A PROCESS FOR PROTECTING FAT-BASED AQUEOUS EMULSION PRODUCTS AGAINST METAL-CATALYZED OXIDATION AND A PRODUCT THUS PROTECTED

Abstract: Fat-based aqueous emulsion products having a fat content of 10-95 % by weight comprising oxidation-sensitive fats/-oils and conventional additions, including optionally conventional antioxidants and emulsifiers, are admixed with a combination of citrate and lecithin in amounts which protect the product effectively against metal-catalyzed oxidation. The products are normally to contain 0.01-1 % by weight of citrate calculated as citric acid and 0.01-1 % by weight of lecithin, and the agents are preferably added to the aqueous part prior to the emulsification. The combination of citrate and lecithin serves as an effective metal chelator and can particularly replace EDTA which has previously been used as a metal chelator in such emulsion products.

Description: A process for protecting fat-based aqueous emulsion prod¬ ucts against metal-catalyzed oxidation and a product thus protected The present invention relates to a fat-based aqueous emulsion product having a fat content of 10-95% by weight, preferably 20-82% by weight and more preferably 40-80% by weight, comprising oxidation-sensitive fats/- oils and conventional additions, including optionally conventional antioxidants and emulsifiers, said product being effectively protected against metal-catalyzed oxi¬ dation. The invention also relates to a process for pro¬ tecting fat-based aqueous emulsion products of this type against metal-catalyzed oxidation. BACKGROUND OF THE INVENTION It has frequently been assumed that problems of oxidation of fat-containing products primarily occur by wrong proc¬ essing of fat/oil which form part of the raw materials of the product. This is correct in fact, in the sense that a beginning oxidation of fat/oil used for production will continue in the finished product. High quality products cannot be made from poor raw materials. For very oxidation-sensitive fats/oils having a great content of unsaturated fatty acids, in particular poly- unsaturated fatty acids, a good raw material quality, however, is not enough. If these particularly sensitive fats/oils are not specially protected, a destructive oxi¬ dation of the finished product will be observed in a sur¬ prisingly short time. Various factors, through their presence, separately in¬ crease the risk of oxidation of fats: light, heat, oxy¬ gen, enzyme activity and metal ions. The exercise of a certain care in the handling of raw ma¬ terials and in the production makes it possible to limit the presence of light, heat and oxygen to a level where these factors do not constitute a problem. Also the en¬ zyme activity may be kept at an acceptable level partly by using raw materials of a sufficiently good quality and partly by maintaining a good hygiene in connection with raw materials and product or by heat treatment. As regards metal ions, it has been found to be somewhat more difficult and frequently to take considerably more resources to keep the contamination caused by these at a level where they do not cause oxidation problems . Usually, antioxidants are added to fats and oils to pre- vent oxidation and thereby rancidity of these. Such anti¬ oxidants are used in many different combinations, and sometimes a distinction is made between antioxidants proper and synergists for these. Further, several func¬ tions are ascribed to some additives; e.g. lecithins are used, which are a group of phospholipids, both as emulsi¬ fiers and as antioxidants. A number of various combinations of antioxidants for use in fats as such is known. It is known e.g. from US Patent Specification No. 2 494 114 to stabilize fatty materials against oxidation by adding a mixture of nordihydroguaiaretic acid (NDGA) , 0.01-0.05%, citric acid, 0.001-0.005%, and lecithin, 0.01-0.05%. According to the patent specification it is the stabiliz¬ ing effect of NDGA which is to be enhanced, and the test results stated in column 2 show that citric acid as well as lecithin in the stated amounts have a synergistic ef- feet together with NDGA. Nothing is said about special problems of metal-catalyzed oxidation. US Patent Specification No. 5 230 916 relates to a proc¬ ess for producing an oil soluble antioxidant composition, comprising dissolving an ascorbic acid in a polar sol¬ vent, dissolving a phospholipid in a non-polar solvent, mixing the solvents, and removing the solvent from the mixture. The resulting composition, which is soluble in non-polar solvents, may then be combined with other anti- oxidant components, in particular with one or more anti¬ oxidants selected