Basics of the Food Extrusion Process...EE Extrusion Wear Parts EE Drying - Coating TE Extrusion USD/ton Example specific production costs USD/ton Example: Marine feed plant 40‘000

Basics of the

Food Extrusion

Process

36th Fish Feed and

Nutrition Workshop

Chad Myers - Buhler

Epic Saga….…of Extrusion… Science or Science Fiction?

Food Extrusion Workshop | Minneapolis |


Webster’s definition of the verb “extrude” is: “to shape by forcing through a specially designed opening often after a previous heating of material.”

Therefore we can safely say that an “extruder” is a machine which continuously takes a soft, perhaps heated, material through a die.

So based on the two previous comments, we must conclude that a “twin screw extruder” is a machine which has two screws and continuously takes a soft, perhaps heated, material through a die.

What is Extrusion?


Co-rotating Twin Screw

Main advantages of co-rotating twin-

screw:

• Conveys like a positive displacement

pump

• Has very good mixing properties

• Elements wipe each other (“self –

cleaning“)

• Flexible screw design


Co-rotating Self cleaning, Erdmenger profile

D

E

A

FR1

R1

B

C


kneading

mixing

homogenizing

gelatinizing

texturizing

shaping / forming

heating

cooling

The twin screw extruder is a continuous working process system which provides many basic process steps:

coloring

cooking

melting

flavor development

evaporation

pressurizing

expanding

degassing / depressurizing

What is twin screw extrusion? - Unit Operations

Basic process steps are broken down into:

Units of Operation= smallest possible process step (can not be divided up into smaller units)


Basics of Extrusion Process - Raw Materials

Native flours

Pre gelatinized flours

Semolina

Coarse fractions of cereal grains

Starches

Proteins

Fibers, Bran

Water / Steam

Oil, Fat, Meat

Salt, Sugar, Spices

Flavors, Vitamins, Emulsifiers, Colors ….


Traditional fields of twin-screw extrusion

1. Snacks and Cereals (direct expanded, indirect expanded)

2. Pet-Food and Aquatic Feed

3. Ingredients

Bread Crumbs, Recomposed Rice, Modified flours / starches, Textured

proteins, Diary, Chocolate

4. Technical Applications / Pharmaceutics

Tobacco, Slug pellets, Fertilizer, Packaging foam, Biodegradable plastics

5. Plastics


Diversity of twin screw extruded products – some samples

Snacks

Textured Proteins Breakfast Cereals

Aquatic FeedFilled Pillows

Modified

Flours / Starches

Bread Crumbs

Fortified Rice


Basics of Extrusion Process -Modification of Product Characteristics

Change of:

Shape

Color

Taste

Bulk Density

Texture

Degree of gelatinization

Composition

etc.

Temperature (steam)

Water

Time

STE

SME

Temperature (friction)

Shear

Aquatic Feeds

36th Fish Feed and Nutrition Workshop

Chad Myers - Buhler

12 | Aquatic Feeds | Munz PE61 | 2009 | © Bühler

Aquatic feeds production - Objective

Fish feed producers

Production of competitive fish feeds at

minimal cost

Integrated producers

Production of complete nutrition at minimal

cost and maximum efficiency, i.e. minimal

cost for maximum production of meat


590.0

49.3

30.3

9.2

5.0

4.4

3.2

2.5

2.4

1.1

0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0

Raw Material

Financing Costs

Personnel

Packaging, Others

TE Drying

EE Grinding, Others

EE Extrusion

Wear Parts

EE Drying - Coating

TE Extrusion

USD/ton

Example specific production costs USD/ton

Example: Marine feed plant 40‘000 t/y

Only a minute improvement in the final product value would justify the need for significant additional wear or energy cost !


Processing cost – Aquatic Feeds and Petfoods

* can be actively controlled by SME and Density Control

** occurring, due to the extruder design and raw materials used

TSE SSE

Mechanical energy dissipation kWh/t 20-40 * 20-30 **

Wear part cost USD/t 0.7-1.0 0.5-0.7

Steam for preconditioning % 7.5 7.5

Steam for drying % 22 22

(alternatively natural gas, direct drying) m3/t (13) (13)

Total steam requirement % 29.5 29.5

Liquid fuel for total steam production m3/t 20 20


Aquatic feeds – why extrusion

Good water stability, no hard pellets, but...

Fast water absorption, but good water

stability

Textured proteins and gelatinized starch

Correct density (floating – sinking)

Minimal loss of nutrients in water

Reduction of anti-nutritive compounds

Pellets with precise sizes without breakage

or fines

Flexibility in least-cost formulation

... better quality and less fines


Aquatic feeds - process steps

Intake, batching, grinding

Mixing Micro ingredients

Extrusion

Drying

Sifting, Grading

Packaging

Vacuum coating


Aquatic feeds - extrusion process

Major farmed

species


Chad Myers - Buhler



Common Carp, Silver Carp, Grass Carp, Big Head Carp, etc.

