CA1091653A - Protein/starch complex and a method of producing a protein/starch complex - Google Patents

Abstract

PROTEIN/STARCH COMPLEX

ABSTRACT OF THE DISCLOSURE
By heating starch with an aqueous dispersion of casein or caseinate at a temperature above the gelation temperature of the starch, a unique complex is formed.

Description

lg.~9~S3 BACKGROUND
When food~tuffs or foodstuff components are co~bined, the raw materials are destroyed and protein, carbohydrate, fat and spices recombine to form diferent products. Proteins and carbohydrate~ are used for their traditional functions. The most common carbohydrate for human consumption is ~tarch, which i8 u~ed as a thickener and as a binder in several foodstuffs. It lack~ certain functional properties, such aR foam and emulsion-stabili~ing properties and i~ limited in its utility.
Physi~al and chemical modification of ~tarch has been effected to modify its properties.
Starch combines with gluten to provide a product having the properties of bread. Starch i8 used to improve the properties of skim milk. According to Swedish patent specification No. 129,026, s~arch increases milX-protein foam stability. The amount and ratio o~ starch used for these purposes and the fact that the same effects are obtained with such ~ubstances as pulverized fruit seeds, pip~ and stones, kefir, kefir casein and lecithin indicate that the normal binding propertie~ of the starch are being utilized to obtain the desired effect. In order to utilize the properties o~ the milk protein, this must also be swollen by increa~ing the pH value.
According to Norwegian patent specification No.
67,483, starch i~ used in the production of a dry-milk protein product. F~om the process conditions and weight ratios of ingredients it is appreciated that normal swelling properties of the starch are responsible for improving the properties of the milk protein. A gelatinized ~tarch product is referred to. Souring of the milk seem~ to be a prerequisite for preparing the actual milk protein product.
Swmmary of the Invention Modified ~tarch products are prepared by binding starch from virtually any source with protein (casein or caseinate) to form complexe9. such complexes are prepared by heating starch with an aqueous dispersion o~ the protein at a temperature in excess of the starch-gelation temperature. The reaction time is naturally dependent upon the actual temperature employed and, to some extent, on the concentration and relative concentrations of reactants. The reaction time i8 ordinarily le~s than 1 minute to about 45 minutes and may even be extended further.
The modified starch i8 useful in substantially the same way as unmodified starch, but does not have the stickiness and gumminess properties of starch. In addition, it i8 useful for emulsion stabilization. The modified starch can further be prepared to various vi6cosities.
B~ief Description of the Drawings FIGS. 1 and 2 graphically depict the relation between viscosity and temperature.
FIGS. 3 to 6 graphically depict the relation between shearing force and shearing speed.
FIG. 7 graphically depicte the relation between viscosity and temperature.
FIG. 8 is a micrograph showing swelled corn ~tarch granules at 95C in 0.2 M NaCl.
FIG. 9 is a micrograph showing starch protein complexes and emptied granules when corn-starch and caseinate was heated to 95C in 0.2 M NaCl.
FIG. lb graphically depicts the effect of different starch-cabeinate ratio~ on the viscosity. ~_ - ~g~6s3 FIG. 11 graphically depict the effect of various salts on the vi~cosity.
Details Characteristic~ of the protein/starch co~plex are dependent upon the degree of complex formation and thus the ratio of protein to ~tarch, reaction time, xeaction temperature and ions in the reaction mixture. The nature of the modified starch i~ virtually independent of the form of casein of the source of starch employed. Naturally, the modified starch retains basic properties of the starch which i8 modified, but the nature of the modification is ~ubstantially the ~ame ~or each starch u~ed. The reaction is also substantially independent of pH.
Increasing the protein from virtually none to at least an amount (by weight) equal to that of starch decreases the thixotropy of the re~ulting modified starch and its ability to gel. By including ions (preferably polyvalent anions) in the reaction mixture, the ability to gel can be eliminated.
Although the reaction temperature must be at least that of the gelation temperature o~ the starch, the reaction is suitably conducted at any temperature from that lower limit.
The reaction time i8 ordinarily less than 1 minute to about 45 minutes and is dependent upon the reaction temperature. At lower temperatures the reaction time can be extended to an hour or even longer without any deleterious effect.
By varying the noted critical reaction parameters, the degree of complex formation and the functional properties of the resulting modified starch are controlled.