from citric acid, tocopherols and rose¬ mary extract. The patent specification states the compo¬ sition of antioxidants in a fish oil with the following percentages with respect to the oil: 0.05-0.2% by weight of tocopherols, 0.01-0.04% by weight of ascorbic acid, 0.01-0.04% by weight of citric acid and 0.1-0.4% by weight of de-oiled soy bean phospholipids (soy bean leci¬ thin) . The patent specification only mentions the combi¬ nation of natural antioxidants which together have a syn- ergistic effect, and mentions nothing about metal-cata¬ lyzed oxidation. US Patent Specification No. 4 913 921 relates to food products containing fish oils stabilized with fructose. The food product comprises about 0,1 to 80 % by weight of a deodorized nonhydrogenated fish oil being substantially free of fish flesh, said fish oil containing (1) about 150 to 200 ppm of a fish oil stabilizing antioxidant and (2) about 1500 to 2000 ppm tocopherol; and the food prod- uct further comprises about 0,5 to 30 % by weight of fructose. According to the specification one important group of foods for which the described invention is paticularly suitable consists of emulsions comprising wa¬ ter and a triglyceride and, especially, stable emulsions which typically additionally comprise an emulsifier in- eluding both oil-in water and water-in-oil emulsion types. Among employable emulsifiers is mentioned hydroxy- lated lecithin. The food compositions may also include conventional oil stabilizing materials such as antioxi¬ dants, TBHQ, BHA or BHT. However, in column 5, lines 34 to 37 it is said that not all food approved antioxidants have been shown to help; for example, the use of lecithin has been shown to actually aggravate development of fish flavours. Preferred products include 10 to 150 ppm (based on total oil), preferably 100 to 150 ppm, of a chelating agent desirably selected from the group consisting of citric acid, phytic acid, ethylene diamine tetraacetate and mixtures thereof . In the examples an antioxidant blend is used which is de- fined in Examples 1, 2 and 3 as follows: • 60 % tocopherol • 30 % TBHQ mixture comprising - 32 % glycerol monooleate - 30 % corn oil - 20 % TBHQ - 15 % propylene glycol 3 % citric acid • 10 % partially hydrogenated soybean oil with BHA. The dosage of this antioxidant blend in the examples ranges from 0.02 weight % (Example 11) to 0,27 weight % (Example 7) and, thus, the maximum content of citric acid exemplified in a food product according to US Patent No. 4 913 921 is 0.0024 % by weigt of the product. There is no exemplification of any use of lecithin, and actually such use is warned against as noted above. US Patent Specification No. 4 765 927 describes an anti- oxidizing composition for use in fat or oil, comprising one or more conventional antioxidants, in particular a mixture of tocopherol and a phospholipid, together with a condensed phosphate and citric acid as synergists. The examples use palm oil with a content of 0.02% of toco¬ pherol, 0.001-0.1% of lecithin, 0.005-0.05% of various condensed phosphates and 0.0025% of citric acid. Metal- catalyzed oxidation is not mentioned here either. US Patent Specification No. 4 906 412 describes a process for stabilizing lauric acid containing fats and oils against both hydrolytic and oxidative rancidity by addi¬ tion of a chelating amount of citric acid and lecithin in an amount which provides 0.003-0.03% of active phosphol- ipids based on the weight of the fat or the oil . It is stated in the patent specification that it is a desirable practice in the deodorization of fats and oils to add citric acid to the oil as a final step. According to the patent specification this takes place conventionally in an amount of about 0.002%, although as much as 0.01% may be used. It is usually added as an aqueous solution under vacuum so that the water evaporates. The citric acid serves as a metal chelator, in particular for traces of copper and iron which act as prooxidants for oil. How¬ ever, in particular lauric acid-containing fats and oils, such as coconut oil and palm kernel oil, also tend to un¬ dergo hydrolytic rancidity in the presence of water. The problem of the presence of citric acid is that, in a con- centrated aqueous solution, it can actually serve as a catalyst for the hydrolysis reaction and cause an in¬ crease in the percentage of free fatty acid. Therefore, lecithin is added as a moisture binder. DE Patent Application, Publication No. 30 02 037 Al de¬ scribes a whippable fat emulsion consisting of a mixture, emulsified in an aqueous medium, of (A) 90-98.5% by weight of a natural, optionally hardened vegetable fat, (B) 0.5-3% by