Automated process for the preparation of an edible fat-containing product and apparatus for carrying out such a process

Apparatus for chilling and working fat-containing compositions, comprising: PA1 (a) means for chilling a composition passed therethrough, PA1 (b) a crystallizer-unit, comprising a rotor, suitable for working the fat-containing composition, placed downstream of said chilling means, PA1 (c) means for measuring the rotation speed of the rotor of the crystallizer-unit, and/or means for measuring the residence time of the fat-containing composition in the crystallizer-unit, which means are able to generate a signal responsive to the rotation speed of or residence time in the crystallizer-unit, PA1 (d) computing means which, on the basis of the signals generated by means (c), are able to calculate target values for the residence time and/or rotation speed, and PA1 (e) controlling means which may adjust the residence time and/or rotation speed of the crystallizer-unit in accordance with the target values calculated by (d) for the residence time and/or rotation speed.

The present invention relates to a process for the preparation of an edible 
fat-containing product, comprising chilling at least part of the fat phase 
of said product, and subsequently feeding the chilled fat through a 
crystallizer-unit, the chilled fat on entering the crystallizer-unit 
having a solid fat content of at least 0.5 wt. %. 
The above process is well known in the art and commonly used in the 
manufacture of fat products such as margarine, halvarine, shortenings, 
etc. The final characteristics of such fat-containing products heavily 
depend on the processing conditions applied in the manufacture of such 
products. Examples of processing conditions which influence the product's 
final characteristics are the residence times within the various 
processing-units (e.g. A-, B- and C-units), the amount of working in the 
units and the amount of chilling applied. 
The large influence of the processing-conditions on the properties of the 
final product may partly be explained from the crystallization-behaviour 
of the fat-phase as present in such a product. Due to the phenomenon 
called polymorphism, triglycerides as present in oils and fats can 
crystallize in stable and unstable forms, depending on their 
crystallization structure. The instable, or metastable, forms are obtained 
by rapid chilling to a temperature below the melting point. The most 
instable form is called the alpha-form. The most stable form is the 
beta-form and in between the former two forms is the beta'-form. Besides 
these main forms various other crystallization forms exist, which however 
do not need to be discussed here. 
In the manufacture of many fat-containing products a fluid oil-containing 
composition is quickly and deeply chilled, resulting in the 
crystallization of part of the fat to a metastable crystal modification, 
whereafter transformation to, for example, the beta'-form takes place in 
crystallizers (C-units), resting tubes (B-units), and during storage of 
the product. The transition of the metastable crystals to more stable 
crystals is accompanied with an increase in the solids content of the 
chilled fat. 
As it is important to control the solids content of the fat during 
processing, it is thus important to control the extent to which conversion 
of the metastable to a more stable form takes place. Commonly this problem 
is solved by applying long residence times (i.e. large and/or many B-and 
C-units) to make sure that the metastable form is almost completely 
converted to a more stable form (mostly the beta'-form), so that the 
maximum solids content at said temperature is nearly reached. This 
approach, however, does not allow the partial conversion of the metastable 
form to a more stable form, which partial conversion may be beneficial for 
some types of products. Moreover this approach leads to an 
over-dimensioning of processing-units. 
It has been found now that, given a certain fat blend, there exists a 
relationship between on the one hand the degree of crystallization in the 
crystallizer-unit and on the other hand the residence time in the 
crystallizer-unit and the intensity of working in the crystallizer-unit. 
Thus by adjusting the processing conditions, i.e. the residence time 
and/or working intensity in the crystallizer-unit, which influence the 
conversion of fat crystals from the metastable to a more stable form, it 
is possible to control the degree of conversion, and thereby the degree of 
crystallization, at a certain stage of the process. 
