Product and process for its manufacture
Field of the invention
The invention relates to a process for the manufacture of a soured
milk product by means of physical modification of the milk raw material and a
cross linking enzyme that strengthens the texture. The invention also relates to
a milk product that contains physically modified milk raw material fat globules
and has been treated with a cross linking enzyme.
Background of the invention
In the preparation of sour milk products, it is typical that starter is
added to homogenized, heat-treated milk, which, as it sours the milk, provides
it with the texture and taste properties typical of the product.
Conventionally all the necessary raw materials and ingredients,
such as sweetener, flavourings and texturizers, are added to the milk, and the
milk mixture is then typically homogenized and pasteurized prior to souring.
The homogenization is conventionally done by using either one- or two-phase
homogenizers, and the typical homogenization conditions are a temperature of
55 to 80 °C, more typically of 65 to 70°C and a pressure of 00 to 250 bar, more
typically of 50 to 200 bar. The milk mixture is soured or the acidity is adjusted
to a pH value specific for each product in some other manner. After this, the
texture is optionally broken and cooled to a packaging temperature, the
necessary flavourings (e.g. jam) are added and the product is packaged.
The effects of milk high-pressure homogenization on the particle
size, water retention, syneresis, and texture of yogurts at a pressure of 300 to
3500 bar have been extensively studied in the last few years (Lanciotti, R. et
al., Food Microbiology, 2 1 (2004) 753 - 760; Ciron, CLE. et al., Int. Dairy J. 20
(201 0) 314 - 320). The high mechanical forces / shear forces directed to milk in
high-pressure homogenization help reduce the size of the fat globules in milk.
It is known that the particle size of an emulsion can be reduced by ultrasound
treatment or power ultrasound treatment.
Basic information exists on the advantageous effects of highpressure
homogenization and ultrasound technology of milk raw material on
the consistency, such as viscosity and structural (gel) hardness, of a sour milk
product and on the reduction in syneresis. However, the problem in the preparation
of low-fat products in particular is the poor resistance to downstream
processing, such as modification and texture breakage.
Publication EP1 464230 describes the preparation of desserts and
soured products at a pressure of 400 to 2000 bar from a homogenized milkbased
emulsion.
Publication US 641 6797, Kraft Foods, describes a preparation process for a cream cheese (Philadelphia cream cheese), in which transglutaminase and starter are added to the raw material liquid, it is soured to a pH value
of 4.5, and then the soured milk-based emulsion mixture is homogenized, if
desired, at a high pressure (approximately 690 bar, 10 000 psi) to modify the
soured product mixture. In the process described in the publication, the down
stream processing of the cream cheese, or unripened cheese, becomes easier.
Conventionally, increasing the dry content of milk by evaporating,
concentrating and/or adding powder to milk, for instance, and decreasing the
dry content of milk, among other things, have been used in adjusting the tex
ture of sour milk products. The protein content of raw material milk affects the
texture of the final product, and the texture of a milk product can be modified
as necessary by increasing or decreasing the protein content. For instance,
the protein content of yogurt milk can be increased by evaporation or by adding
protein powders, such as milk, whey and casein protein powder, therein.
Protein supplements based on non-milk proteins are also useful. Alternatively,
the thinning of the texture can be done by adding milk permeate, cheese whey,
acid whey, such as quark and/or cottage cheese whey, or water to the raw ma
terial milk.
It is also known that by using a crosslinking enzyme in sour milk
products, the texture can be hardened and thickened and modified to be more
fine texture, and the separation of whey reduced. To minimize structural prob
lems, it is well known in the art to add to the protein source a crosslinking e n
zyme that modifies the texture. The processes conventionally use milk
homogenized at low pressures ( 100-250 bar) for the preparation of soured milk
products. A problem then arises that the processes and their control are further
complicated and become more difficult as more preparation steps are added.
Thus, simple product formulations and cost-effective preparation processes
are needed to control the problems, such as post-souring and structural problems
like a powdery texture, caused by the generally known processes to the
products.
In general, problems with the known processes include the altera
tion of the organoleptic properties of sour milk products and their poor shelf-life
during storage. Syneresis, separation of whey and structural problems occur in
the products. Problems related to downstream processing, such as mass
modification and texture breakage, as well as to shelf-life are especially em
phasized in low-fat sour milk products.
Brief description of the invention
The invention relates to a process for the manufacture of a sour milk
product by means of physical modification of the milk raw material and/or the
fat portion thereof, and a crossl inking enzyme that strengthens the texture.
Therefore, the invention provides a process that combines the physical modif i
cation of fat globules and treatment with a crosslinking enzyme in order to pre
pare soured milk products and to modify and stabilize their texture. The
process is simple, economical, and industrially applicable on large scale, and it
does not cause additional costs. Further, the process of the invention provides
significant savings when the amounts of the components in the milk raw mate
rial, such as fat content and/or protein content, may be reduced without affect
ing the texture and properties of the product being prepared. The possibility of
affecting the amounts of different milk raw material components is important,
because the dairy industry currently uses component manufacturing. The in
vention also relates to a milk product that contains physically modified milk raw
material fat globules and has been treated with a crosslinking enzyme. Thus,
the invention relates to a soured milk product which is optimal in relation to the
different components of the milk raw material and withstands well downstream
processing steps of preparation, such as mass modification and texture break
ing, and whose structural properties also keep in storage.
It is very challenging to achieve a soured milk product which con
tains physically modified milk raw material fat globules, is completely flawless
in taste and texture, meets consumer expectations, and withstands both the
demanding downstream processing steps of sour milk product preparation,
such as mass modification and texture breaking, and storage, and is made in
an economical and simple manner. Adjusting the concentrations of raw mate
rial components, such as reducing fat, in a product is challenging. It was sur
prisingly found that a soured product of a desired type that is clearly thicker in
texture was obtained by physically modifying the milk raw material and treating
it with a crosslinking enzyme during souring.
With the process of the invention, it is possible to improve the struc
tural/texture properties of the product being prepared by physically modifying
the particle size, size distribution, composition and condition of the fat globules
in the milk raw material.
