Packaging of Fish and Fishery Products
T. K. Srinivasa Gopal
India is predominantly dependent on its agricultural economy, often leading to severe shortages. One of the important causes of food shortage is high postharvest losses and spoilage, estimated to be around 20%. Packaging of foods becomes all the more important in countries such as India where the climatic conditions vary considerably. Ambient temperature varies from subzero to over 50°C and relative humidity from 10-90%. Handling and transport facilities are also seen as grossly inadequate in countries such as India. Unlike many other manufactured consumer products including leather, machineries and chemicals, the packaging needs of foods, and particularly fish, are very complex because of the intrinsic characteristics and the need to retain or preserve them while in the package.
Packaging Requirements of Individual Seafood Products
Battered and breaded seafood products
A number of value-added marine products both for export and internal markets are prepared from shrimp, squids, cuttle fish, certain species of fish and minced meat from low-priced fish (Figure 1). The changes taking place during frozen storage of the value added products include desiccation, discoloration and development of rancidity. Conventional packaging materials such as flexible plastic films alone are not suitable for these products as they provide little mechanical protection to the products and as a result the products get damaged or broken during handling and transportation. Hence, thermoformed containers are commonly used: polyvinyl chloride (PVC), high impact polystyrene (HIPS) and HDPE are unaffected by the low temperature of frozen storage and provide protection to the contents against desiccation and oxidation during prolonged storage.
Frozen shrimp is the most important marine export of India. Conventionally shrimp was frozen as 2 kg blocks in duplex board cartons lined with low density polyethylene (LDPE) and 10 such cartons are packed in a master carton made of 5 ply or 7 ply corrugated fibre board boxes. There is now great demand from importing countries for shrimp in individually quick frozen (IQF) form (Figure 2). IQF shrimp is packed into plastic film pouches. The other major IQF products are cooked whole lobster, lobster tail, lobster meat, cuttle fish fillets, boiled clam meat and fish fillets from white lean fish.
Dried fishery products
One fifth of India’s fish catch is salted and dried for internal consumption. Baskets improvised with braided coconut or palmirah leaves are the containers mainly used for packaging this product both for export and internal distribution. An overwrap with gunny fabric is given as reinforcement in the case of products meant for export and those which have to be transported over long distances. These packages are however prone to easy entry of insects, rodents and other pests. As the product is highly sensitive to changes in relative humidity, the packaging has to be sufficiently water vapour proof.
The commonly used packaging materials for consumer packs of dry fish are LDPE or polypropylene (PP). These materials are cheap, readily available and have good tearing and bursting strength. Disadvantages are high water vapour and gas transmission rates, proneness to puncture or damage from sharp spines and odour problems, and hence shelf life is limited. A recent development is the use of polyethylene terephthalate (PET)/LDPE laminate pouches (Srinivasa Gopal et al. 1998).
In India tinplate cans with a sulfur-resistant lacquer are the traditional containers for fish and shellfish. However, the high cost of imported tinplate was one of the reasons for the collapse of canned fish exports from India. Aluminium containers offer tremendous opportunities to take care of the packaging needs of food-based products such as canned fish. An indigenously developed aluminium can has been found quite good for heat processing fish and fish-based products (Balachandran et al. 1998). Pull-tab polymer-coated tin-free steel cans are presently manufactured in India and some canneries use them for both internal and export markets.
Freeze dried products
Application of freeze drying in fish preservation is a relatively recent development. In spite of the high production costs, the process is becoming very popular due to several advantages associated with the products. They are generally packed under an inert gas to exclude air and oxygen. Hence the main requirements in the packaging are low oxygen and water vapour permeability to protect the product from rancidity and absorption of moisture, and sufficient mechanical strength to protect from shock. Paper/ aluminium foil /LDPE laminates or metallised PET/LDPE laminated pouches are used for freeze dried products.
Fish curry is a processed item presented in a ‘ready-to-serve’ style. It can be preserved both by freezing and heat processing. When heat processed in conventional tinplate or aluminium cans the problems encountered are development of a metallic taste and discoloration. Conventional flexible films are not suitable packaging for this product as they provide little mechanical protection and are sensitive to heat. Thermoformed trays made of HIPS or PVC are ideal for packing frozen fish curry (Srinivasa Gopal et al. 1995). Thermally processed fish curry products are packed in PET/aluminium foil/cast PP retortable pouches.
Fish soup powder
Fish soup powder is a speciality product containing partially-hydrolysed fish, protein, carbohydrates, fat and several seasonings including salt. An appropriate package developed for such products is 12 µm plain PET laminated with LDPE-HDPE co-extruded film or 90-100 µm LDPE/LLDPE/Nylon/LLDPE/Primacor (where Primacor = ethylene – acrylic acid co-polymer) multilayer film which ensures safe storage of the product up to 180 days (Srinivasa Gopal and Ravishankar 2001).
Dry fish pickle
Although fish such as anchovies (Kowala coval) are generally dried and marketed, they offer a very good raw material for processing into dry pickle which is considered a value-added product. A packaging material which offers safe storage of the product up to 14 months at ambient temperature has been identified as nylon/Surlyn or LDPE/LLDPE/nylon/LLDPE/Primacor (Prabhu and Srinivasa Gopal 1990).
Chitin / chitosan
Until recently posing a very serious problem in its disposal, shrimp waste has now become a very valuable commodity because of its use in the manufacture of chitin and chitosan derived from chitin. Chitin and chitosan are exported commodities and appropriate packaging should protect the product against moisture gain as well as microbial and insect attacks. The packaging extensively being used by the industry is a HDPE woven gusseted bag laminated with 100 gauge LDPE liner (Figure 3).
Figure 3: Chitin packed in HDPE laminated woven sack with LDPE liner
References and Additional Reading
Balachandran, KK, Srinivasa Gopal, TK and Vijayan, PK (1998) Aluminium containers in fish canning. In Aluminium in Food Packaging. Bombay : Indian Institute of Packaging; 571-574.
Prabhu, PV and Srinivasa Gopal, TK (1990) Storage life of dry fish pickle from white sardines (Kowala coval) packed in synthetic flexible pouches. In Proceedings of the Second Indian Fisheries Forum, Asian Fisheries Society. Mangalore: Indian Branch; 309-312.
Srinivasa Gopal, TK and Ravishankar, CN (2001) Packaging of value added fish products. Indian Food Ind. 20(3): 64-67.
Srinivasa Gopal, TK, Joseph, AC, Iyer, TSG and Prabhu, PV (1995) Thermoformed containers for packaging and frozen storage of seer fish (Scomberomorus guttatus ) curry. Fishery Technol. 32(1): 30-33.
Srinivasa Gopal, TK, Nair, PGV, Kandoran, MK, Prabhu, PV and Gopakumar, K (1998) Shelf life of dried anchoviella in flexible packaging materials. Food Control 9(3): 1-5.
Dr T. K. Srinivasa Gopal is a Principal Scientist and Head, Fish Processing Division, Central Institute for Fisheries Technology (CIFT), Cochin 682 029, India; E-mail: firstname.lastname@example.org