~ - 4 916S;3 The modification makes it possible to uge starch in ways and for purposes not previously possible, particularly where swelling, gelation and thixotropy were limiting or preclusionary factors. As compared with properties of employed starch, the complex is devoid of thickening and gelation properties or has these properties only to a significantly-reduced extent. The ability of the starch to thicken and/or gel i~ altered by rupturing starch grains i '~
and for~ing aggregates under the noted reaction conditions.
When the complex (rather than unmodified starch) is admixed with other material, the composite total solids may be increa~ed by more than 100 percent, even though the viscosity of the admixture is concurrently drastically decreased and no gelation occurs. Such a result i8 extremely important for products which must be sterilized and for semi-fluid products, such a~ baby food, wherein bulk is a problem.
The consistency of the protein/starch complex differs from that of the starch from which it was prepared:
it is less sticky and less gummy. The extent to which these particular properties are changed i8 controlled by varying the previously-noted critical factors. Generally, increasing the proportion of protein, introducing ions into the reaction mLxture or increasing the amount of such ions, and increasing the reaction time or temperature reduce the stickiness and gummy nature o compositions otherwise containing modi~ied starch. With the~e properties thus altered, the protein/starch complex is more-ea~ily used in different semi-solid products, such as meat and fi~h products. By controlling stickiness, the modified ~tarch is more useful, e.g. for pastiny particle together, in those 10~653 in~tances where unmodified starch normally provides a consistency which is too gummy.
The flow properties of the protein/starch complex are significantly different from those of, e.g., cold-swelling starch. The degree of thixotropy and elaaticity is materially reduced or entirely eliminated by altering reaction conditions in the same manner aa suggested in the preceding paragraph.
The pre~ent modification of starch does not only reduce or eliminate undesirable properties; it al o introduces desirable propertiea in the obtained product. 0 The co~plex is thus u~eful for emulsion stabilization, a utility not possessed by cold-swelling starch.
As the modified starch does not have any residual flavor of its own, it does not alter the taste of food products with or in which it is used.
All properties of the protein/~tarch complex are controllable by varying process parameters, such as the ratio of protein to starch, the reaction time and temperature, and incorporating salt in the reaction mixture.
The protein employed is a casein or caseinate.
The protein i6 optionally casein or a caseinate, such as ammonium caseinate, calcium caseinate or sodium caseinate.
Alternatively, the protein is, e .g ., in the form of para-casein, acid-precipitated casein or ~elf-soured casein. The properties of the protein/starch complex are substantially independent of the nature of the employed for~
of casein.
Although starchea vary in molecular ~tructure and in properties, depending upon their botanical origin, they all have fundamental common properties which are similarly 9~ 3 modified by the present invention, which i8 thus substantially independent of the source of starch employed.
The starch can thus be that of arrowroot, barley, bean, buckwheat, cassava (tapioca), corn, oat, pea, potato, rice, rye, sago, sorghu~, waxy maize and/or wheat. !V`
Naturally-occurring starch is separated from different parts of plants. Starch from corn, wheat, sorghum and rice is separated fro~ the seed that from cassava, potato and arrowroot is separated from the root; and that from sago is separated the stem. The manner in which the starch is thus separated is conventional and well known; it does not constitute a part of this invention. Although the amylose~amylopectin ratio may vary from starch to starch, such is not a critical factor with regard to this invention.
Since the degree of swelling varies sub~tantially from starch to starch, the maximum starch concentration in any admixture may well depend upon the ~ource or origin of the starch. Of the three most com~on types of starch, the order of precedence with regard to concentration is wheat starch ~ corn starch > potato ~tarch.
