CA1190792A - Process of altering microstructures in polydisperse aqueous systems - Google Patents

Abstract

Abstract of the Disclosure In a process of altering microstructures in polydisperse aqueous systems with the aid of separating processes, the microstructures of dispersed natural substances and/or additives are so adjusted relative to each other by means of the separating processes that properties of the end product are predetermined in the starting material when the microstructures are still water-soluble.

Description

7~3;2 This invention relates to a process Gf altering microstructures in polydisperse aqueous systems which contain water-soluble substances, and in particular milk.
In their original s~ate, such systems are in a state oF equilibrium. The structures of the dispersed substances match each other regarding ~heir solubility in water. The micro-structure of each dispersed substance assumes the configuration which corresponds to the quantity of water which is available.
For this reason the entire system can be described as being in a state of equilibrium. ~Each of ~he individual systems is also in a water-dependent state of equilibriumj.
This state can well be described, e-g-, for milk, which is one of the most complex polydisperse aqueous systems.
Consisting of carbohydra~es, enzymes, fat, protein, salts, trace elements, enzymes and certain ot.her substances, milk is a basic foodstuff.
The above-mentioned nutritive substances possess a larger number of propertiesO Some o~ these are:
- hydrophilic or hydrophobic properties;
- foam-forming, gel-forming, thickening properties;
- thixotropic, agglomerating, cross-linking properties, - an ability to bind, form or relase substancesi - buffering~ sweetness-increasing, sweetness-decreasing, caramelising properties;
- odor-absorbing9 taste-influencing, flavor-activating properties;
- sour-promoting, acid-binding propertiesi - energy-releasing, energy-absorbing properties~ etc.

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Irl original milk, tn3 water-bindincJ property of the substances dispersed in the milk is predolîlinantî all other properties are subord:Lnate to that one property and are not available in the aqueous stat.eO
Besides/ owiny to influences which are due to th~
feeding of animals, environmental condi.tions and an improper treatr.lent, the water-dependent states of equilibrium of -the .substances dispersed in polyd.i.sperse aqueous systems may be unr`avorably altered with regard to the processing of such systemsO
For instance, the presence of inhibitors, an excessive water content, and an activation of enzymes can often be detected~
Systems exhibiting the last-mentioned undesirec1 features previously had to be rejected or~ if they were not recognized in time and were l~rocessed, involved substantial losses in production~, In the previous practice, systems of the kind described first hereinbefore are -tre~ted regardless of the states of the several dispersed substances and su~stantial processing sequences were required to develop a certain necessary property of a certain dispersed substance~
This will be explained with reference to the production of cheeseO
The production o:E cheese deperlds highly on gel-Eorming, cross-linking and enzyme forminy properties oE

proteins.
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Until recentl.y, the in-.iro system of milk, including all systems oF the several clispersed substances, was processed to promo-te the above-mentioned properties~

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~ actose and certain sal~.s as well as ~he so-called whey proteins all had ~o be processed too although in the water solub'e state in which thcy are present they strongly disturb the development of the desired gel-Eormi.ng properties of cas~in~
rrhey are then removed more o.r less in a very lata stage of the production process~
In recent technologies, the systems are :Eirst subjected to separatiorl processes, such as ultrafiltration or ultrafiltration combined with other separating processes, for instance, vacuum evaporation, so that the contents of dispersed substances which would disturb the development of a certain property of another dispexsed substance will be decr~ased~
For instance, ultrafiltration processes for producing a protein concentrate having different protein contents or ultrafiltration processes for removing water from the systems before their actual ultrafiltration are known and have been adopted to provide a specified protein concentrate regardless of th.e behavior of the individual systems during the separating steps, their influenc2 on each other and their properties in the concentrate.
Ir. these processes, the entire system is treated in an entirely indiscriminate manner reyardless of the influences of the individual systems on each other during the processing, only with the aim to provide a specified conc~ntrate having specified contents of individual ~ispersed suhstances, regardless whethe.r or not individual systems can still ass~e water~soluble states and regardless of the behavior of the individual systems can s~ill assume ~L907~
water-soluble states and regardless o~ the behaviour of the individual systems in their incidentally assumed states.
In German Opened Applications 22 11 737 and 27 46 532, reference is made only to the protein content which can be obtained and the final water content which is desired.
In the use of said processes it has been found that concentrates in which the properties of the dispersed substances have been changed arbitrarily and indiscriminately are virtually useless because bitter substances, e.g. may form therein and owing to the uncontrolled particle size distribution of the pro-teins these concentrates do not permit a controlled cross-linking of proteins.
It is an object of the invention to provide a process by which the microstructures of dispersed substances contained in polydisperse aqueous systems, such as milk or beer, can be matched while the substances are water-soluble. This object is accomplished according to the invention in,that the dispersed substances contained in the starting material and/or substances added to the starting material are subjected to separating pro-cesses whereby their microstructures are altered to assume such a relation to each other that properties of the desired end product are predetermined in the starting material in which the dispersed substances are in a water-soluble state.
According to the present invention there is provided a process for standardizing the structure of the proteins in milk, comprising: a) ~ thdrawing a portion of the milk and in-creasing the concentration of protein constituents in said with-drawn portion by ultrafiltration by a factor of at least one-and-a-half; b) mixing the concentrated portion with the residual portion of ~he milki c) concentrating the resulting mixture by ultrafiltration by a factor oE at least one-and-a-half; d) removing a portion of the water from the resulting concentrate . ~ _ ~ i~3 37~

by vacuum evaporation or reverse osmosis at a temperature below 65C; e) subjecting the concentrate obtained in step (d) to -ultrafiltration; f) mixing concentrate obtained in step (e) with the water obtained in step (d); g) subjecting the mixture obtained in step (f) and the iltrate obtained in step (e) to a separate heat treatment at a temperature of up to 85C; and h) subsequently remixing the mixture and filtrate of step (g).
In the process a~cording to the invention the relation-ship of the dispersed substances, whether they are originally contained in the starting material or have been added thereto, are adjusted in quantity, particle - 4a -7~

