EP4694694A1 - Process for the preparation of a swiss-type cheese - Google Patents

Abstract

Process for the preparation of a Swiss-type cheese comprising the steps of (a) preparing a cheese milk having a total protein content in the range of 3.0 to 5.0 grams/100 grams cheese milk; (b) mixing a rennet material and starter cultures comprising a starter material and propionic acid bacteria into the cheese milk; (c) allowing the cheese milk to coagulate to obtain a curd; and (d) further processing the curd into the Swiss type cheese, wherein (i) the cheese milk obtained in step (a) has a lactose content in the range of 1.8 to 3.6 grams/100 grams cheese milk; and (ii) the rennet material is added in an amount in the range of 250 to 650 IMCU/100 liters of cheese milk.

Description

Title: Process for the preparation of a Swiss-type cheese

FIELD OF THE INVENTION

The invention relates to a process for the preparation of a Swiss-type cheese.

BACKGROUND TO THE INVENTION

Swiss-type cheeses are a well known type of cheese characterised by eyes (i.e. holes) in the cheese and a somewhat nutty flavour resulting predominantly from the formation of propionic acid by the fermentation of lactic acid. Such fermentation could be spontaneously induced by the natural propionic bacteria in milk or could be achieved in a more controlled way by using a culture of selected propionic acid bacteria, typically species of the Propionibacterium genus. Examples of Swiss-type cheeses include Emmental, Gruyere and Appenzeller (all from Switzerland originally), Beaufort and Comte (from France) and Maasdam cheese (from the Netherlands). However, many other Swiss-type cheeses are also produced in other countries.

In the production of Swiss-type cheeses a combination of a primary starter and a secondary starter is typically used. The primary starter comprises lactic acid bacteria which convert lactose into lactic acid, whilst the secondary starter comprises the propionic acid bacteria and ferments the lactic acid. In the production of traditional Swiss-type cheeses such as emmental and Gruyere a thermophilic starter is used as the primary starter culture. However, in the production of more recent Swiss-type cheeses such as Maasdam cheese, also mesophilic starters are used as primary starter cultures. The production of Swiss-type cheeses will typically include a scalding or cooking step, in which the curd is heated. Scalding temperatures will typically be 30 °C or higher and could be as high as 55 °C for traditional Swiss-type cheeses such as Emmental cheese. In general, when mesophilic primary starter cultures are used scalding temperature will be lower (e.g. up to 40 °C) than when thermophilic starter cultures are used (40 °C and higher). Examples of thermophilic starters used are strains of Streptococcus thermophilus, Lactobacillus helveticus and Lactobacillus lactis. An example of a suitable mesophilic starter that could be used is Lactococcus lactis ssp. lactis. The lactic acid formed by the fermentation of the lactose is subsequently fermented by the propionic acid bacteria into propionic acid, acetic acid and carbon dioxide. An example of propionic acid bacteria are strains of Propionibacterium freudenreichii ssp. shermanii. As indicated, this latter fermentation of lactic acid gives the Swiss-type cheese its characteristic eyes and taste.

A common phenomenon is that ripening of the Swiss-type cheese continues during storage due to continued proteolysis and continued conversion of lactic acid by the propionic acid bacteria. This latter reaction causes the formation of carbon dioxide which, in return, may result in cracks in the cheese and too much acids formed, thus negatively impacting taste and aromas. Continued proteolysis reactions may result in taste and texture degradations. The present invention aims to provide a process that results in a Swiss-type cheese with better shelf-life properties and hence less defects, thus resulting in a Swiss-type cheese with excellent taste, aroma and texture properties and less prone to crack formation during prolonged periods of storage. An increased shelf-life also leads to less product that needs to be destroyed due to exceeding the maximum shelf-life or unacceptable deterioration of properties, which is beneficial from an economic point of view as well as a sustainability perspective.