The present invention therefore relates to a process for the preparation of 
an edible fat-containing product, comprising: 
a) chilling at least part of the fat phase of said product, and 
subsequently 
b) feeding the chilled fat through a crystallizer-unit, the chilled fat on 
entering the crystallizer-unit having a solid fat content of at least 0.5 
wt. %, more preferably of at least 1 wt. %, and 
c) controlling the degree of crystallization in the crystallizer-unit by 
adjusting the residence time and/or the intensity of working in said 
crystallizer-unit according to an experimentally derivable relationship 
between on the one hand the degree of crystallization in the 
crystallizer-unit and on the other hand the residence time in the 
crystallizer-unit and/or the intensity of working in the 
crystallizer-unit. 
It is to be understood that whenever used here, the term "control" does not 
encompass manual control by humans. Instead when used here, the term 
control relates to automatic control which, when operative, does not 
require any human act. 
Here the crystallizer-unit may be any kind of apparatus which allows the 
conversion of fat crystals from their metastable to a more stable form. 
Preferably the crystallizer-unit is constructed in such a manner that a 
(super)chilled- fat-containing composition, when passed through said 
crystallizer-unit, is subjected to shear, inducing conversion of 
metastable fat crystals to a more stable form. Moreover, the 
crystallizer-unit, as applied in the present process, preferably, is 
essentially non-cooled.

In the present process the residence time and/or the intensity of working 
are adjusted to maintain the degree of crystallization at a fairly 
constant level. By increasing the residence time additional fat crystals 
will be formed, whereas a decrease in residence time results in the 
opposite effect; i.e. less fat crystals being formed. Moreover it was also 
found that by increasing the intensity of working to which the chilled fat 
phase is subjected, the amount of fat crystals formed may be increased. 
Thus it is possible to control the amount of fat crystals formed in the 
crystallizer-unit by means of the residence time and/or working intensity. 
In traditional processing of fat-containing products the working 
intensity, e.g. the rotation speed, is maintained at a constant level. 
If in the process according to the invention the residence time is kept 
constant, the degree of crystallization may be controlled by adjusting the 
intensity of working in the crystallizer in accordance with an 
experimentally determined relationship between the degree of 
crystallization and the intensity of working, for that particular 
residence time. If, alternatively, the intensity of working is kept 
constant, the degree of crystallization may be controlled by adjusting the 
residence time according to the relationship between the degree of 
crystallization and the residence time, at that particular intensity of 
working. 
In either of the above approaches the degree of crystallization may be 
maintained at a constant level by monitoring the solid fat increase 
obtained in the crystallizer and adjusting the residence time or rotation 
speed so as to compensate fluctuations in the degree of crystallization 
observed in said crystallizer. Also the present process makes it possible 
to compensate fluctuations in residence time by adjusting the rotation 
speed and vice versa of fluctuations in the rotation speed by adjusting 
the residence time in the crystallizer, so as to maintain an essentially 
constant degree of crystallization in the crystallizer. The solid fat 
content of a fat-containing composition may be determined by, for 
instance, by measuring the in-line density of the fat-containing 
composition, which is correlated with the solid fat content of said 
composition or, alternatively, by means of on-line pulse-NMR. 
In the present process fluctuations in the degree of crystallization 
obtained in the crystallizer can be compensated by either adjusting the 
rotation speed or the residence time. Alternatively, however, it is also 
possible to compensate for fluctuations in the degree of crystallization 
by adjusting both the rotation speed and the residence time. The latter 
approach may be advisable in a situation where, for instance, the rotation 
speed would have to be set at an undesirable high or low speed. 
It is surprising that for a given fat blend, containing a certain amount of 
crystallized fat when entering the crystallizer-unit, the degree of 
crystallization in the crystallizer-unit may be controlled effectively by 
means of not more than two parameters, as unexpectedly, for instance, the 
temperature of the fat after the (super) chilling step, as well as the 
physical properties of the fat blend, other than the crystallization-rate 
which will be discussed below, appear to be of only minor influence on the 
degree of crystallization observed. 