The present modification of starch is predicated on a specific action on starch granules and has no ~elationship or relevance to other swelling or foaming agents. When native starch granules are heated they lose their birefringent properties and start to swell. Water penetrates into the granules and solubilized amylose and amylopectin diffuse out into the solution. There will be an equilibrium between solubilized a~ylose and amylopectin inside and outside the granules. The swelled ~tarch granules can be seen in FIG. 8 showing swelled corn starch granules at 95C. If casein or caseinate i8 added the 1Q~16S3 protein forms co~plexes with the ~tarch components. The complexes make up particles of various sizes which are seen in the ~icrograph of FIG. 9. If ~n insoluble but colloidal stable particle of starch-caseinate complex is formed, the equilibrium between soluble starch components inside and outside the granule will be affected. This means that more soluble starch components will leave the granule, and if the reaction is permitted to exceed far enough, the granules will be completely emptied. Such a case i8 illustrated in the micrograph of FIG. 9, where some granules appear as emptied ghosts. The com~lex is thus bes~ identified by microscopy. For large complexes light microscopic methods are sufficient. For small complexes electron microscopy may be necessary. FIGS. 8 and 9 are example~ of light micrographs. The degree of complex formation can be controlled and thereby the physical properties of the ~tarch granules. Propertie~ liXe viscosity, stickiness and gumminess can be changed. By controlling the complex formation properties induced by the formed complexes c~n be "tailored" and controlled. The complex formation induces properties such as emulsion stabilization of animal fat, important to meat products. By controlling the interactions between starch granules, solubilized ~tarch and complexes ~particles) various type~ of textures can be created. The ~orce~ involved are electrostatic forces, h~drofobic bonds, hydrogen bonds and van der Waal ' 8 attraction orcec. The complex formation starts immediately as swelling of the starch granule~ takes place. The number and size of complexes increaæe with time.
The formed complex i8 produced over a wide pH
range, e.g. from a pH of about 2 to a pH of about 12. No : L~9~3 particular increase in pH iS required during the reaction.
By using milX-free casein, gelation of starch, e.g., can be completely inhibited. This is not pos~ible when casein or caseinate is employed as a component in milk or with milk powder.
Although the casein or caseinate need not necessarily be in pure form or separated from other ingredients, there are certain ingredients, such as lactose, which impede complex formation~ Effecting complex formation in the same absence of Ruch inhibiting ingredient is naturally advantageous and is effected in conventional equipment according to recognized procedure~. Process equipment employed ~or producing cold-swelling ætarch i~
useful for this purpose. After complex formation, with or without mono- or poly-valent salt, the re~ulting modified starch is dried and sold in powder form. Mixing, heating and drying are the three necessary unit operations. An additional unit process may be required if the dry product is to be given a texture. Conventional texturizing 20 proce88e8 8uch as extrusion or spinning can be used.
The mixing and heating can take place in the same system, e.g. in a heat exchanger Contherm (trade mark) rom Alfa-Laval AB, Sweden. In this case the temperature should not exceed the boiling temperature. Another pos~ibility i8 that heating and drying takes place simul~aneously, e.g. in a roll dryer. The upper temperature limit can then exceed that of the boiling temperature. The lower limit in both cases is the gelation tempexature, if native starch granules are uæed. At the gelation temperature the heat causes swelling and breakdown o~ the crystalline regions of the starch granules. If the starch granules have been damaged, e.g. by mechanical treat.nent, and some of the crystalline regions already have been broken, a lower te~perature may be sufficient. The amount of energy required for breakdown depends on the pre-history of the starch granules and the conditions under which they are broken down. The examples given all refer to experiments on starches having most of the granules undamaged (native ~tarch). The starch-gelation temperature, usually from 60 to 85~C, is the temperature at which the starch lose~ its birefringence properties.
As ~oon as a~ylose and amylopectin collide with a caseinate molecule the complex formation 6tarts. With time the number and size of the particles will increase. The relation ti~e/temperature will therefore deter~ine the properties of the formed complexes as well a~ the properties o~ the modified starch granules. With increasing ti~e and temperature the identity of the original starch granules will be gradually lost. In order to keep the cost of processin~ low the dry content should be kept as high as the processing equipment permits. Theoretically there is no lower limit. The water content must be high enough for swelling and diffusion of macromolecules. Under realistic conditions the dry content should be 8 - 30%. The higher the dry content, the higher the viscosity and the more dificult the handling. The dry content will influence the reaction time necessary to obtain certain properties.
The protein/starch ratio can be 1:20 to 4:1 but '~
mo~t desirable is 1:16 to 4:3.
pH can be about 2 to 4 and about 5 to 10. Close to its isoelectric point around pH 4.5 casein has low solubility. For practical purpose~ pH of 5.5 to B.0 is recommended.