siæe~ water solubility and/or equilibriumO If the products are li~uid or include the entire original solids content, the li~uid which has been removed and which may have been treated or may not have been treated can subse~uently be added entirely or in part. Liquid can be subsequently added in a c~uantity which exceeds the quantity of liquid that has been removedO The separating ~rocesses may be carried out at dif~eren-t temperatures or liquid may be subsequently added at different -temperatures~ The pro-portions of the dispersed su~stances originally containedin and/or added to the starting rnaterial can be changed by separatin~ processes which are carried out in series or in paralleli In a preferred embodiment of thP process according to the invention, a preconcentrate is prepared and is then diluted with polydispersed systems, which may have been treated or may not have been trated, or with the starting matexial, which may have been treated or may not have been treated, and the resulting mixture may subsequently be subjected to another separa-ting process and additional steps for influencing ~he microstructures may be adopted during the separating process, if desired, when the substances which are to be concentrated hava reached a concentration which exceeds their initial concentration in the mixture or amounts to at least one and a half times said initial concentration in the mixture. This process may be used, e~g., to produce milk products/ For instance, when it is desired ~o produce milk products by ultra-filtration, a preconcentrate is prepared, which may contain substances that are to be concentrated, such as proteins, in twice their initial concentration, and which is then ~i~0~9~

diluted with -treated or un-treatecl rnilk, whereaiter the resultingl~xtur~ is subjected to ultra~iltratio:n once more G
When the substances to be concentrated, such as protain, have reached a concen~ration which is at least one and a half times their concentration in the mixture before the ultra~ ration, additional measures for influencir~g micros-tructures may be carried out during tne ultra~iltra~
tion. This process may be carried out, eOc~, to make milk products~ In tlle ~la.~ing of milk proclucts by ultrafiltration, for insta.nce, a praconcentrate is prepared (which ~as, e~g., abou-t twice the contents of substances to be concentrated, such as protein). That concentrate is tllerl diluted with untreatecl or treated milk and -the mixture is subsequently ultrafilterecJ. once moreO When the substa~ces to be concentrated ~such as protein~ have reached at ]east one and a half times their initial concentration~ additional measures for influencincJ microstructures can b~ carried ou~
duriny the ultrafiltration~
The present invention is concerned with controlled ~0 influ~nces ex~rted on inclividual sys-tems in an overall system. Within the scope of the invention it has been ~ound that in the proauction o~ products from said sys tems it is desirabl to develop cer-tain properties of several dispersed substances when these are still water-soluble so that these properties of indiviclual dispersd substances CaXl be utilized in a controlled manner because this will permit the processincJ to be ca:rriecl out with a smaller enercJy cons~rlp-tion, a ihlc~ller economy and a small-~r pollut:ion oE the erlvironment~
In accordance with the invention, separatincJ

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processes known per se are carried out ~.o effect controlled, alterations of the microstructures of the individual systems during the processin~ in such a manner tha-t initially latent pro~rti~s which are desired for the processing to produce of a given procluct are ~eveloped when the dispersed systems are still in a water~soluble state.
For ~stance, when sXim milk is suhjected to ultrafiltration accordiny to the state of the art~ the protein which is present is water-soluble and its concentration will be increased. At the same time, -the also wat~r-soluble lactose and salts are removed regardless of the rnicrostruc-tural state of the proteinO As a result, tlle proportions will be chanyed as follows i~ the protein concentration is increased 1:5.
Ratio of conten~s Ratio of contents in in starting milk concentrate 5 parts casein to 5 parts casein to 1 part protein 1 part protein 20 0.6 part casein to 2.5 parts casein to 1 part lactose 1 part lactose 0~8 part casein to 8 parts casein to 1 part ash 1 part ash 23 parts casein to 30.3 parts casein to 1 part calcium 1 part calciwn As a result o~ that change in proportions, protein micelles divide -to form sub-micelles an~ the stability of that protein is so strongly changed tha~ subsequent process steps result in yrea-t demacJe and cannot be optimiæecl~

119(3~92 These unfavorable alterations o:E the microstruc-tures of the substances dispars~d in milk result froM all separa-ting processes carriea out thus F.ar because they result in substantial c.hanges of the proportions of all or some substances dispersed in the milk regarclless o~
their states of equilibrium and the influences thereof on -the microstructures o~ the several dispe:rsed substancesO
Fo.r this reason the invention calls for such a combination of separating processes that the changes in the proportions o~ the substances dispersed in milk result in such alterations of the microstructures of the substances dispersed in milk that desired properties of the end produc-t are already present in the starting product or are so prepared therein that final states can be stabilized.
This will be explained with reference to the production of certified milk ~heese~ sour milk products, fresh cheese, essences and beerO
.1) Production of Certified Milk In the production of certified milk, a legally prescribed heating process is required, in which states o~ equilibrium of various dispersed substances are chan~ed in an en-tirely indiscriminate manner; this results in undesirea changes of properti~sO
For instance, a high-temperature hea-t treatmen-t will result in an as-boilea taste and oxidizad taste, an ultrahigh-temperature haat treatment will result in carameliziny and in a lower stabili-ty o~ proteins, and short--time heat treatment will rasult i.n a slight as-boiled taste and in an inadequate sterilization.

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For this reason the invention provides a process o:E exerting a controlled influence on the microstruetures of disper~ed substan~es by means of known sepaxacing processes, whieh are systematically carried out to exert such an influence on individual structures that a subsaquent heat treatment will not result in uncontrolled ehanges of proparties so that, e~g~ 9 undesired chanyes o flavor will be avoidedO
If the starting product is a satisfactory oriyinal raw milk, whieh is to be subjected to an ultrahigh-tempera-ture heat treatment, uneontrolled ehanyes o~ the micro-structuxes of the proteins, of lactose, or of the salts, and microstructural reaetions of laetosP and proteins must be prevented~
In the process aecording to the invention, milk is first subjeeted to a moderate ultrafiltration in order to increase the concentration of protein by a small percentage and ef~ect a xelative decrease of the eonten-ts of lactose and salts, In that step, the microstructures o the protein particles which are present are made more uniform.
The polydisperse microstructure are reduced in size toward ~onodisperse forms~ This will reduee the stability o~the solution of protein in water~ Without additional measures t subsequent heatiny steps would considerably demage the proteinO For this reason, a subsequf~nt separatiny process by whi.ch only water is removed would have th~ result that -the protein particles haviny a uniform, small size are uni~ormly increased in size, the surfaee of the total protein is reduced, the polari~y which acts outwarclly is increased and the ~L9~

