HEAT-STERILIZABLE WATER AND OIL EMULSION

Abstract: A heat-sterilizable water and oil emulsion, preferably an O/W-emulsion, is obtained by incorporating from 0.05-5 wt.% each of a lyso-phospholipid (I) and a lipid-binding protein (II). Preferably the weight ratio between (I) and (II) is about 1:1. (I) is preferably obtained by treating a phospholipid or phospholipid-fraction with phospholipase A, and (II) is preferably blood serum albumin. Also a process of preparing the heat-sterilizable emulsions has been described.

Description: This invention relates to a heat-sterilizable water and oil emulsion, particularly an oil-in-water emulsion, and to a process for the preparation thereof. One of the requirements for oil-in-water emulsions of the mayonnaise, French dressing or salad dressing type is that these emulsions should be stable against acetic acid adapted yeasts, lactobacilli and moulds, so that, during storage of the emulsion in sealed containers, the product will not become contaminated. When providing conditions resulting in a product that is stable against acetic acid adapted microorganisms, however, there is the inherent disadvantage that the product must contain chemical preservatives, which are used to inhibit the growth of unacceptable microorganisms, and which include sorbic acid, benzoic acid, propionic acid or sulphite and/or a large proportion of acetic acid. On the other hand there is, however, an ever increasing want for milder, preservative-free products and, to reconcile these two conflicting requirements, it would be of advantage if it were possible to sterilize the water and oil emulsion without breaking the emulsion when it is heated to sterilization temperatures, particularly with high oil contents. It has now been found that the use of a mixture of lyso-phospholipid and blood serum albumin in the preparation of water and oil emulsions leads to emulsions having an improved heat stability, so that they can be heat-sterilized without breakage of the emulsion. Accordingly, the present invention relates to a heat-sterilizable water and oil emulsion, characterized in that it comprises a stabilizing amount of a mixture of a lyso-phospholipid and blood serum albumin in which the weight ratio of blood serum albumin to lyso-phospholipid is 1 : (0.3-5). The emulsions prepared according to the invention preferably have the aqueous phase as the continuous phase. The amounts used of both lyso-phospholipid and blood serum albumin are up to 5 percent by weight of the total emulsion, higher amounts being possible but not adding materially to the heat-stabilizing action. In general, from 0.05 to 5 percent by weight, and preferably from 0.1 to 3 percent by weight, of the total emulsion of each of the components of the emulsion stabilizer are used. The relative amounts of the two components may vary, but in general the weight ratio of blood serum albumin and lyso-phosphplipid is 1 : (0.3-5) and it has been found that the weight ratio of about 1 : 1 between the two components yields smooth and heat-stable products with a high viscosity. It has also been found that the consistency of the water and oil emulsions can be controlled by means of the weight ratio between the blood serum albumin and the lyso-phospholipid. The blood serum albumin is preferably bovine or porcine blood serum albumin. The lyso-phospholipid is a phospholipid in which one fatty acid radical attached either at the 1- or the 2-position of the glycerol part of the phospholidip molecule has been replaced by a hydroxyl group. The lyso-phospholipid is preferably obtained by treating a phospholipid of vegetable or animal origin with phospholipase A, preferably phospholipase A₂, such that a degree of conversion of at least 10%, preferably at least 25%, is reached. The degree of conversion is expressed as the percentage of converted phosphatidyl choline plus phosphatidyl ethanolamine based on the total amount of phosphatidyl choline plus phosphatidyl ethanolamine present before conversion. An easy method to obtain the figures required to calculate this percentage is quantitative thin-layer chromatography. As the phospholipid to be treated with phospholipase A, also lecithin fractions, for example the ethanol-soluble and the ethanol-insoluble fractions, may be used, such as the commercially available lecithin fractions Bolec F and Bolec C (Registered Trade Marks; Unimills, The Netherlands). Examples of suitable lyso-phospholipids are