Module 2. Packaging materials

Lesson 14

14.1 Introduction

Retort is a cooking process that uses heat and pressure to cook food in its sealed package. Retort Pouches conditions are quite demanding with temperatures typically ranging from 120°C to 130°C.

14.2 Retort Pouch Processing of Foods
  • Retort processing of foods in rigid, semi-rigid and flexible packaging systems is the most acceptable form of food preservation.
  • It represents unique combination of package, process and product technology with potential economic benefits.
  • Traditionally, tin containers have contributed to a large extent in building the confidence in processed foods.
  • The increasing public awareness and aversion to accept other methods of food preservation like chemical preservation, irradiation, etc. have offered a vast scope for retort processing of foods.
  • Different retort grade films are laminated together to provide the strength, toughness, puncture and burst resistance that enable flexible retort pouches to withstand the strenuous retort process.
  • A number of different virgin, multilayer and co-extruded packaging materials such as polypropylene, nylon (pp/nylon/pp), polyester cast propylene (pet/c.pp) and polyester aluminum foil cast polypropylene (PET/A foil/C.PP) have been evaluated and are in use for their mechanical strength to withstand retort conditions at temperature up to 135°C, optimum oxygen barrier properties, compatibility with the food products and required shelf-life of 12 months under ambient conditions.
  • Retort pouches and packaging are available in two variants one is aluminum foil laminated and another transparent see through retort pouches.
  • When the retortable pouch is heated in a microwave oven, the laminated cover film having the aluminum foil is removed from the laminated base film, whereby microwaves generated by a magnetron are not intercepted, and cooked food packaged in the retortable pouch can be heated adequately.
14.2.1 Characteristics of retort pouches
  • Because Retort pouches have thinner dimensions, it takes less time to cook food in a flexible retort pouch than in other forms of rigid packaging such as cans and jars.This reduced retort time results in foods that have superior taste in retort pouches.
  • Retort Pouch packaging has superior barrier and printing qualities and can be supplied as stand-up, flat or in roll form.
  • Retort pouches are suitable to pack a variety of food products.
  • The laminated material has a high puncture resistance.
  • It offers a variety of styles of retort packaging such as foil based or completely transparent.
  • Flexible retort pouches offer a variety of additional benefits over rigid packaging to both retailers and consumers that include:
1. Superior taste due to reduced retort time

2. Extended shelf life in retort pouches

3. Reduced storage space, both in warehouse and pantries

4. Reduced transportation costs

5. Easier and safer tear-open/disposal consumer experience

6. Microwave convenience

14.2.2 Common structures used for retort processing
  • 1. Retortable pouch and packaging material for the retortable pouch comprises
  • A laminated base film formed by laminating together a polyester film and an inelastic polypropylene film,
  • A laminated cover film formed by laminating together a polyester film and an aluminum foil, and
  • An adhesive layer detachably bonding the polyester film of the laminated base film to the aluminum foil of the laminated cover film, thereby laminately bonding the laminated cover film to the laminated base film.
  • Common flexible retort pouch structures include the following
  • PET / NYLON / CPP,
  • PET / FOIL / Nylon / CPP,
  • PET / Nylon / FOIL / CPP,
  • PET-SiOX or
  • AlOX / Nylon / CPP
  • PET / NY / AL / Retortable CPP: High Retort (Under 125°C), High Barrier (OTR, MVTR) Non-Microwaveable.
  • High temperature sterilization, Excellent sealing capability, Excellent up to 8 colors gravure printing, Lower OTR, WTR and Longer shelf life, Optional laminated layers for better barriers against moisture, humidity, puncturing are the major characteristics.
  • Alox-PET / NY / Retortable CPP: High Retort (Under 125°C), High Barrier (OTR, MVTR) Microwaveable.
  • Microwavable pouch is advanced version of regular retort pouch.
  • It is very convenient to use and microwavable pouch started to replace retort pouch lately.
  • Microwavable pouch does not contain aluminum and barrier comes from special polyester film.
  • It can be used in seafood, stew, meat, curry, rice, and other processed foods.
  • Normally, microwavable pouch is standup pouch because end user wants to put pouch in to the microwave and eat right out of the pouch.
14.3 Retortable Pouches

  • A typical laminate for retortable pouch is 0.0005 polyester / 0.00035 foil / 0.003 polypropylene, with the outer ply designated first as is customary for pouch material.
  • Filled pouches are sterilized at 115-121°C, with overriding air pressure of ~ 2 kg/cm2 to prevent bursting.
  • Pouch material that will not delaminate at these temperatures must be selected, and the seals should withstand a tensile test of 0.08 kg/m of width, internal pressure of 1 kg/cm2 for 30s, pinhole strength of 0.6 kg and a drop test of 1.22 m.

Last modified: Thursday, 11 October 2012, 8:54 AM