Extruded snacks

Brief Knowledge about Expanded Extruded Snacks

1. EXTRUDED SNACK
FOODS
PREPARED BY:-
SOURABH BHARTIA
B.Sc. & M.Sc. (Food Processing & Technology)
University Teaching Department, Atal Bihari Vajpayee University, BSP, C.G., INDIA
[email protected]
www.linkedin.com/in/sourabh-bhartia

2. CONTENTS
EXTRUDED SNACK FOODS 1
DIRECT EXTRUDED SNACKS 2
COEXTRUDED SNACKS 12
2
nd
GENERATION SNACKS 21
3
rd
GENERATION SNACKS 24
COLLETS 27
COMMON INGREDIENTS 34
FACTORS INFLUENCING EXTRUDED SNACKS 40
BIBLIOGRAPHY 49
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3. EXTRUDED SNACK FOODS
1
The snack food processes, which use extrusion cooking, include the
production of direct expanded extrudate and extruded pellets or half
products of the third generation snacks.
The extruded half products require a secondary puffing step.
Prior to consumption, the third generation snacks are puffed in a fryer,
or expanded in hot air or a microwave oven.
Snack food technology of direct expanded, and shaped snacks is similar
to RTE cereals processes, but normally performed at lower moistures, so
that a higher energy input from mechanical sources occurs.
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4. DIRECT EXPANDED SNACKS
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5. DIRECT EXPANDED SNACKS
Direct expanded snacks are typically puffy, crispy or crunchy cereal or
starch “finger foods” that come in a variety of shapes and sizes and
which are textured and often coated to make them convenient, tasty and
fun.
They are eaten at all times of the day and can be sweet or savory.
Snacks are eaten for pleasure, but increasingly, they need to be healthier
as well.
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6. HISTORY OF DIRECT EXPANDED SNACKS
The directly expanded maize snack was the first industrial form of snack
food.
The Adams Company manufactured it in the 1940s from maize grits using
a Snack foods 173 short-barrelled single-screw extruder.
It continued to be manufactured for many years before the principles by
which it was produced began to be understood and indeed it was not
until the 1970s and 1980s that the true nature of extrusion cooking for
direct expansion was determined by careful research.
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7. SHAPES OF DIRECT EXPANDED SNACKS
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8. PRINCIPLES OF DIRECT EXPANDED SNACKS
The transformation of starch-rich feed stocks such as maize grits, wheat,
rice or potato flour into hot melt fluids, which can be expanded as they
emerge from a die, occurs on the screw between the feed port and the
die.
Almost all the heat was obtained from the barrel and the temperature
rose to 70–80⁰C for a barrel profile for three sections 2.5 L/D of
30/50/90⁰ C.
The heat transfer was related to particle size and smaller particles
heated up more quickly.
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9. Diagram of the expansion of an extrudate at the die of an extruder showing
bubble growth and stabilization of the foam.
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10. MODIFICATIONS FOR SNACK FORMATION
FLAVOURING
TEXTURE MODIFICATION
SHAPING AND CUTTING OF THE DIRECTLY
EXPANDED SNACKS
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11. FLAVOUR MODIFICATION
The flavours generated in snacks by the basic raw materials such as
maize, potato, rice and wheat are also different in character and
intensity.
They are also changed by processing in relation to temperature and time
spent in the hot zones of the extruder.
It is possible to adjust the flavour of snacks by coating them with added
flavoruing in post-extrusion processes.
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12. TEXTURE MODIFICATION
Pure starch polymers will form finely textured foams in extrusion.
Their cell walls will be extended to give very thin dimensions and the
fluid may be manipulated to give a small number of large cells or a large
number of very small cells.
The formation of bubbles in the starch melt is affected by the presence
of nucleating substances, viscosity and the manipulation of the die
pressure.
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13. SHAPING AND CUTTING OF THE DIRECTLY
EXPANDED SNACKS
The flavours generated in snacks by the basic raw materials such as
maize, potato, rice and wheat are also different in character and
intensity.
They are also changed by processing in relation to temperature and time
spent in the hot zones of the extruder.
It is possible to adjust the flavour of snacks by coating them with added
flavoruing in post-extrusion processes.
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14. COEXTRUDED SNACKS
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15. COEXTRUSION
•Co-extrusion is a process that combines two different extruded streams
to obtain two-component products characterized by dual texture and/or
color.