weight, preferably 1-2% by weight of leci¬ thin, (C) 1-5% by weight, preferably 2-3% by weight of a (C6-C22) fatty acid monoglyceride lactic acid ester, said aqueous medium containing (D) 0-2% by weight, preferably 0.2 1% by weight of one or more salts from the group Na pyrophosphate, Na hydrogencarbonate and Na citrate. The stated quantitative ratio of the fat/emulsifier mixture to the aqueous medium is 1:1.5 to 1:5, preferably 1:2 to 1:4. The combination of lecithin (B) and fatty acid mono¬ glyceride lactic acid residues (C) serves as an emulsi- fier for the fat component (A). The salts (D), of which Na pyrophosphate is the preferred one, are mentioned as stabilizers. Nothing is said about special problems of metal-catalyzed oxidation or about any special effect of a combination of lecithin with citric acid. The single example uses 12.7% of lecithin and 0.15% of a salt mix¬ ture consisting of 53.7% of Na pyrophosphate, 43.9% of Na hydrogen carbonate and 2.4% of Na citrate based on the total emulsion; this means that the emulsion just con¬ tains 0.0036% of Na citrate. US Patent Specification No. 4 963 385 describes food emulsions containing fish oils, where the water phase in¬ corporates a stabilizer for the fish oil comprising a sugar or a sugar alcohol and optionally a metal ion chelator. Citric acid salts and ester thereof, e.g., are mentioned as useful metal chelators; but the only exem- plified one is ethylene diamine tetra-acetic acid (EDTA) . US Patent Specification No. 4 772 483 describes a low calorific butter substitute comprising cream having a butter fat content of about 40%, non-fat dry milk, salt, locust bean gum, lecithin, mono- and diclycerides, citric acid, water and natural flavour. Lecithin is added as an emulsifier in an amount of 0.20% by weight and citric acid as an acidity adjusting agent in an amount of 0.10% by weight. Nothing is said about the shelf life of the product. In any production of emulsified products, metal ion con¬ taminations will occur to a greater or smaller degree. These may e.g. originate from the water used, from milk or other milk based ingredients, from other protein sources, from salt or from other ingredients or additives in the product. Particularly in emulsion products containing fats with many unsaturated fatty acids and particularly with many polyunsaturated fatty acids, the metal ions may give rise to a fast oxidation which will make the quality of the product in terms of smell and taste totally unacceptable in a surprisingly short time. It is well-known that conventional antioxidants (toco¬ pherols, BHA, BHT, NDGA, ascorbic acid and salts thereof, gallates, etc.) do not provide oxidation protection of any practical importance if a product contains an oxida- tion-sensitive fat/oil and is contaminated with metal ions . To provide all ingredients in a form in which they do not contain metal ions of any practical importance will be difficult and expensive at best, and impossible at worst. Particularly iron and copper ions are extreme oxidation promoters even in very low concentrations ( few ppm for iron and few ppb for copper) . It has therefore been com- mon practice to complex-bind these metal ions in the wa¬ ter phase with ethylene diamine tetra-acetic acid (EDTA) . This has been found to be necessary particularly in emul¬ sion products with a reduced fat content. EDTA is an extremely effective water soluble metal chela- tor which on one hand effectively binds the harmful metal ions and on the other does not have any unfortunate side effects on the product, such as off-flavour, bad smell or discoloration. However, in the EU EDTA will not be permitted for use in other emulsion products than emulsified sauces and minarine when the EU directive on other additives than colorants and sweeteners is implemented in the individual EU countries. Therefore, what is missing is a water solu- ble alternative with a similar effect and with a smell, taste and colour compatible to the same degree with the product which is to be protected. Such a protection will not be necessary in ordinary fat-based products contain¬ ing fats which are not particularly sensitive to oxida- tion. The lower the fat content of the product is, and the more oxidation-sensitive the fat of the product is, the greater the need is for a protection against the metal-catalyzed oxidation, as a substitute for EDTA. SUMMARY OF THE INVENTION It has surprisingly been found that a combination of cit¬ rate with lecithin effectively binds the harmful metal ions in the water phase of fat-based emulsion products and thereby provides the desired protection against metal-catalyzed oxidation