Production of Cottage Cheese, Streamline Process.

 (Author: Jon Fosse, N.D.T. ApS, Denmark)

NDT Cottage Cheese Technology 

NDT Cottage Cheese Production

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Article

Introduction
Cottage Cheese is produced from low pasteurised skimmed milk and defined as a low fat soft, fresh and acid coagulated Cheese with clearly identifiable curd grains in a viscous cream or cream dressing mixture.
The Curd has normally a dry matter of a maximum at 20% and Water content at 80%.

The product has normally a short shelf life, but with some high hygienic solutions of equipment and production facilities, the Shelf life can be increased to 30 – 50 days.

Selecting the Correct Culture
Of great importance is to select the correct culture for your production.
The selection will very much depend on 3 main elements:

• What kind of result you want
• The Physiological and Bacteriological state of your milk
• What Supplier you would prefer

One of the main "enemies" of Cottage Cheese Production is Bacteriophages.
Most cultures are easy attacked by Bacteriophages. But some are less attacked by some Bacteriophages. Bacteriophages are most likely spread in the air either at the farmers or at the dairy plant. To prevent the effect of Bacteriophages it is recommended to rotate between several types of Cultures. The Suppliers of Culture will be able to recommend a Specific rotation according to your milk and production.
Normally this procedure is done like the following (This is an example of using of a Chr. Hansen Culture, other suppliers of Culture have procedures similar to this):

First use the Fresco 1000 culture.
Take out a sample from the whey after cutting.
Send this sample in a small cooler to Chr. Hansen for analysis of Bacteriophage.
(The sample should be filtrated with a sterile filter.)
From this sample Chr. Hansen will find out which cultures you should prefer in your production.

The Production
There are normally 2 production procedures. The "slow" procedure (12-15 hours) and the "Short-Cut" procedure (5-6 Hours).
The "Short-Cut" procedure is the most used procedure and is the one focused on in this production description.

Pasteurisation:
Skimmed Milk of high hygienic standard is low pasteurised at 72ºC at 15-17 seconds.
The Skimmed milk should have a dry matter of approx. 9%.

Acidification:
The pasteurised skimmed milk is led to the Cheese Vat at 29º-32ºC (depending on the culture in use) and added Culture normal from 4% to 5% and not more than 5%.
More than 5% Culture could give a too soft Coagulum. The Casein have been denaturized in the pasteurisation process and will with a too high percentage of Culture give a soft Coagulum and then the Curd will very easy be destroyed during cutting and the continuing process. At a start standing still of the milk, some rennet is added. Normal approx. 1ml/1.000kg of milk. It is of great importance to agitate the Culture and the Rennet as well as possible to make an even coagulated mass.
During Acidification it is important to keep the temperature at the same level. In a closed Cheese Vat this is safe. With an open Cheese and with a low room temperature it is recommended to cover the vat with some plastics or similar.
Normally is the Rennet added ½ to 1 Hour later than the Culture to have the rennet effect a little bit delayed according to the acid production.
The reason of adding rennet is to make a more firm Coagulum that better can stand the Cutting and agitate. There is also reached a better extraction of whey from the curd by adding rennet and reduced the risk of the curd "sticking" together during heating.
If too much rennet is added, the effect of rennet will be opposite and the coagulum to hard to cut and will be destroyed during cutting and agitating. The amount of rennet must be fitted in a way that it will NOT speed up the process.
To increase the effect of adding rennet, there could be added Calcium Chloride (CaCl) up to 0,02% of dry matter in cases where the milk has a lower content of Calcium. The Calcium Chloride has also a positive effect on the extraction of Whey from the Curd.

Cutting:
The Coagulum is cut at the isoelectric point of pH 4,6. Changes in the dry matter of the milk and the lactation period and different Culture types and amount and types of rennet and the goal for the best curd to fit the process makes the cutting start at pH4,8 to 5,4. This is very much depending on the type of culture used.
If the acidifications have come too far, the Coagulum will be too soft and there will be too much dust and the extraction of whey will be more difficult. To adjust for this the heating temp. have to be higher and there will be problems of reaching the final water percentage in the Cheese.
If the Coagulum has not been cultured to the correct amount of acid, the coagulum will be too elastic and will stick together and give some large and not even curd grains.
The time of cutting must be decided as accurate as possible by controlling the pH and the firmness of the Coagulum.
The size of the Curd is decided by the distance between the threads of the Cutting equipment. Cottage Cheese Curd is cut in Squares. The size of the Curd is decided by how you want the final Cheese to be and must be thought through before ordering equipment. Normal distances between the treads are from 9 to18mm.
After cutting the Cut Coagulum is set to rest for 10-20 minutes.

