense, which is not desired.

[0010] The problem underlying the present invention was to improve and simplify the commonly known cleaning procedures for vegetable processing units.

[0011] Accordingly the subject matter of the present invention is the use of an alkaline aqueous cleaning solution containing a) one or more peroxide compounds, b) one or more surfactants and c) one or more sequestering agents for cleaning one or more inner surfaces of a vegetable processing unit which were in contact with the vegetable. A further subject matter of the present invention is the use of a process comprising contacting one or more inner surfaces of a vege¬ table processing unit which were in contact with the vegetable, with an aqueous alkaline cleaning solution as mentioned above for cleaning said one or more inner surfaces of the vegetable processing unit. Preferably, the use according to the present invention is of advantage for the vegetable processing industry.

[0012] Alkali hydroxides, particularly sodium and/or potassium hydroxide, preferably represent the alkalinity source which forms the basis of the alkaline cleaning solution. However, it is also possible to use compounds with a lower alkalinity like alkali carbonates, especially sodium and/or potassium carbonate. Further appropriate alkalis are sodium and potassium silicates as well as sodium and potassium phosphates. [0013] A mixture of different alkalinity sources may also be utilized. A par¬ ticularly preferred embodiment contains alkalis from the class of compounds of alkali hydroxides.

[0014] The amount of alkali in the cleaning solution ranges from 0,1 to 10 wt.-%, preferably 0,5 to 5 wt-% based on the total cleaning solution. The pH value of the use solution as measured at room temperature preferably ranges from 10 to 14 depending on the use concentration.

[0015] The peroxide compound according to the present invention may be exemplified by anorganic as well as by organic peroxide compounds. Examples of appropriate anorganic peroxide compounds are hydrogen peroxide, perborates, especially sodium perborate, salts of monoperoxosulfuric acid, in particular potas¬ sium monopersulfate, and adducts of hydrogen peroxide to anorganic compounds, particularly the adduct to sodium carbonate referred to as sodium percarbonate, as well as adducts of hydrogen peroxide to sodium phosphates. Peroxy acids, like peroxyacetic acid, peroxypropionic acid and monoperoxyphthalic acid also repre¬ sent appropriate organic peroxide compounds. Hydrogen peroxide and hydrogen peroxide releasing substances, especially sodium borate, sodium percarbonate and organic peroxy acids are used in the most preferred embodiments. Mixtures of two or more peroxide compounds may also be applied.

[0016] The peroxide should be contained in an amount such that the active oxygen content in the cleaning solution preferably is at least 10 ppm, more pre¬ ferred at least 50 ppm over a longer time period to obtain an appropriate solution within an acceptable time. Generally, a higher active oxygen content results in an accelerated cleaning performance. On average the active oxygen content prefera- bly does not exceed 15,000 ppm , more preferred 5,000 ppm due to economical reasons.

[0017] Of course the active oxygen concentration will not remain constant in the cleaning solution over a longer time period because of a decomposition of the peroxide in the heated alkaline cleaning solution. Accordingly, the above men¬ tioned concentrations are meant to be only recommended concentrations which should be present during the main cleaning time. In a preferred embodiment of the present invention one or more peroxide compounds are added during the cleaning process for one or more times to compensate the decrease of the active oxygen concentration due to decomposition. It is either possible to add the same peroxide or peroxide mixture as was originally contained in the cleaning solution or to add a different peroxide compound or peroxide mixture.

[0018] A further advantage of the usage of the peroxide compounds beside the oxidizing effect on the pigments is the formation of oxygen gas. This effects a mechanical support of the cleaning activity. The oxygen release induces additional turbulences in the cleaning system which also occur inside the covers. Accord¬ ingly, due to a corresponding increase in volume, the cover is crushed into smaller particles which facilitates their uniform distribution in and their removal together with the cleaning solution. The (pigment) soil-bearing capacity of the cleaning solution can even be improved by means of surfactants and sequestering agents.

