Detergent composition for automatic dishwashers

Abstract

To provide a detergent composition for automatic dishwasher, capable of effectively removing complex stains containing animal protein and fat and vegetable oil in washing by an automatic dishwasher even in a neutral to weak alkaline fluid, and a method for washing tableware.SOLUTION: A detergent composition for automatic dishwasher contains a component (a), which is an inorganic reducing agent having a redox potential of +71 mV or less, a component (b), which is a nonionic surfactant, and water. The mass ratio between the content of component (a) and the content of component (b), which is (a) / (b), is 0.3 or more and 4.5 or less. The pH at 25°C is 6 or more and 11 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a detergent composition for automatic dishwashers and a method for cleaning dishes. [Background technology]

[0002] Dishwashers are used to wash dirty dishes, glasses, cooking utensils, and other tableware in kitchens such as homes, restaurants, and coffee shops, as well as plastic containers for ingredients and products used in food and beverage factories. The main target stains are food-derived proteins, starches, oils, and grease, which combine to adhere to dishes, glasses, cooking utensils, and other tableware and plastic containers. In addition, these stains can be thermally denatured during cooking, turning into strong, adherent stains.

[0003] Typically, dishwashers perform the washing process followed by the rinsing process. For commercial use, the required time for these processes is very short, typically 40-180 seconds for the washing process and 5-20 seconds for the rinsing process. However, for stubborn stains, these designed times may not be sufficient for cleaning, and it is not uncommon for the washing process to take several times longer than the designed time to achieve adequate cleaning. Protein-containing stains are particularly difficult to remove, so strong alkaline detergents are commonly used. However, strong alkaline detergents are difficult to handle, and technology is needed to quickly clean protein-containing stains even at near-neutral pH levels.

[0004] Patent Document 1 discloses a technology for a liquid detergent composition for dishwashers containing a nonionic surfactant such as an alkyl glycoside or a polyoxyethylene alkyl ether, and states that a very small amount of a reducing agent is effective in suppressing gas generation. Patent Document 2 discloses a technique for applying a very small amount of a reducing agent to stabilize perfume ingredients in a detergent composition containing a nonionic surfactant. Patent Document 3 discloses a technique for applying a reducing agent to stabilize fragrance in a powder detergent containing a nonionic surfactant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-91838 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-522279 [Patent Document 3] Japanese Patent Application Publication No. 9-78099 Summary of the Invention [Problem to be solved by the invention]

[0006] Various types of stains adhere to tableware, but complex stains containing protein and lipids are particularly prone to deterioration and hardening, making them difficult to remove in a short time using a commercial dishwasher. Egg yolk, in particular, can adhere strongly to dishes depending on the state of deterioration of the stain due to drying and denaturation over time, making it even more difficult to remove in a short time. Currently, strong alkaline conditions are required to effectively remove protein and lipid stains in a short time, but considering the impact on workers and the environment, a neutral to weakly alkaline solution is preferable. Furthermore, in actual dishwashing, not only animal protein stains but also vegetable liquid oils used in cooking commonly cause stains to become complex.

[0007] The present invention provides a detergent composition for automatic dishwashers, which can effectively clean complex soils containing animal proteins and lipids and vegetable liquid oils in dishwashers even in a neutral to weakly alkaline range, and a method for cleaning dishes. [Means for solving the problem]

[0008] The present invention relates to a detergent composition for automatic dishwashers, which contains the following components (a) and (b), and water, wherein the mass ratio (a) / (b) of the content of component (a) to the content of component (b) is 0.3 or more and 4.5 or less, and the pH at 25°C is 6 or more and 11 or less: (a) Component: inorganic reducing agent with an oxidation-reduction potential of +71 mV or less (b) Component: Nonionic surfactant

[0009] The present invention also relates to a method for washing tableware, which comprises using an automatic dishwasher to wash soiled tableware with a cleaning liquid prepared by diluting the detergent composition for automatic dishwashers of the present invention with water. [Effects of the Invention]

