To study about different types of packaging material
Packaging materials for fresh fruits and vegetables
The packages for fresh fruits and vegetables can be classified as (1) Consumer/Retail packs and (2) Transport/Bulk packs.
(A) Packing materials used for consumer packs:
Consumer packages are small in size and designed to hold ½ dozen to 1 dozen fruits or ½ to 2 kg of vegetables.
The selection criterion of the packing material for the type of consumer pack depends on the marketing characteristics of the product. The most commonly used packaging materials for consumer packages are:
(1) Flexible plastic films:
Different types of flexible plastic films LDPE (low-density polyethylene), PVC (polyvinyl chloride), PP (polypropylene), and cellulose acetate films are used for packing. These films are mostly used as pouches with holes punched at regular intervals to allow respiration. They are available in a wide range of thicknesses and grades and can be used to control the environmental gases inside the pouch. LDPE is the most widely used material.
(2) Trays with overwrap:
The trays used are usually made of moulded pulp trays or plastic materials like PVC and PP. The produce is placed in individual cavities so that abrasion and bruising are avoided during transportation. The trays also provide cushioning effect to the produce.
The overwrap film is a transparent see-through food-grade, odourless plastic film with the property of clinging to the product packed when stretch wrapped. This film can be applied without the application of heat. This film is usually made of LDPE or PVC. The films are semi-permeable and allow the exchange of gases for the respiration of the product.
(3) Plastic punnets:
These are strong, versatile. clear, bright containers which offer product visibility and are provided with holes for ventilation, which keeps the produce fresh.
These containers are food-grade, odourless, lightweight, stackable, and recyclable and give a good presentation. These are either made of PET (polyethylene terephthalate), PVC, or PP.
(4) Plastic net bags (extruded and oven):
The plastic net bags have the feature to stretch and accommodate all sizes and shapes of produce. These bags are available in roll form or in precut lengths with a stretch width of 200mm – 400mm. By allowing air to circulate in and around the produce; the net bags prolong the freshness and shelf life of the product. These also eliminate pack condensation thereby preventing spoilage and wastage. They make a colourfull point of sale display allowing clear visibility of the contents, enhancing the natural colours of fresh produce. These are generally made of HDPE or PA (polyamide).
(5) Foam sleeve:
This is a plastic tubular film made of polyethylene foam available in different colours, diameters, and lengths. It can be easily slipped over the individual fruits in a snug fit form. It provides a cushioning effect and protects the fresh produce against abrasion and scratches during transport. It is hygienic, non-toxic, and odourless.
(6) Shrink film wraps:
Films such as Polypropelene, polystyrene, Polyethylene, and rubber hydrochloride can be converted into shrink films by molecular orientation methods. After the shrink film is applied to the filled trays or in tubular or heat-sealed wrap form, the packages are sent through a heat tunnel to shrink the film cover. This immobilizes the commodity to reduce the possibility of physical damage during handling.
(B) Transport or bulk packs:
Transport or bulk packages are designed for long-distance transportation in capacities ranging from 4-5 kg to 20-25 kg. These packs must withstand impacts, compression, and vibration during transport.
(1) Natural materials –
Baskets and other traditional containers made from bamboo, rattan, straw, palm leaves, etc., are used throughout the developing world. Both raw materials and labour costs are normally low, and if the containers are well made they can be reused.
- They are difficult to clean when contaminated with decay organisms.
- They lack rigidity and bend out of shape when stacked for long-distance transport.
- They load badly because of their shape.
- They cause pressure damage when tightly filled.
- They often have sharp edges or splinters causing cut and puncture damage.
(2) Wooden boxes/Crates:
The conventional baskets have been replaced by wooden boxes as they give better protection to the fresh produce against transportation hazards. They have high puncture resistance, good tensile strength.
Wooden boxes are rigid and reusable and if made to a standard size, stack well on trucks.
However, the use of wooden boxes is discouraged nowadays as it promotes deforestation.
- They are difficult to clean adequately for multiple uses
- They are heavy and costly to transport
- They often have sharp edges, splinters, and protruding nails requiring some form of the liner to protect the contents.
- The nails cause injuries to the product during long transportation.
- They occupy more space and add on to the tare weight.