ability to bind water is -thus încreasedO
As a result of the prececling ultrafiltration, all protein particles`can be uniformly increased in size in a succeeding evaporating step so that an approximately monodisperse structure is obtainedJ which has a very stable state of equilibriumO
The substances removed by the separating process (parmeate and water) are added to the thus treatad milk in part or en-tirely or in a larger quantit~ because the protein particles which have been increased in size will violently bind that liquid without an alteration of their structure. That efEect can be assisted by a variation o~
temperature during the addition or by separate treatments of the two phases at different temperatures.
The microstructures can be further i.mproved if, e~g., electrodialysis processes are used tooO
In practice, the process can be carried out as Eollows:
It is desired ~o produce 10,000 liters of milk that h~s been subjected to an ultrahigh-temperature heat trea~ment. The milk contains about 209 % casein, 0,6 %
protein, 4.7 % lactose and Oq7 % saltsO The total solids content is about ~09 %l a) Produc-tion of a Preconcentra-ta A part of the milk, e~gO, 2000 li-ters, is subjected to ultra:Eiltration at a temperature below 65 C
to obtain a concentrate which contains about 5.8 % casein 1 a ~ % protein 4.7 % lactose 007 % salts 11,3 % total solids ~L19079;2 The filtrate obtained con-tains about 0.2 ~ protein 4.7 ~ lactose 007 ~ salts and is storedO
b) Preparation of 3 ~lixture The remaining part of the milk amounting, eOg., -~o 8000 litars, i9 mixed with the concentrate obtained~
The resulting mixture amounting to about 9000 liters con-tains about 3.22 ~ casein 0.64 ~ protein 4~68 ~ lactose 0~70 ~ salts 9.24 ~ total solidsO
c) Ultrafiltration o~ Mixture The resulting mixture is then subjected once more to ultrafiltration under the above-mentioned conditions to obtain a concentrate which contains, e~gO, approximately 5.00 ~ casein 1.00 ~ protein 4,65 !~ lactose 0.70 '~ salts 11~35 ~ total solids.
The filtrate is also stored~ 5800 liters concentrate and 4200 liters ~iltrate are now available~
d) ~emoval of Water Water is then removed from the concentrate at a temperature below 65 C by vacuum evaporation or reverse osmoC;iS or the like until the concentrate contains approximately 7~;2 6030 ~ casein 1026 ~ protein 5.86 % lactose 0038 % salts 14 . 30 % -total solidsO
About 4600 li~ers concentrate and 1~00 liters of a dilute -fraction were obtained~
e) Repeated Ultrafil-tration To promo-te a sub~equent th~rmal sterili~ation, the concentra-te obtained in a quantity of about 4600 liters is again subjected to ultrafiltration so that 3000 liters concentrate are obtainecd, which contain about 9~65 ~ casein 1,94 ~0 protein 5,85 ~ lactose 0.85 ~ salts 17.69 % total solids, and 1600 liters filtrate containing 0.2 % protein 5,9 % lactose 0.9 ~0 clalts 7~0 % t.otal solicls~
f) Backm;xinq These 3000 liters concentrate are then mixecd with the dilute fraction obtained by the re~oval of water~
The resulting mixture amounting ~o 4200 liters contained - 12 ~

6.89 ~ casein 1~39 % protein 4020 ~ lactose 0~61 ~ salts 13.09 ~ total solids~
In that mixture the protein has such a microstructure that a heat treakment will not xesult in an as-boiled taste, in caramelizing, in Maillard reactions, and in a d~crease of the stability of protei.nsO
The rem~;ning dispersed subs-tances were obtained with such microstructures that -they cannot produce undesired results in combination with protein or as independent structures during the heat treatment~
~ s a result of the altering of the microstructures of tha individual systems, the system can be sterili2ed at temperatures which are much lower than those used for an ultrahigh-temperature heat treatment~
g) Heat Treatments of Diffarent Fractions For this reason it is proposed in accordance with the invention that the at least two fractions obtained in the process are separately heated at temperatures up to ~5 C.
h) Second Backmixing The two fractions are then mixed when they are still hot or after they have been cooled. The resulting end product is stable and has the original compositionO
Duri.ng the several process steps, the microstructures are influenced as follows a) Production of a Preconcentrate By the pretreatment of a partial quantity by a 7~;~

separatirlg process consisting here o~ ultrafil~ration, -the protein con-tent is increased and the contents of lactose and salts remain substant.ially unchanged. This is appar~nt upon a comparison of the composition of the staxting milk with the composition of the preconcentrate~ As a result, the ratio of the lactose and salt con-tents to the protein content is decreasedO As the system was originally in a state of an unstable equilibrium regarding the relati~e water solubilities of the microstruckures, the product.ion of the preconcentrate makes more water available for t:he protein so that protein microstructures which had adapted in size to the de~iciency of water in the starting material can now change~
As the protein struc-tures are polydisperse in -the starting material, the preconcentrating -treatment results in more uniform structures having substantially uniform properties.
b) Preparation of a Mixture The mixing of the preconcentrate with the rpm~ining starting material increases the quantity of water which is available for the total protein so that the mere mixing results in more uniform protein structures havins more uniform proper-ties.
c) Ultrafiltration of Mix-ture As a result of the pretrea-tment~ the cles.ired changes in properties can be much more easily efEected by ultrafiltra-tion. Protein microstruc-tures can now be changes in various ways, depending on ~he nature and direction of the ultrafiltration~
In the presen~ example the protein structures are first reduced in siæe un-til they have all a uniform small size~ The succaeding removal of wat~r (step d)) and the second ultrafiltration then xesult in a u~ifoxm increase in size ancl in a stabilization of the states oE equilibriumO
As a r~sult o., the Eirst backmixing (step f)) eflectec~ by an acldition of water having th2 properties of a di.stillat, the protein microstructur~s ha.ve a high degree of freedon1 of independen-t movemerlt so that a stable e~uili~rium and a high thermal conduc~ivity are obtained~
For this reason that ~raction can be heat-treated without det ' t-erlora 1011., The second fraction (~iltrate) is substantially f.r~e from protein and the dispersed substances contained therein have such microstructures that the :Eraction will ~ot de-ter~orate in a ~eat traatment as there can be no browning and no Maillard reactionO
The sterilized, stabla product ob-tained by the second ~ackmixing has not been subjectad to an ultrahlgh-temperature heat -treatment and for -~his reason is superior ~o to conventional sta~ilizad milk as regarc~s nutri-tion physiology and ~lavorO

2~ Production of Cheese Cheese .nade by conventional methods has a high case.in content, a low protaiIl content, and ralatively low contents of lac-~ose anc'' salts.
In -the procluction of, e~g~, curd by conventional processæ.s, the antire system is subjact~c'. to microbial souring~ ~if.icroorcJanisms are adcled to milk at suitable tempera~ureC; ar.d Eerment part o:E .h2 lactose to lactic 39 ~ci~.

