DE102011000889A1 - Detergent, useful for dishwashing, and for the machine cleaning of dishes comprises enzymes comprising e.g. amylases, borax, a phosphoric acid ester, a complexing agent, a solubilizer, nonionic surfactants, propylene glycol and water - Google Patents

Abstract

Detergent, comprises: 0.5-2 wt.% of one or more enzymes comprising proteases, lipases or amylases; 0.1-2 wt.% of borax; 0.5-3 wt.% of a phosphoric acid ester; 10-30 wt.% of a complexing agent; 10-30 wt.% of a solubilizer; 2-10 wt.% of nonionic surfactants; 10-30 wt.% of propylene glycol; and the balance water. An independent claim is included for a method for the machine cleaning of dishes, comprising dispensing a neutral cleaning agent into the main cleaner tank of the dish washing dispenser, and flushing the obtained solution on the dishes, where the process is carried out with no prepurifying step with a separate cleaning agent.

Description

The present invention relates to the field of machine washing dishes. In particular, the invention relates to an enzymatic detergent for automatic dishwashing, a process using the same and such a method, with which the control of the present detergent amount is possible.

Washing items in a commercial dishwasher requires the use of powerful detergents. The use of enzymes facilitates the detachment of food residues adhering to the items to be washed, which as a rule are hydrophobic substances and in particular contain protein, starch, fat and cellulose. By their use can be largely dispensed with aggressive chemical agents and both the environment, the staff and the dishes are spared.

WO93 / 21299 (Procter & Gamble) describes a thixotropic liquid agent for dishwashing dishes in automatic dishwashers using enzymes. The composition contains 0.001% to 5% detersive enzymes, 0.1% to 10% of a thickener, 0.001% to 10% propylene glycol, 0.01% to 40% surfactant, and sufficient pH adjustor, including borax, wherein the agent is in the Essentially free of chlorine bleach and silicate.

EP 1 657 297 A1 describes a machine cleaning process for dishes, wherein for pre-cleaning always a freshly prepared detergent solution is sprayed separately on the dishes finely divided. In the main rinsing tank the cleaning of the ware is done with a "hard" jet. Here, the cleaner component is in the wash liquor, which is permanently circulated, as long as items to be washed is in the dishwasher. Subsequently, the cleaner in the final rinse zone is rinsed from the items to be washed. This is done with fresh water, which flows into the main rinse tank. EP 1 657 297 A1 describes that an alkaline or acidic cleaner solution and alkaline products for the main cleaning have previously been used for the separate spraying.

It has been found that conventional dishwashing processes, in particular for industrial installations, generally consist of several rinsing steps, a separate cleaning agent being used for each of these rinsing steps. The elimination of a multi-stage rinse process represents an advance in the field of commercial dishwashing technology because fewer dosing devices are required and the overall process is simplified and more controllable. So far, there is no rinsing method, in particular commercial dishwashing method, in which the items to be washed are treated and cleaned in a single step because it was difficult to formulate a cleaning agent which satisfies these claims. Previously required extreme pH values for cleaning liquors with strong cleaning power are incompatible with most enzymes. It is to be understood that such a detergent, which already contains enzyme, must be substantially neutral (pH about 7), i. H. at a pH of 6-8. From this requirement, however, there is also the difficulty that the amount of detergent can not be tracked by titration in a conventional manner, namely via acid-base titration.

The object of the present invention is therefore to provide a one-stage dishwashing process, the associated enzymatic cleaning agent and a detection method for the present detergent quantity included in the dishwashing process.

The present object has been achieved by the cleaning agent according to claim 1, the method according to claim 10 and the combination method according to claim 11. Preferred embodiments are described in the dependent claims.

The present invention therefore relates to a dishwashing detergent, comprising:
one or more enzymes selected from proteases and amylases in an amount of 0.5 to 2% by weight;
Borax in an amount of 0.1 to 2% by weight;
Phosphoric acid ester in an amount of 0.5 to 3 wt .-%;
Complexing agents in an amount of 10 to 30% by weight;
Solubilizer in an amount of 10 to 30 wt .-%;
nonionic surfactants in an amount of 2 to 10% by weight;
Propylene glycol in an amount of 10 to 30 wt .-%, and
as rest water.

