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Double emulsions for fat reduction: Fundamental investigations on influencing the microstructure of double emulsions and how the structure influences product properties relevant for consumers (mouth feel, creaminess, fatty taste, saturation)
Project
Project code: DFG/AiF-Cluster 3
Contract period: 01.01.2009
- 31.12.2012
Purpose of research: Applied research
The aim of this project was to produce food-grade W/O/W double emulsions
with adjustable structures. Therefore, a two-step process was used. In the first
emulsification step, a water-in-oil emulsion is produced which is again dispersed
in water to produce the final double emulsion.
In the first part of the project, it could be shown that in principle it is possible to
stabilize the inner W/O emulsion without using emulsifiers that underlie restrictions
for the use in food products. Pectin as a gelling agent was used in the dispersed
water phase of the W/O emulsions. A targeted temperature shift during
the production of the emulsions was used to start the gelation and therefore
stabilize the droplets/gel particles. A high pressure homogenizer with an orifice
was used. By using the modified SEM technology (simultaneous emulsification
and mixing) it was possible to first break the droplets and then stabilize them
by decreasing the temperature by mixing with cold oil. Bimodal droplet size distributions
were observed in all emulsions. Therefore, the process first was further
investigated in order to better understand this observation and to control
the process later on. It was possible to characterize the flow patterns by using
the discharge coefficient CD. This is a characteristic parameter known from flow
measurements which was adapted to the process. It was possible to classify the
current flow pattern and use it to control the process. Furthermore, it could be
shown, that the flow pattern in and behind the orifice influences the resulting
droplet sizes of the emulsion significantly. The bimodal droplet size distributions
were caused by the transient flow behavior (between laminar and turbulent
flow). In addition, instabilities were observed when the dispersed phase content
was increased (which is needed for significant fat reduction). These findings did
not allow the usage of this process in the further investigations in this project.
Nevertheless, they showed the relevant parameters for the development of this
process for industrial applications.
In this DFG project, inner emulsions stabilized by the emulsifier PGPR (in authorized
quantities) and produced with a colloid mill were used for the further investigations.
Droplet sizes below 1 μm could be realized like that.
Both, droplet sizes and encapsulation efficiency of the inner droplets, are very
important for the functionality and stability of double emulsions. Therefore,
these parameters have to be measured in order to characterize the emulsions.
Unfortunately, it was shown that the coloring method described in literature
shows a lot of inaccuracies. Another method based on measurements with differential
scanning calorimetry was adapted and further developed for the characterization
of W/O/W double emulsion.
For scientific purposes membrane processes are used very often to produce
multiple emulsions. However, they are not really established for industrial applications
till now because of occurring difficulties like fouling of the membranes.
Therefore, it was investigated if it is possible to use conventional emulsification
devices to produce double emulsions – rotor stator devices (tooth rim dispersing
machine and colloid mill) and high pressure homogenizers. We investigated
how suitable they are for the breakup of filled droplets. It could be observed that
comparing the production of emulsion droplets of the same size the highest encapsulation
efficiency could be achieved using the colloid mill.
Sensory studies of simple (normal fat content) and double (fat reduced) emulsions
were conducted in cooperation with the cluster partner of sub-project 9.
The investigations of simple emulsions gave a hint on required maximum outer
droplet sizes in double emulsions. Furthermore, double emulsions with two
different amounts of inner water droplets were compared to a full fat reference
emulsion. In order to make them comparable, the viscosities of the emulsions
were adjusted by dilution of the double emulsions. In spite of significant differences
in fat content (19, 23 and 50 %) the panelists were not able to distinguish
between the 3 samples.
In conclusion, the results of this research project indicate that double emulsions
show a great possibility to reduce the fat content in food. By using double emulsions
the consumer relevant sensory properties do not change perceivably in
comparison to normal full fat emulsions. By using the two-step process a scalable
technical production process was found. In addition, it could be shown,
how material and process parameters influence the microstructure of double
emulsions and therefore their properties. Furthermore, the results indicated that
the stabilization of double emulsions without using conventional emulsifiers is
still challenging. In addition, the preservation of the inner droplets during the
second emulsification step seems to be crucial for the whole production and
needs to be further investigated.
Section overview
Subjects
- Food Chemistry
Collaborative Project
Saturated fat perception and regulation: approach to the development of reduced-fat foods
Funding programme
Excutive institution
Institute of Process Engineering in Life Sciences Section I: Chair of Food Process Engineering (LVT)