[0010] According to the present invention, there are provided a detergent composition for automatic dishwashers, which can effectively clean complex soils containing animal proteins and lipids, and also containing vegetable liquid oils, even in a neutral to weakly alkaline range of liquid pH, and a method for cleaning dishes. DETAILED DESCRIPTION OF THE INVENTION

[0011] The reason why the detergent composition for automatic dishwashers and the dish washing method of the present invention can effectively clean complex stains containing animal proteins and lipids and vegetable liquid oils, for example, complex stains containing egg yolk protein and salad oil, when washed in a dishwasher even in a neutral to weakly alkaline range of liquid pH is not entirely clear, but is presumed to be as follows. The present inventors analyzed hard-to-clean protein stains, such as dried egg yolk stains, and found that the difficulty in removing and dispersing the stains with surfactants contained in detergents is due to the presence of disulfide bonds (-SS- bonds) within or between protein molecules in the protein structure, which stabilize the structure and make the protein less susceptible to swelling and dispersion by the surfactant. Therefore, in the present invention, by using a reducing agent (component (a)) with a specific redox potential to cleave disulfide bonds in the protein structure of hard-to-clean protein stains, it is believed that the hard-to-clean protein stains can be easily removed from dishes and dispersed in water, even in the neutral to weakly alkaline range. It is important that the reducing agent (component (a)) has the reducing ability to cleave disulfide bonds. It is believed that a redox potential of +71 mV or less, which is the redox potential of disulfide bonds, is sufficient to cleave disulfide bonds even during short wash times in commercial dishwashers. Furthermore, in actual dishwashing, not only animal protein stains but also vegetable liquid oils are used in cooking, which generally results in the compounding of stains. For example, when the top surface of a stain is covered with liquid oil, the structure makes it difficult for component (a) to act on the protein stains. Therefore, in the present invention, by using component (a) in combination with component (b), which enhances the emulsifying power of vegetable oil, it is believed that a synergistically high cleaning effect can be achieved by removing both liquid oil and protein stains. However, the effects of the present invention are not limited to the mechanism of action shown here.

[0012] [Detergent composition for automatic dishwashers] <Component (a)> Component (a) is an inorganic reducing agent with an oxidation-reduction potential of +71 mV or less. From the viewpoint of protein cleaning ability, the redox potential of component (a) is +71 mV or less, preferably +60 mV or less, more preferably +55 mV or less, and even more preferably +50 mV or less. The lower limit of the redox potential of component (a) is not particularly limited, and the effect can be expected as the potential is lower, but from the viewpoint of availability, it is preferably 0 mV or more, more preferably 3 mV or more. The redox potential of component (a) is measured by the following method. Distilled water is added to component (a) to a concentration of 0.016 mol / L, and 1 mol / L of hydrochloric acid and / or sodium hydroxide is added to adjust the pH to 7.5 to prepare a prepared solution. The temperature of the prepared solution is adjusted to 60°C, and the redox potential is measured using a redox potentiometer (for example, an ORP meter (ORP5 Pen ORP Meter) manufactured by Cem Corporation).

[0013] Component (a) is specifically one or more selected from sulfites, disulfates, thiosulfates, and iodides, and specifically includes one or more selected from sodium sulfite (+50 mV), potassium sulfite (+50 mV), sodium disulfate (+17 mV), potassium disulfate (+17 mV), potassium iodide (+28 mV), sodium iodide (+28 mV), sodium thiosulfate (+5 mV), and potassium thiosulfate (+5 mV). Component (a) is not particularly limited as long as it has a redox potential of +71 mV or less. From the viewpoints of protein cleaning ability and ease of availability, however, it is preferably one or more selected from sodium sulfite, sodium disulfate, potassium iodide, and sodium thiosulfate, and more preferably one or more selected from sodium sulfite, sodium disulfate, and sodium thiosulfate. Note that the value in parentheses indicates the redox potential value.

[0014] <(b) Component> Component (b) is a nonionic surfactant.