1~9~L EiS~

For monovalent ions salt concentrations of 0-0.6 M
are recommended; for polyvalent ions concentrations of 0-0.3 M are recommended.
The ratio of casein/caseinate to starch ha~ a considerable effect on the properties of the product. For the several properties different optima apply.
If i~ is de~ired to avoid gelation and thickening, the greatest possible portion of the starch should be formed to complexes. In that case, the casein/caseinate concentration should be relatively high. The addition of salt promotes the complex formation, and the gelation is avoided completely only in the presence of ~alt. Good effects as far as a decrease of the viscosity is concerned have been obtained at a ratio of ca~ein/caseinate to starch ranging from 1:4 to 4:3.
The stickiness i8 largest for untreated atarch and decreases with increasing degree of complex formation. The stickiness decreases with increasing addition o~
casein/caseinate and increasing addition of salt. Optimum conditions are entirely dependent on the product wherein the starch i8 to be used. Thanks to the good control possibilities, starch products having different degrees oP
stickiness can be "tailored" for different fields of demand.
As already noted, the incorporation of ~alt in the reaction medium has a po~itive effect on complex formation and thus on properties of the resulting modified ~tarch.
Optimum conditions for complex formation include salt in the reaction mediu~. The effect of salt iB not limited to any one or group of salts but i~ obtained with different salts.
The largest effect is obtained when the reactants (casein or caseinate and starch) are in contact with polyvalent ione l~g~6S3 during reaction. Under such conditions, considerably lower concentrations of salt (polyvalent-ion-containing salt) are required than, e.g., for NaCl. The greater the salt effect, the lower the thixotropy and the elasticity component of the final product. complexe8 are also formed in the absence of salt, but the reaction equilibrium i8 not so heavily displaced towards complex formation, whieh i3 advantageous in some applications. The complex formation is not dependent on pH within range~ of in~erest in foodstuff technology.
The discussion has so far referred to application~
wherein it is of .interest to reduce the viscosity. For use in meat products such reduction is not a requirement. For this application the complex formation should proceed far enough for new functional properties to occur and far enough to reduce the gumminess of the final product but the viscosity should not be decreased too much. The new functional property that is created ls "emulsion stability"
of the fat used. Such a product can e.g. be created if the starch/casein ratio i~ 8:1 to 4:1 and if the complex is formed in the presence of 0.2 M NaCl or in the absence of salt.
The application of starch products modified by co~plex formation with casein or caseinate can be summarized as follows: Sausages such as Frankfurters: The modified ~tarch gives good water and fat holding properties. There are good possibilities to "tailor" the consistency of the final products. Minced meat products: The modified starch can be used in order to paste particles together which facilitates the formation of minced meat products. The consistency is improved compared to un~odified starch.

1~)91~653 Half-solid and liquid products, such as soups, ~auces, youghurt, dres6ings, ketchup, baby food, and porridge : The viscosity can be controlled. The modified starch can be frozen and due to the complex formation the degree of retrogradation is ~ubstan~ially decreased. Replacers for eggwhite in such products as toppings, meat products and bread: Functional properties can be created compatible with those of eggwhite.
Exemplary embodiments of the invention follow.
The examples are presented solely for the purpose of illustration and in no way limit the na~ure or ~cope of the invention. In the examples all temperatures are in degrees Centrigrade and all parts are parts by weight unless otherwise specified.

