Process for manufacturing dairy products

Improved process for manufacturing dairy products, characterized by the fact that it comprises the use of an effective amount of at least one of the gluconic and glucoheptonic ions at the latest at the time at which there is a risk of the occurrence of phagic attack of said ferments.

BACKGROUND OF THE INVENTION 
The invention relates to an improved process for manufacturing dairy 
products. 
It is known that the manufacture of dairy products--this expression 
comprising yogurts, fresh cheeses, renneted cheeses and "large 
curds"--comprises the formation of what is called the curd which is 
itself, at least in part, the result of the acidifying action on the 
starting material--namely the milk--of one or several acids and/or of one 
or several bacterial microorganisms of the family of acidifying lactic 
ferments, possibly in the presence of a coagulating enzyme and/or of one 
or several lactic ferments with flavoring action. 
It is also known that microorganisms of the family of lactic ferments, just 
as other bacteria, when they are in the presence of specific 
bacteriophages, are attacked and lysed, that is to say destroyed, by these 
viruses which grow at their expense. 
Now, the growth of the bacteriophages and the subsequent destruction of the 
lactic ferments is manifested, according to the nature of the lactic 
ferments concerned, by a disturbance of the acidification--and, 
consequently, of the formation of the curd, of which disturbance the 
economic consequences may be disastrous--and/or by disturbance of the 
organoleptic qualities of the dairy products obtained. 
It follows that counteracting the proliferation of bacteriophages or more 
simply of phages, which withstand conventional pasteurisation treatments, 
constitutes one of the major preoccupations of the dairy products 
industry. 
Thus, it has been proposed to resort to disinfectants such as 
hypochlorites, iodophores and formol; but even with strict hygiene 
(particularly by sterilization of the air and of the equipment from the 
pail to the manufacturing tank), it is difficult and expensive to remove 
the bacteriophages completely. 
It has also been proposed to resort to take advantage of the fact that the 
phages need the presence of calcium ions to be able to infect bacteria. 
Thus, so-called "anti-phage" culture media, adapted to remove or block 
calcium ions, have recently appeared on the market; they are, generally, 
complex mixtures containing milk dehydrated or not, growth factors and 
large amounts of phosphates to sequester the calcium ions. 
Now, these large amounts of phosphates present in the anti-phage media can 
cause metabolic damage to lactic yeast cultures. 
And, especially, the complexing of the calcium has a negative influence on 
the cheese making suitability, in particular on coagulation (lengthing of 
the coagulation time, less firmness of the gel). 
It has again been proposed either to eliminate the so-called maturation 
phase of the milks for cheese making, or to change lactic ferments each 
time the tank is refilled. 
It is true that, in the first case, the lactic ferments being directly 
seeded into the manufacturing tank during the refilling of the latter, the 
phages present are trapped in the curd network formed during the clotting 
after the addition of the rennet which comes into action preferably as 
soon as possible after the seeding; however, besides the high cost of this 
method of working, the suppression of ripening is not without consequences 
and remains therefore necessary in the case of milks treated thermally by 
cold storage or a pasteurisation treatment. 
In the second case, the risk of attack of the phages and the consequences 
of the latter are considerably reduced but, on the other hand, the 
production costs are considerably increased; in addition, the rotation of 
the strains, that is to say the change of the strain of lactic ferments on 
each replenishment, results in variations in the matter of acidification 
times, in the matter of the amount of ferments to be added and especially 
in the matter of the organoleptic qualities of the finished dairy 
products. 
GENERAL DESCRIPTION OF THE INVENTION 
Now, Applicants, who have had the merit of discovering that gluconic and 
glucoheptonic ions inhibited the development of specific phages of lactic 
ferments, have perfected an improved process of manufacturing dairy 
products, characterized by the fact that it comprises the employment of an 
effective amount of the above-said ions at the latest at the time when 
there is a risk of phagic attack occurring. 
According to an advantageous embodiment, the above-said improved process of 
manufacturing dairy products comprises at least one of the following 
conventional steps, namely: 
that of maturation of the milk in the course of which the latter is placed 
in the presence of acidifying lactic ferments and/or flavoring lactic 
ferments, 
that of renneting, 
that of curd formation and 
that of ripening as well as 
that comprising conventional mechanical treatments between the steps of 
curd formation and ripening, 
said process being characterized by the fact that an effective amount of at 
least one of gluconic and glucoheptonic ions is employed at the latest at 
the moment of the use of the lactic ferments. 
In practice, the ions concerned are employed at the time of the maturation 
phase. 