[0015] As component (b), from the viewpoint of low foaming properties and emulsifying power for liquid oils, one or more compounds selected from the group consisting of compounds represented by the following general formula (b1), compounds represented by the following general formula (b2), and compounds represented by the following general formula (b3) are preferred, with compounds represented by the following general formula (b1) being more preferred. R 1b -O-[(EO) m / (PO) n ]-H (b1) [In the formula, R 1b represents a hydrocarbon group having 6 to 18 carbon atoms, EO represents an ethyleneoxy group, and PO represents a propyleneoxy group; m represents the average number of moles of EO added; n represents the average number of moles of PO added; m is a number of 1 to 30, and n is a number of 2 to 50. " / " indicates that EO and PO may be added randomly or in blocks, and the order of addition of EO and PO is not important. HO-(EO) a -(PO) b -(EO) c -H (b2) HO-(PO) d -(EO) e -(PO) f -H (b3) (In the formula, EO represents an oxyethylene group, PO represents an oxypropylene group, and a, b, c, d, e, and f represent the average number of moles added, each independently being a number of 2 or more and 30 or less.)

[0016] R in general formula (b1) 1b is a hydrocarbon group having 6 to 18 carbon atoms, preferably an alkyl group or an alkenyl group, more preferably a linear alkyl group or a branched alkyl group, and even more preferably a branched alkyl group. 1b Examples of the branched alkyl group include a branched primary alkyl group and a branched secondary alkyl group, and a branched secondary alkyl group is preferred. A branched primary alkyl group is a residue obtained by removing a hydroxyl group from a branched primary alcohol, and R in general formula (b1) 1b R bonded to O- in O- 1bThe carbon atom in the branched chain secondary alkyl group is a residue obtained by removing a hydroxyl group from a secondary alcohol, and R in the general formula (b1) 1b R bonded to O- in O- 1b The carbon atom is a secondary carbon atom. R 1b From the viewpoint of the emulsifying power of the liquid oil and the uniform stabilization of the detergent composition, the number of carbon atoms is 6 or more, preferably 8 or more, more preferably 10 or more, even more preferably 12 or more, and is 18 or less, preferably 16 or less, more preferably 14 or less.

[0017] In addition, in general formula (b1), the average number of moles of EO added, m, is 1 or more, preferably 3 or more, more preferably 5 or more, and is 30 or less, preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less, from the viewpoints of emulsifying power for liquid oil, anti-foaming property during washing, and uniform stabilization of the cleanser composition. In addition, in general formula (b1), the average number of moles of PO added, n, is 2 or more, preferably 5 or more, more preferably 7 or more, and is 50 or less, preferably 40 or less, more preferably 30 or less, even more preferably 20 or less, and still more preferably 10 or less, from the viewpoints of the emulsifying power of liquid oil and the foam-suppressing property during washing.

[0018] In general formulas (b2) and (b3), a, b, c, d, e, and f represent the average number of moles added, and are each independently a number of 1 or more, preferably 2 or more, more preferably 5 or more, and 30 or less, preferably 25 or less, more preferably 20 or less, from the viewpoint of the emulsifying power of the liquid oil and the foam-suppressing ability during washing. In the compound represented by general formula (b2) or (b3), from the viewpoint of the emulsifying power for liquid oils and the foam-suppressing property during washing, the EO content of the total of EO and PO is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and preferably 90 mol% or less, more preferably 70 mol% or less, even more preferably 60 mol% or less, still more preferably 50 mol% or less, still more preferably 40 mol% or less, still more preferably 30 mol% or less, and still more preferably 25 mol% or less, and it is preferable to select a, b, c, d, e, and f so as to satisfy this.

[0019] In the compound represented by general formula (b2) or (b3), the weight-average molecular weight is preferably 500 or more, more preferably 700 or more, even more preferably 1000 or more, still more preferably 2000 or more, and is preferably 20000 or less, more preferably 10000 or less, still more preferably 8000 or less, still more preferably 6000 or less, and still more preferably 4000 or less, from the viewpoints of emulsifying power for liquid oil, anti-foaming property during washing, and uniform stability of the formulation.

[0020] The compound represented by general formula (b2) is available from ADEKA Corporation under the trade name "Pluronic." The compound represented by general formula (b3) is available from BASF under the trade name "Pluronic R."

