Process and device for cleaning surfaces which are heavily soiled with grease, starch and/or proteins, especially in the food processing industry

A device for cleaning surfaces which are soiled in the food industry with grease, starch or protein residues including: a housing body having a first inlet for feeding pressurized water; a propulsion jet positioned behind the inlet and in a direction of flow; a collection jet positioned behind the propulsion jet which is flow connected with a second inlet for feeding a chlorine-free alkaline foam cleaning agent and a third inlet for feeding a hydrogen peroxide solution; and a turbulence chamber into which an elongated jet body of the collection jet extends, the turbulence chamber fitted with a chamber inlet for feeding compressed air into the chamber such that a hydrogen peroxide foam is formed from a solution formed upon dosing an effective amount of the hydrogen peroxide solution into the chlorine-free alkaline foam cleaner at a maximum of 60 seconds prior to contact of the hydrogen peroxide foam with a surface to be cleaned, the turbulence chamber further having a chamber outlet through which the hydrogen peroxide foam leaves the chamber to contact the surface, the chamber inlet and the chamber outlet being fitted in a direction of flow ahead of an outlet orifice of the jet body.

FIELD OF THE INVENTION 
The invention concerns the technical field of cleaning heavily soiled 
surfaces in the food processing area, for instance in the meat and fish 
processing industries, vegetables processing or the pastry industry. The 
invention particularly concerns a process according to the concept as 
summarised in claim 1 as well as a device for carrying out the process 
according to the invention. 
BACKGROUND OF THE INVENTION 
In the food processing industry, in particular in heavily soiled areas, 
such as slaughterhouses or meat and fish processing industries, tenacious 
soiling through grease, protein and starch residues is the rule of the 
day. According to a practical state of the art, for cleaning such stubborn 
soiling, alkaline cleaning agents containing chlorine are regularly used. 
Because of the chlorine content of the cleaning agent, combined with an 
alkaline medium, the grease, starch and protein soiling is dissociated, 
whereby shorter molecule components are created from molecules with a 
longer chain, which are then capable of being emulsified by surfactants 
present in the cleaning agents. 
However, the high volumes of waste water created in this way cause severe 
problems because of their chlorine content. On the one hand, the 
environmental effect of waste water containing chlorine is not 
insignificant. On the other hand, if accidentally instead of an alkaline 
medium an acid medium exists or is created, gaseous chlorine may be 
generated, creating an occupational hazard. Therefore, the use of 
oxidising cleaning agents based on chlorine is generally problematic in 
the said industry areas. 
Hence the problem is posed to provide a less ecologically harmful cleaning 
process, which however, as regards its cleaning properties, is at least 
equal to processes using cleaning agents containing chlorine, or which 
exceed the cleaning action of the latter at equal or even lower dosages. A 
further purpose of the invention is to provide an appropriate device for 
carrying out the process. 
DEFINITION OF THE INVENTION 
These problems, as well as other problems which are not presented 
individually, are solved by a cleaning process of the type mentioned at 
the beginning, characterised by the features indicated by the 
characterising part of claim 1. Effective process modifications are 
protected by the subclaims which are standing in relation to claim 1. 
With regard to a particularly appropriate device for performing the process 
according to the invention, the subject of claim 7 provides a solution for 
the problems underlying the invention. Favourable embodiments are the 
subject of the claims which relate to claim 7. 
DETAILED DESCRIPTION OF THE INVENTION 
Because of the fact that an effective amount of hydrogen peroxide solution 
is added to the chlorine-free alkaline foam cleaner at the latest 60 
seconds before contact with the surface to be treated, in order to obtain 
an hydrogen peroxide foam which is able to clean effectively, it is 
possible to substitute the alkaline foam cleaners which contain chlorine 
and which were being used generally up to now and which were causing 
environmental pollution because of their chlorine content. Because of the 
environmental harmlessness of a hydrogen peroxide solution, the 
environmental pollution is clearly reduced with a cleaning process 
according to the invention, in particular the substances used are a priori 
less harmful with respect to the environment. 
Furthermore, the cleaning process according to the invention is superior 
compared to the process according to the practical state of the art as 
regards occupational safety aspects. In case of accidental contact with 
acids or an acid medium, no toxic gases can develop from the cleaning 
system according to the invention. 