In particular, the present invention relates to a dishwashing detergent, comprising:
one or more enzymes selected from proteases and amylases in an amount of 1 to 1.3% by weight;
Borax in an amount of 0.2 to 1% by weight;
Phosphoric acid ester in an amount of 0.8 to 2 wt .-%;
Complexing agents in an amount of 12 to 20% by weight;
Solubilizers in an amount of 15 to 25 wt .-%;
nonionic surfactants in an amount of 4 to 8% by weight;
Propylene glycol in an amount of 16 to 27 wt .-%, and
as rest water.

• a) Dosieren eines wie vorstehend beschriebenen neutralen Reinigungsmittels in den Hauptreinigertank der Geschirrspülanlage mittels Dosiergerät, und
• b) Aufspülen der erhaltenen Lösung auf das Spülgut, dadurch gekennzeichnet, dass dem Verfahren kein Vorreinigungsschritt vorausgeht.

The present invention also relates to a method of machine cleaning dishes comprising

• a) dosing a neutral detergent as described above in the main cleaning tank of the dishwashing system by means of dosing, and
• b) rinsing the solution obtained on the dishes, characterized in that the process is preceded by no pre-cleaning step.

The cleaning composition according to the invention shows superiority over conventional detergents, especially when used against starch and protein contamination. In addition, significant economic benefits are achieved by the one-step dishwashing process.

1 illustrates the range of calibration required in the lower concentration range to determine the amount of detergent, and

2 illustrates the calibration series required to determine the amount of detergent in the upper concentration range;

3 shows a comparative color chart for use in a detection method for detecting a concentration of the detergent of the invention.

The components of the cleaner according to the invention are explained below.

enzymes

Enzymes have long been used as a washing aid. Enzymes are biocatalysts which, in an environment which is optimal for them, in particular split organic substances and thus make them accessible to a solubilization process. The substance to be split is called substrate. In the case of dishwashing these are the food particles that adhere to the dishes. Leftovers contain mainly proteinaceous, starchy and fatty substances. Is z. If, for example, the proportion of vegetables in the food residues is high, a proportion of cellulose can also be detected. Depending on the substrate special enzymes can be used. Proteins can be used to cleave proteins and thus make them easier to remove from the dishes and to achieve solubilization. It should be repealed in the first place the liability for items to be washed. Starchy food particles can be dissolved by amylases and then removed from the dishes. Increasingly, especially in the textile sector, lipases are also used which split the fats and make them more accessible to emulsification, together with detachment from the items to be washed. Ultimately, it is also possible to use cellulases which, in particular, can split cellulosic food residues and detach them from the dishes. A further effect of the use of these enzymes is that the progressive enzymatic degradation of protein, starch, fat and / or cellulose also causes progressive "liquefaction" of the dispersed food residues, thereby preventing the parts of a dishwashing plant from increasing deposits and finally from clogging provided the enzymes can continue to work.

proteases

Enzymes that cleave the amide bonds in protein substrates are classified as proteases or (interchangeably) as peptidases. Bacteria of the Bacillus species secrete two extracellular protease species, a neutral or metalloprotease, and an alkaline protease, which is functionally a serine endopeptidase, called subtilisin. A serine protease is an enzyme that catalyzes the hydrolysis of peptide bonds and that has an essential serine residue at the active site. The bacterial serine proteases have molecular weights in the range of 20,000 to 45,000. They are inhibited by diisopropylpropylfluorophosphate, but unlike metalloproteases, they are resistant to ethylenediaminetetraacetic acid (EDTA) (being stabilized by calcium ions at high temperatures). They hydrolyze simple terminal esters and their activity is similar to that of eukaryotic chymotropin, which is also a serine protease.

Commercial protease preparations for commercial use are subtilisin ^®, Maxacal ^®, Maxatase ^® (Gist-Brocades), Alcalase ^®, Savinase ^®, Esperase ^®, Durazym ^®, Novozym ^® (Novo Industri A / S), Purafect ^® (Genencor Int.) , Opticlean ^®, Optimase ^®, Maxapem ^® (Solvay Enzymes), Bioprase ^® (Nagase Biochemicals), Godo-Bap ^® (Godo Shusei), Wuxi ^® (Wuxi Snyder) and Protosol ^® (Advance Biochemicals).