•The two materials can come from two extruders or from one extruder
and one pump.
•This process can produce a snack with two different flavors, or two
textures or two colors.
•The most common snack produced by co-extrusion is a cereal-based
outer tube with a cheese filling inside.
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16. CO-EXTRUSION SYSTEM
EXTRUDER CREAM FEED PILLOW CRIMPER DRYER SEASONING
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17. EXTRUDER: Ingredients are texturized and cooked through a combination
of heat, mechanical shear and moisture addition. A co-extrusion die then
produces a single stream of product with two components….
“a cereal outer and a centre-filling”.
CREAM FEED: Stores and supplies cream to the co-extrusion die.
PILLOW CRIMPER: After leaving the die, a pressing roll ensures streams
are the correct thickness. They are then separated and spaced before
two rollers with multiple blades pinch streams along their lengths to
form continuous strands of sealed pillow shapes. These are dried and
broken into individual pieces.
DRYER: The products are dried before being passed to the seasoning
unit.
SEASONING: Products are seasoned. Savory snacks are generally coated
with oil and seasoning; sweet snacks can be sugar coated and
subsequently dried.
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18. CO-EXTRUSION SYSTEM FLOW SHEET
DRY MIX FOR TUBULAR SHELL CREAM DOSIMETER
PUMP BUNKER
FILLER DIE EXTRUDER
COOLING
EMBOSSING CUTTING
DRYING COOLING
ADDING SPICES
PACKAGING
WATER
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19. FATS AND OIL
Fats and oils play an important role in frying, coating and filling of the
extruded snack foods.
Coating with oil and seasonings is the final processing step in the
production of snack foods.
The seasonings allow the manufacturer to create a variety of flavors.
The oil is the carrier of seasonings and gives the extrudate a better
mouth feel.
The oil and seasoning coating usually makes up to 35% of the finished
product.
The shelf life of these snacks is limited, because of migration of moisture
and/or oil from the filling to the outer shell.
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20. METHODS OF CO-EXTRUSION
In the food industry, there are two most commonly used methods of
coextrusion.
In the first method(a) the filler is fed perpendicularly to the axis of the
extruder, while in the second method(b) the filler is fed through the axis
of the die.
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21. There are three basic types of co-extruded
snack foods in the market
1.CEREAL-BASED TUBES WITH CEREAL-BASED FILLINGS,
2.CEREAL-BASED TUBES WITH FAT-BASED FILLINGS,
3.CEREAL-BASED TUBES WITH WATER-BASED FILLINGS.
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22. TYPES OF SNACK FOODS
Each snack processor may use a specific unit operation and somewhat
different technologies to produce unique snacks. There are many ways to
classify snacks. Manufacturers use three main terms to identify snacks:
First generation snacks: (Simply Extruded Snacks)
In this category all the natural products used for snacking, nuts, potato chips and
popped popcorn are included.
Second generation snacks: (Expanded Snacks)
The majority of the snacks fall in this category. All the single ingredient snacks, simple
shaped products like corn tortilla chips and puffed corn curls and all directly expanded
snacks are included in this category.
Third generation snacks: (half products” or pellets)
In this category, multi ingredient formed snacks and pellets, made by extrusion
cooking are included.
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23. 2
nd
GENERATION SNACKS
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24. SECOND GENERATION SNACKS
Second generation snacks or expanded snacks, where most extruded
snacks are classified, are usually low in bulk density and are often
marketed as high fibre, low-calorie, high protein and nutritional
products.
Different raw materials used to produce these kinds of snacks i.e. flours
and/or cereals and tubers starches and proteins, are processed in a
extruder resulting in a continuous mass, that is cut into pieces of
uniform size, being afterwards dried, flavored and stored.
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25. 2
nd
GENERATION SNACKS PROCESS
(DIRECT EXPANSION PROCESS)
BLENDING OF RAW MATERIALS
PRE-CONDITIONING
EXTRUSION
DRYING
FLAVOURING
PACKING
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26. 3
rd
GENERATION SNACKS
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27. THIRD GENERATION SNACKS
Third-generation snacks or pellets are also called semi or half products,
because after extrusion cooking they are dried to a stable moisture
content and then expanded by frying in hot oil, puffing in hot air or
microwaving and infrared heating as new variants.
