JP7758484B2 - How to wash dishes - Google Patents

Description

The present invention relates to a method for washing dishes and a detergent composition for automatic dishwashers. In particular, it relates to a method for washing dishes using an automatic dishwasher.

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.

Patent Document 1 discloses a detergent composition for automatic dishwashers, which contains (A-1) methylglycine diacetate and an alkali metal salt thereof, (A-2) citric acid and an alkali metal salt thereof, 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.

International Publication No. 2013/175659 Japanese Patent Application Laid-Open No. 2018-024723 JP 2012-214539 A Japanese Patent Application Laid-Open No. 2005-154716

In water-saving automatic dishwashers, the amount of rinse water is also reduced, so the amount of accumulated dirt in the reused washing liquid tends to increase. This tendency is particularly pronounced in commercial automatic dishwashers, which are used for a large number of washes, and the repeated use and washing of dishes also 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.

The present invention provides a method for washing tableware that suppresses the increase in recontamination of tableware and other items caused by dirt in the washing liquid when washing under washing conditions in which dirt is mixed in the washing liquid.

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:
The present invention relates to a method for washing tableware, in which at least a portion of the washing liquid used for washing tableware is collected in a washing liquid tank and reused as at least a portion of new washing liquid, and after decomposing proteins in the reused washing liquid, the washing liquid is brought into contact with the tableware.

The present invention also relates to a detergent composition for automatic dishwashers used in the above-mentioned dishwashing method, which contains (a) a protease, (b) an alkaline agent, and (c) a nonionic surfactant.

The present invention provides a method for washing tableware that, when washing under washing conditions in which dirt is mixed in the washing liquid, prevents the increase in re-contamination of tableware, etc., due to dirt in the washing liquid.

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, and especially 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 the 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 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 do not come into direct contact with food, such as the backside of the dishes or a glass used for drinking water, is suppressed. 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.

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 part of the washing liquid used for washing dishes is collected in a washing liquid tank and reused as at least a part of new washing liquid, and after decomposing proteins in the reused washing liquid, the washing liquid is brought into contact with the dishes.

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.
In order to obtain the effects of the present invention more significantly, the tableware washing method of the present invention is preferably a method in which the same tableware is 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 tableware is washed using reused washing liquid, the more significant the effects of the tableware washing method of the present invention. Here, washing the same tableware two or more times using reused washing liquid includes washing the tableware after washing, using the tableware after use, and then subjecting the used tableware to the next wash.

The degradation of proteins in the cleaning solution can be achieved by adding (a) a protease (hereinafter referred to as component (a)) or a cleaning composition containing component (a) to the cleaning solution in the cleaning tank and/or cleaning solution tank. Component (a) or a cleaning composition containing component (a) can be added directly to the cleaning solution in the cleaning tank and/or cleaning solution tank, or to the cleaning solution sent to the cleaning tank and/or cleaning solution tank.

First, we will explain component (a) used in the dishwashing method of the present invention.

<(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 a protease 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, aspergylopeptidase B, and the like. 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 trademarks; manufactured by Novozymes), Maxatase, Maxapem, Maxacal, Properase, Prafect, and Prafect OX (registered trademarks; 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). As component (a), alkaline proteases are particularly suitable.

Next, we will explain the detergent composition for automatic dishwashers (hereinafter also referred to as the detergent composition of the present invention) used in the dishwashing method of the present invention.

<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 also 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)).
The detergent composition of the present invention is a detergent composition for automatic dishwashers used in the dishwashing method of the present invention, and may be a detergent composition for automatic dishwashers containing (a) a protease, (b) an alkaline agent, and (c) a nonionic surfactant.
Furthermore, the detergent composition of the present invention may be a detergent composition for automatic dishwashers used in the dishwashing method of the present invention, which contains (a) a protease, (b) an alkaline agent, and (d) a chelating agent.

Component (b) is an alkaline agent, and the alkaline agent 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 hydrogen carbonate, and potassium hydrogen carbonate. 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.
The amine compound may be an alkanolamine. In the present invention, primary alkanolamines are particularly preferred, specifically monoethanolamine. Among these alkali 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.

