Synthetic sausage casings

transcript

Ted Brink

Contents

• types of casings

• synthetic casings

- materials

- production process

- mono and multilayer

- requirements

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

Types of sausage casings

natural animal

polymer cellulose

collagen

Why plastic casings?

• price

• barrier properties

• mechanical strength

Production of plastic casings

• always blown film

• can be stretched biaxial (double/triple bubble process)

• monolayer

• multilayer

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

Monolayer synthetic casings

Materials used:

• polythylenes

• polyamides

- PA66

- PA6.66

- PA11

- PA12

Polyethylene in sausage casings

• no adhesion with meat

• applied mainly for frozen minced meat

• high layer thickness: between 100 and 250 μm

Multilayer casings - materials

• polyethylenes

• polypropylenes

• polyamides

- PA6.66

- amorphous

• EVOH

• PVDC

• ionomers

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

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

The double bubble process

Heat setting

determines

shrinkage %

Main machine producers:

• Kuhne

• Plamex

Casings production plant

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

Post treatment

• printing

• shirring

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

180 *)

250 *)

E-modulus GPa 100-300 1500-3000 1000-20002000

4500 *)

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

Polyamide in sausage casings

Strong points of polyamide:

• strength

• stiffness

• oxygen barrier

• thermal resistance

• protein adhesion

• stretchability

• easy to process

Moisture absorption of polyamides

23 °C/50 % RH

23 °C in water

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

Additives

• pigments and colourants

• nucleating agents (unoriented casings)

• heat stabilizers

• UV-absorbers

• antimicrobial agents

Multitude of colours used for casings

Structures of commercially available casings

0 10 20 30 40 50 60 70

outer layer inner layer

tie tiePE PA

PE + tie 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

Handling of casings

shirred casings

Bon appetit

Contact

Ted Brink

Email: ted.brink@extrusionist.com

Internet: www.extrusionist.com

Tel.: +31 651109899

Synthetic sausage casings

Food