The object of the invention is achieved with a product and process
that are characterized by what is stated in the independent claims. Preferred
embodiments of the invention are disclosed in the dependent claims.
Brief description of the figures
Figure 1 is a flow diagram showing an embodiment of the prepara
tion process of a soured milk product according to the invention, when prepar
ing a low-fat yogurt with reduced protein content. In the process milk raw
material with standardized fat and protein content (0.4 % fat, 3.5 % protein)
was physically treated by high-pressure homogenization at a pressure of 400
bar.
Figure 2 is a flow diagram showing an embodiment of the prepara
tion process of a soured milk product according to the invention, when prepar
ing a low-fat yogurt. In the process the fat portion was physically treated by
high-pressure homogenization at a pressure of 1000 bar.
Figure 3 is a flow diagram showing an embodiment of the prepara
tion process of a soured milk product according to the invention, where fat is
physically modified by means of microfiltration.
Figure 4 shows the particle size distribution of non-homogenized
standardized yogurt milk having a fat content of 1%, measured by particle
size analyzer (Malvern).
Figure 5 shows the particle size distribution of homogenized (220
bar/40 bar), standardized yogurt milk having a fat content of 1%, measured
by particle size analyzer (Malvern).
Figure 6 shows the particle size distribution of high-pressure ho
mogenized (400 bar/70 bar), standardized yogurt milk, fat content 1%,
measured by particle size analyzer (Malvern).
Detailed description of the invention
The invention relates to a soured milk product that contains physi
cally modified milk raw material fat globules. In addition, the invention relates
to a soured milk product that contains physically modified milk raw material fat
globules, i.e. micro/nano particles of milk raw material fat, and has been pro
duced by means of a crossl inking enzyme, and to processes for the prepara
tion of such a product. With the invention, it is possible to optimize a product in
relation to the different components of the milk raw material and still maintain
the texture and stability of the structure/texture during storage.
It was surprisingly found that by physically modifying milk raw mate
rial and treating it with a crosslinking enzyme during souring, a sour milk prod
uct is obtained that is clearly thicker in texture than a corresponding product
produed of high-pressure homogenized milk raw material. Small fat globules
created as a result of the physical modification significantly increase the viscosity
of a sour milk product, such as yogurt, and the formed small fat globules
also prevent syneresis more efficiently than bigger unmodified fat globules and
their clusters. Without wishing to be bound by a theory, it can be assumed that
the small fat globules are coated with casein and whey protein and the crosslinking
enzyme, such as transglutaminase, crosslinks the small fat globules
with the matrix. The proteins inherent to the membrane structures of the fat
globules are crosslinked. Possibly due to the small fat globules, in which case
the structure has more surface and/or less void volume, the caseins and whey
proteins get close to each other. Their crosslinking is then enhanced, as the
activity of the transglutaminase becomes easier.
In addition, it was surprisingly found that the same effect can be
produced by physically modifying only the fat portion of the milk raw material
and combining it with non-homogenized fat-free milk or fat-free milk homoge
nized conventionally at low pressures, and treating the thus obtained milk with
a crosslinking enzyme.
Further, it was surprisingly found that the same effect is produced
by using, in the preparation of a soured milk product, native small fat globules
originating from milk or some other suitable fat source, such as soy milk or co
conut milk, and/or physically, with microfiltration, for instance, modified small
fat globules that are combined with non-homogenized fat-free milk or fat-free
milk homogenized conventionally at low pressures, and treating the thus o b
tained milk with a crosslinking enzyme.
Thus, according to an embodiment of the invention, the milk raw
material is physically modified and treated with a crosslinking enzyme. Accord
ing to a second embodiment of the invention, the fat portion of the milk raw
material is modified physically and combined with non-homogenized fat-free
milk or fat-free milk homogenized conventionally at low pressures, and the thus
obtained milk or milk raw material is treated with a crosslinking enzyme. Ac
cording to a third embodiment of the invention, native and/or physically mod i
fied small fat globules are combined with non-homogenized fat-free milk or fatfree
milk homogenized conventionally at low pressures, and the thus obtained
milk or milk raw material is treated with a crosslinking enzyme.
The invention also relates to a process for the modification of the
texture of soured milk products by means of physical modification of the milk
raw material and a crosslinking enzyme that strengthens the texture.
It was surprisingly found that by means of the processes according
to the invention, it is possible either to prepare a clearly thicker sour milk prod
uct or to reduce the protein content and/or fat content of the product while the
texture of the final product remains the same. This means either a significant
improvement in the quality of the product or significant savings in the raw ma
terials / ingredients. The processes can be applied to the preparation of yogurt,
drinkable yogurt, set-type yogurt, viili, and fermented milk, in particular.
The processes of the invention are thus suitable for the preparation
of soured products having excellent taste and texture. By means of the inven
tion, it is also possible to reduce the fat content of the product and/or maximize
its protein content. The product of the invention is characterized in that it withstands
the mass modification and texture breaking typical of sour milk products
during preparation, as well as the storage of the product.
In connection with the present invention, physical modification of the
milk raw material refers to a procedure that is done through high mechanical
forces / shear forces directed to the raw milk material or with separation techniques
or a combination of these, with which especially the particle size and
particle size distribution, but also composition and condition of the milk raw
material fat globules are changed.
In connection with the present invention, the term "a physically mod
ified fat globule'V'physically modified fat globules" refers to a fat globule/fat
globules having a size of less than about 1 miti preferably from about 20 nm to
about 1 miti , and more preferably from about 00 nm to about 1 miti . In addition,
the fat globule/fat globules have an average particle size, or medium size less
than about 1 miti , preferably from about 200 to about 500 nm, and more prefera
bly from about 300 to about 400 nm.
