Lie Improving Farmed Fish Quality and Safety

1. Auflage 2008
ISBN: 978-1-84569-492-0
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 648 Seiten

Reihe: Woodhead Publishing Series in Food Science, Technology and Nutrition

Global aquaculture production has grown rapidly over the last 50 years. It is generally accepted that there is limited potential to increase traditional fisheries since most fish stocks are well or fully exploited. Consequently increased aquaculture production is required in order to maintain global per capita fish consumption at the present level. Fish farming enables greater control of product quality and safety, and presents the possibility of tailoring products according to consumer demands. This important collection reviews safety and quality issues in farmed fish and presents methods to improve product characteristics.The first part of the book focuses on chemical contaminants, chemical use in aquaculture and farmed fish safety. After an opening chapter discussing the risks and benefits of consumption of farmed fish, subsequent contributions consider environmental contaminants, pesticides, drug use and antibiotic resistance in aquaculture. Part two addresses important quality issues, such as selective breeding to improve flesh quality, the effects of dietary factors including alternative lipids and proteins sources on eating quality, microbial safety of farmed products, parasites, flesh colouration and off-flavours. Welfare issues and the ethical quality of farmed products are also covered. The final part discusses ways of managing of product quality, with chapters on HACCP, monitoring and surveillance, authenticity and product labelling.With its distinguished editor and international team of contributors, Improving farmed fish quality and safety is a standard reference for aquaculture industry professionals and academics in the field. - Reviews safety and quality issues in farmed fish and presents methods to improve product characteristics - Discusses contaminants, persistent organic pollutants and veterinary drug residues and methods for their reduction and control - Addresses important quality issues, genetic control of flesh characteristics and the effects of feed on product nutritional and sensory quality

Autoren/Hrsg.

