How to wash dishes

Abstract

To suppress increase in recontamination of dishes and the like by contaminants in washing liquid when washing dishes under a washing condition that contaminants are mixed in the washing liquid by using an automatic dishwasher equipped with a washing liquid tank for storing washing liquid and a washing tank where the washing liquid supplied from the washing liquid tank is caused to be brought into contact with the dishes.SOLUTION: At least a part of washing liquid used for washing dishes is recovered in a washing liquid tank, and is reused at least as a part of new washing liquid. The reused washing liquid is caused to contain (a) a protein degrading enzyme (hereinafter called component (a)), and the washing liquid is brought into contact with dishes after an enzymatic activity value of the washing liquid is caused to become 5 U / mL or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for washing tableware, and more particularly to a method for washing tableware using an automatic dishwasher. [Background technology]

[0002] BACKGROUND ART In recent years, water-saving automatic dishwashers that use half or less of the rinsing water of conventional automatic dishwashers have become popular. Automatic dishwashers include conveyor-type machines in which dishes and the like are placed on a conveyor, door-type machines in which dishes and the like are loaded and unloaded by opening and closing a door, and under-counter-type machines installed under a counter. Hotels, meal preparation facilities, restaurants, izakayas, convenience stores, and the like use an automatic dishwasher of a preferred type depending on the amount of dishes and the installation space, etc. From the perspective of reducing detergent consumption and running costs, efforts are being made to reduce the amount of water used in all automatic dishwashers. For example, automatic dishwashers circulate the cleaning liquid in a cleaning liquid tank to wash dishes and the like, and then collect this cleaning liquid in the cleaning liquid tank for reuse in the next wash, and all or part of the rinse water is flowed into the cleaning liquid tank, causing dirt accumulated in the cleaning liquid tank to overflow and be discharged.

[0003] Patent Document 1 discloses a detergent composition for automatic dishwashers, which contains (A-1) methylglycine diacetate and its alkali metal salt, (A-2) citric acid and its alkali metal salt, and (B-1) a specific nonionic surfactant. Patent Document 2 discloses a liquid detergent composition for hard surfaces to be used in automatic dishwashers, which contains (A) a specific nonionic surfactant, (B) a specific nonionic surfactant, (C) an alkanolamine, (D) an enzyme, (E) an n-hexylglycoside, (F) a calcium additive, and (G) water. Patent Document 3 discloses a detergent composition for automatic dishwashers that contains (a) a specific ester and (b) a bleach activator. Patent Document 4 discloses a dishwasher detergent composition containing (a) a nonionic surfactant, (b) a polymeric chelating agent, (c) a specific weakly acidic to weakly alkaline water-soluble electrolyte, and further a detergent enzyme. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 175659 [Patent Document 2] Japanese Patent Application Publication No. 2018-024723 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-214539 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-154716 Summary of the Invention [Problem to be solved by the invention]

[0005] In water-saving automatic dishwashers, the rinse water is also saved, so the accumulated dirt in the reused washing liquid tends to increase. This tendency is particularly noticeable in commercial automatic dishwashers, which are used for a large number of washes. Furthermore, repeated use and washing of dishes tends to cause dirt to accumulate on the dishes. When dishes and the like are repeatedly washed under washing conditions in which dirt is mixed in the washing liquid, if the recontamination of the dishes and the like by dirt in the washing liquid increases, dirt is more likely to accumulate on the dishes and the like due to repeated washing. Therefore, when automatic dishwashers are used under washing conditions in which dirt is mixed in the washing liquid, it is necessary to suppress an increase in re-contamination of dishes and the like due to dirt in the washing liquid.

[0006] The present invention provides a method for washing tableware, which, when washing under washing conditions in which dirt is mixed in the washing liquid, suppresses an increase in recontamination of the tableware or the like due to dirt in the washing liquid. [Means for solving the problem]

[0007] The present invention provides a method for washing dishes using an automatic dishwasher equipped with a washing liquid tank that contains washing liquid and a washing tub that brings the washing liquid supplied from the washing liquid tank into contact with dishes, the method comprising: This relates to a method for washing tableware, in which at least a portion of the washing liquid used for washing tableware is recovered in a washing liquid tank and reused as at least a portion of new washing liquid, (a) a protease (hereinafter referred to as component (a)) is contained in the reused washing liquid, the enzyme activity of the washing liquid is increased to 5 U / mL or more, and then the washing liquid is brought into contact with the tableware. [Effects of the Invention]

[0008] According to the present invention, there is provided a method for washing tableware that suppresses an increase in re-contamination of tableware, etc., caused by dirt in the washing liquid when washing is performed under washing conditions in which dirt is mixed in the washing liquid. DETAILED DESCRIPTION OF THE INVENTION

[0009] The inventors analyzed the dirt accumulated in the washing liquid of an automatic dishwasher and the components attached to dishes re-contaminated by the dirt in the washing liquid, and found that the composition ratio of the dirt accumulated in the washing liquid differs from the composition ratio of the dirt attached to dishes due to re-contamination. For example, even if the composition ratio of the dirt accumulated in the washing liquid is, in descending order, lipids, proteins, and sugars, the re-contamination components attached to dishes are relatively high in protein dirt. This is thought to be because, when proteins are exposed to high temperatures during the dishwashing process, particularly during the rinsing process, where the amount of protease is extremely small, the proteins become hydrophobic due to thermal denaturation, making them more likely to adhere to dishes. Based on these findings, the inventors conducted extensive research and completed the present invention. The dishwashing method of the present invention involves recovering the washing liquid used in washing and reusing it as a new washing liquid. Proteins in the washing liquid are decomposed before the reused washing liquid is brought into contact with the dishes. This prevents dirt accumulated in the washing liquid from reattaching to the dishes, and also prevents the accumulation of dirt on the dishes even when the dishes are washed repeatedly. That is, when washing under washing conditions in which dirt is present in the washing liquid, the increase in recontamination of the dishes caused by dirt in the washing liquid can be prevented, which is believed to improve the finish of the dishes. Furthermore, when dishes are repeatedly washed and used using reused washing liquid, the adhesion and accumulation of dirt in the washing liquid on parts of the dishes that have not come into direct contact with food, such as the backside of the dishes or a glass used for drinking water, is prevented. As a result, the degree of deterioration in the finish of the dishes is reduced, and the finish of the dishes is believed to be improved.

[0010] The dishwashing method of the present invention is a method for washing dishes using an automatic dishwasher equipped with a washing liquid tank that contains washing liquid and a washing tub that brings the washing liquid supplied from the washing liquid tank into contact with dishes, the method comprising: This is a method for washing dishes, in which at least a portion of the washing liquid used to wash dishes is recovered in a washing liquid tank and reused as at least a portion of new washing liquid, (a) a protease (hereinafter referred to as component (a)) is added to the reused washing liquid, the enzyme activity value of the washing liquid is increased to 5 U / mL or more, and then this washing liquid is brought into contact with the dishes. The enzyme activity value of the cleaning solution may be the enzyme activity value for proteins, that is, the enzyme activity value for protein degradation.