If in the present process the chilled fat is not in a super-chilled state, 
no additional crystallization can be induced by adjusting the residence 
time and/or the working-intensity in the crystallizer-unit. Thus the fat 
subjected to the chilling step, on entering the crystallizer-unit, should 
be in a super-chilled state. Here by fat in a super-chilled state is meant 
that the solid fat content of the fat, at the temperature of said fat, is 
lower than the solid fat content of said fat, at the same temperature, 
when crystallized to equilibrium, i.e. when crystallized in its most 
stable form. 
It was found that, in general, the degree of crystallization in the 
crystallizer-unit not solely depends on the residence time and the 
intensity of working in the crystallizer-unit, but also on the 
crystallization-rate of the fat. Therefore in a preferred embodiment of 
the present invention the degree of crystallization of fat in the 
crystallizer-unit is controlled by adjusting the residence time and/or the 
intensity of working in said crystallizer-unit according to an 
experimentally derivable relationship between on the one hand the degree 
of crystallization in the crystallizer-unit and on the other hand the 
crystallization-rate of the fat, the residence time in the 
crystallizer-unit and/or the intensity of working in the 
crystallizer-unit. Thus, in this preferred embodiment, the present process 
will also deal with variations in the crystallization rate of the fat 
blend in use, and as a function of said crystallization rate adjust the 
working intensity and/or residence time to the appropriate level(s). 
By crystallization-rate as used here, is meant a parameter which indicates 
how fast a fat crystallizes under certain conditions. Such a parameter 
distinguishes for example slow-crystallizing fats from fast-crystallizing 
fats. An example of a parameter that may be used as an indication of the 
crystallization-rate is the so called transition time. The transition time 
for a certain fat blend may be determined from the adiabatic 
crystallization curve, which for most commercially used fat blends is of a 
sigmoid form. The adiabatic crystallization curve is obtained by rapidly 
chilling a fat blend, followed by measuring, under adiabatic conditions, 
the temperature of the blend as a function of the time. The time at which 
the sharpest increase in temperature is observed is called the transition 
time. In FIG. 1 the adiabatic crystallization curve for a certain fat 
blend is represented. In said figure the transition time for that 
particular fat blend has been indicated. Of course the transition time 
measured depends on the chilling step applied. Therefore to allow a good 
comparison between different fat blends, it is recommendable to apply a 
standard chilling step to determine the transition time for the various 
blends. 
The relationship between on the one hand the degree of crystallization in 
the crystallizer-unit and on the other hand the crystallization rate of 
the fat blend, the residence time and working conditions in the 
crystallizer-unit, depends on the kind of production line used and may be 
derived experimentally. When determining such an experimental 
relationship, the degree of crystallization of a fat-containing 
composition in a crystallizer-unit can, for instance, suitably be defined 
as the quotient of the increase in solid fat-content observed in the 
crystallizer-unit, and the increase in solid fat-content observed when a 
fat-sample is taken immediately before the crystallizer and allowed to 
crystallize to equilibrium under adiabatic conditions. Thus defined, the 
degree of crystallization can range from 0.0 to 1.0. 
Whenever referred to in this application the solids content of a fat is 
determined by means of NMR using the method described in "Fette, Seifen, 
Anstrichmittel", 80 (1978), 180-186. 
The intensity of working, in case such working is accomplished by means of 
rotating elements, may, for example, suitably be defined as the rotation 
speed, as the intensity of working appears to be proportional to the 
rotation speed. In case the crystallizer-unit comprises no rotating or 
other moving elements, the intensity of working in general is found to be 
proportional to the linear velocity of the composition passing through the 
device. An example of a crystallizer-unit comprising no rotating or moving 
elements is a so called static mixer. 
The residence time can properly be defined as the quotient of the volume of 
the crystallizer-unit and the volume-throughput. Thus, for example, if the 
volume of the crystallizer-unit is kept constant the (reciprocal) 
volume-throughput may be used as a measure for the residence time and vice 
versa. 