Due to the process according to the invention, it becomes possible to act 
effectively against the development of the specific phages of the 
above-said lactic ferments without unfavorable effect on the manufacture 
of the desired dairy products and the organoleptic properties of the 
latter, thus protecting said lactic ferments against phagic attack during 
the acidification step. 
In an advantageous embodiment of the above-mentioned process, the effective 
amount of gluconic and/or glucoheptonic ion employed is from 2 to 500 
g/hectoliter of milk. 
The invention is directed also, and this by way of agents limiting the 
proliferation of the specific phages of the lactic ferments, to chemical 
compounds releasing gluconic and glucoheptonic ions within the scope of 
their use in the process according to the invention. 
Proposing, consequently, to combat proliferation of the specific phages of 
lactic ferments in the dairy products industry, advantage is taken of the 
surprising and unexpected ability of gluconic and glucoheptonic ions, that 
Applicants have had the merit of discovering and due to which the 
development of the above-said phages is inhibited in their presence. 
Consequently, procedure is preferably such that the above-said ions are 
present in the milk constituting the raw material for the manufacture of a 
dairy product of the type concerned at the moment when the lactic ferments 
are used. 
The milk used may be a milk or a mixture of milks from any source, 
reconstituted or not, raw or having undergone a prior heat treatment; it 
may be standardized in fat and/or in inorganic matter; it can also be a 
milk concentrated, for example, by ultra-filtration. 
The gluconic and/or glucoheptonic ion may be introduced by the 
corresponding acid, by the alkali salts, among which are ammonium salts or 
by alkaline earth salts of these acids; preferably, the gluconic ion is 
introduced in the form of a gluconolactone or glucoheptonolactone, the 
glucono-delta-lactone being particularly preferred. 
The acid, the salt or the lactone may be employed in the form of a solution 
in water or in milk, or in powder form, in which case their dispersion in 
the milk and their solubilization are ensured by any suitable stirring 
means. 
The gluconic and/or glucoheptonic ion having to be present at the time of 
employment of the lactic ferments, they are introduced into the raw milk 
or into the milk which has previously undergone heat treatment or again in 
the so-called "large curd" tanks, in which the lactic ferments are 
cultivated for their use in the process of manufacturing the dairy product 
concerned or in the maturation tanks. 
Advantageously, the amount of gluconic and/or glucoheptonic anion used is 
from 5 to 250 g/hl of milk and, preferably, it is from 25 to 100 g/hl of 
milk.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The invention will be well understood by means of the illustrative examples 
which follow and which comprise the description of advantageous 
embodiments. 
In these examples, the effectiveness of the process according to the 
invention is shown. 
on the one hand, by direct determination of the reduction of the number of 
phages with respect to a control in a culture of lactic ferments intended 
for the dairy products industry, that is to say at the level of 
manufacture of the "large curd" (Example 1), 
on the other hand, and still for each case with respect to a control, in a 
certain number of manufactures of particular dairy products (Examples 2 to 
4). 
EXAMPLE 1 
Manufacture of the Large Curd 
Into two separate containers, preparation of two "large curds" is 
simulated, the first according to the prior art, the second with the 
application of the features of the process according to the invention. 
The lactic ferment used is the lyophilised strain Streptococcus lactis IL 
561 lyophilisee (kindly supplied by Madame M. C. CHOPIN of I.N.R.A. of 
Jouy-en-Josas, France). 
This strain is inoculated into 50 ml of M 17 culture medium whose 
composition is described in the work "Technique d'Analyse et de Controe 
dans les IAA", vol. 3, page 110, ed. APRIA. 
4 ml of the culture thus produced after 24 hours of incubation at 
25.degree. C. are introduced respectively into two Erlenmeyers flasks each 
containing 150 g of milk, autoclaved previously for 30 minutes at 
95.degree. C., one of the two Erlenmeyers containing in addition, 
conforming with the process according to the invention, 36 mg of 
glucono-delta-lactone or GDL in the form of a solution containing 9 g of 
GDL per liter, in other words 4 ml; the whole is maintained in both cases 
at 25.degree. C. for about 15 hours. 
The curded milk so obtained in the two Erlenmeyers is used to seed in its 
turn respectively 5 liters of sterilized; it is left to incubate at 
25.degree. C. for 15 hours. 
The final acidity of the medium which constitutes the "large curd", is 
80.degree. D in both cases. 
It is on the two "large curds" cultures thus prepared that a count of the 
phages is carried out. 
To do this, the so-called method of "phages "lysed areas" is used which was 
described by W. A. COX in 1980 in an article entitled "Detection and 
enumeration of mesophilic lactic bacteriophages", p. 29-36 of "Starters in 
the manufacture of cheese", IDF FIL Doc. 129, Bruxelles. 