Heating:
Heating is done in 2 steps.
The 1st Step is done slow to the point of stopping the acidification to ensure a good whey extraction from the Curd.
The 2nd Step is done very fast to stop the acidification.
The total time of heating is approx. 1½ - 2 hours.

The Heating is decided partly by the Speed of Heating where the grains discharges the whey and where the grains rapidly gets the wanted water percentage, and partly the stopping of acidification as soon as possible.
It is the curds size and consistency that is the basic of the temperature used during heating. It is important to follow up with water contents analyses during heating. It is not desirable to have a water percentage higher than 80%.
If the previous stages have been accordingly, the curd should have an equal consistency and build without any whey "pockets". When the curd is broken it should give a clean break without any threads and should not stick together when a handful of curd is carefully squeezed together in the hand.
As previously explained the acidification must be stopped as soon as possible to prevent too much acid in the curd that partly makes the curd too fragile which makes less whey extraction. The optimal point of whey extraction is at the isoelectric point at pH 4,6-4,7.
The Titer must not exceed 5-6 ml from the point of cutting to the reach of a temp. of approx. 41ºC where the acidification stops.
The other way around of the consideration of whey extraction is the rising of temperature is done slow to prevent a membrane building up on the surface of the grains that will prevent the whey extraction. This is special for larger grains since they are heated slower to the centre of the grain and must, therefore, be heated slower to prevent this membrane.
The physical and chemical content and characteristics of the milk is also a very important basic of the determination of the end temperature of heating. A low content of casein and a high content of Citrates and Phosphates according to Calcium necessitate a higher end temperature. This could be to some point neutralises by adding Calcium Chloride.
As the last important factor of deciding the temperature run is the adding of rennet. Too much rennet will prevent an optimal whey extraction from the curd which results in a higher end temperature.
The above-mentioned conditions are directly working against each other. The decision of the temperature run must be a compromise of all these factors. Normally the end temp. is about 45º-46º C. I practical terms are used temperatures between 43º-58º C very much depending on the results of the process to the point of heating.
There is only possible to extract a certain amount of whey at a given temperature when the casein particles and any other conditions are equal. When this point is reached the water content of the curd is not much changed even if the time is prolonged. If the curd is too soft at the end of heating it is possible to let rest for approx. 15-30 minutes before draining.
Temp. the difference during Heating between the heating water and the whey should not exceed 10º-13º C. The Ideal is 6º - 8º C. This is very much depending on the experience and practical needs. Difference temperatures up to 25º C have been experienced acceptable in the last step of heating.

During the 1st stage of heating, the agitation is done as gentle as possible. The agitating is to be increased during the heating.
At the temp. of approx. 41º C when heated up at the ideal time and Dt the curd grains have been heated through the agitation can be increased.
If the coagulum is cut too early and the grains are too soft it could be necessary to delay the heating process 10-20 minutes to make the grains harder.
If the coagulum is turned too sour (too high acidification) the whey extraction will go too slow at same time as the grains turns too fragile, there could be emptied a large part of the whey till it only covers the grains and then filled up to the same volume with water at the same temperature as the whey and then continue the heating process.

