A CLEANING COMPOSITION COMPRISING LIPASE AND AMYLASE ENZYMES

Abstract: A novel liquid enzyme cleaning composition for removing heated food soils such as those found in ovens, and the method of its use by application of the composition to a cool surface bearing such food soils. The composition includes enzymes that are active in the pH range 10-14 and comprise a mixture of a lipase and an amylase, and, optionally, a protease. The composition also contains an alkali metal silicate. The composition preferably contains non-ionic surfactant and is buffered.

Description: A CLEANING COMPOSITION COMPRISING LIPASE AND AMYLASE ENZYMES FIELD OF THE INVENTION This invention relates to cleaning compositions, and particularly to cleaning compositions for use on ovens. BACKGROUND ART Cleaning compositions for use on surfaces that have been subjected to spattering by food products at high temperatures are well known. Such surfaces, for example in ovens, quickly become coated with food residues that can become baked on at high temperatures. These residues from food subjected to high temperatures will be described herein as bumt-on food soils. Removal of burnt-on food soils is considerably more difficult than removal of food stains from, for example, textile materials. The high temperatures to which such food soils have been subjected causes their removal to require very aggressive chemical compositions that are usually either very acidic or more usually very alkaline. In particular, known oven cleaning compositions tend to have a quite extreme pH and particularly tend to be strongly alkaline since it has been believed that burnt-on food soils can only be removed by such aggressive materials. These compositions are often used under severe treating conditions, including oxidizing and reducing conditions at high temperatures. Cleaning compositions have been proposed that contain active enzymes, such as washing powders and detergents. However, these compositions typically have been proposed for washing conditions appropriate for textile materials, for example temperatures below 55°C and pH's below 1 1. SUMMARY OF THE INVENTION The liquid, enzyme-based cleaning composition of the invention is summarized in that it includes a lipase enzyme active at a pH of from 10 to 14; an amylase enzyme also active at a pH of from 10 to 14; at least one alkali-stable non-ionic or anionic surfactant; an alkali metal silicate; and an inert diluent. The composition is buffered at a pH of 10 to 14. The method of the invention is summarized in that a method of cleaning a surface bearing burnt-on food soils includes the steps of applying the composition of claim 1 to the food soils at a cool surface temperature; allowing the food soils to soften; and removing the food soils. Preferably the surface temperature does not exceed about 50°C. DETAILED DESCRIPTION OF THE INVENTION According to the present invention there is provided a cleaning composition for burnt- on food soils, particularly suitable for use on ovens, that is enzyme based. The enzyme component is active in the pH range of 10-14. Incorporation of enzymes into cleaning compositions of this type would not normally have been considered since enzymes are known to be rather fragile and to be deactivated rather easily. It is surprising to find an enzyme-containing composition that is effective particularly at pH's in excess of 10. According to the present invention, there is provided an enzyme-based cleaning composition comprising a lipase enzyme, an amylase enzyme, an alkali-metal silicate, and an alkali-stable surfactant, which composition is buffered to maintain the pH of the composition in the range from 10-14, and preferably from 10-12.5. The optimum pH is approximately 12.5. The invention also provides a method of cleaning surfaces that have been subjected to food residues at high temperatures, such as ovens and other cooking surfaces, utilizing the said enzymatic composition for cleaning . All amounts stated in this description are based on the total weight of the composition of the invention. The enzymes used in the invention are preferably alkaliphilic. If enzymes so designated are not commercially available, enzymes can be selected on the basis of activity against the relevant components of the soil (e.g. amylase against starch components) as a function of pH. Those skilled in the art can readily identify commercially or otherwise available enzymes with sufficient activity at the pH of the composition to be useful as components of a cleaning composition and particularly those that would have an activity at the optimum pH of the product, 12.5. Lipase enzymes used in the present invention are those enzymes that promote hydrolysis of