SUMMARY OF THE INVENTION

The present invention relates to a process for the preparation of a Swiss- type cheese, wherein lactose content of the starting cheese milk and dosage of rennet for initiating coagulation of this cheese milk are carefully controlled, thereby enabling improved control of the ripening process and hence ensuring better quality Swiss-type cheese for prolonged periods of time.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, the present invention relates to a process for the preparation of a Swiss-type cheese comprising the steps of

(a) preparing a cheese milk having a total protein content in the range of 3.0 to 5.0 grams/100 grams cheese milk;

(b) mixing a rennet material and starter cultures comprising a starter material and propionic acid bacteria into the cheese milk;

(c) allowing the cheese milk to coagulate to obtain a curd; and

(d) further processing the curd into the Swiss type cheese, wherein (i) the cheese milk obtained in step (a) has a lactose content in the range of 1.8 to 3.6 grams/100 grams cheese milk (g/100 g), preferably 2.0 to 3.3 g/100g; and

(ii) the rennet material is added in an amount in the range of 250 to 650 IMCll per 100 liters of cheese milk (IMCU/100 I), preferably in the range of 350 to 600 IMCU/100 I.

The lactose content of cow’s milk generally varies between approximately 4 and 5 grams per 100 grams of milk (g/100 g) with a generally accepted average natural lactose content of 4.6 g/100 g. The cheese milk prepared in step (a) of the present process should accordingly have a reduced lactose content as compared to this average natural lactose content. The lactose content should, however, not be too low, as the lactic acid formed by fermentation of the lactose is needed for preservation of the cheese and as substrate for the fermentation by propionic acid bacteria to form the characteristic eyes and taste of Swiss-type cheeses. It was found that the reduced lactose content should be in the range of 1.8 to 3.6 grams/100 grams cheese milk (g/100 g), preferably 2.0 to 3.3 g/100g and most preferably between 2.0 and 3.0 g/100g. Such cheese milk with reduced lactose content can be obtained by ways known in the art.

Typically a cheese milk is prepared by subjecting raw milk to thermization, optionally bactofugation, fat separation and then adding a fat source (e.g. cream or full fat milk) to obtain a cheese milk with the desired fat: protein ratio. For the purpose of the present invention the cheese milk suitably has a fat:protein weight ratio in the range of 0.50 to 1 .2, preferably 0.75 to 0.90.

As indicated, the cheese milk should have a reduced lactose content. One suitable method to obtain such cheese milk with reduced lactose content is by mixing a casein source, a milk fat source, skimmed milk and water. By starting from skimmed milk with a normal lactose content and diluting such skimmed milk with water the lactose content is reduced. The desired fat:protein ratio can then be obtained by adding a casein source and a milk fat source. Suitable casein sources include, for example, micellar casein isolate (MCI) and milk protein concentrate (MPC). Suitable milk fat sources include, for example, cream, butter, butter oil, anhydrous milk fat (AMF), AMF fractions or mixtures of two or more of these fat sources. Alternatively, the cheese milk can be prepared by first preparing a concentrated milk product by subjecting a starting milk to one or more filtration steps and subsequently diluting the concentrated milk thus obtained with water to the desired protein content and then adding a fat source to obtain the desired fat:protein ratio. Filtration suitably involves an ultrafiltration step, optionally followed by one or more diaf iltration steps.

Total protein content of the cheese milk prepared in step (a) is in the range typically found in cheese milk, i.e. in the range of 3.0 to 5.0 grams/100 grams cheese milk (g/100 g). It was, however, found particularly suitable to prepare a cheese milk with reduced lactose content in step (a) that has a protein content in the range of 3.5 to 4.8 g/100 g, more preferably 4.0 to 4.6 g/100 g. The weight ratio casein:whey protein could vary somewhat depending on the method used to prepare the cheese milk. The weight ratio casein:whey protein could, accordingly, range from the ratio found naturally in cow’s milk (i.e. approximately 80:20) to 90:10. Particularly when casein- rich sources such as MCI are used to standardize the cheese milk to the desired fat:protein ratio, the casein:whey protein ratio could be higher than 80:20.

