The present invention refers to the field of the cleaning and sanitation of equip- ment for producing or processing dairy products, especially equipment used in milk industry, such as milking equipment.

Especially, according to a first aspect of the present invention, the present inven¬ tion relates to methods of cleaning equipment for producing or processing dairy products.

Furthermore, according to a second aspect of the present invention, the present invention relates to the use of peroxides, preferably hydrogen peroxide, for the cleaning of equipment for producing or processing dairy products or for the acti- vation of a lactoperoxidase system (LPS)3 respectively.

The producing and processing of dairy products are often problematic in view of a spoilage and microbiological contamination of the equipment used for this pur¬ pose. Thus, a high standard of hygiene and sanitation is needed, especially with respect to the producing or processing of dairy products on an industrial level, such as milking processes, where particularly adapted industrial equipment with a high level of technical complexity is used.

Due to the complexity of said equipment, substantial amounts of dairy products may remain within said equipment after processing or producing. This implicates a potential risk of spoilage and microbiological contamination within said equip¬ ment, thus leading to serious problems with respect to the quality and hygiene of the dairy products produced or processed within such equipment.

In order to overcome the aforementioned problems many efforts have been per¬ formed in the prior art. In this context, one conventional method consists of treating said equipment with a chlorine-containing solution in such a way that said equipment is initially pre-rinsed with substantial amounts of water and then rinsed with said chlorine-contarning solution in order to remove dairy products remaining within or adhering to said equipment on the one hand and to ensure a certain disinfection, i.e. a decrease of pathogenic germs within said equipment, on the other hand. Finally, a post-rinse step with water is often required in order to remove excess chlorine. Due to hygiene requirements, a post-rinse step is mandatory by law in some countries.

However, this method exhibits particular disadvantages: The used chlorine- containing products are often instable with respect to their chemical properties. This makes them difficult to handle and furthermore leads to difficulties con¬ cerning the registration of said chlorine-containing formulations as biocides. Ad- ditionally, said cMorme-containing formulations may lead to the formation of so- called AOX-compounds (absorbable organic halides), which are discussed to be problematic with respect to environment and human health. Furthermore, this prior art method is associated with several rinse steps, thus leading to high costs concerning energy, consumption of water as well as wastewater disposal or treatment, respectively.

Due to the aforementioned disadvantages associated with the use of chlorine- containing formulations, several attempts have been made to replace said chlo¬ rine-containing solutions for this purpose. However, new formulations which have been suggested in prior art to replace said chlorine-containing formulations are deemed to be even more cost-intensive than said chlorine-containing formu¬ lations, so that their application on an industrial level is economically not attrac¬ tive.

For this reason, there is a need for a method of cleaning equipment for producing or processing dairy products. Said method to be provided should avoid or at least diminish the disadvantages related to the prior art processes discussed before, thereby ensuring a good effectiveness with respect to the cleaning and/or disin¬ fection of said equipment.

Especially, there is a need for a cleaning method for equipment for producing or processing dairy products, which renounces the use of chlorine-containing solu¬ tions and furthermore requires no pre-rinse step and is thus associated with re¬ duced expenditure and costs, especially due to a reduced water and energy con- sumption. Applicant has now surprisingly found that the problems related to the prior art methods can be overcome by using peroxides in the cleaning of equipment for producing or processing dairy products.

Thus, according to a first aspect of the present invention, the present invention relates to a method of cleaning equipment for producing or processing dairy products, said equipment being soiled with said dairy products, wherein said method comprises the step of treating said equipment with a solution containing at least one peroxide. The treating of said equipment with said peroxide- containing solution is performed in the presence of at least one peroxidase and/or of at least one thiocyanate.

In general, said peroxidase is a naturally occurring peroxidase, especially lactop- eroxidase, originating from said dairy products to be removed from said equip- ment. Also, said thiocyanate is in general a naturally occurring thiocyanate, originating from said dairy products to be removed from said equipment. With other words, according to the present invention, said peroxidase, especially lac- toperoxidase, and/or said thiocyanate are resident per se within said dairy prod¬ ucts to be removed from said equipment. This means that said peroxidase, espe- cially lactoperoxidase, and/or said thiocyanate are naturally occurring and thus intrinsic factors of said dairy products.