[0011] In the dishwashing method of the present invention, the washing liquid is reused at least once. From the viewpoint of obtaining the effects of the present invention more significantly, the dishwashing method of the present invention preferably reuses the washing liquid at least twice, more preferably at least three times, even more preferably at least four times, and even more preferably at least five times. The more times the washing liquid is reused, the more significantly the effects of the dishwashing method of the present invention are obtained. From the viewpoint of obtaining the effects of the present invention more significantly, the dishwashing method of the present invention is preferably a dishwashing method in which the same dishes are washed two or more times using reused washing liquid, more preferably three or more times, even more preferably four or more times, and even more preferably five or more times. The more times the same dishes are washed using reused washing liquid, the more significant the effects of the dishwashing method of the present invention become. Here, washing the same dishes two or more times using reused washing liquid includes washing the dishes after washing, and then subjecting the used dishes to the next wash.

[0012] First, the component (a) used in the dishwashing method will be described.

[0013] <(a) Protease> Component (a) is a protease. As component (a), one or more proteases selected from proteases and peptidases can be used, with proteases being preferred. Component (a) is not particularly limited as long as it is one typically used in detergent compositions, and examples include pepsin, trypsin, chymotrypsin, collagenase, keratinase, elastase, subtilisin BPN', papain, bromelain, carboxypeptidase A, carboxypeptidase B, aminopeptidase, aspergylopeptidase A, and aspergylopeptidase B. Purified fractions of these enzymes as well as crude enzymes and granulated products thereof can also be used. Commercially available enzymes (protease preparations) include, for example, alkaline proteases such as Ovozyme, Savinase, Evalase, Alcalase, Esperase, Cannase, and Durazyme (registered trademark; manufactured by Novozymes), Maxatase, Maxapem, Maxacal, Propelase, Prafect, and Prafect OX (registered trademark; manufactured by Genencor), Blap (registered trademark; manufactured by Henkel), KAP (manufactured by Kao Corporation), and API21 (manufactured by Showa Denko K.K.), and neutral proteases such as Neutrase (registered trademark; manufactured by Novozymes). Alkaline proteases are particularly suitable for use as component (a).

[0014] Next, the detergent composition for automatic dishwashers (hereinafter referred to as the detergent composition of the present invention) used in the dishwashing method of the present invention will be described.

[0015] <Cleaning agent composition> The cleaning composition of the present invention contains component (a). The cleaning composition of the present invention can contain one or more types of component (a) as described above. In addition to component (a), the cleaning composition of the present invention may contain one or more types selected from (b) an alkaline agent (hereinafter referred to as component (b)), (c) a surfactant (hereinafter referred to as component (c)), and (d) a chelating agent (hereinafter referred to as component (d)).

[0016] Component (b) is an alkaline agent, which may be one or more selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal silicates, and amine compounds. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide. Examples of alkali metal carbonates include sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate. Also, anhydrous sodium carbonate, known as soda ash, may be used as component (b). Examples of alkali metal silicates include sodium silicate and potassium silicate. Examples of sodium silicate include sodium orthosilicate, sodium metasilicate, No. 1 sodium silicate, No. 2 sodium silicate, No. 3 sodium silicate, sodium metasilicate pentahydrate, and sodium metasilicate nonahydrate. Examples of potassium silicate include potassium orthosilicate, potassium metasilicate, potassium A silicate, potassium B silicate, and potassium C silicate. Specifically, crystalline layered sodium silicate (manufactured by Tokuyama Corporation, "Purifeed") can be used as component (b). Amorphous alkali metal silicates may also be used. Alkali metal silicates are also effective as antioxidants for tableware. Examples of the amine compound include alkanolamines. In the present invention, primary alkanolamines are particularly preferred, specifically monoethanolamine. Among these alkaline agents, alkali metal carbonates are preferred. The alkaline agent may be in the form of powder or granules. The particle size and bulk density of the granular agent may be appropriately adjusted by granulation or the like.

[0017] Component (c) is a surfactant. Examples of component (c) include one or more selected from nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. From the viewpoint of cleaning properties, one or more selected from nonionic surfactants and anionic surfactants are preferred, and nonionic surfactants are more preferred.

[0018] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyalkylene dialkyl ethers, polyoxyethylene alkenyl ethers, polyoxyalkylene alkylphenyl ethers, reverse Pluronic block polymers, reverse Tetronic block polymers, sucrose fatty acid esters, sorbitan fatty acid esters, polyethylene glycol fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, polypropylene glycol fatty acid esters, coconut fatty acid diethanolamide, lauric acid diethanolamide, lauric acid myristic acid diethanolamide, myristic acid diethanolamide, oleic acid diethanolamide, palm kernel fatty acid diethanolamide, alkyl glucosides, and amine oxides. From the viewpoint of cleansing properties, polyoxyethylene polyoxypropylene alkyl ethers, reverse Pluronic block polymers, and reverse Tetronic block polymers are particularly preferred. These nonionic surfactants may be used alone or in combination of two or more.

[0019] Component (d) is a chelating agent, and as component (d), one or more chelating agents selected from aminocarboxylic acid-based, hydroxycarboxylic acid-based, phosphoric acid-based, ether carboxylate, and phosphonic acid-based chelating agents can be used.

[0020] Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), methylglycine diacetic acid (MGDA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraminehexaacetic acid (TTHA), glutamic acid diacetic acid (GLDA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethylglycine (DHEG), 1,3-propanediaminetetraacetic acid (PDTA), 1,3-diamino-2-hydroxypropanehexaacetic acid (DPTA-OH), aspartic acid diacetic acid (ASDA), ethylenediaminesuccinic acid (EDDS), and salts thereof.

[0021] Examples of hydroxycarboxylic acid-based chelating agents include malic acid, succinic acid, citric acid, lactic acid, tartaric acid, gluconic acid, and salts thereof. Examples of the phosphoric acid-based chelating agent include tripolyphosphate and hexametaphosphate.

[0022] Examples of the phosphonic acid chelating agent include hydroxyethylidene diphosphonic acid (HEDP), nitrilotrismethylenephosphonic acid (NTMP), phosphonobutanetricarboxylic acid (PBTC), ethylenediaminetetramethylenephosphonic acid (EDTMP), and salts thereof.

[0023] Examples of the salt in the chelating agent include salts of alkali metals such as potassium and sodium, and salts of alkaline earth metals such as magnesium and calcium. Of these, alkali metal salts are preferred, and sodium salts or potassium salts are more preferred.