triglycerides into mono and diglycerides, glycerol, and free fatty acids, all of which are more soluble than the original fat triglyceride. A number of different lipase enzymes are commercially available, having been used in fabric cleaning formulations for the removal of fat-containing stains such as the stains resulting from cooking fat, salad oils, butter, and fat based sauces. A preferred lipase for use in the present invention is Lipolase, manufactured by Novo Nordisk Industry. This is a 1,3 -specific lipase that cleaves ester bonds in the positions 1 and 3 of a triglyceride. Amylase enzymes are those that hydrolyze starches to soluble dextrins and oligosaccharide. Amylases have been used in fabric cleaning compositions to remove starch- containing stains, such as those made from pasta, chocolate, and gravy products, by way of example, only. Amylase enzymes hydrolyze 1 ,4-alpha glucosidic bonds in an amylose or amylopectin. A preferred amylase is Termamyl® which is a commercially available enzyme manufactured by Novo Nordisk Industry, being alpha amylase prepared by fermentation of Bacillus licheniformis. The composition of the invention can contain a protease as an optional, additional enzyme. Proteases are enzymes that hydrolyses protein to peptides that can be readily dissolved. Proteases have previously been incorporated into fabric cleaning compositions such as laundry detergents. A preferred protease is the commercial product Savinase® also available from Novo Nordisk Industry. Savinase® is a proteolytic enzyme prepared by submerged fermentation of an alkalophilic species of Bacillus and is an endo-protease of the serine type, with broad substrate specificity. Each of the enzymes types used are present in from 0.1 to 4% by weight of the composition. The particular enzymes disclosed above are only non-limiting examples of their types. It should be noted that a wide range of commercially available lipase, amylase, and protease enzymes are available. Since the compositions of the invention are generally intended for oven cleaning, they should be of sufficient viscosity to hold them on a vertical surface for an effective time, i.e. for a time sufficient to effect or at least facilitate the removal of burnt-on food soils. In order to achieve such a viscosity, it may be necessary to add a thickener, in addition to the other components of the composition. The amount of the thickener will depend on the nature of the thickener itself and of the other components in the composition. It may be that the other components in the composition, along with their other properties, also will act as a thickener for the purpose of giving the appropriate viscosity to the composition, making unnecessary the addition of a separate component specifically as a thickener. A composition primarily intended for application to burnt-on food soils on horizontal surfaces, such as stove tops, could be in a more fluid form. When present as a separate component that is provided primarily to increase composition viscosity, the thickener should be present in the range of from 0.05 to 6 percent by weight and preferably from 0.2 to 6 percent. The thickeners can be selected from the group consisting of inorganic materials, organic polymeric materials, and compatible mixtures thereof. Suitable inorganic thickeners include, by way of example only, colloidal silica, smectite clays such as bentonite, attapulgite, Laponite, magnesium alumino-silicate, and compatible mixtures thereof. Polymeric organic thickeners can be biopolymers (such as xanthan or welan gum) or synthetic polymers (such as polyacrylates or hydrophobically modified polyurethane). Commercially available examples of such synthetic polymers may be selected from the CARBOPOL® polymers produced by B.F. Goodrich or the RHEOVIS® polymers available from Allied Colloids. Preferably the thickener is a crosslinked polyacrylate. Commercial examples of crosslinked polyacrylates may be selected from the ACRYSOL ® polymers produced by Rohm & Haas. When the thickener is a hydrophobically modified polyurethane thickener, it should more preferably be present in the range of from 1 to 2 percent by weight. The alkali metal silicate compounds in the composition assist in fat break-down and provide alkalinity. They also assist as detergent builders and act as corrosion inhibitors. Particular alkali metal silicates that can be employed are those having a Na 2 O:SiO ratio in the range 1 :2 to 2: 1. The optimum range is from 1 : 1 to 2: 1. These alkali metal silicates will usually be present in the range 5-35 weight percent and preferably 5-25 weight percent, although the precise amount may depend on the nature of the surfactant. The amount of silicate will