[0019] Beside, the use of surfactants serves to accelerate the wetting of the surfaces and the penetration of the cleaning component into the soil. In general, all kinds of surfactants known in the art are appropriate in the present invention, like anionic surfactants, non ionic surfactants, cationic surfactants and amphiprotic surfactants. Preferably the surfactants of the present invention are chosen such that they do not exhibit foaming properties to prevent the requirement to use foam inhibiting agents. Non ionic surfactants represent the most preferred surfactants in the present invention wherein the non ionic surfactant preferably is chosen from the group comprising alkoxylated fatty alcohols which optionally are terminated and/or alkylpolyglycosides and/or alkoxylated fatty amines.

[0020] Alkoxylated fatty alcohols can be exemplified by Cβ-C-is alkyl poly- ethyleneglycol propyleneglycol ether having up to 8 moles ethylenoxide (=EO) and/or propyleneoxide (=PO) moieties or mixtures thereof with the sum of ethylenoxide and propyleneoxide being up to 8 in the molecule. Moreover, adding tallow alcohol ethoxylated with 30 EO-groups as well as adding oley-cetyl alcohol ethoxylated with 5 EO-groups positively influences the cleaning performance. It is also possible to use other known non ionic surfactants like C12-C18 alkyl polyethyl- eneglycol polybutyleneglycol ether having up to 8 moles ethylenoxide and butyl e- neoxide moieties in the molecule as well as terminated alkyl polyalkyleneglycoi mixed ethers. Examples of alkoxylated fatty amines are Cβ-Cis alkylamines ethoxylated with 8 to 16 EO groups.

[0021] Substances which show chelating properties with regard to metal cations are referred to as sequestering agents in the present specification. The sequestering agents generally serve to stabilize the peroxide compounds mainly by chelating heavy metal ions which otherwise accelerate the uncontrolled de¬ composition of the peroxide compound.

[0022] Although because of the peroxide stabilizing properties sequestering agents are supposed to deactivate and thereby reduce the cleaning properties of peroxide containing cleaning solutions in contrast thereto it has surprisingly been found that those compounds improve the cleaning performance in combination with surfactants. Moreover, the sequestering agent additionally diminishes the disturbing effect of the water hardness.

[0023] Appropriate sequestering agents which can be used in the present invention are polymeric phosphates, particularly pentasodiumtriphosphate; poly- carboxylic acids and aminopolycarboxylic acids; hydroxypolycarboxylic acids, especially gluconic acid and citric acid; and phosphonocarboxylic acids, like 2- phosphonobutane-1,2,4-tricarboxylic acid, as well as their water-soluble salts, particularly their alkali salts. Preferably, the one or more sequestering agents are selected from the group comprising nitrilotriacetic acid, ethylenediaminetetraacetic acid, methlglycinediacetic acid, gluconic acid, citric acid, dicarboxamethy-L- glutamine acid, serinediacetic acid, imidosuccinic acid, polycarboxylic acids and phsphonic acids as well as the salts thereof. [0024] Polycarboxylic acids can be exemplified by polyacrylic acids and copolymers of maleic andydride and acrylic acid and the sodium salts of said polymeric acids. Common commercially available products are, for example, Sokolan^® CP5 and PA 30 from BASF, Alcosperse^® 175 and 177 from Alco, LMW^® 45N and SPO2 ND from Norsohaas. Further appropriate compounds are repre¬ sented by native polymers like oxidized starch (for example as described in DE 42 28 786 A1) and polyamino acids like polyglutamine acid or polyaspartic acid which may be obtained for example from Cygnus, Bayer, Rohm & Haas, Rhone Poulenc or SRCHEM.

[0025] Examples for appropriate phosphonic acids are polyphosphonic acids and aminopolyphosphonic acids like 1-hydroxyethane-1,1-diphosphonic acid, diethylenetriamine pentamethylenephosphonic acid or ethylenediamine tetramethylenephosphonic acid and the corresponding alkali salts.

[0026] The total amount of the sequestering agents used in the present invention depends on their single activities and preferably lies within the range of from 0,07 to 2 wt.% based on the total cleaning solution.

[0027] A further advantage of the above described cleaning solution is that the solution already provides antimicrobial effect. Thus, additional disinfection after cleaning is not required. Obviously, this tremendously reduces the cleaning effort and the costs.