[0024] In the cleansing composition of the present invention, the concentration of component (a) during use, calculated as enzyme protein, is preferably 0.000005% by mass or more, more preferably 0.000007% by mass or more, even more preferably 0.000009% by mass or more, even more preferably 0.00003% by mass or more, even more preferably 0.00005% by mass or more, even more preferably 0.0001% by mass or more, and even more preferably 0.0002% by mass or more, from the viewpoint of proteolytic performance; and is preferably 0.05% by mass or less, more preferably 0.045% by mass or less, even more preferably 0.04% by mass or less, even more preferably 0.035% by mass or less, and even more preferably 0.03% by mass or less, from the viewpoint of reducing skin irritation. The enzyme protein of component (a) can be quantified, for example, using the Lowry method. For example, a Protein Assay Lowry Kit (manufactured by Nacalai Tespue) can be used to quantify the enzyme protein using the Lowry method.

[0025] The cleaning composition of the present invention has an enzyme activity value of 5 U / mL or more, preferably 6 U / mL or more, more preferably 8 U / mL or more, and even more preferably 10 U / mL or more, during use, from the viewpoint of finish quality; and from the viewpoint of reduced skin irritation, it is preferably 3,000 U / mL or less, more preferably 2,700 U / mL or less, even more preferably 2,500 U / mL or less, and even more preferably 2,000 U / mL or less. The enzyme activity value of the cleaning solution is the enzyme activity value measured under conditions of a reaction temperature of 40°C. The enzyme activity value of the cleaning solution can be measured using PROTASYME AK TABLETS (Megazyme). The enzyme activity value of the cleaning solution to be reused may be the enzyme activity value of the cleaning solution contained in the cleaning solution tank. In the present invention, an enzyme activity value of 5 U / mL or more of the cleaning solution means that the enzyme activity value per mL of cleaning solution is 5 U or more, as determined by the method described below. Furthermore, the enzyme activity value of the cleaning solution may be the enzyme activity value against protein. In the present invention, the enzyme activity value of the cleaning composition (i.e., cleaning solution) during use is a value measured and calculated by the following method. First, 67 mM phosphate buffer (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is placed in a 1.8 mL test tube and kept at 40°C. Next, one PROTASYME AK TABLETS is added and stirred to mix. Next, 0.2 mL of cleaning solution is added and mixed, and the mixture is allowed to react at 40°C for 30 minutes. Next, 1 mL of 10% aqueous citric acid solution is added and mixed, and the mixture is centrifuged (2800 r / min, 15 minutes). The supernatant is then separated as a sample, and the absorbance (590 nm) of the sample is measured. The absorbance change is calculated by subtracting the base absorbance value from the absorbance value of the obtained sample using the following formula. This absorbance change is multiplied by a coefficient (coefficient = 1000) for converting the absorbance change to an enzyme activity value, and the resulting value is defined as the enzyme activity value (U / mL) of the cleaning composition (i.e., cleaning solution). Enzyme activity (U / mL) = (Sample absorbance (590 nm) - Base absorbance (590 nm)) x 1000 The absorbance of the base (590 nm) is measured using the following method. First, 67 mM phosphate buffer (Fujifilm Wako Pure Chemical Industries, Ltd.) is placed in a 1.8 mL test tube and kept at 40°C. Next, one PROTASYME AK TABLETS is added and stirred. Next, 0.2 mL of ion-exchanged water is added and mixed, and the mixture is allowed to react at 40°C for 30 minutes. Next, 1 mL of 10% citric acid aqueous solution is added and mixed, and the mixture is centrifuged (2800 r / min, 15 minutes). The supernatant is collected as the base, and the absorbance of the base (590 nm) is measured.

[0026] When the cleanser composition of the present invention contains component (b), the concentration of component (b) in the cleanser composition of the present invention during use is preferably 0.00010% by mass or more, more preferably 0.0005% by mass or more, and even more preferably 0.0010% by mass or more, from the viewpoint of cleansing performance, and is preferably 0.30% by mass or less, more preferably 0.28% by mass or less, and even more preferably 0.26% by mass or less, from the viewpoint of reduced skin irritation.

[0027] When the cleaning composition of the present invention contains component (c), the concentration of component (c) in the cleaning composition of the present invention during use is preferably 0.00001% by mass or more, more preferably 0.00002% by mass or more, and even more preferably 0.00003% by mass or more, from the viewpoint of cleaning performance, and is preferably 0.075% by mass or less, more preferably 0.070% by mass or less, and even more preferably 0.065% by mass or less, from the viewpoint of blend stability.

[0028] When the detergent composition of the present invention contains component (d), the concentration of component (d) in the detergent composition of the present invention during use is preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more, and even more preferably 0.0004% by mass or more, from the viewpoint of scale deposition-inhibiting performance, and is preferably 0.25% by mass or less, more preferably 0.23% by mass or less, and even more preferably 0.20% by mass or less, from the viewpoint of formulation stability.

[0029] When the detergent composition of the present invention contains component (c), the mass ratio (a) / (c) of the content of component (a) to the content of component (c) is preferably 0.00015 or more, more preferably 0.00017 or more, and even more preferably 0.00020 or more from the viewpoint of proteolytic performance, and is preferably 4.5 or less, more preferably 4.0 or less, and even more preferably 3.0 or less from the viewpoint of detergency. The amount of component (a) is expressed in terms of enzyme protein.

[0030] The pH of the cleaning composition of the present invention at 25°C is preferably 9 or more and 12 or less. The cleaning composition of the present invention, in the form of a 0.1 mass% aqueous solution of the concentrated cleaning composition described below, preferably has a pH of 10 or more and 12 or less at 25°C. The pH of the diluted cleaning liquid can be measured in accordance with JIS K 3362.

[0031] The detergent composition of the present invention may further contain a bleaching agent, an antifoaming agent, a rust inhibitor, a hydrotropic agent, a surface modifier, a fragrance, and the like.

[0032] The cleaning composition of the present invention can be used by diluting a concentrated cleaning composition. The cleaning composition of the present invention can be used by diluting the concentrated cleaning composition so that the concentration of the concentrated cleaning composition is, for example, from 0.01% by mass to 0.5% by mass.

[0033] In the concentrated cleanser composition, the content of component (a) is, in terms of enzyme protein, preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.09% by mass or more, even more preferably 0.10% by mass or more, and even more preferably 0.15% by mass or more, from the viewpoint of proteolysis performance; and preferably 12% by mass or less, more preferably 11% by mass or less, even more preferably 10% by mass or less, even more preferably 9% by mass or less, even more preferably 8% by mass or less, even more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 1% by mass or less, from the viewpoint of reducing skin irritation. The enzyme protein content of component (a) can be quantified, for example, using the Lowry method. For example, a Protein Assay Lowry Kit (manufactured by Nacalai Tespue) can be used to quantify the enzyme protein content using the Lowry method.

[0034] When the cleanser composition of the present invention contains component (b), the content of component (b) in the concentrated cleanser composition is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of cleansing performance, and preferably 70% by mass or less, more preferably 68% by mass or less, and even more preferably 66% by mass or less, from the viewpoint of reduced skin irritation.

