CA2116521A1

CA2116521A1 - Buttermilk curd based cheese process

Info

Publication number: CA2116521A1
Application number: CA002116521A
Authority: CA
Inventors: John Lelievre
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-02-18
Filing date: 1994-02-18
Publication date: 1995-08-19

Abstract

A process for producing a cheese comprising the steps of preparing a concentrated buttermilk having a pH of about 6 and heating same to a temperature of about 35 °C. An effective amount of soluble calcium is added to improve coagulum formation and the buttermilk is inoculated with a thermophilic starter culture. Then an effective amount of a coagulating enzyme is added to the buttermilk. Once the coagulum has reached the desired consistency, water is added to the curd at an elevated temperature, either before or following cutting, and then the curd is stirred in the presence of heated water in an amount effective to lubricate the surfaces of the cut curd, in order to thereby facilitated the stirring and heat transfer to the curds and ultimately to improve the syneretic expression of whey from the curd.

Description

21~ 21 -FIELD OF THE INVENTION:
The present invention relates to a process for the manufacture of buttermilk curd based cheese, and in particular to a process therefor that is carried out at elevated temperatures.

R~ ROUND OF THE INVENTION:
Most conventional types of cheese are fermented products produced through the combination of: the curdling action of a proteolytic enzyme (typically rennet - an enzyme complex found in the stomach of young mammalian animals); and, 2) the pH reduction that is facilitated by the acidic metabolites of "lactic" microorganisms. The resulting product is a curd whose major protein constituent is casein, the predominant protein species in mammalian milk. Additionally, cheese typically contains some of the minerals and most of the fat that are originally contained in the milk at the outset of the cheese-making process. The balance of the milk components becomes a liquid phase by-product following formation and separation of the curd. This liquid phase is known in the art as "whey", and contains the other major protein species of milk - whey protein. In any case, whey characteristically contains not only the indigenous milk proteins and minerals that are preferentially soluble at the relatively acid pH that typically manifests under conventional cheese-making process conditions, but also most of the lactose contained in the milk.
In general, the type and composition of a cheese product depends to a large degree on the starting material, be it milk or a milk-cream -mixture, or at the other end of the spectrum, even skim milk, and the cheese production process.
Curdling almost invariably includes souring of the milk, usually through in-situ acid production by Lactococcus cremoris or Lactococcus lactis, although addition of exogenous acids, (typically food grade organic acids), is not unheard of. In some cheese manufacturing the curdling is entirely a function of acid souring of the milk, with no rennet or other added enzyme involvement.
In still other cases, various microbial proteases are substituted for the more traditional rennet.
After the curdling operation is sufficiently advanced (and indeed completed), the coagulum must be separated from the whey, in order to produce a structurally robust, substantively dewatered curd, having a firm, and almost rubbery character. The realization of this end typically requires the cutting of the curd to facilitate the "syneresis"
of the interstitially-trapped whey from the body of the formed curd.
The cut curd is gently stirred to help prevent the curd cuttings from sticking to one another, or settling and "matting", either of which would otherwise interfere undesirably with the syneretic loss of whey from along the cut surfaces of the curd.
Buttermilk is a by-product of butter manufacturing. Milk is churned to produce a mechanical inversion of the fat-in-water emulsion which is characteristic of milk, into a water-in-fat emulsion. As the working of the inverted emulsion progresses still further, more and more of the liquid fractions of the milk are occluded from the water-in-fat 2~521 `_ emulsion, until finally, butter is formed. Butter typically comprises about 80% butterfat, 1 to 2% and preferably 1.3 to 1.5 % non-fat milk solids, and 0 to 2 % salt. An exemplary butter product might comprise about 15.8 to 17.2% moisture; 79.5 to 80.5% butterfat; 1.7 to 2.0% salt;
and, 1.3 to 1.7% milk-solids-not-fat. Buttermilk on the other hand is made up of the residual milk components that are left behind after the butter is formed. Buttermilk typically comprises 7 to 8% total solids and about 0.5% butterfat. Buttermilk can also be condensed to increase the proportion of constituent solids, if desired, and/or can be supplemented with buttermilk powder as might variously be required to balance the moisture, fat and dairy non-fat solids in any given formulation.
Separated, fresh buttermilk is most typically condensed by evaporation thereof, with the evaporation being carried out in an evaporator at an elevated temperature for as short a time as is reasonably consistent with avoiding off-flavour development due to over-heating. A condensed buttermilk product following evaporation might comprise about 20% (say 20 to 23%) solids; have a pH of between 6.6 and 6.8, (titratable acidity at 9% solids of 0.11 to 0.15%); a maximum of 3.3% salt; a maximum of 2% fat; and should have a clean sweet flavour and odour.
From the commercial perspective buttermilk is a relatively less valuable commodity as ranked amongst various other dairy materials. In many dairy production facilities, buttermilk by-production either volumetrically exceeds the requirements in existing markets for 2 1 l~21 ._ buttermilk products, or at least is available in such quantity that its economic value to the producer is very depressed. In general, buttermilk does not lend itself to any particular application in producing value added products. This is not to say that attempts have not been made at utilizing buttermilk in the search for such value-added product applications. For example, buttermilk has been offered up as a possible constituent in cheese manufacturing, for use therein as a standardizing additive to balance the milk casein to fat ratio for cheese formulations in what otherwise amounts to conventional cheese manufacturing processes.
According to SU 1611314 dated 90/12/07, discloses a process in which buttermilk is pasteurized, cooled and fermented. The fermentation involves the addition of a "fermenting agent" and "coprecipitates (added in amounts of 10 to 15 %) to produce a "pot cheese".
SU 1274666 dated 86/12/07 relates to a coagulated protein curd made form a second grade cheese, a bacterial culture, CaCl2, and an enzyme.
More particularly a buttermilk is pasteurized at 70 - 74 oC and cooled to between 40 and 70 oC. Optionally, the buttermilk can be mixed with skim milk at ratios of 1:1 to 8:2. The buttermilk acidity is adjusted, by fermenting the buttermilk with 0.2% of a pure lactic acid culture, to between 17 to 23 deg.T. The buttermilk is then heated to 38 oC and a further 0.8 % of the same culture is added, along with 40% CaCl2. The mixture is left to coagulate, then stirred for 10 minutes and heated to 43 oC. After a second heating the bulk is kneaded for 15 minutes, and the resulting product is ready for moulding and pressing.