[0028] Optionally the present cleaning solution contains further additives and/or auxiliaries which are commonly used if their presence seems to be func¬ tional. Appropriate additives and auxiliaries are foam inhibiting agents and solutiz- ers. Their concentration depends on their intended purpose.

[0029] According to the uses of the present invention the alkaline cleaning solution is supposed to act upon the surfaces of the processing unit to be cleaned. Temperatures above 5O⁰C are preferably applied to achieve this purpose. It is particularly advantageous that the process requires temperatures above 10O⁰C only in very few cases to obtain fast cleaning. Accordingly, generally it is possible to proceed pressure free. In an especially preferred embodiment the cleaning temperature is in the range of from about 50 to about 95⁰C. Of course, the time required for complete cleaning depends on the cleaning temperature but it also depends on the composition of the cleaning solution. In most cases it is possible to achieve completely satisfactory cleaning results for such a processing unit within a time period of about 5 minutes to about 2 hours.

[0030] There are several possible ways for treating the surfaces with the alkaline cleaning solution in the process presently used. For example the inner walls of large containers may be sprayed from inside with the cleaning solution.

Optionally, the surfaces can be additionally treated manually with the cleaning solution like with a cloth or a sponge or similar devices. However, it is preferred to lead the cleaning solution through a processing device, the pipelines and contain- ers of which are filled to various extents, wherein a circulating of the cleaning solution is particularly preferred. Such a method is referred to as cleaning-in- place(CIP)-method.

[0031] The heating devices of the unit may be used to heat the cleaning solution. With respect to larger units it may be advantageous to treat the unit sector by sector to limit the total required amount of the cleaning solution.

[0032] The cleaning solution can be prepared by adding all of the com¬ pounds separately to a corresponding amount of ether before, after or while heat¬ ing the cleaning solution. The cleaning solution preferably contains alkaline compounds and a mixture of sequestering agents and/or surfactants. Alternatively, two separate aqueous concentrates can be prepared first which are combined to obtain the cleaning solution. Preferably, one concentrate contains alkali, in particu¬ lar selected from the group comprising alkali hydroxide, alkali carbonate and mixtures thereof, and optionally one or more compounds selected from the group comprising surfactants, sequestering agents and one or more further additives and/or auxiliaries.

[0033] One or more further concentrates contain one or more peroxide compounds which one or more peroxide compounds may be the same or different in two or more further concentrates, and optionally the concentrates contain one or more compounds selected from the group comprising surfactants, sequestering agents and one or more further additives and/or auxiliaries. However, at least one of the concentrates has to contain the one or more surfactants and at least one of the concentrates has to contain the one or more sequestering agents.

[0034] Using the main compounds of the cleaning solution in two or more liquid concentrates enables automatic dosage and at the same time provides for the separation of the alkalinity source and the peroxide compound. This results in improved storage stabilities of the concentrates before use. It is also possible to prepare a third concentrate which mainly provides the sequestering agent. Thereby, the sequestering agent may be offered in higher concentrations. Such a kind of separation additionally helps to prevent difficulties with regard to formula¬ tion.

[0035] In an especially preferred embodiment of the inventive uses the parts of the processing unit to be cleaned will be filled with an alkaline cleaning solution first and this solution circulates within the unit while heating the unit until the de¬ sired cleaning temperature is reached. Afterwards the one or more peroxide compounds, preferably in form of one or more concentrates, are added to the cleaning solution. It is particularly preferred to add the one or more further concen¬ trates just at those points in the unit which are excessively soiled to obtain the most effective cleaning results. It may as well be advantageous to add one or more portions of the same one or more peroxide compounds or of a different composition of peroxide compounds during the cleaning process. The one or more portions may be added either selectively, continuously or periodically. This is especially effective in case that the composition of the bath is intended to achieve a fast decomposition of the peroxide compounds. Additionally, the cleaning may as well proceed as is described in the unpublished European application 0 975 884.8.

[0036] After treating the processing unit with the alkaline cleaning solution the unit is rinsed preferably with drinking water at a temperature of from 20 to 60⁰C for 1 to 2 hours. In smaller processing units the rinsing time may even be reduced to 10 to 30 minutes.

