Cheese is a product made from animal milk. It is therefore a product suitable for vegetarians, who, unlike vegans, do not eliminate animal derivatives (milk, cheese, butter, eggs, honey, etc.) from their diet. In the dairy industry, starters, rennet are a fundamental ingredient for the production of many types of cheese.

What are the starters/cultures used for the production of cheeses.

By microbial starter we mean a consortium of microorganisms that is inoculated into the milk at the beginning of cheese making to reduce the pH, with different functions.
The production of fermented milk-based foods, such as cheeses, yoghurts, etc., is a technological process whose performance strongly depends on the starter cultures, which must be added to the initial matrix. These starter cultures can consist of both lactic and non-lactic bacteria (eg propionic bacteria), and other microorganisms (yeasts, molds).
The selected starter cultures can consist of either a single type of microorganism or a mixture of human-selected microbial strains, depending on the desired characteristics of the final product. The peculiarity of the strains used is that each is selected individually, emphasizing their individuality and keeping them in purity. The advantages derived from the use of these crops are many, such as the easy preparation, the high reproducibility of fermentation, which is therefore regular, and the standardization of the final product. However, there are also disadvantages in the use of these starters, such as the high costs to be incurred for the selection of the strains and the loss of typicality of the final products, which will therefore be homogeneous and with less individuality.

Thermophilic cultures are suitable when working at temperatures above 34 degrees and up to 45.

Mesophilic cultures are suitable when working below 33 degrees and up to 15/16 degrees.

In thermophiles, depending on the cheese to be produced, the presence inside the mixture present in the bag is increased or decreased. For example, the thermophiles for pasta filate are certainly more aggressive (and therefore more present) than for example the thermophiles used for a caciotta. Another important distinction between lio cultures is to know whether they are homofermented or heterofermented; thermophiles produce only lactic acid from the fermentation of lactose; Mesophiles, on the other hand, from the fermentation of lactose, produce not only lactic acid but also carbon dioxide which makes it possible to have an occhiato cheese.

Then among the thermophiles there are different strains of bacteria (streptococcus, termophilus, helveticus, lactis, bulgaricus, etc.) as well as among the mesophiles (casei, fermentum, rhamnosus, cremoris, etc.).
The differences between these strains are that each of them gives an organoleptic aroma to the cheese.

For example, helveticus is used extensively in Parmesan, Emmental, and for the production of cooked and long-aged cheeses, thanks to its rapid acidification capacity, resistance to low pH values ​​and to curd cooking treatments.

The bulgaricus, streptococcus It can be found in milk and in many natural crops for the production of cheeses such as asiago, provolone, emmenthal, gruyere, montasio, mozzarella, and is, together with Lactobacillus bulgaricus, one of the two bacteria used in the production of yogurt according to statutory prescription.
In yogurts there are generally bacteria called probiotics.

Natural starters

The use of natural starters involves the use of yogurt, making the yogurt itself a starter for dairy products. Yogurt is a matrix that contains live and vital microorganisms and at the end of production it does not undergo heat treatments; therefore the microbial forms present are not inactivated, which is why yogurt is itself a starter that can be added with percentages from 1 to 3% depending on the type of cheese.

What is rennet

Rennet is a compound based on enzymes, capable of determining the coagulation of the casein contained in milk. This coagulation precipitates on the bottom of the container in which the processing is carried out, giving rise to the so-called “curd”, the basis for all types of cheeses.

Rennet can be of animal, vegetable or microbial origin. We will see these 3 types together, so as to have clear ideas and, if necessary, take a position on it.

Animal rennet: it is obtained from the fourth stomach (or abomasum) of some young ruminants such as veal, buffalo, lamb or kid. These young ruminants feed exclusively on mother’s milk and therefore have great enzymatic richness in their abomasum.

