Process for making pasta filata type cheese

In the manufacture of Cheese of the "pasta filata" type, an intermediate product is obtained by carrying out the coagulation of a protein concentrate, obtained by ultrafiltration of milk, by means of an acid whose concentration is selected so that the calcium concentration, in the coagel resulting from the coagulation, after separation of liquid, is below about 1.5% calculated on the weight of fatfree dry solids.

This invention relates to a process for producing a cheese of the "pasta 
filata" type, from a protein concentrate obtained by ultrafiltration of 
milk. 
"Pasta filata" refers to a type of Italian cheese with a fibrous structure, 
for instance, Mozzarella. In the production of such cheeses there is a 
kneading or stretching step at elevated temperature. In order that the 
final product have the desired features, the intermediate product which is 
subjected to the kneading and stretching, must have certain properties. 
The intermediate product constitutes, substantially, coagulated casein and 
fat, a so-called coagel, which can be made by enzymes, that is to say by 
rennet, by a bacterial culture or by direct acidification. 
In recent years the dairy industry has developed cheesemaking processes in 
which a casein concentrate, obtained from milk by ultrafiltration, is 
coagulated. If such a casein concentrate is to be utilized for the 
manufacturing of "pasta filata" cheese, its calcium content must be 
reduced. This is conventionally done by dilution with water, with the 
mixture so obtained being treated by one more subsequent ultrafiltration 
steps. The object of this operation is to lower the calcium concentration 
to such a value that in the subsequent coagulation a coagel is obtained, 
which can be employed in the kneading and stretching steps referred to, 
leading to the final "pasta filata" cheese. 
The manufacture of such cheese is disclosed, for instance in J. Dairy Sci. 
(1978) Vol. 61, No. 6, p. 701-709. 
By carrying out the process in this way, a coagel is obtained suitable for 
processing directly to "pasta filata" type cheeses in a simple and 
inexpensive way. 
It is especially suitable to carry out the initial separation by 
ultrafiltration in such a way that the fatfree dry solids concentration of 
the concentrate is brought to be within the range between about 13 and 
about 28% by weight. 
In a preferred embodiment the coagulation is carried out by adding the 
concentrate to a solution of the acid. 
The coagulation is best performed so that the separated coagel shows a pH 
of from about 4.9 to about 5.2. 
The most favorable temperature range for performing the coagulation is from 
about 55.degree. to about 65.degree. C. 
Various acids may be used for the coagulation. Particularly suitable acids 
have proved to be citric acid and acetic acid. Acids like lactic acid or 
tartaric acid can also be used. Even mineral acids such as 30% Nitric 
Acid, 80% Phosphoric Acid, and the like can be used, provided that a 
calcium-binding agent like EDTA (ethylene diamine tetraacetate) is added. 
The concentration of acid is, of course, determined by that required to 
obtain the necessary reduction in calcium and this will depend on the acid 
selected and the properties of the particular concentrate. However, in 
general, the solution to which the concentrate is added will contain 
between about 0.05% and about 1.0% by weight of the acid. 
Following coagulation, in the liquid separation step, the dry solids 
content of the coagel is brought to between about 40% and about 48% by 
weight. The fat-free dry solids content is between about 25% and about 33% 
by weight. 
Two ultrafiltration steps involve substantial additional expense. It is an 
object of this invention is to provide a process of the type mentioned 
which is simple and economical, which can be performed continuously, and 
wherein a so-called "melting" step for the coagel, before the kneading and 
stretching step, can be omitted. 
A process according to the invention, starting with a milk raw material, 
may comprise the following steps: 
(a) optionally, a conventional pretreatment of the milk such as 
homogenization and pasteurization , 
(b) ultrafiltration of the milk, with or without such homogenization and 
pasteurization, into: 
a filtrate containing lactose and mineral compounds; and 
a concentrate, containing fat and proteins at a substantially higher 
concentration than raw milk. 
(c) optionally, pasteurization and homogenization of the concentrate, 
coagulation of the concentrate, with or without the homogenization and 
pasteurization referred to, by an acid, to a coagel. 
(e) separation of liquid from the coagel to increase the dry solids content 
of the same. 
(f) kneading or stretching of the coagel. 
Subsequently the kneaded and stretched product may be treated to make the 
cheese in the conventional way. 
According to the invention the coagulation is carried out with acid in such 
a concentration that the calcium concentration, calculated as % Ca on 
fatfree dry solids in the coagel after the separation of the liquid, is 
below about 1.5%.

Referring to the drawing, a plant for carrying out the process of the 
invention comprises a series of units, which are coupled by pipes, namely 
a first homogenization apparatus 1, a first pasteurization apparatus 2, a 
first cooler 3, an ultrafilter 4, a second pasteurization apparatus 5, a 
second homogenization apparatus 6, a second cooler 7, a tubular reactor 8, 
a whey sieve 9 with a liquid discharge opening 14 and a coagel outlet 15, 
and a cheese making unit 10, not described in detail, for kneading, 
forming, chilling, salting and packaging. A pipe 11 for the addition of 
acid is connected to the reactor 8. The ultrafilter is provided with a 
filtrate discharge outlet 12 and a concentrate discharge outlet 13, which 
latter is connected to the second pasteurization apparatus 5. 
To exemplify the process according to the invention data from the actual 
manufacture of cheese in a plant of the type described above will be 
given. In this case a 10 meter pipe with an inner diameter of 50 mm, shown 
as 8 in the drawing, was used as the tubular reactor. 
As raw material, milk containing 2.95% fat and 3.3% raw protein was used, 
which milk was homogenized in the homogenization apparatus 1 at 150 bars 
and 60.degree. C., and was pasteurized in the pasteurization apparatus 2 
at 79.degree. C. for 14 sec. It was then cooled to 55.degree. C. in the 
cooler 3. The milk thus cooled was separated in the ultrafilter 4 to give 
a filtrate, which was discharged through the outlet 12, and a concentrate 
containing 34% dry solids, 14.2% fat and 13.1% raw protein. This 
concentrate was pasteurized in the pasteurization apparatus 5 at 
80.degree. C. for 30 sec. and was then homogenized in the homogenization 
apparatus 6 at 85 bars and 60.degree. C. It was then cooled in the cooler 
7 to 15.degree. C. Then the cooled concentrate was fed to the tubular 
reactor 8 at a rate of 500 liters/hour simultaneously with a 0.4% by 
weight citric acid solution having a temperature of 75.degree. C., pumped 
into the reactor 8 at a rate of 1500 liters/hour. After dewatering in the 
whey sieve 9, which sieve had a mesh size of 150.times.200/.mu.m, the 
coagel had a dry solids content of 48%. The calcium concentration, 
calculated on fatfree dry solids, was 1.25% Ca. 
The coagel was then fed into the unit 10 for kneading and forming into 
filaments of 40 mm diameter, which filaments were cooled in cold water, 
salted in saturated salt lye for 2 hours and then packed in vacuum bags. 
The final product was a Mozzarella having a quality equal to that of 
conventional manufacture, and having the following composition, by weight 
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Dry solids 46.5% 
protein 21.9% 
ash 4.12% 
fat content 19.2% 
salt 2.4% 
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The calcium concentration, calculated on fatfree dry solids, was 1.25%. 
Corresponding trials were made using other acids. Using 0.8% acetic acid, 
the final product contained 1.42% Ca on fatfree dry solids. Using 0.8% 
lactic acid gave 1.29% Ca and 0.8% tartaric acid, 1.33% Ca. On the other 
hand, when phosphoric acid was used, without EDTA, 1.63% Ca was obtained 
and the product was unacceptable.