According to the method of the present invention, the treating of said equipment with the peroxide-containing solution may be performed without a preceding pre-rinse step. The renunciation of a pre-rinse step leads to the decisive advan¬ tage that enormous amounts of water are saved on the one hand. On the other hand, another crucial advantage is the time-optimization of the cleaning process on the basis of the absence of a pre-rinse step. On the whole, according to the method of the present invention, high amounts of costs are saved, thus leading to an economical improvement of the production and/or processing dairy products.

Furthermore, the method of the present invention is based on a natural biologic system inherent within the dairy products to be removed, thus leading to the de¬ cisive advantage that no further addition of specific disinfecting and cost- intensive chemicals exhibiting critical properties concerning e.g. human health, environment and influence on foodstuff is required.

The term "cleaning" used in the present invention refers both to the chemical and biological as well as to the mechanical removal of soils and contaminations con¬ tained within said equipment, said soils and contaminations originating from said dairy products. Especially, the term "cleaning" also comprises the disinfection, decontamination and/or sanitation of said equipment, especially the killing of microorganisms, such as pathogenic germs, and/or the prevention or inhibition of the growth thereof. Examples for respective microorganisms being affected by the method of the present invention are e.g. Campylobacter jejuni, Salmonella typhimurium, Streptococcus mutans, Listeria monocytogenes, Escherichia coli and Staphylococcus aureus.

The term "dairy products" generally refers to all kinds of dairy products. Such dairy products comprise e.g. milk, especially raw milk or processed milk, or products derived therefrom. Examples for processed milk are pasteurized milk, skimmed milk and long-life milk. Furthermore, the term "dairy products" also comprises diverse milk-containing products, e.g. cheese, curd cheese, yoghurt and milk-containing drinks.

The term "equipment" is to be understood in a broad manner, i.e. this term refers to all kinds of devices, apparatus, machines, pipes, hoses, conduits, tubes etc. used in the segment of the production and processing of dairy products, e.g. milking machines, milking collection tanks, fermenters etc.

The term "treating" is to be understood in a broad manner, i.e. this term refers to all kinds of treating methods. Especially, this term comprises the step(s) of con¬ tacting and/or rinsing the equipment with the peroxide containing solution.

Alternatively and/or in addition, peroxidase(s), especially lactoperoxidase, and/or thiocyanate(s) may be supplementarily added to the cleaning solution containing the peroxide(s). As it will be discussed in the following, this supplementary ad¬ dition may be performed in order to increase even more the effectiveness of cleaning with respect to the soiled and/or contaminated equipment. However, it is preferred that the peroxidase(s) and/or the thiocyanate(s) originate from the dairy products to be removed themselves.

According to a preferred embodiment, the peroxide-containing solution is an aqueous solution since water is a cost-efficient solvent which is easy to handle and chemically compatible with peroxides and foodstuff.

In general, according to the present invention, the peroxide is chosen with re¬ spect to its capability to activate the so-called lactoperoxidase system (LPS), as defined in the following. According to the present invention, appropriate perox¬ ides are organic and inorganic peroxides of all kinds. The preferred peroxide used in the present invention is hydrogen peroxide, especially in the form of an aqueous, preferably acidic solution.

According to a preferred embodiment, the peroxide-containing solution is an acidic solution, especially with a pH- value less than 7, preferably less than or equal 6, more preferably less than or equal 5. If necessary or required, the pH- value of said peroxide-containing solution may be adjusted to even lower values. However, also neutral or basic solutions may be applied if necessary due to spe- cific requirements.

However, acidic solutions are preferred according to the present invention in or¬ der to stabilize the peroxide within said solution, which results in a prolonged shelf-life of said solutions and thus leads to an easy handling and storage of said peroxide-containing solutions.

Said peroxide-containing solution may be acidified with at least one organic and/or inorganic acid or a respective buffer system. According to the present in¬ vention, a preferred inorganic acid comprises phosphoric acid and/or its salts.

According to the present invention, the amount of peroxide(s), especially hydro¬ gen peroxide, in said peroxide-containing solution is selected such that the per¬ oxide-containing solution has a sufficient cleaning and/or sanitation effect with respect to the equipment to be cleaned or disinfected, respectively. The peroxide concentration may be selected as a function of treating time, especially contact- ing time (i.e. duration for which the peroxide-containing solution remains in contact with the equipment to be cleaned) and thus as a function of the rate with which the peroxide-containing solution is rinsed through the equipment to be cleaned.

