Pasteurisation - heat treatment
When, why and how the milk should be pasteurised? The decision on the heat treatment or use of raw milk without pasteurization is made by the maker. To make the right decision, try to gather as many aspects as possible.
With industrial equipment, the time of keeping heat can be shortened to 20 minutes.
Pasteurisation 72-74°C for 20 seconds
The structure of milk changes roughly, so the makers of homemade cheeses usually avoid this temperature. Under industrial conditions, this temperature is used for heat treatment of cheese milk because it can be easily done with fast and operational equipment. Soluble calcium ions should be replaced in the milk thus heat-treated, with the addition of calcium chloride.
Raw milk or pasteurised milk by cheese variety:
The responsibility for the decision always on the maker, because only he knows how reliable the milk from which he works and under what conditions he processes it. Does the maker has enough professional knowledge and experience to manage the processes of processing?
Soft cheeses, delicacy cheeses, beer and tea cheeses, mouldy cheeses, mascalpone
Gentle pasteurization is required. It’s possible to make impeccable soft cheeses from raw milk, but this requires a very careful, expert maker. And of course, first-class, fresh, tested raw milk.
It was originally made by shepherds from freshly milked raw milk. Whether it is made from gently heat-treated milk or raw milk, it must be ensured that the mesophilic strains have sufficient potential. To this end, it is recommended to use mesophilic starters if you are not sure if there is a sufficient amount of lactic acid-producing strain in the milk or if you are working from heat-treated milk. (if high-quality clotted milk can be made from the milk concerned, it contains enough mesophilic strains)
Semi-hard-hard cheeses aged beyond 35 days:
These artisanal cheeses are usually made from raw milk, but the decision can be made responsibly by the maker, because he knows the origin of the milk, the conditions of processing and his own knowledge.
Pasta filata cheeses (parenyica, mozzarella, etc.)
Pre-pasteurisation is not necessary because sufficiently acidified cheese nosterate must be drilled through water at ~85°C.
What diseases can a dairy product carry?
Infection and disease caused by cheeses and other fermented dairy products are rare. Inedible, bloated cheese, infused with E. coli or butyric acid bacteria, and mouldy sour cream yoghurt occur.
It is caused by a toxin called botulin produced by the bacterium Clostridium botulinum. In a sour environment, so in well-prepared cheese, it does not multiply.
Anaerobic soil-dwelling bacteria.
Cheese-induced disease is very rare, but mascalpone poisoning has occurred before.
Listeria monocytogenes is the cause of listeric diseases. Its natural habitat is the soil, but it can also be found in the intestinal canals of animals and people. It multiplies well in feed, plants, and also in the refrigerator, cold room.
From the point of view of cheese-making:
Listeria infections caused by cheeses are very rare, but if so, it is always the mayor news, as clinical cases can even result in death.
The most important rules are:
Clean, careful work and professional cheese making result in beautiful healthy cheeses.
Ration the mesophilic bacteria responsible for the initial maturation of milk. The acidification of cheese milk and cheese does not allow most pathogenic infectiouss to prevail, because milk is dominated by lactic acid bacteria.
Read more about this here:
Severe listeria infections of cheeses occur in soft cheeses ripened for 10-25 days. Soft cheeses that are made from raw milk with milder acidification has higher risk for infection. Most endangered cheeses are camembert, brie, mascalpone. Mouldy cheeses lose their acidity during ripening (increasing pH), so they open the way for latent listeria. In addition, such cheeses are consumed precisely when the infection is at its peak. (days 14-25)
The listeria is destroyed by pasteurised temperatures, so as a preventive thing, such cheeses should be made from pasteurised milk or have the necessary expertise and lab background.
Practice and statistics show that this disease is caused by goat's milk eaten raw, but any raw milk can in principle carry such a virus. The risk of infection is eliminated by heat treatment of milk or significantly reduced in milk products processed into cheese. In a sour environment, after a few days, the virus loses its infectivity.
Bacteriophagic infections are much more common in pasteurized milk, they are much less common when processing raw milk. These viruses, which destroy lactic acid bacteria, are the main cause of acidification disorders.
Types of heat treatments when making homemade dairy products
Before making yoghurt varieties:
Some species of Clostridium cause rotting and stretching due to their protein-disrupting effect. Before making yogurt, the milk should be heated above pasteurized temperature so that these strains are destroyed. This means a minimum of 86°C at all points of milk. The homemaker must heat the milk up to at least 90-92°C to make sure it is safe. Then rapid cooling back to the recommended temperature of mixing culture. (43-48°C) The proteins of milk that have undergone heat treatment are dehydrated and therefore form a stronger- firmer curd. This is true if the milk is to be clotted acidically. In this respect, it is beneficial to heat the milk before making yogurt, kefir, clotted milk, because a more whey-holding and firmer curd is formed.
Gentle pasteurization for cheese preparation:
Gentle heat treatment of milk with a heat retention of 63-65°C / 30 minutes. This temperature does not yet cause a serious change in the structure of milk, so calcium can be used for cheese making without supplementation. Nevertheless, the dosage of calcium salts benefits the cheese matter and improves the yield. During heat retention, the milk must be mixed several times to pass through all parts. After 30 minutes, the milk must be cooled quickly to the temperature of pre-ripening and inoculated for the cheese variety.
The bacterium cultures and the calcium chloride must be stirred in the milk at this time.
Late bloating can be prevented by using the enzyme Lysozyme. Strains that cause butyric bloating are also able to multiply in the concentrated salt bath, which you can protect yourself against by regular boiling.
As a result of heat treatment, the lactic acid-producing strains characteristic of the region and the natural enzymes of milk are destroyed. The milk can be controlled from a bacterial point of view, it is ready for industrial processing, but with it the bacterial imprint of the landscape has been erased from it. Milk that has undergone heat treatment loses its diversity and natural protection. This diversity will be missed by the flavours and aromas of cheese, which is why the maker of long-ripened high-end cheeses often skips heat treatment.
What problems do we not avoid with heat treatment?
Many bacteria survive pasteurized temperatures (range from 63 to 73°C). Since the lactic acid bacteria, which are a natural barrier around them, have died, it is easier for strains of bacteria to multiply in milk that has undergone heat treatment that they have not had the opportunity to prevail before. It is very important to inoculate and ripen cooled milk with bacteria as soon as possible.
Among pasteurized surviving bacteria, the cheesemaker is most often forced to face strains of Clostridium. Clostridium butyricum and tyrobutyricum are the causes of butyric bloating. Cheeses ripened for more than 3 weeks cause bloating and then internal cracking. More on bloating:
Heat treatment reduces the biological potential of milk, destroys important acidifying strains and natural enzymes of milk. It impairs the clotting capacity of milk, impairs its yield, can result in taste and odour defects.
What do we gain with heat treatment?
Through pasteurization, we partially get rid of some of the problematic strains that can be: enzyme inhibitory strains, strains that inhibit lactic acid bacteria, disease-causing (pathogenic) strains, strains that impair quality - cause cheese defects.
We heat the raw milk to destroy undesirable microorganisms. Reduce the microflora of milk to a uniform, hand-held, predictable starting state. From an operational point of view, it is a very important operation, because the predictably behaving raw material can then be processed in accordance with the technology, its recipe, in automated systems, with the help of trained workers.