Finally, the cleaning process according to the invention provides further 
unexpected advantages as compared with the state of the art. 
Thus, it can be considered particularly surprising that it was possible 
after all that by using a hydrogen peroxide solution a foam cleaner is 
produced with sufficient foam stability. Apart from this, it could also 
not be expected that the cleaning action, which can be obtained with the 
cleaning process according to the invention, is a clear improvement on the 
most recent state of the art. Finally, the professional could not foresee 
without anything else that the foam system consisting of two components 
possesses, apart from a cleaning activity, also a microbiological 
activity, which is increased unexpectedly in comparison with the use of 
individual components. 
The alkaline foam cleaner to be used in the cleaning process according to 
the invention consists of at least two components, which should be mixed 
shortly before application. 
In this respect, "shortly" means, in the sense of the invention, that one 
of the components, i.e., the chlorine-free alkaline foam cleaner, has to 
be mixed with the other component, i.e., the hydrogen peroxide solution, 
not later than 60 seconds before the contact with the surface to be 
treated. If this interval is clearly exceeded, oxidative deterioration of 
the cleaning components contained in the alkaline foam cleaner may 
develop. One should strive to mix both components as shortly as possible 
before application to the surfaces to be cleaned. This corresponds with a 
preferred modification of the process according to the invention, i.e. to 
add the hydrogen peroxide solution to the chlorine-free alkaline foam 
cleaner at the latest 10 seconds before contact with the surface to be 
treated. 
The cleaning process according to the invention is characterised as being 
particularly effective when the hydrogen peroxide solution is added to the 
alkaline foam cleaner within a period of time in the range of 0.01 to 1 
seconds before contact of the hydrogen peroxide foam, which is being 
released during the addition, with the surface to be treated. 
Thereby, pre-mixing of both components of the foam cleaning system to be 
applied according to the invention may be done in any manner which is 
known to the professional and which is appropriate at the same time. Thus 
it is e.g. possible to mix the chlorine-free alkaline foam cleaner and the 
hydrogen peroxide solution batch-wise together and then to use them within 
a short period of time. Contrary to this, however, it is much more 
preferred to add the hydrogen peroxide solution continuously to the 
alkaline foam cleaner solution. In this context, both components to be 
kept separately until shortly before the application, for example as 
concentrates, may be adjusted by means of water under pressure to the 
application concentration. It is particularly advantageous to dose the 
hydrogen peroxide solution in such a quantity as is required for the 
consumption of the hydrogen peroxide foam which is active in the cleaning 
of the soiled surfaces. With respect to batch-wise mixing, this continuous 
process furthermore has the advantage that it is capable to practically 
prevent completely the premature dissociation of the H.sub.2 O.sub.2 into 
inactive components in the alkaline cleaning solution. 
In the alkaline medium, H.sub.2 O.sub.2 is converted much more into the 
active HO.sub.2 anion, which then should be considered to be the actual 
oxidising bleach component. In this way, because of the minimal mixing and 
contact times during the continuous process, the efficiency of the 
hydrogen peroxide foam cleaner according to the invention is clearly 
enhanced as compared to a batch-wise procedure. 
The process according to the invention may be performed in a particularly 
advantageous way by using special mixing devices, which enable intensive 
mixing of both components of the foam cleaning system according to the 
invention at extremely short mixing times, while allowing the air supply 
which is required for producing the foam. For this purpose, for instance, 
special injection systems, which will be described further following 
hereafter, are particularly appropriate. 
One of the components of the foam cleaning system according to the 
invention concerns a chlorine-free alkaline foam cleaner. The 
chlorine-free alkaline foam cleaner may be present as a pre-concentrate, 
which preferably is liquid and consists of 
(i) 3-30 wt. % alkali hydroxide 
(ii) 1-10 wt. % alkyl amine oxide with the general formula I 
EQU C.sub.m H.sub.2m+1 NO(C.sub.n H.sub.2n+1).sub.x (C.sub.n 
H.sub.2n+1).sub.y(I) 
whereby m is an integer from 8-18, n is 1 or 2 and x and y are integers 
from 0-2, and x+y=2, 
(iii) 2-10 wt. % usual ingredients and 
(iv) made up to 100 wt. % with water. 