also be determined to some extent by the nature of the buffer used. Thus the preferred buffer employing an alkali metal carbonate, and preferably sodium carbonate, may allow a reduced amount of silicate to be present. Decreasing the amount of silicate present, though it cannot be reduced to 0, is advantageous in that it reduces the amount of electrolyte, which increases the shelf life of the formula. Also, silicates sometimes have adverse effects on skin, making it desirable to reduce the amount of silicates so as to minimize the side effects of the composition, should it come in contact with unprotected skin. The composition of the invention must be buffered, although it may be that components in the composition, e.g. the silicate, will provide a sufficient buffering effect so as not to require an independent buffer. The buffer components in the composition should be selected to retain the composition's pH in the range of from 10-14, preferably from 10-13, and optimally at about 12.5. If a specific buffer is required, a wide variety of buffer compositions are available and known to those skilled in the art. Carbonate buffers and particularly alkali metal (e.g. sodium) carbonate buffers are preferred because of the high pH of the composition. Preferably carbonate is added in amounts ranging from 0.5 to 12 weight percent. To enable the composition to wet and penetrate the materials to be removed, the composition preferably contains a surfactant. Preferred surfactants are those that are alkali stable and have an HLB (hydrophile-lipophile balance) in the range of 12-20 and preferably in the range 13-16. The HLB is a measure of the relative water solubility of the surfactant and gives an indication of the relative proportions of hydrophobic and hydrophilic portions in the molecule. The surfactants preferably are non-ionic, but anionic surfactants may be used. It is only rarely that a cationic surfactant will be operable. Preferable non-ionic surfactants include nonyl phenol ethoxylates (preferably 9 and 20 mole ethoxylates), alkyl glucosides, Cl 1 oxo-alcohol ethoxylates containing at least 7 moles of ethylene oxide, short chain fatty acid polyethylene glycol ethers containing at least 5 moles of ethylene oxide, and iso-C13 oxo-alcohol ethoxylates containing at least 8 moles of ethylene oxide, or compatible mixtures thereof. Alkyl and aryl capped materials can also be employed. Typical anionic surfactants are alkaline metal and alkylolamine alkyl sulfonates, paraffin sulfonates, and alkaline metal alkyl phenol sulfonates. Normally one would use either an anionic surfactant or a non-ionic surfactant, as mixtures of anionic and non-ionic surfactants tend to be ineffective. Mixtures of surfactants are not normally compatible because of the high alkalinity, tending to separate. However, by very careful choice of the appropriate surfactant system, anionic/non-ionic surfactant mixtures are possible and are not excluded from the invention. The amount of surfactant present is usually from 0.5 to 10 weight percent. With anionic surfactants, it is also desirable that a co-builder be present, partly to assist in avoiding the salting-out of the surfactant. A wide variety of co-builders are used with anionic surfactants in the various applications of these surfactants. Preferred co-builders that are useful for anionic systems are alkali metal polyphosphates, alkali metal salts of organic acids, and alkali metal salts of polymeric acids. More preferably the co-builder is at least one of STPP (sodium tri polyphosphate) and alkali metal salts of citric acid, gluconic acid, polyacrylic acid, and modified polyacrylic acid. Compatible mixtures of the above mentioned co-builders can.be utilized. In addition, the silicate component of the composition can contribute as a co-builder. Preferably the co-builder (other than the silicate component) is present in the amount of 0.5-12 percent by weight. Co-builders are usually less necessary in non-ionic surfactant systems since there is less likelihood of inactivation by calcium ions. Nevertheless, co-builders may still be necessary if it is found that the calcium ions present in the composition are having an adverse effect. Preferably the compositions include hydrotropes, i.e. compounds that have the property of increasing the aqueous solubility of any insoluble organic chemicals present. Useful hydrotropes are cumenesulfonate, sodium zylene sulphonate, phosphate esters, and sodium toluene sulphonate. Compatible mixtures of the above mentioned hydrotropes can be used if desired. Preferably said hydrotropes are present in the amount of 0.2-2.5 percent by weight. Removal of burnt-on food soils can be enhanced by the use of penetrating solvents. The