How to choose your next Extruder? | Foodresearchlab

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HOW TO CHOOSE
YOUR NEXT EXTRUDER
An Academic presentation by Dr. Nancy Agnes,
Head, Technical Operations, FoodResearchLab
Group www.foodresearchlab.com Email
info_at_foodresearchlab.com
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Today's Discussion
OUTLINE
In-Brief Introduction Global Leaders
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In-Brief
During the extrusion process, raw materials are
ground to the preferred size, which then passes
through a preconditioner. At this stage, steam
may be injected into the raw materials and
finally reaches the die assembly at a defined
throughput. Extruder feeds both solid and liquid
ingredients, mostly grain pulse, root-based
foods, water, oil, sweeteners, colours, and
added vitamins and minerals. Extruders design
and specification can be tailored for the ideal
and intended manufacturing application of food
products.
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There is a complex interaction between feed
ingredients, extruder design and operating
conditions, affecting product development,
quality improvement, consistency, and optimum
operational efficiency. Extruders can generally
be classified based on the build type, such as
single screw extruder, twin screw extruder,
parallel twin screw extruder, pelletizing
Extruder and dry Extruder. The following
variables affect the efficiency of the extrusion
process. Firstly, raw materials physical and
chemical properties, such as viscosity, moisture
content etc.
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The dough's rheological behaviour can greatly
influence the final product quality, process
time, and heat transfer. Secondly,
thermomechanical cooking factors, such as the
design of the equipment including the type of
screw, variable screw diameters (D) and lengths
(L) and barrel section of the machine, die
design and opening shape and section. The die
plate assembly design is a crucial part of the
operation as it is responsible for forming the
desired product shape and adds flow resistance to
achieve a final output of transformed
materials. Bronze dies produce better quality
pasta compared to stainless steel dies.
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Finally, operating conditions of the equipment
such as screw speed, temperature and overall
water content contribute to the process's
efficiency. For instance, during the extrusion
process, caution must be given to the heat
generated from screw elements, the heating system
and the self-heat gained by the barrel's
viscosity. Water is greatly used in combination
with the extrusion process to characterize the
melting behaviour and overall final dough
rheology. Moreover, it is also used in the form
of steam to impact the total extruder energy
output.
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Such usage can significantly impact the extruder s
election, design and performance and mainly on
the product quality. The remaining water is evapo
rated during the venting stage to achieve
accelerated cooling to form the final
product. There are different categories of extrud
ers, such as cold, hot, steam-induced and
co-extrusion. Cold extrusion is mainly used for
gentle mixing and shapes the dough without
heating or cooking, such as pasta.
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Hot extrusion converts the raw materials under
high temperature and pressure in a short
time. This type is considered for textured foods
such as pet food. Steam-induced extrusion is used
for determining the textural attributes of highly
expanded products, such as expanded breakfast
cereals. Co-extrusion can be very helpful for
products with dual textures, such as crispy shell
and soft filling. Co-extrusion combines stem
induced expansion as well as injection filling.
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Introduction
Extruders can be thought of as high temperature
short time cooking (HTST) equipment, that can
transform various raw ingredients by forcing
through a die to create the desired final
product shape during new product development in
the food development companies. A food extruder
accelerates the restructuring process for food
ingredients, compared to other traditional food
processing methods. Extruders are highly multi
purposed as they can be used to cook, form, mix,
and texturize food products with added flavour,
quality retention and increased productivity at
a low-cost.
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Global Leaders
There are several types of extruders available in
the market, confusion for food manufacturers,
based on the product type.
Some manufacturers who supply single-screw
extruders are American Extrusion International,
Wenger, Extru-Tech, and Schaaf
Technologie. Companies such as Buhler, Baker
Perkins, Clextral and Coperion offer twin-screw
extruders. Brabender CW offers extruders at a
pilot scale level.
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Extruder KE 19 is a single screw extruder with a
screw diameter of 19mm and has an output of
5kg/hr. Single screw extruders are open channel
extruders, which can be thought of as a drag
flow pump, with the final output delivery
controlled by the pressure flow. This Extruder
comes in handy for product development,
specifically to test the extrusion properties of
different raw materials and develop the
processing characteristics. Process stimulation
could be done with ease under low RD costs.
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Stimulations such as cold forming, shaping,
gelatinization, plasticization and
expansion. This Extruder also aids in increasing
the time efficiency to characterize the sensory
and rheological characteristics. Brabender CW
also offer a twin screw variety, TwinLab-F
20/40. Twin screw extruders contain two screw as
the name suggests which counter-rotate forming
closed channels.
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The output from this type of Extruder is less
vulnerable to pressure flow and can be
considered as a positive displacement pump. The
TwinLab-F20/40 model has been designed for lab
scale applications at different L/D
ratios. New product developments in snack, breakf
ast cereals, sweets, and pet food category can
be prepared on a lab scale. It contains either a
600 or 1200 rpm motor and horizontally divided
barrel that can be opened to observe and clean.
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It also contains 4 different heating zones and
water cooling. Alternatively, Buhler group offer
twin screw extruders. ECOtwin variety is
specifically tailored for the pet and sea food
industry. It offers a screw diameter of 5 to 7
inches and produces 20,000kg/hr. Whereas the
POLYtwin option is a parallel twin screw
extruder. Its screw diameter ranges from 2 to 7
inches and offers up to 450 kg/hr.
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Due to its modular design, it is highly
flexible. It can be used for food ingredients,
breakfast cereals, sea food and pet
food. POLYtwin also offers a robust and fully
automated screw ejection unit, thus reducing the
risk of damaging the elements. Knife heads can be
changed easily without disrupting the production
process. Flexible cutter for a consistently high
quality end product is yet another advantage.
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