Disperse 4 parts of caseinate in 100 part~ by volume of a 0.1 M phosphate buffer solution having a pH of 7.0 (neutral pH value), and then add 4 partfi of corn-starch to the thus-obtained dispersion to form a reaction medium.
Heat the reaction medium in a Brabender Viscograph from ambient temperature to 95 at a rate of 1.5 per minute.
Maintain the temperature of the reaction medium constant at 95 for 30 minutes, and then cool the reaction ~edium to approximately ambient temperature at a rate of 1.5~ per minute.
Conduct the preceding steps ~eparately with each of two different caseinate~: Sodium caseinate ~odinol (trade mark) from A/S Lidano, Denmark, and sodium caseinate from DMV, Holland. Dry and grind the reæulting starch according to conventional procedures used for starch.
Repeat the entire preceding procedure without any 10~L653 ca~einate in the phosphate buffer.
FIG. 1 provide~ a co~parison between the viscosity at different temperature~ of the aqueous starch col~position which was not reacted with caseinate, that which was reacted with Sodinol (A) and that which was reacted with sodium .?
caseinate from DMV (B). Both curve A and curve B illustrate ~ignificant reductions in viscosity at the different temperatures noted. FIG. 1 further shows that the viscosity decreased Qubstantially at the addition of each type of caseinate. With the caseinate from Lidano, gelation was entirely elilninated, and swelling ceased a~ter a very short initial period. With the caseinate from DMV the resulting modified starch ailed to form any gel and reflected materially-reduced ~welling.

Effect two separate reactions, each in 100 parts by volume of a 0.1 M phosphate buffer, according to the procedure of Example 1 ~except as otherwi~e indicated), one with one part and the other with 4 parts of caseinate fro.n DMV and both with a reaction-mixture pH of 5.5. (The specified conditions si~nulate those which prevail in a meat sy3tem.) Maintain the pH constant at 5.5 and heat only to 70. Maintain the temperature at this level for 30 minutes before cooling.
Repeat the procedure without any caseinate in the reaction ~ixture.
FIG. 2 reflects the viscosity/temperature relationship throughout the pxeceding procedure for preparing the comparative product A with zero percent 3~0 caseinate, the reaction product B with one percent caseinate and the reaction product C with four percent caseinate.

~91~S3 FIG. 2 confirms the ~aterial decrease in visco~ity with increased caseinate concentration. Swelling and viscosity are very much reduced when the reaction mixture contains 4 percent by weight of caseinate, i.e. when the total solids of the employed starch are increased by 100 percent by weight, as shown by curve c.

Following the procedure of Example l, prepare a corresponding product with 5 parts of pure corn-starch in 100 parts by volume of distilled water (no casein or caseinate and no other additive). Dry and grind the resulting product according to conventional procedures e~ployed for starch.

Following the general procedure of Example 1, react 5 part~ of corn-~tarch with 4 parts of caseinate (from DMV) dispersed in 100 parts by volwme of distilled water (no additive). Dry and grind thus-obtained modified starch according to conventional procedures used for starch.

q Following the procedure of Exa,~ple 1, react 5 parts of corn-6tarch with 4 parts of caseinate ~rom DMV) in 100 parts by volume of an aqueous 0.2 M NaCl solution. Dry and grind the resulting modified starch according to pro¢edures conventional for starch.