Industrial-scale mixers having a sufficient energy density to provide
high mechanical forces / shear forces and capable of producing fat globules
with a particle size of less than 10 miti include homogenizers (less than 4 miti ) ,
high-pressure homogenizers (less than 2 miti ) , micro-flu id izers (less than 1
miti ) , rotor-stator systems (Ultra Turrax; particle size of 1 to 25 miti ) , and colloid
mills (particle size of 1 to 25 miti ) . The size, size distribution, composition, and
condition of the milk raw material fat globules can also be physically modified
by extrusion, ultrasound treatment (low frequency, power ultrasound), optical
technology (Laser, Light Amplification by Stimulated Emission of Radiation),
HPP technology (high pressure processing), atomizer (spray drying), no n
thermal pulsed electric field (PEF) technology, and a combination of different
techniques. MTS (manothermosonication) technology combines treatment with
ultrasound under pressure and a temperature lower than the pasteurization
temperature. Membrane techniques, such as microfiltration and gravitation, as
well as combinations of different techniques can be used as the separation
technique.
According to an embodiment, the physical modification is done by
high-pressure homogenization at a temperature of 40 to 95°C, preferably 60 to
70°C, and a pressure of 250 to 1000 bar, preferably 250 to 500 bar. In an em
bodiment, the pressure of the high-pressure homogenization is 400 bar. In an
other embodiment of the invention, high-pressure homogenization is done in
two steps. In a second embodiment of the invention, the high-pressure ho
mogenization is done in two steps in such a manner that in the first step, the
temperature is 40 to 95°C and the pressure is 250 to 1000 bar, and in the se
cond step, the temperature is 40 to 95°C and the pressure less than 1000 bar.
In the first step, the size of fat globules is decreased, and in the second step,
any fat globules that have attached to each other are separated into individual
globules. In the second step, the homogenization conditions may correspond
to those of high-pressure homogenization i.e., having a temperature of 40 to
95°C, preferably 60 to 70°C, and a pressure of 250 to 1000 bar, preferably 250
to 500 bar or be either those used in conventional homogenization i.e., having
a temperature of 65 to 70°C and a pressure of 150 to 200 bar or even lower
than them. In one embodiment, in the first step, the pressure is 400 bar, and in
the second step, the pressure 70 bar.
As can be seen from Figure 4, in non-homogenized milk the fat
globules are within the size area from 1 mhh to 10 mhh and caseins are within
the size area from 0.04 mhh to 0.4 mhh . The traditional homogenization ( 100 -
250 bar) reduces the size of fat globules to below 2 mhh (see Figure 5). The
high pressure homogenisation (250 - 1000 bar) reduces the fat globule size
even further i.e., to below 1 mhh (see Figure 6).
In addition to the particle sizes of the fat globules, the particle volumes
of particles smaller than about 1 mhh are affected by high-pressure ho
mogenization. The particle volume share of fat globules having particle size for
example less than about 1 mhti , less than about 0.6 mhh and less than about 0.3
mhti , is higher after high-pressure homogenization than after conventional ho
mogenization. High-pressure homogenization increases the volume share of
fat globules having particle size less than about 1 mhti , less than 0.6 mhh and
less than 0.3 mhh by about 10 %, about 15 % and about 15 %, respectively,
compared to the traditional homogenization. As can be seen from Table 1, the
volume share of fat globules having particle size less than about 1 mhh increas
es from about 9 1.5 % to 99.7 % when the homogenization pressure increases
from 220 bar to 400 bar. Correspondingly, the volume share of fat globules
having particle size less than about 0.6 mhh increases from about 80.8 % to
94.8 % and the volume share of fat globules having particle size less than
about 0.3 m ΐ increases from about 65.2 % to 78.4 % when the homogeniza
tion pressure increases from 220 bar to 400 bar.
Table 1.
Particle volume share%
After the high-pressure homogenization, the fat globules could be
thought to be acting like caseins in milk based products, such as yoghurts of the
present invention, and this can be seen in thicker texture of the product and/or
in reduced protein and/or fat content of the product while the texture of the
product remains unchanged.
According to a second embodiment of the invention, physical modif i
cation is done by microfiltration. Microfiltration (MF) is a membrane filtration process,
in which the average pore size of the used membranes is 0.05 to 10 miti .
The components contained in a fluid to be separated are forced through the
membrane by means of pressure.
In microfiltration, native fat globules divided into different size
categories do not lose the original structure of their membrane, as occurs in
homogenization, for instance. Homogenization under pressure affects the fat
globules in such a manner that it breaks large fat globules into smaller ones,
whereby part of the membrane of the globules is replaced by casein proteins.
This changes the properties of the fat globules in such a manner that they are
less susceptible to the oxidative spoilage effects of fats, for example. The fat
globules that have been reduced in size by homogenization and coated in ca
sein act to some extent like casein.
According to another embodiment of the invention, the physical
modification is done by high-pressure homogenization and microfiltration in
any order. In this embodiment, the milk raw material can for instance first be
microfiltered and then the retentate obtained from microfiltration is highpressure
homogenized and combined with the microfiltration permeate for fur
ther processing.
In milk, fat is present in globules having a diameter that varies be
tween 0.1 and 15 miti . The average fat content of raw milk is 4.5%. Approximate
80% of the fat globules in milk have a diameter of less than 1 miti in size,
but the total fat content has less than 10% of small fat globules. The average
diameter of a fat globule is approximately 4 miti . It has been noticed that large
(over 2 miti ) fat globules cluster more easily than the small (less than 2 miti )
and are more susceptible to lipolysis. Large globules also bind less water.
In this patent application, the term "physical modification of milk raw
material" covers not only the above-mentioned processes, but also modif ica
tion done by means of enzymes (fat affecting enzymes, phospholipases, lipas
es and the like).
The terms "mechanically modified fat globules", "physically modified
fat globules", micro-particles", "nano-particles" and "enzymatically modified fat
globules" are used in parallel.
In addition, the terms "fat globule of milk raw material" and "microparticle/
nano-particle of milk raw material fat" are used in parallel. The term "fat
globules of milk raw material" refers to the micro- and/or nano-particles or fatty
acid chains or parts separated from the fat globules of milk raw material fat.