(3) Cardboard (fibreboard)/corrugated fibreboard boxes:
Containers are made from solid or corrugated cardboard. The types closing with either fold over or telescopic (separate) tops are called boxes or cases. Shallower and open-topped ones are called trays. Boxes are supplied in collapsed fore that is flat and are set up by the user. The setting up and closing of boxes require tapping, gluing, stapling, or fixing interlocking tabs.
Are used for tomato, cucumber, and ginger transport. They are easy to handle, lightweight, come in different sizes, designs, and strengths, and come in a variety of colours that can make products more attractive to consumers. These have good cushioning properties, low cost to strength and weight ratio. These are reusable and recyclable, easy to set up and collapsible for storage, smooth and non-abrasive surface with good printability on the outer surface of the board.
Ventilation can be provided by punching holes and have good printability on the outer surface of the board.
Since these boxes have poor wet strength, nowadays they are laminated with a plastic film like LDPE, PP, or PVC. Plastic corrugated boxes made of PP and DPE are partly replacing CFB boxes because of their low weight to strength ratio, high degree of water resistance, and reusability. However, its cushioning properties are not comparable to CFB boxes
- They may if used only once, prove an expensive recurring cost.
- They are easily damaged by careless handling and stacking
- They are seriously weakened if exposed to moisture
- These boxes are often of lower strength compared to wooden or plastic crates, although multiple thickness trays are very widely used.
- They can be ordered economically only in large qualities; small quantities can be prohibitively expensive.
(4) Moulded plastic crates:
Re-usable boxes moulded from high-density polythene are widely used for transporting produce. They can be made to almost any specification. They are strong, rigid, smooth, easily cleaned, and can be made to stack when full of produce and nest when empty in order to conserve space.
- They can be produced economically only in large numbers but are still costly.
- They have to be imported into most developing countries, adding to the cost and usually requiring foreign currency for their acquisition
- They often have many alternative uses (as washtubs) and are subject to high pilferage rates.
- They require a tight organization and control for use in a regular go and return service
- They deteriorate rapidly when exposed to sunlight (especially in the tropics) unless treated with an ultraviolet inhibitor, a factor adding to the cost.
Despite their cost, however, their capacity for reuse can make them an economical investment.
These crates are either stackable, stack nest, or collapsible in design.
Collapsible plastic crates are the most expensive followed by stack nest and then the stacking crates. The collapsible crates reduce the storage space requirement and transport cost of empty containers. The normal capacity varies between 20-40kg.
(5) Natural and synthetic fibres:
Sacks or bags for fresh produce can be made from natural fibres like jute or sisal or from synthetic polypropylene or polyethylene fibres or tapes. ‘Bags’ usually refers to small containers of up to about 5 kg capacity. They may be woven to a close texture or made in the net form. Nets usually have a capacity of about 15kg. Bags or sacks are mostly used for less easily damaged produce such as potatoes, sweet potatoes, onions, but even these crops should have careful handling to prevent injury.
These are very useful because of their low cost, high strength, re-usability and require less space for empties.
- They lack rigidity and handling can damage contents
- They are often too large for careful handling; sacks dropped or thrown will result in severe damage to the contents
- They impair ventilation when stacked if they are finely woven
- They may be so smooth in texture that stacks are unstable and collapse; they are difficult to stack on pallets.
(6) Paper or plastic film:
Paper or plastic film is often used to line packing boxes in order to reduce water loss of the contents or to prevent friction damage.
Paper sacks can have walls up to six layers of Kraft (heavy wrapping) paper. They can have a capacity of about 25 kg and are mostly used for the produce of relatively low value. Closure can be done by machine stitching across the top (recommended for large-scale crop production) or in the field by twisting wire ties around the top by means of a simple tool.
- Walls of paper are permeable by water or vapour and gases (walls may be waterproofed by incorporating plastic film or foil, but sacks then retain gases and vapour)
- Heat can be slow to disperse from sacks of stacked produce, thus damaging the fruit or leafy vegetables.
- Limited protection to contents if sacks are mishandled.
- Plastic film bags or wraps are used because of their low cost, widely used in fruit and vegetable marketing, especially in consumer packs.