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 standpoint of cleaning properties, one or more selected from nonionic surfactants and anionic surfactants are preferred, with nonionic surfactants being more preferred.

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 standpoint of cleaning performance, 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.

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

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), or salts thereof.

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.

Examples of phosphonic acid chelating agents include hydroxyethylidene diphosphonic acid (HEDP), nitrilotrismethylenephosphonic acid (NTMP), phosphonobutanetricarboxylic acid (PBTC), ethylenediaminetetramethylenephosphonic acid (EDTMP), and salts thereof.

Salts in chelating agents include, for example, 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, with sodium salts and potassium salts being more preferred.

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 reduced skin irritation. The enzyme protein of component (a) can be quantified, for example, using the Lowry method. Quantification of enzyme protein using the Lowry method can be performed using, for example, the Protein Assay Lowry Kit (manufactured by Nacalai Tespue).

When the cleaning composition of the present invention contains component (b), the concentration of component (b) in the cleaning 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 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.

When the cleaning composition of the present invention contains component (c), the concentration of component (c) 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 formulation stability.

When the detergent composition of the present invention contains component (d), the concentration of component (d) 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 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 formulation stability.

When the cleaning 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 cleaning performance. Component (a) is expressed in terms of the amount of enzyme protein.

The cleaning composition of the present invention preferably has a pH of 9 or more and 12 or less at 25°C. The cleaning composition of the present invention preferably has a pH of 10 or more and 12 or less at 25°C when formed into a 0.1% by mass aqueous solution of the concentrated cleaning composition described below. The pH of the diluted cleaning solution can be measured in accordance with JIS K 3362.

The cleaning composition of the present invention may also contain bleaching agents, antifoaming agents, rust inhibitors, hydrotropic agents, surface modifiers, fragrances, etc.

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 is, for example, 0.01% by mass or more and 0.5% by mass or less.

In the concentrated cleanser composition, the content of component (a) is 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, in terms of enzyme protein, from the viewpoint of proteolytic performance; and from the viewpoint of reduced skin irritation, it is 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. The enzyme protein of component (a) can be quantified, for example, using the Lowry method. Quantification of enzyme protein using the Lowry method can be performed using, for example, the Protein Assay Lowry Kit (manufactured by Nacalai Tespue).

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 is 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 reducing skin irritation.

When the cleaning composition of the present invention contains component (c), the content of component (c) in the concentrated cleaning 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 even 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 even more preferably 10% by mass or less, from the viewpoint of blend stability.

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 prevention performance, and is 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 formulation stability.

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

<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.

When washing tableware, the cleaning liquid contained in the cleaning liquid tank is sent to the washing tub, and the cleaning liquid is brought into contact with the tableware in the washing tub to wash the tableware. 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 tub. When washing tableware, component (a) or a detergent composition containing component (a) may be added to the washing tub or the cleaning liquid sent to the washing tub, as necessary. Furthermore, when washing tableware, for example, the cleaning liquid can be sprayed and brought into contact with the tableware.
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.

From the viewpoint of cleaning performance, 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 protein degradation performance, the temperature is preferably 70°C or lower, more preferably 68°C or lower, and even more preferably 66°C or lower.

From the viewpoint of cleaning power, the supply rate of 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.

Furthermore, from the viewpoint of workability, the supply time of the cleaning liquid per dish washing process 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.

When the automatic dishwasher is an under-counter type, the amount of washing 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 detergency, 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.

When the automatic dishwasher is a door-type, the amount of washing 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 detergency, 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.

When the automatic dishwasher is a conveyor type, the amount of washing 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.

When washing dishes, the cleaning liquid that has come into contact with the dishes can be pumped up and brought into contact with the dishes again. In other words, the cleaning liquid that comes into contact with the dishes can be circulated within the washing tank, allowing the cleaning liquid to come into contact with the dishes multiple times.

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.