After expansion products are spiced with various types of spices and
then packaged and sold as ready-to-eat (RTE) snacks.
They can also be flavoured before expansion and sold as pellets, for
preparation at home.
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28. THIRD GENERATION SNACKS PROCESS
(PALLETS PROCESS)
BLENDING OF RAW MATERIALS
PRE-CONDITIONING
EXTRUSION
COOLING
DRYING
FRYING OR HOT AIR PUFFING
FLAVOURING
PACKING
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29. COLLETS
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30. COLLET EXTRUSION
The majority of extruded snacks are in this category.
This group is also referred to as “collet” or “second generation snacks.”
In general, expanded snacks are made on high hear extruders.
These are high-fiber, high-protein, and low calorie snacks. Some
examples are corn curls, onion rings, three dimensional snacks, and
potato sticks.
These types of snacks can be seasoned with a variety of different flavors,
oils, salt, sugars, etc.
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31. TYPES OF COLLETS
BAKED COLLETS
FRIED COLLETS
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32. BAKED COLLETS
Baked collets are another example of extruded snacks.
This includes products such as baked corn curls, onion rings and potato
sticks.
Baked collets can be made with different cereal grains and tuber flours.
Protein, fibers, cellulose, and bran can be blended with cereal grain up to
20 percent to make healthy snacks.
Potato sticks are usually made by mixing potato flour with corn or rice
flour.
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33. BAKED COLLETS PROCESS FLOW
RAW MATERIAL
EXTRUSION
CUTTING EXTRUDATES
DRYING AT DRYER
COATING
PACKAGING
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34. FRIED COLLETS
These are the most familiar extruded snacks in the market.
A special die arrangement gives the product twisted, puffed shape.
These collets are made on collet extruders.
The product is then fried in vegetable oil, and coated with cheese and
some other flavor.
During frying, the moisture level in the product reduces from 8 percent
to 1-2 percent.
The most common material used for fried collet is corn meal.
Some other cereal grains can also be used for this type of product.
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35. FRIED COLLETS PROCESS FLOW
RAW MATERIAL
MIXING/SIFTING
EXTRUSION
FRYING
COATING
PACKAGING
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36. COMMON INGREDIENTS
Common Ingredients Extrusion technology, have led to more diverse and
complex formulations for snack foods.
The most common source of ingredients is:
corn, wheat, rice, potato, tapioca, and oats.
A major ingredient in snack formulation is starch.
In its natural form, the starch is insoluble, tasteless, and unsuited for
human use. To make it digestible and acceptable, it must be cooked.
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37. CEREAL SOURCES
Almost any cereal can be extruded, but if expansion is a major objective,
the numbers of functional cereals are limited to degermed corn/grits and
rice.
Cereals that have high amounts of lipids are more difficult to expand due
to dough slippage within the extruder barrel.
This type of cereal usually requires high moisture and high temperature
before significant puffing will occur.
In general, starches with 5-20 percent amylose content will significantly
improve expansion as well as the texture of snack foods.
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38. RICE AS STARCH SOURCE
Small, tightly packed starch granules that hydrate slowly;
Becomes sticky when it gelatinizes;
Choose long grain varieties over medium and short grain varieties as
they are much less sticky when cooked;
Rice is very digestible even when cook values are low;
Rice bran may contain up to 40% starch.
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39. CORN AS A STARCH SOURCE
Good expansion;
Excellent binding;
Sticky at high levels (>40%).
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40. WHEAT AS STARCH SOURCE
Good binding;
Good expansion;
Can be sticky if overcooked;
Contains gluten (good binder);
Most widely available starch source;
Often utilized as wheat flour which has most of
the bran removed.
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41. TUBERS AS STARCH SOURCE
(POTATO & CASSAVA)
Excellent binding (at 5% levels);
Requires less total starch in diet;
Good expansion;
Often precooked;
Smooth pellet surface;
Increased cost.
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42. Factors influencing the degree of puffing
of snacks during extrusion
The amount of moisture in the feed material, dough residence time in
the extruder barrel and cereal particle size.
To manufacture expanded products, the pressure and temperature are
increased, while the moisture level is accurately controlled.
When the product exerts the extruder through the forming die, the
change in atmospheric pressure causes the internal moisture to turn to
steam.
This puffs the fully-cooked dough into an expanded product.
