IL46844A - Preparation of water-dispersible stabilized reaction products of protein and alkylene glycol alginates - Google Patents

Description

o»oa n?»s «na n»a»s» naian ·ΪΪΙΟ man \td»e3»¾ s ip* a »p¾»Ki paVno PREPARATION OP WATER -DISPERSIBLE STABILIZED REACTIOH PRODUCTS OP PROTEIN AND ALKYLENE GLYCOL ALGINATES' The invention relates to the preparation of water dispersible stabilized reaction products of protein and alkylene glycol alginates. These stabilized reaction products are useful as food additives or foam stabilizers.

Various types of gels and gums have been used in food compositions as functional ingredients. Such materials function as thickening agents, suspending agents and structural stabilizers.

One of the gums is algin or alginic acid. Alginic acid is a polymannuronic acid derived from kelp. It is available, among other forms, as the sodium salt (sodium alginate) and as the alkylene glycol esters. J The alkylene glycol alginates have been employed as functional ingredients in foods.

Alkylene glycol alginate is an esterification reaction product of some of the' carboxylic acid groups or alginic acid and an alkylene oxide. Alkylene glycol alginates are most generally available as propylene glycol esters of alginic acid in which from about o to ■abuul 90 of the carboxyl groups have been esterified with propylene glycol, the remaining groups being either free or neutralized with a base.

Unlike salts of alginic acid, the alkylene glycol alginates are generally not precipitated in acidic solutions as low as pH 2-3. Propylene glycol alginate is recognized as being a safe food additive for thickening, suspending or as a solids stabilizer for acidic food stuffs such as acidic fruit drinks.

Propylene glycol alginates have generally not been used in alkaline systems since it was thought that alkaline conditions would lead to saponification of the ester groups and a reduction in viscosity.

McDowell discloses in United States patent 3,503,769, that propylene glycol alginate under mild alkaline treatment provides a product with modified properties, i.e., higher viscosity and improved suspending ability. The result can be achieved by forming an acidic solution of propylene glycol alginate alone or in combination with a hydroxyl containing polymer such as starch, carboxymethyl cellulose, guar gum, or polyvinyl alcohol, adding sodium carbonate to raise the pH to the alkaline side, holding the solution for fifteen minutes at 18°C. and acidifying with acetic acid.

While the product proposed by the method disclosed in the McDowell patent is an improvement over propylene glycol alginate, a greater improvement in the thickening properties is desirable.

It is also known that proteins such as gelatin, casein, and albumin can be reacted with propylene glycol alginate under alkaline conditions, i.e., above pH 9.6, to form an insoluble (non-dispersible) product. United States patent 3,378,373 (British counterpart 962,483) and British patent 987,797, teach that this reaction is useful in photographic processes for hardening gelatin photographic layers containing silver halide. However, this product is insoluble (non-dispersible) and cannot be employed as a functional food additive as it is not water dispersible.

U.S. patent 3*407,076 teaches that a globulin type protein can be reacted with an anionic polyelectrolyte such aa sodium alginate at an acidic pH near the isoelectric point of the protein (about 4.5). The reaction product is a complex taught to be useful in preparing whipped toppings.

U.S. Patent 2,444,241 teaches that proteins can be recovered from cheese whey by raising the pH of the whey aboge 7, adding sodium alginate and reducing the pH to the acidic range. A precipitate forms upon acidification.

However, water dispersible reaction products of protein and alkylene glycol alginate are unknown in the art. The present invention relates to water dispersible reaction products of protein and alkylene glycol alginates. Such products have useful functional properties suitable for uses such as thickening agents, suspending agents and structural stabilizers stabilizers or foam stabilizer for such foams as fixe fighting foams.

In accordance with the present invention there is provided § method for preparing water dispersible reaction products of water dispersible proteins and alkylene glycol alginate which comprises :- a) reacting a mixture of protein , whi ch is dispersible in water at a temperature of 30°C or below , and alkylene glycol alignate dispersed in water, at a reactive pH as hereinbefore defined of at least 9. 5 at a reaction temperature to obtain a reaction mixture containing a water dispersible reaction product , said reaction mixture having a vis cosity increase of at least four times the vis cosity Of an aqueous mixture of unreacted water dispersib le protein and unreacted alkylene glycol alginate as measured by a Brookfie ld viscometer , and b) adjusting the pH of the reaction mixture to 7 or below whereby a s tabi lized reaction product as hereinbefore defined of protein and an alkylene glycol alginate dispersed in water is obtained.

The stabi lized reaction product of this invention can be dried with appropri ate care and ' recovered as a dry , water dispersib le material capable of forming thickened dispersions .

As used herein , the term " reaction mixture" means the alkaline reacted mixture of protein and alkylene glycol alginate.

As used herein , the term " reaction product" means the product in the reaction mixture formed by the alkaline reaction of the protein and the alkylene gly col alginate .

As used herein the term "s tabi li zed reaction product" means the product in the reaction mixture formed by the alkaline reaction of protein and the alkylene glycol alginate which has been treated to halt further reaction as by neutralizing by acidification of the reaction mixture .

Some of the water-dispereible proteins and water-dispersible reaction products may be in the colloidal state.

Water insoluble reaction products of protein such as gelatin and propylene glycol alginate can be prepared. When such water insoluble products are mixed with water, no dispersion of the product occurs. Even after prolonged stirring, such water insoluble products settle out.

The reaction products formed by reaction of alkylene glycol alginate and proteins are believed to be polymeric in nature. Whether or not these products can be effectively employed as functional ingredients is dependent upon the degree of reaction. If the degree of reaction is too great (i.e., molecular weight too high), the produot will be of little use as a food ingredient, as it will be relatively non-dispersible in water. If the degree of reaction is too low, it will,be dispersible in aqueous systems but will not provide desirable functional properties.

There is, however, a degree of reaction between alkylene glycol alginates and proteins where a produot is formed which is compatible with an aqueous system and yet provide the functional characteristics desired.

These desired products can be added to water and dispersed. The products absorb water, swell, and form thickened dispersions.

The resulting thickened dispersions can be dehydrated and the procedure repeated. As stated before* this ability to form such dispersions and not settle out is defined as "dlepersibility". Accordingly, a product having an excessively high degree reaction cannot disperse in water. Such a product is defined as "non-dispersible" or insoluble and is outside the scope of this invention.

In contrast, the water dispersible stabilized reaction products prepared by the method of the present invention swell and disperse when added to water. Preferably at least 90$, more preferably at least 9% and desirably above 9£$ by weight of the stabilized reaction product is dispersible and still within the definition of a product prepared in accordance with the present invention. It has been found that generally some mixing ie desirable in that the stabilized reaction product may not disperse easily without some assistance.

