It is important to understand the definition of food science before learning about food chemistry.

Food
Science deals with the physical, chemical, and biological properties of foods. Food science is a branch of
biological science and an interdisciplinary subject involving primarily microbiology, chemistry, biology, and
engineering.
what Food chemistry is?
Food chemistry is a major aspect of food science that deals with the composition and properties of food and
the chemical changes it undergoes during handling, processing, and storage. It is the study of chemical
processes and interactions of all biological &non-biological components of foods. Food chemistry is
intimately related to chemistry, biochemistry, physiological chemistry, botany, zoology, and molecular
biology. It is similar to biochemistry in its main components such as carbohydrates, lipids, and protein, but it
also includes areas such as water, vitamins, minerals, enzymes, food additives, flavours and colours.
The primary interests in food chemistry include reproduction, growth, and changes that foods and their
constituents undergo under suitable/unsuitable environmental conditions. This discipline also encompasses
how food 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 microorganisms that convert lactose to lactic acid; an example of preventing a process
would be stopping the browning on the surface of freshly cut apples using lemon juice.
Composition of food
Food is composed of water, carbohydrates, proteins, lipids known as major components and vitamins,
minerals, colorants, flavours, bioactive substances and food additives.
1. Water
A major component of food is water, ranging from 50% in meat products to 95% in tomato products. It is
also an excellent place for bacterial growth and food spoilage if it is not properly processed. One way of
measuring this in food is by analysis of water activity which is very important in the shelf life of many foods
during processing. One of the keys to food preservation in most instances is to reduce the amount of water or
alter the water's characteristics to enhance the shelf-life. Such methods include dehydration, freezing, and
refrigeration.
2. Carbohydrates
A carbohydrate is a biological molecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms. The
simplest version of a carbohydrate is a monosaccharide which possesses the properties of carbon, hydrogen,
and oxygen in a 1:2:1 ratio under a general formula of CnH2nOn where n is a minimum of 3. Glucose is an
example of a monosaccharide and also fructose. A chain of monosaccharides form to make a polysaccharide.
Such polysaccharides include pectin, dextran, agar, and xanthan.
3. Proteins
Proteins are macromolecules consisting of one or more long chains of amino acid residues. They also play a
fundamental role in the structure and function of cells. Consisting mainly of carbon, nitrogen, hydrogen,
oxygen, and some sulphur, they also may contain iron, copper, phosphorus, or zinc. Food proteins may be
defined as those that are easily digestible, nontoxic, nutritionally adequate, functionally useable in the food
products, available in abundance, and sustainable agriculturally. Protein is commonly obtained from animal
sources: eggs, milk, and meat. Nuts, grains and legumes provide vegetable sources of protein, and protein
combining of vegetable sources is used to achieve complete protein nutritional quotas from vegetables.
4. Lipids
The term lipid comprises a diverse range of molecules and includes relatively water insoluble or nonpolar
compounds of biological origin, including waxes, fatty acids (including essential 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, while others are not.
Some are flexible, while others are rigid. Most lipids have some polar character in addition to being largely
nonpolar. Generally, the bulk of their structure is nonpolar or hydrophobic ("water-fearing"), meaning that it
does not interact well with polar solvents like water. Another part of their structure is polar or hydrophilic
("water-loving") and will tend to associate with polar solvents like water. This makes them amphiphilic
molecules (having both hydrophobic and hydrophilic portions). Lipids in food include the oils of such grains
as corn, soybean, from animal fats, and are parts of many foods such as milk, cheese, and meat.
5. Vitamins
Vitamins are organic compounds which are vital 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). Vitamins are necessary for normal growth and good health of an individual and shortage of one
or more vitamins in the body results in deficiency diseases in the individual. From a food chemistry point of
view several of the vitamins influence the chemical nature of food, by functioning as reducing agents,
radical scavengers, reactants in browning reactions, and as flavour precursors. The main interest of food
chemistry is to maximize the retention of vitamins in food.
6. Minerals
Minerals in foods are naturally occurring inorganic substances that are large and diverse with many of them
required for the normal functioning of the body.Mineral elements are present in foods in many different
chemical forms. These forms are commonly referred to as species and include compounds, complexes, and
free ions. Mineralsarepresent in low concentrations in foods compared to carbon, hydrogen, oxygen and
nitrogen. Nonetheless, they play key functional roles in both living systems and foods. Minerals are found in
foods such as meat, cereals (including cereal products such as bread), fish, milk and dairy foods, vegetables,
fruit (especially dried fruit) and nuts.
7. 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.
8. Colour
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 used in ketchup. Caramel is a natural food dye; the industrial form known as‘caramel colouring’ is the
most widely used food colouring and is found in foods from soft drinks to soy sauce, bread, and pickles.
9. Flavours
Flavour 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 flavour chemists develop many of these
flavours for food products. On such artificial flavours include lactic acid which gives milk a tart taste.
10. Food additives
Food additives are substances added to food for preserving flavours, or improving taste or appearance. The
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.
Factors affecting food composition
 Raw Materials: The content of different components in food raw materials depends on the species and
variety of the animal or plant crop; on the conditions of life, and age of the farm harvesting of the plants;
on the feeding, conditions of life, and age of the farm animals or the fishing season for fish and marine
invertebrates; and on post-harvest changes that take place in the crop during storage.
 Processed foods: The composition of processed foods depends on the recipe applied and on changes
taking place due to processing and storage. These changes are mainly brought about by endogenous and
microbial enzymes, active forms of oxygen, heating, chemical treatment, and processing at low or high
pH.
 Changes occurring in food due to processing: Leaching of soluble, desirable and undesirable
components, such as vitamins, minerals and toxins occurs during washing, blanching and cooking. These
are lost in dripping after thawing or due to cooking. Loss of moisture and volatiles occur due to
evaporation and sublimation.
During salting, pickling, seasoning, frying or smoking there is leaching of nutrients and absorption of
desirable or harmful compounds. Due to enzyme activity, desirable or harmful compounds are formed. There
is also development of typical flavor in cheese or decarboxylation of amino acids in fish marinades.
Desirable or objectionable products are generated due to interactions of reactive groups induced by heating
or chemical treatment, such as flavors or carcinogenic compounds in roasted meats, or trans-fatty acids in
hydrogenated fats. Different products of oxidation of food components, mainly of lipids, pigments, and
vitamins are also formed. There is a loss of nutrients and deterioration of dried fish due to attacks by flies,
mites and beetles.
Alterations that can occur in quality attributes of food during processing and storage
CHEMISTRY OF WATER
Introduction
Water is an important basic element in all foods. Water is called as the universal solvent and it is a basic
necessity for the growth & metabolism of microbes and various chemical reactions that occur in food
products. Water occurs in food systems as free water and bound water. Water is found as an intracellular and
extracellular component in foods. The importance of water as a crucial component necessitates the
understanding of the properties and behaviour in food systems. The way water behaves in foods can provide
information on the stability of a product as well as its shelf life.
Definition of water in food
Water is a chemical compound composed of two hydrogen atoms and one oxygen atom. The liquid stage of
this compound is termed as water, the solid state as ice and gaseous state as steam. Water is also the most
substantial component of foods and acts as a medium by supporting chemical reactions.
Structure of Water (H₂O)
Molecular Composition Water is a chemical compound composed of two hydrogen atoms and one oxygen
atom, represented by the molecular formula H₂O.
Molecular Geometry
 Bonding: The hydrogen atoms are covalently bonded to the oxygen atom, sharing electrons. Each O-H
bond involves one hydrogen atom sharing one electron with the oxygen.
 Shape: The molecular geometry of water is bent or V-shaped. This is due to the arrangement of the
electron pairs around the oxygen atom.
 Bond Angle: The angle between the two hydrogen atoms is approximately 104.5 degrees, which is
slightly less than the ideal tetrahedral angle of 109.5 degrees. This reduction is caused by the repulsion
between the lone pairs of electrons on the oxygen atom.
 Polarity: polar property allows water to separate polar solute molecules and explains why water can
dissolve so many substances.
 Electronegativity: Oxygen is more electronegative than hydrogen, meaning it attracts the shared
electrons more strongly. This unequal sharing creates a dipole moment, making water a polar molecule.
 Partial Charges: As a result, the oxygen atom carries a partial negative charge (δ-), while the hydrogen
atoms carry partial positive charges (δ+). Hydrogen Bonding
 Intermolecular Forces: The polarity of water molecules allows them to form hydrogen bonds with each
other. A hydrogen bond is an attractive force between the partially positive hydrogen atom of one water
molecule and the partially negative oxygen atom of another.
 Impact of Hydrogen Bonds: These bonds are responsible for many of water's unique properties, such as
its high boiling point, high specific heat, and surface tension.