Once the cheese milk with the desired fat:protein weight ratio is obtained in step (a) starter cultures and rennet material are added. The order in which starter cultures and rennet material are added is not particularly critical. For example, starter cultures may be added to the cheesemilk by dosing it into the conduit that transports the cheese milk to the cheese vat (i.e. the vessel or tank where coagulation takes place) or by dosing it directly into the cheese vat containing the cheese milk. Rennet would typically be dosed into the cheese vat, but could alternatively also be added to the cheese milk via the aforesaid conduit. The cheese milk in the cheese vat is continuously stirred, so that starter cultures and rennet are homogenously distributed through the cheese milk to ensure homogenous coagulation and fermentation.

The rennet material induces coagulation of the casein present in the cheese milk by operation of the enzymes chymosin and pepsin which are typically present in the rennet material. In general, the milk-clotting activity of rennet is expressed in International Milk Clotting Units (IMCU) in accordance with international standard ISO 11815:2007. Essentially one IMCU is defined as the amount of rennet enzyme that coagulates 10 ml of a standard milk substrate at pH of 6.5. The standard milk substrate is a skim milk powder dissolved in a calcium chloride solution (110 g skim milk powder dissolved in 1000 ml of a 0.5 g/l CaCl2 solution). So, for example, 250 IMCU is the amount of rennet that is needed to coagulate 2500 ml (250 x 10 ml) of standard milk substrate. If a rennet material has a strength of 250 IMCU per milliliter of rennet (250 IMCU/ml), it means that 1 ml of this rennet material is sufficient to coagulate 2500 ml of standard milk substrate.

It was found that the amount of rennet added should be carefully dosed. More specifically, it was found that the rennet material should be added in an amount in the range of 250 to 650 IMCll per 100 liters of cheese milk having a protein content as indicated hereinbefore (IMCU/100 I), preferably in the range of 350 to 600 IMCll/100 I. It was found that when using this amount of rennet material in combination with the reduced lactose amount of the cheese milk, a Swiss-type cheese is obtained which exhibits the advantages mentioned above: improved shelf-life properties and less defects as well as excellent taste, aroma and texture properties whilst being less prone to crack formation during prolonged periods of storage.

Prior to, simultaneously with or after addition of the rennet material also the typical starter cultures used to produce Swiss-type cheese are added to the cheese milk. These starter cultures comprise a starter material and propionic acid bacteria. The starter material typically comprises lactic acid bacteria as primary starter cultures to convert the lactose into lactic acid. Examples of such primary starter cultures are the thermophilic starter cultures and the mesophilic starter cultures mentioned above. Such cultures are well known. The starter cultures furthermore comprise propionic acid bacteria as secondary starter cultures to convert the lactic acid formed into propionic acid, acetic acid and carbon dioxide. Suitable propionic acid bacteria are also well known. These include the strains from the genus Propionibacterium, in particular Propionibacterium freudenreichii ssp. shermanii. The starter cultures are added in their usual amounts and typically total amount of starter cultures will be in the range of 0.01 to 1.0% by weight based on total weight of cheese milk. The exact amount of particularly the primary starter will also depend on the concentration of the relevant lactic acid bacteria in the starter material. The amount of propionic acid bacteria added will typically be in the range of 0.00001 to 0.01 % by weight based on total weight of cheese milk, whilst primary starter will suitably be added in an amount of 0.01 to 0.99% by weight based on total weight of cheese milk.

In step (c) the coagulation takes place and the curd is formed. Simultaneously fermentation of lactose into lactic acid by the primary starter cultures added takes place. This step takes place under the usual conditions and in the equipment normally used in Swiss-type cheese manufacture, typically a so called cheese vat: a vat or tank in which the cheese milk is converted into the curd through the action of the rennet material.

Further processing of the curd into the Swiss-type cheese takes place in step (d). Also this step can be carried out in the usual way for producing Swiss-type cheese. In a suitable embodiment step (d), accordingly, comprises the steps of (d1 ) cutting the curd;

(d2) draining the curd, obtaining a first whey stream and drained curd;

(d3) scalding the curd obtained in step (d2);

(d4) further draining the curd obtained in step (d3), obtaining a second whey stream and a dried curd;

(d5) molding and pressing the curd, obtaining a third whey stream and a shaped curd;

(d6) brining the shaped curd, thus obtaining the unripened cheese; and (d7) ripening the unripened cheese to obtain the Swiss-type cheese.