According to an embodiment of the invention, the size of the fat glob
ules obtained as a result of the physical modification is less than about 1 miti ,
preferably from about 20 nm to about 1 miti , and more preferably from about 100
nm to about 1 miti . According to a second embodiment of the invention, the av
erage particle size, or medium size, of the fat globules obtained as a result of
the physical modification is less than about 1 miti , preferably from about 200 to
about 500 nm, and more preferably from about 300 to about 400 nm. According
to a second embodiment of the invention, the size of the fat globules obtained as
a result of the physical modification is less than about 1 miti , preferably from
about 20 nm to about 1 miti , and more preferably from about 100 nm to about 1
miti , and the average particle size, or medium size, is less than about 1 miti ,
preferably from about 200 to about 500 nm, and more preferably from about 300
to about 400 nm.
The milk raw material may be milk, whey and combinations of milk
and whey as such or as concentrate. The milk raw material may be milk as
such obtained from an animal, such as a cow, sheep, goat, camel, mare or any
other animal that produces milk suitable for human consumption, or milk that is
pre-processed as desired. The milk raw material may be, for instance, whole
milk, cream, low-fat or fat-free milk, low-lactose or lactose-free milk, colostrum,
ultrafiltered milk, diafiltered milk, microfiltered milk, or milk reconstituted from
milk powder, organic milk or a combination of these. According to an embodi
ment of the invention the fat content of the milk raw material is 0.4 to 2%. The
milk raw material is preferably low-fat milk (fat content 0.5 to 1.5%) standard
ized with cream (30 to 50%) or semi-skimmed milk ( 1 .5 to 4%) or fat-free milk
(fat content less than 0.5%) standardized with whole milk (over 4%).
The milk raw material may be supplemented by ingredients general
ly used in producing milk products and/or whey and milk protein fractions, such
as milk protein, whey protein, casein, whey and milk protein fractions, milk salt,
a-lactalbumin, peptides, amino acids, e.g. lycine, as such or in different combi
nations and amounts depending on the product being prepared. The milk raw
material may be supplemented by vegetable fat, such as rapeseed oil, corn oil,
sunflower oil, berry oils as such or in different combinations and amounts depending
on the product being prepared. Possible other optional supple
ments/components are omega-3 fatty acids, antioxidants and/or water-soluble
or fat-soluble vitamins, cholesterol content-affecting sterols and their esters,
and satiation-increasing compounds or compositions, such as food fat compositions
having an oil-in-water emulsion structure and milk salts. In the process
of the invention, these optional components may be used as such or in differ
ent combinations and amounts depending on the product being prepared. The
whey and milk protein fractions may be produced by ultra- or nanofiltration (NF
retentate), for instance.
The present invention provides a new solution for avoiding structural
and quality defects that have shown to cause problems in the preparation of
sour milk products by using a process that is characterized by treating milk raw
material containing physically modified fat globules with a crosslinking enzyme
and souring it.
According to an embodiment of the invention, the milk raw material
is physically modified and treated with a crosslinking enzyme. According to this
embodiment, the milk raw material containing physically modified fat globules
is obtained by physically modifying the particle size, size distribution, composi
tion, and condition of the fat globules. Physical modification can be done by
utilizing high-pressure homogenization and/or microfiltration, for instance.
Thus, in an alternative within the scope of this embodiment, the milk raw mate
rial or part thereof is fractionated by microfiltration, and the permeate contain
ing small fat globules is transferred to treatment performed with a crosslinking
enzyme as such or together with a further high-pressure processed retentate.
Between the physical modification of the milk raw material and the treatment
with a crosslinking enzyme, other processing steps may be performed option
ally as desired and/or required. Further, other processing steps may also be
performed before the physical modification of the milk raw material. Similarly,
other processing steps may be performed after the treatment with a crosslinking
enzyme.
According to a second embodiment of the invention, the fat portion
of the milk raw material is modified physically and combined with nonhomogenized
fat-free milk or fat-free milk homogenized conventionally at low
pressures, and the thus obtained milk raw material mixture is treated with a
crosslinking enzyme and soured. According to this embodiment, the milk raw
material containing physically modified fat globules is obtained by physically
modifying the fat portion of the milk raw material and by combining it with nonhomogenized
or conventionally homogenized fat-free milk. Physical modif ica
tion can be done by utilizing high-pressure homogenization and/or microfiltration,
for instance. Thus, in an alternative within the scope of this embodiment,
the fat portion of the milk raw material is fractionated by microfiltration, and the
permeate containing small fat globules is transferred to treatment performed
with a crosslinking enzyme as such or together with a further high-pressure
processed retentate. Between the preparation of the milk raw material mixture
containing physically modified fat globules and the treating with a crosslinking
enzyme, other processing steps, such as heat treatment(s), may optionally be
performed as desired and/or required. Further, before the preparation of the
milk raw material containing physically modified fat globules, it is possible to
perform other processing steps known in the art, such as heat treatment,
standardization, reconstitution, protease, filtration, separation and/or freezing.
Similarly, other processing steps may be performed after the treatment with a
crosslinking enzyme.
According to a third embodiment of the invention, native and/or
physically modified small fat globules are combined with non-homogenized fatfree
milk or fat-free milk homogenized conventionally at low pressures, and the
thus obtained milk raw material mixture is treated with a crosslinking enzyme
and soured. According to this embodiment, the milk raw material containing
physically modified fat globules is obtained by combining native and/or phys i
cally modified fat globules with non-homogenized or conventionally homoge
nized fat-free milk. In an alternative within the scope of this embodiment, the
size of the native fat globules or fat globules obtained as a result of the phys i
cal modification is less than about 1 miti , preferably from about 20 nm to about 1
miti , and more preferably from about 100 nm to about 1 miti . According to an
embodiment, the average particle size, or medium size, of the fat globules o b
tained as a result of the physical modification is less than about 1 miti , preferably
from about 200 to about 500 nm, and more preferably from about 300 to about
400 nm. According to another embodiment, the size of the fat globules obtained
as a result of the physical modification is less than about 1 miti , preferably from
about 20 nm to about 1 miti , and more preferably from about 100 nm to about 1
miti , and the average particle size, or medium size, is less than about 1 miti ,
preferably from about 200 to about 500 nm, and more preferably from about 300
to about 400 nm.