It was found that the relationship between on the one hand the degree of 
crystallization observed in the fat after leaving the crystallizer-unit, 
and on the other hand the residence time and the intensity of working in 
the crystallizer unit, and the crystallization-rate of the fat phase 
subjected to the chilling step, in general, can be represented by a single 
formula. Thus in a preferred embodiment the present invention relates to a 
process wherein the residence time and/or the intensity of working in the 
crystallizer-unit are adjusted according to a relationship which can be 
represented by the following formula: 
EQU E&lt;&gt;(t.sub.c).sup.x .multidot.(v.sub.c).sup.y .multidot.(d).sup.z 
where 
E represents the degree of crystallization, 
t.sub.c is the residence time in the crystallizer-unit, 
v.sub.c represents the intensity of working in the crystallizer-unit, 
d represents the crystallization-rate of the fat subjected to the chilling 
step, 
x is within the range of from 0.5 to 2.0, 
y is within the range of from 0.1 to 1.0, more preferably within the range 
of from 0.3 to 0.8, 
z is within the range of from -2.0 to -0.5, and where &lt;&gt; stands for: is 
proportional to. 
A still better control of the degree of crystallization may be obtained if 
the exponents x, y, and z are within the following ranges: x between 0.7 
and 1.4, y between 0.35 and 0.7, and z between -1.5 and -0.7. 
The above relationship, as may be seen from FIG. 2 wherein the degree of 
crystallization of various margarine as a function of 
(T.sub.c).multidot.(v.sub.c)1/2/d is represented, is particularly accurate 
as long as the degree of crystallization remains substantially below 100%. 
Thus in the present process the degree of crystallization obtained in the 
crystallizer-unit, defined as the quotient of the increase in solid 
fat-content in the crystallizer-unit, and the increase in solid 
fat-content found when a fat-sample is taken immediately before the 
crystallizer and allowed to crystallize to equilibrium under adiabatic 
conditions, preferably is less than 0.85, more preferably less than 0.7. 
Since in general it is difficult to influence the residence time in the 
crystallizer-unit, because, in normal practice, the throughput is not 
allowed to fluctuate and because crystallizer-units normally have a fixed 
volume, it is preferred to use the intensity of working in said unit, to 
adjust the processing conditions. 
In a preferred embodiment of the present invention the crystallizer-unit 
comprises a rotor. The rotation speed of the rotor may be taken as a 
suitable measure of the intensity of working in such a crystallizer-unit. 
Preferably a crystallizer of the C-unit type is used as a crystallizer-unit 
according to the present process. In order to adjust the intensity of 
working in such a C-unit, the rotation-speed of the rotor, on which pins, 
or the like, are mounted, may be varied. 
The chilling step in the present process may take place in any kind of 
chilling-apparatus, although it is preferred to use the devices which are 
normally used in the manufacture of fat-containing products, i.e. A-units 
(also called Votators {tradename}), chilled cavity transfer mixers, 
cooling coils, etc. Moreover these chilling devices preferably are used in 
such a manner that, when passed therethrough, the fat is not only chilled, 
but also subjected to shear, as shear promotes the formation of metastable 
fat-crystals. 
In this application the words fat and oil are used interchangeably. By fat 
and oil is meant a triglyceride composition, but also non-toxic material 
having physical properties similar to those of triglycerides, which 
material may be indigestible, such as for example jojoba oil, or esters of 
fatty acids and sugars. 
Although the present process may be applied in the preparation of all kinds 
of fat-containing products, it is preferred to use the process in the 
production of products mainly consisting of fat and/or water, such as 
bakery margarine, spreads, shortenings etc. Preferably the process is used 
in the manufacture of fat-containing products comprising a continuous 
fat-phase, and containing more than 80 wt. % of water and fat. More 
preferably the process is applied in the production of fat-containing 
products having a fat-content of at least 35 wt. %, more preferably of at 
least 65 wt. %. 
The crystallization-rate of the chilled fat phase may be determined 
off-line, for example, by taking samples from the oil-container from which 
the oil is fed to the production line, but it is also possible to 
determine said crystallization-rate in-line, for instance, after the 
chilling step. 