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Tll~ resultiny lactic acid transforms the casein from a water-soluble s~ate to a water-insoluble stateO The prot~ remains water~s31uble~
Suitable ~epara-tillcJ proc~ssec are then carried out to remove a large part of the aqueous phase an~ o~ -the subs~ances dic;sol~Te~ tller~irl~ One OL the substances clisperseA
in tlle milk~ nan1ely, casein, is recovered irl a relatively higll concentra-tio~.
Tnat process has the ~ollowing disa~van-tages:
1. Whereas only one o~ tlle subs-tances dispersed in milk is to be -treated and recovere~, all otller substances dispersed in the rililk musc be proc~ssed too~
20 Whe~ proteiIls~ which are of high bioloyical value, cannot be recover2dO

3. The process requires expensive e~uipmant and a higl ~nergy consumption because all disperssd subs-tances must initially be processed.
~1. The process pollut~s -the environment because the whey must be disposed of.
In view o~ these disadvantayes, therMal pretreatins processes or additional proccsses hav~ been proposed, which have been disclosed in Ge~rma1l Opened Applications 27 ~ 105, 25 03 840 and 25 45 847 and serve to increase the content o~ the valuable whey proteins in the curd, Other processes, which have been ~isclosed in German Paten~ Publication 20 65 974 and in Britisll Pa-tent Speci~icatior~ 9~37 and in which the protein content o:E the sweet milk is increased by sui~table ~epara~tin~
processes, such a5 ul-tra:Eiltration or ultra:Eiltration and washing, whereafter the milk is sou.recl and/or treatecl - 1u ~

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with enzylnes and a coupling product i.s not ob-tainedO
In the other processes, described in Gerr.lan Openecl Applications 27 4~ 53S ancl 22 11 737~ sour milk or partl-y sourecl milk is subjected to ultraEiltration or washed with water during ul-~rafiltratisn~ The milk rnay be evaporated be:Eore or after the ultrafiltrati.o~O
It is an ob~ect of all these processes to increase the protein conten^t i.n relation to the collten-ts of the othex substancPs dispersed in the milk because it is believed that the renlainincJ dispersed contents will recluce the quality of th2 end productO
All these processes have the disadvantage that uncontrolled changes of the proportions are effected reyardless of ~e changes of states of equilibri~n and without an alte.ration of the microstructures o dispersed substances~
For ins-tance, preconcentrated milk can be used but a spe~ific concentration has not been stated, or the water can be removed after the ultrafilt.ration regardless of previous drastic changes of properties of dispersed substances~
All -these processes result in a formation of bitter substances and in undesired jelly structures, in poor hydrophilic properties and in a product which quickly deteriorates in sensorial qualitiesO
It has been founcl that these undesired results are due to -the uncontrolled chanyes of the microstructures of the dispersecl substances rather than to the proportions thereofO
For this reason/ known sepaxatiny processes are used in accoxdance with the invention in o.rd~r to ef:Eect - 17 ~

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a con-trolled alteration of the micros~ructures of the dispersed subscances rather than Eor a mere change of the propor-tions oId~persed subst~ncesO
It has been found that any alteration of structure will result also in a change in propertiesO
By the use of systen1atic~ controlled separati~g processes in accordance with the inventionc controlled, desirable changes in properties can be ef~ected in accordarlce with khe invention.
It has been found. that, e~gO~ a bitter ta~te is due to a hydrophobi~ property of dispersed substances~
For instance, an indiscriminate preconcentration of milk by an evaporation of water be~ore ultrafiltration will result in a de~iciency of water for all dispersed substances, which are present in a watar-soluble form. As a result, the structures of all dispexsed substances wil].
be altered~ For instance, casein combines with salts and lactose~ ~ighly hydrophilic substances are bound~ The surface area of casein is increased; the water re~uire-ment is reduced~
When that indiscrirninate removal of water anduncontrolled alteration of structure is succeeded by an indiscriminate ultrafiltration, water as well as lactose and salts dissolved in said water will be removed from the milk Th~ remaining protein concentrate will assume a new, uncont.rolled equilibrium owing to the presence of an excessive quantity of water so that structures will disintegrate in an uncontrolle~ manner and h~7drophobic properties will become eff2ctive and will resul-t in hydrophobic conglomera-tes so that the e~d product will have a butter ~aste~
That undesired change in properties will be increased iE water is added during the ultrafiltration in order to increase the protein content relative to the con-tents of the othe.r dispersed substances.
If an indiscriminate ultra~iltration is succeeded by a removal of water to obtain a final concentrate having a required solids content, the protein structure will disintegrate as has been described he.reirlbeforeq The previously latent hydrophobic properties are activated and now repel waterO ~hereas a subse~uent removal of wa~er regardless of the microstructures which are present will result in a rebuilding o certain protein structures, highly hydrophobic structures can no longer he encapsulated~ The resulting products have also a strongly bi-tter taste~
The solubility of sal~s will be improved by a presouring or partial presouring o~ milk~ Salts which have been combined with proteins are removed from such compounds~ A subsequent ultrafiltration will increase the salt content o~ the filtrate. This results in an uncontrolled disintegration of the protein microstructures with a risk of a development of hydrophobic properties.
An indiscriminate removal o:E water before or after ultrafiltration resul-ts in undesired influences on microstructures. ~e souring serves only to change the proportions o~ dispersed substances~
Any processes which serves only to chancJe the proportion~ oE disabled substances will inevitably result - 19 ~

