Liquid natamycin composition, process for preparing same, use thereof and protected products

Field of the invention

The present invention relates to a liquid natamycin composition for protecting perishable goods such as food and feed products, including pet foods and beverages, against the growth of fungi. The composition may be used also on agricultural products such as vegetables, fruits and flower bulbs. The composition of the present invention is physically stable over prolonged periods and it is preferably also microbially stable. The present invention also relates to a process for preparing the physically stable liquid natamycin composition according to the invention and to methods of using the composition for controlling the growth of fungi on perishable goods, such as food and feed products. Finally, the invention also relates to products treated with the liquid composition. A preferred treated product comprises a bakery product.

Background of the invention

Natamycin is a polyene macrolide natural anti-fungal agent produced by fermentation of the bacterium Streptomyces natalensis. Natamycin (previously known as pimaricin) has an extremely effective and selective mode of action against a very broad spectrum of common food spoilage yeasts and moulds with most strains being inhibited by concentrations of 1-15 ppm of natamycin.

Natamycin has been used for many years in many countries throughout the world as an authorized preservation treatment, principally for surface treatment of cheeses and certain meat products such as dried sausages. Despite this long-term use, the development of resistant strains has not been reported to date unlike the chemical organic acid sorbate and propionate preservatives for which a number of resistant yeasts and moulds have been detected and reported. Some species of Penicittium mould are even able to degrade and metabolise sorbate.

Natamycin is typically applied in the form of an aqueous suspension although natamycin is sparingly soluble in water with its maximum solubility being around 40 ppm. In practice this means that when an aqueous natamycin liquid is applied to the surface of a cheese or sausage, the natamycin will mainly be present in the form of crystals on the surface of the treated

product. The dissolved fraction of natamycin in aqueous liquids shows very limited diffusion into the food. Natamycin is active over a wide pH range and unlike many organic acid preservatives it is not dependent on a low pH acidic environment to show good anti-fungal activity.

Natamycin has not been reported to have any adverse quality or flavour impact on food products. Natamycin is most soluble at high or low pH but is most stable at neutral pH (Stark, J., and Tan, H. S. 2003. 'Natamycin'. In: Food Preservatives, Second Edition. Eds: N. J. Russell and G. W. Gould. Kluwer Academic/Plenum Publishers.)

A general description of natamycin and its current uses may be found in the above review and in Thomas, L. V. and Delves-Broughton, J. 2003. Natamycin. in: Encyclopedia of Food Sciences and Nutrition. Eds. B. Caballero, L. Trugo and P. Finglas, pp 4109-4115. Elsevier Science Ltd.

In the food industry natamycin is generally used as a suspension in an aqueous solution for the surface treatment of food (i.e. in spraying, dipping or brushing) or dosed as a powder directly into food. The natamycin powder, although mixed with excipients such as lactose, is difficult to handle due to its stickiness. Furthermore it causes problems by the dust it generates and it can also adhere to weighing equipment used in the preparation of the treatment liquid. Natamycin is a very attractive antifungal agent for many purposes in the food and feed industry as well as for agricultural products. However, the physical handling and dosing of natamycin powder is not altogether uncomplicated particularly because of the potency of natamycin at very low concentrations.

Because natamycin is sparingly soluble in aqueous liquids, the undissolved crystals tend to settle at the bottom of treatment or storage vessels. This physical instability of the suspensions requires a frequent mixing of the suspension and/or recirculation of the treatment liquid. Natamycin is highly effective against fungi but its suspensions are vulnerable to the attack of bacteria. In order to prevent bacterial growth, salt is typically added to the liquids. However, the salt is prone to crystallize, thus clogging the nozzles of spraying equipment. The problems relating to the physical instability and bacterial vulnerability of aqueous natamycin liquids has

made it difficult to provide ready-to-use liquid suspensions and concentrates of natamycin for the industry to use.

EP-Bl-O 678 241 (US-A-5,552,151, DSM N.V.) discloses a concentrated aqueous suspension of natamycin, which exhibits chemical, physical and microbial stability. The physical stability relates to a stability calculated in hours. It is provided by a gum based or cellulosic thickening agent which increases the viscosity of the suspension to at least 500 mPa. The aqueous suspension may also include a deflocculating or suspending agent. Although the document mentions the possibility of additionally using glycol or glycerol as suspending agents, there are no examples of such use. The aqueous suspension has a pH lower than 6 to provide microbial stability of at least 14 days.

