Food Packaging Technology 3(2+1)

Lesson- 19 Advantages of different packaging materials

19.1 Retortable pouches

The pouches, trays, and tubs are always multilayer laminate structures that contain different polymers which provide heat resistance, strength, and toughness (PET), pierce and pinhole resistance (nylon), oxygen barrier (EVOH, nylon or PVDC) and (for the pouches and trays) heat sealability (PP). An aluminum foil layer often serves as the moisture and oxygen barrier in pouches. The retortable paperboard cartons have external and internal PP layers that are impermeable to liquid and allow heat sealing, along with an internal aluminum layer that provides a gas and light barrier.

19.1.1 Advantages of retortable pouches

• less energy is required to manufacture pouches compared with cans

• transport of empty containers is cheaper (85% less space required than cans)

• packaging is cheaper than equivalent can and with carton cost is about the same

• filling lines are easily changed to a different size

• rapid heat penetration and faster process results in better nutrition/flavour

• contents are ambient shelf stable – no refrigeration is required

• packed pouch is more compact requiring about 10% less shelf space

• less brine or syrup used, pouches are lower in mass and cheaper to transport

• fast reheating of contents by immersion of pack in hot water. No pots to clean

• opens easily by tearing or cutting

• ideal for single portion packaging and serving size control

• retort pouch materials are non-corrosive

• convenient for outdoor leisure and military rations use.

19.2. Glass

 Glass is made by mixing several naturally-occurring inorganic compounds at a temperature above their melting points. The molten mixture is then cooled to produce a noncrystalline, amorphous solid. The main ingredient is silica (sand) (SiO2) that serves as the network-forming backbone of the glass. However, silica has a very high melting temperature, and molten silica has high viscosity that makes it difficult to form into shapes. Adding soda (Na₂O) modifies the silica network by disrupting some of the Si-O bonds, with resulting lower melting temperature and viscosity but reduced resistance to dissolving in water. Thus, lime (CaO) is added as a network stabilizer, with the result that durability is increased but tendency to crystallize is also increased. Finally, alumina (Al₂O₃) is added as an intermediate to resist crystallization. Minor amounts of colorants are added to produce colored glass, including chromium oxide for green, cobalt oxide for blue, nickel oxide for violet, selenium for red, and iron plus sulfur and carbon for amber. Amber provides the best protection for light-sensitive foods and beverages, transmitting very little light with wavelength shorter than 450 nm.

 19.2.1. Advantages of Glass

• Inert

• Total barrier to

• Gas

• Water vapor

• Aroma

• Good compression resistance

• Good heat resistance

• Allow viewing of product

• Microwavable

• Customer perception of high quality

• Reclosable

• Recyclable

• Refillable

 19.3. Metals

Like glass, steel and aluminum are total barriers to gases, water vapor and aromas. Both also have good heat resistance and can withstand physical and thermal shock. Because of steel’s greater strength, it is used more often in the thermal processing of foods. Neither steel nor aluminum is as inert as glass; thus both must be coated to avoid interactions with the foods they contain. Tin or chromium is used to coat steel, usually followed by a coating with a polymeric lacquer (enamel). Aluminum is coated directly with a lacquer. Other advantages of metal containers are exclusion of light from food products that are light-sensitive and their recyclability.

19.3.1 Advantages of Metal Containers

• Total barrier to

• Gas

• Water vapor

• Aroma

• Good compression resistance

• Good heat resistance

• Good thermal and physical shock resistance

• Light protection

• Recyclable

 19.4. Plastic

The most commonly used thermoplastic polymers are inexpensive, and their conversion into food packaging is also relatively inexpensive. These plastics can be molded or extruded into a wide range of flexible, semi-rigid and rigid containers

that are lightweight, noncorrodible, shock-resistant, and heat-sealable. Most are transparent and some are microwaveable. Certain plastics have high enough heat resistance that they can be hot-filled, retorted and/or used in a conventional oven. Finally, the most commonly used plastic semi-rigid and rigid containers are recyclable. Similar to glass and metal, plastic properties have improved over the years so that less material is necessary for making containers with acceptable integrity.

19.4.1 Advantages of plastics

• Inexpensive materials

• Inexpensive conversion to packaging

• Versatile

• Flexible

• Rigid

• Semi-rigid

• Moldable

• Light-weight

• Noncorrodible

• Shock-resistant

• Heat-sealable

• Transparent

• Can be pigmented

• Microwavable (some)

• Good heat resistance (some)

• Recyclable (some)

 19.5. Paper

Paper is a quite versatile material, utilized in flexible, semi-rigid, and rigid packaging. It is made into a wide variety of single- and multi-wall bags. It can also be made into a thicker stronger structure (>0.012 in. /0.03 cm) called paperboard (Pb), which is made into cartons and boxes that provide mechanical protection for many foods. The paperboard can be converted to an even stronger material called corrugated paperboard that is converted into boxes used for logistics (tertiary and quaternary packaging). Most types of paper provide a partial or complete barrier to light. It can also be manufactured into transparent and clear materials. The starting material of paper, wood, is a renewable resource, and paper is recyclable and biodegradable.

19.5.1 Advantages of Paper Packaging

• Versatile

• Rigid          

• Semi-rigid

• Flexible

• Mechanical protection

• Logistics functions

• Barrier to light

• Renewable resource

• Recyclable

• Biodegradable