Following step (d7) a further step may follow:

(d8) packaging and storing the cheese.

All steps (d1 ) to (d7) as well as step (d8) are well known and can be carried out in the usual way in the equipment typically used therefor. For example, cutting and draining the curd in steps (d1 ) and (d2) will normally take place in the cheese vat in which also the coagulation takes place. The drained curd obtained will then be subjected to scalding step (d3) followed by further draining of whey in step (d4). The scalding (or cooking) treatment is typical for the preparation of Swiss-type cheese. Such scalding will typically involve heating the curd to a temperature of at least 30 °C, for some Swiss-type cheeses it could even be at least 45 °C. The curd will typically not be heated to temperatures above 60 °C, suitably not above 56 °C. Scalding causes expelling of water/whey from the curd, which will be removed during the subsequent draining step. The higher temperatures will also inactivate any mesophilic starter cultures used. The whey streams recovered in the various processing steps are suitably combined and further processed, for example for isolating certain serum proteins (e.g. [3-lactoglobulin, a-lactalbumin, immunoglobulins, serum albumin, lactoferrin), preparing whey protein isolates or, after purification, for use in nutritional products such as infant formula. Molding and pressing the curd (step (d5)), brining step (d6) and ripening step (d7) are carried out in the common way known in the art. After brining step (d6) the unripened cheese formed will be ripened in ripening step (d7). It was, accordingly, found particularly suitable to carry out ripening step (d7) by placing the unripened cheese obtained in brining step (d6) in a ripening chamber under controlled conditions, typically at a relative humidity between 70% and 95% and a temperature between 10 °C and 20 °C for at least 10 days and usually not more than 45 days, preferably not more than 35 days. Within this ripening period different temperature intervals may be applied, for example a temperature between 10 and 15 °C for 5 to 20 days followed by or preceded by a temperature between 15 and 20 °C for another 5 to 20 days. These were found to be very good ripening conditions for the specific Swiss-type cheese resulting from the process according to the present invention.

After such ripening the cheese will typically be packaged and then stored at a lower temperature (i.e. at 10 °C or lower), suitably at a temperature in the range of -2 °C to 10 °C, preferably 3 °C to 8 °C, for a period of at least 50 days, preferably at least 90 days. As indicated above, ripening reactions will normally continue during storage, be it at a lower rate due the low storage temperature, thereby resulting in cracks and more acid formation, which negatively impacts taste and aromas and hence shelf-life. The process of the present invention results in a Swiss-type cheese with excellent taste, aroma and texture properties which is less prone to crack formation during prolonged periods of storage.

EXAMPLES

The invention is further illustrated by the following examples.

Example 1

Flat, wheel-shaped Swiss-type cheeses of about 12 kg were prepared using a 700 I curd preparator as follows.

Approximately 700 liters of cheese milk were prepared by mixing in the curd preparator full fat milk and skimmed milk, both with normal lactose content, to obtain cheese milk with a protein content of 3.5 g/100 g of cheese milk (g/100 g), a fat/protein weight ratio of 0.85 and a lactose content of 4.6 g/100 g of cheese milk (i.e. the normal lactose content of cheese milk).

To the cheese milk were subsequently added under continuous stirring: - microbial rennet Milase Premium (ex. CSK food enrichment) having a strength of 200 IMCU/ml (12.2 grams per 100 liters of cheese milk corresponding with 2440 IMCU/100 I; this is the normal dose for preparing Swiss-type cheese),

- CaCl2 (35 wt%-solution: 160 g/100 I;

- LD-bulk starter C-57 (ex. CSK-food enrichment), 0,5 wt%; and

- Propionibacterium culture C-23 (ex. CSK food enrichment), 0.85 g/100 I.