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in uncontrolled and uncon-trollable charlges or the structures oE dispersed substances, i.e., in en-tirely uncontrolled an uncontrolla~le changes of the properties o.~ the dispersecl substancesso that a controlled end product cannot ~e obtained in this mannerp The i.nvenkion will now ~e explained wi~h reEerence to the production of ~resh cheese and cheeseO It will be pointed out that by the selective use of ]cnown separating processes, microstructures can be in-fluenced that a development of hydrophobic properties resulting in a Eormation of bitter substances will be avoidedQ
A) Milk or the like, which may be provlded with any additives that may be required~ is evaporated to remove about 10 % water~ Very little energy is required ~or such evapora-tion~ The protein microstructures are increased in sizeO The structures oE the salts and of lactos~ are so altered that they can be dissolved in less water. The resulting structures permit a succPeding ultraEiltration to be carried out with an optimum efficiency oE the ultraEiltration plant becaus~ there is no danger tha-t the altered microstructures may clog the membranesO
By the ultrafiltration, the microstructures are altered so that the protein particles hav~ a smaller, but uniEorm size~ For -this reason -the retentate discharged Erom the ultraEiltration plant is immediatel~ ~vaporated once more. As a result~ protein structures have a uni:Eorm small size are uniformly increased in size. (The firs-t evaporation has resulted in a noIl-uniform increase in size of the protein structures~) The ~rotein concentrate discharged from the ~9~7~2 evaporatin~ process is subjected to another ultrafiltration process until the composition has beerl obtain~d which corre.sponds to an optimum cheese jelly structuxe.
Compared to the state of the art, that procedure affords the su~stantial advantaye tha-t all separating processes are carried out in the range of optimum efficiency, so that considerable energy can be saved~
the quantity of permeate which becomes available is decreased by on~-hal-E or two-thirds compared with the conventional technolo~y, and -~he sizes of the protein structures can be SQ contxolled that a succeeding souring or rennet process will result in a jelly which is ideal for the type of cheese to be madeO
In a special embodiment of the process, an ov~rconcentrati.on may be eff~cted because all separating processes are carried out at optim~ efficiency so that that portion of the permeate which becomes available in such operations can be cycled and no pollutiny liquid is to ~e disposed.of.
Any pe-rmea~e which becom~s available can be electrodialy~ed in -that the salts of the permeate are introduced into the concentrate before the last evaporating stepl This practice affords th~ advantages that the ~ntire salt content rPm~; n.~ in the cheese and that the ~uffering capacity of the concentrate and the microstructure of the protein can be adjusted to suit spec:ific types o~
cheeseO
Such procedures permit the preparation of par-tial or hiyh concentrat~s for an end product consisting of soft chees~/ cutable cheese or hard cheeseu This is not possibl~
in the state o~ the ar-ta ~ 2.1 In such processes the a.ci.d and salt contents which arerequired in the cheese of the type desired can be adjusted in the liquid raw product (concentrate)0 Such concentrate contains the dispersed substances in same proportions and structures as in the finished cheese but still in a water-soluble state~
This concentrate is then transEorme~ from a liquid state to a semisolid or cuttable state in a single process step, e~g./ by an enzymatic process t S that the process steps previously requixed, which are complicated and time-, material- and energy~consuming and pollute the environment, are entirely eliminated.
These proc~dures accordiny to the invention can be applied to the production o~ all milk products which can be made. In the production of a given milk product, the micro- and macrostructuras and the states of equilibrium which are required in -the end product are ascertained first and these conditions are then adjusted in the li~uid starting raw material by separatiny pro esses carried out in seri~s or parallel~ In the preparation of some products, li~uids which have been separated are added during the process or at the end of the process in an unchanged or changed form and additional quanti-ties may alos be added in controlled proportions if this is necessary tQ form re~uired microstructures.
Individual fractions which become available in the separating proc~sses and may consist of whey proteins, lactose, salts of milk, lactic acid, water ~tc~ ~ay be subjected to a separate treatment/ for instance, a temperature treatment, a further æparation, a separate structure-- 22 ~