presence of these solvents also can assist in stabilizing the enzyme content of the composition. Suitable solvents are those organic liquids that soften and penetrate into resin- type materials, for example those solvents found in paints. The particularly preferred solvents are those that are found also to enhance the stability of the enzymes. Suitable solvents are glycol ethers (e.g. those sold under the trade name Cellosolve), esters, glycol ether acetates, methyl pyrrolidone, and l,3-dimethyl-2-imidazolidinone. Compatible mixtures of the above mentioned solvents can be used. More preferably, the mentioned solvents are present in the amount of from 2-10 percent by weight. The compositions of the invention can contain other conventional cleaning composition components, if they do not materially detrimentally affect the enzymatic properties of the system. Such components include, for example, sequestering agents, dyes, bleaches, bleach activators, foam control agents, and fragrances. The composition of the invention also includes appropriate diluents for application, although the composition may be prepared in a concentrated form for dilution prior to use. The preferred diluent (apart from the penetrating solvents discussed above) is water and will usually comprise at least 70% and preferably at least 75% by weight of the composition. The composition of the invention can be applied directly without further dilution, for example by water, and can be applied by brushing or by spraying from a spray device, including an aerosol dispenser. In the case of an aerosol dispenser, the inclusion of a foaming agent in the composition will result in a foam that covers the surface to be treated. The surface to be treated should preferably be cold, which shall mean commonly experienced room temperatures. If warm, the surface should not be of a temperature sufficiently high as to be deleterious to the enzymes in the composition. Temperatures not in excess of 50°C are preferred. The invention will be illustrated by the following Examples. EXAMPLE 1. The following were combined in the stated percentages by weight. Compositions described in Columns A and B are examples of specific formulations that have been made, while Column C states the preferred ranges of ingredients: Name Percentage Comp Comp Δ B. ACRYSOL* ICS-I - 5.0 5.0 0.05-6 A commercial polyacrylate resin supplied by Rohm & Haas. Sodium Metasilicate - 5.0 5.3 5-35 A commercial product METSO 510* supplied by Crosfields Pic ETHYLAN* BAB 20 - 1.0 1.1 0.5-10 Nonionic surfactant supplied by Akcros Chemicals Hexyl CELLOSOLVE* - 3.0 2.7 2-10 Ethylene glycol monohexyl ether supplied by Union Carbide Sodium Carbonate 1.5 1.2 0.5-12 Sodium Citrate 5.0 3.8 0.5-12 LIPOLASE* 100L TYPE EX - 2.5 2.5 0.1-4 A commercial lipase supplied by Novo Nordisk Industries TERMAMYL* 300 TYPE DX - 2.0 2.0 0.1-4 A commercial amylase supplied by Novo Nordisk Industry Water 75.00 76.4 70-75 * Trade Name or Registered Trade Mark The compositions of Example 1 were viscous fluids which, when applied to the vertical walls of an oven, remained in position for sufficient time to effect cleaning. When the compositions were applied to a surface contaminated with burnt-on food soils in a test of the type recommended by the Vitreous Enamel Council, the soils softened and were easily removable after 16 hours. EXAMPLE 2, The following were combined in the stated percentages by weight. The composition described in Column A is an example of a specific formulation that has been made, while Column B states the preferred ranges of ingredients: Name Percentage Δ fi CarbopolS 2.0 0.05-6 A commercial cross-linked polyacrylate supplied by B. F. Goodrich Sodium Metasilicate - 5.3 5-35 A commercial product METSO 510* supplied by Crosfields Pic ETHYLAN* BAB 20 - 1.0 0.5-10 Nonionic surfactant supplied by Akcros Chemicals Hexyl CELLOSOLVE* - 2.6 2-10 Ethylene glycol monohexyl ether (supplied by Union Carbide) Sodium Carbonate 1.1 0.5-12 Sodium Citrate 3.8 0.5-12 LIPOLASE* 100L TYPE EX - 2.5 0.1-4 A commercial lipase supplied by Novo Nordisk Industry TERMAMYL* 300 TYPE DX - 2.0 0.1 -4 A commercial amylase supplied by Novo Nordisk Industry Water 79.7 70-75 * Trade Name or Registered Trade Mark The composition of Example 2 was a viscous fluid which, when applied to the vertical walls of an oven, remained in position for sufficient time to effect cleaning. When applied to a surface contaminated with burnt-on food soils in a test of the type recommended by the Vitreous Enamel Council, the soils softened and were easily removable after 16 hours. The invention is not limited to the Examples, which are only illustrative. Instead, the invention is in accordance with the claims.

