The previous section discussed the processing methods most often used by small freshwater fish processing plants. Quality assurance is essential in each technological process, and suitable packaging materials and methods are of great importance. If these requirements are not met all efforts made during processing could be of little avail, which could lead to serious economic losses.
Packaging should protect the product from contamination and prevent it from spoilage, and at the same time it should:
- extend shelf life of a product
- facilitate distribution and display
- give the product greater consumer appeal
- facilitate the display of information on the product
The quality of freshwater fish which is delivered to the consumer or the processing plant as live fish greatly depends on correct handling during transport and, when processed, on suitable packaging. For short distances, the live fish can be transported in insulated containers with lids, capacity varying from 300 to 1 000 kg of fish. Fish can also be transported in normal lorries, but for long distances the water in the containers must be aerated and cooled by portable devices.
In order to maintain good quality of fresh fish during transportation, fish boxes made of suitable materials should be used. When purchasing fish boxes the six following requirements should be remembered; they should:
- be of a suitable size for the range of fish to be handled or the product to be put into them
- be of a convenient size for manual handling or lifting by mechanical equipment
- be stackable such that the weight of the containers on top rests on the containers underneath and not on the fish
- be constructed of impervious non-staining materials
- be easy to clean
- provide drainage for melted ice
Fish boxes are usually made of high-density polyethylene. Although this offers many advantages, such as duration, lightness, ease of cleaning, there are also disadvantages, e.g., high price and the fact that they are not returnable. That is why disposable fish boxes of about 25 kg capacity (fish and ice) are more often used: these include fibreboard cartons, waxed and waterproof boxes. In the case of transport by lorries with no cooling system, insulated cartons, e.g., boards made of moulded polyestyrene should be preferred. The latter is commonly used for delivery of chilled and frozen fish and fish products to wholesale and retail outlets. In the case of fillets, each layer of fillets should be packed thin and separated from the ice with a plastic foil.
Styropor boxes are normally sold with lids, which fit very closely and can be with or without drainage holes. In a typical range, wall thickness varies with box size; e.g., a 6 kg capacity box has a 15 mm thick wall, a 10 kg box a 19 mm wall, a 25 kg box a 25 mm wall. The main disadvantage of moulded polyestyrene fish boxes is their lack of strength. They are easily damaged or broken by rough handling. This limits their size and use.
Polyestyrene is difficult to clean. Polyestyrene boxes are difficult to re-use, and are usually non-returnable. They may cause disposal problems due to their bulk.
The packaging industry improves its products by using new materials with better insulating properties or by introducing new leakproof designs. The new containers are often lighter and less bulky. For example, the Therma Gard packing system consists of a metallized plastic bag (which reflects practically all radiant heat). This is then wrapped in a waterproof and leakproof carton. The metallized bag, together with a bubble-pack wrapper, provides a double-pack insulation. The Therma Gard bag can be sealed airtight and thus be used for carrying live fish. The Stratech aluminized boxes have a wall thickness of only 5mm and it is claimed that these boxes have similar insulating characteristics as polystyrene boxes with 30 mm wall thickness.
The future use of expendable packages is becoming questionable as there is a growing discussion, for example in some states of the USA, on imposing a ban on these packages.
The main drawbacks in using returnable containers are freight costs for returning empty containers. Use of "knock-down" returnable containers will reduce freight costs.
The main role of packaging is described above but in respect of retail presentation it should also reduce the smell and the drip, and enable the product to be tucked into shopping baskets with other purchases. Moreover, the packaging of fish products should ensure attractive presentation among other food products without contaminating them.
Basic packaging materials include paper, cartons, sheets of metal, metal foils and many kinds of plastics. Despite the rapid growth in use of plastics, the role of paper and carton as packaging materials does not decrease.
Kraft paper or carton are often laminated with polyethylene or aluminium foil which render them waterproof. Such material is used for production of trays for packaging of fresh or frozen products. More often, trays are made of plastic materials such as polyestyrene or expanded polyestyrene. Expanded polyestyrene is frequently used but it is partly oxygen-permeable and so those products which are sensitive to rancidity have to be additionally overwrapped or skin-packed with suitable film.