in fat-based emulsion products, such as e.g. margarine and minarine. Citrate added to the water phase in a concentration, cal- culated as citric acid, of at least about 0.01% by weight of the finished product together with lecithin in a con- centration of at least about 0.01% by weight of the fin¬ ished product has been found to have a metal-chelating effect which greatly exceeds what might be expected on the basis of the effect of the said substances used indi- vidually. Accordingly, the fat-based aqueous emulsion product of the invention is unique in that it contains a combination of citrate and lecithin in amounts which protect the product effectively against metal-catalyzed oxidation. Generally, the emulsion product of the invention is to contain 0.01-1% by weight, preferably 0.05-1% by weight and more preferably 0.1-0.5% by weight, of citrate calcu- lated as citric acid and 0.01-1% by weight, preferably 0.05-1% by weight and more preferably 0.1-0.5% by weight, of lecithin. In practice, a safe protection against metal-catalyzed oxidation without any form of off-flavour is obtained when the emulsion product contains 0.2-0.4% by weight of citrate calculated as citric acid and 0.2-0.4% by weight of lecithin. The process of the invention for protecting fat based aqueous emulsion products having a fat content of 10-95% by weight, preferably 20-82% by weight and more prefera¬ bly 40-80% by weight, comprising oxidation-sensitive fats/oils and conventional additions, including option- ally conventional antioxidants and emulsifiers, against metal-catalyzed oxidation, is unique by adding to the emulsion product during the production citrate and leci¬ thin in amounts which in combination protect the product effectively against metal-catalyzed oxidation. 10 The citrate and the lecithin are generally added in the amounts stated above. The citrate is normally added to the aqueous part prior to the emulsification. The preferred citrate is trisodiu citrate, but the citrate my also be added in the form of citric acid, which is converted into citrate in the sub¬ sequent pH adjustment with a base, e.g. NaOH. Preferably, a water soluble lecithin is used, and in that case it is also added to the aqueous part prior to the emulsification. But also fat soluble lecithins may be used, and in that case the lecithin is added to the fat part prior to the emulsification. DETAILED DESCRIPTION OF THE INVENTION As mentioned, the present invention can protect fat-based emulsion products with a fat content of 10-95% by weight, preferably 20-82% by weight and more preferably 40-80% by weight against metal-catalyzed oxidation. As a starting point, the invention is intended to protect products consisting of water-in-fat emulsions, but a per- son skilled in the art will appreciate that fat-in-water emulsions can be protected in the same manner. The invention comprises adding a combination of: - citrate and - lecithin in amounts which protect the product effectively against metal-catalyzed oxidation. Citric acid is a tribasic acid with the pK a values 3.1, 4.8 and 6.4 for the three acid groups. This means that chemical equilibrium will occur between citric acid, the monobasic acid residue, the dibasic acid residue and the tribasic acid residue primarily in the pH range 2-7.5. It is rather complicated to calculate the ratio of the sub¬ stances incorporated in the equilibrium, and the ratio is moreover affected by one or more of the substances occur¬ ring in the equilibrium. In other words, in the emulsion products of the invention the citrate is an equilibrium mixture of citrate ions formed in situ by addition of citric acid or a mono-, di- or tribasic citrate salt and subsequent pH adjustment with base or citric acid. The citrate may optionally also be a dibasic derivative of citric acid where one of the carboxyl groups of the citric acid is bound, e.g. in the form of an ester. It is moreover conceivable that the citrate anion may be replaced by other anions of polybasic acids with a simi- lar effect. The options include tartaric acid, malic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid and phthalic acid. Lecithin is a collective name of products which consist of a few well-defined substances and many more or less well-defined substances in varying amounts. It is common to non-purified lecithin (crude lecithin) that about one half or more consists of phospholipids which have an emulsifying effect. Other substances pres¬ ent in crude lecithin are fats (about 35%), free fatty acids, glycolipids, tocopherols, sterols and carbohy¬ drates. Most commercially available lecithins are pre¬ pared on the basis of soy