In general, according to the present invention, the amount of peroxide(s), espe¬ cially hydrogen peroxide, in said peroxide-containing solution may be in the range of from 0.01 to 0.2 % by weight, especially from 0.01 to 0.05 % by weight, preferably from 0.02 to 0.03 % by weight, based on the total weight of said solu- tion. However, it might be possible to deviate from these ranges if it is appropri¬ ate or required according to application necessities.

Applicant has surprisingly found that peroxides, especially hydrogen peroxide, are excellent agents for the cleaning of equipment for producing or processing dairy products. Peroxides, especially hydrogen peroxide, exhibit per se a certain disinfecting effect against microorganisms since they possess a high oxidizing potential. However, applicant has surprisingly found out that the effectiveness of said peroxides is significantly increased — namely in a surprisingly synergistic manner - when these peroxides are used for the cleaning of equipment soiled with dairy products, said effect being probably due to the presence of peroxidase, especially lactoperoxidase, and/or thiocyanate originating from said dairy prod¬ ucts.

Without being bound to a specific theory, it is believed that the application of said peroxide, especially hydrogen peroxide, leads to the activation of a so-called lactoperoxidase system (LPS), which acts as a naturally occurring inhibitor with respect to microorganisms, especially pathogenic germs. Said lactoperoxidase systems is in general a ternary system comprising (i) a particularly naturally oc¬ curring peroxidase, especially lactoperoxidase (LP); (ii) a particularly naturally occurring thiocyanate (SCN"); and (iii) a peroxide, preferably hydrogen perox¬ ide. It is believed that said lactoperoxidase system (LPS) exhibits a certain an- timicrobiological activity and thus acts as a natural disinfectant and/or inhibitor with respect to microorganisms on the basis of the lactoperoxidase catalyzed- oxidation of thiocyanate in the presence of hydrogen peroxide. The resulting hy- pothiocyanite anion (OSCN") is considered to be possibly one of the disinfecting agents due to the oxidation of essential protein and sulfhydryl groups mediated by said hypothiocyanite anion.

The lactoperoxidase system (LPS) as such is known from prior art; however, its applicability in the cleaning of equipment for producing or processing dairy products has not been considered yet.

For example, the scientific publication by G. R. Siragusa and M. G. Johnson en¬ titled "Inhibition of Listeria monocytogenes Growth by the Lactoperoxidase- Thiocyanate-H2O2 Antimicrobial System", Applied and Environmental Micro¬ biology, November 1989, pages 2802 to 2805, describes a bacteriostatic effect of the lactoperoxidase system with respect to the gram-positive bacteria Listeria monocytogenes. The experimental data presented in this publication are based merely on pure in-vitro-experiments within the scope of fundamental research.

The article by R. L. Althaus et al. entitled "Analysis Time and Lactation Stage Influence on Lactoperoxidase System Compounds in Dairy Ewe Milk", J. Dairy ScL, Vol. 84, pages 1829 to 1835, describes in a very specific manner the con¬ centration of compounds of said lactoperoxidase system (LPS) at different analy- sis times during the lactation period in ewe milk, especially in menchega ewe milk.

However, neither of the two aforementioned scientific publications refers to the specific practical use of said lactoperoxidase system in a complex technical field, especially not with respect to the cleaning of equipment for producing or proc¬ essing dairy products.

In very contrast to these scientific publications, applicant has now found that said naturally occurring lactoperoxidase system. (LPS) is surprisingly applicable on an industrial level in a complex technical field, namely with respect to the cleaning of equipment for the producing or processing dairy products, when a peroxide- containing solution is contacted with equipment soiled with dairy products com¬ prising lactoperoxidase and thiocyanate. In particular, the antimicrobial performance of the used peroxide, especially hy¬ drogen peroxide, which is known per se due to its high oxidative potential, is in¬ creased in a synergistic manner by the presence of lactoperoxidase (LP) and thiocyanate, which both originate from the dairy products to be removed. Thus, a synergistic effect based on the lactoperoxidase system (LPS) is provided by the present invention.

