Composition and Properties of Meat Chemical

By: Suharyanto

Meat chemical composition comprises 56-72% water, 15-22% protein, 5-34% fat, and soluble non protein substances 3.5% including carbohydrates, organic salt, dissolved nitrogen substances, minerals and vitamins (Lawrie, 1991). Meanwhile, Aberle et al. (2001) state meat contains 70% water, 19% protein, 5% fat, 3.5% non-protein substances, and minerals and other materials 2.5%. However, Paleari et al. (2003) reported that each species has different chemical characteristics.

As a source of protein, meat protein is the second largest component after the water one. Muscle protein is divided into 3 groups based on their solubility properties; firstly, sarcoplasmic protein (30%), myofibrilar protein (55%) and stromal protein or muscle tissue (15%). Sarcoplasmic proteins are soluble in water and dilute salt solution contained in the sarcoplasmic. Myofibrilar protein is a protein-containing structures myofibril and are soluble in saline solution with a concentration of 1.5% or more. Stromal proteins are main constituent of connective tissue that is not soluble in salt solutions but soluble in alkali or acid treatment (Xiong, 2000).

Sarcoplasmic proteins include glyceraldehyde, aldose, enolase, creatine kinase, lactate dehydrogenase, pyruvate kinase, phosphorilase, myoglobin, calpain, chatepsin, extracellular proteins and membrane protein. Proteins are composed of myosin, actin, troponin, tropomyosin, M-protein, C-protein, Titin, Nebulin and Desmin. Myosin is the largest component in miofibril and dissolve into the solution with high ionic strength (greater than 0.3 M). Myosin has an important functional properties in meat, namely (a) is an enzyme with ATP-ase activity, (b) myosin form a complex with actin and (c) myosin form aggregate with each other to form filaments (Zayas, 1997; Xiong, 2000).

Stromal proteins include collagen, elastin and reticuline. This protein directly affects meat quality (Zayas, 1997) by:
1. Lowering the tenderness of meat and it depends on the number of stromal protein and the degree of cross-linking other stromal proteins.
2. Influencing meat emulsion capasity due to this protein is not soluble in water.
3. Lowering Water Binding Capacity of meat because of the low content of hydrophilic and charged amino acids.
4. Lowering meat nutritional value.

Muscle protein solubility is one of the factors influencing properties of water retention in the muscles and eventually affects meat quality. Physical and chemical bonding in muscle protein affects structural and texture muscle protein. There is a correlation between protein structure and solubility, and is related to tenderness or hardness of meat during processing and storage (Zayas, 1997).

Other chemical components that quite important in meat is fat. Although relatively few in amount, it is the 3rd largest chemical component in the flesh. Fat in meat has both beneficial and detrimental roles. One of the disadvantages is the oxidation. It affects meat processing.

Fat is an important energy source because of the amount of energy produced can be doubled from that generated by proteins and carbohydrates. Fat in meat is generally in triglycerides form. The composition of triglycerides significantly determines meat tenderness and roughness. Fatty acid composition in each species is different and it is also has different effect on fat properies in each species. Total saturated fatty acids in sheep, cattle and pigs respectively 53%, 45% and 40%, while the unsaturated fatty acids respectively were 47%, 55% and 60% (Warriss, 2000).

Posted in: Animal Product Technology