Food packaging
This article is mainly focused on food packaging, functions of packaging, factors affecting deterioration of food, major types of packaging and types of of packaging materials.
Food packaging
Food packaging is an integral part of food processing operations. Packaging is a means of achieving safe delivery of products in sound condition to the final user at a minimum cost in terms of its protective role, or it is 'a techno-economic function for optimizing the costs of delivering goods while maximizing sales and profits.'
Functions of packaging
• Containment - to hold the contents and keep them secure until they are used
• Protection - against mechanical and environmental hazards encountered during distribution and use
• Communication - to identify the contents and assist in selling the product.
• Machinability – to have improved performance on production lines for high-speed filling, closing, and assembling (example: 1000 packs per minute), without considerable amounts of stoppages
• Convenience – throughout the production, storage, and distribution system without leakages, including easy opening, dispensing, and/ or after-use retail containers for consumers.
The package should:
• retain the food in a convenient form to the customer without any leakages,
• aesthetically pleasing,
• have a functional size and shape,
• possibly act as a dispenser which opens easily and re-closes securely after every use,
• be suitable for easy disposal, recycling, or re-use.
• The package design should also meet the legislative requirements concerning the labeling of foods.
Factors affecting deterioration of food
• The main factors that cause deterioration of foods during storage include:
– light, moisture vapour, oxygen, temperature changes
– Contamination (by microorganisms, insects, or soils)
– Mechanical forces
– pilferage, tampering or adulteration
– Packaging provides a barrier between the food and the environment.
– Controls light transmission, the rate of transfer of heat, moisture, and gases, and movement of microorganisms or insects.
– Should not influence the product
- it should allow smooth, efficient, and economical operation on the production line, resistance to mechanical damages such as fractures, tears caused by filling and capping equipment, loading/ unloading or transportation, and minimum total cost.
Light
• Light transmission is desirable in packages that are intended to display the contents but is restricted when foods is susceptible to get deteriorated by light (example: oxidation of lipids, destruction of light-sensitive vitamins and natural pigments).
• Pigments may be incorporated into glass containers (amber colour bottles) or polymer films
• Alternatively, clear packs may be contained in fiberboard boxes for distribution and storage.
Heat
•The insulating effect of a package depends on its thermal conductivity and reflectivity.
•Materials that have low thermal conductivity (example: paperboard, polystyrene) reduce conductive heat transfer, and
•reflective materials (example: aluminum foil) reflect radiant heat.
•In specific applications where the package is heated (example: in-pack sterilization), the packaging material must be able to withstand the processing conditions without any damage and interactions with the food.
Moisture
•Moisture uptake or loss is one of the most significant factors that control the shelf life of foods.
•There is a micro-climate developed within a package, particularly in the headspace, determined by the water vapour pressure of the food at the temperature of storage and the permeability of the packaging.
•Control of moisture exchange is necessary to prevent microbiological, enzymatic deterioration, drying out (moisture loss), or softening of the food (moisture uptake), leading to condensation occurring within the packages and resulting mould growth (example: fresh vegetables, bread)
•Foods with low equilibrium relative humidity, such as dehydrated food, biscuits, and snack foods, require packaging that has good barrier properties to moisture to prevent moisture uptake from the environment and loss of their crispness.
•If the water activity rises above a level that permits microbial growth, the food gets spoiled.
•Similarly, foods with elevated amounts of lipids or other components sensitive to oxygen are spoiled if the package has inadequate barrier properties against oxygen.
•Fresh food that are respiring and have a high equilibrium relative humidity require a packaging material that allows the exchange of oxygen and carbon dioxide developed under controlled humidity.
•Packaging should be sufficiently impermeable to retain characteristic odours (example: coffee).
•odour pick up from the plasticizers, printing inks, adhesives, or solvents used to manufacture the packaging material should be negligible.
•Glass and metal packaging are almost totally impermeable to gases and vapours.
Plastic films have a range of permeabilities, depending on the thickness, chemical composition, structure, and orientation of molecules in the film.
Microorganisms, insects, animals, and soils
•Metal, glass and polymer packaging materials are barriers to microbes, but their seals are potential sources of contamination.
•Packs folded, stapled, or twist wrapped are not truly sealed.
Causes of microbial contamination
– Contaminated air or water is drawn through pinholes in hermetically sealed containers as the headspace vacuum forms
– Inadequate heat seals in polymer films caused by contamination of the seal with product or faulty heat sealer settings
– Poorly sealed lids or caps
Mechanical damages
•The suitability of a package to protect foods from physical damages depends on its ability to withstand crushing, abrasion, impact, and shear forces caused during handling.
•Some foods (example: eggs, fresh fruits, biscuits) are easily damaged and require a higher level of protection from a package (example: egg cartons, fruit trays).