Properties Influenced by Structure

1. High Specific Heat: Water can absorb a lot of heat before its temperature changes significantly, which
helps regulate climate and maintain stable environments for living organisms.
2. Density: Water is unique in that it is less dense in its solid state (ice) than in its liquid state, allowing ice to
float on water. This is due to the arrangement of hydrogen bonds in the solid state, which forms a crystalline
structure.
3. Solvent Properties: Water's polarity makes it an excellent solvent, particularly for ionic and polar
substances. It can dissolve a wide range of compounds, earning it the title "universal solvent."
4. Surface Tension: The hydrogen bonds between water molecules create a high surface tension, allowing
small objects to float on the surface and enabling phenomena like water striders walking on water.

Water in Foods
Foods are composed of proteins, polysaccharides, minerals, pigments, and many other constituents in
addition to water. These constituents interact with water and significantly affect the properties and status of
water. Generally, the water in foods can be classed as ―bulk water and ―bound water
Bound Water
Bound water is water that exists in the vicinity of solutes and other nonaqueous constituents and binds to
other solutes through covalent bonds. According to the binding strength, bound water is further divided into
the following three types:
 Constitutional water: Water of this type is a constituent of other compounds and binds the most tightly.
Water in hydrates belongs to this type.
 Monolayer water: Water of this type is the first layer water bound to the hydrophilic groups of solutes.
The forces involved include mainly water-ion or water-polar association, followed by hydrogen bonding
between water and solutes.
 Multilayer water: Water of this type refers to water distributed in multiple layers around nonaqueous
components. The forces involved are water-water and water-solute hydrogen bonding. Multilayer water
binds tightly to nonaqueous components, but the strength is lower than that of monolayer water. Besides,
multilayer water has changed properties compared with ordinary water.
Bulk Water
Bulk water or free water is not chemically bound to nonaqueous compounds and mainly includes water that
is physically entrapped. Based on the physical interaction, bulk water is further divided into two types:
 Entrapped water: Water of this type is entrapped by microstructures or ultra structures and cannot flow
freely as pure water.
 Capillary water: Water of this type is restricted in the gaps between cells or the capillaries of food
structures. Capillary water has similar reduced fluidity and vapor pressure as entrapped water.