[0021] <Composition, etc.> From the viewpoint of cleaning ability for proteins in complex soils containing proteins and liquid oil, the detergent composition for automatic dishwashers of the present invention may contain component (a) in an amount of preferably 0.5% by mass or more, more preferably 0.7% by mass or more, even more preferably 1% by mass or more, still more preferably 2% by mass or more, and preferably 20% by mass or less, more preferably 18% by mass or less, even more preferably 15% by mass or less, still more preferably 10% by mass or less, still more preferably 5% by mass or less, and still more preferably 3% by mass or less.

[0022] From the viewpoint of cleaning ability for liquid oil in complex soils containing protein and liquid oil, the detergent composition for automatic dishwashers of the present invention may contain component (b) in an amount of preferably 0.6% by mass or more, more preferably 0.7% by mass or more, even more preferably 0.8% by mass or more, still more preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 18% by mass or less, even more preferably 15% by mass or less, still more preferably 10% by mass or less, still more preferably 5% by mass or less, and still more preferably 3% by mass or less.

[0023] In the detergent composition for automatic dishwashers of the present invention, the mass ratio (a) / (b) of the content of component (a) to the content of component (b) is 0.3 or more, preferably 0.5 or more, more preferably 1 or more, and 4.5 or less, preferably 4 or less, more preferably 3 or less, even more preferably 2 or less, and still more preferably 1.5 or less, from the viewpoints of the cleaning ability for complex soils containing protein and liquid oil and the finish of tableware after washing.

[0024] In the detergent composition for automatic dishwashers of the present invention, the ranges of the contents of component (a) and component (b) can be set by arbitrarily selecting and combining the values ​​described above.

[0025] From the viewpoint of reducing the risk of chemical burns, the detergent composition for automatic dishwashers of the present invention has a pH at 25°C of 6 or more, preferably 6.2 or more, more preferably 6.5 or more, and 11 or less, preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less. This pH is measured by the following method. (1) pH measurement method A pH measurement composite electrode (e.g., a glass-ground sleeve type manufactured by Horiba, Ltd.) with a saturated potassium chloride aqueous solution (3.33 mol / L) as the pH electrode internal solution is connected to a pH meter (e.g., a pH / ion meter F-23 manufactured by Horiba, Ltd.). Next, a pH 4.01 standard solution (phthalate standard solution), a pH 6.86 standard solution (neutral phosphate standard solution), and a pH 9.18 standard solution (borate standard solution) are each filled into a 100 mL beaker and immersed in a thermostatic bath at 25°C for 30 minutes. The pH measurement electrode is immersed in the thermostatically adjusted standard solution for 3 minutes, and calibration is performed in the order of pH 6.86 → pH 9.18 → pH 4.01. The automatic dishwasher detergent composition to be measured is adjusted to 25°C, and the electrode of the pH meter is immersed in the sample, and the pH is measured after 1 minute.

[0026] From the viewpoints of reducing the risk of chemical burns and reducing the environmental load by lowering the pH of wastewater, the detergent composition for automatic dishwashers of the present invention has a pH at 25°C of preferably 6 or more, more preferably 6.5 or more, and preferably 10.5 or less, more preferably 9 or less, and even more preferably 8 or less, when diluted with water to a concentration of 0.2% by mass. This pH is measured by the above-mentioned method (wherein "detergent composition for automatic dishwashers" is read as a diluted version of the detergent composition for automatic dishwashers).

[0027] The detergent composition for automatic dishwashers of the present invention preferably contains water from the viewpoint of the stability and workability of the composition. The water is not particularly limited, but examples thereof include tap water, well water, ion-exchanged water, and distilled water. The water is preferably used in an amount that makes up the remainder of the composition (amount that makes the total 100% by mass). The water content of the composition can be, for example, 20% by mass or more, further 30% by mass or more, further 50% by mass or more, further 55% by mass or more, further 60% by mass or more, further 65% by mass or more, or even 70% by mass or more.

[0028] The detergent composition for automatic dishwashers of the present invention may contain components such as surfactants, enzymes (protease, olease, carbohydrate-degrading enzyme, etc.), solvents, hydrotropes, dispersants, pH adjusters, thickeners, viscosity modifiers, fragrances, colorants, antioxidants, preservatives, foam suppressors, bleaches, bleach activators, etc. (excluding those corresponding to components (a) and (b)) within the scope of the present invention.

