Food chemistry is the study ofchemical processes and interactions of all biological and non-biological components of foods.[1][2] The biological substances include such items asmeat,poultry,lettuce,beer, andmilk as examples. It is similar tobiochemistry in its main components such ascarbohydrates,lipids, andprotein, but it also includes substances such as water,vitamins,minerals,enzymes,food additives,flavors, andcolors. This discipline also encompasses how products change under certainfood processing techniques and ways either to enhance or to prevent those changes from happening. An example of enhancing a process would be to encourage fermentation ofdairy products withmicroorganisms that convertlactose tolactic acid; an example of preventing a process would be stopping thebrowning on the surface of freshly cutapples usinglemon juice or otheracidulated water.
The scientific approach to food andnutrition arose with attention toagricultural chemistry in the works ofJ. G. Wallerius,Humphry Davy, and others. For example, Davy publishedElements of Agricultural Chemistry, in a Course of Lectures for the Board of Agriculture (1813) in the United Kingdom which would serve as a foundation for the profession worldwide, going into a fifth edition. Earlier work included that byCarl Wilhelm Scheele, who isolatedmalic acid from apples in 1785.
Some of the findings ofLiebig on food chemistry were translated and published byEben Horsford in Lowell Massachusetts in 1848.[3]
In 1874 the Society of Public Analysts was formed, with the aim of applying analytical methods to the benefit of the public.[4] Its early experiments were based on bread, milk, and wine.
It was also out of concern for the quality of the food supply, mainly foodadulteration and contamination issues that would first stem from intentional contamination to later with chemicalfood additives by the 1950s. The development ofcolleges anduniversities worldwide, most notably in the United States, would expand food chemistry as well as research of the dietary substances, most notably theSingle-grain experiment during 1907-11. Additional research byHarvey W. Wiley at theUnited States Department of Agriculture during the late 19th century would play a key factor in the creation of theUnited States Food and Drug Administration in 1906. TheAmerican Chemical Society established its Agricultural and Food Chemistry Division in 1908 while theInstitute of Food Technologists established its Food Chemistry Division in 1995.
Food chemistry concepts are often drawn fromrheology, theories oftransport phenomena,physical andchemical thermodynamics,chemical bonds, and interaction forces,quantum mechanics andreaction kinetics,biopolymer science,colloidal interactions,nucleation,glass transitions and freezing/disordered or noncrystalline solids, and thus hasFood Physical Chemistry as a foundation area.[5][6]
A major component of food is water, which can encompass anywhere from 50% inmeat products to 95% inlettuce,cabbage, andtomato products. It is also an excellent place forbacterial growth and food spoilage if it is not properly processed. One way this is measured in food is bywater activity which is very important in the shelf life of many foods during processing. One of the keys tofood preservation in most instances is reduce the amount of water or alter the water's characteristics to enhance shelf-life. Such methods includedehydration,freezing, andrefrigeration[7][8][9][10] This field encompasses the "physiochemical principles of the reactions and conversions that occur during the manufacture, handling, and storage of foods".[11]
Comprising 75% of the biological world and 80% of all food intake for human consumption, the most common known human carbohydrate issucrose[citation needed]. The simplest version of a carbohydrate is amonosaccharide which containscarbon,hydrogen, andoxygen in a 1:2:1 ratio under a general formula of CnH2nOn where n is a minimum of 3.Glucose andfructose are examples of monosaccharides. When combined in the way that the image to the right depicts,sucrose, one of the more commonsugar products found in plants, is formed.
A chain of monosaccharides form to make apolysaccharide. Such polysaccharides includepectin,dextran,agar, andxanthan.[12] Some of these carbohydrate polysaccharides are accessible for digestion by human enzymes and mainly absorbed in the small intestine, whereas dietary fiber passes to the large intestine where some of these polysaccharides are fermented by the gastrointestinal microbiota.[13]
Sugar content is commonly measured in degreesbrix.