[0037] Optionally, the cleaning solution can be stapled up to the next clean¬ ing process. Under those circumstances, it is preferred to compensate the decom- position of the peroxide compound during storage by adding fresh peroxide compound before the next cleaning process starts.

[0038] In a further preferred embodiment the cleaning solution is freed from the organic load which mainly results from the removed soil particles. The freeing preferably proceeds by centrifuging, filtering or other separating methods used to clean a solution, and serves to reduce the load und maintain the cleaning per¬ formance. Separation of the organic particles from the solution can take place during the cleaning process or afterwards. A periodic acidic cleaning step (for example every 3 to 6 months) can make sense depending on the water hardness.

Examples

1. Composition of the concentrates

[0039] In the following tables 1 to 3 the composition of the concentrates A1 and A2, the concentrates B1 and B2 and the concentrates C1 and C2, containing surfactant, peroxide and/or sequestering agent are presented, which concentrates are used to prepare the corresponding cleaning solutions. If not indicated other- wise the values refer to wt.-% based on the single concentrate. Table 1

¹nitrilotriacetic acid

N1 represents commercially available non ionic surfactants containing ethyleneox- ide and propyleneoxide

Table 2

Table 3

2. Laboratory tests

[0039] The combination of several concentrate compositions was tested with regard to their cleaning performance with plastic tapes (FAB2 conveyor, Habasit) which were soiled for 12 hours with cut carrots as commercially available in form of baby food products. The cleaning temperature was 8O⁰C and the clean¬ ing time was 20 minutes. Afterwards the test tapes were rinsed with water without additional pressure. With all combinations as specified in table 4 visually deter¬ mined cleaning performance was very good to excellent. However, the best result was obtained using combination A1 + B1 + C1 and A2 + B2. The percentages refer to wt.-% of the concentrate based on the total cleaning solution. The remain¬ ing amount of the cleaning solution is mainly represented by water but may also represent further additives and/or auxiliaries. Table 4 Tested concentrate combinations

3. Cleaning of pipelines

[0040] The cleaning performance of composition A1 + B1 + C1 was tested on steel pipelines having an inner volume of 50 I which were soiled with carrot mush in a thickness of about 1 mm on average. Cleaning proceeded with about 300 1 cleaning solution corresponding to Nr. 2 in example 2. The cleaning solution was heated to 77 to 89°C by means of direct steam for 30 minutes. Some parts were pre-treated with a nitric acid based cleaning formulation. After 5 and 20 minutes 300ml each of B1 were post-dosed. The cleaning performance was de¬ termined visually.

[0041] As a result even by steam heating which leads to additional dilution, about 90% of the residues were removed. Accordingly constant cleaning process¬ ing is supposed to result in even better values. The pre-treatment had no influence on the cleaning result.

4. Cleaning of a screw (reduced penstock)

[0042] A screw supposed to be cleaned with an internal volume of about

100 1 was uniformly discharged with a carrot-cover of about 1 mm thickness. To enhance the spraying pressure two of three internal penstocks were blind flanged. This lead to a pump pressure of about 2,5 bar divided on 10 nozzles.

[0043] The cleaning proceeded using about 1001 cleaning solution compris¬ ing 3 wt.-% A1 , 1 wt. -% B1 and 1 wt.% C1 based on the total cleaning solution. 5 There was no screw movement. The cleaning solution was heated by direct steam to a temperature of from 77 to 82⁰C for 45 minutes. The lower part of the screw was pre-treated with a nitric acid based cleaning formulation. After 5, 15 and 30 minutes 2I each of B1 were post-dosed. The cleaning performance was deter¬ mined visually.

io [0044] As a result all the areas reached by the spray pressure were com¬ pletely clean. The areas not completely reached by the spray pressure were only partly cleaned. The pre-treatment did not influence the cleaning performance.