SU 405521 dated 74/04/04 discloses a process in which skim milk is pasteurized at 75 to 80 oC, then cooled to 30 to 32 oC and inoculated with lactic acid bacteria. The resulting curd is cut into cubes and mildly heated, then the whey is separated and buttermilk, heated to 92 to 95 oC, is mixed with the cut curd. The protein that is contained in the buttermilk is coagulated out, and the whey from the buttermilk is separated as far as possible without extraordinary measures. The remaining curd is compressed (to release the balance of the excess whey that remains more stubbornly entrained within the curd) to yield a moisture content of 60 to 68%, whereafter additives such as fat and taste and aroma improvers are added, while the mixture is heated to 70 to 75 oC and intensively stirred.
Experience in this connection, however, has amply demonstrated that buttermilk compositions evidence a marked and inherent reluctance to undergo coagulation. Various examples of disparate and extraordinary processing steps have been embraced in the hope of realizing a firm, self-supporting curd structure. Ironically, even if the desired structural stability in the intermediate coagulum could be realized, the collateral enhancement of the interstitial liquid retention within the stabilized coagulum network would frustrate the downstream dewatering that is so necessary in order to arrive at the desired cheese's final, finished texture.
The problem of forming a firm, self-supporting coagulum as a prerequisite to cheese production, followed by the complications inherent in the successful resolution of that problem during subsequent dewatering of the coagulum, have been significant obstructions to the commercial adoption of buttermilk as a principle component in cheese-making. This continues to be the case in spite of the clear and long standing economic advantages that would follow, were it feasible to incorporate buttermilk in a cheese making process, at significant loading levels. Accordingly, there remains a need in the art for a process which might facilitate the incorporation of significant proportions of buttermilk into a value-added cheese product.

SU~ARY OF THE INVENTION:
The present invention relates in part to a process for setting up the curd coagulum in a buttermilk cheese product. As mentioned elsewhere herein, buttermilk curd formation is intrinsically problematic, and marked by a tendency not to coagulate into a physically manageable, firmly self-supporting coagulum.
The present process entails concentrating the buttermilk. Although concentrating milk in conventional cheese making processes is apparently known, the purpose of doing so in such a conventional cheese making context has to do with either:

-improving the volumetric throughput of a given sized production facility; or, -reducing the amount of whey protein losses from the cheese product.