The stabilized reaction products of the invention tend to have the appearance of egg albumen, clear to off white in color, and varying in consistency. Stirring of a dispersion of the stabilized reaction product generally results in the entrapment of air bubbles throughout the dispersion giving the dispersion a cloudy appearance.

The products of the present invention are water dispersible stabilized reaction products of protein and alkylene glycol alginate. These products can be used as formed after stabilization or Isolated and dried, I.e. recovered as a dry product from the aqueous mixture afer stabilization.

The products can be precipitated from the aqueous mixture by the addition thereto of an and a water miscible solvent, as for example acetone,/isopropanol ■and the ijLks The precipitate can then be separated by filtration and dried with care at room temperature as excessive temperatures over extended periods of time may destroy the product. The dried product is a water dispersible material capable of forming a thickened dispersion. Alternative methods for the recovery of a dried water dispersible material, such as spray or freeze drying, may also be used. Solvent precipitation may be advantageous if speed of separation is desired. However, spray or freeze drying is less likely to affect adversely a protein product.

The dried products are water dispersible materials capable of forming thickened dispersions which are useful as thickening, emulsifying, and foam stabilizing agents, particularly in the area of foods. These products of the process also find use in non-food areas where foam stabilizing or suspending properties are required.

Suitable alkylene glycol alginates for use in the process of the present invention are prepared by reacting alginic acid with alkylene oxides. These products are described by H. Maas in "Alginsaure and Alginate," SCT Publ.

Co., Heidelberg, 1959, pages 126-130. Particularly advantageous are the reaction products of alginic acid with 1.2-epoxides Examples of such products include ethylene glycol alginate, trimethylene glycol alginate, propylene glycol alginate (prepared from 1.2-propylene oxide and alginic butylene glycol alginate (prepared from 1.2-butylene oxide and alginic acid), isobutylene glycol alginate (prepared from 1.2-isobutylene oxide and alginic acid) or pentylene glycol alginate (prepared from 1.2-pentylene oxide and alginic acid) and mixtures thereof. The aforementioned esters are also described in Ind. Eng. Cheat. 3* 073 (¾ 951 ). Propylene glycol alginate or alginic aoid propylene glycol ester is especially useful in the preparation of additives for food uses since propylene glycol alginate is generally recognized as safe for use in foods.

The alkylene glycol alginates vhich may be used in the practice of the present invention in general have a degree of esterification of at least 25 € the degree of esterification may be less than 25$.

Conveniently, the degree of esterification of these alginates is from 25$ to 95 and is at least 30$. Preferably the degree of esterification ranges from at least 30$ to 90$ preferably 50$ to 90$ and most preferably ranges from 80$ to 90$ of the carbozyl groups. The remainder of the carboxyl groups are generally partially neutralized with a base.

Proteins vhich have been found to be particularly useful in preparing the water dispersible stabilized reaction products of the present invention are proteins vhich are soluble or dispersible in water at a temperature of 30°C or below. Bjt tills definition it Is Intended to exclude proteins which are only soluble or dispersible o in water at temperatures above 30 C such as gelatin. Examples of proteins which may be used in the invention include milk proteins suoh as those from whole milk or skim milk and derived milk proteins $i.e. proteins derived from milk by chemical reaotlon) such as cheese wheyI both acid and sweet, from processes for preparing cheeses such as cottage* cheddar and mozzarella, cheese, in various forms such as raw whey, dried whey, demineralized whey, concentrated and/or whey,—derod.negal3.zed whey?—oonoontratod and/or«-pai Llally delactosed whey protein as, for example, the material prepared by the process taught in U.S. Patent 3,547,900, as well as sodium caseinate, plant protein such as oil seed proteins illustrated by soy protein and soy whey, hydrolyaed vogotablo and hydro!Jy zed vegetable protein, protein, plant protein from corn, wheat or barley,/ fish protein, egg albumen, blood protein, and single cell protein such as yeast. As long as the protein is dispersible in water at temperatures of 30°C. or below, it is considered useful ..in the practice of this invention.

In the context of this invention, a single protein source is not required. Mixtures of two or more proteins can be reacted with the alkylene . glycol alginate.

When the water dispersible stabilized reaction product is dispersed in water it has been found that the clarity of . the dispersion can vary with the type of protein used.

Albuminoid type protein, in general, and whey protein, in particular, provide clearer solutions.

Generally, the properties of stabilized reaction products of protein and' alkylene glycol alginate prepared in accordance with the method of the present invention vary with the nature of the reactants, the reaction conditions and the composition of the initial mixture of reactants. The conditions necessary to produce water dispersible stabilized reaction products vary within different reaction systems. The conditions which affect the process and which must be controlled are the concentration of the reactants, the weight ratio of reactants (alkylene glycol alginate and protein) , the temperature, the tine during which the ctatoriale ere reacted at alkaline pB, tle pH, he quantity of alkali added, and the method of alkali addition.

Te process ie carried out in an aqueoue taixture. The initial concentrations of the protein and the alkylene glycol alginate at any given protein to alginate ratio must he adjusted suoh that the reaction between the protein and the alkylene glycol alginate occurs under the conditions of reaction when the aqueous mixture is at a reaotive alkaline pB. It hse been found that If tits concentration of the reaotants present in the mixture is too low, no reaction will occur on treatment with alkali. Conversely* the vieeoalty of the reaction product can be increased very rapidly to a point where an insoluble nondispersible gelatinous type of reaction product is created if tits concentration of the reaotants is too high for the reaction conditions* Generally, protein concentrations of from 0.5 to 5% by weight based on the total weight of the aqueous mixture of the protein, tits alkalene glycol alginate and the water«are preferred.

The concentration of the alkylene glycol alginates is usually limited by the practical consideration of handling and mixing viscous solutions of these compositions. Aqueous mixtures containing from 0.2J& to t¾6 by weight of alkylene glycol alginate may be used but it is preferred to utilise aqueous mixtures containing from 0.25$ to 4$ by weight of alkylsne glycol alginate based on its total weight of the protein, the alkylene glycol alginate and the water.

The most suitable concentration of reaotants for the method of the present invention varies for any given system but will generally be over a eoapara vely narrow concentration range* The weight ratio of protein to alginate which may be used in the process of the present invention varies from 50x1 to 1:5. Preferably weight ratios of from 20:1 to 1 J5, and more preferably from 20:1 to 113 are utilized. The most preferred weight ratio for a whey protein and propylene glycol alginate system ranges between 10:1 to 1:3* In general, as the ratio of protein to alginate varies, so do the properties of the stabilized reaction product which is prepared. For example, if the ratio of protein to alginate is increased, the viscosity of a dispersion of the stabllzed reaction product can decrease. Furthermore, when a high weight ratio protein:alkylene glycol alginate stabilized reaction product is precipitated by the addition thereof to a water miscible solvent, for example acetone, the precipitation stabilized reaction product can become more finely divided and difficult to separate and recover.