The total amount of rinse water used in one rinsing step is preferably 0.3 L or more, more preferably 0.5 L or more, and even more preferably 0.7 L or more per 1 ^m3 of the cleaning tank from the viewpoint of finish quality, and is preferably 300 L or less, more preferably 250 L or less, and even more preferably 200 L or less from the viewpoint of reducing the amount of water used.

Proteins present in small amounts in rinse water are more likely to denature when the rinse water temperature is high, making redeposition of soil onto tableware more likely. From the viewpoint of easily achieving the effect of the present invention, i.e., the effect of reducing the degree of increase in redeposition due to repeated washing, the rinse water temperature is preferably 50°C or higher, more preferably 53°C or higher, and even more preferably 55°C or higher. From the viewpoint of reducing redeposition of tableware by inhibiting thermal denaturation of proteins, the temperature is preferably 95°C or lower, more preferably 93°C or lower, and even more preferably 90°C or lower.

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.

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, and 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, and 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.

When the automatic dishwasher is a door-type machine, 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, when 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.

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, when 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.

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.

The degradation of proteins in the reused cleaning solution can be achieved, for example, by adding component (a) to the cleaning solution stored in the cleaning solution tank. Here, "degrading proteins" refers to reducing the molecular weight of proteins. "Reducing the molecular weight of proteins" refers, for example, to degrading proteins to those with a relative molecular mass of less than 25 kDa.

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 standpoint 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, even 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 molecular mass of 25 kDa or more in the reused cleaning solution can be quantified, for example, by the following method. The above content may be the content in the cleaning solution before it is used for cleaning.

(Method for quantifying proteins in washing solution)
To 16 μL of washing solution, 8 μL of sample buffer (3×SDS-PAGE Loading Buffer, BioVision) was added, stirred, and heated at 90°C for 5 minutes. 15 μL of sample was injected into a polyacrylamide gel (Mini-PROTEAN TGX Any kD Stain-Free Gel 12-well, Bio-Rad) and electrophoresed at 200 V for 25 minutes (PowerPac™ HC Basic, Bio-Rad). The electrophoresis buffer used was TRIS/GLYCINE/SDS x10 BUFFER (Bio-Rad), and the staining solution used was EzstainAqua (ATTA). Then, bands in the range of 25 kDa to 250 kDa are analyzed using image analysis software Image J. Based on a calibration curve obtained using albumin (Fujifilm Wako Pure Chemical Industries, Ltd.), proteins of 25 kDa or more in the reused washing solution are quantified.

The mass ratio ((undegraded protein amount)/(initial protein amount)) of the content of proteins with a relative molecular weight of 25 kDa or more in the cleaning solution collected in the cleaning solution tank (hereinafter referred to as the initial protein amount) to the content of proteins with a relative molecular weight of 25 kDa or more in the cleaning solution collected in the cleaning solution tank and used for the next wash (hereinafter referred to as the undegraded protein amount) is preferably 0.0001 or more, more preferably 0.0002 or more, even more preferably 0.0003 or more, from the viewpoint of preventing re-contamination and accumulation of dirt on tableware. Also, from the viewpoint of preventing re-contamination and accumulation of dirt on tableware, it is preferably 0.7 or less, more preferably 0.65 or less, even more preferably 0.55 or less. Furthermore, after performing the first washing step of washing tableware using the washing method of the present invention, a second washing step may be additionally performed one or more times. In the second washing step, it is preferable to wash the dishes with a treatment liquid that satisfies the condition that the mass ratio of the amount of undegraded protein in the treatment liquid in the second step to the initial protein amount in the first washing step is 0.0001 or more and 0.7 or less.

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 weight of 25 kDa or more or the mass ratio of [(amount of undegraded protein)/(initial protein)] 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 tank, or on the way to the cleaning solution tank and/or cleaning tank.

In the reused cleaning solution, the content of component (a) 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, even more preferably 0.0002% by mass or more, and from the viewpoint of reducing skin irritation, it 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. The enzyme protein content of component (a) can be quantified, for example, using the Lowry method. For quantification of enzyme protein using the Lowry method, for example, a Protein Assay Lowry Kit (manufactured by Nacalai Tespue) can be used.