Vegetable rennet: it is extracted from the flowers of plants, such as Cynara cardunculus, commonly called cardoon or fig. The cheeses obtained with this product are more fragrant and more digestible; moreover, by releasing more amino acids in less time, they allow us to better assimilate good fats as energy without raising insulin which is instead fattening.
With the use of vegetable rennet, the Fiandino Farms have created, first in the world, the KINARA METHOD, which sees the use of the flowers of Cynara cardunculus, the common wild thistle that grows spontaneously even in our mountains, transforming itself into “true vegetable rennet “. It is a rare and sought-after alternative to the traditional animal rennet, able to make a decisive contribution to the “zero lactose” of Gran Kinara and to provide original and pleasant organoleptic characteristics.

Microbial rennet: it is extracted from some types of molds (such as Mucor miehei) or other microorganisms and has a coagulating action. It is used for large-scale productions due to its low cost. It is used for large-scale production thanks to its low cost, and is recommended for all hard and semi-hard cheeses.

Chymosin rennet: it is extracted from the fermentation of kluyveromyces lactis dairy yeast.
Being a derivative of yeasts, not of animal origin, it does not contain allergens.
Proteolytic enzyme present in milk (also called rennin), with a structure similar to pepsin. It causes milk to clot, as it partially hydrolyzes casein to paracasein, which precipitates in the presence of calcium ions.

How animal rennet is extracted

The rennet is extracted from the abomasum of young ruminants, as they have high levels of chymosin, the enzyme that allows the digestion of mother’s milk. Of course, for its extraction, the killing of the animal is necessary.

These very young living beings are killed at a very young age in order to be able to use the “pure product” contained in their stomach. Lamb is grown where there is no grass, even when it is time to start weaning, because there must be no risk that it will eat a few blades of grass that “contaminate” the precious rennet. It is then killed around 22 days of life, an age beyond which it should necessarily be weaned and therefore it would be useless for the production of rennet.

Therefore, we can safely say that they are killed at that age precisely because of the rennet.

Then there is the “strengthened rennet”. When a little lamb is born, after a few days of life he is removed from his mother so as not to allow him to breastfeed. After three days of fasting, he is brought back to his mother: the poor puppy is practically dying of hunger and therefore eats greedily, filling his stomach with milk. The poor animal is killed shortly after, when greater quantities of gastric juices to digest the milk come into operation in its stomach. This is an illegal practice, which unfortunately happens …

What are the advantages for the dairy industry in using animal rennet:

• dairy processing is faster;

• in their opinion, the final product is perfect;

• always in their opinion, cheese has a particular and recognizable smell and taste.

How to recognize cheese with animal rennet

The first thing to do, to check if the cheese you are about to buy contains rennet of animal origin, is to check the label. But it does not always contain exhaustive information.

The words “rennet” or “natural rennet” may be present, generic indications that do not help us understand what the origin is. Fortunately, however, the terms “animal rennet”, “vegetable rennet” or “microbial rennet” are beginning to be noticed more and more often: this can help vegetarians in choosing which cheese to buy. The problem, however, is that, in most cases, the wording is generic.

Unfortunately, to date, in Italy there are no laws on the transparency of some substances on the label and, as regards cheese, the producer is not obliged to specify the type of rennet used.

There are types of cheeses that have always been without animal rennet, such as mascarpone, which is made through the acidification of cream, and ricotta, which comes from whey and is made with thermal coagulation. In addition, organic cheeses show the type of rennet used on the label.

Rennet is also found on the market, with an indication of the coagulating strength. The most commonly used ratio between rennet and milk is 1: 10,000, which corresponds to about 1 ml of rennet per 10 liters of milk, which coagulate in about 40 minutes.

1: 10,000 = 1ml for every 10 liters of milk – 0.1ml for each liter of milk.

How much animal rennet per 10 liters of milk?

Animal rennet has a different titer and therefore the ratio mL of rennet: liters of milk is also different; for animal rennet about 8 – 10 mL of rennet (which corresponds to about 160-200 drops) is required for 10 liters of milk.

How much vegetable rennet per 10 liters of milk?

Vegetable rennet has a different titer and therefore the ratio mL of rennet: liters of milk is also different; for vegetable rennet about 2 – 4 mL of rennet (which corresponds to about 40-80 drops) is needed for 10 liters of milk.