Consequently, the method according to the present invention has the decisive ad¬ vantage that it activates said lactoperoxidase system which is resident in the re- spective dairy products remaining in the equipment for producing or processing said dairy products. Thus, the present invention also relates to the activation of an intrinsic disinfection system ("self-disinfection"). As a consequence, no fur¬ ther addition of specific disinfecting and cost-intensive chemicals, like chlorine containing compounds, is required, which are often critical with respect to their environmental properties and with respect to their influence on foodstuff, i.e. dairy products. In very contrast to this, the method of the present invention ex¬ hibits the decisive advantage that it is a very mild method based on a natural biologic system which is inherent within the dairy products to be removed.

Furthermore, if necessary or appropriate due to application requirements, the per¬ formance of said lactoperoxidase system (LPS) may be modified or increased by the supplementary addition of peroxidase(s), especially lactoperoxidase (LP), and/or thiocyanate(s) to the cleaning solution containing the peroxidase(s).

In such a case, the respective peroxidase(s), especially lactoperoxidase (LP), may preferably be a naturally occurring peroxidase, especially lactoperoxidase (LP), which may be e.g. isolated separately from raw milk or products therefrom using methods and techniques well known in prior art.

Said supplementary addition of peroxidase(s), especially lactoperoxidase (LP), and/or of said thiocyanate(s) may be performed by using separate solutions and/or by adding said peroxidase, especially lactoperoxidase (LP), and/or said thiocyanate to said peroxide-containing solution. However, it is preferred that no supplementary addition of the aforementioned peroxidase(s) and/or thiocy- anate(s) is performed, i.e. the peroxidase(s) and/or the thiocyanate(s) should preferably originate from the dairy products to be removed themselves.

For the specific embodiment according to which the supplementary addition of peroxidase(s) to the cleaning solution is necessary or appropriate due to applica¬ tion requirements, the cleaning solution may comprise peroxidase(s), especially lactoperoxidase, preferably in the range of from 0.1 to 15 mg/kg, especially from 0.2 to 10 mg/kg, preferably from 0.3 to 5 mg/kg, based on the total weight of said solution. However, it might be possible to deviate from these ranges if it is appropriate or required according to application necessities.

If supplementary addition of thiocyanate(s) to the cleaning solution is necessary or appropriate due to application requirements, the peroxide-containing solution may comprise thiocyanate(s) in the range of from 50 to 4,000 μg/kg, especially from 100 to 2,000 μg/kg, preferably from 200 to 1,000 μg/kg, based on the total weight of said solution. However, it might be possible to deviate from these ranges if it is appropriate or required according to application necessities.

With respect to the aforementioned case, i.e. the supplementary addition of per- oxidase(s), especially lactoperoxidase, and/or thiocyanate(s) to the cleaning so¬ lution, said supplementary addition of peroxidase(s), especially lactoperoxidase, and/or of thiocyanate(s) should be performed in order to modify or increase the cleaning performance of the method according to the present invention. For in¬ stance, said supplementary addition should be performed when the content of peroxidase(s), especially lactoperoxidase, and/or thiocyanate(s) within the dairy products to be removed is not sufficient with respect to the desired cleaning ef¬ fect.

Thus, according to the present invention, it is possible to adapt the respective content of each component of the lactoperoxidase system (LPS), i.e. the naturally occurring peroxidase(s), especially lactoperoxidase (LP)5 the natural occurring thiocyanate(s) (SCN") and the peroxide(s), preferably hydrogen peroxide, in or¬ der to modify or increase the cleaning and/or disinfecting performance of the en¬ tire system. For each component of said lactoperoxidase system (LPS), its respective amount may be chosen in an amount effective to kill said microorganisms and/or to pre¬ vent or inhibit the growth thereof.

Furthermore, according to the present invention, said peroxide-containing solu¬ tion may comprise one or more further ingredients and/or additives.

For instance, the peroxide-containing solution may comprise at least one surfac¬ tant, preferably in the range of from 10 to 3.000 mg/kg, especially from 20 to 1.000 mg/kg, preferably from 50 to 300 mg/kg, based on the total weight of said solution. However, it might be possible to deviate from these ranges if it is ap¬ propriate or required according to application necessities.