5. screw (complete penstock)

[0045] Testing 4 was repeated using all spray nozzles. The cleaning con- i5 centration corresponded to the one of testing 4. The cleaning time was 20 min¬ utes. The screw was not pre-treated. After 5 and 15 minutes 2I each of B1 were post-dosed and, additionally, after 15 minutes 2I A1 were post-dosed. The clean¬ ing performance was determined visually.

[0046] Areas reached by the spray pressure were completely clean wheras 20 areas which the spray pressure did not reach were still partly soiled.

[0047] The above presented results with regard to the cleaning performance illustrate that the above described cleaning composition as well as the cleaning method are appropriate to excellently remove even persistent pigment and poly¬ saccharide containing soil.

25

Claims

1. Use of an alkaline aqueous cleaning solution containing a) one or more peroxide compounds, b) one or more surfactants and c) one or more sequestering agents for cleaning one or more inner surfaces of a vegetable processing unit which were in contact with the vegetable.

2. Use of a process comprising contacting one or more inner surfaces of a vege¬ table processing unit which were in contact with the vegetable, with an aque- ous alkaline cleaning solution according to claim 1 for cleaning said one or more inner surfaces of the vegetable processing unit.

3. Use according to claims 1 or 2 characterized in that the amount of alkali in the aqueous alkaline solution ranges from 0,1 wt.-% to 10 wt.-% based on the total aqueous alkaline solution.

4. Use according to any of claims 1 to 3 characterized in that the aqueous alka¬ line solution contains at least 10 ppm active oxygen and not more than 15,000 ppm active oxygen based on the total aqueous alkaline solution.

5. Use according to any of claims 1 to 4 characterized in that the treatment of the surfaces proceeds at a temperature of from 50 to 100⁰C.

6. Use according to any of claims 1 to 5 characterized in that the aqueous alka¬ line solution is lead through the unit.

7. Use according to any of claims 1 to 6 characterized in that the peroxide com¬ pound is selected from the group comprising hydrogen peroxide, anorganic peroxide compounds, organic peroxide compounds and mixtures thereof.

8. Use according to claim 7 characterized in that the organic peroxide compound is an organic peroxycarboxylic acid, in particular peracetic acid.

9. Use according to any of claims 1 to 8 characterized in that one or more perox¬ ide compounds which may be the same as originally contained in the aqueous alkaline cleaning solution or different therefrom, are added during the cleaning process for one or more times.

10. Use according to any of claims 1 to 9 characterized in that the aqueous alka¬ line cleaning solution additionally contains further additives and/or auxiliaries.

11. Use according to one of claims 1 to 10 characterized in that the cleaning solu- tion is prepared from at least two separate aqueous concentrates wherein at least one concentrate contains alkali, in particular selected from the group comprising alkali hydroxide, alkali carbonate and mixtures thereof, and optionally one or more compounds selected from the group comprising surfactants, sequestering agents and one or more further additives and/or auxiliaries, and

at least one of one or more further concentrates contains one or more per¬ oxide compounds which one or more peroxide compounds may be the same or different in two or more further concentrates, and optionally con¬ tains one or more compounds selected from the group comprising surfac- tants, sequestering agents and one or more further additives and/or auxiliaries,

provided that at least one concentrate contains one or more surfactants and at least one concentrate contains one or more sequestering agents.

12. Use according to one of claims 1 to 11 characterized in that the sequestering agent is selected from the group comprising nitrilotriacetic acid, ethylenediami- netetraacetic acid, methyleneglycerinediacetic acid, gluconic acid, citric acid, dicarboxymethyl-L-glutamic acid, serinediacetic acid, imidosuccinic acid, poly- carboxylic acid and phosphonic acid and the salts thereof.

13. Use according to any of claims 1 to 12 characterized in that the sequestering agent is contained in the cleaning solution in an amount of from 0,07 to 2 wt-% based on the total cleaning solution.

14. Use according to any of claims 1 to 13 characterized in that the peroxide compound is added to the aqueous alkaline cleaning solution after the cleaning solution is heated up to the intended cleaning temperature.

15. Use according to any of claims 1 to 14 characterized in that the peroxide compound is added selectively, periodically or continuously to the cleaning so¬ lution at a position of the vegetable processing unit which is excessively soiled.