The temperature at which the protein and alkylene glycol alginate are reacted together In aqueous mixture can be from the o freezing point of the aqueous mixture of reaotants up to 50 C and preferably from 5°C to 25°C, and more desirably from 16-20°C. It has been found that the temperature of reaction employed is related to the concentration of the reactante. Increasing the temperature of the reaction tends to inhibit the reaction between the reaotants at low concentrations i.e., 1 or less. However, at higher concentrations of protein, i.e. above preferably 5-10 , at a 111, protein to alginate, ratio, temperatures of 20 to 50°C preferably 35 to 40°C can be effectively used. Lowering the temperature of the aqueous mixture of reaotants produces an advantageous effect on the extent of the desired reaction, particularly on aqueous mixtures of reaotants having protein concentrations of less than \ At temperatures in the range of freezing point to 10°C preferably 0°»-100C, reaction products which are water disperslble can be formed from mixtures containing 0.5 protein by weight at a 1)1 ratio of protein.

Accordingly/ temperatures from the freezing point of the aqeuoua mixtures of reactants to a temperature up to 50°C can be employed herein, subject to the limiting effects of concentration as established above.

The first step of the method of the present invention requires the reaction of an aqueous mixture of a protein with an alkylene glycol alginate at a reactive pH of at least 9.5. There are various methods for accomplishing this result. One can mix the protein and the alkylene glyco r '.alginate together in an aqueous mixture and rapidly add thereto a sufficient quantity of alkali to bring the pH of the entire mixture into the reaction range. Likewise, one can prepare an aqueous mixture of the alkali with protein and add a sufficient quantity of alkylene glycol alginate solution to that mixture provided that care Is taken to avoid undue damage to the protein by the alkali. Aqueous solutions of protein, alkylene glycol alginate and alkali can be brought together at one time in a mixing apparatus to form the reaction mixture.

Since the alkylene glycol alginate readily hydrolyzes under alkaline conditions, procedures should be avoided which tend to leave the alkylene glycol alginate in contact with the alkali under conditions insufficient for reaction. One such set of conditions might be to prepare a mixture of alkylene glycol alginate with alkali and after standing add that material to protein. It has also been determined that slow addition of alkali to a mixture of protein and alkylene glycol alginate will tend to hydrolyze the alkylene glycol alginate rather than provide the reaction of the alkylene glycol alginate with the protein* Again, for this reason, addition should be rapid* In general, the minimum reactive pH is approximately 9,5, It has been found that the optimum reactive pH will vary from 9,5 to 11.5 depending upon protein type, concentration, ratio of reactants and temperature.

Most reactions within the preferred concentration ranges occur at a pH of from 10 to 11 and preferably from 10.2 to 10.8. Higher pH's within the preferred range tend to increase the rate at which a thickened reaction mixture is formed. used herein, the term "reactive pH" denotes a pH at which a reaction product will form for a particular reaction mixture.

The aqueous mixture of reactants is conveniently brought to an alkaline condition by the use of a sufficient quantity of alkali* Alkalis are defined, for purposes of this invention, as alkali metal carbonates and hydroxides. Preferred alkalis are sodium carbonate and sodiumhydroxide, potassium carbonate, potassium hydroxide, and mixtures thereof. The alkali may conveniently be added as an aqueous solution.

Generally, the use of carbonate is preferable- to hydroxide because the hydroxide may cause localized high pH before full mixing can be achieved. Localization of high pH can partially destroy the alkylene glycol alginate.

In operation of the process it is necessary to determine the amount of alkali required to bring the pH of the aqueous mixture of unreacted protein and unreacted alkylene glycol alginate to the reactive pH above 9.5. For most protein systems, a reactive pH within the range of 10.2-10.8 has generally been found to be most effective. The amount of alkali required to raise a small measured portion of the aqueous mixture of unreacted protein and unreacted alkylene glycol alginate to a pH in the range of 10.2-10.8 is determined separately. The amount of alkali required is then proportioned to the amount of aqueous mixture of reactants to be reacted.

Small adjustments in the amount of alkali can be made to obtain the optimum pH for any particular protein, concentration of reactants, temperature and protein to alkylene glycol ratio in the mixture. In general, a higher pH within the range provides a faster reaction.

The amount of alkali required to bring the aqueous mixture of reactants to the required pH is primarily dependent upon the particular protein and its concentration in the aqueous mixture.

Further, the amount of alkali needed to be added to the aqueous mixture of reactants varies slightly with different systems but generally this quantity is slightly above the quantity required to produce, soft or thickened dispersions. If quantities of alkali below that required to bring the aqueous mixture of reactants to the reactive pH are used, no thickening of the aqueous mixture of reactants occurs.

For an isolated whey protein-propylene glycol alginate system, the pH is generally raised to at least 9.5 before the thickening reaction occurs. Preferably the reaction is from †0 carried out at a pH .between- 10.2 and.10.8.

Once the amount of alkali required to bring the aqueous mixture of reactants to the required pH has been determined, the process can be carried out by bringing the protein and alkylene glycol alginate and alkali together in an aqueous mixture.

In carrying out the method of the invention, it is desirable that the two reactants be brought together in aqueous admixture only at a sufficiently high pH to effect reaction. Since the alkylene glycol alginate is readily hydrolyzed by alkali, slow addition of alkali will destroy the alkylene glycol alginate so that the alkylene glycol alginate will not be available for reaction with protein at the reactive pH above 9.5. Rapid addition of the alkali to the aqueous mixture of reactants of the protein and alkylene glycol alginate generally avoids this hydrolysis problem.

Other methods such as rapid mixing of all ingredients in a mixing head can also overcome the problem.

After formation of the thickened reaction mixture under alkaline conditions , the reaction must, of necessity, be 7.or terminated by neutralizing the system to a pH of/below approximately ·? since the reaction proceeds as long as alkaline conditions are maintained. Failure to neutralize the reaction mixture while the reaction product is still in an aqueous dispersible state can result in either the formation of a product which is no longer water dispersible (a water insoluble material) or the reaction product is sufficiently destroyed to form a low viscosity liquid. Stabilization of the reaction product is accomplished by terminating the reaction, usually by neutralization. Neutralization is most and then adding acid to the reaction mixture to adjust the 7 Qr pH to/foglow .7». It is preferable that the reaction, mixture be diluted prior to acidification so that rapid, homogenous neutralization is realized. Acidification and dilution can be effected simultaneously if a sufficiently dilute acid is utilized for neutralization.