US 5,962,510 (Gist-Brocades B.V.) discloses an antifungal aqueous composition comprising natamycin, a suitable thickener and optionally salt. The thickener is preferably xanthan gum or gellan gum and it improves the adhesion of the natamycin to the surface of the treated products. The thickener also reduces the sedimentation tendency of a dipping bath for cheese and sausages. Although the document mentions the possibility to use polyethylene glycol or glycerol as suspending agents in the aqueous suspension, there are no examples of such use.

WO-A1-03/101213 (DSM IP Assets B.V.) discloses an aqueous natamycin composition for treating shredded cheese by spraying. The composition contains a thickener such as xanthan gum for preventing the clogging of the nozzles of the spraying equipment.

WO-Al -2004/082407 (DSM IP Asset B.V.) discloses an aqueous solution of natamycin which is chemically stable despite an increased solubility in the aqueous liquid. The liquid comprises a solubilizer which is preferably a surfactant and which increases the amount of dissolved natamycin to at least 100 ppm. The liquid may contain conventional chelating agents and/or antioxidants.

WO-Al -2004/105491 (DSM IP Assets B.V.) discloses a chemically stable ready-to-use aqueous solution of natamycin which contains a water-miscible solvent and natamycin dissolved in the water and solvent The preferred water-miscible solvent is ethanol, but also other lower alcohols such as methanol, propanol, ethylene glycol propylene glycol and glycerol

are mentioned. The natamycin is initially dissolved in a water/solvent mixture containing 10 to 90% solvent and having a high or low pH. The resulting concentrate is then quickly diluted with an aqueous buffer solution to adjust the pH to 5-8 for avoiding chemical degradation of the natamycin. The amount of the solvent is 0.1% to 10% in the final aqueous solution. The examples show an amount of 0.2 or 0.4% ethanol in the ready-to-use aqueous solution.

GB-A-I 470 005 (Gist-Brocades N. V.) discloses a non-aqueous alcohol/acid mixture for treating agricultural products, especially citrus fruits. The natamycin is preferably dissolved in a mixture of ethanol and acetic acid. However, some other lower alcohols and acids are also shown to be useful. The specification suggests also that alkanols with 2 or 3 carbon atoms and up to one hydroxy per carbon atom can be used, but there are no examples of any solutions with alkanols having more than one hydroxy group. The combination of alcohol and acid provides the benefit of increasing the solubility of the natamycin so that it can penetrate the peel of the citrus fruit to such an extent that mould growth is effectively prevented. The solution may also contain water and it is applied on the agricultural products by submersion, brushing or spraying.

WO-Al -2005/018322 (Danisco AJS) discloses an antimicrobial material such as natamycin in an encapsulated form. The encapsulation keeps the natamycin from contact with food ingredients and/or environments which might harm the natamycin. Alternatively, food ingredients such as yeast are protected from contact which natamycin during the production of the food.

WO-Al -2005/074690 (Danisco A/S) discloses a fine bakery product with increased shelf life. The baked product has natamycin sprayed on its outer surface to prevent mould growth in a package stored for 2 weeks or more. The natamycin is preferably sprayed in the form of an aqueous suspension with or without a thickener.

Documents cited in this text ("herein cited documents"), as well as each document or reference cited in each of the herein-cited documents, and all regulations, manufacturer's literature, specifications, instructions, product data sheets, material data sheet, and the like, as to each product mentioned in this text, are hereby expressly incorporated herein by reference.

Despite recent improvements in the use of natamycin in the food and feed industry, there still exists a need for improved physical and microbial stability in the natamycin liquids. There is especially a need for a physically stable ready-to-use liquid or concentrate which can be stored and used without a need for agitation. The liquid naturally also needs to contain a high enough amount of natamycin for the intended preservation purposes.

The present invention seeks to overcome the problems of the prior art, as described above, by providing a liquid composition of natamycin in an organic solvent. Contrary to the prior art, the composition is not an aqueous liquid. The present inventors have found that lower polyhydric alcohols and especially glycerol have unique properties, which make them eminently suitable for providing a stable natamycin composition. The organic solvent and the absence of large amounts of water help to make the natamycin composition stable against bacterial degradation.