From the viewpoint of cleaning performance, 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, and from the viewpoint of reducing skin irritation, it 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 cleaning performance, the content of component (c) in the reused cleaning solution 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 blend stability, the content 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 scale adhesion prevention performance, 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, and from the viewpoint of blend stability, it 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 cleaning performance, 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 reducing skin irritation, the pH is preferably 12.0 or lower, more preferably 11.8 or lower, and even more preferably 11.6 or lower. 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 in accordance with JIS K 3362. The amount of component (b) added may be determined so that the pH of the cleaning solution falls within this range.

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; from the viewpoint of protein decomposition performance, it is preferably 70°C or lower, more preferably 68°C or lower, and even more preferably 66°C or lower.

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

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 or denaturation of proteins in the cleaning solution to be reused, 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.

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, the soiled dishes are brought in. Furthermore, 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.

In this way, the dishwashing method of the present invention is thought to inhibit protein hydrophobization (thermal denaturation) by decomposing proteins in the reused washing liquid to lower 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 re-contamination 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, 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).

The dishwashing method of the present invention can be used in commercial and home automatic dishwashers, but is particularly suitable for commercial automatic dishwashers that have a short wash time (e.g., 40 to 60 seconds), a large amount of items per wash, and wash multiple times per day. In this case, the dishwashing method of the present invention can suppress redeposition of accumulated dirt in the washing liquid onto dishes and the accumulation of dirt on the dishes, even under conditions where a small amount of rinse water is used (e.g., 2 to 3 L per 2,500 ^cm2 of horizontal surface area where dishes are placed per rinse). In other words, the dishwashing method of the present invention can suppress the increase in redeposition of dirt on dishes and the like due to dirt in the washing liquid when washing under washing conditions where dirt is mixed in the washing liquid, thereby improving the washing quality of the dishes.

The dishwashing method of the present invention is suitable for water-saving automatic dishwashers. A water-saving automatic dishwasher refers to, for example, an automatic dishwasher capable of performing a water-saving rinse using less water than a conventional automatic dishwasher. This includes not only machines dedicated to water-saving rinses but also automatic dishwashers with a water-saving rinse function. For example, a conventional automatic dishwasher requires 4 to 6 L of water per 2500 ^cm2 of horizontal dish surface area, whereas a water-saving automatic dishwasher requires 2 to 3 L, even less than 2 L, or even 1 L or less per 2500 ^cm2 of horizontal dish surface area. Therefore, an automatic dishwasher that can perform a rinse using ² to 3 L, even less than 2 L, or even 1 L or less per 2500 cm2 of horizontal dish surface area may be considered a water-saving automatic dishwasher.

[Method for assessing the degree of contamination]
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), and in the case of Table 1, 55.6 g of fresh cream (trade name: Fresh Pure Milk Fat, manufactured by Megmilk Snow Brand Co., Ltd.), 55.6 g of curry powder (trade name: Curry Mix, manufactured by S&B Foods Co., Ltd.), 55.6 g of margarine (trade name: Neo Soft, manufactured by 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, manufactured by Kagome Co., Ltd.), and 55.6 g of raw egg (Akita Foods Co., Ltd.) were added as complex soils containing protein, and the mixture was stirred to be uniform. Similarly, in the cases of Tables 2 and 3, 55 L of 60°C warm water (German hardness 3° dH) was placed in the cleaning solution tank, and 10 g (initial protein amount 182 mg/L) or 60 g (initial protein amount 1091 mg/L) of albumin (Fujifilm Wako Pure Chemical Industries, Ltd.) was added as proteinaceous soil, 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 x 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 rinsing water at 80°C 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. The degree of contamination of the transparent glass plate was evaluated for the transparent glass plate after it had been washed once, three times, and five times in total.

[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).