The materials mentioned above are not stable at high temperatures and hence are not suitable for trays to be used in an oven. Polyester can be used as a packing material for heating of the product in the traditional and microwave ovens, but this material cannot be used for microwave cooking.
Trays used for packing are generally overwrapped with a protective film, often with PE wrapping which shrinks. The film shrinking is achieved by use of hot air or hot water.
Stretch wrapping is often used for products which are heat-sensitive. The film is stretched over the product manually (very often in the supermarket) or by machine. Foils used as wrapping or bags for packing of trays with product must be puncture-proof, extensible and impervious to gases like oxygen.
Hundreds of different films are used in the packaging industry. These can be broadly categorized into two groups:
- basic films consisting of a single layer of film
- laminate consisting of two or more basic films glued together or bonded together by heat or by adhesives
Plastics such as polyethylene film or copolymer of ethylene and vinyl acetate are very often used for packing of frozen products. Polyethylene packs can be produced manually using pre-made bags. An impulse or bar sealer is used to seal the bags which are hand-filled.
In order to improve the barrier properties of packages laminates are used, for example polyester/polythene. Products which are particularly sensitive to oxygen are vacuum-packed. During the sealing operation, air is removed from the package. A laminate nylon/polythene is commonly used as packaging material. This type of packaging is used, for instance, for smoked trout which are arranged on a board with, for example, a coated texture. Numerous machines exist for vacuum-packing with single, double or continuous chambers. Vacuum-sealing machines can additionally be equipped with a modified atmosphere packing system (MAP). Immediately on removing the air from the package a mixture of gases is pumped in. Usually this mixture consists of 30% nitrogen, 40% carbon dioxide, and 30% oxygen. In the case of fat fish the oxygen is replaced by nitrogen. This method is increasingly used for packing fresh fish. The MAP products have to be stored at the temperatures lower than 3° C because of C. botulinum hazard. MAP packages consist of two kinds of foil. The bottom film is foil-rigid or semi-rigid. This foil is formed by, for example, extrusion and the resultant tray is moved to the packing section. Because of product drip it is placed on an absorbing board. The top web is drawn over the filled trays and sealed round the edges. The pack may be evacuated or gas-flushed before sealing.
Vacuum-skin packaging is becoming more common for packing smoked fish. In this process the wrapper is heated and wrapped over the product, the film moulding completely to the product shape and sealing the product completely, forming an extra skin.
5.3 Labelling Requirements for Freshwater Fish Products
Lack of detailed standards and existence of only limited regulations concerning wholesomeness and sanitary conditions for production and trade of food products characterize the market economy. Here, the problem of labelling is of a particular importance. Regulations in this regard are very detailed and are aimed at protecting the health of the consumer and providing the best information. These requirements enable the consumer to decide which products to buy. A label placed on the product should inform the consumer about the raw material used, method of preparation and form of consumption, shelf life, etc.
Product labelling is of prime concern in the European Union. Directive 79/112/EEC of 18 December 1978 was revised several times, and in 1990 there came into force a new Directive 90/496/EEC which concerned labelling and providing information on nutritive and energetic values (kcal or kJ/100 g or 100 ml), the amount of basic ingredients and nutritive compounds such as: proteins, carbohydrates, fat, fibre, sodium and vitamin content (EEC, 1979). These requirements were supplemented in Directive 89/396/EEC recommending the labelling of batches of product which would make it easier to withdraw the batch from commodity turnover in the case of health hazard.
Taking into account the necessity to ensure complete information on the product to facilitate the selection of a healthy and economic diet, the US Food and Drug Administration (FDA) recently proposed a voluntary Nutritive Labelling Programme which covers, inter alia, a proposal for placing on the product for example information concerning the percentage of recommended daily intake of protein, vitamin A and C, iron, calcium, etc.