After all ingredients were added and mixed into the cheese milk, the cheese milk was allowed to set for 35 minutes at 31 ,5 °C whilst coagulation occurred, resulting in a gelled milk coagulum. This coagulum was cut and approximately 30% of the volume of the coagulum was then drained as whey. To the remaining curd-whey mixture wash water was added in an amount corresponding to 25% of the volume of this remaining curd-whey mixture. The resulting mixture was subsequently scalded at 35 °C for 40 minutes whilst continuously stirring. Further draining of whey took place, the resulting curd was then put in wheel-shaped moulds, pressed (5 hours, 1 bar), removed from the moulds and allowed to rest for 12 hours. The resulting wheel-shaped curd masses were then placed in a brining bath for 40 hours.

One of the shaped curd masses was analyzed for composition (see results in Table 1 ) and all shaped curd masses were further ripened for 14 days at 13 °C, followed by 14 days at 19 °C, at a relative humidity of between 80 and 90 %, whilst receiving a treatment with a cheese coating composition (Ceska WL, ex. CSK food enrichment) at regular intervals. After this period, the cheeses of approximately 12 kg each were cooled to 7 °C and stored for 3 months at this temperature.

After ripening and cooling, at the start of the storage period for 3 months, eye formation was characteristic for Swiss-type cheese and taste was typically nutty, sweet. However, after the 3 months cold storage (7 °C) the taste had become bitter, acid and overripe, whilst growth of eyes had continued resulting in slit formation and propionic acid content had increased with > 40% during the cold storage.

Example 2

Example 1 was repeated except that the amount of rennet (strength 200 IMCU/ml) dosed was 2.45 g/100 I, corresponding with 490 IMCU/ 100 I (i.e. 20% of normal dosage used). After ripening and cooling, at the start of the storage period of 3 months, eye formation was characteristic for Swiss-type cheese, whilst lactic acid was fully consumed. During the storage period of 3 months, eyes kept stable (no significant growth, no slit formation), whilst propionic acid content increased with < 20 %. The cheeses from this example 2 were characteristic, but mild and kept this profile during the 3 months cold storage, although some bitter formation occurred and the cheeses started to taste slightly bitter.

Further properties of the cheese milk and cheese prepared are show in Table 1.

Examples 3-6

Example 1 was repeated except that the amount of lactose in the cheese milk and the dosage of rennet were varied. Amount of washing water (% by volume of water on volume of curd-whey mixture resulting from first whey draining) was varied to vary resulting lactose levels in curd.

The amount of lactose was varied by preparing the cheese milk having a fat/protein ratio of ~0.85 by mixing in the curd preparator micellar casein concentrate MCI-80 (Refit® MCI-80 RL liquid; ex. FrieslandCampina Ingredients), cream having a fat content of 40 % by weight, skimmed milk and water in different mixing ratios (by weight): a) mixing ratio MCI-80:cream:skimmed milk:water of 14:9:60:17, resulting in a cheese milk having a total protein content of 4.4 g/100 g and a lactose content of

3.2 g/100g corresponding with 70% of the lactose content of normal cheese milk with the same fat/protein ratio (Examples 3 and 4); or b) mixing ratio MCI-80:cream:skimmed milk:water of 18:9:42:31 , resulting in a cheese milk having a total protein content of 4.3 g/100g and a lactose content of

2.3 g/100 g corresponding with 50% of the lactose content of normal cheese milk with the same fat/protein ratio (Examples 5 and 6).

The amount of rennet (strength 200 IMCU/ml) dosed in Examples 3 and 5 was the same as in Example 1 : 12.2 grams per 100 liters of cheese milk corresponding with 2440 IMCU/100 I. The amount of rennet (strength 200 IMCU/ml) dosed in Examples 4 and 6 was 2.45 g/100 I, corresponding with 490 IMCU/ 100 I (i.e. 20% of normal dosage used). During the storage period of 3 months at 7 °C, eyes of variants with lower lactose content of Examples 3-6 remained stable (no significant growth of the eyes, no slit formation), whilst propionic acid content increased less, compared to reference cheeses of Examples 1 and 2 (100 % lactose, increase of propionic acid content 3-6 times higher). Cheeses of Examples 3-6 made of low-lactose milk were characteristic nutty and sweet, but mild and kept this profile during storage, with some bitter formation though for the 100 % (2440 IMCU/100 I) rennet variants of Examples 3 and 5. The 20% (490 IMCU/100 I) rennet variants of Examples 4 and 6 on the other hand did not exhibit any bitter formation after 3 monts of storage.

