Meat lipids, composition

Gonzalez-Esquerra, R. and Leeson, S. 2000. Effects of menhaden oil and flaxseed in broiler diets on sensory quality and lipid composition of poultry meat. British Poultry Sci. 41, 481—488. Gonzalez-Esquerra, R. and Leeson, S. 2001. Alternatives for enrichment of eggs and chicken meat with omega-3 fatty acids. Can. J. Anim. Sci. 81, 295-305. 

Sinclair AJ, O Dea K, Dunstan G, Ireland PD, Niall M. Effects on plasma lipids and fatty acid composition of very low fat diets enriched with fish or kangaroo meat. Lipids 1987 22(7) 523-529. 

Although nutrition specialists object to excessive consumption of animal fat, this component constitutes a considerable percentage in the global consumption balance. To improve its nutritional value, it is modified with respect to animal lipid composition and properties. The fat present in milk, eggs, and poultry meat is of particular interest. Nutritional modification of the amount and quality of cows milk fat plays an important role and can be effectively performed. However, fat modification by feeding is limited due to the biohydrogenation in rumen, resulting in a lower supply of unsaturated FA from feed. 

Morgan, C.A., Noble, R.C., Cocchi, M. and McCartney, R. (1992). Manipulation of the fatty-acid composition of pig meat lipids by dietary means. Journal of the Science of Food and Agriculture, 58, 357-368. 

Lin, C.F., Gray, J.I., Buckley, D.J., Booren, A.M. and Flegal, C.J. (1989) Effects of dietary oils and a-tocopherol supplementation of lipid composition and stability of broiler meat. 

As a first requirement, the sample analyzed should represent as closely as possible the lipid composition of the whole matrix from which it was taken furthermore, sample preparation should be carried out in such an environment as to minimize any changes in lipid properties prior to analysis. In food analysis, proper sampling of the lipid fraction requires knowledge of the physical structure and location of the major lipids in the sample, and the choice of the most adequate procedure depends on the t)q)e of food being analyzed, the nature of the lipid fraction, as well as the analytical procedure applied for the extraction. Foods consisting almost entirely of lipids, such as vegetable oils, often require little, if any, sample preparation prior to analysis. Qn the other hand, for more complex foods, such as meat or milk, extraction and purification of the lipid fraction is necessary prior to analysis. Official methods have been developed, which recommend the sample preparation and extraction procedures to be followed for a specific t)q5e of food. Solvent extraction methods are usually used, to separate lipids from water-soluble food components, prior to chromatographic analysis these are described in the sections that follow. A number of steps are usually required, prior to the solvent xtraction of lipids from a matrix ... 

JS Elmore, MM Campo, DS Mottram, M Enser. Effect of lipid composition on meat-like model systems containing cysteine, ribose, and polyunsaturated fatty acids. J Agric Food Chem 50 1126-1132, 2002. 

The lipid in muscle is composed primarily of triglycerides (depot fats) and of phospholipids (membrane components), and is a constituent which varies enormously not only in amount present, but also in properties such as degree of saturation (species dependent). The ash of lean meat is comprised of various minerals such as phosphorus, potassium, sodium, magnesium, calcium, iron and zinc Carbohydrate was not noted in the proximate composition because while some may be present, it is normally there in low concentration compared to the other constituents. Glycogen is the carbohydrate occurring in greatest concentration in muscle but is normally degraded soon after the animal is sacrificed. 

Nilzen V, Babol J, Dutta P C, Lundeheim N, Enfalt A-C and Lundstrom K (2001), Free range rearing of pigs with access to pasture grazing-effect on fatty acid composition and lipid oxidation products , Meat Sci, 58, 267-275. 

The formation of free radicals after lipid oxidation is known to play a key role in the deterioration of meat flavor 8, 23), Since proteins constitute a major portion of the muscle s composition, the relationship between chemically active radical species and decomposition of food flavor proteins and peptides needs to be studied in detail. Data has been presented showing the correlation of proteins with flavor (Figures 5 and 6). Data is now presented showing how soluble meat proteins change in an environment where free radicals are induced by a free-radical oxidation generating system or FROG (Figure 10). 

Bitman, J. 1976. Status report on the alteration of fatty acid and sterol composition in lipids in meat, milk, and eggs. In Fat Content and Composition of Animal Products. National Academy of Sciences, Washington, D. C., pp. 200-237. 