amylases

Amylases, also referred to as diastases, are enzymes belonging to the hydrolases capable of degrading starch (amylopectin and amylose) directly or via dextrins to maltose and glucose. A distinction is made between α-, β- and γ-amylases; the latter two are commonly referred to as saccharogenic, d. H. saccharifying amylases. The activated by chloride ion α-amylases split starch first into larger fragments (dextrins), then into oligosaccharides. They lower the viscosity of a starch solution. An iodine-starch complex is lightened by its effect. Depending on the origin, the α-amylases have different molecular weights (15,000-97,000), pH activity ranges (3.5-9), temperature optima (45 to 90 °), inactivation temperature (60-100 °) and different cleavage products. The technical α-amylases obtained from bacteria, fungi, pancreatic glands and germinated cereals (malt) are used industrially in detergents.

A known commercial amylase preparation for commercial use is Termamyl ^® by Novo Industri A / S.

In the present invention, a total of 0.5 to 2 wt .-% enzyme mixture are used. Preferred is an amount of 1 to 1.3 wt .-%. When the enzymes are used singly, the amount of proteases is 0.25 to 1% by weight, preferably 0.3 to 0.5% by weight. The amount of amylases is 0.4 to 1.4 wt .-%, preferably 0.7 to 0.9 wt .-%.

borax

Borax, the chemical name is disodium tetraborate, Na ₂ B ₄ O ₇ · 10xH ₂ O, is a crystalline substance which is moderately soluble in cold water with a weakly alkaline reaction, well soluble in boiling water and insoluble in ethanol. The stability of the enzymatic ingredients of detergent formulations, especially liquids in which the ingredients are in close contact with each other, is a major problem in the preparation of detergent compositions. Borax inhibits the loss of activity of many beneficial detergent components. For example, proteases in liquid formulations have stability problems due to self-digestion, ie, "cannibalism." However, this effect can be controlled by the use of small amounts of borax (<2 wt .-%). During the washing process, the borax, which forms a protective complex with the enzyme, is released again, so that the enzyme can carry out its function again. Borate-polyol complexes also serve as enzyme stabilization systems and have been found to be effective in protecting amylases, lipases and cellulases from attack by proteases.

In the present invention, 0.1 to 2% by weight, preferably 0.2 to 1% by weight, more preferably 0.3 to 0.5% by weight of borax is used.

organophosphate

Phosphoric acid esters are organic compounds of phosphoric acid with generally aliphatic alcohols. Owing to the three OH groups of the phosphoric acid, different degrees of esterification are possible: monoesters, diesters and triesters, the first two still having two or one acid group which is or are accessible to salt formation. Mono- or diesters of phosphoric acid are acidic and have similar phosphatizing properties as phosphoric acid. Due to the additional alcohol chain they are far less corrosive. Short-chain phosphoric acid esters which z. B. sold under the trade name Hordaphos ^® CC, react in aqueous solution as proton donors and are far less corrosive than free mineral acids. They are therefore a good choice as a suitable basic substance for a cleaning, which may also have to take place under non-alkaline conditions. In particular, they can also Remove limescale deposits. In this regard, the combination of strong but gentle cleaning power and strong corrosion-inhibiting effect is advantageous.

For the present invention, Hordaphos ^® CC MS proved to be particularly effective. Hordaphos ^® CC MS has a viscosity at 20/25 ° C of 200 mPa.s and consists essentially of Phosphorsäuremonomethylester.

In the present invention, 0.5 to 3 wt .-%, preferably 0.8 to 2 wt .-%, particularly preferably 1 to 1.4 wt .-% phosphoric acid ester is used.

complexing

Complexing agents have the task of binding water hardness and, if appropriate, side-group metal ions which have negative effects on other constituents of the cleaning agent.

In the present invention, in particular, the sodium salt of methylglycinediacetic acid (MGDA) is advantageously used over other complexing agents. A trade name for this is Trilon ^® (BASF). Or will it be with the same advantage GLDA 4 Na ^®, ie L-glutamic acid-N, N-diacetic acid tetrasodium salt (Akzo Nobel) was used.

In the present invention, 10 to 30 wt .-%, more preferably 12 to 20 wt .-%, particularly preferably 14 to 16 wt .-% complexing agent used.

solubilizers

Solubilizers are used in surfactant formulations, such as. As the present detergent, for substances that are not compatible with each other, used. They are also called solubilizers or solubilizers and lower the cloud point.