Between the preparation of the milk raw material mixture containing
physically modified and/or native fat globules and the treatment with a crosslinking
enzyme, other processing steps, such as heat treatment(s), may o p
tionally be performed as desired and/or required. Further, before the
preparation of the milk raw material mixture containing native and/or physically
modified fat globules, it is possible to perform other processing steps known in
the art. Similarly, other processing steps may be performed after the treatment
with a crosslinking enzyme.
According to an embodiment of the invention, the process for the
preparation of a sour milk product comprises
- the physical modification of milk raw material,
- treating with a crosslinking enzyme, and
- souring, and
- optionally the packaging of the product.
According to a second embodiment of the invention, the process for
the preparation of a sour milk product comprises
- the physical modification of the fat portion of the milk raw material and
its combination with non-homogenized fat-free milk or fat-free milk ho
mogenized conventionally at low pressures
- treating with a crosslinking enzyme, and
- souring, and
- optionally the packaging of the product.
According to yet another embodiment of the invention, the process
for the preparation of a sour milk product comprises
- the combination of native and/or physically modified fat globules with
non-homogenized fat-free milk or fat-free milk homogenized conven
tionally at low pressures
- treating with a crosslinking enzyme,
- souring, and
- optionally the packaging of the product.
In the process of the invention, souring may be done before crosslinking
enzyme treatment, simultaneously with the crosslinking enzyme treat
ment or only after the crosslinking enzyme treatment. In the process of the
invention, the crosslinking enzyme treatment may be done simultaneously with
souring, before souring, or only after souring. Thus, according to an embodi
ment of the invention, the process comprises the following steps:
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material,
- souring,
- treating with a crosslinking enzyme,
- optionally packaging the product.
According to a second embodiment of the invention, the process
comprises the following steps:
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material,
- souring and treating with a crosslinking enzyme,
- optionally packaging the product.
Further according to yet another embodiment of the invention, the
process comprises the following steps:
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material,
- treating with a crosslinking enzyme,
- souring,
- optionally packaging the product.
Further, the sour milk products prepared by the process of the invention
can be soured either before packaging the product or immediately after
packaging. Especially viili-type products and set-type yogurts are soured in the
package. Thus, according to an embodiment of the invention, the process
comprises the following steps:
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material,
- packaging,
- souring/allowing to sour and treating with a crosslinking enzyme in the
package.
In the process of the invention, the heat-treatment may also be performed
in several steps.
If necessary, the composition of the milk raw material used in the
process may optionally be adjusted by standardizing its protein, fat, and/or lac
tose content. If desired/required, the milk raw material used in the process can
optionally be heat-treated before the physical modification and/or after it.
Thus, according to an embodiment of the invention, the process
comprises the following steps:
- adjusting the composition of the milk raw material, that is, standardizing
its protein, fat, and/or lactose content,
- heat-treating the milk raw material,
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material,
- heat-treating,
- souring,
- treating with a crosslinking enzyme,
- optionally packaging the obtained product.
In addition to souring, the process may also contain the use of ren
net, and if necessary a subsequent heat treatment, that is, post-pasteurization.
Thus, according to an embodiment of the invention, the process
comprises the following steps:
- standardizing, optionally, the composition of the milk raw material in
terms of protein, fat, and/or lactose content,
- optionally heat-treating the milk raw material,
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material,
- optionally heat-treating,
- souring,
- treating with a crosslinking enzyme,
- adding rennet or other enzymes,
- heat-treating,
- optionally packaging the obtained product.
Further, the process may also comprise the step of adding other raw
materials after souring and treating with a crosslinking enzyme.
Thus, according to an embodiment of the invention, the process
comprises the following steps:
- standardizing, optionally, the composition of the milk raw material in
terms of protein, fat, and/or lactose content,
- optionally heat-treating the milk raw material,
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material,
- optionally heat-treating,
- souring,
- treating with a crosslinking enzyme,
- optionally adding rennet,
- adding other raw materials,
- optionally heat-treating,
- optionally packaging the obtained product.
According to an embodiment of the invention, milk raw material
standardized in terms of protein, fat, and/or carbohydrate contents is optionally
heat-treated, the particle size, size distribution, composition and condition of its
fat globules are physically modified, and it is modified with a crosslinking e n
zyme simultaneously with souring. According to a second embodiment of the
invention, the formulation of the milk raw material is adjusted by standardizing
its protein, fat and carbohydrate contents, the standardized milk raw material is
heat-treated, the particle size, size distribution, composition and condition of
the fat globules are modified by high-pressure homogenization at a tempera
ture of 40 to 95°C and a pressure of 250 to 1000 bar, and modified with a
crosslinking enzyme simultaneously with chemical souring.
In the process of the invention, the physical modification of the milk
raw material can be done on the milk raw material or a part thereof in several
steps with the same process or by combining different techniques in order to
change the particle size, size distribution, composition and condition of the fat
globules. The physical modification of the milk raw material or a part thereof
can, thus, be done by high-pressure homogenization or microfiltration or by
both. Thus, according to an embodiment of the invention, the process com
prises the following steps:
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material or a part
thereof by using several techniques and/or several steps,
- optionally heat-treating,
- souring,
- treating with a crosslinking enzyme,
- optionally packaging the obtained product.
In one embodiment of the invention, the optional steps of the above
described processes, such as standardizing the composition of the raw milk
material, heat-treating, adding rennet or other enzymes and/or packing the
product, are performed, i.e., they are not optional.
According to an embodiment of the invention, the milk raw material,
which may be a standardized in terms of its protein, fat, and/or lactose content,
is high-pressure homogenized, treated with a crosslinking enzyme, heattreated
and cooled, a separately high-pressure homogenized and/or microfiltrated
milk raw material high in fat content (30 to 50%, preferably 35%) is
optionally added to it, a starter is added, the mixture is mixed and packaged.
