synthetic sausage casings
TRANSCRIPT
Synthetic sausage casings
Ted Brink
Page 2
Contents
• types of casings
• synthetic casings
- materials
- production process
- mono and multilayer
- requirements
Page 3
Page 4
Types of sausage casings
• animal casings- for traditional casings, edible
• collagen casings- made from gelatinous substances of bones, cartilage and connective
tissue of mammals, edible
• cellulose casings- made from solubilized cotton
• fibrous casings- from paper and viscose
• polymer casings- polyolefins and polyamides
Page 5
Types of sausage casings
natural animal
polymer cellulose
collagen
Page 6
Why plastic casings?
• price
• barrier properties
• mechanical strength
Page 7
Production of plastic casings
• always blown film
• can be stretched biaxial (double/triple bubble process)
• monolayer
• multilayer
Page 8
Requirements of synthetic casings
• barrier properties
• oxygen
• moisture
• flavour
• microbiological
• mechanical properties
• puncture resistance
• tear strength
• defined shrinkability
• retortability
• meat (protein) adhesion
• printability
• food contact approved
Page 9
Monolayer synthetic casings
Materials used:
• polythylenes
• polyamides
- PA6
- PA66
- PA6.66
- PA11
- PA12
Page 10
Polyethylene in sausage casings
• no adhesion with meat
• applied mainly for frozen minced meat
• high layer thickness: between 100 and 250 μm
Page 11
Multilayer casings - materials
• polyethylenes
• polypropylenes
• polyamides
- PA6
- PA6.66
- amorphous
• EVOH
• PVDC
• ionomers
Page 12
Multilayer casings
• process: double bubble stretched casings
• typical 5 layers
• blends are common
Example12 μm PA6/PA6.66
3 μm tie resin
10 μm LDPE
3 μm tie resin
25 μm PA6/AmPA
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Coextrusion
• requires rheology match of individual polymers
- viscosity
- elasticity
• mismatch of rheology may result in:
- optical defects
• rheology match in practice often trial-and-error
- MFI used for polyolefins
- RSV or VN used for engineering plastics
Page 14
The double bubble process
Heat setting
determines
shrinkage %
Main machine producers:
• Kuhne
• Plamex
Page 15
Casings production plant
Page 16
Effects of orientation of PA-based casings
property not oriented oriented
tear strength ++ +
tensile strength + +++
modulus + +++
oxygen barrier + ++
cooking of sausages in molds in hanging position
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Post treatment
• printing
• shirring
Page 18
Polymer properties
property unit PE PP EVOH PET PA6
melting
point°C 100-140 150-165 176 260 220
tensile
strengthMPa 25-35 30-40 25
100
180 *)
85
250 *)
E-modulus GPa 100-300 1500-3000 1000-20002000
4500 *)
1500
3000 *)
strain at
break% 500-800 250-600 150 250-600 300-500
H2O g/m2 d 0.5-5 1-5 50 15 40
O2 ml/m2 d bar 4000 2500 3-10 160 80
*) oriented
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Polyamide in sausage casings
Strong points of polyamide:
• strength
• stiffness
• oxygen barrier
• thermal resistance
• protein adhesion
• stretchability
• easy to process
Page 20
Moisture absorption of polyamides
0
2
4
6
8
10
12
mois
ture
abso
rpti
on [
%]
23 °C/50 % RH
23 °C in water
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Polymer blends are common
• PA6 with ionomer
- improvement of water barrier
- fine-tuning of meat adhesion
• PA6 with amorphous polyamide
- improvement of transparency
- improvement of oxygen barrier
- improvement of UV barrier
• PA6 with Arnitel
- improvement of smoke permeation
Page 22
Additives
• pigments and colourants
• nucleating agents (unoriented casings)
• heat stabilizers
• UV-absorbers
• antimicrobial agents
Multitude of colours used for casings
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Structures of commercially available casings
0 10 20 30 40 50 60 70
G
F
E
D
C
B
A
outer layer inner layer
PA
PA
PA
PA
PA
PA
PA
tie tiePE PA
PE + tie PA
IOIO
+ PA
EVOH tie PP PA
PP + tie PA
thickness in micron
PA polyamide
tie adhesive
PP polypropylene
IO ionomer
EVOH ethylene vinyl
alcohol
PE polyethylene
Page 24
Handling of casings
shirred casings
Page 25
Bon appetit
Page 26
Contact
Ted Brink
Email: [email protected]
Internet: www.extrusionist.com
Tel.: +31 651109899