How much microbial rennet per 10 liters of milk?

The microbial rennet has a different titer and therefore the ratio mL of rennet: liters of milk is also different; for microbial rennet about 2 – 3 mL of rennet (which corresponds to about 40 – 60 drops) is needed for 10 liters of milk.

How much chymosin rennet per 10 liters of milk?

Chymosin rennet is extracted from the fermentation of kluyveromyces lactis dairy yeast.
Being a derivative of yeasts, not of animal origin, it does not contain allergens.
With its characteristic and a title of well 200IMCU / ml. It is a totally versatile and easy-to-use rennet, and can be used for almost all processing (dairy products, stretched curd, fresh cheeses, white, semi-aged and aged cheeses).
For Chymosin rennet about 2 – 3 mL of rennet (which corresponds to about 40 – 60 drops) is needed for 10 liters of milk.

How to dilute the rennet?

The rennet must be diluted in a ratio of 1: 5, 10 grams of rennet in 50 ml of warm water, not with liters of water that make the milk water down and inevitably lose a part of rennet in the whey and not in the cheese.

When to put rennet in milk?

The rennet is added to the milk warmed at a temperature of 36 °- 39 °C according to the type of cheese. If there are curdling problems, you can try raising the temperature before trying to add more rennet. Before being added to the milk, the rennet should be diluted in a little water.

Which rennet is better?

The liquid rennet – which is immediately recognizable for its brown yellow color – is also microbiologically very stable and ideal for the production of different types of cheeses.

How to dilute the rennet powder?

It is necessary to dissolve the dose of 4 grams (1 scoop) of powdered rennet in 30 cc of cold water and pour the liquid obtained into the boiler with milk at coagulation temperature (36 ° C). This quantity of rennet is sufficient to process 100 liters of milk.

How much rennet paste per 100 liters of milk?

The main feature of this type of rennet is that it has no residues. The product is available with a coagulating power of 1: 12,000. We recommend a serving of 8.5ml / 10.5g. of rennet per 100 liters of milk, to be dissolved a few minutes before use in 100 cc of cold water.

1: 12,000 = 1ml for every 12 liters of milk – 0.0.8ml for each liter of milk.

CALCIUM CHLORIDE

Most often, we find calcium chloride in cheese kits.
During the pasteurization and homogenization process to which the milk is subjected before being put on the market, it is responsible for a decrease in the calcium naturally contained in the milk.
Adding calcium chloride helps restore some of the lost calcium and will help you get a good, tough curd as well as more cheese production.
For calcium chloride about 2 -2.8 g. calcium chloride (which corresponds to about 40 – 60 drops) is needed for 10 liters of milk (carefully read the indications and dosage of the type of product used).

The values ​​provided are entirely indicative: these values ​​depend on many factors such as the coagulating strength of the rennet, the type of milk, the technology used, the temperature of the milk, etc.

SALTING

Brine

Salting cheeses by brine consists of immersing the cheese in a solution containing sodium chloride (salt), kept at a relatively low temperature, 4-5°C for soft cheeses and between 10 and 18°C for others, in order to cool the cheese rapidly and reduce the metabolic activities of the lactic flora.

The salt concentration varies between 15% and 25% and is usually expressed in degrees Baumè (Bé) or in gr / l, as well as in %. Higher concentrations are preferred for hard cheeses and lower concentrations for soft cheeses.

The volume of brine should be greater than that of cheeses (minimum 3-4 times), this means that for a cheese weighing 10 kg, 30-40 liters of saline is needed.

With the passage of time, the brine is progressively impoverished due to the absorption of salt by the cheeses and the dilution derived from the diffusion of the purge whey.

The microbiological profile is a critical point of the production process and must be monitored regularly: it is good practice to subject the brines to frequent filtration and sanitize them periodically by boiling. Brines should be kept in the dark to prevent the rancidity of exuding fat.