Thus, the period of time during which the aqueous mixture of reactants is reacted at an alkaline pH is also a factor which can affect the properties of the product obtained. The reaction time, therefore, can be defined as the period of time at which the aqueous mixture of protein and alkylene glycol alginate are maintained at a reactive pH before the neutralization of the mixture. In practice, there is generally a time lag between elevation of pH and onset of thickening. The time" lag depends on the type and concentration of reactants, the temperature and the pH.

Reaction times as short as several seconds to as long as 20 minutes have been observed. It is, however, preferred to adjust the pH, concentration, protein: alginate ratio and temperature to provide reaction times of from about ■ 15 seconds to 20 minutes and most preferably from 30 seconds to 5 minutes, but it must be kept in mind that the reaction time for a given system is dependent on all of the variables of pH, concentrations, and specific reactants as specified above. This time can be easily determined for any given system with a minimum of experimentation.

During the reaction, the viscosity of the reaction mixture increases to a maximum, then slowly decreases as further reaction occurs. As stated hereinbefore, the decrease If neutralization and acidification take place before the onset of thickening or after extensive degradation has occurred, the resulting dispersible product will be one having low viscosity when dispersed in water. reaction acidification of the reaction mixture after the viscosity of the reaction mixture as measured by a Brookfield viscometer has increased to at least about four times the viscosity of an aqueous mixture of unreacted protein and unreacted alkylene glycol alginate. More preferably, the viscosity of the aqueous reaction mixture as measured b a Brookfield viscometer increases taore thaa from 5 to 500 times the viscosity of the unreacted aqueous mixture before neutralization though thousand fold increases in viscosity have been observed.

It is understood" that the viscosity increase as used herein refers to an increase in viscosity caused by reaction of the protein with the alkylene glycol alginate and is not due merely to protein thickening caused by the increase in pH. Certain native proteins in aqueous dispersions exhibit increases in viscosity on increase in pH. This increase in viscosity is reversible in that it can return to the original state when the pH is decreased.

At high protein concentrations and low protein to alkylene glycol alginate ratios by weight, the reaction product which forms becomes increasingly non-dispersible as the reaction time at the reactive pH is increased. When the amount. of non-dispersible material becomes substantial, the reaction product loses its functionality. Under these conditions it is necessary to reduce the pH of the reaction non-dispersible material appears in the reaction product.

If the reaction product is permitted to remain at the reactive pH over a period of several hours, the reaction product will lose its original thickening qualities and revert to a liquid of low viscosity. The low viscosity liquid is miscible with water but has Lost its thickening functionality and its utility within the scope of this invention.

For these reasons the maximum period of reaction time is that which will permit the reaction mixture to maintain useful functional properties.

For a 1:1 whey protein:propylene glycol alginate system, a reaction time of from 10 to 15 minutes has been found to be suitable. In general, to form a reaction mixture having maximum viscosity, a reaction time of from about 30 seconds to five minutes before neutralization by acidification of the reaction mixture (stabilization of the reaction product). The exact reaction time for any given system can easily be ascertained by one skilled in the art.

It is essential that the pH of the reaction mixture be 7 or adjusted to /below jibxut 7- to terminate the reaction and to prevent deterioration of the reaction product (stabilization) . The pH is usually not adjusted to below abou 3 since extremely low pH can affect the properties of the stabilized reaction product.

Suitable acids for the acidification acid, acetic acid, citric acid, sulphuric acid, phosphoric mixtures thereof acid, and the like-* Other acids may also be suitable, dependent, of course, on the final use of the product. Food grade acids are preferable in preparing food grade products.

The reaction between the protein and alkylene glycol alginate is terminated when the pH of the reaction mixture is adjusted to below 7. However, the final pH to which the reaction mixture is adjusted is important in determining the dispersibility of the stabilized reaction product after drying. The acidification pH which provides optimum dispersibility varies with the particular system and/usually lieo ■ to preferably from 3.5 to 5.5 between 3-aa4-7/. For example, for a 1:1 whey protein :propylene glycol alginate reaction mixture where sodium carbonate was used as the alkali, the pH will generally be adjusted to within the range of from about- 3.5 to about 6.0 and preferably about 4.5.

It is contemplated that the neutralized reaction mixture ' or can be treated by methods known m the art, such as filtration/ contact with activated carbon and the like to improve color or clarity of the stabilized reaction product.

The stabilized reaction product can be used as formed or recovered from the aqueous neutralized reaction mixture.

Recovery means such as solvent precipitation or vacuum drying have been found suitable for recovering a dry dispersible product capable of forming a thickened dispersion as disclosed in detail above.

While applicants do not intend to be bound by this explanation, the mechanism of the reaction between the protein and the alkylene glycol alginate is believed to be one of nucleophilic attack of the amino group, which is present in the residue of the protein, on the ester carbonyl group of the alkylene glycol alginate thus forming amide linkages between the component molecules. Thus, it is . . ■ ' · " ... · ^; believed that the chemical modification of a protein with alginate residues forms amide linkages which allow for the formation of the product. However, it is not intended to limit the invention to any specific theory since the exact theory or mechanism for the formation of the product is not known with certainty and the above is postulated only to facilitate an understanding of the invention. Other theories may explain the phenomenon equally well or better.

The present invention also includes within its scope a water dispersible reaction product of a water dispersible protein and an alkylene glycol alginate arid a dry water dispersible reaction product of a water dispersible protein and an alkylene glycol alginate capable of forming a thickened dispersion when admixed with water.

Heating of an aqueous dispersion brings about additional thickening if the concentration of the reaction product is high enough in the disperion. A one percent/concentration of a reaction product having a 1:1 whey protein/propylene glycol alginate weight ratio can be thickened by this treatment. Reaction products prepared from higher protein/ alkylene glycol alginate weight ratio mixtures require higher concentrations to achieve an increase in viscosity by heating. If the concentration of the dispersion material is too low, a decrease in viscosity results. Heating an aqueous of at least 75 dispersion of stabilized reaction product to a temperature/ conveniently to a temperature from in the range of from- abo¾ffe/75°C . to about 100°C, and preferably about 90 °C. is usually sufficient to bring about the change in viscosity. It is to be understood that the thickening effect due to heating can be observed in connection with the stabilized reaction mixture itself, or on dispersions of The following examples are illustrative of the present invention. In these examples and throughout this specification, and ratios all parts and percentages/are by weight unless otherwise specified.

£ Example 1 Preparation of 1:1 whey protein-propylene glycol alginate stabilized reaction product. 15.75 grams dry weight of propylene glycol alginate having a degree of esterification of 83% and available from Alginate Industries , Ltd. , 22 Henrietta Street, London, Trade Mark England, as Manucol Ester, (trademark) , E/RK were dissolved in water to give 1400 grams of an aqueous mixture having a propylene glycol alginate concentration of 1.125% by weight. 29.17 grams of a commercially available modified whey protein containing 54% whey protein, 27% lactose, and 3% moisture, obtainable from Stauffer Chemical Company , Westport, Connecticut, Trade Mark U.S.A., under the tradomar-k ENRPRO 50, were dissolved in 370.8 grams of water to give 400 grams of an aqueous mixture having a protein concentration of 3.94% by weight.

