GB2247025A - Enzymatic dishwashing and rinsing composition - Google Patents

Abstract

An enzymatic dishwashing or rinsing composition comprises phospholipase A1 and/or A2. In combination with proteolytic enzymes the composition is effective in removing egg yolk soil and consequently reducing spotting on glassware.

Description

ENZYMATIC DISHWASHING AND RINSING COMPOSITION FIELD OF INVENTION The present invention relates to an enzymatic dishwashing or rinsing composition comprising lipolytic enzymes.

BACKGROUND OF INVENTION Enzymatic dishwashing compositions have been proposed in the art. As enzymes, mainly amylases and/or proteases have been proposed for inclusion in dishwashing compositions (e.g. US 4 162 987, Maguire et al). Lipases have also been suggested (e.g. EP 271 155, Unilever), but have received far less attention than the amylases and/or proteases. Dishwashing compositions, in particular machine dishwashing compositions which are used in the main wash step of a machine dishwashing operation have, in general, a satisfactory cleaning performance. However, frequently the articles cleaned with such products still do not have a satisfactory visual appearance after rinsing and drying, showing film or spots.Some main wash liquor is usually carried over from the main wash step to the rinse step, causing some deposition of soil and resulting in insoluble calcium salts on the articles to be rinsed.

This results in visible film or spots on the articles when they are dry. In particular with glass articles, this causes an unsightly visual appearance, and most particularly when egg soil is present in the wash.

SUMMARY OF INVENTION We have now found that the addition of phospholipase A and/or A2 to a main wash dishwashing composition or to a rinse composition significantly improves the cleaning of certain soils and reduces the formation of film or spots on the articles cleaned or rinsed with such a composition.

DESCRIPTION OF INVENTION Phospholipids occurs generally in animal and vegetable foods. They are important constituents of all cell membranes. For example, in egg yolk the phospholipid level is 18% of the total dry weight. Phospholipids are of the general formula (I):

wherein X represents hydrogen, choline (to give lecithin), ethanolamine or serine, for example, and R1 and R2 are alkyl groups which may be the same or different.

Tests have shown that if glasses are washed in the presence of the phospholipid lecithin, there is a significantly greater degree of spot formation in comparison to other fats, proteins, etc. Although we do not wish to be bound by any theory, it is possible that the phospholipid adsorbs onto glass surfaces, thereby modifying the drainage behaviour of water films.

Furthermore, phospholipids may influence the removal of composite soils, such as egg yolk, because of their tendency to form complexes with proteins (usually phosphoglycoproteins, eg livetin in egg yolk) and more apolar lipids such as triglycerides.

Four classes of phospolipases (classified as Al, A2, C and D) are known (E Dennis, The Phospholipases, Chapter 9, The Enzymes, Vol XVI, Academic Press, 1983). The enzymes all use phospholipids as a substrate, but catalyse the hydrolysis of different ester moieties in the substrate molecule. Phospholipase-Al, and -A2 yield lysophospholipids which can in turn be further hydrolysed by lysophospholipases.

The most common class of phospholipase is Phospholipase-A2, commercially available as Lecitase (ex Novo Industri) and isolated from porcine pancreas glands.

Lecitase has an activity of 10,000 IU/ml, wherein 1 IU is defined as the amount of enzyme producing 1 microequivalent of free fatty acid per minute on an egg yolk emulsion substrate at 6mM calcium over 5-10 minutes at 400C, pH 8.0 (G de Haas et al, Biochim Biophys Acta 159, 105 (1968)). Molecular weight is approximately 14,000 and the enzyme has a high stability by virtue of its disulphide bridges.

Lecitase hydrolyses glycerophospholipids to yield a fatty acid and lysoglycerophospholipid.

Both of the reaction products are surface active and, accordingly, will assist in the removal of egg yolk and the prevention of spot formation. Thus, soil breakdown products themselves act in the removal of soils.

However, it has been found that the above described phospholipases require free calcium ions for enzyme activity at a sufficient level to break down phospholipids. In conventional machine dishwashing compositions the level of free Ca ions is generally very low because the compositions are usually built (pCa > 4-5).

Accordingly, such a class of phospholipase is generally thought impractical for machine compositions.

However, it has been found that PLA-2 may yield significant appearance benefits in dishwashing, when lecithin containing soils are present. In order to be of use in a built dishwashing system when egg yolk is present, it has been found that it is necessary to utilise a combination of PLA-2 and protease.

The phospholipase used in the system according to the invention may be as described above. It is preferred to use from 5-200 U/g of final detergent composition. This will be roughly 2000-1500 U/standard wash.

The protease can be the subtilisin variety sold as Savinase (TM of Novo-Nordisk A/S) or Maxacal (TM of Gist Brocades/IBIS) or as Opticlean (ex MKC) or AP122 (ex Showa Denko), which has pI approximately 10. Other useful examples of protease include Maxatase, Esperase, Alcalase (Trade Marks), proteinase K and subtilisin BPN'.