Following the procedure of Example 1, react 5 parts of corn-starch with 4 parts of caseinate ~from DMV) dispersed in 100 parts by volume of univer6al buffer (containing phosphate and citrate ions, see Example 13) at a pH of 7. Dry and grind the resulting modified starch according to procedures conventional for starch.
Examples 3 to 6 are directed to producing products differing in degree of co~plexing, stickiness and thixotropy. The degree of thixotropy can be measured, as can the degree of gel structure, but to a lesser extent.
Stickine~s must be estimated by sensory evaluation and is correlated to the other noted propertie~. This group of exa~ples reflects the effect on starch of casein or caseinate alone, with a salt, and wi~h polyvalent anions.
FIG. 3 to 6 represent the relationship of shearing force (vertical axis) to shearing rate (horizontal axis) for products prepared according to Example~ 3 ~o 6, respectively. The area between the upper and the lower curves in each of these figures i8 a measure of thixotropy tgelation). The mea~urements were made ln a Haake Rotovisko, Model RV3 (Gebruder Haake K.G.) with a MVI
measuring system. During the measurement the temperature was kept con~tant at 37C. The shearing force is repre~ented by, and the shearing rate is represented by D.
T o iS the force necessary to put the sy~tem into motion.
The greater the thixotropy and T o, the stronger the gel ætructure in systems o this type.
FIG. 3 presents the 10w curve for corn-etarch treated without any additive. A high To prevails, and the thixotropy is great. Moreover, there is a clear maximum in shearing force, which means that the ~tructure is broken down at shearing.
When 4 percent caseinate i8 added (Example 4) and the ~olids content i9 thus increased by 80 percent, both To and thixotropy decrease, as shown by FIG. 4. No maximum in shearing force i8 observed. When the reaction i9 effected ~, in the presence of 0.2 M NaCl solution (Example 5), thixotropy and T 0 decrease substantially, as shown in FIC.
5. In the presence of polyvalent ions (Example 6), the obtained product reflects no sign of gel structure; neither T 0 nor thixotropy is evident from FIG. 6.
~XAMPLE 7 Disper~e 0.5 parts of sodium caseinate in 100 parts by volume of 0.~ M calcium sulfite (aq) solution having a pH of 9, and then add 8 parts of wheat starch to the thus-obtained dispersion to form a reacton mediuL~. Heat the reaction medium in a Brabender Viscograph from ambient temperature to 85 at a rate of 1.5 per minute. Maintain the temperature of the reaction medium constant at 85 for 45 minutes, and then cool the reaction medium to approximately ambient temperature at a rate of 1.5 per minute. Stir the reaction medium throughout the preceding procedure to maintain all solids dispersed throu~hout the aqueous medium.
Dry and grind the resulting modified ~tarch (starch complex) according to conventional procedures used for starch.
~XAMPLE ~
Disperse 9 parts of calcium caseinate in 100 parts by volume of 0.1 M calcium tartrate (aq) solutioll having a pH o~ 8, and then add 6 parts of tapioca to the thus~obtained dispersion to form a reaction medium. Heat the reaction mediu~ in a Brabender Viscograph from ambient temperature to 90 at a rate of 1.5 per minute. Maintain 0 the temperature of the reaction ~edium at 90 for ~5 minutes, and then cool the reaction medi~ to approximately al~bient temper~ture at a rate of 1.5 per minute. Stir the 91~53 reaction medium throughout the preceding procedure to maintain all solids dispersed throughout the aqueous mediul~.
- Dry and yrind the re~ulting modified starch (starch complex) according to conventional procedures used for starch.
~XAMPLE 9 Disperse 2 parts of acid-precipitated casein in 100 parts by volume of O.S M NaCl (aq) solution having a pH
of 6, and then add 4 part~ of rice ~tarch to the thus-obtained dispersion to form a reaction medium. Heat the reaction medium in a Brabender Viscograph from ambient temperature to 85 at a rate of 1.5 per minute. Maintain the temperature of the reaction medium constant at 85 for 35 minutes, and then cool the reaction mediurn to approximately ambient temperature at a rate of 1.5 per minute. Stir the reaction medium throughout the preceding procedure to maintain all solids dispersed throughout the aqueous medium.
Dry and grind the resulting modified starch ~starch complex) according to conventional procedures used for starch.