Brief summary of the invention

The present invention thus relates to a liquid composition for controlling the growth of fungi, said composition comprising an antifungally effective amount of natamycin in an alcoholic solvent, wherein said solvent contains a physically stabilizing amount of polyhydric alcohol(s) and is selected from polyhydric alcohols, mixtures of polyhydric alcohols, and mixtures of polyhydric and monohydric alcohols, said composition comprising a physically stable solution, sol or suspension of natamycin in said solvent.

The invention also relates to a process for preparing the physically stable liquid natamycin composition. The process comprises combining an antifungally effective mount of natamycin with a physically stabilizing amount of polyhydric alcohol(s) in an alcoholic solvent selected from polyhydric alcohols, mixtures of polyhydric alcohols and mixtures of polyhydric and monohydric alcohols, and mixing the resulting natamycin-solvent mixture to provide a physically stable solution, sol or suspension of natamycin in said solvent.

The invention further relates to the use of the liquid natamycin composition for controlling the growth of fungi. The use comprises applying an antifungally effective amount of natamycin to perishable product(s) said natamycin being provided by way of a liquid composition comprising natamycin in said alcoholic solvent, wherein said solvent contains a physically

stabilizing amount of polyhydric alcohol(s) and is selected from polyhydric alcohols, mixtures of polyhydric alcohols and mixtures of polyhydric and monohydric alcohols. The composition is a physically stable solution, sol or suspension of natamycin in said solvent.

The invention also relates to products treated with the composition according to the invention. Said products comprise antifungally preserved products, which are food or feed products or agricultural products having natamycin and polyhydric alcohol spread over the surface thereof, said natamycin being provided in an antifungally effective amount for preserving said product against the growth of fungi.

The polyhydric alcohol used as physically stabilizing solvent in the composition according to the invention contains 2 or 3 carbon atoms and is selected from glycerol, propylene glycol and glycol. Glycerol is the preferred polyhydric alcohol. The monohydric alcohol in the alcoholic solvent also contains 2 or 3 carbon atoms and is selected from ethanol and propanol. Ethanol is the preferred monohydric alcohol. The alcoholic solvent of the liquid composition preferably consists essentially only of said alcohol(s) and the innate water included in said alcohol(s).

The preferred composition of the invention is either a ready-to-use liquid or it comprises a concentrate from which the actual treatment liquid is made. The physically and microbially stable ready-to-use liquid reduces the need for equipment needed for the application of the natamycin as no dilution equipment, no balance tanks and no mixing is needed.

Detailed description of the invention

It has been discovered that dissolving or suspending the sparingly soluble natamycin in a polyhydric alcohol provides a stable solution, sol or suspension in which the natamycin does not settle or sediment. The physical stability of such a natamycin composition greatly improves the use of natamycin in the food and feed industry as well as in other applications, such as the agricultural industry.

As utilized herein, the term "alcohol" means an organic compound having at least one hydroxy group. A "monohydric alcohol" has only one hydroxy group, while a "polyhydric alcohol" has at least two hydroxy groups. The preferred alcohols of the present invention are lower alcohols

having 2 or 3 carbon atoms. It is noted that the monohydric alcohol methanol would be technically suitable for use in the invention but it is usually excluded because of its poisonous character.

As used herein, the term "solvent" means a liquid in which natamycin and optionally one or more other ingredients is dissolved or suspended. The solvent of the invention is an "alcoholic solvent" by which is meant that it is based on an alcohol and consists to more than 50 % of one or more alcohols. Preferably, the solvent consists essentially of alcohol(s). The alcoholic solvent is "non-aqueous" in that it is not based on water even though it may contain small amounts of water added e.g. in connection with a solvent or an additive ingredient. The liquid composition is considered non-aqueous as long as it contains less than 10% water. The composition may be diluted with water to contain more than 10% water, in which case it becomes an aqueous liquid. The composition may contain other additives with various functions such as described below. Such additives are not considered to form a part of the alcoholic solvent.

As used herein, the term "solution" means a liquid in which a solid compound such as natamycin is truly dissolved. The term "sol" means a liquid in which a solid such as natamycin is homogeneously distributed in such small particles that there is no settling or only very little settling of the solid during storage of more than two weeks. The term "suspension" means a liquid in which solid particles are distributed but wherein they may with time settle. The liquid composition of the present invention can be a solution, a sol, a suspension or a mixture of these.