[0035] When the detergent composition of the present invention contains component (c), the content of component (c) in the concentrated detergent composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and still more preferably 0.5% by mass or more, from the viewpoint of cleaning performance, and is preferably 15% by mass or less, more preferably 14% by mass or less, even more preferably 13% by mass or less, and still more preferably 10% by mass or less, from the viewpoint of blend stability.

[0036] When the detergent composition of the present invention contains component (d), the content of component (d) in the concentrated detergent composition is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more from the viewpoint of scale adhesion preventive performance, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less from the viewpoint of blend stability.

[0037] The concentrated detergent composition may be in either a solid or liquid form, but is preferably in the form of a solid, i.e., a solid block, granules, powder, or the like, and is more preferably in the form of a powder from the viewpoints of ensuring workability and storage stability of the detergent.

[0038] <How to wash dishes> Next, the dish washing method of the present invention will be described in detail. In the description of the dish washing method, an automatic dishwasher including a washing liquid tank for storing washing liquid and a washing tub for bringing dishes into contact with the washing liquid supplied from the washing liquid tank will be used as an example. Note that the dish washing method of the present invention is not limited to the disclosed embodiment.

[0039] When washing dishes, the cleaning liquid contained in the cleaning liquid tank is sent to the washing tank, and the cleaning liquid is brought into contact with the dishes in the washing tank to wash the dishes. The cleaning liquid contained in the cleaning liquid tank already contains component (a), and at least a portion of the proteins that will be contained in the cleaning liquid from the previous wash have been decomposed before being sent to the washing tank. When washing dishes, component (a) or a detergent composition containing component (a) is added to the washing tank or the cleaning liquid sent to the washing tank, as necessary. Furthermore, when washing dishes, for example, the cleaning liquid can be sprayed and brought into contact with the dishes. Examples of tableware to be washed include cups, glasses, bowls, chopsticks, plates, knives, forks, spoons, and other cooking utensils made of various materials such as ceramics, glass, melamine resin, polycarbonate resin, wood, and metal, as well as other items that can be washed in an automatic dishwasher. Any of the tableware to be washed is tableware that has at least protein stains attached.

[0040] The temperature of the washing liquid when washing dishes is preferably 40°C or higher, more preferably 42°C or higher, and even more preferably 44°C or higher, from the viewpoint of cleaning performance, and is preferably 70°C or lower, more preferably 68°C or lower, and even more preferably 66°C or lower, from the viewpoint of protein decomposition performance.

[0041] From the viewpoint of detergency, the supply rate of the washing liquid during dishwashing is preferably 0.008 L / sec or more, more preferably 0.010 L / sec or more, even more preferably 0.012 L / sec or more, still more preferably 0.03 L / sec or more, still more preferably 0.04 L / sec or more, still more preferably 0.05 L / sec or more, still more preferably 0.08 L / sec or more, still more preferably 0.10 L / sec or more, still more preferably 0.12 L / sec or more, and from the viewpoint of workability, it is preferably 200 L / sec or less, more preferably 190 L / sec or less, still more preferably 180 L / sec or less, still more preferably 160 L / sec or less, still more preferably 8.0 L / sec or less, still more preferably 7.8 L / sec or less, still more preferably 7.6 L / sec or less, still more preferably 3.0 L / sec or less, still more preferably 2.8 L / sec or less, still more preferably 2.6 L / sec or less.

[0042] Furthermore, from the viewpoint of workability, the supply time of the cleaning liquid per dish washing step is preferably 5.0 seconds or more, more preferably 5.5 seconds or more, even more preferably 6.0 seconds or more, even more preferably 7.0 seconds or more, even more preferably 20 seconds or more, even more preferably 22 seconds or more, even more preferably 24 seconds or more, and from the viewpoint of workability, it is preferably 180 seconds or less, more preferably 170 seconds or less, even more preferably 160 seconds or less, even more preferably 125 seconds or less, even more preferably 120 seconds or less, even more preferably 115 seconds or less, even more preferably 110 seconds or less, even more preferably 100 seconds or less, even more preferably 95 seconds or less, even more preferably 90 seconds or less, even more preferably 60 seconds or less, even more preferably 55 seconds or less, and even more preferably 50 seconds or less.

[0043] When the automatic dishwasher is an under-counter type, the amount of cleaning liquid supplied during dishwashing is preferably 0.008 L / sec or more, more preferably 0.010 L / sec or more, and even more preferably 0.012 L / sec or more, from the viewpoint of cleaning power, and is preferably 3.0 L / sec or less, more preferably 2.8 L / sec or less, and even more preferably 2.6 L / sec or less, from the viewpoint of workability. Furthermore, when the automatic dishwasher is an under-counter type, the supply time of the cleaning liquid per washing step is preferably 20 seconds or more, more preferably 22 seconds or more, and even more preferably 24 seconds or more, from the viewpoint of workability, and is preferably 120 seconds or less, more preferably 115 seconds or less, and even more preferably 110 seconds or less, from the viewpoint of workability.

[0044] When the automatic dishwasher is a door-type, the amount of cleaning liquid supplied during dishwashing is preferably 0.03 L / sec or more, more preferably 0.04 L / sec or more, and even more preferably 0.05 L / sec or more, from the viewpoint of cleaning power, and is preferably 8.0 L / sec or less, more preferably 7.8 L / sec or less, and even more preferably 7.6 L / sec or less, from the viewpoint of workability. Furthermore, when the automatic dishwasher is a door-type, the supply time of the cleaning liquid per washing step is preferably 20 seconds or more, more preferably 22 seconds or more, and even more preferably 24 seconds or more, from the viewpoint of workability, and is preferably 100 seconds or less, more preferably 95 seconds or less, and even more preferably 90 seconds or less, from the viewpoint of workability.

[0045] When the automatic dishwasher is a conveyor type, the amount of cleaning liquid supplied during dishwashing is preferably 0.08 L / sec or more, more preferably 0.10 L / sec or more, and even more preferably 0.12 L / sec or more, from the viewpoint of cleaning power, and is preferably 200 L / sec or less, more preferably 190 L / sec or less, and even more preferably 180 L / sec or less, from the viewpoint of workability. Furthermore, when the automatic dishwasher is a conveyor type, the supply time of the cleaning liquid per washing step is preferably 5.0 seconds or more, more preferably 5.5 seconds or more, and even more preferably 6.0 seconds or more, from the viewpoint of workability, and is preferably 60 seconds or less, more preferably 55 seconds or less, and even more preferably 50 seconds or less, from the viewpoint of workability.

[0046] When washing dishes, the cleaning liquid that has come into contact with the dishes can be pumped up by a pump and brought into contact with the dishes again. In other words, the cleaning liquid that comes into contact with the dishes can be circulated in the washing tank, allowing the cleaning liquid to come into contact with the dishes multiple times.