In practice, procedure is as follows. 
On a gelose base constituted from M 17 culture medium (whose composition is 
indicated in the work "Technique d'Analyse et de Controle dans les IAA", 
vol. 3, page 110, ed. APRIA.) and from 18 g of agar/1, is introduced 
0.1 ml Streptococcus lactis culture, strain IL 561 (cultivated on M 17 
medium and aged for 15 hours), 
0.05 ml of a molar solution of CaCl.sub.2, 
0.1 ml of the phage suspension obtained after filtration of the large curd 
on a 0,2 .mu.filter; this filtrate can then be diluted. 
The phages present are rapidly fixed on the bacteria; the adsorption is 
terminated after about 5 minutes. 
Then in each case 2.5 ml of soft gelose obtained by dissolving agar in M 17 
culture medium (4 g of agar per liter of M 17 medium) is then added. 
The appearance of the lysed zones occurs within 10 hours. 
In the case of the first test, the method concerned shows that, in neither 
of the two cases, were there phages in the culture medium. 
The experiment was then continued respecting the conditions actually 
prevailing in the industry. 
In other words, a "large curd" was prepared every 3 days for 4 months in 
the same container by means of inoculi derived from the same storage 
stock, that is to say from the freeze dried strain. 
On each tenth preparation of the large curd, the test described above was 
recommenced and the number of phages present was determined. 
The first test being denoted by the number N1, the four following tests 
carried out respectively after the first, second, third and fourth months 
were given the numbers N2 to N5. 
In Table I below, is indicated for each of the tests the number of phages 
detected. 
TABLE I 
______________________________________ 
Number of phages present 
Test Culture according 
Culture according 
Number to the prior art 
to the invention 
______________________________________ 
N1 No phage No phage 
N2 Absence of phage 
No phage 
N3 10.sup.2 phages/ml 
Detection of 
phages &lt; 10/ml 
N4 10.sup.11 phages/ml 
10.sup.2 phages/ml 
phagic accident 
N5 10.sup.11 phages/ml 
10.sup.2 phages/ml 
______________________________________ 
The superiority of the process according to the invention is clear from the 
indications shown in this Table. 
EXAMPLE 2 
Manufacture of Cheddar 
It is recalled that the manufacture of cheddar comprises the following 
steps: 
a) Maturing of the milk 
To 500 l of milk at a temperature of 31.degree. C. (pasteurised at 
72.degree. C. for 16 seconds), placed in a double jacketed tank provided 
with a stirrer, is added 1.5% of lactic ferments (Streptococcus lactis 
strain) . 
b) Curd formation 
After 25 minutes, 90 ml of a strong rennet 1:15000 is added. It is stirred 
at average speed (10 r.p.m.) for 5 minutes. After stopping the stirrer, 
the stirring blades are removed. 25 minutes is allowed for the formation 
of the curd. 
c) Cutting up 
When the curd has reached the desired firmness (about 1 hour after 
rennetting), the cutting follows. 
d) Cooking of the grains of curd 
After cutting up and still in the same tank, the cooking is started 
gradually, by injecting steam into the double Jacket of the tank. The 
temperature is increased up to 38.degree. C. at the rate of 2.degree. C. 
per 5 minutes, with gentle and constant stirring. The temperature of 
38.degree. C. is maintained for a further 45 minutes. 
e) Drainage 
The stirring is stopped and the free whey is removed. The temperature of 
the tank is kept at 38.degree. C. 
f) Cheddarisation 
The curd freed from whey is cut up lengthwise to permit good exudation of 
the whey contained in the curd for 15 minutes. Then the curd is cut in the 
other direction; the blocks so obtained are separated and left to stand 
for 15 minutes at a temperature of 38.degree. C. After cheddarisation, the 
titratable acidity must be from 0.50 to 0.60%. The optimum pH of the curd 
was 5.2-5.3. 
g) Crumbling of the lumps of curd 
The lumps of curd are crumbled above the tank so that the crumbs may fall 
into the latter. 
h) Salting 
Salt is sprayed on to the crumbled curd in the proportion of 1 kg per 
estimated 500 kg of curd. The salt is added in three batches in order to 
facilitate its dissolution. 
i) Molding and pressing 
A given amount of curd (for example 15 kg) is taken and placed in a metal 
mold; a pressure of 1.7 bar is applied for 18 hours. 
j) Drying 
After stopping the pressing, the cheese is placed, for 2 or 3 days, in a 
drying chamber at 13.degree. C. and 70% humidity with daily turning over 
of the cheese. 
k) Ripening 
The cheese is surrounded with a film of paraffin by dipping for 6 seconds 
into liquid paraffin of which the temperature is 118.degree. C. After 
hardening of the paraffin, the cheese is kept for refining for at least 60 
days at 4.degree. C. in an atmosphere with 85% relative humidity. 