changiny treatmen-t, etc~ and may then be processecl separatel~ or be added to -the startillg raw material at the same or di~erent temperatur~s~
B) 10,000 liters milk are subjected to separating processes for alt~ring the microstructuresO The milk contains 9~0 ~ solids and 91 % watexO
Polydisperse pro~ein struc~ures are contained in the water.
a) First SeparatiIly Treatment 2000 liters mil]c are treated at a temperature below 65 C fora removal of water by reverse osmosis or evaporation until a water content of 8~ ~ and a solids content of 12 % have been obtained~
This treatment changes the protein microstructures, which adapt to the lower water content~ The proteins increase in adaptation to the lower water content~
Without additional measures, -these structures would become hydrophobic in a souring process in which substances having a high water requir~ment (lactic acid) are formed or addeda b) First Dilution For this reason the resulting concentrate ~s diluted with additional ~000 li-ters milk~
2000 liters milk containiny l2 % solids and 88 % wat~x dilutecl at a temperature below S5 C with 2000 liters milk con-taininy 9 % solids and 91 % water~
The resulting mix-ture oE 4000 liters mil}c contains 1005 % solids ancl ~ ~ wat~r.
The larges~ casein structures present disintegrate to form somewhat smaller struc~ures, Casein structures of - ~3 -~07~12 edium and small size are not aEfected~
The smallest casein structures in the startin~
mil~ are incr~ased to an interrnediate size.
The separating and mixiny steps result in more uniform casein structures without a developmeIIt of hydrophobic properties.
The protein structures of ~he resultiny system are not sufficientl~ stable in a souring process.
c) Second Separatinq Treatment The r,lixture described above, which contains 10.5 ~ solids and 89 ~ water, is now subjected to ultra-filtratiorl at a temperature below 65 C, preferably 60 C, until the concentrate contains more than 11 %, preferably 13~56 % protein.
A concentra-te is obtained in an amount of 1333 liters and contains 13.56 % protein, 21 ~ total solids and 79 % water. The permeate contains 70~ % solids and 92.d ~ water~
The removal of salt and lac-cose at the beginning of the ultra~iltration results in a disin-t~gration of the largest casein structures present to struc-tures OL
intermediate size~ The smallest casein structur~s which are present ayglomerate tD form larger structuresa It is apparent that the second separating treat-ment xesults in still more uniform protein structures.
But owing co the shortage of wa-t~Qr, a succ~eding souring process would still give rise to hydrophobic properties.
d) Second Dilution 1333 liters concentra-te are diluted at a tempera-ture below 65 C, preferably 60 C with the remaining - ~4 -~v~gz 6000 liters startirly rnilk~ e resulcing mixture has a pro-tein con-LQi~c of rn.or~ ~han 5 ~0, preferably 5~25 %, a solids conteI~t of 11.2 ~l and a water conterlt of ~8.8 %.
As a resul.t of the separatirly processes and diluting steps carried out, the initially polydisperse proteiIl structures have been transformed to substalltially monodisperse structures~
ThQ su70stantiall~ monoclisperse protein structures must be furtller stabilized. l~his is effected as follows:
e) Third Separatinq r~reatment 7333 liters of the mixture obtained in step d) are subjectdd at 60 C to another separating process, such as an ultrafiltration.
The resulcing conGentrate amounting to 3080 liters contains 12.5 protein, 1~ ~ total solids and 82 % waterO
This concentrate contains stabilized, su~stantially : monodisperse prot~in structures which even in a succeeding microhial souring processes or after an addition of acid will not give rise to hydrophobic properties.
The aroma can be further improved by a moderate.
: f) Third Dilution with starting milk to a final water conten-t above 82.oo %, preferably 82,3 %. 3080 liters concentrate cont~;ning 82 water are diluted with 500 liters sta~ting milk to obtain a final water content of 82.28 ~0.
That final concentrate is excellently suitable for th~ production of curd.
The protein s-~ruc-tures thu.s obtairled can ~e further stabilized in that the Einal concentxate is hea~ed a~ove 85 ~ and held a~ the resulting temperature for more than 2 minutes, ~refera'oly 7 minuLLes.

~1~07~

Such concerltra-tes ma~ also be used for tln~
production of soft chees~, cuttabl~ chaese or hard cheeseO
In ord~r to obtain ~icrostructuxes having the xequir~d properties in an aqueous dispersion, the ql1antity of milk used as a ~iluent in the third dilution should amount to at least one-half of tll~ quantity of ~he concentrate to be diluted.
3080 liters concentrate which contain 1205 %
protein arld have a solids content of 18 % and a water content of 82 % are dilutecl with at least 15~0 liters milk which contains 3.4 % protein, 9 ~ total solids and 91 % water.
The resulting mixture amounts to 4620 li~ers and contains 9 a 46 ~ protein, 15 ~ total solids and ~,5 % water.
That mixture is subjected to another separatiny treatment ~ultrafiltration) to obtain 2300 liters of a concentrate which contains 18.9 % protein, 24~4 ~ total solids and 75.6 % water.
This concentrate is diluted with twice its quanti-ty of starting milk~ 2300 liters concentrat~ +
4600 liters milk = 6900 liters of a mixture cont~;n; ng go56 % protein, 14.13 % to-tal solids and 85087 % watera This mixture is subjec-ted to ultrafiltra-tion at a temperature of 55 Ca The result.iny concentrate amounting to 2750 liters contains 21.5 % protein, 26 5 % total solids and 73.5 %

watPr ~, rThe properties of ~he microstructur~s o~ the dispersed substancas of said concentrate in a water-soluble state will not be adversely a~fected by an enzymatic treatmen-t and by souring and salting processesO

~g~

The concen-trates can be mixed with cream or crPam powder, particularly for the pro~uction of fat~y cheese .
The properties o-f the protein structure~ can be improved, particularly for the production of cuttable cheese and hard cheese, if th~ last sepa.rating process is succeaded by a removal o~ water ~o a water co~tent which is 2-5 % lower than the legally prescribed water content.
It will be particularly desirable to e~fect before the last separating process a modera-,e dilution with milk and/or a protein solution and/or a whey protein solution.
The dilu~nt used may also contain fa-t.
2750 liters concentrate containing- 2105 ~ protein, 26.5 % total solids and 73~5 % water are mixed with at least 500 liters of protein solution cont~;n; ng about 6 protelnt about 7 % total solids and 93 % water.
The resulting mixture amounts ko 3250 liters and contains 19.12 ~ protein, 23.5 % total solids and 76.5 %
waterO Water is ~hen removed from the resulting mixture until it has a water content of about 50 %.
From such a concen-trate in which the dispers~d substances, particularly the proteins, have substantially monodisperse structures, water can be removed without a deterioration of said structures. Succeeding enzymatic processes will be eLfected in the range of optimum activity and will not result in a deterioration, particularly in an activation of hydrophobic proper~ies.
I~ such concentrat~ is to be aromatized immediately in a sweet range (pH value & to 608), eOg~, by salting~ khe permeate which becomes available is o~

subjected to electrodialysis and the r~sultins brine is concentrated and added to the concentrateO
rrhe water-soluble microstructures thus obtain~d can be used in a desirable process of producing~ eOg., cheese~
By an addition of culture concentrates or edibla acids, the ~inal concentrate is adjuste~ to a pE value which is rec~uired for the dcsired cheese, e~g~, 407 or soft cheese~ 501 .Eor cuttable cheese or 504 for hard cheese.
The protein structures which are present will not permit a ~rmation of gel by t'nis treatment.
The required salt content of, e.g., 2 to 5 %, is : then adjusted~ microorganism cultures and/or enzymes are admixed, and the concen~rate, which is still liquid, is fllled into containers.
The cheese will then coayulate and fully ripen in the packages~
This constitutes an entirely continous process of producing cheese.
In modifications of the process according to the inventlon, separating processes effecting a controlled alteration o microstructures of dispersed substances in polydispers~ aqueous systems can be used in a controlled manner ~o change ~he proper~ies of the disperse~ substances in a desired manner while the dispersed substances ar~
still water-soluble~
In thi.s manner, foodstuffs of li~uid, pasty and solid consistency can be made from poly~isperse aqueous systems by processes which are energy-saving, economical and friendly to the environment.

