Food technology is a branch of food science that addresses the production, preservation, quality control and research and development of food products. Bakery at the Faculty of Food Technology, Latvia University of Life Sciences and Technologies The food technology room at Marling School in Stroud,

1. FOODTECHNOLOGY
FOOD CHEMISTRY
WATER
Lecture -3

2. Overview of water in food
• Water is a chemical substance with the chemical formula
H2O. A water molecule contains one oxygen and two
hydrogen atoms connected by covalent bonds.
• Safe drinking water is essential to humans and other life
forms
• Water plays an important role in the world economy, as it
functions as a solvent for a wide variety of chemical
substances and facilitates industrial cooling and
transportation. Approximately 70% of the fresh water used
by humans goes to agriculture.

3. • Water plays many critical roles within the field of agriculture, food, and
feed science, technology, and engineering.
• Water is the main components of drinking water, beverages and most of
foodstuffs.
• Water content of fresh fruits, vegetables, meats, and sea foods exceeds
50%. Water is used as a good medium to cook foods.

4. Why water is important
Aids with transport
Helps to break substances down
Helps to maintain body temperature/pH
• Adequate intake:
• For men: 3.7 liter / day
• For women: 2.7 liter / day
• Ideally 80% of water should coming from drinking fluids.
• 20% of water intake should come from food

5. Forms of Water in Food
• The ease of water removal from foods depends on how
it exists in the food product. The three forms of water in
food products are:
1. Free water
2. Adsorbed water
3. Water of Hydration (Bound water)

6. Free water
Free water
• Most water in foods is called free water
• Free water is lightly entrapped & therefore easily pressed from food
• It acts as a dispersing agent & solvent & can be removed by drying foods
Adsorbed water
This water associates in layer through intermolecular hydrogen bonds around hydrophilic food
molecules i.e. the water is held tightly in cell walls or protoplasm & is held tightly to proteins .

7. Free water …
Bound Water
• Bound water is the water that remains unfrozen at temperature below 0⁰C usually -20⁰C
• Also it is the amount of water in a food that is unavailable as a solvent.
• The amount of un-freezable water, based on protein content, vary from one food to another
 For E.g., About 8-10 % of the total water in animal
tissue is unavailable for ice formation. Egg white, egg yolk, meat & fish all contain
approximately 0.4gm of un-freezable water/g of dry protein. Most fruits & vegetables contain
less than 6% un-freezable water.

8. Uses of water in food preparation
Heat Transfer
• Water both transfers and moderates the effects of heat. A potato heated by itself in a pan will burn. But
surrounding that same potato with water ensures that the heat will be evenly distributed.
• Almost half of the methods used to prepare foods rely on water to transfer heat and these are known
collectively as moist-heat methods
• The major moist-heat methods discussed in this book include boiling, simmering, steaming, stewing,
and braising. Dry-heat methods use heat in the form of radiation and include baking, grilling, broiling,
and frying.

9. Uses of water in food preparation ….
Universal solvents
• The many biochemical interactions occurring in living organisms—human, animal,
and plant—could not occur in the absence of a solvent environment. Water is
considered to be the earth's universal solvent.The fluid substance, mostly water,
within and around the cell is a solvent that contains many dissolved substances
called solutes.
• Combining a solvent and asolute results in either a solution, a colloidal dispersion, a
suspension, or an emulsion.These mixtures differ from each other based on the size or
solubility of their solutes.

10. Uses of water in food preparation ….
Universal solvents ….
Solution
• In a solution, the molecules of the solute are so small that they completely dissolve and will not
precipitate from their fluid medium. They cannot be separated by filtering, but can sometimes be
removed by distillation. If a substance is able to enter into a solution by dissolving, it is considered to
be soluble.
• Much of what people perceive as the taste of foods depends on the formation of solutions with solutes
in foods such as sugars, salts, acids, and other flavor compounds, and their resulting enhanced ability
to attach to flavor receptors. Water also forms solutions with minerals and water-soluble vitamins (B
complex and C).

