Damage to lipids is accentuated in the immediate post slaughter period and, in particular, during handling, processing and storage. This may be brought about by a high intake of polyunsaturated fatty acids, or by a deficiency of nutrients involved in the antioxidant defence system. Oxidative damage to lipids may occur in the living animal because of an imbalance between the production of reactive oxygen species and the animal's antioxidant defence mechanisms. It is generally accepted that lipid oxidation in muscle foods is initiated in the highly unsaturated phospholipid fraction in subcellular membranes. Oxidation of lipids is a major cause of deterioration in the quality of muscle foods and can directly affect many quality characteristics such as flavor, color, texture, nutritive value and safety of the food. The main factors governing the eating quality of muscle foods are tenderness, color and flavor. Composition of total muscle lipids was thus influenced by the ratio of the two fat classes. The influence of a fat supplemented diet on FA composition of the muscles was different for TG and PL. Fish oils decreased C18:0 but increased PUFAn-3 contents in the muscle. Linseed produced the higher level of C18:3 than other added fats. In the muscles, the variations in the C18:2 contents are influenced less when unprotected fat was added to the ration. In adipose tissues, the PUFA levels were at their highest with linseed and with safflower. Except for palm oil and cotton seeds, the vegetable fats produced adipose tissues with lower levels of SFA content than with animal fats. Moreover, in intramuscular fat the PUFAn-6/PUFAn-3 ratio was lower with forage diets. With diets including concentrate feed unsupplemented with fat, the adipose tissues and the muscles had lower contents of C18:0 and C18:3 but higher contents of C18:1 than with diets with forages only. TG had higher contents in monounsaturated FA (MUFA) and saturated FA (SFA) (TG/PL = 1.9 - 1.3 - 4.5 - 1.2 - 1.1, for MUFA, SFA, C14:0, C16:0 and C18:0, respectively) but had lower contents in polyunsaturated FA (TG/PL around 0.07 for PUFA). The phospholipid (PL) content was nearly constant for one type of muscle. The increase in intramuscular fat content with age and fattening was mainly constituted of triacylglycerols (TG). The lipid content of muscle was influenced by the genotype and the level of energy intake. The main causes of variation in the fatty acid composition has been studied in cattle by meta-analyse of data from the literature.
The fatty acid (FA) contents of adipose tissues and muscles influence the characteristics of meat quality. * Serves as a general reference book for scientists studying lipids, lipoproteins and membranes and as an advanced and up-to-date textbook for teachers and students who are familiar with the basic concepts of lipid biochemistry. * Allows scientists to become familiar with recent developments related to their own research interests, and will help clinical researchers and medical students keep abreast of developments in basic science that are important for subsequent clinical advances. Key Features: * Represents a bridge between the superficial coverage of the lipid field found in basic biochemistry text books and the highly specialized material contained in scientific review articles and monographs. All of the chapters have been extensively updated since the 4th edition appeared in 2002. The second objective is to provide a text for scientists who are about to enter the field of lipids, lipoproteins and membranes and who wish to learn more about this area of research. The chapters are written for students and researchers familiar with the general concepts of lipid metabolism but who wish to expand their knowledge in this area. The first objective is to provide students and teachers with an advanced up-to-date textbook covering the major areas of current interest in the lipid field. The 5th edition of this book has been written with two major objectives. Research on the biochemistry and molecular biology of lipids and lipoproteins has experienced remarkable growth in the past 20 years, particularly with the realization that many different classes of lipids play fundamental roles in diseases such as heart disease, obesity, diabetes, cancer and neurodegenerative disorders.
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