the soya bean phospholipids or egg phospholipids, which have been treated with phospholipase A₂, such that a degree of conversion of at least 10%, preferably of at least 25%, has been reached. Commercially available products which can be used are Bolec I, Bolec FS-M and Bolec CM (Registered Trade Marks; Unimills, The Netherlands). The water and oil emulsions according to the present invention contain from 5 to 85 percent by weight, preferably from 40 to 85 percent by weight of oil. The oil may also comprise a small amount of solid fat. By fat we understand triglyceride which is hard at room temperature (15-25°C). The oil and/or the fat may be of vegetable or animal origin and may be a synthetic oil and/or fat. It may be a single oil or fat or fat fraction or a mixture of oils or fats and/or fat fractions. At least part of the oil and/or fat may be replaced by a liquid or solid low-calorie fat replacer. Particularly suitable fat replacers are the edible polyesters of polyhydric alcohols having at least four free hydroxyl groups, such as polyglycerols, sugars or sugar alcohols, and saturated or unsaturated, straight or branched alkyl chain C₈-C₂₄ fatty acids. The polyhydric alcohol fatty acid polyesters include any such polyesters or mixtures thereof of which, on an average, at least 70% of the polyhydric alcohol hydroxyl groups have been esterified with the fatty acids. Also fatty alkyl ether derivatives of glycerol, esters of C₈-C₂₄ fatty alcohols and polycarboxylic acids, waxes and microcrystalline cellulose can be used for replacing at least part of the oil or the fat. The water and oil emulsions according to the present invention may also comprise vinegar, lime or lemon juice, edible acids, sweetening agents, salt, herbs, spices, mustard, flavouring agents, vegetable particles, emulsifying agents, colouring agents, gums and stabilizers, but the amount and the type of these additives should be such that the emulsions obtained will be mild and preservative-free. The present invention also relates to a process of preparing oil and water emulsions, in which a stabilizing amount of a mixture of a lyso-phospholipid and blood serum albumin is incorporated in the emulsion. In general, from 0.05 to 5 percent by weight of the total emulsion of each of the components of the emulsion stabilizer are used. The weight ratio of the two components may vary, but preferably this ratio is about 1 : 1. The invention is now illustrated by the following examples. EXAMPLE I A mayonnaise was prepared, using the following recipe: Soybean oil 708 g Water 200 g Sugar 16 g Sodium chloride 2 g Acetic acid solution (10%) 58 g Bovine blood serum albumin 8 g Defatted ethanol-soluble fraction of soybean phospholipid which has been treated with phospholipase A₂ 8 g 1000 g The bovine blood serum albumin was dissolved in water while vigorously stirring by means of an Ultraturrax. The solution obtained was heated to 40-50°C and subsequently the lyso-phospholipid was added and dispersed, using the Ultraturrax mixing device. Then all dry ingredients were added and subsequently the oil addition was started under stirring in a Hobart mixer. After addition of two thirds of the oil, the acetic acid solution was added while stirring. The final mixture obtained was homogenized, upon which a smooth, mild-tasting mayonnaise was obtained, which could be heated in a water bath at 100°C for 30 minutes without the emulsion breaking. EXAMPLES II - XII In the following examples, mayonnaises were prepared in the same way as described in Example I, using the same recipe with the exception of the emulsion stabilizer, which was changed in composition as indicated in Table I. In order to arrive at a total charge of 1000 grams, the amount of water was changed to compensate for a smaller or larger total amount of emulsion stabilizer. In all the Examples the final emulsions obtained could be heated to 100°C for 30 minutes without breaking the emulsion, and for the remainder they were rated, using the following appreciation marks: Mark Emulsion appearance Particle size µm Bostwick value after heating 30 min. at 100°C in cm/30 s 1 Thin 5-10 5-10 2 Thin 4-10 2-5 3 Thick 1-5 0-2 Example Bovine blood serum albumin (wt.%) Lyso-phospholipid as in Example I (wt.