The nutritional value of meat is essentially related to the content of high quality protein. High quality proteins are characterized by the content of essential amino acids which cannot be synthesized by our body but must be supplied through our food. In this respect the food prepared from meat has an advantage over those of plant origin. There are vegetable proteins having a fairly high biological value(see page 431), for instance soy protein, the biological value of which is about 65% of that of meat. Soy protein concentrates are also very useful ingredients in many processed meat products, where they not only enhance the nutritional value but primarily the water binding and fat emulsifying capacity.
The contractile proteins or myofibrillar proteins are quantitatively the most important (some 65%) and are also qualitatively important as they have the highest biological value. Connective tissues contain mainly collagen, which has a low biological value. Elastin is completely indigestible. Collagen is digestible but is devoid of the essential amino acid tryptophan.
Blood proteins have a high content oftryptophan but are nevertheless of a lower biological value than meat due to their deficiency of the essential amino acid isoleucine.
Animal fats areprincipally triglycerides. The major contribution of fat to the diet is energy or calories. The fat content in the animal carcass varies from 8 to about 20% (the latter only in pork, see table 1). The fatty acid composition of the fatty tissues is very different in different locations. External fat (“body fat”) is much softer than the internal fat surrounding organs due to a higher content of unsaturated fat in the external parts.
The unsaturated fatty acids (linoleic,linolenic and arachidonic acid) are physiologically and nutritionally important asthey are necessary constituents of cell walls, mitochondria and other intensively active metabolic sites of the living organism. The human body cannot readily produce any of the above fatty acids , hence they have to be made available in the diet. Meat and meat products are relatively good sources, but in some plant sources such as cereals and seeds, linoleic acid is usually present at about 20times the concentration found in meat.
In recent years it has been suggested that a high ratio of unsaturated / saturated fatty acids in the diet is desirable as this may lower the Meat, fat and other edible carcass parts 15 individual’s susceptibility to cardiovascular diseases in general, and to coronary heart disease in particular. There is evidence to indicate that a diet which predominantly contains relatively saturated fats (such as those of meat) raises the level of cholesterolin the blood. To avoid possible health risks from the consumption of the meat, vulnerable groups should reduce the animal fat intake.
In this context, the “hiding” of high fat contentsin some processed meat products can be a dietary problem. Improved processing equipment and techniques and/or new or refined ingredients has made it possible to produce meat products with relatively high fat contents, which may be difficult to recognize by consumers. In particular in products like meat loaves, frankfurter type sausages or liver pate, where meat and fat are finely comminuted and the fat particles are enclosed in protein structures, the fat is difficult to detect visibly. Fat contents of up to 40% may be hidden this way, which is profitable for the producer as fat is a relatively cheap raw material. For some consumer groups, such diets are not recommended. On the other hand, there are many physically active hard working people or undernourished people, in particular in the developing world, where meat products with higher fat content may be beneficial in certain circumstances, predominantly as energy sources.
Meat and meat products are excellent sources of the B-complex vitamins (see table 1). Lean pork is the best food source of Thiamine (vitamin B1) with more than 1 mg / 100 g as compared to lean beef, which contains only about 1/10 of this amount. The daily requirement for humans of this rarely occurring vitamin is 1-1.5 mg. Plant food has no vitamin B 12, hence meat is a good source of thisvitamin for children, as in their organisms deposits of B12 have to be established. On the other hand, meat is poor in the fat soluble vitamins A, D, E, K and vitamin C.
However, internal organs, especially liver and kidney generally contain an appreciable percentage of vitamin A, C, D, E and K. Most of the vitamins in meat are relatively stable during cooking or processing, although substantial amounts may be leached out in the drippings or broth. The drip exuding from the cut surface of frozen meat upon Fig. 18: Meat loaves with different fat contents; Left lower fat (20%) and right high fat (35%).
Table 1: Average content of vitamins in meat (micrograms per 100g)
The mineral contents of meat include calcium, phosphorus, sodium, potassium, chlorine, magnesium with the level of each of these minerals above 0.1%, and trace elements such as iron, copper, zinc and many others. Blood, liver, kidney, other red organs and to a lesser extent lean meat, in particular beef are good sources of iron. Iron intake is important to combat anaemia, which particularly in developing countries is still widespread amongst children and pregnant women. Iron in meat has a higher bio-availability, better resorption and metabolism than iron in plant products.
The authors of this article are
- Syed Mudabbar Hussain Shah from Department of Food Engineering. a
- Fahim Ali Jawad from Department of a
- Mirtab Ali from Department of Food Science & Technology. a
*a = University of Agriculture, Faisalabad.