The two mixtures were then thoroughly mixed until homogeneous and the temperature was adjusted to 19+0.5 °C. to give a mixture having the composition of 0.875% whey protein and 0.875% propylene glycol alginate.

With rapid stirring, 72.9 milliliters of a one molar sodium carbonate solution were added to the protein and ester mixture and after one minute, thickening of the mixture occurred. After an additional four minutes, the thickened reaction mixture was diluted with 1800 grams of water and the mixture was stirred until homogeneous. The excess ·■;. ■ - . ■ ' ■ . .· _ " / Γ alkali was then neutralized approximately 10 minutes after the alkali addition with 2 normal hydrochloric acid. To reduce the pH to 4.5, approximately 72 milliliters of 2 normal hydrochloric acid were required.

The reaction product was recovered by pouring the acidified reaction mixture into approximately 5 volumes of acetone. The precipitate was allowed to harden, separated by filtration, pressed, washed with several portions of fresh acetone then air dried at room temperature to give a solid with a dry matter content of 80-90%.

A sample of this material was added to water to give a dispersion of concentration of 1% (on a dry weight basis) and the slurry stirred mechanically until complete dispersion occurred. The resulting thickened dispersion had a pH of approximately 5.3, and a viscosity of about 3500 centipoises as measured on' a Brookfield LVT Viscometer, (speed 60 revolutions per minute, spindle 4, temperature 20°C) .

Heating of this dispersion to 90°C. followed by cooling to 20 °C. resulted in a further increase in the viscosity of the dispersion.

Example 2 Preparation of 2 :1 whey protein/propylene glycol alginate stabilized reaction product. The procedure of Example 1 was followed using 300 grams of an aqueous solution containing 0.67% propylene glycol alginate (Manucol Ester E/RK as defined in Example 1) on a dry matter basis and 1.33% whey protein (ENRPRO 50 as in Example 1). 15 milliliters of 2 normal sodium carbonate solution were added with stirring. After five to ten minutes the thickened reaction mixture obtained was diluted with 250 grams of water and acidified to pH 4.5 with approximately 16.5 milliliters of 2 normal hydrochloric acid. The acidified reaction mixture was then made up to 600 grams with water to give a reaction product concentration of 1% by weight.

Example 3 Preparation of 5;1 whey protein/propylene glycol . alginate stabilized reaction product.

The procedure of Examples 1 and 2 was followed using 300 grams of an aqueous mixture containing 0.458% propylene glycol alginate ( anucol Ester E/ K as defined in Example 1) on a dry matter basis and 2.29% whey protein (ENRPRO 50 as in Example 1). 21.7 milliliters of 2 normal sodium carbonate solution were added with stirring. After five to ten minutes, 25 milliliters of water were added and the reaction mixture acidified to pH 5.0 with approximately 24 milliliters of 2 normal hydrochloric acid.

The acidified reaction mixture was then made up to 412.5 grams with water to give a reaction product concentration of 2.0% by weight.

Examples 4 to 11 The general procedure of Examples 1 to 3 was followed and Table I gives details of the reactants and other conditions of the reaction for Examples 1 to 11.

In each case the protein and propylene glycol alginate were dissolved separately, then the mixtures were mixed to give an aqueous mixture of reactants of the required composition.

The temperature of the aqueous mixture of reactants was then adjusted to 19±0.5°C. The appropriate quantity of alkali was added to raise the pH to above 9.5 with efficient stirring to prevent localized build-up of excessively high pH. After five to ten minutes the reaction mixture thickened to at least 4 times the viscosity of the aqueous mixture of unreacted protein and unreacted alkylene glycol alginate. The reaction mixture obtained was diluted with approximately its own weight of water and, acidified with the appropriate quantity of acid to the pH indicated in Table I.

The reaction product was precipitated by pouring the acidified reaction mixture into acetone/ and collecting the precipitate which was then washed with solvent and dried at room temperature .

The proteins used and stated in Table I are listed below with details of their actual protein contents on a dry matter basis.

ENRPRO 50 Modified Whey Solids 54% protein, 27?- lactose, (Stauffer Chemical Co.) 3% moisture.

Arkasoy 50 Soy Isolate 50% protein. Insoluble in water at natural pH of 6.5 (1% solution).

(British Arkady Co., Ltd.

Sodium Caseinate 77% protein, 9% moisture (Laing National) Egg Albumen 75% protein Single Cell Protein (Experimental Yeast Product) 82% protein In Table I the concentration of protein refers to the actual percent level of protein in the mixture and not the level of protein-containing material. The propylene glycol The propylene glycol alginates used in Table I were obtained from Alginate Industries, Ltd. of London and had degrees of esterification and percentage dry solids as follows : PROPYLENE GLYCOL ALGINATE Degree of Dry Viscosity (P.G.A) . ' Esterifica- Solids% (cps) tion% Manucol Ester E/R 83 83 120 Manucol Ester E/RE 84 87 100 Manucol Ester E/PL 75 86 200 Manucol Ester M 60 83 400 Note. Viscosity is measured on Brookfield L.V.T. viscometer at 60 rpm.

T = 20 °C. using a 1% solution except in the case of Manucol Ester E/RE where a 2% solution is used.

TABLE I Example Protein Protein P.G.A. P.G.A. Ratio Volume Appro Concen- Type Concen- Protein 2 Normal Volum tration tration P.G.A. Sodium Hydro % % Carbonate Chlor Solution/ Acid/ lOOg. React Reaction Mixtu Mixture (ml (ml) 1 Mod. Whey 0.875 E/R 0.875 1:1 4.1 4.2 Solids* 2 Mod. Whey 1.33 E/RK 0.67 2:1 5.0 5.5 Solids* 3 Mod. Whey 2.29 E/RK 0.458 5:1 7.2 8.0 Solids* 4 Mod. Whey 1.33 E/RE 0.67 2:1 6.7 7.0 Solids* 5 Mod. Whey 2.292 E/RE 0.458 5:1 11.7 11.9 Solids* 6 Mod. Whey 0.875 E/PL 0.875 1:1 6.50 6.4 Solids* · 7 Mod. Whey 0.875 M 0.875 1:1 6.67 6.5 Solids* 8 Sodium 0.625 E/RE 0.625 1:1 3.33 3.3 Caseinate 9 Single 0.75 E/RE 0.75 1:1 3.33 2.9 Cell Protein TABLE I Example Protein Protein P.G.A, P.G.A. Ratio Volume Appro Concen- Type ConcenProtein: 2 Normal Volum tration tration P.G.A. Sodium Hydro Carbonate Chlor Solution/ Acid/ lOOg. React Reaction Mixtu Mixture (ml (ml) 10 Soya 1.5 E/RE 1.5 1:1 5.0 4.6 Protein (Arkasoy 50) 11 Egg 1.75 E/RE 1.75 1:1 4.84 3.8 * ENRPRO 50 The viscosities (Brookfield) were observed at the concentrati and 20°C. for the compositions listed, examples 1 to 11 inclu The viscosities marked ** in parenthesis are after heating an solution, and show typical increases for this treatment.