2 11652 ~

In the presently contemplated buttermilk application, however, the concentration of the buttermilk solids, serves to overcome some of the reluctance of the buttermilk to coagulate, by providing a certain amount of body during gel formation.
It is desirable that undue protein denaturation be avoided during any concentration process. In an evaporation process, this is best facilitated by minimizing the thermal treatment. In accordance with the present invention, this can be accomplished, for example, by heating the buttermilk to a temperature of about 72 oC for a holding period of about 15 seconds. Higher temperatures, say up to as high as 95 oC might be used, provided that the exposure time is correspondingly shortened.
Preferably, however, buttermilk concentration is carried out through ultrafiltration, rather than evaporation. The use of ultrafiltration helps to avoid denaturation of the indigenous milk proteins (in particular, by avoiding formation of intermolecular disulphide bonds between kappa-casein and either or both beta-lactoglobulin/alpha-lactalbumin), and thereby facilitates formation of the coagulum during later stages of the processing. Ultrafiltration also reduces the residual lactose concentration in the final cheese product, thereby more closely approximating the lactose profile traditionally associated with classical cheese archetypes, and collaterally increasing the protein to total solids ratio in the curd.
In any case, the buttermilk is preferably concentrated to about 18%
total solids.
The buttermilk is then acidified through the use of an edible, ~ 5 ~ 1 -preferably organic acid or its equivalent, to a pH in the range of about S.5 - 6.6, in particular to 5.6 - 6.4, especially 5.8 - 6.2, and most especially to about 6. Note that it is also within the contemplation of the present invention to acidify through the use of a starter bacteria culture (such as lactococcus or lactobacillus) to reduce the pH. Dilute lactic acid is, however, the acidulent of choice in this application.
Preferably, the acidified buttermilk is held for a period of time before further processing takes place. Holding for up to 24 hours or more is acceptable, provided all due care is taken to avoid spoilage or cont~rin~tion. In a typical commercial process according to the present invention, however, the acidified buttermilk is held for about 2 hours.
Acidification at this juncture improves coagulum formation in the subsequent processing steps.
Skim milk can also then be added to the buttermilk if desired.
Mixtures of buttermilk comprising preferably up to 50% (but even 60 and at the outside about 70%), skim milk can be accommodated in the practice of the present invention, and still retain a material proportion of the economic advantages of utilizing buttermilk in the production of cheese according to the present invention. It is preferred that the addition of the skim milk does not result in any collateral dilution of the total solids levels of the condensed buttermilk. That being the case, the skim milk preferably has a coagulable protein solids content that is about equal to that of the evaporated buttermilk, and preferably therefore, of about 18% total solids. The ratio of the coagulable protein solids can be as high as 80:20 buttermilk to skim milk.

2 ~

The buttermilk or skim milk/buttermilk mixture, as the case may be, is then heated ~typically to about 35 oC), and supplemented with CaCl2.
Note that the CaCl2 can be added before or after the heating step - the only essential requisite being that the CaCl2 must be added before coagulation of the casein protein, (eg before rennet addition).
The CaCl2 is added in concentrations of greater than 4mM (pref. in the range of 4 - 10 mM). In a typical process herein, the CaCl2 might be added in an amount of 2 to 10 ounces per thousand pounds of buttermilk or skim milk/buttermilk mixture. The divalent calcium ions are believed to be relevant in empirically associated improvements in the formation of the coagulum and especially in remediating effects of prior heat damage done to the buttermilk, which otherwise interferes with coagulation.
Heating of the buttermilk, or buttermilk/skim milk mixture as mentioned above (hereinafter collectively referred to as buttermilk substrate), helps to promote starter bacteria growth.
The buttermilk substrate is then inoculated with an at least mesophilic and preferably thermophilic starter culture, usually at the rate of about 1.5 to 4.0%, (by weight). Although the use of thermophilic cultures is known in the manufacture of the mozzarella cheese, the use of thermophilic species, such as thermophilic Lactobacillus bulgaricus in the context of the present invention serves an entirely different purpose. In the present invention, the need for the thermophilic starter is ancillary to the fact that conducting the "fermentation" at higher temperatures, encouraging syneretic losses once the curd is cut. As a generalization the higher the processing temperature the better the separation of curds and whey.
This is followed by rennet addition, in known manner, whereafter the setting of the coagulum manifests in due course.
Once a buttermilk curd is formed, the curd is cut and stirred to release the entrained whey, but this is complicated by the fact that the cut-surfaces of adjacent portions of curd are not lubricated by autogenously released whey, thereby making stirring difficult.
In accordance with this aspect of the present invention, therefore, there is provided a process for the cutting of a buttermilk based curd comprising the steps of adding water at an elevated temperature to the curd after it has reached the desired consistency and either before or following cutting, and then stirring same in the presence of the heated water. The presence of the heated water lubricates the surfaces of the cut curd, thereby facilitating the "stirring", and ultimately the syneretic expression of whey from the curd. The curd is then heated to 52 oC ~eg 50 to 55 oC), for 60 to 90 minutes or so.
The addition of heated water facilitates stirring without destroying the curd structure during the dewatering of the coagulated curd.
In traditional processing, the cheese is then drawn onto the cheese table, packed and pressed, and then passed to storage, preferably at temperatures of less than 4.5 oC. In more modern processing facilities, the cheese is passed to a draining conveyor, or the like.
In accordance with an especially preferred aspect of the present invention, there is provided a combination of the process steps set out above, for the purpose of producing the coagulum and then dewatering same.