Whey discharge and rinsing.
The whey is discharged by pumping the whey and grains together in a gentle way to the Drainer Washer. The pumping of Whey and Curd Grains should be in a way that ensures an equal mixture and conditions as in the Cheese Vat throughout the emptying of the Cheese Vat.
In the Drainer Washer, the Whey is drained off in the first section without any mechanical treatment. After a few seconds the Grains drained off on the Conveyor belt is rinsed with a small amount of water at 21ºC. This ensures the start of an osmosis process to extract the last whey left in the Curd Grains.
The next sections Cold water at 5º-10º C is rinsed over the curd in to start the cooling of the Curd Grains. It is important to prevent a too strong and fast cooling of the grains in order to prevent building a membrane on the Grain surface that again will prevent the osmosis effect (whey and water changing places) and also prevent the curd absorb the cream.
The last section at the Washing Camber the Curd Grains are flushed with cold water at 5º - 10º C to cool the Grains to the desired temperature at 8º to 12º C and also to rinse away any whey and small particles left on the surface of the grains.
The Curd Grains and water from the Washing Chamber is pumped directly to the Drum Drainer where the water is drained off and the Curd very gently is squeezed between the Drain Belt and a rotating Drum in order to break the last Water surface on the Grains. The Drum Drainer is equipped with an adjustable pressure regulator of the Grains. The Curd Grains falls directly into the Creamer (Blender). The Creamer could be filled with Cream, normally from 50% to 80% of the total Cream. This in order to let the Curd fall into the Cream as this is more gentle than falling directly on the hard surface of Stainless Steel. A gentle agitating could be started after a few minutes. When all the Curd is transported to the Creamer, the Controller calculates how much Curd is added and will according to the recipe add the last needed Cream. The Creamer is equipped with a Cooling Jacket to keep the Curd and Cream cold. Normal blending time is from 10 minutes to 30 minutes depending on the Curd and the Process in general. The mixture of Curd and Cream could be stored in the Creamer overnight.

Salting and cream addition.
Normally approx. 1% salt is added to Cottage Cheese by mixing with cream which is the most common procedure or by dissolved in distilled water and distributed directly into the Creamer in the last part of the blending.

The Cream which is applied for adjustment of fat content in the cheese must contain 10%-20% fat, possibly more if the water content of the cheese is higher than 80%, as it is used for increasing dry matter content of the cheese. The extra fat cream is applied if the cheese grains are relatively large or if they tend not to be able to absorb the cream, and finally, if a good cheese with a dry look, i.e. the small quantity of liquid between the grains, is required. The homogenised cream containing at least 20% fat is preferred as this provides the cheese grains with a fairly thick, shining coating, and simultaneously reduces the risk of whey extracting from the cheese before it is being consumed.
After resting 12-15 hours in cold Store in the Consumer Package, all the cream has been soaked into the cheese grains, and the cheese is ready for sale.

As mentioned the cream quantity depends on the fat content of the cream and on the dry matter content of the cheese.
Example – if the cheese contains 20% dry matter and the cream 15% fat the following mixture can be used: 75 kgs cheese, 1 kg salt and 24 kgs cream to get a final product containing 21% dry matter and 4% fat (assuming that the cheese contains 0.5% fat). If cream containing 20% fat is used the mixture will be as follows: 81 kgs cheese, 1 kg salt and 19 kgs cream.

For the production of 1 kg cheese (prior to addition of cream and salt) 5.5-7 kg (in average 6 kg) skimmed milk is needed, but of course, this depends on how carefully the coagulating has been carried out. However, the dry matter content and Calcium content of the milk also influences on the quantity needed, as studies indicate that the consumption of skimmed milk decreases proportionally more than a possible increase of the dry matter content of the milk stipulates.

Literature:
- Fremstilling of Danske Ostesorter, Mejeriteknisk Bogforlag, Denmark
23. kapitel: Surmælksoste, af H. Skov Rasmussen.
(Production of Danish Cheese Types, Mejeriteknisk Bogforlag,
23. Chapter: Acid Cheeses by H. Skov Rasmussen)
- Chr. Hansen A/S, Denmark
Production of Cottage Cheese

The latest development in the NDT Cottage Cheese line equipment, a world sensation.
NDT has during the last years developed a new construction of the Cottage Cheese equipment and enhanced the process itself through highly advanced mechanical constructions and advanced software of the process control. The new NDT Cottage Cheese lines can document an increase in yield of more than 10%.
Documented results:
Made by Skimmed milk with the protein content of 3,5% gives an average yield of 5,3kg skimmed milk per kg of curd grains!
For more information on this new process line for Cottage Cheese,
contact Director Jon Fosse at

Appendix 1

Production Flow Chart in Principle.

Appendix 2

Cause and prevention of defects in Cottage cheese

 The information contained herein is to our knowledge true and correct and presented in good faith. However, no warranty, guarantee, or freedom from patent infringement is implied or inferred. This information is offered solely for your consideration and verification.

 

Appendix 3

Content & Nutrition Facts.