The term lipid comprises a diverse range ofmolecules and to some extent is a catchall for relatively water-insoluble ornonpolar compounds of biological origin, includingwaxes,fatty acids (includingessential fatty acids), fatty-acid derived phospholipids, sphingolipids, glycolipids and terpenoids, such as retinoids andsteroids. Some lipids are linearaliphatic molecules, while others have ring structures. Some arearomatic, while others are not. Some are flexible, while others are rigid.
Most lipids have somepolar character in addition to being largely nonpolar. Generally, the bulk of their structure is nonpolar orhydrophobic ("water-fearing"), meaning that it does not interact well with polar solvents like water. Another part of their structure is polar orhydrophilic ("water-loving") and will tend to associate with polar solvents like water. This makes themamphiphilic molecules (having both hydrophobic and hydrophilic portions). In the case ofcholesterol, the polar group is a mere -OH group (hydroxyl or alcohol).
Lipids in food include the oils of such grains ascorn,soybean, from animal fats, and are parts of many foods such as milk,cheese, and meat. They also act as vitamin carriers.
Proteins comprise over 50% of the dry weight of an average living cell[citation needed][clarification needed] and are very complex macromolecules. They also play a fundamental role in the structure and function of cells.[14] Consisting mainly of carbon, nitrogen, hydrogen,oxygen, and somesulfur, they also may containiron,copper,phosphorus, orzinc.
In food, proteins are essential for growth and survival, and requirements vary depending upon a person's age andphysiology (e.g., pregnancy). Protein is commonly obtained from animal sources:eggs,milk, andmeat.Nuts,grains andlegumes provide vegetable sources of protein, andprotein combining of vegetable sources is used to achievecomplete protein nutritional quotas from vegetables.
Protein sensitivity asfood allergy is detected with theELISA test.
Enzymes are biochemicalcatalysts 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, includingbaking,brewing,dairy, andfruit juices, to make cheese,beer, andbread.
Vitamins arenutrients required in small amounts for essential metabolic reactions in the body. These are broken down in nutrition as either water-soluble (vitamin C) orfat-soluble (vitamin E). An adequate supply of vitamins can prevent diseases such asberiberi,anemia, andscurvy while an overdose of vitamins can producenausea andvomiting or even death.
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 aReference Daily Intake (RDI, formerly Recommended Daily Allowance (RDA)) of more than 200 mg/day arecalcium,magnesium, andpotassium 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.
Food colouring is added to change the colour of any food substance. It is mainly for sensory analysis purposes. It can be used to simulate the natural colour 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 colours to a product likeKellogg'sFroot Loops. Caramel is a natural food dye; the industrial form, caramel colouring, is the most widely used food colouring and is found in foods from soft drinks tosoy sauce, bread, andpickles.
Flavour in food is important in how foodsmells and tastes to the consumer, especially in sensory analysis. Some of these products occur naturally likesalt andsugar, but flavour chemists (called a "flavourist") develop many of these flavours for food products. Such artificial flavours includemethyl salicylate which creates thewintergreen odor and lactic acid which gives milk a tart taste.
Food additives are substances added to food for preserving flavours, or improving taste, look, smell and freshness. The processes are as old as addingvinegar forpickling or as anemulsifier foremulsion mixtures likemayonnaise. These are generally listed by "E number" in theEuropean Union orGRAS ("generally recognized as safe") by the United StatesFood and Drug Administration.
Branches ofchemistry | |
|---|---|
| Analytical | |
| Theoretical | |
| Physical | |
| Inorganic | |
| Organic | |
| Biological | |
| Interdisciplinarity | |
| See also | |
| General |
| ||||||
|---|---|---|---|---|---|---|---|
| Preventive healthcare | |||||||
| Population health | |||||||
| Biological and epidemiological statistics | |||||||
| Infectious and epidemic disease prevention | |||||||
| Food hygiene and safety management | |||||||
| Health behavioral sciences | |||||||
| Organizations, education and history |
| ||||||
| International | |
|---|---|
| National | |
| Other | |
