Biomedical Engineering Reference
In-Depth Information
1. Introduction
Fishery has still been a fast-growing industry because of increasing demand of fish and
seafood throughout the world. A large amount of raw material is processed for the
development of fishery products annually. The main processes presenting in fishery industry
are defrosting, cooking, canning and cleaning. For example, the process for canned tuna
comprises the following stages: defrosting, cooking, peeling, canning and the finishing
operations, which are similar to all lines (sauce or brine filling, sterilization and packing). In
the case of mussel, the main steps are washing, trimming, cooking, size classifying,
dehydrating and finishing operation. Sardine processing includes scraping, cutting,
conveying, canning and finishing operation. The process for other species (octopus, squids,
mackerel, etc.) is similar. A more detailed description of all these manufacturing has been
previously published (Veiga et al. 1994).
The major part of aquatic animals for fishery processing is meat. Therefore a big part of
raw material as well as the effluents from fishery processing plant is wasted. Wastewater from
fishery processing contains a high variable content of organic matter of both suspended and
dissolved solids, it is thereby characterized as a nontoxic effluent. The main environmental
problems of fishery industries are related to the emission of large volume wastewaters. During
the processing of fishery products, the amount of raw material which is converted into waste
can reach 50 % by weight (Aguilar and Sant Anna 1988). The solid wastes include bone, skin,
dark meat, viscera and pieces from flaking, shells, etc. The liquid waste includes the water
pumped together with the fish during its unloading, washing water, cooking juice, oil, blood,
mucus, etc (Afonso and Borquez, 2002). For example, in the production of surimi, about 80 %
of the original raw materials is considered as waste (Dewitt and Morrissey, 2002). The amount
of chilled-fresh water used for washing purposes during surimi processing is approximately 27
m
3
/ton of surimi product. The organic load of these wastewater is also high. In the case of
canned tuna processing, there are 23-25% solid waste (e.g. head, skin, viscera) and nearly 35%
liquid waste (e.g. blood, tuna cooking juice, oil) (Prasertsan
et al
., 1988).
In addition to the process of product development, the increase of the world fishery
production can be mainly attributed to aquaculture. Indeed while the total catch from fisheries
has been leveling off since the last decade, aquaculture has been constantly growing at a rate
of 10% per year due to the fact that the majority of the stocks are being fully exploited (FAO,
2006). Waste discharges from aquaculture facilities can have a pronounced effect on their
surroundings (Wu, 1995). Increased sedimentation of organic material below fish cages,
nutrient release in receiving waters and the use of antibiotics are a few examples of possible
negative impacts of aquaculture on the environment. Unless these waste are properly treated,
they can create environmental and ecological hazards associated to their high organic content
(Danish Ministry of Fisheries, 1983). The treatment of wastes from fishery industry could be
divided into water reuse and by-product recovery. The importance of water reuse has been
definitely recognized. By-product recovery is also a cost-effective way to reduce the amount
of waste that would, otherwise, be disposed of. There are numerous ways for utilization of
fish processing by-product such as production of pet food, fish meal, fertilizers, fish silage,
protein hydrolysates, chitin and chitosan, gelatin, collagen, food flavors, bone meal, bait and
fish scales. In addition, these by-products can be used as raw materials for producing
bioactive compounds such as peptide, collagen hydrolysate, chitooligosaccarides.