In the present invention, sodium cumene sulfonate is preferably used. A commercial product is for example Stepanate ^® SCS-40-E (liquid) ^® or Stepanate SCS-93 (crystalline) from the Fa. Neochem or sodium cumene sulfonate (40%) from the Fa. Silbermann.

In the present invention, a solubilizer of the above-defined form is used in an amount of 10 to 30% by weight, preferably 15 to 25% by weight, and more preferably in an amount of 18 to 22% by weight.

surfactant

An important effective ingredient of a dishwashing detergent is a surfactant. Surfactants reduce the surface tension of a liquid or the interfacial tension between two phases, thus allowing the formation of dispersions. Therefore, they cause that actually immiscible substances can be finely mixed and therefore cause the washing effect by dispersing or emulsifying the generally hydrophobic food particles in the aqueous wash liquor in the present case.

There are a variety of different surfactants. Generally, they are classified according to their chemical nature into ionic, nonionic and amphoteric surfactants. Nonionic surfactants are used for the present invention, in particular those of the group of alkoxylated, in particular ethoxylated fatty alcohols. These compounds are usually obtained by adding an alkylene oxide such as ethylene oxide or propylene oxide to the OH group of a fatty alcohol, ie, an alcohol having usually 8 to 22 carbon atoms. Preferred in the present invention are fatty ethoxylates, that is, compounds obtained by adding one to several -CH ₂ CH ₂ -O- moieties (either by addition with ethylene oxide or by etherification with glycol) to a fatty alcohol.

In the present invention Plurafac ^® grades preferably be used, in particular Plurafac LF 221 and / or LF 231st

Plurafac ^® LF 221 is a liquid with a surfactant content of about 95% and a water content of about 5%. The cloud points after DIN EN 1890 are about 34 ° for method A, method B about 24 °, method D about 48 ° and method E about 44 ° C.

The number of water according to DIN EN 12836 is about 17. The pH is neutral. The density at 23 ° C is 1. The pour point is about 5 ° C. The Brookfield viscosity ( EN 12092 , Brookfield LVT) at 23 ° C is about 100, at 10 ° C about 5000 and at 0 ° C> 10 ⁵ . The net effect (after EN 1772 , at least Water, 2 g of sodium carbonate / l) at 23 ° C with 0.5 g of surfactant about 75, at 23 ° C with 1 g of surfactant about 30, at 23 ° C with 2 g of surfactant about 15, at 70 ° C with 0.5 g of surfactant> 300, at 70 ° C with 1 g of surfactant> 300, and at 70 ° C with 2 g of surfactant about 100. The surface tension (acc EN 14370 , 1 g / l dist. Water, 23 ° C) is about 30.

Plurafac ^® LF 231 is a liquid with a surfactant content of 100%. The cloud points after DIN EN 1890 are about 35 ° for method D, and method E about 28 ° C.

The number of water according to EN 12836 is about 12. The pH is about 6. The density at 23 ° C is about 0.96. The pour point is about -5 ° C. The Brookfield viscosity ( EN 12092 , Brookfield LVT) at 23 ° C is about 45, at 10 ° C about 100 and at 0 ° C about 400. The net effect (acc EN 1772 , at least Water, 2 g of sodium carbonate / l) at 23 ° C with 0.5 g of surfactant is about 100, at 23 ° C with 1 g of surfactant about 40, at 23 ° C with 2 g of surfactant about 20, at 70 ° C with 0.5 g of surfactant> 300, at 70 ° C with 1 g of surfactant> 300, and at 70 ° C with 2 g of surfactant> 300. The surface tension (acc EN 14370 , 1 g / l dist. Water, 23 ° C) is about 29.