beans, but lecithin is also found inter alia in rapeseed and yolk. The phospholipids consist of glycerol with fatty acids bound in positions 1 and 2 and with phosphoric acid bound in position 3. In turn, the phosphoric acid has bound to it a substance which decides which type of phospholipid is involved. It is primarily: choline (phosphatidyl choline, PC) ethanolamine (phosphatidyl ethanolamine, PE) inositol (phosphatidyl inositol, PI). In crude lecithin prepared on the basis of soy beans, the content of the 3 substances varies as follows: PC: 12-18% PE: 10-16% PI: 7-12% (Source: The brochure "Stern-Lecithin More than an Emul- sifier", 1985 from Stern, a lecithin manufacturer). In some commercial products the content may vary more of course, depending on purification and modification. The dosage of the individual lecithins, used in fat-based products in their function as emulsifiers, also varies much. Lecithin is frequently used together with other emulsifiers to give a special effect as anti-spattering in cooking margarines or as dough improvers in baking margarines . Lecithins are generally fat soluble, but some lecithins are dispersible in water. Good results have been obtained with such a water dispersible lecithin in connection with the present invention, but also fat soluble lecithins have shown a good effect. It is evident that a lecithin having a low natural con¬ tent of iron and copper will be preferred in connection with the present invention. The dosage of both citrate and lecithin is of 0.01-1%, preferably 0.05-1% and more preferably 0.1-0.5% of each ingredient. A higher dosage of the ingredients singly or in combina- tion may be used. It will not improve the effect noticea¬ bly, but, in contrast, can cause off-flavour in the fin¬ ished product in some cases . It may also be appropriate to use an additional antioxi- dant or antioxidant combination to protect the fat and the finished product. Usually, it will also be necessary to protect the physical stability of the finished product with at least one emulsifier in addition to lecithin. Emulsion products of the present type will frequently have a pH value in the range 4.5-6.5. It may very well be changed, but a reduction of pH per se will increase the risk of oxidation of the product, and a higher pH will reduce the bacteriological shelf life. Finally, a change in pH will affect the taste of the product. The invention will be illustrated more fully by the fol¬ lowing product examples and test examples . It is common to all the product examples that the emul¬ sion is produced as follows: - Fats and oils are weighed and molten together and heated to the desired emulsion temperature. - Fat-based ingredients are added to the fat mixture in consideration of possible special processes for the addi¬ tion of individual ingredients, as specified by the sup¬ plier. - The complete tempered fat phase is transferred to an emulsion tank. - The water phase is likewise weighed, mixed and tem- pered, and pH is not adjusted until all other ingredients have been mixed. - The water phase is added to the fat phase in the emul¬ sion tank with stirring. - The emulsion is processed in the perfector system under the conditions which are specified for each individual product. It applies to all the examples that the samples are pro¬ duced on a Gerstenberg & Agger test perfector. The emul¬ sion temperature was generally 45 °C, and the samples were made with a perfector capacity of about 20 kg/h and a cooling of -10 °C on 2 cooling pipes. The following abbreviations are used in the examples be¬ low: ADM: supplied by ADM Europoort B.V. Elbeweg 125 - Harboor 5840 NL-3198 LC Europoort RT, NL AO: supplied by Aarhus Oliefabrik A/S M.P. Bruunsgade 27 DK-8000 Arhus C, DK DI : supplied by Danisco Ingredients, DK Edwin Rahrsvej 38 DK-8220 Brabrand, DK LM: supplied by Lucas Meyer GmbH & Co. Ausschlager Elbdeich 62 D-20539 Hamburg, DE ST: supplied by Stern-Chemie Volkmar Wywiol An der Alster 81 D-20099 Hamburg, DE VM: supplied by Vamo Mills Prins Albertlaan 12 B-8870 Izegem, BE PRODUCT EXAMPLES Product example 1 (60% margarine) Water phase 38.59% water 1.0% salt 0.4% Na3 citrate 0.01% butter flavouring 3175 (DI) pH adjusted to 6.0 with citric acid Fat phase 59.19% fat mixture 0.4% lecithin "Vamothin SBX" (VM) 0.4% e ulsifier "Dimodan® OT" (DI) 0.01% butter flavouring 2520 (DI) 10 ppm β-carotene Fat mixture: 10% fish oil 65% rapeseed oil 25% hardened soy bean oil "Shoguwar 41" (AO) Product example 2 (60% margarine) Water phase: 33.39% water 5.0% non-acidified buttermilk 1.0% salt 0.2% Naβ citrate 0.4% lecithin "Emulfluid E" (LM) 0.01% butter flavouring 3175 (DI) pH adjusted