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43. FACTORS INFLUENCING EXTRUDED SNACKS
Raw Materials:
The most used raw materials in the extrusion process are- starch and-
protein based materials.
The structure of the extruded products may be formed from starch or
protein polymers.
In general, the chemical or physicochemical changes in biopolymers
that can occur during extrusion cooking include:
- binding, cleavage, loss of native conformation, fragment recombination and thermal
degradation.
Thermally labile compounds such as flavors and vitamins maybe
injected immediately before the die to minimize exposure to heat and
shear.
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44. Moisture:
If high expansion is required in a low moisture product, finely milled forms
of harder endosperm types will give excellent results.
If the product requires low to medium expansion, some of the hard material
may be replaced by soft flour; and for low expansion in a dense product such
as breading crumb, soft flour may be used.
Maximum expansion degree is closely related to starch content.
Maximum expansion is obtained with pure starches (an increase of 500% in
product diameter), followed by whole grains (400%)and with lower
expansions for seeds or germ (150-200%); the starch content of these
products is 100, 65-78, 40-50 and 0-10,respectively.
The minimum starch content for expansion is 60-70%.
In the extrusion process of expanded products with low moisture, the
expansion of the final product is inversely related to the moisture of the raw
material and directly related to the increase in extrusion temperature;
however, the effect of moisture is more significant
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46. Fibre:
The physical presence of fibres in air cell walls reduces the expansion
potential of the starchy film, larger particles, such as bran, tend to
rupture air cell walls of the extruded product, causing a reduction in
expansion index.
Non-starch polysaccharides, such as fibers, may bind water more
strongly than proteins and starch during extrusion.
This water binding capacity inhibits water loss at the die, that is, at the
exit of the extruder, reducing expansion.
The starch present cannot be totally gelatinized in the presence of fiber
and is thus not capable of supporting expansion.
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47. Lipids:
The presence of lipids in quantities lower than 3% does not affect
expansion properties, however, in amounts above 5%,reduction in
expansion rate is considerable.
The increase in lipid content can be corrected through the reduction in
conditioning moisture content, so as not to affect the expansion index
of second generation products (directly expanded snacks).
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48. Temperature:
Another important parameter for extrudate expansion is process
temperature. Products do not expand if “temperature < 100°C”.
Expansion increases with the increase in temperature when moisture
content of the material is close to 20%, due to lower viscosity,
permitting a more rapid expansion of the molten mass, or due to an
increase in water vapor pressure.
The reduction of expansion at very high temperatures is attributed to
an increase in dextrinization, weakening starch structure.
Expansion occurs in both radial and axial directions, at different
degrees, depending on the viscoelastic properties of the melt.
Vaporization of moisture and cooling of the extrudate serve to bring the
product from a molten to a rubbery state; further drying is usually used
to produce the brittle, fracturable texture typical of these products.
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49. Fibre:
The physical presence of fibres in air cell walls reduces the expansion
potential of the starchy film, larger particles, such as bran, tend to
rupture air cell walls of the extruded product, causing a reduction in
expansion index.
Non-starch polysaccharides, such as fibers, may bind water more
strongly than proteins and starch during extrusion.
This water binding capacity inhibits water loss at the die, that is, at the
exit of the extruder, reducing expansion.
The starch present cannot be totally gelatinized in the presence of fiber
and is thus not capable of supporting expansion.
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50. PROCESS TEMP.
(⁰C)
MAX. PRESSURE
(bar)
MOISTURE
(%)
MAX. FAT
(%)
COOK (%)
PELLET PRESS 60-100 12-18 12 15-30
EXPANDER 90-130 35-40 12-18 12 20-55
DRY
EXTRUSION
110-
140
40-65 12-18 12 60-90
WET EXTRUSION:-
SINGLE
SCREW
80-140 15-30 15-35 22 80-100
TWIN SCREW 60-160 15-40 10-45 27 80-100
TYPICAL PROCESS PARAMETER
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51. BIBLIOGRAPHY
ADVANCES IN FOOD EXTRUSION TECHNOLOGY- MEDENI MASKAN &
AYLIN ALTAN;
EXTRUSION COOKING TECHNOLOGIES AND APPLICATION- ROBIN
GUY;
https://www.researchgate.net/publication/273692346_Coextru
sion_of_food_products_-
_essence_and_technical_characteristics .
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52. THANKYOU
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