Process for low fat spread production

The invention provides a process for the production of reduced-fat spreads which comprises emulsifying, cooling and working a mixture of oil and water in a process line including at least one crystallizer, preferably an A-unit, and a high shear inversion unit, preferably a C-unit, in which at least a part of the oil, preferably 4-8% wt of the oil, is injected into the process stream after the crystallizer and before the inversion unit, and apparatus for carrying out the said process.

BACKGROUND OF THE INVENTION 
The present invention falls in the technical field of edible spread 
processing and relates to a process for the preparation of edible spreads 
and to an apparatus for carrying out this process. 
It is commonplace to use "Votator" (RTM) units in edible fat processing. 
These comprise both "A-units" and "C-units". 
A-units, serve both to cool and crystallise an emulsion, whereas C-units, 
while also being used for crystallisation are also used to apply 
sufficient shear to induce phase inversion of a oil in water emulsion or 
premix to a water-in-oil dispersion. In spread manufacture by the phase 
inversion process, it is commonplace to separate the cooling and inversion 
steps, such that cooling occurs in one or more A-units in line, prior to a 
C-unit which functions as an invertor. 
Our previous European patent EP 98664 discloses a process for producing a 
water-in-oil emulsion spread having a fat content of at most 60%, wherein 
an emulsion containing oil and water is both sheared and cooled in an 
apparatus internally coated with a layer of hydrophobic material selected 
from the group comprising PTFE and butter oil. In this process, fat 
flushing may be employed prior to start-up, so as to form the hydrophobic 
coating. No phase inversion occurs in this process. 
European patents EP 98664 and EP 40874 both disclose the general process of 
fat-flushing prior to continuous process operation. In this process fat is 
first circulated through the process line and a cream is introduced until 
the required process conditions are attained. Again, this is not a true 
phase-inversion process. 
It is difficult to maintain inversion with low fat levels especially if 
fats with high solids are being used. Problems in maintaining inversion 
are also caused when the process stream includes certain ingredients. 
Without wishing to restrict ourselves to any particular theory of 
operation, it is believed that the presence of, for example, oleaginous 
milk powders and other polar materials, in the process stream, hampers the 
inversion process. Such powders are considered important ingredients in 
edible spreads as they modify the organoleptic and physical properties of 
the products obtained. 
Failure of the inversion process results in so-called "cold-flushing" of 
the process line resulting in production of a microbiologically unstable, 
and organoleptically unacceptable product. Cold flushing occurs when phase 
inversion fails to occur. Inversion may only be recovered by stopping and 
restarting the process which results in plant down-time and can result in 
loss of materials. The risk of inversion failure at a particular 
throughput often determines the maximum production capacity of a spread 
manufacturing line. 
A further limitation on the capacity of some spread processing lines is the 
volume of product which may be packed in unit time. Products cannot 
normally be stored before they are packed and therefore the capacity of 
the packing apparatus is often a rate determining factor. There would be a 
great advantage in being able to double the throughput of a line as this 
would make it possible for a single line to serve two packing machines of 
the same capacity, and therefore to double capacity at the cost of a 
single packing machine. 
SUMMARY OF THE INVENTION 
It is an object of the invention to reduce the risk of cold-flushing in 
inversion processing when apparatus is operated at a high throughput. 
We have now determined that by continuously, or semi-continuously injecting 
a small quantity of liquid fat, prior to the inversion unit, the above 
mentioned difficulties may be simply overcome, and much higher line 
throughput can be attained without risk of inversion failure. 
Surprisingly, we have found that this benefit is accompanied by an 
improvement in product properties. 
Accordingly, the present invention provides a process for the production of 
reduced-fat spreads which comprises emulsifying, cooling and working a 
mixture of oil and water in a process line including at least one 
crystalliser and a high shear inversion unit, CHARACTERISED IN THAT at 
least a part of the oil is injected into the process stream after the 
crystalliser and before the inversion unit. 
Typically, the crystalliser is a tubular heat exchanger, of the A-unit type 
described above, although this may be replaced by alternative cooling 
means, such as a simple jacketed tube. 
Preferably the invertor is a C-unit of the type described above. 
It is believed that this oil injection facilitates inversion and thereby 
makes it possible to decrease the invertor pin speed and lower the power 
input. This reduces the amount of kinetic energy impressed on the product 
and results in a lowering of final temperature in the invertor. This is 
important when the quantity of solid fat in the invertor is critical for 
phase inversion to occur. 
Typically, the injected portion of oil comprises 2-12% by weight of the 
total fat phase content of the eventual product. Preferably, the injected 
quantity of oil is 4-8% by weight of the total fat content. We have 
determined that by injecting this quantity of oil, the throughput of the 
apparatus can be increased by up to a factor of two at an industrial 
scale. 
Oil soluble ingredients such as emulsifiers, antioxidants, colouring agents 
and flavours may be placed in the injected part but better results have 
been obtained when the oil soluble ingredients are present in the bulk of 
the process stream. 
Spreads production lines often comprise a sequence of several "A" and/or 
"C" units as described above. In a preferred embodiment the process aspect 
of the invention comprises emulsifying, cooling and working a mixture of 
oil and water in a process line including at least two A-units and at 
least one C-unit in an AAC sequence wherein the part of the oil injected 
enters process stream after the first A-unit and before the C unit. Most 
preferably, injection occurs between the second A-unit and the C-unit. 