As used herein, the term "physical stability" or "physically stable" refers to a liquid natamycin composition wherein the natamycin is included in such a form that any tendency to settle out is so small that the liquid retains a uniform distribution of the natamycin during the practical daily use of the liquid. A physical stability of four days means, for instance, that even though the liquid is not agitated, shaken or mixed for four days it remains uniform enough for practical purposes. A "physically stabilizing amount" of polyhydric alcohol is an amount which is sufficient to keep the solution, suspension or sol uniform for the practical use of the liquid without the conventional mixing, agitation or recycling. The amount differs from one polyhydric alcohol to another and is also different depending on the other alcohols included

and on the content of water and other components in the composition. The stabilizing amount of polyhydric alcohol is preferably one which keeps the composition physically stable for at least 2 weeks.

As used herein the term "food and feed products" means products, which are meant to be ingested by man or beast. The term food specifically includes also pet foods and beverages. The food and feed products of the invention are solid, semi-solid or liquid products, although the preferred products are solid.

As used herein, the term "agricultural products" means fruits, vegetables, crops, flower bulbs and other agricultural products, which are susceptible to attack by fungi. The food and feed products as well as the agricultural products are also referred to as "perishable products".

The preferred polyhydric alcohol according to the invention is glycerol. Propylene glycol has also proven very useful. The solvent preferably contains at least 50%, preferably at least 70% polyhydric alcohol. Most preferably, the solvent contains at least 80% polyhydric alcohol. The solvent may contain 90% or even 100% polyhydric alcohol. It is preferred to use glycerol in an amount of at least 30% and preferably at least 45 % of the solvent. It should be noted that very good results have been obtained with the use of glycerol as the only alcohol of the solvent.

The preferred monohydric alcohol in the solvent is ethanol. If propanol is used, the propanol may be n-propanol or i-propanol. The preferred propanol is i-propanol. The preferred solvent of the invention is a mixture of glycerol and a second alcohol selected from propylene glycol and ethanol. Mixtures of glycerol, propylene glycol and ethanol are also very good solvents.

The alcoholic solvent may contain minor amounts of other solvent components in addition to the alcoholic solvents. However, it is preferred that the solvent consists essentially of said alcohols. It should be noted that ethanol, for instance, usually contains minor amounts of water (about 5% to 0.5%) and also glycerol contains some innate water (about 0.2%). This small amount of water need not be removed before use in the composition and the low water content is not considered to make the liquid composition an aqueous one.

The natamycin is dissolved or suspended in the solvent. Even when the natamycin is not completely dissolved, the solvent is capable of keeping the natamycin uniformly distributed in the liquid. Natamycin can also form a sol in the polyhydric alcohol or mixture of alcohols. In the sol the natamycin particles are so small that no sedimentation takes place even during weeks of storage.

Thus, the invention provides a physically stable liquid form of natamycin with no precipitation or settling of the natamycin for a prolonged period of time. This gives the advantage of ease of handling with no need for stirring, agitating, shaking or recirculation of the liquid before or during use.

The composition of the invention is useful as such for application to perishable goods. The composition may be incorporated into the goods or applied by dipping, spraying or brushing onto the goods.

Special benefits are obtained in the spraying of the natamycin composition onto food and feed products. There has been observed no blocking of the nozzles of the spraying equipment. In cases when the solvent includes monohydric alcohols such as ethanol, this alcohol will evaporate from the surface of the food or in the spray and only the polyhydric alcohol part of the solvent will remain on the food. Polyhydric alcohols are well accepted in the food and feed industry. For instance, spraying of glycerol on food generally poses no regulatory problems. By combining a fairly thick polyhydric alcohol such as glycerol with a free flowing alcohol such as ethanol, the viscosity of the composition may be adjusted to suit the spray equipment.

In the preferred composition according to the invention the solvent comprises a mixture of glycerol and ethanol, wherein the ratio of glycerol to ethanol is from 95:5 to 70:30, preferably from 90:10 to 80:20 calculated by weight. Addition of ethanol to the glycerol improves the solubility of natamycin in the solvent and reduces the viscosity of the composition. It is preferred that at least 30%, preferably at least 45% by weight of the solvent comprises glycerol. The amount of ethanol should not exceed 30% by weight of the liquid composition. Preferably, the ethanol amount is between 10 and 20% by weight.