In the process of the invention, the souring may be performed by
adding a biological starter specific to each product (e.g. bulk starter or direct to
vat starter DVI/DVS), a chemical starter, or organic or inorganic acids with or
without adding rennet. For instance, the Lactobacillus bulgaricus and Strepto
coccus thermophiles strains are conventionally used in yogurt production. Examples
of suitable organic acids include glucono-delta-lactone (GDL), calcium
lactate, citric acid, and lactic acid. The used acid is preferably glucono-deltalactone.
In addition to lactic acid bacteria starters, viili-mould is also used in
producing viili-type products.
The sour milk products prepared by the process of the invention can
be soured either in a tank before packaging the product or immediately after
packaging in a consumer or food service package.
Especially viili-type products and set-type yogurts are soured in the
package.
The thickness of the texture is adjusted by altering the dosage of
crosslinking enzymes. The product may be a "set type" (shearing and
spoonable), drinkable (fresh), drinkable UHT, spoonable "yogurt-type" or pow
der (spray- or freeze-dried powder) product. Nutritionally, for instance, the es
sential amino acids in the proteins are in a well-absorbing form in the product.
Amino acids of animal and vegetable proteins may be crosslinked
with enzymes, such as transglutaminase (EC 2.3.2.13). The covalent links
formed in the enzyme process resist well different process conditions, such as
heating and mixing. Of milk proteins, caseins and k-casein in particular are the
best substrate for transglutaminase b-casein, too, is rich in glutamine and ly
sine that the enzyme links together. The used transglutaminase may be any
transglutaminase enzyme used in the dairy industry, and it may originate from
a microbe, yeast, mould, fish or mammal. The transglutaminase enzyme of an
embodiment of the invention is microbial. There are several different commer
cially available transglutaminase enzyme preparations that are suitable for use
in the process of the invention. These include Activa®YG (Ajinomoto, Japan)
and Activa®MP (Ajinomoto, Japan). Optimum conditions depend on the used
enzyme, and they can be obtained from the manufacturers of the commercial
enzymes.
Other possible crosslinking and protein-modifying enzymes include
laccase, tyrosinase, peroxidase, sulphydryl oxidase, glucose oxidase, protein
glutaminase and in general other protein-modifying enzymes, such as chymosin
and proteases. Tyrosinases (EC1 .14.1 8.1 ) may originate from different
vegetable, animal or fungal species, such as the Trichoderma reesei fungus. It
is known that laccases (EC 1.1 0.3.2) originating from fungi or bacteria, such as
the Trametes hirsuta fungus, hetero-crosslink carbohydrates and proteins. Tyrosinase
and laccase preparations are also commercially available. Optimum
conditions depend on the used enzyme, and they can be obtained from the
manufacturers of the commercial enzymes. Said enzymes may be used either
alone or in combination to achieve the desired result.
The process of the invention may also contain one or more further
processing steps (e.g. mixing, separation, flavouring, cooling, packaging
and/or product recovery specific to the product being prepared or dependent
thereon), in which the soured milk raw material containing physically modified
fat globules and treated with a crosslinking enzyme is processed.
In the process of the invention, the heat treatment(s) is/are performed
in the manner known in the art. Examples of heat treatment processes
useful for the process of the invention are pasteurization, high pasteurization,
heating at a temperature lower than the pasteurization temperature for a suff i
ciently long time, thermisation, i.e., heating for at least 15 s at approximately
57 to 68°C, UHT, HT, and ESL treatments. In UHT, the raw material is heated
at approximately 135 to 140°C for 2 to 4 s . HT ("short UHT treatment") is d e
scribed in published patent application WO 201 0085957. In ESL, the raw ma
terial is heated at approximately 127 to 135°C for 1 to 2 s . In pasteurization,
the raw material is heated at approximately 70 to 72°C at least for 15 s, and in
high pasteurization, the raw material is heated at approximately 95°C at least
for 5 min. Heat treatment may also be a combination of different techniques.
According to the invention, raw milk (unseparated and unpasteur
ized milk, raw milk), which had been high-pressure-treated at a pressure of
400 bar and transglutaminase-treated during souring, was, depending on the
storage time, 65 to 35% thicker than yogurt which had been merely highpressure-
treated at a pressure of 400 bar. Milks containing 0.4% and 1.0% fat
and prepared in a corresponding manner, which were high-pressure-treated at
a pressure of 400 bar and transglutaminase-treated during souring, were twice
as thick as a control product that was merely high -pressure-treated.
Further, the viscosity of a yogurt prepared according to the invention
and high-pressure-treated at a pressure of 400 bar and transglutaminasetreated
during souring, was at one week 30% thicker than that of a yogurt ho
mogenized at a pressure of 200 bar and transglutaminase-treated during sour
ing, and 60% thicker than that of a yogurt homogenized at a pressure of 200
bar but not transglutaminase-treated.
According to the invention, the same effect can be produced by
high-pressure homogenizing only the fat portion and combining it with nonhomogenized
fat-free milk or fat-free milk homogenized conventionally at low
pressures, and treating the thus obtained milk with transglutaminase.
The texture of the products prepared with the process of the present
invention remained homogeneous and whey did not separate during cold storage
(+4°C, 3 weeks) or storage at room temperature (20 to 25°C, several
weeks). An example of an advantageous embodiment of the process of the
invention is the preparation of a yogurt having a protein content of 3.4 to 3.5.
The viscosity of the fat (4.1 %) yogurt of the invention was at one week 30%
thicker and at three weeks 65% thicker than that of the control yogurt. The viscosity
of the low-fat ( 1%) yogurt of the invention was 100% thicker than that of
the control yogurt during the entire 3-week storage time. The viscosity of an
even lower-fat (0.4%) yogurt of the invention was at one day 85%, at 1 to 2
weeks 50% and at 3 weeks 30% thicker than that of the control yogurt.
In addition, it was surprisingly found that the same effect can be
produced by high-pressure homogenizing only the fat portion and combining it
with non-homogenized fat-free milk or fat-free milk homogenized conventional
ly at low pressures, and treating the thus obtained milk with transglutaminase.