DE~TTFn DESCRIPTION OF THE INVENTION:
INTRODUCTION TO THE DRAWINGS:
Over the course of the following detailed description of the present invention, reference will be made to the accompanying drawings, in which:

Figure 1 is a flow chart outlining in a schematic form, the process steps according to the present invention;
and, Figure 2 is a graphical representation of stylized water loss profiles for a conventional curd, and for a buttermilk curd, respectively.

In accordance with one aspect of the present invention there is provided a process for which raw milk 1, having an acceptable odour, being antibiotic free and stored at a temperature of four to seven oC, is sourced. The raw milk 1 is heated to about 49 oC during the separation of the skim milk. The skim milk is then evaporated in an evaporator 2, under low heat conditions, of about 72 oC with a 15 second holding time. The total solids content reaches about 18%.
Similarly, raw buttermilk 3, being antibiotic free and stored at a 211~521 -temperature of less than 6 oC, is obtained. The buttermilk 3 is then passed to an evaporator 4 and after being subjected to low heat of about 72 oC from a period of about 15 seconds, the total solids content of the buttermilk should be about 18%, (eg about 6 - 7% coagulable protein).
Note that where required by alternative processing conditions, a heat exchanger 5 can be employed to cool the buttermilk. The condensed buttermilk is acidified through the addition of lactic acid to a pH of about 6Ø The acidified condensed buttermilk is then preferably, but not essentially, held for a period of about 2 hours, preferably under moderate agitation in a blender 6.
The acidified, condensed and aged buttermilk is then blended with the condensed skim milk, in a ratio of 2 parts buttermilk to one part skim milk. The blend is then optionally heated in a heat exchanger 7, to about 95 oC and CaCl2 is added at the rate of from 2 to about 10 ounces per 1000 pounds of the blend.
Alternatively, the condensed buttermilk and milk can be mixed, and then acidification can be carried out through the addition of the food grade acid.
The blend is then inoculated with a thermophilic starter culture, such as Lactobacillus bulgaricus, for example, and the rennet complex is added to the blend.
The coagulation process continues in the cheese vat 8, until the desired degree of consistency is realized. Typically, the pH of the product at this point will be about 6Ø The set cheese is then cut.
Cooking of the cut cheese with added water follows, by heating the -cheese to about 52 oC for a period of about 60 to 90 minutes. The predraw elicits about 45% of the whey, typically at a pH of about 5.9.
The draw curd on the table 9 typically has a pH of about 5.8.
Refer in this connection to Figure 2. Figure 2 illustrates the dynamics of whey loss from conventional cheese curds, following cutting.
The rate of loss moves quickly higher following the cutting of the curd.
Also as shown in Figure 2, however, buttermilk curd tends to retain the whey, and the removal of whey can be difficult and protracted process.
The cheese is then salted to taste. Note that the elapsed time from the onset of rennet addition, to the addition of the salt, should be on the order of four hours. The cheese is then packaged, typically, for example, into pre-lined drums 10, and pressed for 45 to 60 minutes.
Alternatively, cheese can be passed to a packing tower, in which it is formed into 20kg bolcks. The cheese should then be stored at temperatures of less than 4.5 oC.

Claims

1. A process for producing a cheese comprising the steps of:

-preparing a concentrated buttermilk having a pH of about 6, heating same to a temperature of about 35 °C;
-adding an effective amount of soluble calcium to improve coagulum formation;
-inoculating with an at least mesophilic starter culture;
and, -adding an effective amount of a coagulating enzyme;

then, once the coagulum has reached the desired consistency:
cutting; drawing; packing; and, pressing the resulting cheese.

2. The process according to claim 1 wherein said at least mesophilic starter culture is a thermophilic starter culture.

3. The process according to claim 1 wherein the concentrated buttermilk is evaporated at low temperature to a total solids content of about 18%
by weight.