- 2~ -~o~

3) Pro~uc~ion of Saur Milk Products Sour milk proclucts distinguish by the nature of -the jelly structure oE protein. ~n -their production, protein is transformed from microstructures to macro-structuresO Thes~ jelly structures nust be strongly ~ydropllilic~ For this purpose, their voids must be as small as possible so that -they contain no interstitial waterO In an idQal j~lly structure for sour milk products, water is chemically combined or contained in capillariesO
In the process accordiny to the invention the formation of such a jelly structure can be influenced in that the rllilk is treated to alter the microstructure of the dispersed substances.
Milk is Eirst evaporated~ As a result of this removal of water~ the structures of the dispersed substances adapt to the reduced water content. Salts are incorporated in protein structuresO Protein particles increase in size although the polydisperse state is maintained, with larger particle sizes.
The ratio of ionodisperse salts and of salts combined with proteins is changed toward thQ latter~ The form in which lactose is dissolved in water is changed tooO
The resulting state is by no means suitable for the formation of the jelly structure described above.
For this reason another separating process, e~g., an ultrafiltrationl is carriecl out in accordance with the invention~
This separating process results in more uniorm protein scructures although this is effected in another size range than in the previously describecl process of ~30~'9~

producing certifiedm11k. The resulting protein structu.res are smaller than ihose in certified mi~k so that their surface area is larger than in the s-tartiny milk.
Ideal conditions ar~ thus obtained for the formation of tha above described gel structures in a subsequent souriny processO Such ideal conditions cannot be obtained by processes known in the art.
With the controlled microstructures obtained according to theinvention, -the solids content can be lower than in the starting milk so that it is possible to add not only thep~viously separated liquid but additional li~uid, e~g., in the form of whey or ultrafiltrate or the likeO There will be no pollution of the environment by coupling products.
In a special embodiment of the process~ the permeate which becomes available is subjected to ion exchange or eIectrodialysis and is then added to the starting material as a buffer or as a lactose concentrate (which may contain dissociation products of lactose)0 e) Production of Fresh Chsese Fresh cheese has a gel structure which permits part of the original li~uid content to be removed but retains the remaining water~ In the prior art, water is removed in the r~quired amount only after tha gel has formed or water is removed from the milk by ultrafiltration, whi.ch may bs combined with washing, and partial or hign concentrates are produced~
T~ese processes have substantial disadvantages~
In none of these processes is -the formation of a satisfactory jelly ensured4 In the first-mentioned process the nature of the resulting jell~ structures and of ~he souring s~uences cannot be controll~d~ These processes often xesult in a ~resh cheese whic~ is too dry or which loses water and Eor this re~son has an unsatisfac-tory aroma and is not sufficiently stabl~0 In the process involving a removal of filtrate, possibly in combination with washing, more uniform protein structures are obtained but this is effected in a very unfavora~le size range so that the finished product contains sand- or gritlike structures and bitter substancesO
These serious disadvantages are eliminated by the process according to the invention in that the startin~
milk is treated first, e.g~, by evapoxa~ion~ The fo~Dwing changes are effected:
Starting Milk Composition of Milk After Removal of Water Water content91.00 ~ Water content88,00 %
Protein content3.40 % Protein content4~53 %
Lactose content4~70 % Lactose content6027 ~
Salt conte~t 0~8 ~ Salt content 1,18 %
Fat content 0~02 % Fat content 0~03 The protein structures have polydisperse sizes but the protein structures are increased in ~ize~
During th~ subsequent souring processes, the sal-t content of the milk is of essential significance for buffering. For this reason the salt content was adjusted so that this buffering capacity is substantially preserved in a succeeding ultrafiltration.

7~

rrhe removal of wa~er is succeed~d by ultrafiltra-tion, whi~h may xesult in a high concAntrate, although all intermediate s-tates are possible. The high concentrate obtainecl,~.y., by ultrafiltration, has the following composition~
Water contenk81,27 %
proteiIl content110 25 ~actose content6~27 ~
Salt content1~14 %
Fat content 0.07 %
In this process, the total solids content after the second separating process amoun-ts to 18~73 %; -this corresponds to the solids content of fresh cheeseO
The process according to the invention permits the formation of jelly structures which in low concentrates permit a controlled removal of wa-ter and in high concentrates ensures that the souring processes will proceed in an exactly controlled manner ancl will not permit a formation of bitter substances or of sandy, granular structures because the re~uirements for the formation of an optimum jelly for fresh cheese have been met in the starting system while the water-soluble state has been preserved~
Gelly structures having an even more exactly predetermined consistency and buffering capacity can be obtained in that the ultrafiltrate is sub~ected to electrodialysis so that the salts containe~ in the ul-tra-filtra-te are transferred into the low or high concentrates ancl -the final product contains all salts originally contain~d in the milk or more than the original salt content oE the milk (i:E the ~uanti-ty of ul-traf.i.ltrate su~jected to clialysis is incr~asecl)0 - 3~ -7~%

This carlnot be achieved by any of the conventional processes, in which a ma:jor part of ~he salts are removed or even washed out.
5) El;m;n~tion of Undesired Properties in Oriyinal Poly-disperse Ac~uaous ~ystems and Preparation of the System for the Production of Sour Milk Products By environmental influences, by an improper treatment and by influences o~ the food aaten by the animals, substances d.ispersed in original polydispersa aqueous sys~ems may be changed in such a manner that it is difficult or ~possible to properly manufacture a product~
All such non-oriyinal constituents axe dissolvQd in water and combined with oriyinal disperse~ substances dissol~ed in waterO
For instance, certain inhibitors are known, which in th~ production o-~ ~oods tha~ are to be soured by microbes interfere with or entirely inhi~it the action of microorganisms~ Such aqueous polydisper~e systems give rise to high economic demage~
For this reason the invention as applied, for instan~e, to systems which contain inhibi~ors proposes tha~ the mlcrostructures of the dispersed substances which are originally present and have ~een altered by inhibitors should b~ influenced by separating processes in such a manner that the effects o undesired changes in properties will be eliminated and required properties will be prepared at tha same time7 A portion of an inhibitor-containing milk is )75~