[0029] The viscosity of the detergent composition for automatic dishwashers of the present invention at 20°C may be, for example, 1200 mPa·s or less, or even 1000 mPa·s or less, from the viewpoint of ensuring a stable supply of the detergent using a detergent dispenser. The lower limit of the viscosity may be 0 mPa·s or more. This viscosity is measured using a Brookfield viscometer.

[0030] In the present invention, tableware refers to: (i) In addition to so-called tableware such as plates, bowls, cups, chopsticks, knives, forks, and spoons, (ii) Storage containers such as Tupperware and bottles, (iii) Cooking utensils such as knives, cutting boards, pots, frying pans, and fish grills; (iv) Storage or transport equipment such as racks, containers, etc. It may also mean parts or utensils that come into contact with food ingredients, such as:

[0031] <How to wash dishes> The present invention provides a method for washing tableware, which comprises using an automatic dishwasher to wash soiled tableware with a cleaning liquid (hereinafter referred to as the cleaning liquid of the present invention) prepared by diluting the detergent composition for automatic dishwashers of the present invention with water. The items described for the detergent composition for automatic dishwashers of the present invention can be appropriately applied to the dishwashing method of the present invention. Component (a), component (b), mass ratio (a) / (b), pH, specific examples and preferred examples of tableware are also the same as those for the detergent composition for automatic dishwashers of the present invention.

[0032] The cleaning liquid of the present invention may be prepared by diluting the detergent composition for automatic dishwashers of the present invention with water more than 1-fold, further 300-fold or more, and 2000-fold or less, further 1500-fold or less.

[0033] From the viewpoint of protein cleansing ability in complex soils containing protein and liquid oil, the cleaning solution of the present invention may contain component (a) in an amount of preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more, even more preferably 0.0003% by mass or more, still more preferably 0.0005% by mass or more, still more preferably 0.001% by mass or more, still more preferably 0.002% by mass or more, still more preferably 0.003% by mass or more, and preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and still more preferably 0.01% by mass or less.

[0034] From the viewpoint of cleaning ability of liquid oil in complex soils containing protein and liquid oil, the cleaning solution of the present invention can contain component (b) in an amount of preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more, even more preferably 0.0003% by mass or more, still more preferably 0.0005% by mass or more, still more preferably 0.001% by mass or more, still more preferably 0.002% by mass or more, still more preferably 0.003% by mass or more, and preferably 2% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and still more preferably 0.01% by mass or less.

[0035] In the present invention, the ranges of the contents of the components (a) and (b) in the cleaning solution can be set by arbitrarily selecting and combining the values ​​described above.

[0036] From the viewpoint of reducing the risk of chemical burns and reducing the environmental load by reducing the pH of the wastewater, the pH of the cleaning solution of the present invention is preferably 6 or more, more preferably 6.2 or more, even more preferably 6.5 or more, and preferably 10.5 or less, more preferably 10.2 or less, even more preferably 10 or less, and even more preferably 9 or less.

[0037] In the dish washing method of the present invention, the dish is contacted with the washing liquid for, for example, 20 seconds or more, further 30 seconds or more, further 40 seconds or more, and then 600 seconds or less, further 300 seconds or less, further 180 seconds or less, from the viewpoint of cleaning ability of complex soils containing protein and liquid oil.

[0038] In the tableware washing method of the present invention, the temperature of the washing liquid can be, for example, 30°C or higher, further 35°C or higher, further 40°C or higher, and 90°C or lower, further 80°C or lower, further 70°C or lower.

[0039] In the dishwashing method of the present invention, the flow rate of the cleaning liquid when contacting the dishwashing liquid is preferably 5 m / min or more, more preferably 10 m / min or more, even more preferably 50 m / min or more, from the viewpoint of cleaning ability of complex soils containing protein and liquid oil, and is preferably 2000 m / min or less, more preferably 1000 m / min or less, more preferably 500 m / min or less.