The surfactant may be added in order to increase the effect of cleaning and/or disinfection of said equipment, especially with respect of the removal of par¬ ticularly fatty residues within said equipment. Surfactants usable according to the present invention may be all types of surfactants conventionally used in cleaning agents, especially for industrial applications. According to the present invention, the respective surfactants may be chosen from the group consisting of ionic (i.e. cationic, anionic, zwitterionic) and nonionic surfactants. The surfactants to be used should be compatible with the lactoperoxidase system.

According to the present invention, said dairy products to be removed from said equipment may comprise milk, especially raw milk or processed milk or prod- ucts derived therefrom. Examples for processed milk are pasteurized milk, skimmed milk and long-life milk. Furthermore, said dairy products may also comprise diverse milk-containing products, e.g. cheese, curd cheese, yoghurt and milk-containing drinks. For the reasons mentioned above, the aforementioned dairy products should contain at least one peroxidase, especially lactoperoxidase, by natural occurrence and/or at least one thiocyanate by natural occurrence.

In particular, the cleaning method of the present invention is applicable in all fields where peroxidase(s), especially said lactoperoxidase, and/or thiocyanate(s) are provided by the soils or contaminations to be removed from equipment used for the production and/or processing of foodstuff containing the respective per- oxidase(s) and/or thiocyanate(s). In this context, besides the area of dairy prod¬ ucts, i.e. especially the production and processing of milk, the area of vegetables may be another area where the present invention may be used.

According to the present invention, the inventive cleaning method may be run in a broad temperature range, especially in a temperature range of from 15 to 70 0C, especially from 40 to 70 0C. Preferably, the inventive method may be performed in the temperature range of from 40 to 70 0C. However, it might be possible to deviate from these ranges if it is appropriate or required according to application necessities. In order not to inhibit the LP system and in order to reach an opti¬ mum activity of the LP system, temperatures should not be selected too exces¬ sive, especially not too high.

According to the present invention, a subsequent rinsing, preferably with water, of said equipment may be performed after treating, especially after contacting and rinsing said equipment with said peroxide-containing solution. This so-called post-rinse step may be performed in order to prevent a new contamination and/or spoilage after the cleaning process and/or to remove eventually remaining resi¬ dues of the peroxide-containing solution within said equipment. The rinsing me- dium is preferably water, eventually supplemented with diverse additives, like preserving agents. However, the aforementioned post-rinse step is not compulso- rily required according to the present invention. Due to hygiene requirements, a post-rinse step may be mandatory by law in some countries.

Also, the present invention relates to a method of cleaning equipment for pro¬ ducing or processing dairy products, said equipment being soiled with said dairy products, wherein said method comprises the activation of a lactoperoxidase system (LPS). According to this aspect of the present invention, said activation may be realized by treating, especially by contacting and rinsing said equipment with a solution containing at least one peroxide as described above.

According to a second aspect of the present invention, the present invention also relates to the use of at least one peroxide for the cleaning of equipment for pro¬ ducing or processing dairy products, said equipment being still soiled with said dairy products. In a preferred embodiment of the present invention, said peroxide is hydrogen peroxide. However, any peroxide being able to activate the aforementioned lac- toperoxidase system (LPS) may be used in the scope of the present invention. For further details, reference is made to the above explanations which apply ac- cordingly.

Furthermore, said peroxide is applied in combination with at least one peroxidase and/or with at least one thiocyanate. Especially, said peroxidase is a naturally oc¬ curring peroxidase, especially lactoperoxidase, originating from said dairy pro- ducts to be removed from said equipment. Also, said thiocyanate is especially a naturally occurring thiocyanate, originating from said dairy products to be re¬ moved from said equipment.

Also, the present invention relates to a use of at least one peroxide, preferably hydrogen peroxide, for the activation of a lactoperoxidase system (LPS), wherein said activation is realized by the combination of said peroxide with at least one lactoperoxidase and/or with at least one thiocyanate. As described above, said lactoperoxidase and/or said thiocyanate are in general naturally occurring com¬ ponents within said dairy products.

For further details with respect to the inventive use, reference can be made to the above explanations with respect to the method of the present invention, which also apply to the inventive use accordingly.

The method and the use of the present invention lead to a great number of ad¬ vantages:

The method of the present invention replaces the conventional processes of e.g. rinsing said equipment with a chlorine-containing solution, which are often re- lated to great environmental problems and have to be performed with a large number of steps, e.g. a pre-rinse step followed by at least one subsequent rinse step and at least one post-rinse step.