The salting of the cheeses, until a few decades ago, was done exclusively by hand or rather dry, they took the shapes and were practically rolled in fine or coarse salt and sometimes this procedure was repeated several times throughout the day.
The brines are also excellent for pasta filata, in particular provolone, caciocavalli, scamorze.
The brine is also cheaper for dairies, as once made, it lasts over time and when the salt concentration decreases, it is immediately put back inside.
Dry salting, on the other hand, apart from a considerable amount of extra time, it must also be calculated that a part of salt (about 20/30%) is lost in the dry salting phase.

Keep in mind that in brines, the higher the concentration of salt and the less the salt will penetrate inside the cheese, the lower it is and the more the cheese will absorb the salt.
For example, if we put a form of semi-cooked pecorino at 42 degrees in a 22% brine, for 8 hours and we keep the same cheese for 8 hours in an 18% brine, surely the latter will have a higher internal concentration of salt. than the other.

Dry salting

Generally dry salting is done with fine salt, because having a small grain, it is easier to rub it on the surface of the cheese and it penetrates better.
There are also old-fashioned dairies and cheesemakers who dry salt with coarse salt, mostly only by tradition.
Whether you use coarse, fine, iodized salt, etc., the flavor of the cheese does not change, it will always be the same.
The dry salting technique consists in rubbing the salt on the surface of the cheese several times (from three to more days).

Fresh cheese

The transformation of milk into cheese results from three fundamental stages: the coagulation of the milk, which gives rise to the curd, the purging of the whey and the maturing or maturation of the curd.

After the milk is collected, it is transformed into cheese: coagulation. It consists in the agglomeration and precipitation of casein and a large part of the fat present in milk, which are separated from the liquid part, the whey. Water, lactose, a modest amount of fat and whey proteins (lactalbumin and globulins) are dissolved in the whey, which make it possible to make ricotta.

Coagulation can occur by acidification, thanks to the action of ferments naturally present in milk, or more commonly by enzymatic method using rennet.

Once formed, the curd is broken with a special tool, the spino (giant whisk), into pieces the size of an orange or a walnut if you want to obtain soft cheeses, a bean for semi-hard cheeses, a grain of rice for hard cheeses. The curd is then cooked at various temperatures depending on the type of cheese produced. The minced curd, left to rest for a short period, contracts to form a solid mass which is extracted from the boiler in which it is located and distributed in the cheese molds where it can be pressed to obtain a more consistent paste.

Subsequently, the wheels are salted, dry or in brine, which has the purpose of flavoring, but also of increasing the shelf life of the cheese. At this point, the last phase begins, maturation or seasoning, which can last from a few hours to many months depending on the type of cheese.

Cheeses are not always fresh

Fresh cheeses, also defined as fresh pasta, are a type of dairy product that must be consumed immediately after production as it has a limited shelf-life, as they are not subjected to any ripening or seasoning process. These dairy products are characterized by a soft, grainy, moist and spreadable paste, basically white in color, without a crust and with a fresh, slightly acidic flavor. This category of cheeses is widely appreciated by consumers as they are products defined as lean and light, having fat titles, referring to the dry substance, which vary from 0 to 70%. In this regard it is possible to divide these cheeses into:

• Fresh lean cheeses (0-20% fat on the SS)

• Fresh fat cheeses (40-50% fat on the SS)

• Fresh “double cream” cheeses (> 60% fat on the SS)

Another interesting aspect of this type of product is the fact that it is possible to mix them with many other ingredients, such as herbs, spices and fruit, enriching them from an organoleptic point of view and thus making them more palatable.

Also, in this case it is possible that defects develop during the production phase which therefore make the product unusable from a commercial point of view. Such defects can arise during all stages of production, as there is always the possibility that during processing technological errors may occur that lead to the onset of various defects, described below.

Acidity

It is a defect caused by the slow acidification of the milk. The main causes are attributable to the use of unsuitable lactic ferments or suboptimal acidification temperatures. These two conditions can be consequential: often the sudden rise in temperature, and a slightly contaminated base milk, leads to an excessive lowering of the pH and therefore to a cheese that is too acidic.

It should be remembered that acidity, when kept at a suitable level, is actually a great tool for protecting cheese from altering agents.