to 6.0 with citric acid Fat phase 59.59% fat mixture 0.4% emulsifier "Dimodan® OT" (DI) 0.01% butter flavouring 2806 (DI) 8 ppm β-carotene Fat mixture: 10% fish oil 65% rapeseed oil 25% hardened soy bean oil "Shoguwar 41" (AO) Product example 3 (80% mixed product) Water phase 8.7% water 10.0% non-acidified butter milk 1.0% salt 0.4% a3 citrate pH adjusted to 5.8 with citric acid Fat phase 79.29% fat mixture 0.4% lecithin "Sternprime N-10 Top" (ST) 0.2% emulsifier "Dimodan® OT" (DI) 0.01% butter flavouring 2590 (DI) 8 ppm β-carotene Fat mixture: 10% butter fat 8% fish oil 20% coconut oil 30% hardened soy bean oil "Shoguwar 35" (AO) 32% rapeseed oil Product example 4 (liquid margarine) Water phase 11.40% water 5.0% non-acidified butter milk 1.0% salt 0.4% lecithin "Emulfluid E" (LM) 0.2% Na3 citrate pH adjusted to 5.8 with citric acid Fat phase 79.59% fat mixture 2.0% emulsifier "Grindsted® TS 209" (DI 0.4% emulsifier "Grindsted® CITREM LC" (DI) 0.01% butter flavouring 2469 5 ppm β-carotene Fat mixture: 100% rapeseed oil Product example 5 (minarine) Water phase 58.09% water 1.0% salt 0.4% a3 citrate 0.01% buffer flavouring 4151 (DI) pH adjusted to 6.0 with citric acid Fat phase 39.59% fat mixture 0.5% emulsifier "Dimodan® OT" (DI) 0.4% lecithin "Adlec" (ADM) 0.01% butter flavouring 4152 (DI) 5 ppm β-carotene Fat mixture: 25% hardened soy bean oil "Shoguwar 41" (AO) 15% fish oil 60% rapeseed oil Product example 6 (minarine) Water phase 50.19% water 5.0% non-acidified buttermilk 2.5% gelatine "Grindsted® G" (DI) 0.4% Na3 citrate 0.4% lecithin "Emulfluid E" (LM) 0.01% butter flavouring 4151 (DI) pH adjusted to 6.0 with citric acid Fat phase 39.99% fat mixture 0.5% emulsifier "Dimodan® OT" (DI) 0.01% butter flavouring 4152 (DI) 5 ppm β-carotene Fat mixture: 25% hardened soy bean oil "Shoguwar 41" (AO) 15% fish oil 60% rapeseed oil Product example 7 (70% fat spread) Water phase 28.4 % water 1.5 % salt 0.1 % Na3 citrate pH adjusted to 5,6 with citric acid Fat phase 69.68 % fat mixture 0.2 % emulsifier "Dimodan® LS" (DI) 0.02 % butter flavouring 2807 (DI) 0.1 % lecithin "Vamothin SBX" (VM) 10 ppm β-carotene Fat mixture: 5 % fish oil 65 % sunflower oil 30 % hardened soybean oil "Shoguwar 41" (AO) Product example 8 (65 % fat spread) Water phase 30.28 % water 1.9 % salt 2.5 % buttermilk powder 0.02 % butter flavouring 3175 (DI) 0.1 % a3 citrate 0.2 % lecithin "Emulfluid E" (LM) pH adjusted to 5.9 with citric acid Fat phase 64.78 % fat mixture 0.2 % emulsifier "Dimodan® LS" (DI) 0.02 % butter flavouring 2590 (DI) 6 ppm β-carotene Fat mixture: 7 % fish oil 65 % rapeseed oil 28 % hardened soybean oil "Shoguwar 41" (AO) Product example 9 (70 % fat spread) Water phase 26.28 % water 0.2 % Na3 citrate 0.2 % lecithin "Emulfluid E" (LM) 1.8 % salt 1.0 % skimmed milk powder 0.5 % gelatine "Gelodan G" (DI) 0.02 % butter flavouring 3175 (DI) pH adjusted to 6.0 with citric acid Fat phase 69.69 % fat mixture 0.3 % emulsifier "Dimodan OT" (DI) 0.01 % butter flavouring 2469 (DI) 8 ppm β-carotene Fat mixture: 5 % fish oil 65 % rapeseed oil 30 % hardened palm oil "Palmowar EE 42" (AO) Product example 10 (60 % fat spread) Water phase 33.45 % water 5.0 % buttermilk 1.0 % salt 0.15 % Na3 citrate 0.4 % lecithin "Emulfluid E" (LM) pH adjusted to 5.8 with citric acid Fat phase 59.6 % fat mixture 0.4 % emulsifier "Dimodan® LS" (DI) 0.01 % butter flavouring 2960 (DI) 8 ppm β-carotene Fat mixture: 11 % fish oil 22 % coconut oil 33 % hardened soybean oil "Shoguwar 35" (AO) 37 % rapeseed oil It is evident to every one familiar with the production of products of this type that the production factors emulsion temperature, perfector capacity, cooling and number of cooling pipes as well as emulsifier type and flavour selection may be varied much, without this really changing anything of importance to the present invention. Likewise, the selection of fats and oils in the products may vary indefinitely. It applies to many fat mixtures that the increased protection against metal-catalyzed oxidation provided by the present invention will not be necessary. Therefore, a changed selection of the vegeta¬ ble oil used or of marine oil or an addition of one ore more animal oils or fats does not change the effect of the invention. Finally, it will be without importance to the invention whether additives having another effect, such as hydro- colloids or the like which change meltdown or consis- tency, are added to the products. As regards the shelf life of the products of the inven¬ tion, it will be determined by other factors than the metal-catalyzed oxidation. (It will thus correspond to the shelf life of similar products without