The cloud point is according to DIN EN 1890 as determined below:
Method A: 1 g of surfactant + 100 g of dist. water
Method B: 1 g of surfactant + 100 g of NaCl solution (c = 50 g / l)
Method D: 5 g of surfactant + 45 g of butyl diglycol solution (c = 250 g / l)
Method E: 5 g of surfactant + 25 g of butyl diglycol solution (c = 250 g / l)

In the present invention, a total of 2 to 10 wt .-%, more preferably 4 to 8 wt .-% and particularly preferably 4.5 to 7 wt .-% surfactant used in total. If the surfactant is present as a mixture of different fatty alcohol ethoxylates, the ratio is 9: 1 to 1: 9, preferably 8: 3 to 3: 8, more preferably 2.5: 1 to 1: 2.5 of the fatty alcohol ethoxylate with the higher Cloud point to the fatty alcohol ethoxylate with the lower cloud point. Particularly preferred is the ratio 3: 1, especially 2.5: 1.

propylene glycol

Propylene glycol, also known as 1,2-propanediol, is a chiral compound in the form of a clear, colorless liquid, which is usually traded as a racemate. Propylene glycol is miscible with water and ethanol. It is used as a solvent and filler and thus has a certain cleaning effect. In addition, it can contribute to the stabilization of enzyme systems.

In the present invention, the amount of propylene glycol is 10 to 30% by weight, preferably 16 to 27% by weight, more preferably 21 to 25% by weight.

The range values of the amounts given above for the respective components can be combined as desired for the composition of a cleaning agent according to the invention, provided that all components of the cleaning agent total less than 100 wt .-% and a desired effect is obtained. All these combinations are expressly disclosed.

The invention also relates to a dishwashing process, comprising a) metering a neutral detergent as described above into the main dishwashing tank of the dishwashing plant by means of a metering device, and b) rinsing the resulting solution onto the wash ware, the process not preceded by a precleaning step with a separate detergent. The process according to the invention is therefore, as far as the number of dish washing process steps taking place, a one-step process, ie. H. there is no upstream pre-cleaning step with a separate cleaning agent.

Furthermore, the invention consists in the combination of the above-described purification method with a determination of the (still) present amount of active cleaner, in particular the amount of enzyme. In non-enzymatic processes, the amount or suitability of the rinsing liquor used can be titrated with acid. In conventional commercial dishwashing z. For example, in addition to the enzymatic cleaning solution, the usually strongly alkaline precleaning solution also reaches the rinsing liquor, so that the enzyme action present there is generally no longer available.

The determination method used in the method of the invention is based on the addition of starch solution to a sample of rinse liquor. After a certain time, in which the Stäke is dismantled, will Added iodine solution and compared the obtained color. The more starch there is, the darker the color. Depending on the size of the dishwasher, the measurement can be carried out by automated sampling and addition of the starch solution and a little later the iodine solution z. B. in the flow-injection method or in the continuous-flow method with colorimetric or photometric evaluation.

Examples

The following examples illustrate the invention. All percentages are by weight unless otherwise indicated.

example 1

A detergent was prepared by mixing in a conventional manner known per se. component weight Enzyme Savinase ^® Ultra 16 L 0,400 Enzyme Termamyl ^® Ultra 300 L 0,800 Borax techn. gran. 0,400 Phosphoric acid ester CCMS 1,200 Trilon ^® M 14,997 Na cumene sulphonate 40% liquid 19.996 Plurafac LF 221 ^® 4,999 Plurafac ^® LF 231 2,000 1,2-propylene glycol 23.661 Water perm. 31.549

The agent was used in a commercial commercial dishwashing system, which could be dispensed with a pre-rinse with separate detergent. The results were outstanding, in particular soiling by starch and protein had been eliminated much better than in a known manner.

The economic savings effects were also clear.

Example 2

In a similar manner to Example 1, a further cleaning solution was formulated, in which case in particular GLDA Na4 ^® was used as a liquid complexing agent. component weight Enzyme Savinase ^® Ultra 16 L 0,399 Enzyme Termamyl ^® Ultra 300 L 0.799 Borax techn. gran. 0,399 Phosphoric acid ester CCMS 1,198 GLDA Na4 ^® liquid 14,980 Na cumene sulphonate 40% liquid 19.973 Plurafac LF 221 ^® 4,993 Plurafac ^® LF 231 1,997 1,2-propylene glycol 23.635 Water perm. 31.625

Similar outstanding results could be obtained as for Example 1. In particular, the removal of starch and protein was excellent.

Example 3

Determination of a series of calibrations for determining the enzyme activity present, in which case amylase represents the lead enzyme.