•For other foods, protection can be provided by a rigid container and/ or restricted movement by shrink-wrapping, stretch-wrapping, or by using plastic packages that are tightly formed around the product
Two major categories of packaging
Packaging can be categorized into two main types:
1. Shipping containers - which contain and protect the contents during transportation and distribution but have no marketing function.
The requirements of shipping containers are to:
• contain products efficiently throughout the journey
• protect against the climate and contamination
• be compatible with the product
• be easily and efficiently filled and sealed
• be easily handled
2. Retail containers/ consumer units) - which protects and advertises the food in convenient quantities for retail sale and home storage
Types of packaging materials
Wood
Wooden shipping containers are traditionally used for a range of solid and liquid foods, including fruits, vegetables, tea, wines, spirits, and beers.
– good mechanical protection, good stacking characteristics, and a high vertical compression strength-to-weight ratio.
Metal
•Metal cans are hermetically sealed.
•Metal cans have advantages over other types of containers in that they can withstand high-temperature processing
•they are impermeable to light, moisture, odours, and microorganisms to provide total protection to the contents
•they are inherently tamperproof
•recyclable
•the high cost of metal and relatively high manufacturing costs make cans expensive.
•heavier than other materials, except glass, hence involves higher transport costs.
•made from mild steel. Tin is applied by electroplating to a different thickness of tin coatings on each side of the steel.
•The tin may be coated with the lacquers to prevent interactions with foods
Aluminum packaging
•In addition to its use in can-making, aluminum is used for foil wrappers, lids, cups and trays, laminated pouches, collapsible tubes, barrels, and closures.
•The advantages of foil include:
– Good appearance
– Odourless and tasteless
– Good dead-folding properties
– The ability to reflect radiant energy
– An excellent barrier to moisture and gases
– Good weight: strength ratio
– Impermeable to light, moisture, odours, and microorganisms
– High-quality surface for decorating or printing
Glass
•the main constituents are silica (99%), broken glass or 'cullet' (15–30% of total weight), soda ash, and limestone to a temperature of 1350–1600ºC.
•The molten glass is shaped in a mould by the blow-and-blow processor the press-and blow process
•Glass containers have the following advantages:
– they are impermeable to moisture, gases, odours, and microorganisms
– they are inert and do not react with or migrate into food products
– they are suitable for heat processing when hermetically sealed
– see through
– they are reusable and recyclable
Disadvantages of glass containers:
heavy
since they are transparent, light passes through
Flexible films
• By altering the film thickness, the orientation of polymer molecules, amount and type of additives, and type and thickness of coatings, the mechanical, optical, thermal, and barrier properties are produced for each type of polymer.
•Films may be used singly, coated with polymer or aluminum, or produced as multi-layered laminates or co-extrusions.
•Plastic is added to soften the film and to make it more flexible, especially for use in cold climates or for frozen foods.
•Pigments may be added to avoid the need for large areas of printing.
Paper and board
•The principal differences between paper, paperboard, and fiberboard are thickness and usage.
•Papers are thin, flexible, and used for bags and wraps;
•paperboard is thicker, more rigid, and used to construct single-layer cartons;
•fiberboard is made by combining layers of solid papers and is used to construct secondary shipping cartons.
•The material used to construct shipping cartons is called "corrugated paperboard" because of the wavy inner layer of paper board used in its construction.
•Kraft paper is the strongest of papers and is commonly used for grocery bags. If bleached and coated, it is commonly used as butcher wrap.
•Acid treatment of paper pulp modifies the cellulose and gives rise to water-and oil-resistant parchments of considerable wet strength.
•These papers are called greaseproof or glassine papers and are characterized by long wood pulp fibers which impart increased physical strength.
•Many papers are treated with wax
–Wax provides a moisture barrier and allows the paper to be heat sealed.
–the simple wax coating is easily damaged by folding or by abrasive foods, but this is overcome by laminating the wax between layers of paper and/ or polyethylene.
–Waxed papers are used for bread wrappers and inner liners for cereal cartons.
•White board is acceptable for contact with food and is often coated with polyethylene or wax for heat sealability.
•used for ice cream, chocolate, and frozen food cartons
•Chip board is made from recycled paper and is not generally used in contact with foods. (example: as the outer cartons for tea and cereals).
•It is often lined with the white board to improve the appearance and mechanical strength
•Fiber board (> 0.11mm) is either solid or corrugated. The solid type has an outer kraft layer and an inner bleached board.
•It can withstand compression and impact forces considerably.
•Aseptic packaging for packaging aseptically sterilized (UHT) foods.
Conclusion
References
Food Processing Technology: Principles and Practice, Second Edition.
PRINCIPLES OF FOOD PACKAGING. https://habib-ahmad.wixsite.com/foodscience/post/principles-of-food-packaging
https://www.studocu.com/in/document/university-of-mumbai/microbiology-immunology-and-plant-physiology/chapter-packaging/3636299
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