An example of an advantageous embodiment of the invention is a yogurt that
was prepared using the described process and raw materials: the fat portion
(fat 35% and protein 2%) was high-pressure homogenized at a pressure of
1000 bar and at a temperature of 60°C, whipping cream/double cream and
non-homogenized fat-free milk were combined to obtain a fat content of 1.5%
and protein content of 3.5 for the raw material, it was pasteurized and cooled
to 42°C, and TG enzyme 0.6 U/g (protein) and starter was added. The mixture
was allowed to acidify until its pH was 4.5, it was then mixed, cooled to 20°C
and packaged.
The method of the invention is simple and suitable for large-scale
production.
According to an embodiment of the invention, the process is a com
ponent manufacture process, in which milk components having different fat
and protein contents are combined only just before packaging.
The process of the present invention may be applied to both batch
and continuous production. The method of the invention is preferably carried
out as a batch process.
The invention also relates to a soured milk product that contains
physically modified milk raw material fat globules, i.e. micro/nano particles of
the milk raw material fat and has been produced by means of a crosslinking
enzyme. According to an embodiment of the invention, the size of the fat glo b
ules of the soured milk-based product is less than 1 miti , preferably from about
20 nm to about 1 miti , more preferably from about 100 nm to 1 miti . Further,
according to a second embodiment of the invention, the average particle size
or medium size of the fat globules in the soured milk-based product is less
than about 1 miti , preferably from about 200 nm to about 500 nm, and more
preferably from about 300 nm to about 400 nm. According to a second embod
iment of the invention, the size of the fat globules in the soured milk-based
product is less than 1 miti , preferably from about 20 nm to about 1 miti , more
preferably from about 100 nm to 1 miti , and the medium size is less than about
1 miti , preferably from about 200 nm to about 500 nm, and more preferably
from about 300 nm to about 400 nm.
The following examples describe the performance of the invention, but
without limiting the invention to said product embodiments.
Example 1
Yogurt produced of raw milk (400 bar and TG treatment)
The test yogurt of the invention was produced of raw milk (fat 4.1 %
and protein 3.4%) that was high-pressure homogenized at a temperature of 60°C
and a pressure of 400 bar. After this, the milk was pasteurized and cooled to a
temperature of 42°C. A TG enzyme (Activa®MP) 0.6 U/g (protein) and starter
were added. The mixture was allowed to acidify until its pH was 4.5. The mix
ture was mixed and cooled to 20°C and packaged. After this, the mixtures
were transferred to a cold room for cooling to a temperature of 5°C.
The control yogurt was prepared in the same manner except that no
TG enzyme was added with the starter.
The viscosity of the yogurt of the invention was at one week 30%
thicker and at three weeks 65% thicker than that of the control yogurt.
Example 2
Yogurt produced of milk containing 1.0% fat (400 bar and TG treatment)
The test yogurt of the invention was produced of milk (fat 1.0% and
protein 3.5%) that was high-pressure homogenized at a temperature of 60°C
and a pressure of 400 bar. After this, the milk was pasteurized and cooled to a
temperature of 42°C. A TG enzyme (Activa®MP) 0.6 U/g (protein) and starter
were added. The mixture was allowed to sour until its pH was 4.5. The mixture
was mixed and cooled to 20°C and packaged. After this, the mixtures were
transferred to a cold room for cooling to a temperature of 5°C.
The control yogurt was prepared in the same manner except that no
TG enzyme was added with the starter.
The viscosity of the yogurt of the invention was 100% thicker than
that of the control yogurt during the entire 3-week storage time.
Example 3
Yogurt produced of milk containing 0.4% fat (400 bar and TG treatment)
The test yogurt of the invention was produced of milk (fat 0.4% and
protein 3.5%) that was high-pressure homogenized at a temperature of 60°C
and a pressure of 400 bar. After this, the milk was pasteurized and cooled to a
temperature of 42°C. A TG enzyme (Activa®MP) 0.6 U/g (protein) and starter
were added. The mixture was allowed to acidify until its pH was 4.5. The mixture
was mixed and cooled to 20°C and packaged. After this, the mixtures
were transferred to a cold room for cooling to a temperature of 5°C.
The control yogurt was prepared in the same manner except that no
TG enzyme was added with the starter.
The viscosity of the yogurt of the invention was at one day 85%, at 1
to 2 weeks 50% and at 3 weeks 30% thicker than that of the control yogurt.
Example 4
The difference between the yogurt of the invention produced of milk con¬
taining 0.4% fat (400 bar and TG treatment) and control yogurt 1 (200 bar)
and control yogurt 2 (200 bar + TG treatment)
The test yogurt of the invention was produced of milk (fat 0.4% and
protein 3.5%) that was high-pressure homogenized at a temperature of 60°C
and a pressure of 400 bar. After this, the milk was pasteurized and cooled to a
temperature of 42°C. A TG enzyme (Activa®MP) 0.6 U/g (protein) and starter
were added. The mixture was allowed to sour until its pH was 4.5. The mixture
was mixed and cooled to 20°C and packaged. After this, the mixtures were
transferred to a cold room for cooling to a temperature of 5°C.
Control yogurt 1 was prepared in the same manner as the test yo
gurt of the invention except that no TG enzyme was added with the starter and
the milk was homogenized at a pressure of 200 bar.
Control yogurt 2 was prepared in the same manner as the test yo
gurt of the invention except that the milk was homogenized at a pressure of
200 bar.
The viscosity of the yogurt of the invention was at one week 60%
thicker than that of control yogurt , and control yogurt 2 was at one week 30%
thicker than control yogurt .
Example 5
Separate homogenization of the fat portion (1000 bar) and yogurt pro¬
duced of milk containing 1.5% fat (TG treatment)
The fat portion of the test yogurt of the invention (fat 35% and protein
2%) was high-pressure homogenized at a pressure of 1000 bar and a
temperature of 60°C. After this, double cream and non-homogenized fat-free
milk were combined to produce a fat content of 1.5% and protein content of
3.5% for the raw material. After this, the milk was pasteurized and cooled to a
temperature of 42°C. A TG enzyme (Activa®MP) 0.6 U/g (protein) and starter
were added. The mixture was allowed to acidify until its pH was 4.5. The mix
ture was mixed and cooled to 20°C and packaged. After this, the mixtures
were transferred to a cold room for cooling to a temperature of 5°C.