Omnivorous, herbivorous

Good sensory abilities

Warm water, i.e. 20-26°C

China is biggest producer of carp

Production in ponds, extensive or intensive,

often as polyculture together with other species

High enzymatic activity, good starch digestion

Requirements

low to medium protein content, i.e. 28-36%

low fat content, i.e. 6-15%

pellet diameters 1.0-4.0mm

usually floating or slow sinking pellets, density

450-550 g/l


Tilapia, Catfish

Omnivorous

Use entire water column

Good sensory abilities


Fresh water, temperature range 20-26°C, Tilapia

adapts well to salt or brackish water

Produced in ponds and raceways

Fast, vigorous eaters, stir water while feeding

High enzymatic activity, good starch digestion

Requirements

low to medium protein content,

i.e. 28-36%



usually floating or slow sinking pellets, density

450-550 g/l


Salmon, Trout

Carnivorous

Feeding in entire water column, require high

oxygen level

Sensitive to high nutrient loading of water

Fresh or saltwater, temperatures 5°-16°C

Active feeders

Tolerate only limited amount of digestible

starches

Requirements

High protein content i.e. 38-45%

high fat content, i.e. 25-35%


Good conversion rates due to high costs of

formulations

floating or sinking pellets, depending on

culture method, i.e. 480-640 g/l


Shrimp

Omnivorous, detrivorous

Bottom feeders, i.e. near anaerobic zone

Poor visibility, high sensory abilities


Fresh water and salt water species

Produced in ponds or recirculative systems

Slow eaters, messy eaters

High enzymatic activity, good starch

digestion

Requirements

low to medium protein content,

i.e. 30-38%



fast water absorption, good water stability

soft, pliable, meaty texture after rehydration

good sensory properties

100% sinking pellets, density > 600 g/l


Problems with shrimp feeds

Farming – conversion rate

Nutrients are lost due to feeding behavior

Nutrients are leaching in to the water

Digestibility of ingredients (starch

gelatinization, protein denaturation,

antinutrients, etc.

Wasted and excreted nutrients compete

for dissolved oxygen, increase health risk

Feed mill – production cost

Shrimp feeds require cost intensive

processing (i.e. long-term conditioning,

pelleting, post conditioning, drying,

coating, cooling)

Raw material cost (i.e. compromising

between cost, nutritional properties and

water stability)


Shrimp - starch digestibility


Water stability and leaching of nutrients (flavor)

Larval diets,

micropellets


Chad Myers – Buhler


Fish feed – fry v/s grow-out feeds

Grow-out feeds 1.5-16 mm

Low specific value

High volume, low production cost

Large diameter, high energy (high fat)

growout diets

> 95% of total production

Fry feeds 0.25-2.0mm

High specific value

Low capacity, labor intense production

Requires fine grinding and prescreening

for micro-pellets

Requires crumbling and sifting for larval

diets

Coating system for attractants, medication

and others

< 5% of total production


Small pellets require fine grinding

0 1.0 mm

Pellets 1000mm

Petfood blend 250-500mmCrumbles 800mm


Larval diets - requirement

Larvae need exact particle sizes

Neutral buoyancy

No dust

required

particle size

500 mm

Example: Sole juvenile,

length approx. 30 mm


Pellets versus crumbles

Crumbles break into random

shapes with l/d ratio within 0.7-1.4

Small pellets < 1mm diam. have

significantly larger size variation

Size variation for pellets depending

on raw material granulation,

extrusion conditions and content of

insoluble matter in formulation

Pellets diameter

0.6mm x 0.7-2.2 mm

long.

Crumbles sized

between 0.63-0.8mm

Raw material

prior to extrusion


Micropellets extrusion with crumbling, sifting

Infeed, Grinding Pre-screening, Extrusion Drying, Cooling Crumbling, sifting

Aquatic feeds –

shape, texture


Chad Myers – Buhler


Pellet texture and fat absorption

spherical porosity, sealed surfaces linear cavities, open porosity


Influence of die shape and material - observations

Temperature, moisture and protein content

has major influence over texture and shape

of pellets.

Conical holes favor spherical expansion

PEEK inserts favor cylindrical pellets

Staggered holes with an abrupt diameter

change help to improve the formation of a

stronger texture

The combination of material and hole shape

allows to improve texture, shape and fat

absorption.

PEEK


Influence of die hole shape

Sharp hole improves texturization

of pellets

Die pressure with rectangular cut

is slightly higher

Pellets are tendencially more

cylindrical


Influence of oil addition on surface after coating

sample 151107_1710, no

oil addition, 408 g/l

sample 151107_1720,

3% oil addition, 406 g/l

matt surface

glossy surface

38 | © Bühler |

x

Thank you for your Attention!Chad Myers Customer Service Account Manager

Pasta and Extruded Products…


Documents

Basics of the Food Extrusion Process...EE Extrusion Wear Parts EE Drying - Coating TE Extrusion USD/ton Example specific production costs USD/ton Example: Marine feed plant 40‘000