While the oil can be injected at the process stream temperature, in certain 
embodiments of the invention the oil is injected at a higher temperature 
preferably in the range 40.degree.-80.degree. C., especially when 
injection is before the second A-unit. 
Additionally the present invention comprises a spread processing line 
including at least two A-units and at least one inverting C-unit in an AAC 
sequence and means for injecting edible oil into the process stream after 
the first A-unit and before the inverting C unit. 
In order that the present invention may be better understood it will be 
further explained by way of examples of the practice of the invention in 
the manufacture of 40% fat butter-based spreads and with reference to the 
accompanying drawings wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Examples 
A conventional spreads production line is shown in FIG. 1. A mixed fatphase 
and waterphase enters at the left hand side of the diagram and passes to 
the right at a maximum flow rate of some 80 kg/hr. The VOTATOR sequence 
comprises (1) a first A-unit, (2) a first C-unit, (3) a second A-unit, (4) 
a second C-unit serving as an invertor, (5) a third A-unit and (6) a third 
C-unit. The temperature of the process stream at the entry of the second 
C-unit is commonly between 5.degree. and 15.degree. C. 
A spreads production line modified according to a first embodiment of the 
present invention "method (A)" is shown in FIG. 2. The same numbering is 
used as in FIG. 1, with the addition that (7) is the entry point into the 
process stream of the injected fat carried along line (8). It is noted 
that injection occurs after the first C-unit (2) and before the second 
A-unit (3). 
A spreads production line modified according to a further embodiment 
"method (B)" of the present invention is shown in FIG. 3. As with FIG. 2 
the numbering used in FIG. 1 has been employed, and again there is shown 
the addition of the entry point (7) for the injected fat phase and line 
(8) for the supply of this phase. It is noted that injection occurs after 
the second A-unit (3) but before the second C-unit (4) which serves as the 
invertor. An additional feature shown in this figure is the additional 
A-unit (9) which serves to cool the injected oil in flow line (8). 
In order to compare the process of the present invention with the methods 
of the prior art a standard low calorie butter formulation was processed 
both according to the present invention as illustrated in FIG. 2 and 
according to the method illustrated in FIG. 1. 
The formulation comprised as follows, all percentages being expressed as 
wt% on final product: 
______________________________________ 
Skim Milk Powder 1% 
Gelatine 3% 
Butterfat 40% 
Water 56% 
______________________________________ 
In the comparative experiment all the above ingredients were combined into 
a generally oil in water emulsion pre-mix as is known in the art. This 
premix was fed along the operating process line of FIG. 1 at a varying 
throughput. As the process stream passed through units (1)-(3) it was 
cooled and worked. Phase inversion occurred in unit (4) to form a water in 
oil spread which was further worked and cooled in units (5)-(6). The 
product was acceptable as an average low-calorie butter. It was determined 
that the maximum throughput which could be maintained with this process 
line was around 80 kg/hr. Above this value it proved progressively more 
difficult to maintain phase inversion in unit (4) without cold-flushing as 
described above. 
In a first set of trials 2-8% by weight of the fat phase was injected at 
point (7), according to the method (A) as shown in FIG. 2. and the 
throughput increased to the point at which inversion failed. The 
temperature of the injected oil was 40.degree.-80.degree. C. The oil was 
heated by the use of a hot water jacketed tank prior to injection. No 
other process parameters were varied. It was determined that the 
throughput could by this method be increased to 160 Kg/hr without loss of 
phase inversion in unit (4). 
The injection apparatus comprised a dosing pump capable of delivering oil 
at above the line pressure. A "Bran & Luebbe" (Registered Trade Mark) 
oil-dosing pump was found suitable. Such pumps are commonly employed 
upstream in the process line to dose oil and water phase together. The 
injection point was formed by fitting a "T-head" into the process stream. 
The products prepared according to "method A" were compared with the 
controls as prepared above. No difference is taste was noted by an expert 
panel. However a significant improvement in the melting properties and 
consistency of the product was noted when the injection comprised 4-8% of 
the fat phase by weight of that phase. 
In a second set of trials 4-12% of the fat phase was injected at point (7), 
according to the method (B) as shown in FIG. 3. and the throughput 
increased to the point at which inversion failed. The oil was injected at 
a temperature of 5.degree.-15.degree. C., having been cooled with an 
A-unit type scraped surface heat-exchanger. No other process parameters 
were varied. It was determined that the throughput could by this method be 
increased to 150 Kg/hr without loss of phase inversion in unit (4). 
The products prepared according to method (B) were compared with the 
controls by an expert panel. Again, while no difference in taste could be 
perceived the products were of a better consistency and had improved 
melting properties. As with method A the best results were obtained with 
injection of from 4-8% of the fat phase by weight of that phase. 
From the above results it is seen that the present invention can enable an 
increase of process throughput of up 100% as compared to the conventional 
process. This doubling of the throughput is accomplished without doubling 
the energy cost. 
The above method (B) was repeated at industrial scale with a 108 liter 
C-unit of the "Merksator MF153H" (Registered Trade Mark) type. This is 
normally operated at a throughput of 700-800 kg/h with the above mentioned 
composition. Using method (B) it was possible to increase throughput to 1.5 
tonnes/hr, with the same risk of inversion failure and without any 
reduction in product quality.