[Method for quantifying undegraded protein]
The amount of undegraded protein in the cleaning solution was quantified before contacting the dishware with the cleaning solution. 8 μL of sample buffer (3×SDS-PAGE Loading Buffer, BioVision) was added to 16 μL of cleaning solution, stirred, and heated at 90°C for 5 minutes. 15 μL of sample was injected into a polyacrylamide gel (Mini-PROTEAN TGX Any kD Stain-Free Gel 12-well, Bio-Rad) and electrophoresed at 200 V for 25 minutes (PowerPac™ HC Basic, Bio-Rad). The electrophoresis buffer used was TRIS/GLYCINE/SDS x10 BUFFER (Bio-Rad), and the staining solution was EzstainAqua (ATTA). The 25 kDa to 250 kDa bands were analyzed using image analysis software Image J. The quality of undegraded protein was quantified based on a calibration curve obtained using albumin (Fujifilm Wako Pure Chemical Industries, Ltd.).
The calibration curve was prepared as follows. 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), and 0 g, 10 g, 30 g, or 60 g of albumin (Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred to homogenize to prepare a cleaning solution. To 16 μL of the cleaning solution, 8 μL of sample buffer (3x SDS-PAGE Loading Buffer, Biovision) was added, stirred, and then heated at 90°C for 5 minutes. 15 μL of sample was injected into a polyacrylamide gel (Mini-PROTEAN TGX Any kD Stain-Free Gel 12-well, Bio-Rad) and electrophoresis was performed at 200 V for 25 minutes (PowerPac™ HC Basic, Bio-Rad). The electrophoresis buffer used was TRIS/GLYCINE/SDS x10 BUFFER (Bio-Rad), and the staining solution was EzstainAqua (ATTA). Bands of 25 kDa to 250 kDa were analyzed using image analysis software ImageJ. The amount of added albumin was calculated as protein.
The initial protein amount in the cleaning solution was determined by quantifying the amount of undegraded protein in the cleaning solution before adding the detergent composition using the same method as above. The initial protein amount is a model of the protein amount in the cleaning solution to be reused (i.e., the mass of protein contained in the cleaning solution collected in the cleaning solution tank). The initial protein amount was 131 mg/L.

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

In the examples in Tables 1 and 2, when comparing the initial protein amount and undecomposed protein after one cumulative wash, it can be seen that the protein in the cleaning solution used for washing has been decomposed in advance. In other words, in the examples in Tables 1 and 2, by decomposing the protein in the cleaning solution to be reused in advance, the amount of dirt attached to the dishes after washing is reduced, and re-contamination of the dishes is suppressed. It is also presumed that a reduction in the amount of dirt attached (i.e., the amount of protein attached) will also reduce the total amount of attached complex dirt, including lipid dirt.
Furthermore, as shown in the examples in Tables 1 and 2, by decomposing the proteins in the reused washing liquid in advance, the contamination levels after the third and fifth cumulative washes are closer to the standard values than in the comparative examples. In other words, by decomposing the proteins in the reused washing liquid in advance, the degree of suppression of recontamination of tableware is higher than in the comparative examples. From this, it can be inferred that even when dishes are repeatedly washed and used in an automatic dishwasher, an increase in recontamination of tableware (i.e., accumulation of dirt on tableware) can be suppressed.
In other words, when dishes are washed with wash water having a high ratio of undegraded protein amount to initial protein amount with a relative molecular mass of 25 kDa or more, the proteins attached to the surface of the dishes are thermally denatured during the washing process, especially the rinsing process at high temperatures, making the proteins more likely to adhere to the dishes and hydrophobizing the surface of the dishes. Furthermore, repeated washing using dirty wash water is thought to cause further accumulation of dirt on the hydrophobized surface of the dishes, resulting in a poor finish of the dishes. On the other hand, even in wash water with a high dirt content, by reducing the ratio of undegraded protein amount to initial protein amount with a relative molecular mass of 25 kDa or more, the thermal denaturation of the proteins attached to the surface of the dishes is thought to be suppressed, and the hydrophobization of the surface of the dishes is suppressed. The results of the examples also show that repeated washing with dirty wash water does not increase the accumulation of dirt on the surface of the dishes.