The composition of the present invention differs from the traditional aqueous liquids used on food and feed products in that it is non-aqueous. The preferred non-aqueous composition comprises less than 10% water, preferably less than 5% water, most preferably less than 2% water. When water- free solvents are used, the liquid composition is essentially free of water.

The water content of the liquid composition of the invention is preferably very low. Natamycin is sparingly soluble in water and adding e.g. 20% water to a concentrate of natamycin in glycerol makes the natamycin drop out. In other words, the water destroys the physical stability provided by the polyhydric alcohol. Smaller amounts of water are acceptable and the composition remains stable even though 10% water is added to it. As mentioned above, the innate water provided e.g. by the use of ethanol having 5% water is not harmful to the stability.

The low water content provides a low water activity to the composition and hence most bacteria are unable to grow in the liquid. This makes the composition microbially stable even when stored at ambient temperature. The alcohols of the solvent do not support the growth of bacteria on their own, which adds to the microbial stability. The long shelf life of the composition provides great advantages over the traditional physically and microbially unstable aqueous natamycin preparations. Because of the microbial stability, the composition can be made without salt, which reduces corrosion and clogging of spray nozzles.

When natamycin is added to food and feed products without water or with only minor amounts of water, this removes concerns connected with additional moisture in the production environment and on the food or feed surface.

The liquid composition contains an antifungally effective amount of natamycin. The amount of natamycin included depends on the intended use of the liquid composition. However, the composition typically includes 100 to 50,000 ppm natamycin. If less than 100 ppm natamycin is included, the amount of liquid applied to the goods will have to be larger than normally desired. It is preferred that when the composition is to be used as a ready-to-use non-aqueous microbially stable natamycin liquid, the natamycin is present in an amount of 100 to 10,000 ppm.

The alcoholic solvent of the present invention is capable of forming a homogeneous liquid with water and with many other solvents. The composition is therefore suitable as a concentrate to be diluted before use. Thus, if the composition is a non-aqueous liquid concentrate, the natamycin should be present in an amount of 400 to 50,000 ppm to allow for a dilution with 4 to 5 times the amount of water or solvent.

The amount of natamycin typically needed for providing an antifungally effective ready-to-use composition is soluble in a mixture of glycerol and ethanol and it forms a true solution in the solvent. Hence the natamycin will not separate out on standing. Natamycin is also soluble in a mixture of glycerol and propylene glycol. In glycerol natamycin forms a suspension or sol, which is also physically stable.

The liquid composition of the invention is adapted for being applied to perishable products as such or after dilution with water or another physiologically acceptable (food grade) liquid. The composition is preferably applied onto the surface of an edible food or feed product. The application of the composition on the products may be performed by dipping, brushing or spraying. In an alternative embodiment of the present invention the liquid is adapted for being added directly into a liquid or semi-liquid food product such as various beverages or drinks.

The food or feed product which is typically preserved by the natamycin composition of the present invention can be selected from cheese, shredded cheese, processed cheese, cream cheese, sour cream, dried fermented meat product including salamis and other sausages, wine, beer, yoghurt, juice and other beverages, salad dressing, dips, bakery products and bakery fillings, surface glazes and icing, pizza toppings, confectionery and confectionery fillings, olives, olive brine, olive oil, cottage cheese, cottage cheese dressing, tomato purees and paste, condiments, and fruit pulp and the like food products, as well as feed products, such as pet food, broiler feed fruits, crops, bulbs etc. The most preferred use of the present natamycin composition is in spraying on baked or unbaked bakery products. The bakery product most preferably comprises baked bread, hot plate goods or fine bakery products. The amount of natamycin to be sprayed on a bakery product is preferably from 1 to 10 μg/cm ² of its surface.

The liquid natamycin composition according to the invention may comprise other active agents besides natamycin. Such additive ingredients may have an effect on the liquid composition as

such or on a diluted form thereof. The additive may also be desirable in and/or on the product to be treated with the composition. The additive may also be an active agent for the natamycin itself or for another additive ingredient. Since the composition of the present invention is nonaqueous it is advantageous to include in the liquid such additives, which are not soluble in water but are soluble in the alcoholic solvent. Other additives are soluble in both the alcoholic solvent and in water. Some are soluble only in water and play their role after dilution with water has been completed. The additive may be included in the ready-to-use liquid composition or in the concentrate or it may be added via a diluent for the concentrate.