[0040] The dish washing method of the present invention is intended to wash complex soils containing animal proteins and lipids, as well as vegetable liquid oils. The stain containing animal protein and lipid may be, for example, a stain containing protein and lipid derived from egg yolk. The stain containing vegetable liquid oil may be, for example, a stain containing liquid oil such as salad oil.

[0041] After the dishware is contacted with the cleaning solution, the dishware is rinsed with water at a temperature of 50°C or higher, preferably 55°C or higher, more preferably 60°C or higher, and 80°C or lower. The rinsing time for the dishes is 4 seconds or more, preferably 5 seconds or more, and 10 seconds or less, preferably 9 seconds or less. The flow rate of the rinse water is preferably 5 m / min or more, more preferably 10 m / min or more, even more preferably 100 m / min or more, and preferably 2500 m / min or less, more preferably 2000 m / min or less, even more preferably 1500 m / min or less, even more preferably 250 m / min or less, and still more preferably 150 m / min or less.

[0042] In the present invention, the automatic dishwasher may be any dishwasher generally available on the market, and although a household automatic dishwasher may be used, a commercial automatic dishwasher is preferred. When washing with a commercial dishwasher, the detergent composition for automatic dishwashers of the present invention is generally used as a cleaning liquid mixed with water. In this case, the composition is arbitrarily transferred in a fixed amount into the commercial dishwasher by a supply device, and an appropriate concentration of the cleaning liquid is maintained. The detergent composition for automatic dishwashers of the present invention is supplied, for example, by inserting a tube dedicated to commercial dishwashers directly into a container such as a plastic container filled with the composition and sucking it up. The cleaning liquid is then supplied into the commercial dishwasher. [Example]

[0043] The ingredients used in the examples and comparative examples are listed below.

[0044] <Component (a)> Sodium sulfite: oxidation-reduction potential 50 mV, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Sodium disulfate: Oxidation-reduction potential 17 mV, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Potassium iodide: Oxidation-reduction potential 28 mV, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Sodium thiosulfate: Oxidation-reduction potential 5mV, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0045] <Component (a') (comparison component of component (a))> Sodium dithionite: oxidation-reduction potential 76 mV, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Thiourea dioxide: Oxidation-reduction potential 147mV, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Glutathione: Oxidation-reduction potential -90mV, Fujifilm Wako Pure Chemical Industries, Ltd.

[0046] The oxidation-reduction potentials of the components (a) and (a') were measured by the following method. A solution was prepared by adding distilled water to component (a) or (a') to a concentration of 0.016 mol / L, and adjusting the pH to 7.5 with 1 mol / L hydrochloric acid and / or sodium hydroxide. The temperature of the solution was adjusted to 60°C, and the oxidation-reduction potential was measured using an ORP meter (ORP5 Pen ORP Meter) manufactured by Cem Corporation.

[0047] <(b) Component> SOFTANOL EP7085: In the general formula (b1), R 1b is a branched secondary alkyl group with 12 to 14 carbon atoms, m is 7, n is 8.5, and is a compound in which ethyleneoxy groups and propyleneoxy groups are block-added in this order, "SOFTANOL EP7085" manufactured by Nippon Shokubai Co., Ltd. Emulgen LS-106: In the general formula (b1), R 1b is a compound in which ethyleneoxy and propyleneoxy groups are block-added in this order, with a primary alkyl group having 12 to 14 carbon atoms, m being 6, and n being 1.5. Kao Corporation's "Emulgen LS-106" Pluronic RPE2520: Compound represented by general formula (b3), weight average molecular weight 3,100, propylene oxide / ethylene oxide ratio = 80 / 20, "Pluronic RPE2520" manufactured by BASF Japan Ltd.

[0048] The cleaning power for complex soiling containing egg yolk and salad oil was evaluated using the detergent compositions for automatic dishwashers shown in Table 1 according to the following procedure. The results are shown in Table 1. The pH of the compositions in Table 1 was adjusted by adding sodium hydroxide and / or sulfuric acid as necessary.