The reaction products prepared in examples 1 to 11 were dispersed in water and it was found that the viscosities of the dispersions varied depending on the protein used. Thus reaction products of 1:1 protein: ester ratio using whey or sodium caseinate gave by far the highest viscosities, while the reaction product from protein soy had the lowest viscosity, although this may be partly due to the high proportion of insoluble components present in the soy protein employed.

In almost every case, viscosity further increased after the dispersions of reaction products were heated to 90 °C. possibly as a result of partial denaturation of the protein.

Example 12 Preparation of 10:1 Whey Protein-Propylene Glycol Alginate Stabilized Reaction Mixture The procedure of the preceding examples was followed. 300 grams of an aqueous mixture containing 0.5% (1.5 grams) of propylene glycol alginate (Manucol Ester E/RK as defined in Example 1) and 5% (15 grams) of whey protein (27.78 grams of ENRPRO 50 as defined in example 1, were alkalized with 47 milliliters of 2 normal sodium carbonate solution. After five to ten minutes the thickened reaction mixture obtained was diluted with water and the pH adjusted with 2 normal hydrochloric acid to below 7 to give a thickened stabilized dispersion of reaction product. & 8 Example 13 Preparation of 50 ; 1 Whey Protein-Propylene Glycol Alginate Stabilized Reaction Mixture The procedure of the preceding examples was followed. 300 grams of an aqueous mixture of reactants containing 0.3% (0.9 grams) propylene glycol alginate (Manucol Ester E/R as defined in example 1) on a dry matter basis and 15% (45 grams) whey protein (83.3 grams ENRPRO 50 as defined in example 1) were alkalized with 18 milliliters of 2 normal sodium hydroxide. After five to ten minutes the thickened reaction mixture was diluted with water as required and the pH adjusted with 2 normal hydrochloric acid to below 7 to give a thickened, highly viscous dispersion of reaction product.

Example 14 Effect of Amount of Alkali on Reaction Product Formation Two 200 milliliter samples of aqueous mixtures of reactants containing 1.25% by weight propylene glycol alginate having a degree of esterification of about 83% and 1.25% by weight whey protein (ENRPRO 50 as defined in example 1) were prepared. The viscosity of the mixtures was 35 centipoises as measured on a Brookfield viscometer.

To the first sample were added 17 milliliters of 1 molar sodium carbonate and 23 milliliters of water in about 5 seconds. Final pH of the solutions was 10.7. The viscosity of the alkaline solution after 2 minutes was 30 centipoises. No thickenening of the reaction mixture was observed.

To the second sample was added 40 milliliters of 1 molar sodium carbonate in about five seconds. The resultant pH was about 10.9 and the viscosity after two minutes was greater than 500 centipoises. Thickening of the reaction mixture was observed. Temperature of reaction was 20 °C.

This example is to be contrasted with Example 1, and illustrates the influence that variation in the nature of the reactants have on the reaction product.

Example 15 Effect of the rate of Alkali Addition on Reaction Product Formation To a 200 milliliter sample of propylene glycol alginate/ whey protein prepared as in the preceding example 14, were added a total of 40 milliliters of 1 molar sodium carbonate in successive small steps over a period of five minutes.

The final pH was 10.9. The viscosity two minutes after completion of carbonate addition was 30 centipoises. No thickening of the reaction mixture was observed. Temperature of the reaction was 20 °C.

Example 16 Effect of Concentration of Reactants on Reaction Product Formation Two propylene glycol alginate/whey protein aqueous mixtures of reactants were prepared as in example 14 above containing the following amounts of reactants: Reaction Mixture A B PGA 1.2.5% by weight 1.5% by weight ^ . · To each aqueous mixture of reactants were added 17 milliliters of a 1 molar sodium carbonate solution in five seconds . The following results were obtained: Reaction Mixture Initial Viscosity pH Pinal Viscosity A (1.25% 35 cps 10.7 30 cps B (1.5%) 42 cps 10.6 500 cps At a 1:1 reactant ratio and concentration of 1.25% no thickening of the reaction mixture was observed but at a 1:1 reactant ratio and concentration of 1.5% thickening of the reaction mixture was observed. Temperature of reaction mixture was 20°C.

Example 17 Effect on Reaction Product Formation of Adding Alkali to Protein First A. A 100 milliliter mixture of 1.6% propylene glycol alginate as defined in example 1 and a 100 milliliter mixture of 1.6% whey protein (ENRPRO 50 as defined in example 1) were prepared. 20 milliliters of a 1 molar sodium carbonate solution were added to the whey protein mixture. After about five seconds, this alkalized whey protein solution was then added to the propylene glycol alginate solution. After 5 seconds thickening of the reaction mixture occurred.

Part A The above "^ρ1 Q was repeated but the alkalized whey protein mixture was allowed to stand for 15 minutes before being added to the propylene glycol alginate mixture. No increase in viscosity (no reaction) was observed. Reaction temperatures for both examples was 20 °C.

Example 18 Reaction Product Formation at Elevated Temperature A 5% propylene glycol alginate ester mixture (Manucol Ester E/RE - low viscosity as defined in example 4) was mixed with a 10% ENRPRO .50 (as defined in example 1) (approximately 5% whey protein) mixture to provide a mixture having a 1:1 weight ratio of alginate to protein. The prereaction viscosity of the mixture was 215 centipoises. Sufficient sodium carbonate solution was added to bring the pH within the range of 10 to 11. The reaction temperature was 40°C.

The viscosity of the alkaline reaction mixture was 4,800 centipoises. After dilution of the reaction mixture with an equal volume of water, the reaction mixture was neutralized with acid giving a mixture having a viscosity of 6,200 centipoises. The reaction product was precipitated with acetone and moderately dried with care. The dried reaction product reconstituted in water at 2% concentration gives a dispersion of a viscosity of 1500 centipoises. The dried reaction product contains 37% protein based on Kjeldahl nitrogen, and 14% moisture.