[0047] After washing the dishes, the dishes are rinsed. For example, after washing the dishes, the cleaning liquid in the washing tub is collected in the washing tank, and then rinsing water such as tap water is supplied to the washing tub. The dishes are then rinsed by contacting the rinsing water with the dishes in the washing tub. When rinsing the dishes, the rinsing water can be sprayed to contact the dishes. After contacting the dishes, some or all of the rinse water can be sent to the washing liquid tank. Any amount exceeding the capacity of the washing liquid tank is discharged outside the automatic dishwasher as wastewater. In this way, the washing liquid recovered from the washing tub to the washing tank and diluted with the rinse water is reused as washing liquid for the next load of dishes. When sending the rinse water to the washing tank, some of the washing liquid in the washing tank can be drained in advance before the rinse water is recovered in the washing tank.

[0048] The total amount of rinse water used in one rinse step is determined based on the finish quality of the wash tank. 3 From the viewpoint of reducing the amount of water used, the volume is preferably 0.3 L or more, more preferably 0.5 L or more, and even more preferably 0.7 L or more, and from the viewpoint of reducing the amount of water used, it is preferably 300 L or less, more preferably 250 L or less, and even more preferably 200 L or less.

[0049] Proteins present in small amounts in rinse water are more likely to denature when the temperature of the rinse water is high, making it easier for stains to be recontaminated on tableware. The temperature of the rinse water is preferably 50°C or higher, more preferably 53°C or higher, and even more preferably 55°C or higher, from the viewpoint of easily achieving the effect of the present invention, i.e., the effect of reducing the degree of increase in recontamination due to repeated washing, and is preferably 95°C or lower, more preferably 93°C or lower, and even more preferably 90°C or lower, from the viewpoint of reducing recontamination on tableware by suppressing thermal denaturation of proteins.

[0050] The ratio of the total amount of rinse water used per rinse step to the total amount of cleaning liquid present in the cleaning liquid tank is preferably 0.0004 or more, more preferably 0.0005 or more, even more preferably 0.0007 or more, and even more preferably 0.0009 or more, from the viewpoint of finish quality, and is preferably 0.40 or less, more preferably 0.38 or less, and even more preferably 0.36 or less, from the viewpoint of water conservation. Furthermore, from the viewpoint of finish quality, the amount of rinse water supplied during rinsing is preferably 0.008 L / sec or more, more preferably 0.010 L / sec or more, and even more preferably 0.012 L / sec or more, and from the viewpoint of water conservation, it is preferably 3.5 L / sec or less, more preferably 3.3 L / sec or less, and even more preferably 3.1 L / sec or less. Furthermore, the supply time of rinse water per rinse step is preferably 2 seconds or more, more preferably 3 seconds or more, and even more preferably 4 seconds or more from the viewpoint of cleaning performance, and is preferably 60 seconds or less, more preferably 58 seconds or less, and even more preferably 56 seconds or less from the viewpoint of water conservation.

[0051] When the automatic dishwasher is an under-counter type, the ratio of the total amount of rinse water used per rinse step to the total amount of cleaning liquid present in the cleaning liquid tank is preferably 0.03 or more, more preferably 0.04 or more, even more preferably 0.05 or more, from the viewpoint of finish quality, and is preferably 0.40 or less, more preferably 0.38 or less, even more preferably 0.36 or less, from the viewpoint of water conservation. Furthermore, when the automatic dishwasher is an under-counter type, the amount of rinse water supplied during rinsing is preferably 0.08 L / sec or more, more preferably 0.10 L / sec or more, and even more preferably 0.12 L / sec or more, from the viewpoint of finish quality, and is preferably 1.0 L / sec or less, more preferably 0.9 L / sec or less, and even more preferably 0.8 L / sec or less, from the viewpoint of water conservation. Furthermore, when the automatic dishwasher is an under-counter type, the supply time of rinse water per rinse step is preferably 4.0 seconds or more, more preferably 4.5 seconds or more, and even more preferably 5.0 seconds or more, from the viewpoint of cleaning performance, and is preferably 20 seconds or less, more preferably 18 seconds or less, and even more preferably 16 seconds or less, from the viewpoint of water conservation.

[0052] When the automatic dishwasher is a door-type, the ratio of the total amount of rinse water used per rinse step to the total amount of cleaning liquid present in the cleaning liquid tank is preferably 0.010 or more, more preferably 0.012 or more, and even more preferably 0.014 or more, from the viewpoint of finish quality, and is preferably 0.20 or less, more preferably 0.18 or less, and even more preferably 0.16 or less, from the viewpoint of water conservation. Furthermore, if the automatic dishwasher is a door-type, the amount of rinse water supplied during rinsing is preferably 0.08 L / sec or more, more preferably 0.10 L / sec or more, and even more preferably 0.12 L / sec or more, from the viewpoint of finish quality, and is preferably 1.0 L / sec or less, more preferably 0.9 L / sec or less, and even more preferably 0.8 L / sec or less, from the viewpoint of water conservation. Furthermore, when the automatic dishwasher is a door-type, the supply time of rinse water per rinse step is preferably 4.0 seconds or more, more preferably 4.5 seconds or more, and even more preferably 5.0 seconds or more from the viewpoint of cleaning performance, and is preferably 20 seconds or less, more preferably 18 seconds or less, and even more preferably 16 seconds or less from the viewpoint of water conservation.

[0053] When the automatic dishwasher is a conveyor type, the ratio of the total amount of rinse water used per rinse step to the total amount of cleaning liquid present in the cleaning liquid tank is preferably 0.0004 or more, more preferably 0.0005 or more, and even more preferably 0.0006 or more, from the viewpoint of finish quality, and is preferably 0.08 or less, more preferably 0.07 or less, and even more preferably 0.06 or less, from the viewpoint of water conservation. Furthermore, if the automatic dishwasher is a conveyor type, the amount of rinse water supplied during rinsing is preferably 0.008 L / sec or more, more preferably 0.010 L / sec or more, and even more preferably 0.012 L / sec or more, from the viewpoint of finish quality, and is preferably 2.5 L / sec or less, more preferably 2.4 L / sec or less, and even more preferably 2.3 L / sec or less, from the viewpoint of water conservation. Furthermore, when the automatic dishwasher is a conveyor type, the supply time of rinse water per rinse step is preferably 2.0 seconds or more, more preferably 2.2 seconds or more, and even more preferably 2.4 seconds or more, from the viewpoint of cleaning performance, and is preferably 60 seconds or less, more preferably 58 seconds or less, even more preferably 56 seconds or less, still more preferably 20 seconds or less, still more preferably 18 seconds or less, and even more preferably 16 seconds or less, from the viewpoint of water conservation.