Such additives include, but are not limited to preservatives, stabilizers, thickeners, antioxidants, chelating agents, buffers, acids, salts, carriers, excipients, diluents, surfactants, emulsifiers, flavonoids, vitamins, essential oils, flavours, pigments and mixtures thereof. The additives should not be used in amounts, which impair the physical stability of the composition.

In certain embodiments of the present invention, the active agent is a preservative. Typical preservatives are selected from benzoic acid and benzoates, sorbic acid and sorbates, lactic acid and lactates, propionic acid and propionates, acetic acid and acetates, methyl paraben, propyl paraben, sulfur dioxde and mixtures thereof. The preservative may thus be an organic acid or its salt. However, it should be noted that the chemical degradation of natamycin increases at low and high pH. Organic acids may reduce the chemical activity of the composition with time. Salts of organic acids should thus preferably be selected and it is preferred that the preservative is not an organic acid.

An organic acid should not either be included in the composition in such a manner that the organic acid in combination with the alcohol in the solvent makes the natamycin penetrate the peel or wall of agricultural products such as citrus fruit (as described in GB -A-I 470 005). When the composition of the invention is applied to the outer surface of food products, the composition should rather maintain the natamycin on the surface or as close to the surface as possible, because that is where the attacking moulds and yeasts will be. Food products, which have undergone a heating process will be substantially free of moulds and yeast underneath their outer crust or wall and any natamycin migrating into the product will be lost for its protective purpose. This is especially true for products with a fairly easily penetrable wall or crust, such as a bakery product.

Polyhydric alcohols, and especially glycerol have a viscosity, which is eminently suitable for keeping the composition on the surface of the product. Where the use of an organic acid would increase the risk of penetration and migration of the composition into the product, organic acids should be excluded and, if preservation is needed, preservatives other than organic acids should be selected.

In another embodiment of the invention, the active agent(s) is/are selected from phenolic and alkyl compounds, flavonoids and mixtures thereof. The active agent may also be selected from plant extracts or essential oils, such as obtainable from cinnamon, vanilla, citrus, geranium species, mint, cloves, thyme, garlic, onion, horseradish, mustard, cole, cabbage, spinach, radish, oreganum, sage, grapes and other red fruits, coffee, tea, rosemary, and mixtures thereof. Other alcohol soluble additives are selected from vegetables oils containing vitamin A, vitamin E, vitamin B3 (nicotinamide) and/or tocopherol. Many of these compounds have an antibiotic, antibacterial or antimycotic activity and have a preservative effect on the natamycin composition as well as on the treated product itself.

Another kind of additives is exemplified by anti-oxidants such as butyl hydroxy anisole, butyl hydroxy toluene, tert butyl hydroxy quinine, propyl gallate and mixtures thereof.

The composition or its diluent may also contain chelating agents such as EDTA, citric acid, tartaric acid, etc. Moreover, the composition or its diluent may contain active agents selected from fatty acids esters such as mono-and diglycerides, non-ionic surfactants such as polysorbates, phospholipids, etc. Emulsifiers may enhance the stability of the composition, especially after dilution.

In a specially preferred embodiment, the composition comprises a concentrate and the concentrate or the diluent therefor contains active agent(s), which have the function of stabilizer, thickener and/or solubilizer after dilution of the concentrate. Such stabilizers, thickeners and solubilizers are known in the art and they include but are not limited to gums and other hydrocolloids, such as xanthan gum, guar gum, etc.

The natamycin dissolved or suspended in the alcoholic solvent of the present invention has a surprisingly good physical stability. It retains its physical stability for 2 weeks or more without

the addition of further stabilizers. Test samples have shown no drop out of natamycin even after a storage of 10 weeks at ambient temperature.

The liquid natamycin composition of the present invention is easy to prepare. The desired amount of natamycin is weighed and added to the alcoholic solvent. If the alcoholic solvent is a mixture of alcohols, the mixed solvent is typically prepared beforehand by simply mixing the alcohols together. In case the composition is to be applied to edible products, the ingredients need all be food grade ingredients. The natamycin is typically used in one of its commercial forms, such as Natamax® (from Danisco), Delvocid® (from DSM), etc. The natamycin may contain additives and excipients such as salt and lactose, in which case these will be included in the composition.