The present invention exhibits the advantage that the inventive method neither requires a pre-rinse cleaning step nor requires the application of chlorine- containing disinfecting agents. Thus, the present invention is highly compatible with respect to environmental requirements and is further associated with less expenditure due to lower water and energy consumption.

Due to the impressive reduction of the use of water and due to the renunciation of chlorine, the present invention provides great advantages with respect to envi¬ ronmental aspects and human health on the one hand and with respect to a better economy on the other hand.

Furthermore, the present invention provides an effective means to replace chlo¬ rine in formulations for cleaning and/or disinfecting equipment for the produc¬ tion and processing of dairy products.

The present invention relates to the activation of a mild, naturally occurring bio- logical system with so-to-speak "self-disinfecting" properties, namely a lactoper- oxidase system (LPS), and this in an effective manner on an industrial level with a high degree of complexity and throughput.

With respect to the cleaning and/or disinfection of said equipment, the perform- ance of the inventive method can individually be adapted by the selective addi¬ tion of the respective components of the lactoperoxidase system (LPS), i.e. per¬ oxidase^), especially lactoperoxidase (LP), thiocyanate(s) (SCN") and perox¬ ide^), preferably hydrogen peroxide.

Further embodiments, aspects, variations and advantages of the present invention will be understood by the skilled practitioner when reading the description, with¬ out him leaving the scope of the present invention.

The present invention will be illustrated by the following Examples, which, however, do not limit the present invention. EXAMPLES:

Example 1:

Milking equipment (from applicant's laboratory) is soiled with raw milk (coming from a farm). This equipment is cleaned with different products without a pre- rinse step. The cleaning solution is taken at the end of the cleaning step just be¬ fore this solution is eliminated. The solution is analyzed in a microbiological de¬ partment for the total mesophilic flora. A control is made by cleaning with water only. This control gives the initial level of the contamination of the equipment.

Products used: Horolith® oxy (VFR 2310-14 from Ecolab) at 0.5 %. This is an aqueous solution comprising hydrogen peroxide and acidified with phosphoric acid.

Horolith® oxy has the following composition:

60 % phosphoric acid at 75 % (45 % final),

1 % Dequest® 2000 (containing Aminotri(methylenephosphonic acid) ATMP, purchased by Monsanto),

6.5 % hydrogen peroxide at 70 %,

1 % Dehypon® LS 54 (fatty alcohol, C12-C14, with approximately 5 moles EO and 4 moles PO, purchased by Henkel Corporation, Chemicals Group, CD Division),

1 % Eltesol® ST 90 (Sodiumtoluenesulphonate at 90%, purchased by Hunts- man Surface Sciences UK Ltd.).

This gives in a 0.5 % solution:

2250 ppm phosphoric acid,

25 ppm Dequest® 2000 (used for stabilization of hydrogen peroxide),

227.5 ppm hydrogen peroxide,

50 ppm Dehypon® LS 54,

45 ppm Eltesol® ST 90. The experimental data given in this and the following examples represent the concentration of germs in the cleaning solution.

Results:

Cleaning with water: 30,000 germs/ml

Cleaning with Horolith® oxy (i.e. containing H2O2): 35 germs/ml

Example 2:

The experimental set-up is comparable to that of Example 1. The aim is to know if the formulation without hydrogen peroxide exhibits an effect on the growth of germs.

Cleaning with water: 6,650 germs/ml

Cleaning with Horolith® oxy without H2O2 : 3 ,000 germs/ml

Cleaning with Horolith® oxy (i.e. containing H2O2): 400 germs/ml

Example 3:

The experimental set-up is comparable to that of Example 1. As the efficiency is linked to enzymatic activation of lactoperoxidase, the activity must be independ¬ ent of the substrate concentration (here: hydrogen peroxide). The aim of this ex¬ periment is to test Horolith® oxy with different contents of hydrogen peroxide.

The experiments have been made in different series. The results are given in log reduction versus cleaning with water.

2.84 ppm H2O2 : 3.2 log reduction

3.8 ppm H2O2: 3.68 log reduction

15.2 ppm H2O2 : 3.66 log reduction

113.8 ppm H2O2: 2.97 log reduction

314.5 ppm H2O2: 3.6 log reduction