Example 19 Reaction Product Formation at Elevated Temperature A 7% whey protein (14% ENRPRO 50 as defined in example 1) aqueous mixture was mixed with a 7% propylene glycol alginate aqueous mixture (Manucol Ester E/RE as defined in example 4) to provide a mixture of reactants having a weight ratio of 1:1 protein to propylene glycol alginate. The prereaction viscosity of the mixture of reactants was 380 centipoises. After elevating the pH within the range of 10- a viscosity of 5,000 centipoises. The reaction temperature was 50 °C. The thickened reaction mixture was diluted with an equal volume of water with a sufficient quantity of acid therein to neutralize the pH to below pH 7. The viscosity of the neutralized reaction mixture obtained was 2,300 centipoises.

The reaction product was separated by acetone precipitation and dried. i?ossibly because of a defect in the precipitation technique, a 2% solution of the reaction product in water provided a composition with a viscosity of 115 centipoises.

The dried reaction product contained 35% protein based on Kjeldahl nitrogen and 16% moisture.

Example 20 Reaction Product Formation at Lower Temperatures (5°C) A 1.0% whey protein mixture (approximately 2.0% ENRPRO 50 as defined in example 1) is mixed with a 1.0% propylene glycol alginate mixture (Manucol Ester E/RE as defined in example 4) at a weight ratio of 1:1 protein to alginate.

The prereaction viscosity was 22 centipoises. Sufficient sodium carbonate solution was added to raise the pH within the range of 10-11. The temperature of reaction was 5°C.

After the reaction mixture thickened, the viscosity of the reaction mixture formed was 4,200 centipoises. The reaction mixture was diluted with an equal volume of water to provide a diluted reaction mixture having a viscosity of 400 centipoises After neutralization of the diluted reaction mixture with acid, the viscosity of the neutralized reaction mixture was 500 centipoises. The reaction product was precipitated with acetone and dried. Upon redispersion at 2% concentration in Γ In accordance with the method of the preceeding examples, 'reaction mixtures were obtained at 20°C. using: a) 1:5 weight ratio whey protein to propylene glycol alginate (0.5% whey protein solution: 2.5 propylene glycol alginate solution) ; b) skimmed milk as a protein source; c) propylene glycol alginate having a degree of esterification of 35%.

All the foregoing thickened under alkaline conditions at 20 °C. The products were not separated.

Example 21 Reaction Product Formation Using Liquid Whey Liquid whey estimated to have a protein content of 0.7% protein was mixed with sufficient propylene glycol alginate to provide 1.4,% propylene glycol alginate (Manucol Ester E/RE as defined in example 4) in the liquid whey thus providing a mixture of reactants having a weight ratio of 1:2 protein to propylene glycol alginate at 10 °C. The prereaction viscosity was 83 centipoises. After alkalizing with sodium carbonate to between pH 10 and 11, the viscosity rose to 44,000 centipoises. The reaction mixture so formed was diluted with an equal volume of water giving a diluted reaction mixture with a viscosity of 3,000 centipoises.

After neutralization with acid to a pH below 7, the viscosity was 900 centipoises. The product was isolated by the addition of acetone and dried to a moisture content of 13%. A 2% reconstituted dispersion provided a thickened dispersion with a viscosity of 3,800 centipoises.

\, Example 22 Use of Freeze Drying for Reaction Product Isolation 50 Milliliters of a 1% propylene glycol alginate mixture were prepared by dissolving 0.5 grams propylene glycol alginate (Manucol Ester E/RE, 85.7% esterification as defined in example 4) in 50 milliliters of water. To this mixture was added 2.5 grams of ENRPRO 50, as defined in example 1, (approximately 1.25 grams whey protein) and the mixture was allowed to come to a reaction temperature of 18 °C. 7.5 milliliters of 2 normal sodium carbonate solution were then added with stirring to bring the pH to about 10.3. After 55 seconds, 25 milliliters of water were added to the thickened reaction mixture which formed. After five seconds, the diluted reaction mixture was neutralized (acidified) by adding 8.5 milliliters of 2 normal hydrochloric acid with stirring. The pH of the acidified reaction mixture was checked on a pH meter and found to be 6.0. An aliquot of the reaction mixture disperses in water. The remainder of the sample was freeze dried overnight. The freeze dried reaction product was redispersible in water.

Example 23 Effect of Alkaline Reaction Time on Reaction Product Water Dispersibility In order to determine whether reaction time under alkaline conditions had any effect on the properties of the final products obtained, the following comparative examples were run at 55 seconds, 2, 4, and. 6 minutes. 50 milliliter samples of a 1% propylene glycol alginate mixture were prepared by dissolving 0.5 grams propylene glycol alginate (Manucol Ester E/RE, 85.7% esterification, as defined in Example 4) in 50 milliliters of water. To this mixture Were added 5 grams of ENRPRO 50, as defined in example 1, (approximately 2.5 grams whey protein) and the mixture of reactants was allowed to come to a reaction temperature of 18 °C. 15 milliliters of a 2 normal sodium carbonate solution were then added with stirring to bring the pH to about 10.3. In less than 1 minute a thickened reaction mixture formed. After time periods of 55 seconds, 2 , 4, and 6 minutes, the thickened reaction mixture was neutralized by adding 32 milliliters of water and 17 milliliters of 2 normal hydrochloric acid with stirring. The pH of the acidified mixtures were checked on a pH meter and found to be below pH 7. The following results were obtained: Sample A B D Reaction 55 seconds 2 minutes 4 minutes 6 minutes Time Thickening 30-60 seconds 30 seconds 40 seconds 30-40 Appearance Seconds Time Final pH 5.85 4.6 4.6 Dispersi- Yes No No No bility in Water A portion of the reaction product of Sample A was freeze dried overnight. The freeze dried sample was also dispersible in water.

Example 24 Use of Potassium Carbonate as Alkali 50 milliliters of a 1% propylene glycol alginate mixture were prepared by dissolving 0.5 grams propylene glycol alginate (Manucol Ester E/RE, 85.7% esterification, as defined in example 4) in 50 milliliters of water. To this example 1, (approximately 0.75 grams whey protein) and the mixture of reactants was allowed to come to a reaction temperature of 18 °C. 9 milliliters of 2 normal aqueous potassium carbonate solution were then added with stirring to bring the pH to about 10.3. After 45 seconds, 30 milliliters of water were added to the thickened reaction mixture which appeared. After an additional five seconds the diluted reaction mixture was neutralized (acidified) by adding 9 milliliters of 2 normal hydrochloric acid with stirring.

The pH of the acidified reaction mixture was checked on a pH meter and found to be below 7. The reaction mixture was dispersible in water.

