|
|
|
|
|
Food chemistry is the study of chemical processes and interactions of all biological and non-biological components of foods. It deals with the production, processing, distribution, preparation, evaluation, and utilization of food. Basic food chemistry is mainly concerned with the three primary components in food: carbohydrates, lipids and proteins.
Carbohydrates – empirical formula Cx(H2O)z - are the most widely distributed and abundant organic compounds on earth. They have a central role in the metabolism of plants and animals. Carbohydrate biosynthesis in plants starting from carbon dioxide and water in the presence of light – known as photosynthesis – is the basis for the existence of all other organisms which depend on the consumption of organic substances with food.
Carbohydrates represent one of the basic nutrients and are the most important source of energy. They are obtained from plant foods such as cereals, fruit and vegetables. Other important functions in food are fulfilled by carbohydrates. They act for instance as sweetening, gel or paste-forming and thickening agents, stabilizers and are also precursors for aroma and coloring substances, especially in thermal processing.
Carbohydrates are divided into monosaccharides (glucose, fructose, galactose), oligosaccharides (saccharose, maltose, lactose) and polysaccharides (starch, cellulose).
Lipids include fats, oils, waxes and cholesterol. They are insoluble in water and soluble in non-polar solvents. In the body, fat serves as a source of energy, a thermal insulator, and a cushion around organs. The majority of lipids are derivatives of fatty acids.
Some lipids act as building blocks in the formation of biological membranes which surround cells and subcellular particles. Such lipids occur in all foods, but their content is often less than 2%. Nevertheless, even as minor food constituents they deserve particular attention, since their high reactivity may strongly influence the organoleptic quality of the food. In most instances oils are from plants (nuts, olives and seeds) and fats are from animal products (meat, milk products, eggs and seafood). Lipids are used for flavor, to cook foods and to improve the texture of foods.
Proteins are vital components of all life. They are natural polymers made from combinations of 20 different 2-aminoacids. Every cell requires protein (amino acids) for structure and function. Eight of these amino acids are essential for adults and children and nine are essential for infants. Essential means that cannot be synthesized in large quantities in vivo and therefore they must be included in our diet.
Animal protein is generally more valuable nutritionally than vegetable protein because animal protein contains the full complement of essential amino acids. Vegetable protein, in general, tends to lack one or more of the essential amino acids. Cereal protein, for example, lacks lysine, which is an essential amino acid. In addition, proteins directly contribute to the flavor of food and are precursors for aroma compounds and colors formed during thermal or enzymatic reactions in production, processing and storage of food. Proteins also contribute significantly to the physical properties of food through their ability to build or stabilize gels, foams and emulsions.
The most important sources of protein are grain, oilseeds and legumes, followed by meat and milk. Some common protein-rich foods are prawns, fish, meat, beans, eggs, nuts, mushrooms, milk, soya beans, tofu, cheese and yoghurt.
References
- H-D. Belitz et al. “Food Chemistry”, 4th Edition, Springer Verlag, 2009
- P. Barham et al., Chem. Rev., 110, 2313 (2010)
- L.H. Skibsted, “Lipid Oxidation Pathways”, AOCS Press: Urbana, Illinois: 2008
- H.E. Nursten, “The Maillard reaction - Chemistry, biochemistry and Implications”, The Royal Society of Chemistry: Cambridge, 2005
No comments:
Post a Comment