particularly oxidation-sensitive fats and/or oils) . TEST EXAMPLES To check the effect of the invention, a plurality of tests was performed with products artificially contami¬ nated with copper and/or iron ions in the form of CuS04 and FeSθ4 (spiking) and with products made with ordinary tap water. For the sake of comparison, all the test prod- ucts are 60% fat products with protein in the water phase and with about 10% of the fat phase consisting of unhard- ened fish oil. Unhardened fish oil has two advantages in this connection: 1) it must be considered one of the most oxidation- sensitive edible oils; 2) oxidized fish oil has an extremely unpleasant taste, which makes it easy to evaluate organoleptically whether a product with fish oil is oxidized. All the samples were evaluated by a panel of trained tasters according to the following marking scale: no fishy taste very faint fishy taste faint fishy taste distinct fishy taste strong fishy taste distinct smell of fish and very unpleasant fishy taste The samples are condemned as defective when all the tast¬ ers have given the mark 4 or above. Test example 1 Comparison of products without chelator, with EDTA and with Na3 citrate + lecithin ("Emulfluid E"). Spiking: 0.5% ppm Fe ++ added to the water phase Conclusion: With 0.5 ppm Fe ++ the present invention is just as effec¬ tive as EDTA in a test period of 6 weeks. Test example 2 Comparison of shelf life of samples with EDTA and with various dosages of Na3 citrate and lecithin ("Emulfluid E" ). Spiking: 2.5 ppm Fe ++ and 0.05 ppm Cu ++ . Conclusion: It seems that with the used extreme metal contamination of the products, 0.1 or 0.4% Na3 citrate together with 0.1% lecithin is not enough to prevent metal-catalyzed oxidation, while 0.6% Na3 citrate together with 0.1% lecithin and 0.4% Na3 citrate together with 0.4% lecithin is . It should be noted that the amount of metal ions in this test was so high that the metal taste of the prod¬ ucts was distinct. It must be assumed on the basis of this test that under normal circumstances 0.05% citrate together with 0.05% lecithin will be sufficient to pro- vide good protection against metal-catalyzed oxidation, and in most cases 0.01% citrate together with 0.01% leci¬ thin will give protection. Test example 3 Comparison of the effect of contaminating the water phase with 0.5 ppm Fe vs. the effect of contaminating the finished emulsion with 2.5 ppm Fe . No chelator is used in the test. Spiking Defect after 0.5 ppm Fe + in the water phase 3 days 2.5 ppm Fe in the emulsion 7 days Conclusion: Metal contamination applied directly to the products in the emulsion does not affect the shelf life of the prod¬ ucts to the same degree as metal contamination in the wa¬ ter phase. It may be concluded on the basis of this that metal contaminations applied through water or ingredients mixed in the water phase will be of greater importance to the shelf life of a product than metal contamination ap¬ plied through fat, oil or ingredients mixed in the fat phase, and than metal contamination applied after the wa¬ ter-in-oil emulsion has been prepared. Consequently, a chelator combination like the present invented one capa- ble of replacing the water soluble chelator EDTA will give the best protection against metal-catalyzed oxida¬ tion of fat-based products. Test example 4 Comparison of shelf life of samples with EDTA and Na3 citrate + lecithin, respectively, prepared with ordinary tap water. EDTA a3 citrate Lecithin Defect after 100 ppm 0 0 >12 weeks 0 0.2% 0.2% >12 weeks Conclusion: Samples prepared with ordinary tap water and a combina¬ tion of 0.2% Na3 citrate and 0.2% lecithin exhibit the same stability against oxidation as samples prepared with the previously usual 100 ppm EDTA. Test example 5 Comparison of shelf life of samples with a low content of the chelator components, and without spiking. EDTA Na3~citrate Lecithin Defect after - - - <4 days 100 ppm - - >8 weeks - 0.05% 0.01% 4 weeks - 0.01% 0.05% 6 weeks 0.05% 0.05% 6 weeks Conclusion: Samples containing as little as 0.01 % of either of the chelator components of this invention exhibit a signifi- cant prolonging of the shelf life compared to samples without any chelating agents. Test example 6: The product of product example 10 was tested in compa¬ rison with a similar product containing EDTA instead of the chelator combination according to the invention. EDTA Na3 citrate Lecithin Defect after 100 ppm - - >24 weeks - 0.15 0.4 >24 weeks Conclusion: The product prepared in Production example 10 exhibits a shelf life as regards the development of a fishy off- taste comparable with a similar product containing EDTA.