This pre-concentrate is diluted at the time of application or shortly 
before to a concentration of between 0.1 and 5 weight per cent, preferably 
0.1-2.5 weight per cent, particularly advantageously 0.15-2 weight per 
cent active ingredients (i)+(ii), usually with water or aqueous media, for 
instance water under pressure. 
An essential component of the chlorine-free alkaline foam cleaner is the 
component (i). Among the alkali hydroxides capable of being used are LiOH, 
NaOH, KOH. Of these, KOH and NaOH are preferred, and NaOH is particularly 
preferred. The alkali hydroxides may be used in solid form or in the form 
of a solution for producing the chlorine-free alkaline foam cleaner. 
Usually they are present in the dissolved form in the foam cleaner, or at 
least they are dissolved in the application solution. 
Component (ii) of the chlorine-free alkaline foam cleaner is also an 
essential component. Alkyl amine oxides according to the general formula I 
are known as such and are familiar to the professional. The compounds 
mentioned are either commercially available or may be synthesised 
according to known processes. 
The alkyl amine oxide according to the general formula I shows a cationic 
behaviour under acidic conditions (pH&lt;3), however, under the alkaline or 
neutral pH values to be maintained according to the invention they behave 
as nonionic surfactants. 
The alkyl amine oxides mentioned show a particularly high foam stability. 
Among the compounds according to the general formula I, particularly 
suitable are those in which: 
m=8-16 
n=1 
x=1 and 
y=1 
Furthermore, compounds for which m=10-14 are preferred. 
Component (iii) contains all usual ingredients, which are applied in 
conventional alkaline foam cleaners, among others also in chlorine 
containing foam cleaners. The usual ingredients include the builders, like 
alkaline substances (e.g. potassium and sodium carbonate, sodium 
silicate); complexing agents (e.g. sodium diphosphate, sodium 
triphosphate, nitric acetic acid (NTA), nitrilo trimethyl phosphonic acid, 
2 phosphonobutane-1,2,4-tricarboxylic acid,1-hydroxyethane-1,1 
diphosphonic acid, N-(2-hydroxyethyl) imino diacetic acid, ethylene 
diamino tetra acetic acid (EDTA), 1,2,3,4 cyclopentane tetracarboxylic 
acid, citric acid, o-carboxymethyl tartaric acid, o-carboxymethyl 
oxysuccinic acid); and ion exchangers (e.g. poly(acrylic acids), 
poly(acrylic acid coalkylalcohols), poly(acrylic acid comaleinic acid), 
poly (.alpha.-hydroxy acrylic acids), poly (tetramethylene-1,2 
dicarboxylic acids), poly (4-methoxytetramethylene-1,2 dicarboxylic 
acids), sodium aluminium silicates). 
Furthermore, the usual ingredients include among others bleaching 
substances, with the exception of chlorine-containing compounds (e.g. 
perborate); bleach activators (e.g. tetra acetyl glycoluril, tetra acetyl 
ethylene diamine (TAED), sodium-p-iso nonanoyl oxybenzene sulphonate 
(iso-NOBS); bleach catalysts and bleach stabilisers. 
Other possible ingredients could include additives such as enzymes (e.g. 
serin proteases, metalloproteases, SH-proteases, carboxyproteases, 
amylases, lipases); so-called "soil anti-redeposition agents" (e.g. 
carboxy methyl cellulose derivatives (CMC), carboxy methyl starch (CMS); 
foam regulators (e.g. fatty acid amides, fatty acid alkanol amides, 
betaine, sulpho betaine, alkyl poly glycosides, alkyl benzene sulphonates, 
alkyl sulphonates, fatty alcohol ethoxylates and/or propoxylates); 
corrosion inhibitors (e.g. soluble sodium silicate); perfumes; colorants; 
fillers (e.g. sodium sulphate); and formulating additives (e.g. alkyl 
benzene sulphonates, urea, alcohols, polyglycol ethers). 
With the indicated amounts of (i) to (iii), and by adding up to 100 wt. % 
with water, it is possible to produce a pre-concentrate of a chlorine-free 
alkaline foam cleaner, which can be used not only as a pre-concentrate, 
but also directly as an application concentrate, provided the water 
content exceeds 85 weight per cent. 