Table 3 shows the washing conditions used in the washing method of the present invention. When washing under these washing conditions, component (a) decomposes proteins in the reused washing liquid, which is then used to wash dishes. This prevents dirt in the washing liquid from redepositing or accumulating on the dishes, and is thought to improve the finish of automatic dishwashers.

Claims (16)

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 reused cleaning solution contains (a) a protease, (b) an alkaline agent, and (d) a chelating agent (provided that the reused cleaning solution does not contain any enzyme other than component (a) );
The content of proteins having a relative molecular weight of 25 kDa or more in the reused cleaning solution is 0.003% by mass or less;
Decomposing proteins in the reused washing liquid and then contacting the washing liquid with the dishes.
How to wash dishes. The dishwashing method according to claim 1, wherein the washing liquid collected in the washing liquid tank contains proteins removed by washing the dishes. The method for washing tableware according to claim 1 or 2, in which washing water at 40°C or higher and 70°C or lower is brought into contact with the tableware in the washing tank at a rate of 0.008 L/sec to 200 L/sec for 5 seconds to 180 seconds. A method for washing tableware according to any one of claims 1 to 3, in which after the dishware has been brought into contact with the washing liquid in the washing tank, rinse water at 50°C or higher and 90°C or lower is brought into contact with the dishware at a rate of 0.008 L/sec to 3.5 L/sec for 4 seconds to 20 seconds, and then at least a portion of the rinse water is recovered in the washing liquid tank. 5. The method for washing tableware according to claim 4, wherein the amount of rinsing water used per rinsing step is 0.3 L or more and 300 L or less per 1 ^m3 of the washing tank. The dishwashing method according to claim 4 or 5, wherein the ratio of the total amount of rinse water used in one rinse step to the total amount of cleaning liquid in the cleaning liquid tank is 0.0005 or more and 0.4 or less. The method for washing tableware according to any one of claims 1 to 6, wherein (a) a protease is used to decompose proteins in the reused washing liquid. The method for washing tableware according to any one of claims 1 to 7, wherein (a) a proteolytic enzyme is added to the washing tank and/or the washing liquid tank to decompose proteins in the washing liquid to be reused. (a) A method for washing tableware according to any one of claims 1 to 8, in which a detergent composition containing a protease is added to a washing tank and/or a washing liquid tank to decompose proteins in the washing liquid to be reused. The method for washing tableware according to any one of claims 1 to 9, wherein a detergent composition containing (a) a protease, (b) an alkaline agent, and (d) a chelating agent is added to a washing tank and/or a washing liquid tank to decompose proteins in the washing liquid to be reused. The method for washing tableware according to any one of claims 1 to 10, wherein (a) a protease is added to the washing liquid so that the content of proteins with a relative molecular mass of 25 kDa or more in the reused washing liquid is 0.003 mass% or less. The dishwashing method according to any one of claims 8 to 11, wherein (a) the proteolytic enzyme is one or more selected from proteases and peptidases. The dishwashing method according to any one of claims 8 to 12, wherein (a) the protease is an alkaline protease. A method for washing tableware according to any one of claims 1 to 13, wherein after the cleaning liquid is collected in the cleaning liquid tank, the collected cleaning liquid is held at a temperature of 40°C or higher and 70°C or lower for 10 seconds or longer and 50,000 seconds or shorter, and then the cleaning liquid is brought into contact with the tableware. The tableware washing method according to any one of claims 1 to 14, wherein the content of component (a) in the reused washing liquid is, in terms of enzyme protein, 0.0002% by mass or more and 0.05% by mass or less, the content of component (b) is 0.0010% by mass or more and 0.30% by mass or less, and the content of component (d) is 0.0004% by mass or more and 0.20% by mass or less. A detergent composition for automatic dishwashers used in the dishwashing method according to any one of claims 1 to 15 ,
A detergent composition for automatic dishwashers, comprising (a) a protease, (b) an alkaline agent, and (d) a chelating agent .