%) Rating II 0.2 0.3 2 III 0.2 0.4 2 IV 0.4 1.0 1 V 0.4 1.2 1 VI 0.8 1.6 2 VII 0.8 1.2 3 VIII 0.8 0.4 3 IX 1.3 1.5 3 X 1.3 1.2 3 XI 1.3 0.8 3 XII 1.3 0.4 3 From these results it can be concluded that the weight ratio between the lipid-binding protein and the lyso-phospholipid may vary widely. EXAMPLES XIII - XXII In the following examples mayonnaises were prepared in the same way as described in Example I, using the same recipe with the exception of the emulsion stabilizer, which was changed in composition as indicated in Table II and Table III. In all examples the final emulsion obtained could be heated to 100°C for 30 minutes without breaking the emulsion. The emulsions were rated as indicated for Examples II-XII. Example Porcine blood serum albumin (wt.%) Lyso-phospholipid as in Example I (wt.%) Rating XIII 0.4 0.4 2 XIV 0.8 0.8 1 XV 1.2 0.8 2 XVI 1.6 1.2 2 Example Bovine blood serum albumin (wt.%) Lyso-phospholipid Rating Type Amount (wt.%) XVII 0.8 Soya phospholipid treated with phospholipase A₂ 0.5 3 XVIII 0.4 ibid. 0.4 3 XIX XX XXI 0.8 0.8 0.8 Ethanol-insoluble fraction of soya phospholipid treated with phospholipase A₂ Ethanol-soluble fraction of soya phospholipid treated with phospholipase A₂ ibid. 0.5 0.6 2.4 3 3 2 XX XXI 0.8 0.8 Ethanol-soluble fraction of soya phospholipid treated with phospholipase A₂ ibid. 0.6 2.4 3 2 XXI 0.8 ibid. 2.4 2 XXII 0.8 ibid. 4.0 1 Comparative Example A A mayonnaise was prepared, using the following recipe: Soya bean oil 708 g Water 200 g Sugar 16 g Sodium chloride 2 g Acetic acid solution (10%) 58 g Chicken egg white 8 g Defatted ethanol-soluble fraction of soya bean phospholipid treated with phospholipase A₂ 8 g 1000 g The mayonnaise was prepared as described in Example I. Upon heating the mayonnaise at 100°C for 30 minutes the emulsion broke. Comparative Example B Comparative Example A was repeated, but now using 8 g of sodium caseinate instead of 8 g of chicken egg white. The mayonnaise obtained was already broken at 20°C. These two comparative examples clearly show that it is essential to use blood serum albumin as one of the components of the emulsion stabilizer.

Claims: A heat-sterilizable water and oil emulsion, characterized in that it comprises a stabilizing amount of a mixture of blood serum albumin and a lyso-phospholipid in which the weight ratio of blood serum albumin to lyso-phospholipid is 1: (0.3-5). An emulsion according to claim 1, which is an oil-in-water emulsion. An emulsion according to claim 1 or 2, in which the amounts of lyso-phospholipid and of blood serum albumin each are from 0.05 to 5 percent by weight of the total emulsion. An emulsion according to claims 1-3, in which the amounts of lyso-phospholipid and of blood serum albumin each are from 0.1 to 3 percent by weight of the total emulsion. An emulsion according to claims 1-4, in which the weight ratio between the lyso-phospholipid and the blood serum albumin is 1:1. An emulsion according to claim 1-5, in which the lyso-phospholipid is obtained by treating a phospholipid or a phospholipid-fraction with phospholipase A. An emulsion according to claim 1-5, in, which the lyso-phospholipid is obtained by treating a phospholipid or a phospholipid-fraction with phospholipase A such that a degree of conversion of at least 10% is reached. An emulsion according to claim 6 or 7, in which the phospholipase is phospholipase A₂. An emulsion according to claim 1-8, in which the oil content is from 5 to 85 percent by weight of the total emulsion. An emulsion according to claim 1-8 in which the oil content is from 40 to 85 percent by weight of the total emulsion. An emulsion according to claim 1-10, in which at least part of the oil is replaced by a low-calorie fat replacer selected from the group consisting of: the edible polyesters of polyhydric alcohols having at least four free hydroxyl groups, such as polyglycerols, sugars or sugar alcohols, at least 70% of the hydroxyl groups on an average being esterified with saturated or unsaturated, straight or branched alkyl chain C₈-C₂₄ fatty acids, fatty alkyl ether derivatives of glycerol, esters of c₈-c₂₄ fatty alcohols and polycarboxylic acids, waxes, microcrystalline cellulose, or mixtures thereof. A process of preparing heat-sterilizable water and oil emulsions according to claim 1-11, characterized in that a stabilizing amount of a mixture of blood serum albumin and a lyso-phospholipid in which the weight ratio of blood serum albumin to lyso-phospholipid is 1:(0.3-5) is incorporated therein.

Inventors: DUTILH, CHRISTIAN ELIE
Applicants: UNILEVER N.V., UNILEVER PLC
Application year: 1988
Main classification: A23D7
IPC codes: A23L1, A23D7