The other component of the two component system to be used according to the 
invention is standard hydrogen peroxide solution. For this purpose it is 
particularly preferred, in order to produce the alkaline hydrogen peroxide 
foam, to dose 30% H.sub.2 O.sub.2 solution to the chlorine-free alkaline 
foam cleaner, whereby the amount is selected in such a way that the 
application concentration with respect to the H.sub.2 O.sub.2 
concentration in the hydrogen peroxide cleaner is between 0.1 and 1 weight 
per cent. The H.sub.2 O.sub.2 amount is preferably 0.2-0.6, especially 
preferred for the purpose is 0.3-0.5 weight per cent. 
As already mentioned, both solutions are most advantageously dosed 
separately by means of an injector system, so that the application 
concentrations may be individually adjusted to the degree and type of 
soiling present. This measure can be realised in an extremely effective 
way by using a special injector system. 
Therefore, the object of the invention is also a device for performing the 
process, enabling separate dosing of both solutions. Through the special 
design of the turbulence chamber and the way the compressed air is added, 
particularly an improved foam structure is obtained. Apart form this, 
surprisingly also a particularly fine and long-lasting foam was obtained. 
Following hereafter, the invention is explained in more detail by means of 
examples and comparative examples. 
The cleaning performance of a foam cleaning system according to the 
invention was tested on standard types of soiling, whereby it was 
surprisingly shown that the system according to the invention surpassed 
commercially available alkaline foam cleaners containing chlorine as 
regards dirt removal. The tested standard types of soiling consisted of: 
1. Grease/flour soiling 
with 
30% molten lard 
30% wheat flour 
3 % corn flour 
37% distilled water 
2. mashed chicken liver 
3. milk paste 
with 
60% skimmed milk powder 
40% distilled water 
Test procedure: 
1. A clean, dry stainless steel plate, with dimensions 10.times.10 cm, is 
weighed. 
2. The standard soiling is applied to the plate. Excess soiling is removed 
with a serrated knife. 
3. After 2 hours drying at 40.degree. C., the plate is weighed again. 
4. The plate is immersed in 5% test solutions and stored during various 
periods of time, depending on the type of soiling: 
grease/flour 60 minutes 
chicken liver 30 minutes 
milk 15 minutes 
5. At the end of each test period, the plate is removed from the solution 
and immersed for 30 seconds in distilled water, to remove residual 
solution. 
6. The plate is dried at 40.degree. C. during the night and weighed again. 
7. Subsequently, the percentage removed dirt is calculated. 
All tests are checked by means of double samples and controlled by means of 
a reference sample. If the reference sample deviates more than 10% from 
the average values, the test is repeated. 
The commercially applied foam cleaners used for comparison purposes contain 
next to polyacrylates for hardness stabilising: 
______________________________________ 
Sample A 
Sample B 
______________________________________ 
Chlorine bleach 20% 17% 
Alkali hydroxide 5% 8% 
Sodium tripoly-phosphate 4% 
Alkyl amine oxide 3% 3% 
______________________________________ 
The cleaning results which can be achieved with these are not as good as 
the dirt removal obtained with the present system: 
______________________________________ 
grease / 
flour chicken milk 
% removed dirt soiling liver soiling 
______________________________________ 
Sample A (5%) 34.7 42.6 65.6 
Sample B (5%) 24.6 37.7 58.5 
Present formula (5%)-30% 
73.0 41.5 75.5 
hydrogen peroxide 
solution (1%) 
______________________________________ 
Microbiological activity 
The foam system described possesses, apart from a cleaning activity, also a 
microbiological activity, which is unexpectedly enhanced as compared with 
the individual components. The microbiological behaviour was tested by 
means of a modified European suspension test based on two test germs which 
frequently occur in the food industry, staphylococcus aureus and 
pseudomonas aeruginosa, and compared with a 30% hydrogen peroxide solution 
at pH 8 (see K. H. Wallhauser, `Praxis der 
Sterilisation-Desinfektion-Konservierung`, 4th ed., Georg Thieme Verlag, 
Stuttgart, 1988) and also compared with a commercially available alkaline 
foam cleaner. The latter contains, besides hardness stabilisers, about 11% 
alkali hydroxide and 3% alkyl amine carboxylate. 
