Food chemistry
Food chemistry is the study of chemical processes and interactions of the biological and nonbiological components of foods. It deals with areas such as food composition, quality, preservation, and deterioration, and methods of food processing.
The biological substances include such items as meat, poultry, lettuce, beer, and milk as examples. It is similar to biochemistry in its main components such as carbohydrates, lipids, and proteins, but it also includes areas such as water, vitamins, minerals, enzymes, food additives, flavors, and colors. This discipline also encompasses how products change under certain food processing techniques and ways either to enhance or to prevent them from happening. An example of enhancing a process would be to encourage fermentation of dairy products with lactic acid; an example of a preventing process would be stopping the Maillard reaction on the surface of freshly cut Red Delicious apples whether cut by hand or by machine.
Brief history of food chemistry
The history of food chemistry dates back to the late 1700s, when many famous chemists were involved in discovering chemicals important in foods. In 1785, for example, Carl Wilhelm Scheele isolated malic acid from apples. In 1813, and Sir Humphry Davy published the first book on agricultural and food chemistry, titled Elements of Agricultural Chemistry, in a Course of Lectures for the Board of Agriculture in the United Kingdom. This book served as a foundation for the profession worldwide and went into a fifth edition.
In 1874, the Society of Public Analysts was formed, with the aim of applying analytical methods to benefit the public.[1]. Its early experiments were based on bread, milk, and wine.
It was also out of concern for the quality of the food supply, mainly food adulteration and contamination issues stemming first from intentional contamination and proceeding later to chemical food additives by the 1950s. The development of colleges and universities worldwide, most notably in the United States, expanded food chemistry through research of dietary substances, most notably the single-grain experiment during 1907-11. Additional research by Harvey W. Wiley at the United States Department of Agriculture during the late nineteenth century played a key role in creation of the United States Food and Drug Administration in 1906. The American Chemical Society established their Agricultural and Food Chemistry Division in 1908,[2] and the Institute of Food Technologists established their Food Chemistry Division in 1995.[3]
Water
A major component of food is water, which can range in content from 50 percent in meat products to 95 percent in lettuce, cabbage, and tomato products. It also provides a place for bacterial growth and food spoilage if it is not properly processed. One way of measuring this in food is by water activity, which is very important in the shelf life of many foods during processing. One of the keys to food preservation is to reduce the amount of water or alter the water's characteristics to enhance shelf-life. Such methods include dehydration, freezing, and refrigeration.
Carbohydrates
Carbohydrates form the largest group of substances in food consumed by humans. A common carbohydrate is starch.
The simplest version of a carbohydrate is a monosaccharide made up of molecules in which carbon, hydrogen, and oxygen atoms are in the ratio 1:2:1. Thus the general formula of a monosaccharide is CnH2nOn, where n is a minimum of 3. Glucose and fructose are examples of monosaccharides. The familiar table sugar is sucrose, a disaccharide. Each molecule of sucrose is made up of a combination of one glucose and one fructose molecule.
A chain of monosaccharides forms a polysaccharide. Such polysaccharides include pectin, dextran, agar, and xanthan.
Sugar content is commonly measured in degrees brix.
Lipids
The term lipid encompasses a diverse range of molecules and to some extent is a catchall for relatively water-insoluble (nonpolar) compounds of biological origin. Examples of lipids are waxes, fatty acids, fatty-acid derived phospholipids, sphingolipids, glycolipids and terpenoids, such as retinoids and steroids. Some lipids are linear aliphatic molecules, while others have ring structures. Some are aromatic. Some are flexible, and others are rigid.
Most lipids have some polar character, in addition to being largely nonpolar. In other words, the bulk of the structure of a lipid molecule is nonpolar or hydrophobic, meaning that it does not interact well with polar solvents like water. Another part of the molecular structure is polar or hydrophilic and will tend to associate with polar solvents like water. Thus lipid molecules are amphiphilic, having both hydrophobic and hydrophilic portions. In the case of cholesterol, the polar group is a mere -OH (hydroxyl or alcohol).