Disper~e 4 parts of self-soured caseinate in 100 parts by volul~e of 0~1 M calcium citrate (aq) solution having a pH o~ 5, and then add 3 parts of sago starch to the thus-obtained di~per~ion to form a reaction medium. Heat the reaction medium in a Brabender Viscograph from ambient temperature to 90 at a rate of 1.5~ per minute. Maintain the temperature of the reaction meditm constant at 90 for 20 minutes, and then cool the reaction medium to approximately ambient temperature at a rate of 1.5 per minute. Stir the reaction medium throughout the preceding procedure to maintain all solids dispersed throughout the aqueous medium.
Dry and grind the resulting modified starch (starch complex) according to conventional procedures used for starch.

Following the procedure of Example 1, add 4 parts by weight of potato starch separately to each of the 10 following:
a) 100 parts by volume of distilled water;
b) a disper~ion of 6 parts by weight of milk powder in 100 parts by volume of di6tilled water;
c) a di~persion of 8 parts by weight of milk powder in 100 parts by volume of distilled water;
d) a dispersion of 10 parts by weight of milk powder in 100 parts by volume of distilled water;
e) a dispersion of 12 parts by weight of milk powder in 100 parts by volume of distilled water.
Heat each reaction medium (a) through (e), maintain its maximum temperature for the prescribed period and then cool it aG spé~i~ied in Example 1.
The change in vl~cosity of each of (a) through (e) during the noted treatment is reflected in FIG. 7.
As demonstrated by the preceding Examples, gelation of starch can be completely avoided by incorporating anions, preferably polyvalent anions, e.g.

~al91653 phosphate ions (see Example 1), in the reaction medium. It is not possible, however, to avoid gelation or even to reduce the viscosity to any significant extent when a mixture of starch and milk powder (containing casein) is similarly treated. Thi8 i~ illu~trated by FIG. 7, which shows the Pffect of different percentages of milk powder on 4 percent by weight dispersions of potato starch. Milk powder contains about 30 percent by weight of casein and 53 percent by weight of lactose. As is commonly known, lactose ha~ a retarding effect on the swelling of starch grains.
FIG. 7 confirms that swelling is retarded initially, but milk-powder mixtures rapidly reach a thicker consistency than pure starch. When caseinate, rather than milk powder ~containing ca~ein), is combined with starch in corresponding systems, the viscosity decreases with increasing caseinate concentration, and gelation is completely avoided when 4 percent by weight of caseinate (corresponding to 13 percent by weight of milk powder) is combined with 4 percent by weight o starch.

In order to further illustrate the effect of starch-caseinate ratios on the vi~cosity, the following procedure is adopted. Make caseinate dispersion in 0.1 M
pho~phate bufer at pH 7.0 of the following concentrations by weight: 0%, 1%, 2%, 4%, 6%. Add 5% ~orn-starch to each dispersion. Heat in a Brabender Amylograph with 1.5C/~in.
to g5C. After a holding time of 30 min. at 95C cool the dispersion at a cooling rate of l.5C/min. The effect of caseinate concentration on the viscosity can be seen in FIG.
10 wherein the curves designated A, ~, C~ D, and E relate to the concentrations 0%, 1%, 2%, 4%, and 6% caseinate, ~91~i53 respectively. The viscosity is decreased by increasing caseinate concentration to a concentration of 4~, where the gelation is completely suppressed.

In order to illustrate the effect of various salts on the viscosity of modified starch dispersions the following procedure is adopted:
Make a 5% corn-6tarch dispersion in 0.1 M
phosphate buffer at pH 7. Composition of buffer, see below.
Make 4~ caseinate dispersions at pH 7 in the following solutions:
a) No salt, distilled water b) 0.2 M NaCl c) 0.1 M phosphate buffer d) 0.019 M citrate e) 0.019 M phosphate f) universal buffer Add 5% corn-starch to the caseinate di~persions.
Composition of buffer~:
Phosphate at pH 7: 610 ml 0.1 M Na2HP04 + 390 ml 0.1 M Na~2po4 Universal bufer : 1 1 solution is made which contain 6.008 g citric acid, 3.893 9 KH2PO~, 1.769 g H3B03 and 5.266 g ~arbitol. 0.2 M NaOH i~ added to the solution until the desired pH i~ obtained (approx. 1,000 ~nl NaOH to