Protease can for example be used in an amount ranging from about the order of 0.0002 to about the order of 0.05 Anson units per gram of the detergent composition.

Expressed in other units, the protease can also be included in the compositions in amounts of the order of from about 0.1 to 100 GU/mg detergent formulation.

Preferably, the amount ranges from 1 to 50 and particularly preferably from 5 to 20 GU/mg, although the upper level of protease is not critical to the invention.

A GU is a Glycine Unit, defined as the proteolytic enzyme activity which, under standard conditions, during a 15-minute-incubation at 40 deg C, with N-acetyl casein as substrate, produces an amount of NH2-group equivalent to 1 micromole of glycine.

The enzymes may be added in the form of a granular preparation or a slurry. The compositions may contain either crude or purified enzyme.

The composition of the invention may furthermore comprise the usual ingredients of dishwashing compositions, i.e. it may contain one or more alkali salts commonly used in dishwashing compositions. Thus, it may contain organic and/or inorganic builders such as the alkali metal ortho-, pyro- and tripolyphosphates and hexametaphosphates, zeolites, silicates, carbonates, borates, citrates, carboxymethyloxysuccinates, nitrilotriacetates, polymeric polyelectrolytes such as polyacrylates, polymaleates, and other known organic and inorganic builder compounds, together with combinations thereof.

Usually, the amount of builders in the composition varies from 10-90% by weight, generally from 20-70% by weight.

The composition may also contain a detergent-active compound. If a detergent-active compound is included, it is usually in an amount of from 0.5-10%, usually 1-5%.

Any well-known type of detergent-active compound may be used, such as soaps, synthetic anionic, nonionic, or amphoteric detergent surfactants and mixtures thereof.

Preferably, a nonionic detergent surfactant is used, especially a low-foaming one. Suitable examples of such nonionic detergent surfactants can easily be found in M Schick, "Nonionic Surfactants" (1967).

The composition may furthermore contain other useful additives such as bleaching agents, bleaching agent activators, hydrotropes, fillers, perfumes, colouring agents, germicides, soil-suspending agents, drainage-promoting agents, threshold agents, aminopolyphosphonic acids and alkali metal or alkaline earth metal salts thereof, clays such as hectorites, anti-corrosion agents such as fatty acids and benztriazole. Other enzymes such as amylases and lipases may also be included.

As bleaching agents the peroxygen type bleaching agents, preferably with a bleach precursor such as TAED are suitable for inclusion in the machine dishwashing compositions. Chlorine based agents may not be used unless suitably separated from the enzymes by, eg encapsulation.

The composition of the present invention may be formulated as a powder, as a pourable aqueous or non-aqueous liquid or gel, as a tablet or cake, or in any other conventional form.

A typical example of a conventional powder machine dishwashing composition usually contains a phosphate or non-phosphate builder in an amount of from 20-60% by weight an alkali metal silicate in an amount of from 40-80% by weight or an alkali metal disilicate in an amount of from 5-308 by weight, a peroxy type bleaching agent in an amount of from 1-15% by weight, a low-foaming nonionic detergent surfactant in an amount of from 0.5-5% by weight, and minor ingredients such as perfumes, colouring agents, hydrotropes, fillers, etc.

A typical example of a conventional liquid machine dishwashing composition usually contains a phosphate or non-phosphate builder in an amount of from 1-30 wtt, a bleach in an amount equivalent to from 0.5 to 5 wtt available chlorine and a thixotropic thickener in an amount of from 0.5 to 5 wtt, the balance being water.

Minor ingredients as above may also be present.

Final rinse products may be produced containing phospholipase. Rinse aids are described in, eg, EP 0 070 587 and EP 0 197 434.

The invention will be further described with reference to the following non-limiting Examples.

Example 1 In a test system, a 50:50 mix of a base composition of disilicate and citrate was used in a commercial dishwashing machine.

Detergent composition dose : 30 g Water hardness : 16 OFH Main wash temperature : 65 OC 'Test soil : 0.15 g lecithin The glasses were appraised by counting the average number of spots.

PLA-2 (ml at 11,000 U/ml) Number Spots > 60 0.025 30 0.05 30 0.1 10 0.3 10 0.5 10 It is seen that addition of PLA-2 causes a significant reduction in the number of spots caused by lecithin-based soil.

Example 2 When egg yolk is present, the combination of protease and PLA-2 is essential. In a machine experiment, using a base composition of a 50:50 mixture of disilicate and citrate the following results were obtained: Number Protease PLA-2 of Spots 80-100 0.2g Esp - 80-100 0.2g Esp 1100 U 60 (37 U/g) 0.2g Esp 2200 U < 10 0.2g Esp 4400 U < 10

Claims (2)

1. Claims 1. An enzymatic dishwashing composition comprising from 10-80% by weight of a builder, characterised in that it further contains from 5-50 IU/g of composition of phospolipase A1 and/or A2.
2. 2. A composition as claimed in claim 1 which further contains 1-50 GU/mg of composition of protease.