4. The process according to claim 3 wherein the buttermilk is concentrated at a temperature of about 72 °C, for about 15 seconds.

5. The process according to claim 1 wherein the concentrated buttermilk is a mixture of concentrated buttermilk and concentrated skim milk.

6. The process according to claim 5 wherein the concentrated skim milk has a total solids content of about 18% by weight.

7. The process according to claim 6 wherein the skim milk is concentrated at a temperature of about 72 °C, for about 15 seconds.

8. The process according to claim 7 wherein the relative proportions of buttermilk to skim milk in said mixture is from at least some skim milk, up to about equal parts buttermilk and skim milk.

9. The process according to claim 8, wherein said mixture contains not more than about 60 parts skim milk for every 40 parts buttermilk.

9. The process according to claim 1 wherein the soluble calcium is CaCl2.

10. The process according to claim 9 wherein the CaCl2 is added at a rate of about 2 to 10 ounces per 1000 pounds of buttermilk.

11. The process according to claim 1 wherein the buttermilk is acidified to the pH of about 6 through the addition of an edible acid.

12. The process according to claim 11 wherein the edible acid is lactic acid.

13. The process according to claim 11 wherein the acidified buttermilk is held for up to 24 hours following addition of the edible acid, and prior to adding the starter culture.

14. The process according to claim 13 wherein the acidified buttermilk is held for about 2 hours prior to adding the edible acid, and prior to adding the starter culture.

15. A process for cutting of a buttermilk based cheese curd comprising the steps of adding water to the curd at an elevated temperature, once said curd has reached the desired consistency and either before or following cutting, and then stirring same in the presence of the heated water in an amount effective to lubricate the surfaces of the cut curd, thereby facilitating the stirring and ultimately improving the syneretic expression of whey from the curd.

16. The process according to claim 15 wherein the curd is heated to an elevated temperature in the range of about 52 °C for a period of from about 60 to about 90 minutes.

17. The process according to claim 16 wherein following the heating of the cheese, the cheese is then drawn onto the cheese table, packed and pressed, and then passed to storage.

18. The process according to claim 17 wherein the cheese is stored at a temperature of less than 40 °C.

19. A process for producing a cheese comprising the steps of:

-preparing a concentrated buttermilk having a pH
of about 6, heating same to a temperature of about 35 °C;
-adding an effective amount of soluble calcium to improve coagulum formation;
-inoculating with a thermophilic starter culture; and, -adding an effective amount of a coagulating enzyme;

then, once the coagulum has reached the desired consistency:
adding water to the curd at an elevated temperature, either before or following cutting, and then stirring same in the presence of the heated water in an amount effective to lubricate the surfaces of the cut curd, thereby facilitating the stirring and ultimately improving the syneretic expression of whey from the curd.

20. The process according to claim 19 wherein the curd is heated to an elevated temperature in the range of about 52 °C for a period of from about 60 to about 90 minutes.

21. The process according to claim 20 wherein following the heating of the cheese, the cheese is then drawn onto the cheese table, packed and pressed, and then passed to storage.

22. The process according to claim 19 wherein the concentrated buttermilk is evaporated at low temperature to a total solids content of about 18% by weight.

23. The process according to claim 22 wherein the buttermilk is concentrated at a temperature of about 72 °C, for about 15 seconds.

24. The process according to claim 19 wherein the concentrated buttermilk is a mixture of concentrated buttermilk and concentrated skim milk.

25. The process according to claim 24 wherein the concentrated skim milk has a total solids content of about 18% by weight.

26. The process according to claim 25 wherein the skim milk is concentrated at a temperature of about 72 °C, for about 15 seconds.

27. The process according to claim 26 wherein the relative proportions of buttermilk to skim milk in said mixture is from at least some skim milk, up to about equal parts buttermilk and skim milk.

28. The process according to claim 19 wherein the soluble calcium is CaCl2.

29. The process according to claim 28 wherein the CaCl2 is added at a rate of about 2 to 10 ounces per 1000 pounds of buttermilk.

30. The process according to claim 19 wherein the buttermilk is acidified to the pH of about 6 through the addition of an edible acid.

31. The process according to claim 30 wherein the edible acid is lactic acid.

32. The process according to claim 31 wherein the acidified buttermilk is held for up to 24 hours following addition of the edible acid, and prior to adding the starter culture.

33. The process according to claim 32 wherein the acidified buttermilk is held for about 2 hours prior to adding the edible acid, and prior to adding the starter culture.