It appears, then, that there is a general, meaty aroma, common to cooked beef, pork, and lamb (and probably poultry), attributable to the pyrolysis of the mixture of low molecular weight nitrogenous and carbonyl compounds extracted from the lean meat by cold water. But the aromas of roast beef, roast pork, roast lamb, and roast chicken are unmistakably different. The chemical composition of the muscular fat deposits of these animals differ appreciably, and it is to these lipid components that we must look to account for the specific flavor differences. Heating the carefully separated fat alone does not give a meaty aroma at all, much less an animal-specific one. It is the subsequent reactions of pyrolysis products of nonlipid components that give the characteristic aromas and flavors of roasted meats (20). 

Ajuyah, A.O., Hardin, R.T. and Sim, J.S. (1993) Effect of dietary full-fat flax seed with and without antioxidant on the fatty acid composition of major lipid classes of chicken meats. Poultry Science 71,125-136. 

In initial work, L- a-phosphatidylcholine (lecithin) from egg yolk was selected as the phospholipid, and later studies compared other phospholipids and lipid extracts from meat. As the study originated from investigations of cooked meat flavor, the model system reactions were carried out in aqueous solution buffered with phosphate at an initial pH of 5.7 and concentrations of the reactants were selected to approximate their relative compositions in mammalian muscle. The reactions were carried out under pressure... 

Lipids play an important part in the development of aroma in cooked foods, such as meat, by providing a source of reactive intermediates which participate in the Maillard reaction. Phospholipids appear to be more important than triglycerides. The addition of phospholipid to aqueous amino acid + ribose mixtures leads to reductions in the concentrations of heterocyclic compounds formed in the Maillard reaction. This effect could be due to lipid oxidation products reacting with simple Maillard intermediates, such as hydrogen sulfide and ammonia, to give compounds not normally found in the Maillard reaction. The precise nature of the odoriferous products obtained from lipid - Maillard interactions is dictated by the lipid structure and may depend on the fatty acid composition and the nature of any polar group attached to the lipid. 

The chemical nature of flavor volatiles was representative of most classes of organic compounds. Hexanal was found to be the predominant volatile component In each case and Its content was directly proportional to the amount of TBA-reactlve species, while Inversely proportional to the flavor acceptability of meats. Nitrite curing depressed the production of lipid oxidation products and nltrlte-free curing composition duplicated the action of nitrite on meat, flavorwlse. 

Fat portion of meats, particularly their phospholipid components, undergo autoxidation/degradation (2) and produce an overwhelming number of volatiles. Fats also serve as a depot of fat-soluble compounds that volatilize on heating and strongly affect flavor. Since compositional characteristics of lipids in meats, vary from one species to another, these factors may be responsible for the development of some species-specific flavor notes in cooked meats (8.9 ). Obviously presence of 4-methyloctanoic and 4-... 

Several ascorbic acid derivatives were examined by Pensabene et al. (570) for their ability to inhibit nitrosation of pyrrolidine in a model system developed to simulate the lipid-aqueous-protein composition of bacon. While sodium ascorbate was quite effective in the aqueous phase, a combination of an ascorbyl ester with sodium ascorbate gave a better effect in the lipid phase (Table XX). The use of ascorbates and tocopherol as inhibitors of nitrosamine formation and oxidation in foods of the aqueous and lipid type has been reviewed by Newmark and Mergens (326). These compounds in combination could be markedly useful in preventing food contamination with nitrosamines and/or nitros-amides in cured meats such as bacon. 

Meat is the edible part of animal, chicken, or fish carcasses. Its chemical composition is as follows 60-85% water, 8-23% protein, 2-15% lipids, 0.5-1.5% saccharides, and about 1% inorganic substances (Table 2.1). These quantities change significantly depending on the kind, age, sex, level of fattening, and part of the animal carcass. The largest fluctuations are observed in the contents of water and lipids. 

Jakobsen M, Bertelsen G, Colour stability and lipid oxidation of fresh beef. Development of a response surface model for predicting the effects of temperature, storage time, and modified atmosphere composition, Meat Science 2000, 54, 49-57. 

It appears from Figs. 9.5 and 9.6 that there is a huge variation in colour stability between meat from different sources. A range of intrinsic factors influence the oxidative balance in raw meat and thereby the colour stability of the meat (Bertelsen et al., 2000). Thus the oxidative stability of muscles is dependent on the composition, concentrations, and reactivity of (i) oxidation substrates (lipids, protein and pigments), (ii) oxidation catalysts (prooxidants such as transition metals and various enzymes) and (iii) antioxidants, e.g., vitamin E and various enzymes. For review see Bertelsen et al. (2000). 

---