[0054] The washing liquid stored in the washing liquid tank after washing the dishes contains at least the proteins removed from the dishes by washing the dishes. In the dishwashing method of the present invention, the proteins in the washing liquid collected in the washing liquid tank after washing the dishes, which will be contained in the washing liquid by washing the dishes, are decomposed, and then the washing liquid is sent from the washing liquid tank to the washing tank again and reused as the washing liquid for washing the next load of dishes. In other words, in the dishwashing method of the present invention, at least a portion of the washing liquid used to wash dishes is recovered and reused as at least a portion of the washing liquid for the next dish. Then, before this reused washing liquid is brought into contact with dishes again, proteins contained in the washing liquid due to the previous washing of dishes are decomposed, and the washing liquid with decomposed proteins is used as the washing liquid for the next dish.

[0055] The degradation of proteins in the reused cleaning solution can be achieved, for example, by adding component (a) to the cleaning solution contained in the cleaning solution tank. Here, "degradation of proteins" refers to the reduction of the molecular weight of proteins. "Degradation of proteins" refers, for example, to the degradation of proteins to those with a relative molecular mass of less than 25 kDa.

[0056] The lower the content of proteins with a relative molecular mass of 25 kDa or more in the reused cleaning solution, the better the finish quality. Therefore, from the viewpoint of finish quality, the content of proteins with a relative molecular mass of 25 kDa or more in the reused cleaning solution is preferably 3% by mass or less, more preferably 0.3% by mass or less, even more preferably 0.03% by mass or less, still more preferably 0.003% by mass or less, and even more preferably 0.0003% by mass or less. The protein content in the reused cleaning solution may be the protein content in the cleaning solution contained in the cleaning solution tank (the same applies to the contents of components (a) to (e) in the reused cleaning solution). The content of proteins with a relative molecular mass of 25 kDa or more in the reused cleaning solution can be quantified, for example, by the following method.

[0057] (Method for quantifying proteins in washing solution) To 16 μL of the wash solution, add 8 μL of sample buffer (3× SDS-PAGE Loading Buffer, BioVision), vortex, and heat at 90°C for 5 minutes. Then, load 15 μL of the sample onto a polyacrylamide gel (Mini-PROTEAN TGX Any kD Stain-Free Gel 12-well, BioRad) and perform electrophoresis at 200 V for 25 minutes (PowerPac™ HC Basic, BioRad). Use TRIS / GLYCINE / SDS x10 BUFFER (BioRad) as the running buffer and EzstainAqua (ATTA) as the staining solution. Then, analyze bands with relative molecular masses ranging from 25 kDa to 250 kDa using ImageJ image analysis software. Based on a calibration curve obtained using albumin (Fujifilm Wako Pure Chemical Industries, Ltd.), the quality of proteins with a relative molecular mass of 25 kDa or more in the reused washing solution is quantified.

[0058] The concentration of component (a) in the cleaning solution and the concentration of the cleaning composition containing component (a) are adjusted so that the content of proteins with a relative molecular mass of 25 kDa or more in the reused cleaning solution falls within the above range. These components can be added to the cleaning solution in the cleaning solution tank and / or cleaning bath or on the way to the cleaning solution tank and / or cleaning bath.

[0059] In the reused cleaning solution, the content of component (a) is, in terms of enzyme protein, preferably 0.000005% by mass or more, more preferably 0.000007% by mass or more, even more preferably 0.000009% by mass or more, even more preferably 0.00003% by mass or more, even more preferably 0.00005% by mass or more, even more preferably 0.0001% by mass or more, even more preferably 0.0002% by mass or more, and from the viewpoint of reducing skin irritation, preferably 0.05% by mass or less, more preferably 0.045% by mass or less, even more preferably 0.04% by mass or less, even more preferably 0.035% by mass or less, and even more preferably 0.03% by mass or less. The enzyme protein content of component (a) can be quantified, for example, using the Lowry method. For example, a Protein Assay Lowry Kit (manufactured by Nacalai Tespue) can be used to quantify the enzyme protein by the Lowry method.

[0060] The enzyme activity of the reused cleaning solution is 5 U / mL or more, preferably 6 U / mL or more, more preferably 8 U / mL or more, and even more preferably 10 U / mL or more, from the viewpoint of finish quality, and is preferably 3,000 U / mL or less, more preferably 2,700 U / mL or less, even more preferably 2,500 U / mL or less, and even more preferably 2,000 U / mL or less, from the viewpoint of reducing skin irritation. The enzyme activity is the activity of the enzyme measured under conditions of a reaction temperature of 40°C. The enzyme activity of the cleaning solution can be measured using PROTASYME AK TABLETS (Megazyme). The enzyme activity of the reused cleaning solution may be the enzyme activity of the cleaning solution contained in the cleaning solution tank. Alternatively, the enzyme activity of the cleaning solution may be the enzyme activity against protein.

[0061] In the present invention, the enzyme activity value of the reused cleaning solution is measured and calculated as follows: First, 67 mM phosphate buffer (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is placed in a 1.8 mL test tube and kept at 40°C. Next, one PROTASYME AK TABLETS is added and stirred to mix. Next, 0.2 mL of cleaning solution is added and mixed, and the mixture is allowed to react at 40°C for 30 minutes. Next, 1 mL of 10% citric acid aqueous solution is added and mixed, and the mixture is centrifuged (2800 r / min, 15 minutes). The supernatant is then separated as a sample, and the absorbance (590 nm) of the sample is measured. The absorbance change is calculated by subtracting the base absorbance value from the absorbance value of the obtained sample using the following formula. This absorbance change is multiplied by a coefficient (coefficient = 1000) for converting the absorbance change to an enzyme activity value, and the resulting value is used as the enzyme activity value (U / mL) in the cleaning composition (i.e., in the cleaning solution). Enzyme activity (U / mL) = (Sample absorbance (590 nm) - Base absorbance (590 nm)) x 1000 The absorbance of the base (590 nm) is measured using the following method. First, 67 mM phosphate buffer (Fujifilm Wako Pure Chemical Industries, Ltd.) is placed in a 1.8 mL test tube and kept at 40°C. Next, one PROTASYME AK TABLETS is added and stirred. Next, 0.2 mL of ion-exchanged water is added and mixed, and the mixture is allowed to react at 40°C for 30 minutes. Next, 1 mL of 10% citric acid aqueous solution is added and mixed, and the mixture is centrifuged (2800 r / min, 15 minutes). The supernatant is collected as the base, and the absorbance of the base (590 nm) is measured.

[0062] The content of component (b) in the reused cleaning liquid is preferably 0.00010% by mass or more, more preferably 0.0005% by mass or more, and even more preferably 0.0010% by mass or more, from the viewpoint of cleaning performance, and is preferably 0.30% by mass or less, more preferably 0.28% by mass or less, and even more preferably 0.26% by mass or less, from the viewpoint of reducing skin irritation.

[0063] The content of component (c) in the reused cleaning liquid is preferably 0.00001% by mass or more, more preferably 0.00002% by mass or more, and even more preferably 0.00003% by mass or more, from the viewpoint of cleaning performance, and is preferably 0.075% by mass or less, more preferably 0.070% by mass or less, and even more preferably 0.065% by mass or less, from the viewpoint of blend stability.