For the requirements of the example, a first specimen of cheese is 
manufactured by proceeding as it has just been described and in parallel a 
second specimen by proceeding in the same manner except that the 
maturation of the milk is performed by adding to pasteurized milk 
(72.degree. C. -16 seconds) cooled to 31.degree. C., an amount of 1 g of 
GDL in powder form per liter of milk, and then the ferments coming from 
the strain Streptococcus lactis (IL 561). 
Tasting of the two specimens of cheese did not show a difference of 
appearance, of texture and of organoleptic properties. 
These two manufactures were repeated ten times (during a period of 12 
months; they were pilot tests). 
The phagic infection which occurred in the manufactures, not comprising the 
addition of gluconic ion according to the invention, required 7 changes of 
strains during this period. 
In the case of the manufacture according to the invention, it was only 
necessary to change the strain once. 
EXAMPLE 3 
Manufacture of Cottage Cheese 
It is recalled that the manufacture of cottage cheese comprises the 
following steps. 
500l of milk is pasteurized by treatment at 72.degree. C. for 16 seconds. 
The milk thus pasteurized is then cooled to 31.degree. C. and placed in a 
double Jacketed tank provided with a stirrer. 
Lactic ferments are added (Streptococcus lactis, Streptococcus cremoris and 
Leuconostoc citrovorum) during the filling of the tank, this addition 
being done in the form of powder and in the amount of 5%. 
Milk comprising lactic ferments is kept at the temperature of 31.degree. C. 
for 5 hours until the formation of curd. The acidity of the serum is then 
0.52% and its pH 4.6. 
The curd is cut up into blocks which are allowed to stand for 15 to 30 
minutes. Water at the temperature of 46.degree. C. is introduced into the 
double jacket of the tank and the cooking of the curd is started with 
gentle stirring (10 rpm). 
The temperature of the water introduced in the double jacket is increased 
very slowly to 49.degree.-52.degree. C. to cook the curd, an operation 
which should be continued for about 100 minutes to obtain the desired 
firmness. A portion of the serum is removed by simple evacuation and then 
the blocks of curd are allowed to stand for 10 to 30 minutes. 
After cooling to 29.degree. C., the curd is washed with demineralized water 
for 10 minutes and then drained. After further washing, the curd is 
brought to 15.degree. C. It is washed a third time and then cooled to 
4.degree. C. 
After draining, the curd is cut up into grains; care is taken that the 
temperature does not rise above 7.degree. C. 
A cream is prepared which has to be mixed with the cut up curd to provide 
the final cottage cheese. 
To do this, 56.3% by weight of whole milk is mixed with 39.7% by weight of 
sweet cream and with 4,0% by weight of salt. 
The cream and the cut up curd are mixed in the proportion of 167 liters of 
cream per 500 liters of curd, mixing gently for 15 minutes. 
The finished product has the following properties: 
fats:4.5% by weight 
humidity:79 % by weight 
pH:5.2. 
For the requirements of the example, a first specimen of cottage cheese is 
manufactured by proceeding as it has just been described and, in parallel, 
a second specimen by proceeding in the same manner except that at the same 
time than the lactic ferments is introduced an amount of 0.5 g of GDL, in 
powder form, per liter of milk. 
These two manufactures were repeated 15 times (during a period of 12 
months; they were pilot tests). 
Phagic infection occurring in the manufactures, not comprising the addition 
of gluconic ion according to the invention, necessitated 5 changes of 
strains during this period. 
In the case of the manufacture according to the invention, it was not 
necessary to change the strain through the whole year. 
EXAMPLE 4 
Manufacture of a Pressed Cheese of Saint-Paulin type 
It is recalled that the manufacture of cheese of the type concerned 
comprises the following steps. 
An amount of 500 liters of milk is brought, under normal industrial 
conditions, to 26.7 g/l of fat. 
Pasteurization at 72.degree. C. for 40 seconds follows, then it is cooled 
again to 31.degree. C. 
The milk thus heat treated, was brought into a tank designated for the 
manufacture of pressed cheese; it was on oval tank of the 3000 l type 
manufactured by the Guerin S. A. 79210 Mauze-sur-le-Mignon (France) 
equipped with two curd cutters. 