The control yogurt was prepared in the same manner as the test
yogurt of the invention except that no TG enzyme was added with the starter.
The viscosity of the yogurt of the invention was at one day and at
three weeks 50% thicker than that of the control yogurt.
Example 6
Microfiltration of cream
Cream was filtered with Tetra Alcross MFS-1 microfiltration equip
ment with a ceramic, tube-type filtration membrane. The targeted top end
pressure of the feed was approximately 4 bar. The pressure difference be
tween the permeate and retentate side was approximately 0.4 bar.
Table 2 shows the total surface areas and average particle diameters
of the unfiltered raw cream and microfiltered permeate and retentate ca l
culated with the Malvern program.
Table 2. Total surface areas and average particle diameters calculated
with the Malvern program.
Example 7
Yogurt produced using microfiltration permeate
Three yogurts were prepared, in which the fat content was adjusted to
2.5% and in which
a) non-homogenized fat-free milk was standardized with nonhomogenized
cream and the thus obtained milk raw material mixture (fat con
tent 2.5%) was homogenized at a pressure of 140/20 bar (control),
b) the milk raw material (fat content 2.5%) was obtained by adding to
non-homogenized fat-free milk non-homogenized cream permeate that was
obtained from raw cream by microfiltration, and
c) the milk raw material (fat content 2.5%) was obtained by adding to
non-homogenized fat-free milk non-homogenized cream permeate (control).
It was found that in the non-homogenized standardized raw material
milk (c), fat rose to the top, whereas in the homogenized (a) or cream permeate-
containing (b) milk raw material, no phase separation occurred. The milk
raw materials were pasteurized at a temperature of 90°C for 5 min and soured
with a yogurt starter at 42°C/pH 4.5. The gelated yogurt was mixed. The yogurt
with a conventionally homogenized fat (average particle size around 0.5 miti )
was the thickest (200 to 400 mPas). The texture of this yogurt thickened further
during storage. The yogurt without homogenization (average particle size of fat
around 4 miti ) was around 100 mPas in thickness when fresh and 200 mPas
after three weeks of storage. With the cream permeate (average particle size
of fat 1.8 miti ) , the thicknesses of the yogurt were 100 and 125 mPas. The yogurt
with the cream permeate was the most stable in texture, its viscosity did
not change during storage. Whey did not separate from any sample.
Claims
1. A process for the manufacture of a sour milk product, character
ised in that milk raw material containing physically modified fat globules is
treated with a crosslinking enzyme and then soured.
2 . A process as claimed in claim 1, characterised in that the milk
raw material containing physically modified fat globules is obtained by physi
cally modifying the particle size and size distribution of the fat globules of the
milk raw material.
3 . A process as claimed in claim 1, characterised in that the milk
raw material containing physically modified fat globules is obtained by physi
cally modifying the fat portion of the milk raw material and by combining it with
non-homogenized or conventionally homogenized fat-free milk.
4 . A process as claimed in claim 1, characterised in that the milk
raw material containing physically modified fat globules is obtained by combining
native and/or physically modified fat globules with non-homogenized or
conventionally homogenized fat-free milk.
5 . A process as claimed in any one of claims 1 to 4, characterised in
that the treatment with a crosslinking enzyme is done before souring, simulta
neously with souring, or after souring.
6 . A process as claimed in claim , characterised in that the process
comprises the following steps:
- physically modifying the particle size, size distribution, composi
tion, and condition of the fat globules of the milk raw material,
- souring,
- treating with a crosslinking enzyme,
- optionally packaging the obtained product.
7 . A process as claimed in claim , characterised in that the process
comprises the following steps:
- physically modifying the particle size, size distribution, composition,
and condition of the fat globules of the milk raw material,
- packaging,
- souring and treating with a crosslinking enzyme in the package.
8 . A process as claimed in claim 6, characterised in that the process
comprises the following steps:
- optionally adjusting the composition of the milk raw material,
- optionally heat-treating the milk raw material,
- physically modifying the particle size, size distribution, composi
tion, and condition of the fat globules of the milk raw material,
- optionally heat-treating,
- souring,
- treating with a crosslinking enzyme,
- optionally adding rennet,
- optionally heat-treating,
- optionally adding other raw materials,
- optionally packaging the obtained product.
9 . A process as claimed in any one of claims 1 to 8, c h a r a c t e r -
i s e d in that the milk raw material containing physically modified fat globules
is achieved and/or the physical modification is done by high-pressure homogenization
and/or microfiltration.
0 . A process as claimed in any one of claims 1 to 9, c h a r a c -
t e r i s e d in that the souring is done biologically by adding a starter, product
inoculation starter, chemical starter, organic acids or inorganic acids with or
without adding rennet.
11. A process as claimed in any one of the preceding claims,
c h a r a c t e r i s e d in that the process is a component manufacture process,
in which milk components having different fat and protein contents are com
bined only just before packaging.
12 . A process as claimed in any one of the preceding claims,
c h a r a c t e r i s e d in that the preparation process is either a continuous or
batch process.
13 . A process as claimed in any one of the preceding claims,
c h a r a c t e r i s e d in that souring is performed either in a tank before the
product is packaged or immediately after packaging in a consumer or food se r
vice package.
14 . A soured milk-based product, c h a r a c t e r i s e d in that it is
prepared by a process of any one of claims 1 to 13 .
15 . A soured milk-based product, c h a r a c t e r i s e d in that the
size of the fat globules in the product is from about 20 nm to about 1 miti .
16 . A product as claimed in claim 15 c h a r a c t e r i s e d in that
the medium size of the fat globules is less than about 1 miti , preferably from
about 200 nm to about 500 nm.