[0064] The content of component (d) in the reused cleaning liquid is preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more, and even more preferably 0.0004% by mass or more, from the viewpoint of scale deposition inhibitory performance, and is preferably 0.25% by mass or less, more preferably 0.23% by mass or less, and even more preferably 0.20% by mass or less, from the viewpoint of blend stability.

[0065] The pH of the reused cleaning solution is preferably 9.0 or higher, more preferably 9.2 or higher, and even more preferably 9.4 or higher, from the viewpoint of cleaning performance, and is preferably 12.0 or lower, more preferably 11.8 or lower, and even more preferably 11.6 or lower, from the viewpoint of reducing skin irritation. The pH is measured at the temperature of the cleaning solution, and may be the pH of the cleaning solution at 25°C. The pH of the cleaning solution can be measured according to JIS K 3362. The amount of component (b) to be added may be determined so that the pH of the cleaning solution falls within this range.

[0066] From the viewpoint of cleaning performance, the temperature of the cleaning solution in the cleaning solution tank is preferably 40°C or higher, more preferably 42°C or higher, and even more preferably 44°C or higher, and from the viewpoint of proteolytic performance, it is preferably 70°C or lower, more preferably 68°C or lower, and even more preferably 66°C or lower.

[0067] If necessary, the component (a) or a cleaning agent composition containing the component (a) can be supplied to the cleaning liquid stored in the cleaning liquid tank, or to the cleaning liquid or rinse water sent to the cleaning liquid tank so that the contents of the components (a) to (d) fall within the above ranges.

[0068] The time for which the cleaning solution is held in the cleaning solution tank is preferably 10 seconds or more, more preferably 60 seconds or more, and even more preferably 300 seconds or more, from the viewpoint of sufficient decomposition of proteins in the reused cleaning solution, and is preferably 50,000 seconds or less, more preferably 40,000 seconds or less, and even more preferably 30,000 seconds or less, from the viewpoint of enzyme stability.

[0069] In the dishwashing method of the present invention, dishes are washed by repeating the steps of washing dishes, rinsing dishes, decomposing proteins in the reused washing liquid, and subjecting the decomposed protein-containing washing liquid to the next dishwashing step multiple times. After the rinsing step, the washed dishes are removed, and before the washing step, soiled dishes are brought in. If the concentration of component (a) or the detergent composition in the washing liquid contained in the washing liquid tank is sufficient after the rinsing step, the supply of component (a) or the detergent composition before the dishwashing step can be omitted.

[0070] Thus, the dishwashing method of the present invention is thought to inhibit protein hydrophobization (thermal denaturation) by decomposing proteins in the reused washing liquid to reduce their molecular weight, thereby inhibiting protein redeposition to dishes or the accumulation of dirt on the dishes. In other words, the dishwashing method of the present invention can inhibit increased recontamination of dishes and other items due to dirt in the washing liquid when washing under washing conditions in which dirt is mixed in the washing liquid, thereby improving the washing finish of dishes. Note that the content of component (a) in the washing liquid is minute compared to the content of proteins derived from dirt on dishes, so its impact on the finish can be ignored, and therefore the protein content in the washing liquid does not include component (a).

[0071] The dishwashing method of the present invention can be used in commercial and domestic automatic dishwashers, but is particularly suitable for commercial automatic dishwashers that have a short washing time per wash (e.g., 40 to 60 seconds), a large amount of dishes per wash, and wash multiple times per day. In this case, the dishwashing method of the present invention is suitable for use under conditions where the amount of rinsing water used is small (e.g., when the dish is placed horizontally at a height of 2500 cm). 2Even with a water volume of 2 to 3 L per rinse (per rinse), redeposition of accumulated dirt in the washing liquid onto dishes or accumulation of dirt on the dishes can be suppressed. In other words, the tableware washing method of the present invention can suppress an increase in redeposition of dirt in the washing liquid when washing under washing conditions in which dirt is mixed in the washing liquid, thereby improving the washing finish of dishes.

[0072] The dishwashing method of the present invention is suitable for water-saving automatic dishwashers. A water-saving automatic dishwasher is, for example, an automatic dishwasher that can perform water-saving washing by rinsing with less water than a conventional automatic dishwasher, and includes not only machines dedicated to water-saving washing but also automatic dishwashers with a water-saving washing function. For example, in a conventional automatic dishwasher, the amount of water required per rinse cycle is 2500 cm2 (approximately 1000 sq ft) of water for a horizontal surface where dishes are placed. 2 However, in a water-saving automatic dishwasher, the amount of water required per rinse cycle is 2500cm above the horizontal surface where the dishes are placed. 2 Therefore, the amount of water used per rinse is 2 to 3 liters, or even less than 2 liters, or even less than 1 liter. 2 An automatic dishwasher that can perform rinsing with 2 to 3 L per wash, further less than 2 L, and further 1 L or less per wash may be a water-saving automatic dishwasher. [Example]

[0073] [Recontamination evaluation method] 55 L of 60°C hot water (German hardness 3°dH) was placed in the cleaning solution tank of a commercial dishwasher (Hoshizaki Corporation, JWA-680A). In the case of Table 1, 55.6 g of fresh cream (trade name: Fresh Pure Milk Fat, Megmilk Snow Brand Co., Ltd.), 55.6 g of curry powder (trade name: Curry Mix, S&B Foods Co., Ltd.), 55.6 g of margarine (trade name: Neo Soft, Megmilk Snow Brand Co., Ltd.), 27.8 g of rapeseed oil (Fujifilm Wako Pure Chemical Industries, Ltd.), 27.8 g of ketchup (trade name: Tomato Ketchup, Kagome Co., Ltd.), and 55.6 g of raw egg (Akita Foods Co., Ltd.) were added as protein-containing stains, and the mixture was stirred until uniform. In the cases of Tables 2 and 3, 55 L of 60°C hot water (German hardness 3°dH) was added to the cleaning liquid tank of the commercial dishwasher, and 10 g (initial protein amount 182 mg / L, Table 2) or 60 g (initial protein amount 1091 mg / L, Table 3) of albumin (Fujifilm Wako Pure Chemical Corporation) was added as a protein soiling agent, and the mixture was stirred to make it uniform. Next, the detergent composition shown in the table was added to this warm water, and the water was kept at 60°C for 30 minutes to prepare a cleaning solution containing soil (a cleaning solution in which the concentration of each component in the cleaning solution was [the value of each component in the table × 10 (mg / kg)]; hereinafter referred to as cleaning solution). A transparent glass plate (manufactured by Kenis Co., Ltd., 10 cm wide, 10 cm long, 2 mm thick) was placed on the rack of the washing tub of a commercial dishwasher. The cleaning solution was then supplied from the washing tank to the washing tub, and the transparent glass plate was washed for 40 seconds by contacting the cleaning solution with the cleaning solution. Thereafter, the transparent glass plate was rinsed for 6 seconds with 2 L of 80°C rinse water without using a rinse aid. The transparent glass plate was removed from the rack and dried at 25°C for 30 minutes. This washing and rinsing process was repeated five times at 30-minute intervals. Recontamination of the transparent glass plate was evaluated using the transparent glass plate after it had been washed once, three times, and five times in total.