[0049] (1) The mass (mass A) of a SUS stainless steel tray (external dimensions: width 258 mm x depth 177 mm x height 18 mm, internal bottom dimensions: 235 mm x 155 mm) was measured. (2) 1.5 g of egg yolk was spread evenly over an area of ​​180 mm x 100 mm on the bottom of the stainless steel tray with a brush. This was then left to dry for 30 minutes in a constant temperature bath FC-612 manufactured by ADVANTEC Co., Ltd., heated to 30°C. After drying, 1.5 g of salad oil manufactured by Nisshin Oillio Group, Inc. was spread over an area of ​​235 mm x 155 mm on the bottom of the stainless steel tray. (3) The mass (mass B) of the stainless steel tray after the salad oil was spread was measured. (4) Using a JWE-680A dishwasher manufactured by Hoshizaki Electric Co., Ltd., a stainless steel tray coated with egg yolk and salad oil was washed with a detergent composition for automatic dishwashers shown in Table 1 diluted with water to 0.2% by mass to prepare a cleaning solution, at 60°C for 40 seconds at a flow rate of 270 m / min, and then, a few seconds later, rinsed with 80°C rinse water for 6 seconds at a flow rate of 1000 m / min. A portion of the cleaning solution was sampled and the pH was measured at 25°C. (5) The mass of the stainless steel tray after washing (mass C) was measured, and the cleaning rate of complex protein and lipid soiling was calculated from the mass change rate. The mass change rate can be calculated using the following formula. The cleaning rate results are shown in Table 1. A cleaning rate of 85% or more is preferred. Mass change rate (%) = [[BC] / [BA]] x 100 (6) After cleaning, both sides of the stainless steel tray were checked for cloudiness due to residual oil. The results are shown in Table 1.

[0050] [Table 1]

Claims

1. A detergent composition for automatic dishwashers, comprising the following components (a) and (b), and water, wherein the content of component (a) is 2% by mass or more and 20% by mass or less, the mass ratio (a) / (b) of the content of component (a) to the content of component (b) is 0.3 or more and 4.5 or less, and the pH at 25°C is 6 or more and 11 or less: Component (a): one or more inorganic reducing agents selected from sulfites, disulfates, and thiosulfates, each having an oxidation-reduction potential of +71 mV or less Component (b): Nonionic surfactant

2. 2. The detergent composition for automatic dishwashers according to claim 1, wherein component (a) is one or more inorganic reducing agents selected from sulfites, disulfates, and thiosulfates, each of which has an oxidation-reduction potential of 0 mV or more and +71 mV or less.

3. 3. The detergent composition for an automatic dishwasher according to claim 1, wherein the component (a) is at least one selected from the group consisting of sodium sulfite, potassium sulfite, sodium disulfite, potassium disulfate, sodium thiosulfate, and potassium thiosulfate.

4. 3. The detergent composition for an automatic dishwasher according to claim 1, wherein component (b) is a compound represented by the following general formula (b1): 2 1ｂ --[(5O) ｍ / (O) ｎ )-2(b1) [In the formula, R 1ｂ represents a hydrocarbon group having 6 to 18 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, m represents the average number of moles of EO added, n represents the average number of moles of PO added, m is a number of 1 to 30, and n is a number of 2 to 50. " / " indicates that EO and PO may be added randomly or in blocks, and the order of addition of EO and PO is not important.

5. 3. The detergent composition for automatic dishwashers according to claim 1, which has a pH of 6 or more and 8 or less at 25°C.

6. A method for washing tableware, comprising using an automatic dishwasher to wash soiled tableware with a cleaning liquid prepared by diluting the detergent composition for an automatic dishwasher according to claim 1 or 2 with water.

7. 7. The method for washing tableware according to claim 6, wherein the cleaning liquid is prepared by diluting the dishwasher detergent composition according to claim 1 or 2 with water at a ratio of more than 1 to 2000 times.

8. The method for washing tableware according to claim 6, wherein the washing liquid is brought into contact with the tableware for 20 seconds or more and 600 seconds or less.

9. 7. The method for washing tableware according to claim 6, wherein the temperature of the washing liquid is 30°C or higher and 90°C or lower.

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