Claims: PATENT CLAIMS 1. A fat-based aqueous emulsion product having a fat con¬ tent of 10-95% by weight, preferably 20-82% by weight and more preferably 40-80% by weight, comprising oxidation- sensitive fats/oils and conventional additions, including optionally conventional antioxidants and emulsifiers, characterized in that it contains a combination of cit¬ rate and lecithin in amounts which protect the product effectively against metal-catalyzed oxidation. 2. An emulsion product according to claim 1, character¬ ized in that it comprises fats with polyunsaturated fatty acid residues. 3. An emulsion product according to claim 1 or 2, char¬ acterized in that it comprises fish oils. 4. An emulsion product according to any one of the pre- ceding claims, characterized in that it contains 0.01-1% by weight, preferably 0.05-1% by weight and more prefera¬ bly 0.1-0.5% by weight, of citrate calculated as citric acid and 0.01-1% by weight, preferably 0.05-1% by weight and more preferably 0.1-0.5% by weight, of lecithin. 5. An emulsion product according to claim 4, character¬ ized in that it contains 0.2-0.4% by weight of citrate calculated as citric acid and 0.2-0.4% by weight of leci¬ thin. 6. An emulsion product according to any one of the pre¬ ceding claims, characterized in that the citrate is an equilibrium mixture of citrate ions formed in situ by ad¬ dition of citric acid or a mono-, di- or tribasic sodium citrate and subsequent pH adjustment with NaOH or citric acid. 7. An emulsion product according to any one of the pre¬ ceding claims, characterized in that the lecithin is a water soluble lecithin. 8. An emulsion product according to any one of the pre¬ ceding claims, characterized in that it is a water-in-oil emulsion. 9. A process for protecting fat-based aqueous emulsion products having a fat content of 10-95% by weight, pref¬ erably 20-82% by weight and more preferably 40-80% by weight, comprising oxidation-sensitive fats/oils and con¬ ventional additions, including optionally conventional antioxidants and emulsifiers, against metal-catalyzed oxidation, characterized by adding to the emulsion prod¬ uct during the preparation citrate and lecithin in amounts which in combination protect the product effec¬ tively against metal-catalyzed oxidation. 10. A process according to claim 9, characterized by adding 0.01-1% by weight, preferably 0.05-1% by weight and more preferably 0.1-0.5% by weight, of citrate cal¬ culated as citric acid and 0.01-1% by weight, preferably 0.05-1% by weight and more preferably 0.1-0.5% by weight, of lecithin based on the total weight of the emulsion. 11. A process according to claim 10, characterized by adding 0.2-0.4% by weight of citrate calculated as citric acid and 0.2-0.4% by weight of lecithin based on the to- tal weight of the emulsion. 12. A process according to any one of claims 9-11, char¬ acterized by adding the citrate to the aqueous part prior to the emulsification. 13. A process according to any one of claims 9-12, char¬ acterized by adding the citrate in the form of trisodium citrate. 14. A process according to any one of claims 9-13, char¬ acterized by adding the citrate in the form of citric acid which is added to the aqueous part prior to the emulsification and is converted into citrate salt in the subsequent pH adjustment. 15. A process according to any one of claims 9-14, char¬ acterized in that the lecithin is water soluble and is added to the aqueous part prior to the emulsification. 16. A process according to any one of claims 9-14, char¬ acterized in that the lecithin is fat soluble and is added to the fat part prior to the emulsification.

Inventors: ENGELL ASTRID MARGRETHE, MADSEN SOEREN, ENGELL, ASTRID, MARGRETHE, MADSEN, SOEREN
Applicants: ENGELL ASTRID MARGRETHE, MADSEN SOEREN, MD FOODS AMBA, ENGELL, ASTRID, MARGRETHE, MADSEN, SOEREN
Application year: 1997
Main classification: A23D7
IPC codes: A23D7, C11B5