ultrafilcer~d at a -te~ erature above ~5Q ~, particularly ~ ~ Parc of th~ liquid whic'n is discllarged, particularly S0 % of the separated li~uid which is disclllar~ed, is im~lediately added to tha concentrace ~ormecl in tlle second stag~ of all ultra~iltra-ti.ori pla.nt~
'~hat operatiorl results in an al~eration of the micrvstructur~s of casein ancl protein and a libe.ration in-to thc aqueous phase o, inhi'~itors whicl~ Jere combined with the original structuresO
A ldajox part oi tha now wa-ter-soluble inhibitors contained ill the s~cond mixture are removed in th~ second staye and are included in the permeata whic'n is discharged~
Part of the retentate obtained 'cogetll~dr witll s~arJcing millj~
that has been diluted with watex (at least 9 parts of milk to 1 part of ~a-tar) i5 supplied to che :Lirst stage o,F t~a ultrailtration plant and is ultra-Filtrated once more so tha-t microstructures of dispersed milk su~stances which a.re -Eree from inhibi-tors are continuously r~covered in the discharged part of -the retentate and the demaged microstructures which have not yet been traated axe reganerated con~inuously.
As a result, the microstructures O.L the dispersed substances cont-ained in the discharged part of the retentate are alr~ady in a stat~ which corresponds to original states~
Obviously such a regeneration can also b~ carried out when the starting raw ~laterial contains other non-origi~al water-soluble dispersed substances, e.g., from the enviromnent~
The regenerated part is now to be ~rocessed further to ohtain sour milk products~

~ 34 -~19()~Y12 Sour n~ilk prodllcts ~riepencL on gel-~ormincj properties, e~g., of dispersed milk subs-tances. It is important that ~he ~1 is no~ Eormed in an uncontrolled manner at ran~om i-)ut a jelly is formed which con~alns little void water an~ much capillary water and particularly hydrate water a For this reason ~he w~ker-~olub]Ae micro~truc~ures must be prepared for the aevelopment of the gel-orming property of ~otein~ This has not be~n possible in accordance with the state of the art.
For this reason it is proposed b~ tne invention to dG~ e.g,, the mi`lk having microstructures which have been corrected by the process described aboveO At least 20 % of the milk to ~e processed is subjected to a process by which water is removsd. 10 ~ o~ ~he water conten-t are removed at temperatures below 65 C or preferably at Additional 20 % of the milk to be processed are ultrafiltered at the same time~ The ultrafiltration is continuad until 30 % retentate and ~0 % permate have formed. The product from which water has been removed is then mixed with the retentate obtained by ultrafiltration.
The mixture is ultrafiltered once more at a -temperature ofS5 C. During the ultrafiltration of the mixture, the remainder of th~ pretreated milk at a temp~rature of 65 C is continuously fed to -the ultra-filtration so that the final concentrate contains at least 1~ ~ solids~
The mllk which has thus been treated is Eree from inhibitors and has protein microstrllctures which are ~ )7 ~9 water-soluble and ~ermit the iorma~ion OL an optimum j~lly O
6~ Procassin~ of Recombine~ Systems Recombined sys~ems are systems which have been racovered in that substances which have been dried, for instance, are redissolvedO
Pxocedure:
Milk powder and/or pro~ein powder of animal or vegetable origin are mixed witll wa~er to form an aqueous polydisperse system, Approved addit.ives, sucll as salts, ~inders, Pn~ymes, sweetening agents etc.~ which are re~uired may be admixedO ~ecause ~he states of solution in such a sy3tem are mainly obtained at random, it is very difficult to process the system so as to form produc~s~
For thisre son the invention provides that such a random agueous system is treated to form concentrate which ha~ contxolled microstructures and can ~e processed ~urther.
1000 liters OL a recombined starting solution are Eirst hyparfiltexed at a temperature below 20 C, mainly 15 C, until about 10 % of the carrier li~uid have been removed~
One-half o~ the concentra-te is then mixed with additional 1000 liters of the recombined starting li~uid and the mixture is ultrafiltered at 55 C until ~00 liters concentrate hava been obtained.
Vuring the ul~rafiltra~ion, the remainder left af-ter the hyperfiltration is continuously supplied to the ultrafiltration, 0~2 " .

The concentrate which becomes available is mixed with the carrier liquid obtained by the hyperfiltration. The resulting concentrate can then be processed further to form, - e.g~, evaporated or sterile milk. In this special case the permeate discharged from the ultrafiltration step is electro-dialyzed and the resulting liquid, which is substantially free from salts, is admixed to the concentrate that is to be pro-cessed further to obtain evaporated or sterile mi1k.
The product now obtained is excellently suitable ~or making evaporated or sterile milk without an occurrence o~
Maillard reactions or a precipitation of proteins and without ' a tendency to thicken subsequently.

~f,,

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for standardizing the structure of the proteins in milk, comprising: a) withdrawing a portion of the milk and increasing the concentration of protein constituents in said withdrawn portion by ultrafiltration by a factor of at least one-and-a-half; b) mixing the concentrated portion with the residual portion of the milk; c) concentrating the resulting mixture by ultrafiltration by a factor of at least one-and-a-half; d) removing a portion of the water from the resulting concentrate by vacuum evaporation or reverse osmosis at a tem-perature below 65°C; e) subjecting the concentrate obtained in step (d) to ultrafiltration; f) mixing concentrate obtained in step (e) with the water obtained in step (d); g) subjecting the mixture obtained in step (f) and the filtrate obtained in step (e) to a separate heat treatment at a temperature of up to 85°C;
and h) subsequently remixing the mixture and filtrate of step (g).

2. A process according to claim 1, wherein the protein concentrate in step (a) is increased by a factor of approxi-mately 2.

3. A process according to claim 1, wherein the several separating steps and the addition of liquid are carried out at different temperatures.

4. A process according to claim 1, wherein the pro-cess steps are effected continuously.

5. A process according to claim 1, wherein step (d) is carried out at a temperature of 60°C.

6. A process according to claim 1, wherein the separ-ate heat treatment of step (f) is carried out for at least 2 minutes.

7. A process according to claim 6, wherein the separate heat treatment of step (f) is carried out for at least 7 minutes.