If the crystallization rate is determined off-line, this means that, in the 
conventional semi-continuous process, each fat blend batch is analyzed 
separately. For each batch, on the basis of the crystallization rate 
found, the process conditions, i.e. working intensity and/or residence 
time are then adjusted in accordance with the experimentally derived 
relationship. 
In another embodiment of the present invention, the crystallization-rate is 
determined in-line. By measuring the temperature of the chilled 
fat-containing material upon entering and leaving the crystallizer-unit, 
the temperature increase of said material inside the crystallizer-unit can 
be established. The latter temperature increase, provided rotation speed 
and throughput remain constant, is a good measure of the rate of 
crystallization of the fat blend used. The use of the temperature increase 
as a measure of the rate of crystallization is particularly effective if 
the degree of crystallization observed in the crystallizer-unit is 
substantially lower than the maximum obtainable degree of crystallization. 
Thus the processing conditions after the chilling step may be adjusted 
adequately in a fully automatic manner, taking into account the 
crystallization rate of the specific fat blend being fed to the cooling 
section of the production line at that moment 
Another aspect of the present invention is concerned with an apparatus for 
chilling and working fat-containing compositions, comprising: 
(a) means for chilling a composition passed therethrough, 
(b) a crystallizer-unit, comprising a rotor, suitable for working the 
fat-containing composition, placed downstream of said chilling means, 
(c) means for measuring the rotation speed of the rotor of the 
crystallizer-unit, and/or means for measuring the residence time of the 
fat-containing composition in the crystallizer-unit, which means are able 
to generate a signal responsive to the rotation speed of or residence time 
in the crystallizer-unit, 
(d) computing means which, on the basis of the signals generated by means 
(c), are able to calculate target values for the residence time and/or 
rotation speed, and 
(e) controlling means which may adjust the residence time and/or rotation 
speed of the crystallizer-unit in accordance with the target values 
calculated by (d) for the residence time and/or rotation speed. 
The means for chilling preferably is a Votator, a cooled cavity transfer 
mixer, a cooled static mixer or a cooling coil. 
The crystallizer-unit present in the apparatus, preferably is a C-unit, a 
cavity transfer mixer or a static mixer, more preferably the 
crystallizer-unit is a C-unit. 
The computing means in the present apparatus may be a programmed computer, 
but a similar effective control may be obtained if the apparatus comprises 
as computing means a relatively simple electronic circuit. Preferably, 
however, the computing means comprises a programmed computer. 
FIG. 3 is a block diagram illustrating the process and apparatus according 
to the present invention. 
In FIG. 3 vessel 1 contains an aqueous solution and vessel 2 contains a fat 
blend. Pump 3 feeds the combined water and oil stream to Votator 4, after 
which the combined composition subsequently passes a C-unit 5 containing a 
rotor 13, a Votator 6 and a resting tube (B-unit) 7. Both Votator 4 and 6 
are cooled by means of liquid ammonia. 
Computer 8 receives input signals from temperature probes 9 and 10, from 
device 11 which measures the rotational shaft speed of the C-unit and from 
mass-flow meter 16. The computer 8, on the basis of an experimentally 
derived relationship, computes a suitable combination of residence time 
and working intensity for the particular fat blend passing through the 
production line at that moment, and adjusts the mass flow through pump 3 
and/or the rotation speed of C-unit 5 accordingly. When computing a 
suitable combination for the residence time and working intensity computer 
8, besides the working intensity and residence time, also takes into 
account the crystallization rate of the fat blend being processed. 
The crystallization rate of the particular fat blend being processed is 
determined continuously by the computer 8 on the basis of the temperature 
difference observed between probes 9 and 10. If, for instance, the 
temperature difference observed between probes 9 and 10 increases, 
computer 8 will increase the mass flow through and/or reduce the rotation 
speed of the C-unit and thus maintain the degree of crystallization in the 
C-unit at an essentially constant level.