2,000 ml solution).
The dispersions are heated at 1.5Clmin. to 95C.
held at 95C for 30 min. and cooled at 1.5C/min. ~he result is shown in FIG. 11 wherein the curves A to F relate to the dispersions a to f, respectively, defined above and curve G relates to the 5% pure corn starch dispersion.

~16S3 It is seen that the ~ffect o~ complex formation on viscosity is s~all in the absence of salt~ The strongest effects are obtained in the presence of polyvalent ions.
~XAMPLE 14 For making a stabilized emulsion of animal fat potato starch is added to a 4% caseinate dispersion at a starch-protein ratio of 4:1. No salt i8 added. The dispersion is heated to 95C for 10 min., roller-dried and ground.

For the sa~e purpose as in Exa~ple 14 potato starch is added to a 4~ caseinate dispersion made in 0.2 M
NaCl solution. The starch/protein ratio i~ 4:2. The mixture is heated to 90C for 10 min., roller-dried and ground.
The products made according to the procedure~ in Examples 14 and 15 are tested for emulsion stability in the following way:
Starch-casein complex, pork fat and water in a ratio of 1:6:6 are mixed in a turbomixer at high speed. The emulsion thus obtained is sealed in a can and cooXed for 30 min. After cooling the cans are opened and the fat and water rélease measured. No ~at or water release was obtained when the two casein-starch complexes were tested.
For reference native starch and caseinate were mixed in the above described proportions without complex formation. In this case a substantial fat and water release of the heat-treated emulsions was observed. This procedure gives information on how the fat will be stablized in a meat emulsion.
The invention and its advantages are apparent from 1~9~6~3 the preceding description. Various changes may be made in the process, the actual ingredients employed and the resulting modified starch (complex) withou~ departing from the spirit and scope of the invention or sacrificing its material advantages. The process and products hereinbefore described are merely illu~trative of preferred embodiments of the invention.

,~i

Claims (19)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A protein/starch complex having a) protein in the form of casein or caseinate and b) a protein/starch weight ratio of from 1:20 to 3:2.

2. A complex according to claim 1 wherein the starch is root-derived starch.

3. A complex according to claim 2 wherein the root is cassava, potato or arrowroot.

4. A complex according to claim 1 wherein the starch is seed-derived starch.

5. A complex according to claim 4 wherein the seed is corn, wheat, waxy maize, sorghum or rice.

6. A complex according to claim 1 wherein the starch is stem-derived starch.

7. A complex according to claim 6 wherein the stem is sago.

8. A complex according to claim 1 wherein the protein/starch weight ratio is from 1:4 to 4:3.

9. A complex according to claim 1 having emulsion-stabilizing properties.

10. A complex according to claim 1 having a reduced degree of gel structure and of thixotropy as compared with those of non-complexed starch.

11. A salt-containing complex according to claim 1.

12. A polyvalent-ion-containing complex according to claim 1.

13. A process which comprises complexing starch with casein or caseinate by heating them together in an aqueous reaction medium at a temperature above the starch-gelation temperature for a period which is inadequate to cook the starch.

14. A process according to claim 13 wherein the reaction medium comprises ions and the heating temperature is not in excess of the reaction medium boiling temperature.

15. A process according to claim 14 wherein the anions are polyvalent.

16. A process according to claim 13 which comprises dispersing the casein or caseinate in water before adding starch thereto and heating.

17. A process according to claim 13 wherein the complexing is obtained in a texturing procedure.

18. A process according to claim 17 wherein the texturing procedure comprises extrusion.

19. A process according to claim 17 wherein the texturing procedure comprises spinning.