[0074] [Method for quantifying proteins attached to a transparent glass plate] Sodium dodecyl sulfate (hereinafter referred to as SDS, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was diluted with ion-exchanged water to obtain a 0.3% by mass SDS aqueous solution. A washed and dried transparent glass plate was immersed in this SDS aqueous solution, and proteins attached to the transparent glass plate were recovered in the SDS aqueous solution. The proteins recovered in the SDS aqueous solution were then quantified using a Protein Assay Lowry Kit (manufactured by Nacalai Tespue).

[0075] [Method for quantifying enzyme activity] The enzyme activity of each cleaning solution was determined before the cleaning solution was brought into contact with the dishes. First, 67 mM phosphate buffer (Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a 1.8 mL test tube and maintained at 40 ° C. Next, one PROTASYME AK TABLETS was added and mixed by stirring. Next, 0.2 mL of cleaning solution was added and mixed, and the mixture was allowed to react at 40 ° C. for 30 minutes. Next, 1 mL of 10% citric acid aqueous solution was added and mixed, and the mixture was centrifuged (2800 r / min, 15 minutes). The supernatant was then separated and the absorbance (590 nm) of the sample was measured. The absorbance value of the obtained sample was calculated by subtracting the base absorbance value from the absorbance value according to the following formula, and this absorbance change was multiplied by a coefficient (coefficient = 1000) for converting the absorbance change to an enzyme activity value. This value was used as the enzyme activity value (U / mL) of the cleaning solution. Enzyme activity (U / mL) = (Sample absorbance (590 nm) - Base absorbance (590 nm)) x 1000 The absorbance of the base (590 nm) was measured by the following method. First, 67 mM phosphate buffer (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a 1.8 mL test tube and kept at 40°C. Next, one PROTASYME AK TABLETS was added and mixed by stirring. Next, 0.2 mL of ion-exchanged water was added and mixed, and the mixture was allowed to react at 40°C for 30 minutes. Next, 1 mL of 10% citric acid aqueous solution was added and mixed, and the mixture was centrifuged (2800 r / min, 15 minutes). The supernatant was collected as the base, and the absorbance of the base (590 nm) was measured.

[0076] The following were used as components (a) to (d). (a) Component, enzyme (trade name: Savinase 18T, manufactured by Novozymes) (b) ingredient, anhydrous sodium carbonate (soda ash (dense), manufactured by Tokuyama Corporation) (d) ingredient, trisodium citrate dihydrate (trade name "Purified Sodium Citrate M", manufactured by Fuso Chemical Co., Ltd.)

[0077] [Table 1]

[0078] [Table 2]

[0079] [Table 3]

[0080] The washing conditions for the washing method of the present invention are shown in Table 4. When washing under these washing conditions, the reused washing liquid contains a predetermined amount of component (a), so it is estimated that the enzyme activity of the washing liquid is 5 U / mL or more, which is thought to suppress recontamination of dishes and accumulation of dirt on dishes and improve the finish of automatic dishwashers.

[0081] [Table 4]

Claims

1. A method for washing dishes using an automatic dishwasher having a washing liquid tank that contains washing liquid and a washing tub that brings the washing liquid supplied from the washing liquid tank into contact with dishes, comprising: At least a part of the cleaning liquid used for washing the dishes is collected in the cleaning liquid tank and reused as at least a part of new cleaning liquid three or more times; The cleaning solution to be reused contains (a) a protease (hereinafter referred to as component (a)), (b) an alkaline agent, and (d) a chelating agent (excluding those containing enzymes other than component (a)), After the enzyme activity of the cleaning solution is increased to 76 U / mL or more, the cleaning solution is brought into contact with tableware. How to wash dishes.

2. 2. The method for washing tableware according to claim 1, wherein the reused washing liquid is mixed with component (a) and one or more selected from the following components (b) and (d), and the enzyme activity of the washing liquid is set to 76 U / mL or more. (b) Alkaline agent (d) chelating agent

3. 3. The method for washing tableware according to claim 2, wherein a detergent composition containing component (a) and one or more selected from component (b) and component (d) is mixed into the washing liquid to be reused.

4. 4. The method for washing tableware according to claim 3, wherein the content of component (a) in the detergent composition is 0.05% by mass or more and 10% by mass or less, the content of component (b) is 1% by mass or more and 60% by mass or less, and the content of component (d) is 1% by mass or more and 50% by mass or less.

5. A method for cleaning tableware as described in claim 3 or 4, wherein the detergent composition further contains a surfactant as component (c), and the content of component (c) in the detergent composition is 0.1 mass% or more and 15 mass% or less.

6. A method for cleaning tableware as described in claim 5, wherein component (c) is a nonionic surfactant.

7. The method for washing tableware according to any one of claims 1 to 6, wherein the pH of the reused washing liquid is 9.0 or more and 12.0 or less.

8. The method for washing tableware according to any one of claims 1 to 7, wherein the enzyme activity of the reused washing liquid is 76 U / mL or more and 3,000 U / mL or less.

9. The dish washing method according to any one of claims 1 to 8, wherein the cleaning liquid is at 40°C or higher and 70°C or lower, and the cleaning liquid is brought into contact with the dishes at a rate of 0.008 L / sec or higher and 200 L / sec or lower for 5 seconds or higher and 180 seconds or lower.

10. The method for washing tableware according to any one of claims 1 to 9, wherein after the washing liquid is brought into contact with the tableware, the tableware is rinsed with rinsing water.

11. The method for washing tableware according to claim 10, wherein the rinsing water is at 50°C or higher and 95°C or lower, and the rinsing water is brought into contact with the tableware at a rate of 0.008 L / sec or higher and 3.5 L / sec or lower for 4 seconds or higher and 20 seconds or lower.

12. 12. The method for washing tableware according to claim 10 or 11, wherein a cycle of contacting the dishware with the cleaning liquid and then rinsing the dishware with rinsing water is performed three or more times.

13. The method for washing tableware according to any one of claims 10 to 12, wherein the rinsing water is sprayed onto the tableware to bring the rinsing water into contact with the tableware.

14. The method for washing tableware according to any one of claims 1 to 13, wherein the washing liquid is sprayed onto the tableware to bring the washing liquid into contact with the tableware.

15. The method for washing tableware according to any one of claims 1 to 14, wherein the washing liquid collected in the washing liquid tank contains proteins removed by washing the tableware.

16. The method for washing tableware according to any one of claims 1 to 15, wherein the washing liquid collected in the washing liquid tank is kept at a temperature of 40°C or higher and 70°C or lower for 10 seconds or higher and 50,000 seconds or lower.

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