Example 25 Effect of Alkaline Reaction Time on the Water Dispersibility of the Reaction Mixture 50 milliliters of a 1% propylene glycol alginate mixture were prepared by dissolving 0.5 grams propylene glycol alginate (Manucol Ester E/RE, 85.7% esterification , as defined in Example 4) in 50 milliliters of water. To this mixture were added 5 grams of ENRPOR 50, as defined in Example 1 (2.5 grams whey protein) and the mixture of reactants was placed in a water bath and was allowed to come to a reaction temperature of 40°C. 15 milliliters of 2 normal sodium carbonate solution were then added with stirring to bring the pH to about 10.3. After 35 seconds, 32 milliliters of water were added to the thickened reaction mixture which appeared. After an additional 5 seconds, the reaction mixture so diluted was neutralized (acidified) by adding 17 milliliters of 2 normal hydrochloric acid with stirring.

The pH of the acidified mixture was checked on a pH meter and found to be below pH 7. The neutralized reaction mixture was dispersible in water.

A like sample was run using all of the preceeding conditions with the exception that the alkaline reaction was held for 50 seconds rather than the 35 seconds of the initial experiment. This sample which was reacted longer was insoluble and non-dispersible in water.

Example 26 Use of 1:1 Whey Protein-PGA Reaction Product in Salad Dressing A salad dressing using a 1:1 whey protein-PGA stabilized reaction product prepared in accordance with Example 1 as an emulsion stabilizer in place of a propylene glycol alginate stabilizer was prepared using the following ingredients: % (a) % (b) % (c) Salt 2.5 2.5 2.5 Seasoning 0.4 0.4 0.4 Sugar 9.7 9.7 9.45 Mustard 0.8 0.8 0.8 Coloring 0.1 0.1 0.1 Dried Egg Yolk 1.35 1.35 1.35 10% Vinegar 18.0 18.0 18.0 Corn Oil 27.0 27.0 27.0 Stabilized Protein/ PGA Reaction Product 0.5 0.5 PGA 0.5 Starch 4.5 4.5 4.5 Whey Protein 0.5 Water 35.15 35.15 34.90 100.00 100.00 100.00 " I - Method for Preparing Formulation A and C 1. Dry mix the sugar, mustard, salt, seasoning, starch and coloring and mix into the water and vinegar until a homogeneous mix is obtained. 2. Heat the mixture to 80-85°C. and hold for 10 minutes to gelatinize the starch. 3. Cool to 30 °C. or below and add 3/4 of the oil as a fine stream. Stir under high speed to form an emulsion. 4. Disperse the egg yolk and the protein/PGA reaction product or the PGA in the remainder of the oil and add to the mix described above. 5. Homogenize at 1700 psi (119 Kg/sq cm) to obtain a stable emulsion. The sample was placed in storage at 20°C.

II - Method, for Preparing Formulation B. 1. Predissolve the protein/PGA reaction product in the water of the formulation and then add thereto the dry ingredients listed in and in accordance with step 1 of Method I. 2. Perform steps 2, 3, 4, and 5 of Method I (except no protein/PGA reaction product added in Step 4) .

The following results were obtained: Sample A B C Method I II I Consistency Smooth Smooth Smooth Pourable Pourable Pourable Viscosity (cps) 7,000 9,400 10,200 The stabilized reaction product proved effective in stabilizing oil emulsions in salad dressings.

The water-dispersible reaction products prepared in accordance with the method of the present invention may be useful as thickening, emulsifying, foaming or binding agents.

Claims (10)

/ CLAIMS :

1. A method for preparing water dispersible reaction products of water dispersible proteins and alkylene glycol alginate which comprises: a) reacting a mixture of protein, which is dispersible in water at a temperature of 30°C or below, and alkylene glycol alginate dispersed in water, at a reactive pH as hereinbefore defined of at least 9.5 at a reaction temperature to obtain a reaction mixture containing a water dispersible reaction product, said reaction mixture having a viscosity increase of at least four times the viscosity of an aqueous mixture of unreacted water dispersible protein and unreacted alkylene glycol alginate as measured by a Brookfield viscometer, and b) adjusting the pH of the reaction mixture to 7 or below whereby a stabilized reaction product as hereinbefore defined of protein and an alkylene glycol alginate dispersed in water is obtained.

2. A method according to claim 1 wherein said alkylene glycol alginate is selected from ethylene glycol alginate, trimethylene glycol alginate, propylene glycol alginate, butylene glycol alginate, isobutylene glycol alginate, pentylene glycol alginate and mixtures thereof.

3. A method according to claim 1 or claim 2 46844/2^., wherein said protein is utilized in a weight ratio to said alkylene glycol alginate of from 50:1 to 1:5 preferably from 20:1 to 1:3.

4. A method according to any one of claims 1 to 3 wherein said reactive pH is within the range of from 9.5 to 11.5, preferably from 10 to 11 and more preferably from 10.2 to 10.8.

5. A method according to any one of claims 1 to 4 wherein the reaction temperature at the reactive pH of at least 9.5 ranges from the freezing point of the aqueous mixture of reactants to 50°C, preferably from 5°C to 25°C and more preferably from 16 °C to 20°C.

6. A method according to any one of claims 1 to 5 wherein the time at the reactive pH ranges from 15 seconds to 20 minutes, preferably from 30 seconds to 5 minutes.

7. A method according to any one of claims 1 to 6 wherein the pH of the reaction mixture of step (a) of claim 1 is adjusted to a pH within the range of 3 to 7, preferably from 3.5 to 5.5.

8. A method according to any one of claims 1 to 7 wherein the reaction mixture of step (a) of claim 1 is diluted with water prior to adjusting the pH to 7 or below as required in step (b) of claim 1.

9. A water- dispersible reaction product of a protein and an alkylene glycol alginate whenever prepared by a method as claimed in any one of claims 1 to 8.

10. A method for preparing wate -dispersible reaction products of whey protein and propylene glycol alginate which comprises : a) reacting a mixture of whey protein and propylene glycol alginate dispersed in water at a reactive pH , as hereinbefore defined, of at least pH 9.5 and below 11 to obtain a water-dispersible reaction mixture, said whey protein being used in a weight ratio to said propylene glycol alginate within the range of from 20:1 to 1:3, said whey protein being used in a concentration of from 0.5% to 35% by weight, said propylene glycol alginate being used in an amount of from 0.2% to 6% by weight, weight said wioght percentages being based on the total weight of the mixture of reactants of the whey protein, the propylene glycol alginate and the water in which the two said ■p re vi PUB— mater i a Is are mixed, said water dispersible reaction mixture having a viscosity increase of at least 4 times the viscosity of an aqueous mixture of unreacted whey protein and unreacted propylene glycol alginate as measured by a Brookfield viscometer, and b) adjusting the pH of said reaction mixture within the range of from 3.5 to 5.5 whereby a stabilized reaction product dispersed in water is obtained.