It is preferred that the only water which is added into the composition is the innate water of the components of the composition. In case other active agents besides natamycin are to be included in the composition, these may be added to the composition before or after the natamycin or with the natamycin. Thus, they may be added to the solvent, to the natamycin, to the composition or to a diluent therefor. They may be first dissolved in a solvent alcohol such as in ethanol or, if water soluble, they may be dissolved in a small amount of water. They may also be suspended as fine particles in the composition. However, care should be taken not to add active agents which destroy the stability of the composition.

The viscosity of the liquid composition can be adjusted by selecting the alcohol and/or by adding thickeners. When the composition consists essentially only of natamycin in an alcoholic solvent, the viscosity can be adjusted to a value between 0.0001 Pas and 10 Pas. The viscosity when glycerol alone is used as the solvent is 5 to 10 Pas. Adding ethanol reduces the viscosity, which thus can be lowered down to 0.0001 Pas if desired. The liquid composition as such is thus suitable for spraying on products.

It was not possible in the prior art to have a natamycin liquid with such a low viscosity and good physical and microbial stability. This combination provides an advantage especially for spraying applications.

When the liquid natamycin composition according to the invention is used for controlling the growth of fungi, an antifungally effective amount of natamycin is applied to perishable product(s) together with the alcoholic solvent. The liquid composition may be used as such or it may comprise a concentrate to be diluted with a diluent selected from water and an alcoholic diluent comprising glycerol, propylene glycol, glycol, ethanol, propanol or mixtures thereof prior to being applied to said product(s). Also other diluents are possible, provided they are acceptable form the point of view of stability and physiological acceptability.

When the composition of the invention is prepared in the form of a concentrate, it is typically diluted with water prior to use. This reduces the need for storing and shipping of huge amounts of water. Diluting with water is also easy at the point of end use. Typically the concentrate is diluted with no more than 4 times the amount of water. If another diluent is used, especially if an alcoholic solvent is used for dilution, the concentrate is typically diluted with no more than 5 times the amount of said alcoholic diluent.

The physical stability of the composition is reduced when it is diluted with water. A dilution with about 20% water makes the natamycin drop out too quickly for most practical use, while a dilution with water in ratios of water to concentrate between 2:1 and 4:1 maintains the liquid physically stable for 0.5 to 2 hours even without a stabilizer.

Since, dilution with water makes the natamycin drop out of the solution in a matter of hours it is recommended to add stabilizers and/or thickeners as described above for water-based applications. Thus, when the composition is diluted with water, the diluted composition preferably contains a compound selected from a stabilizer, an emulsifier, an antioxidant, a chelating agent, a thickener, a surfactant, a preservative and combinations thereof. The compound(s) should preferably be selected from compounds capable of maintaining the diluted composition physically and/or microbially stable for at least 4 days.

The concentrate is preferably made of natamycin in a mixture of glycerol and ethanol. The above mentioned additives may be included in the concentrate or in the diluent. In another embodiment, the concentrate is diluted with water immediately before application, e.g. by injecting water into the concentrate flowing to or in the spray equipment. In such a case no stabilizers or preservatives are needed.

The liquid natamycin composition is applied to the products to be treated in a manner well known in the art. Such application procedures include spraying, dipping or brushing. Spraying is the preferred way of application since the viscosity of the liquid is especially suited for such use. The spraying may be performed with the concentrated liquid as such or the composition may be sprayed after dilution with water or another diluent.

The preferred products to be sprayed are baked or unbaked bakery product. Special benefits are obtained in the spraying of baked bread, hot plate goods or fine bakery. Bread products include different kinds of bread which are typically packaged in moisture proof casings and are expected to have a shelf life of 5 days or more. A preferred kind of bread is sliced loaves packed in plastic bags. Hot plate goods include crumpets and pancakes and fine bakery includes all kinds of cakes and pastry, including buns, waffles, tortillas, pizzas, etc. The viscosity of the liquid enables the production of a very fine spray and the natamycin is evenly distributed over the whole product surface. The monohydric alcohol such as ethanol will evaporate during spraying and after having landed on the product. Thus, the product contains only the natamycin (and other active agents) and the polyhydric alcohol component.