______________________________________ 
Staphylo 
Concentra 
Treatment 
coccus Pseudomonas 
Log reduction 
tion (%) time (min) 
aureus aeruginosa 
______________________________________ 
H.sub.2 O.sub.2, pH 8 
1 60 2 4 
Sample C 5 5 &lt;2 &gt;6 
present formula 
5 + 1 15 &gt;6 &gt;6 
+ 30% hydrogen 
peroxide 
solution 
______________________________________ 
An example of the realisation of the injection device for carrying out the 
process according to the invention is explained in further detail, with 
reference to the drawings, following hereafter.

DETAILED DESCRIPTION OF THE EMBODIMENT 
The injection device shows a hexagonally shaped metal housing body 1, for 
accepting a jet assembly 2, which is screwed into an axial body boring 3. 
The jet assembly 2 includes a jet duct 4 which is shaped as a propulsion 
jet with a cone shaped section 4a and a cylindrical section 4b. A flow 
channel 5 designed as collecting jet is connected onto the propulsion jet 
4, which flow channel shows a first cylindrical section 5a in the 
direction of flow, which passes into a second cylindrical section 5b of 
which the flow cross-section is larger than that of the first section. In 
doing so, the first section 5a of the flow channel 5 which is designed as 
a collection jet shows a larger flow cross-section than the cylindrical 
channel 4b of the propulsion jet 4. 
In the direction of flow, immediately after propulsion jet 4, the jet 
assembly 2 shows a circular groove 6, so as to form a circular space 7 in 
housing body 1 in which two inlet bores 8, 9 terminate, which bores run 
transversally with respect to the axial boring in the housing. For 
connecting the tubes, which are not shown in the figures, two connections 
10, 11 are provided, which are bolted to the injector body 1 and each of 
which are showing a butterfly valve with adjusting screw 10a, 10b and a 
return valve. The circular space 7, in which the inlet bores 8, 9 
terminate, is placed, via a transverse passage boring 12, immediately 
behind propulsion jet 4 in the direction of flow, and is connected to the 
flow duct of collection jet 5 and is laterally sealed against body 1 by 
means of two sealing rings 13, 14 which are fitted into two circular 
grooves of the jet assembly. 
The rear section of the axial body boring in the direction of flow shows a 
larger cross-section than the middle section. This section forms a 
cylindrical turbulence chamber 15, in which the cylindrical body 16 of jet 
assembly 2 extends. Above the outlet orifice 16a of jet assembly 2, the 
injector body 1 shows a boring 17 which runs transversely and which is 
blocked on one side by a stopper 18. A connector 19 for a compressed air 
feed hose is screw fitted into boring 17 on the other side of the housing 
body. 
An inlet channel 20 with a cone shaped and a cylindrical section is 
provided in the housing body in the direction of flow ahead of the 
injection assembly 2, which passes into the cylindrical section of the 
flow channel 4 of the propulsion jet. 
The injection device operates as follows. Water under high pressure is fed 
through inlet 20 to the injector. Because of the reduction of the flow 
cross-section in propulsion jet 4, the flow speed of the transport medium 
is increased. The water leaving propulsion jet 4 sucks the foam cleaning 
agent which is fed through inlet boring 8 into the circular space 7 and 
the hydrogen peroxide solution which is fed via the inlet boring 9 through 
the transverse boring 12 into jet assembly 2, so that the fluids are mixed 
and are flowing from the jet assembly into the turbulence chamber 15, 
where the foam forming starts through the feeding of compressed via the 
compressed air connection 19. The dosing of both solutions may be 
performed thereby separately by means of the adjustment screws 10a, 11a. 
The cleaning foam is drained away by means of a tube which is not shown in 
the figures and which is connected to outlet 21 of the injector. Because 
the compressed air which is fed above the outlet orifice of the jet 
assembly into the circular space of the turbulence chamber 15, which is 
formed by the walls of axial boring 2 and the jet body 16, is directed 
sideways by the jet body, the flow of air has the same flow direction as 
the flow of fluid. Therefore foaming is improved and the use of chemicals 
is reduced.