So Examples 4 and 6 which illustrate the invention show that a Swiss type cheese prepared using a cheese milk having lower lactose content (3.2 g/100 g and 2.3 g/100 g, respectively) as well as a lower rennet dosage (490 IMCU/100 I) has an improved stability (no continued eye formation, no slit/cracks formation and less increase of propionic acid content), maintains the characteristic nutty and sweet but mild taste, and keeps this taste profile without any bitter formation during the 3 months of cold storage.

Further properties of the cheese milk and cheeses prepared are show in Table 1.

Thus, the Examples show that starting from a cheese milk with a lower lactose content and using a lower dosage of rennet results in a Swiss-type cheese which is not only more stable during cold storage in terms of continued eye formation, slits/crack formation and propionic acid content, but is also less prone to bitter formation and hence has a more stable flavor profile during shelf life.

Table 1

* According to the invention

¹⁾ measured according to NEN 3755:1998 - expressed in % by weight based on total weight of cheese

²⁾ measured according to NEN-EN-ISO 5943:2006 (chloride content) - expressed in % by weight on dry matter

³⁾ measured according to NEN-ISO 3433:2008 - expressed in % by weight on dry matte

Claims

1 . Process for the preparation of a Swiss-type cheese comprising the steps of

(a) preparing a cheese milk having a total protein content in the range of 3.0 to 5.0 grams/100 grams cheese milk;

(b) mixing a rennet material and starter cultures comprising a starter material and propionic acid bacteria into the cheese milk;

(c) allowing the cheese milk to coagulate to obtain a curd; and

(d) further processing the curd into the Swiss type cheese, wherein

(i) the cheese milk obtained in step (a) has a lactose content in the range of 1.8 to 3.6 grams/100 grams cheese milk (g/100 g), preferably 2.0 to 3.3 g/100g; and

(ii) the rennet material is added in an amount in the range of 250 to 650 IMCU/100 liters of cheese milk (IMCU/100 I), preferably in the range of 350 to 600 IMCU/100 I.

2. Process according to claim 1 , wherein the cheese milk is standardized to have a fat:protein weight ratio in the range of 0.50 to 1.2, preferably 0.75 to 0.90.

3. Process according to claim 1 or 2, wherein the cheese milk is prepared in step (a) by mixing a casein source, a milk fat source, skimmed milk and water.

4. Process according to claim 1 or 2, wherein the cheese milk is prepared in step (a) by first preparing a concentrated milk product by subjecting a starting milk to one or more filtration steps and subsequently diluting the concentrated milk with water and adding a fat source.

5. Process according to any one of the preceding claims, wherein step (d) comprises the steps of

(d1 ) cutting the curd;

(d2) draining the curd, obtaining a first whey stream and drained curd;

(d3) scalding the curd obtained in step (d2); (d4) further draining the curd obtained in step (d3), obtaining a second whey stream and a dried curd;

(d5) molding and pressing the curd, obtaining a third whey stream and a shaped curd; (d6) brining the shaped curd, thus obtaining the unripened cheese; and

(d7) ripening the unripened cheese to obtain the Swiss type cheese.

6. Process according to claim 5, wherein the ripening in step (d7) takes place at a relative humidity between 70% and 95% and a temperature between 10 °C and 20 °C for a period in the range of 10 days to 45 days.

7. Process according to claim 5 or 6 further comprising the step of (d8) packaging and storing the cheese.

8. Process according to claim 7, wherein storage in step (d8) is carried out by placing the ripened cheese obtained in step (d7) into storage at a temperature in the range of in the range of -2 °C to 10 °C, preferably 3 °C to 8 °C, for a period of at least 50 days, preferably at least 90 days