Claims: CLAIMS 1. A liquid, enzyme-based cleaning composition comprising: i) a lipase enzyme active at a pH of from 10 to 14; ii) an amylase enzyme active at a pH of from 10 to 14; iii) at least one alkali-stable non-ionic or anionic surfactant; iv) an alkali metal silicate; and v) an inert diluent; the composition being buffered at a pH of 10 to 14. 2. A composition according to claim 1 that also contains a protease active at a pH of 10 to 14. 3. A composition according to claim 1 that is sufficiently viscous to remain on a vertical surface for an effective time sufficient to so soften bumt-on food soils on the surface as to aid in their removal therefrom. 4. A cleaning composition according to claim 3 containing a thickening agent. 5. A cleaning composition according to claim 1 that contains an anionic surfactant and a co-builder. 6. A cleaning composition according to claim 1 , wherein said composition further includes a hydrotrope. 7. A cleaning composition according to claim 1 that further includes a penetrating, enzyme-stabilizing organic solvent. 8. A cleaning composition according to claim 7, wherein said solvent is selected from the group consisting of glycol ethers, esters, glycol ether acetates, N-methyl pyrrolidine, 1,3- dimethyl-2-imidazolodinone, and compatible mixtures thereof. 9. A cleaning composition according to claim 1 , further including a protease active at pH 10 to 14, a thickener, a hydrotrope, and an anionic surfactant and co-builder, wherein the following components are present in the following amounts based on the total weight of said composition: i) said lipase enzyme is present in the amount of 0.1 to 4 weight %; ii) said amylase enzyme is present in the amount of 0.1 to 4 weight %; iii) said protease is present in the amount of 0.1 to 4 weight %; iv) said thickening agent is present in the amount of 0.05 to 6 weight %; v) said anionic surfactant is present in the amount of 0.5 to 10 weight %; vi) said hydrotrope is present in the amount of 0.2 to 2.5 weight %; vii) said alkali metal silicate is present in the amount of 5 to 35 weight %; viii) said co-builder is present in the amount of 0.5 to 12 weight %; ix) -said penetrating solvent is present in the amount of 2 to 10 weight %; and the balance is inert diluent and ancillary ingredients. 10. A cleaning composition according to claim 1 , wherein said lipase enzyme and said amylase enzyme are present in amounts such that the weight ratio of said lipase enzyme to said amylase enzyme lies in the range 1 :2 to 3: 1. 11. A cleaning composition according to claim 4, wherein the thickening agent is selected from the group consisting of an inorganic thickener, an organic polymeric thickener, a hydrophobically modified polyurethane thickener, and compatible mixtures thereof. 12. A cleaning composition according to claim 11, wherein said thickening agent is an inorganic thickener selected from the group consisting of colloidal silica, bentonite, attapulgite, laponite, magnesium alumino-silicate, and compatible mixtures thereof. 13. A cleaning composition according to claim 11, wherein said thickening agent is an organic polymeric thickener selected from the group consisting of xanthan gum, welan gum, a cross-linked polyacrylate polymer, and compatible mixtures thereof. 14. A cleaning composition according to claim 1 , wherein the surfactants have a combined HLB within the range of 12-20. 15. A cleaning composition according to claim 14, wherein said surfactants include a non-ionic surfactant selected from the group consisting of nonyl phenol ethoxylates, alkyl glucosides, Cl 1 oxo-alcohol ethoxylates containing at least 7 moles of ethylene oxide, short chain fatty acid polyethylene glycol ethers containing at least 5 moles of ethylene oxide, iso- C13 oxo-alcohol ethoxylates containing at least 8 moles of ethylene oxide, and compatible mixtures thereof. 16. A cleaning composition according to claim 14, wherein said surfactants include an anionic surfactant selected from the group consisting of alkali metal alkyl sulphonates; alkylolamine alkyl sulphonates; paraffin sulphonates; alkali metal alkyl phenol sulphonates; and mixtures thereof. 17. A cleaning composition according to claim 6, wherein said hydrotrope is selected from the group consisting of sodium xylene sulphonate, phosphate esters, sodium toluene sulphonate, and mixtures thereof. 18. A cleaning composition according to claim 1 , wherein said alkali metal silicates include Na 2 O and have an Na 2 O:SiO 2 ratio of from 2:1 to 1 :2. 19. A cleaning composition according to claim 1 , wherein the diluent is water. 20. A method of cleaning a surface bearing bumt-on food soils comprising the steps of a. applying the composition of claim 1 to the food soils at a cool surface temperature; b. allowing the food soils to soften; and c. removing the food soils. 21. The method of claim 20 wherein the cool surface temperature is a temperature not in excess of about 50°C.

Inventors: CALLAGHAN IAN C, PALMER SANDRA A, CALLAGHAN, IAN, C., PALMER, SANDRA, A.
Applicants: CALLAGHAN IAN C, JOHNSON & SON INC S C, PALMER SANDRA A, CALLAGHAN, IAN, C., PALMER, SANDRA, A., S.C. JOHNSON & SON, INC.
Application year: 1995
Main classification: C11D3
IPC codes: C11D3