Lie, Øyvind

Leseproben

1 The risks and benefits of consumption of farmed fish
J. Tuomisto    KTL National Public Health Institute, Finland L. Frøyland    National Institute of Nutrition and Seafood Research (NIFES), Norway 1.1 Introduction: the human health implications of consumption of farmed fish
The aim of this chapter is to give information on benefits and risks of consuming farmed fish. A major part of relevant published information is based on studies dealing with fish in general, or using pure compounds such as n-3 poly-unsaturated fatty acids. Therefore it is necessary to outline first the benefits and risks based on studies of fish in general. Then findings will be extrapolated to farmed fish utilising the information on health-promoting compounds and contaminants of farmed fish compared with wild fish, as well as specific health studies available on the consumption of farmed fish. Fish has long been considered excellent food. There are clear benefits, but there are also some problems partly different from other equivalent food items (Table 1.1). Most of these benefits and risks are not restricted to fish, but often they are more prominent in fish than, e.g., meat or dairy products. Table 1.1 Examples of some benefits and risks of fïsh consumption • Nutritional value (e.g., good quality protein) • Essential n-3 fatty acids (cardiovascular and nervous system benefits, anticarcinogenicity) • Certain vitamins (e.g., vitamin D) and minerals (e.g., I, Se) • Replaces hard fats in diet • Microbiological problems (requires good hygiene and ice-cold storage) • Toxins (e.g., botulinum toxin, certain algal toxins) • Chemical contaminants (e.g., HG, AS, PCBs, dioxins, organochlorine pesticides) 1.2 Nutrients in fish and other seafood
Fish and other seafood contain relatively high levels of many different nutrients, and based on an assessment of nutritional factors, they are good sources of protein, fat, especially the long, polyunsaturated marine n-3 fatty acids, vitamin D, vitamin B12, selenium and iodine. 1.2.1 Fat
Fat is not distributed equally in fish, and the fat content decreases from the head to the tail. In fatty fish the fat is contained in the muscle (fillet), while in lean fish the fat is located primarily in the liver. For this reason, the oil is extracted from the cod liver. Farmed salmon is fatty, whereas wild salmon in general contains less fat, in part because wild salmon have a limited food intake on their journey from the open sea to the rivers for spawning. In addition, during the process of sexual maturation, fat is transferred from the muscle for use in the development of reproductive glands (with the products roe and milt), which further reduces the fat content of the fillet. Because sexually mature salmon are not considered to be of top quality, this process of fat transfer is avoided in the production of farmed salmon. Most fish species are leaner immediately prior to spawning, but they regenerate the fat content in the period up to the next spawning. Because lean fish, such as cod, stores its excess fat in the liver, the amount of fat in the fillet does not depend on the amount of fat in the feed. However, the composition of fatty acids in the fillet (and liver of cod fish) does reflect the fatty acid profile of the feed, and the composition of fatty acids in the blood lipids of those who eat fish (farmed and wild) and other seafood. This is especially the case for fatty fish or when consuming fish liver. A recently published article documents the correlation between the fatty acid profile of salmon feed, the fatty acid composition of salmon fillet, and the blood lipids of those who eat the salmon (Seierstad et al., 2005). People and animals can synthesise most of the fatty acids they need, except for linoleic acid (LA, 18:2 n-6) in the n-6 series and a-linolenic acid (ALA, 18:3 n-3) in the n-3 series. As a result, these two fatty acids are called essential and must be supplied through the diet. Many plant oils, especially soy oil, are rich in LA, and because of the widespread use of soy oil and soy beans as food and in animal feed, this is the dominant polyunsaturated fatty acid in the Western diet. Some plant oils contain significant amounts of ALA, such as linseed oil and rapeseed (canola) oil. ALA is part of many important metabolic pathways, the most important being the synthesis of the n-3 fatty acids eicosapentaenoic acid (EPA, 20:5 n-3), docosapentaenoic acid (DPA, 22:5 n-3) and docosahexaenoic acid (DHA 22:6 n-3), substrate for fatty acid oxidation (energy production) and the recirculation of carbon atoms to de novo (new) synthesis of fatty acids (Sinclair et al., 2002). Fish and other seafood, especially fatty fish and fish oils as well as oils extracted from the blubber of sea mammals, are the main sources of EPA, DPA and DHA. This is because plant plankton in the sea effectively produces EPA, DPA and DHA from ALA. In this marine food chain from plant plankton via animal plankton to fish, significant amounts of EPA and DHA are accumulated in the food web. In farmed fish the levels of EPA and DHA are determined by the levels in the feed. 1.2.2 Protein
Protein is found in all organic material from plant cells to animal cells. Proteins are built up of 20 different amino acids. Proteins in the diet provide amino acids, nitrogen and sulphur, and they are a source of energy. Unlike fat, excessive amounts of protein are not stored; thus, the body depends on a constant supply of protein for normal weight and maintenance. The protein content of fish varies much less than the fat content, and constitutes 15–20 grams per 100 grams of fish. Fish protein is a high quality protein source, i.e. it contains all essential amino acids and is easily digestible. Some findings suggest that marine protein possesses health properties. When the casein protein of a high-fat (HF) diet was fully replaced by cod protein, insulin resistance did not develop in rats (Lavigne et al., 2001). 1.2.3 Vitamins
Fish and other seafood, especially fatty fish, are rich sources of many different vitamins, primarily the fat-soluble vitamins (vitamin A to some extent, and especially vitamin D), as well as the water-soluble vitamin B12. Vitamin A is synthesised by plants and microorganisms in the form of provitamin A (carotenoids) which are converted to vitamin A in the intestine. Vitamin A is essential for humans and plays a role in a number of important functions, such as eyesight, immune response, growth, development and reproduction. Vitamin A deficiency leads to reduced immune response and increased mortality as a consequence of this. In many developing countries, vitamin A deficiency is a major cause of blindness. The biochemical basis for the role played by vitamin A in eyesight was documented early on, but other functions of vitamin A appear to be mediated through the regulation of gene expression in the various cell types, often in connection with cell growth and differentiation. Fatty fish (fillet), liver from cod and cod liver oil contain significant amounts of retinol. Cod liver contains 12–15 mg per 100 g, and cod liver oil generally contains approximately 5 mg per 100 ml. Humans synthesise vitamin D in the skin by means of sunlight, but the exposure depends on several factors, including the light intensity and the surface area of skin exposed to sunlight. Vitamin D is necessary for normal calcium absorption in the intestine, normal bone metabolism and normal cell differentiation. Vitamin D deficiency leads to rickets in children and osteomalacy (soft bones) in adults. In the diet, vitamin D is found naturally in fish and fish liver. Fatty fish species have higher vitamin D content than partially fatty fish. In lean fish most of the vitamin D is found in the fish liver. In general, both marine and freshwater fish represent a natural source of vitamin D. B vitamins are important for energy metabolism, and vitamin B12 is an umbrella term for a number of bioactive compounds that contain cobalt (corrinoids) and are involved in a number of methylation reactions (one carbon atom transfer). Vitamin B12 is found primarily in animal products, and fish and other seafood are good sources of this vitamin. 1.2.4 Minerais
Iodine is important for normal functioning of the thyroid gland and production of the hormones thyroxine (T4) and triiodothyronine (T3). A deficiency of iodine in the diet is associated with enlargement of the thyroid gland (development of goitre), and hypothyroidism results in arrested growth and mental retardation in children, and low metabolism, low blood pressure and muscle weakness in adults. In a global context, iodine deficiency is a significant problem, and in half the countries in Europe the population has insufficient iodine intake (Vitti et al., 2003). Fish and other seafood are naturally high in iodine. Selenium is an essential trace element and plays an important role as the cofactor for the enzyme glutathione peroxidase. Selenium is involved in antioxidant reactions...