The antifungally preserved product obtained according to the invention comprises a food or feed product or an agricultural product having natamycin and polyhydric alcohol spread over the surface thereof. The natamycin is provided in an antifungally effective amount for preserving said product against the growth of fungi. When the product is a bakery product, natamycin is provided in an amount of 1 to 10 μg/cm of the surface of the product. Other products may need more natamycin to be preserved, as is clear to those skilled in the art.

The following examples illustrate the invention.

Example 1

A ready-to-use natamycin composition was prepared as follows:

Ethanol (95%, 10 g) was mixed with glycerol (89.6 g) to provide an alcoholic solvent mixture. 0.4 g of Natamax® (natamycin provided from Danisco A/S and containing 50 % lactose as a diluent) was added to the solvent mixture to provide a liquid composition with 200 ppm natamycin. The natamycin was readily soluble in the solvent after a few minutes mixing. The natamycin seemed to form a true solution in the glycerol/ethanol solvent.

The liquid composition was completely stable and natamycin did not separate out on standing. After 10 weeks of storage, no separation of the natamycin from the solution could be seen. There was no microbial growth in the composition during the storage.

Ethanol was also added in higher concentration (up to 30%) to the solvent mixture to reduce the viscosity. The solution with 30% ethanol was very easy to spray. A clear smell of ethanol was noted during spraying. Increasing the ethanol content further would reduce the viscosity still further, but the handling of liquids with more than 30% ethanol poses certain hazards, wherefore higher ethanol amounts should be avoided.

Example 2

A ready-to-use natamycin composition was prepared as follows:

An alcoholic solvent was made by combining propylene glycol and glycerol. Natamycin in the form of Natamax® (from Danisco A/S) was added to the solvent to provide a 200 ppm natamycin liquid composition having the following components (by weight)

0.4% Natamax®

50.0% propylene glycol

49.6% glycerol

The Natamax® dissolved in the solvent mixture with a couple of hours of mixing. The propylene glycol lowered the viscosity of the glycerol solvent and the composition was suitable for spraying. The absence of ethanol reduced the volatility of the solvent and eliminated any potential hazards.

The solution was stored for 10 weeks without any settling and without microbial growth.

Example 3

A liquid non-aqueous natamycin concentrate was made as follows:

Natamycin in the form of Natamax SF (from Danisco A/S, no lactose diluent included) was added to glycerol to make a mixture having 1200 ppm of natamycin and the following components (by weight):

1.2% Natamax SF

98.8%glycerol

The natamycin did not seem to truly dissolve in the glycerol, but the suspension/solution of natamycin was like a stable sol. The glycerol composition was thick enough to keep the natamycin suspended. After 10 weeks of storage, the composition was still uniform and no microbial growth had occurred.

Before use the concentrate was diluted with water. The dilution water contained 0.1 % of a stabilizer (50% xanthan gum and 50% guar gum) and 0.5% salt (NaCl). 1 part of the concentrate was diluted with 2 parts of water. The diluted concentrate remained physically stable for more than 10 weeks.

Example 4

Bread loaves were baked by normal procedures. The main ingredients were flour, sugar, salt, shortening, dry yeast and water. Directly after baking the loaves were detinned and then sprayed with the natamycin compositions of examples 1 and 2, respectively. The amount of natamycin on the surface of the loaves was analysed and was found to be about 1.5 μg/cm ² . No natamycin was detected in any sample below the 3 mm depth that was analysed, which indicates that the natamycin composition did not migrate past the crust.

The loaves were sliced and packed in plastic bags after cooling. The bags were stored at ambient conditions (22-24 ⁰ C, relative humidity 66%) for 12 days. Bags with untreated loaves were stored in the same manner as controls.

After 4 days, the control loaves showed clear growth of mould and were wholly covered by mould mycelium on day 12. The loaves treated with the natamycin compositions kept mould- free for 11 days. On day 12 small colonies of mould were seen on the crust of some of the loaves.

The freshly baked treated and untreated loaves were subjected to a triangle sensory testing program. No significant difference in taste could be observed between the treated and untreated loaves.

Based on the description and examples a person skilled in the art is able to apply the invention to a wide variety of food products.