The pH measured on the whole milk at the moment of its introduction at 
31.degree. C. into the tank was 6.65. An addition of soluble calcium salt 
was then made in the form of 490 ml of a solution of 510 g/l of calcium 
chloride in water. 
The maturation of this milk was carried out by an addition of mesophilic 
lactic ferments prepared under the following conditions: a concentrated 
and frozen preparation of mesophilic lactic ferments, marketed by the 
Laboratoires Miles--Division Marshall (rue des Longs Reages--28280 
Epernon--France), was cultured in the nutrient medium Marstar marketed by 
the sae Laboratories, applying strictly the conditions of preparation 
recommended by these Laboratories. 
An amount of 3 liters of this culture (0.6% in volume with respect to the 
volume of treated milk) is mixed with the milk at the moment of 
introduction of the latter into the maturation tank. 
After 30 minutes of maturation, the pH of the milk was 6.60 and its 
temperature 31.degree. C. 
The renneting was performed in the maturation tank; to do this, there was 
introduced per liter of milk an amount of 0.33 ml of a commercial 
preparation of coagulating enzymes containing 520 mg of chymosine per 
liter. 
The setting time was 16 minutes; the curd formation was allowed to 
continue, under traditional conditions, for 6 minutes; this additional 
period was called hardening time. 
The coagulum was then cut up in the tank by slow rotation of the two curd 
cutters which each make 3 turns in 1 minute. 
The cut up coagulum was left to stand for 5 minutes. 
Cutting up followed by means of the two curd cutters, by bringing the 
latter for 1 minute to a rotary speed of 12.5 rpm, then for 3 minutes to a 
speed of 10 rpm. 
Following this treatment, the curd grains had reached the desired size 
which was comprised between 0.5 and 1 cm. The curd-whey mixture was left 
to stand for 5 minutes. The pH was then 6.58. 
The subsequent operation of washing the curd included the removal of the 
supernatant whey (which represented 33% of the initial volume of 500 
liters) by means of a pump, then the addition of an equal volume of 
potable water of temperature 32.degree. C. 
It was followed by a mashing, reversing the direction of rotation of the 
curd cutters; his mashing included a first phase of 6 minutes at high 
speed (13 rpm) in order to individualize the grains which have a tendency 
to agglomerate, then a second phase of 2 minutes at a speed of 7 rpm. The 
temperature was then 31.5.degree. C. 
The curd-whey assembly was transfered to a prepressing tank (length 1.82 m; 
width 1.75 m; height 0.62 m, whose two opposite vertical surfaces were 
perforated to permit the drainage of the whey), equipped previously 
internally with a linen cloth of weft of the order of 2 mm. This cloth was 
then folded over the upper part of the curd so as the completely enclose 
it. The operation of prepressing in the tank was carried out in 5 minutes 
by distributing a load over the whole upper surface such that there 
resulted therefrom a regular pressure of about 600 Pa (6 g/cm.sup.2). 
In this way a firm and cohesive slab of curd was obtained which was cut up 
into loaves with a square base of 38.5 cm side; these loaves were 
introduced into individual molds and placed under pressure in premises at 
18.degree. C. The pressing is carried out for about 45 minutes, with a 
pressure of about 6.10.sup.3 Pa (60 g/cm.sup.2), turning over of the 
loaves (with a view to regularizing the shape) being carried out 15 
minutes after the start. 
At the end of pressing, each loaf was cut up into twelve parallelepipeds 
which corresponded to the final size of the cheeses (length:19 cm, width 
and height:6.5 cm). The pH is then 6.30. 
The lactic ferments present in said cheeses then continued the 
acidification so as to bring the pH to 5.6 after 4 hours. 
Then salting of the cheeses followed. 
After 18 hours, this operation called pickling was finished; the pH was 
5.40. 
Analysis of the finished cheeses showed that the total dry matter was 
50.08%, the total fat 20.5% and the ratio fat/dry matter (F/D) 40.93. 
For the requirements of the example, a first specimen of cheese was 
manufactured by proceeding as it has just been described and, in parallel, 
a second specimen by proceeding in the same manner, except that at the 
moment of maturation, 0.2 g of powdered GDL was added per liter of milk. 
On emerging from the pickling, analysis of the manufactured cheeses with 
the addition of GDL Gave the following values: 
total dry matter:52.10 
total fat:20.75 
F/D:39.83. 
These two manufacturers were repeated 20 times during a total period of two 
years. 
The phagic infection which occurred in the manufactures, not including the 
addition of gluconic ion according to the invention, necessitated 7 
changes of strains during this period. 
In the case of manufactures according to the invention, it was not 
necessary to change strain even once.