First, exactly 50 ml of rinsing solution are removed and placed in a large titration vessel. The temperature of the rinse liquor must be at least 55 ° C. For this purpose, add exactly 4.0 ml of starch solution, mix and allow to act for exactly 60 sec. It should be noted that if the exposure time is not met, the content can not be determined accurately enough. During the exposure time, a 1 ml syringe is filled with 0.4 ml of iodine solution. Immediately after the reaction time 0.4 ml of iodine are added and mixed. You wait exactly 5 minutes. Now with a standard color chart, z. As a photo, compared to which of the standard shades of the obtained hue is most similar. An example of a comparison color chart is in 3 to see. This then corresponds to the concentration. If there is a hue between those shown in the photo, the mean is estimated. In principle, the brighter (yellow) the color, the more cleaning agent according to the invention is contained. For the calibration series 1.0; 1.5; 2.0 and 2.5 ml / l of detergent are added to 4.0 ml of starch solution, for the calibration series 2.5; 3.0 3.5 and 4.0 ml / l are used 7.0 ml of starch solution. The quoted quantities are only guide values. The concentrations of the starch solution, the iodine solution (if necessary, iodine / KI solution) can all be chosen so that the colorimetric effect is achieved in the field of application.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 93/21299 [0003]
• EP 1657297 A1 [0004]

Cited non-patent literature

• DIN EN 1890 [0036]
• DIN EN 12836 [0037]
• EN 12092 [0037]
• EN 1772 [0037]
• EN 14370 [0037]
• DIN EN 1890 [0038]
• EN 12836 [0039]
• EN 12092 [0039]
• EN 1772 [0039]
• EN 14370 [0039]
• DIN EN 1890 [0040]

Claims (11)

Detergent for dishwashing installations, comprising: one or more enzymes selected from proteases, lipases and amylases in an amount of 0.5 to 2% by weight; Borax in an amount of 0.1 to 2% by weight; Phosphoric acid ester in an amount of 0.5 to 3 wt .-%; Complexing agents in an amount of 10 to 30% by weight; Solubilizer in an amount of 10 to 30 wt .-%; nonionic surfactants in an amount of 2 to 10% by weight; Propylene glycol in an amount of 10 to 30 wt .-%, and as rest water. A detergent according to claim 1, comprising: one or more enzymes selected from proteases, lipases and amylases, in an amount of 1 to 1.3% by weight; Borax in an amount of 0.2 to 1% by weight; Phosphoric acid ester in an amount of 0.8 to 2 wt .-%; Complexing agents in an amount of 12 to 20% by weight; Solubilizers in an amount of 15 to 25 wt .-%; nonionic surfactants in an amount of 4 to 8% by weight; Propylene glycol in an amount of 16 to 27 wt .-%, and as rest water. A detergent according to claim 1 or claim 2 wherein the enzyme is in the form of a mixture of protease, lipase and amylase and the mixture comprises from 0.25 to 1% by weight of protease and from 0.4 to 1.4% by weight of amylase. Cleaning agent according to one of the preceding claims, wherein the phosphoric acid ester used is a product which comprises substantially phosphoric acid monomethyl ester. Cleaning agent according to one of the preceding claims, wherein as complexing agent methylglycinediacetic acid and / or L-glutamic acid-N, N-diacetic tetrasodium salt is used. Cleaning agent according to one of the preceding claims, wherein sodium cumenesulfonate is used as solubilizer. Cleaning agent according to one of the preceding claims, wherein at least one fatty alcohol ethoxylate is used as nonionic surfactant. A detergent according to claim 7, wherein fatty alcohol ethoxylate is a mixture of two or more fatty alcohol ethoxylates. A cleaning composition according to claim 8, wherein the fatty alcohol ethoxylate mixture comprises two components and these are present in a ratio of 9: 1 to 1: 9 from the higher cloud point fatty alcohol ethoxylate to the lower cloud point fatty alcohol ethoxylate. A method of machine cleaning dishes comprising a) dosing a neutral detergent according to one of the preceding claims in the main cleaning tank of the dishwashing by means of dosing, and b) rinsing the solution obtained on the dishes, characterized in that the process precedes no pre-cleaning step with a separate detergent. The method of claim 10, wherein the detergent is tested manually or mechanically at intervals as to whether the amount of cleaning agent is within the prescribed range and / or whether the rinse liquor still has sufficient cleaning power by an exact amount of sample rinsing liquor is removed, a exact amount of starch solution is added, after a period of time iodine solution is added and after a precise time, the resulting color is compared visually with a standard or measured photometrically.

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