As with all the cheeses we have talked about and will talk about, the best remedy to avoid the onset of any type of defect is to maintain the correct hygiene and health regulations. This includes the environment, instrumentation, equipment, containers and personnel, who must work cleanly. Another essential prerogative to satisfy the qualitative requirements is the processing of a high-quality milk, that is a milk that has a microbial and somatic cell count that respects the parameters. It should also be remembered that the evaluation of milk is also important for the dairy yield. The higher the quality of the milk, the greater the ability to process it, thus leading to an excellent cheese. As for the excessive acidity in particular, which can occur in some cheeses, the preventive techniques concern a correct choice of the starter, and correct temperature maintenance, avoiding thermal changes.

Bitter taste

This defect occurs both when there is an excess of proteolysis by microorganisms and lactic ferments and when the whey is not effectively separated during centrifugation.

If an excess of bacterial proteolysis is observed, so that the curd is diluted and not very compact, the selected starter must be promptly replaced with less proteolytic enzymes. This defect is caused by pungent tasting peptides, so don’t push the proteolysis too far. Among the bacteria are the coliforms those that if present in high quantities cause the formation of a cheese with an unpleasant aroma. It is a defect that can be prevented by using a correct amount of rennet, which also must not be rich in pepsin and low in chymosin; rennet with these characteristics can only be taken from animals fed exclusively with milk.

Quality

Fresh cheeses, due to their high humidity and the long manufacturing cycle to which they are subjected, characterized by multiple technical operations, are strongly subject to microbial contamination, mainly due to bacterial, such as coliforms and fungi. The latter can develop during the manufacturing process on several occasions: when the hygiene rules are not respected and the systems are not adequately washed and sanitized after each production cycle, or during the mixing and packaging phases of the ingredients.

For fresh cheeses, given their delicacy and therefore the high probability of incurring quality defects and contamination by microorganisms, it is possible to add potassium sorbate as an anti-mold when mixed. The presence of 0.1% of this antifungal is acceptable in the finished product. The precautions to be taken to keep the cheese in optimal conditions are mainly linked to the cold chain. The packaged cheese must be quickly cooled and stored at a temperature of 4 ° C throughout the distribution period.

The Feta

For a practical example we are talking about Feta, a fresh cheese made from sheep’s milk, which can help you understand the defects that may occur during the processing of fresh cheeses.

When too rapid acidification occurs (pH <4.6 in 24h), when temperatures are too high and the curd, at the time of breaking, is too small and / or irregular, the paste is acidic, crumbly and chalky. On the contrary, when the dough is too hard and moist, this is caused by a too coarse cut of the curd, as well as by too rapid acidification and non-turning. Excessive acidification caused by a high temperature makes the curd almost without consistency. During the ripening process, if there is a saline imbalance in the brine or cheese, an excess of proteolysis, excessive or insufficient acidification and too low temperatures, the Feta does not mature and could become slimy. It is also possible that defects related to the organoleptic quality of the cheese may also arise, including: the development of a yellowish color when the Feta is too exposed to the air; unpleasant flavors that occur when the milk is not pasteurized, the temperatures are too high in the maturation cell or due to putrefaction processes conducted by spore-forming bacteria, as well as due to the presence of fungi. The brine process can also cause defects, in particular when the dough becomes stringy and mucilaginous: this usually happens when the cheese is contaminated with bacteria belonging to the Bacillaceae family due to insufficient acidification of the dough. At the same time the brine can develop gases, caused both by the proliferation of halophilic yeasts and coliform bacteria, and by an insufficient salt concentration and too high temperatures.

Defects that occur during the production of Feta can be prevented, as well as by respecting the hygienic-sanitary rules along all the phases of cheese making, and by resorting to good quality milk, also by increasing the thermization temperatures, since it may happen that the treated milk still has a microbial load. The control of acidity and temperature is not the only one that must be carried out during the processing, sometimes the defects are of a technological nature, in this case it is the operator who must avoid carrying out a procedure in a superficial manner, and check his gesture especially when it comes to delicate cheeses such as fresh ones.