In food, lipids are present in the oils of grains such as corn and soybean, and they are also found in meat, milk, and dairy products. They act as vitamin carriers as well.
Proteins
Proteins make up over 50 percent of the dry weight of an average living cell and are very complex macromolecules. They play a fundamental role in the structure and function of cells. Protein molecules are constructed mainly of carbon, hydrogen, oxygen, and some sulfur, they may also contain iron, copper, phosphorus, or zinc.
In food, proteins are essential for growth and survival, but the amount of protein needed by an individual varies, based on the person's age and physiology (such as during pregnancy). Proteins in food are commonly found in peanuts, meat, poultry, and seafood.
Enzymes
Enzymes are biochemical catalysts used in converting processes from one substance to another. They are also involved in reducing the amount of time and energy required to complete a chemical process. Many aspects of the food industry use catalysts, including baking, brewing, dairy, and fruit juices, to make cheese, beer, and bread.
Vitamins
Vitamins are nutrients required in small amounts for essential metabolic reactions in the body. These are broken down in nutrition as either water soluble (Vitamin C) or fat soluble (Vitamin E). An adequate supply of vitamins can prevent such diseases as beriberi, anemia, and scurvy while an overdose of vitamins can produce nausea and vomiting or even death.
Minerals
Dietary minerals in foods are large and diverse with many required to function while other trace elements can be hazardous if consumed in excessive amounts. Bulk minerals with a Reference Daily Intake (RDI, formerly Recommended Daily Allowance (RDA)) of more than 200 mg/day are calcium, magnesium, and potassium while important trace minerals (RDI less than 200 mg/day) are copper, iron, and zinc. These are found in many foods, but can also be taken in dietary supplements.
Color
Food coloring is added to change the color of any food substance. It is mainly for sensory analysis purposes. It can be used to simulate the natural color of a product as perceived by the customer, such as red dye like FD&C Red No.40 (Allura Red AC) to ketchup or to add unnatural colors to a product like Kellogg's Froot Loops. Caramel is a natural food dye; the industrial form, caramel coloring, is the most widely-used food coloring and is found in foods from soft drinks to soy sauce, bread, and pickles.
Flavors
Flavor in food is important in how food smells and tastes to the consumer, especially in sensory analysis. Some of these products occur naturally like salt and sugar, but flavor chemists (called a "flavorist") develop many of these flavors for food products. Such artificial flavors include methyl salicylate which creates the wintergreen odor and lactic acid which gives milk a tart taste.
Food Additives
Food additives are substances added to food for preserving flavors, or improving taste or appearance. These processes are as old as adding vinegar for pickling or as an emulsifier for emulsion mixtures like mayonnaise. These are generally listed by "E number" in the European Union or GRAS ("Generally recognized as safe") by the United States Food and Drug Administration.
See also
Notes
- ↑ Proc. Soc. Analyt. Chem, 1874, p. 234
- ↑ Agricultural and Food Chemistry, A Division of ACS. Retrieved June 22, 2008.
- ↑ Food Chemistry Division. Institute of Food Technologists. Retrieved June 22, 2008.
ReferencesISBN links support NWE through referral fees
- Fennema, O.R., Ed. (1985). Food Chemistry - Second Edition, Revised and Expanded. New York: Marcel Dekker, Inc.
- Francis, F.J. (2000). "Harvey W. Wiley: Pioneer in Food Science and Quality." In A Century of Food Science. Chicago: Institute of Food Technologists. pp. 13-14.
- Potter, N.N. and J.H. Hotchkiss. (1995). Food Science, Fifth Edition. New York: Champman & Hall. pp. 24-68.
- U.S. Food and Drug Administration. (1993). Everything Added to Food in the United States. Boca Raton, FL: C.K. Smoley (c/o CRC press, Inc.).
External links
- American Chemical Society Agricultural and Food Chemistry Division website.
- Institute of Food Technologists Food Chemistry Division website.
- Association of Public Analysts
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