Seafood has traditionally been a popular part of the diet in many parts of the world and in some countries constituted the main supply of animal protein. Today even more people are turning to fish as a healthy alternative to red meat. The low fat content of many fish species (white fleshed, demersal) and the effects on coronary heart disease of the n-3 polyunsaturated fatty acids found in fatty (pelagic) fish species are extremely important aspects for health-conscious people particularly in affluent countries, where cardiovascular disease mortality is high. However, consumption of fish and shellfish may also cause diseases due to infection or intoxication. Some of the diseases have been specifically associated with consumption of seafood while others have been of more general nature.
For the purpose of this paper, seafood includes both finfish, shellfish and cephalopods (octopus, squid). The term shellfish covers the bivalve molluscan shellfish (oysters, cockles, clams and mussels), the gastropods (periwinkles, sea-snails) and the crustacean shellfish (crab, lobster, shrimp).
Seafood differs from other types of food in a number of ways. Most seafood is still extracted from a ‘wild’ population, and the fishermen are hunters with no influence on handling of their prey before it is caught. Thus it is not possible to imitate the situation for slaughter animals, selecting only the most suitable specimens for slaughter and to rest and feed them well before killing. The seafood processor is limited in his choice of raw materials to what is available in respect of size, condition and fish species landed by the fishermen. It should also be emphasized that while the inner and outer surface of warmblooded animals (gastrointestinal tract, skin) represent specific ecological environments with a very specific microbiological flora, these environments are very different for fish and shellfish. The microbiological flora in the intestines of these cold blooded animals is quite different being psychrotrophic in nature and to some extent believed to be a reflection of general contamination in the aquatic environment. Furthermore, in filter feeding bivalve molluscan shellfish (i.e. oysters), an accumulation and concentration of bacteria and viruses from the environment is generally taking place. However, some seafood is processed in a modern fish industry which is a technologically advanced and complicated industry in line with any other food industry,and with the same risk of products being contaminated with pathogenic organisms or toxin.
The quality of our foods is of major concern to food processors and public health authorities. It has been estimated that there are more than 80 million cases per annum of food-borne illnesses in the USA (Miller and Kvenberg 1986) and that the cost of these illnesses is in the order of many billions of dollars per year (Todd 1989b). The economic losses due to spoilage are rarely quantified but a report by the US National Research Council Committee (FNB/NRC 1985) estimates that one–fourth of the world's food supply is lost through microbial activity alone. Thus, the need for control of quality of our food is well documented and, since the rate of food-borne illnesses is increasing, there is also an urgent need to improve the traditional or present means of assuring the quality of food.
The word “quality” embraces a lot of meanings such as safety, gastronomic delights, purity, nutrition, consistency, honesty (e.g. in labelling), value, product excellence. This book focuses mainly on safety aspects, but also sensory quality (spoilage) will be dealt with and included in the quality assurance programmes. Control options and prevention measures to be applied within the various types of processing will be discussed.
From this very outset, a distinction needs to be drawn between Quality Assurance and Quality Control. Unfortunately, these two terms have been used indiscriminately and the difference between them has become blurred. According to International Standards Organization (ISO 8402), Quality Assurance (Q.A.) are “all those planned and systematic actions necessary to provide adequate confidence that a product or service will satisfy given requirements for quality”. In other words, Q.A. is a strategic management function which establishes policies, adapts programmes to meet established goals - and provides confidence that these measures are being effectively applied. Quality Control (Q.C.) on the other hand are “the operational techniques and activities that are used to fulfill requirements for quality” (ISO 8402), i.e. a tactical function which carries out the programmes established by the Q.A.