11. Uses of water in food preparation ….
Universal solvents ….
Colloidal dispersions
• Not all particles dissolve readily or homogeneously. Some particles, called colloids (e.g.,
proteins, starches, and fats) never truly dissolve in a solvent, but remain in an unstable
colloidial dispersion. Unlike solutes in solutions, which completely dissolve, colloids do not
due to their large size.
• Examples of different types of dispersions include a solid in a liquid, a liquid in another
liquid (salad dressing) or solid (jam, gelatin, cheese, butter), and a gas that can be
incorporated into either a liquid (egg white or whipped cream foams). Two types of
dispersions are suspensions and emulsions.

12. Uses of water in food preparation ….
Universal solvents ….
Suspension
Mixing cornstarch and water results in a suspension in which the starch grains float within the liquid.
Emulsion
• Another type of colloidal dispersion involves water-in-oil (w/o) or oil-in-water (o/w) emulsions.
Neither water nor fats will dissolve in each other, but they may become dispersed in each other,
creating an emulsion. Examples of food emulsions include milk, cream, ice cream, egg yolk,
mayonnaise, gravy, sauces, and salad dressings. These and other emulsions can be separated by
freezing, high temperatures, agitation, and/or exposure to air.

13. Uses of water in food preparation ….
Universal solvents ….
Suspension
Mixing cornstarch and water results in a suspension in which the starch grains float
within the liquid.
Emulsion
• Another type of colloidal dispersion involves water-in-oil (w/o) or oil-in-water (o/w)
emulsions. Neither water nor fats will dissolve in each other, but they may become
dispersed in each other, creating an emulsion. Examples of food emulsions include
milk, cream, ice cream, egg yolk, mayonnaise, gravy, sauces, and salad dressings.
These and other emulsions can be separated by freezing, high temperatures,
agitation, and/or exposure to air.

14. Carbohydrates
• Produced by photosynthesis in plants.
• The major source of energy from our diet.
• Composed of the elements C, H, and O.
6CO2 + 6H2O + energy C6H12O6 + 6O2
Photosynthesis
Respiration
glucose
Cn(H2O)n

15. Carbohydrates cover a wide range of natural compounds, such a starches,
glycogen and sugars, which are all based on monosaccharides.
Carbohydrates can be divided into three main groups:
• Monosaccharides;
• Disaccharides;
• Polysaccharides.

16. Polysaccharides
• Polymers of many monosaccharides units.
Amylose (20%)
• Starch
Amylopectin (80%)
• Glycogen (an energy storage in animals & humans)
• Cellulose (plant and wood structures).
(starch that stores glucose in plants such
as rice, potatoes, beans, and wheat - energy storage).

17. Properties of Starch
• Appearance and Solubility:
Starch is a white powder which is insoluble in cold water.
Hydrolysis breaks down starch:
Starch -> Dextrins -> Maltose -> Glucose
•

18. Properties of Starch
• Effect of Heat
Gelatinization (with water):
• Water penetrates the outer layers of granules and the granules begin to swell
when the temperature rises from 60 C to 80 C.
• Granules swell up to 5x the original size – mixture becomes viscous (thick).
• At 80 C the starch granules break up and disperse throughout the water.
• Long chain molecules unfold and the starch/water
mixture becomes more viscous.

19. Glycogen
• Carbohydrate only found in animals
Animals store glycogen in muscles and liver and
when required, it converts it to glucose which is broken down to
provide energy.
Glycogen, like Amylopectin, is composed of branched chains of
glucose units.

20. Glycogen
• Carbohydrate only found in animals
Animals store glycogen in muscles and liver and
when required, it converts it to glucose which is broken down to provide
energy.
Glycogen, like Amylopectin, is composed of branched chains of glucose
units.

21. Complex Polysaccharides
• These are long chains of different monosaccharide's joined
together and often with branches.
• Pectin
• Gums

22. Pectin
• Complex mixture of polysaccharides found in many fruits and some root
vegetables.
Apples and the peel of citrus fruits are particularly rich in pectin.
Main importance: Gelling Agent (e.g. jam making)
Pectin is broken down in fruit as fruit ripens – Jam will not gel well if
made from over ripe fruit.
For pectin to form a really good gel, 65% of it needs to be sugar.
pH affects gel strengths (pH 3.0-3.5). Lemon juice lowers this setting.

23. Gums
• Xanthan, arabic and guar – Produced by plants and are used in food
manufacturing as thickeners, stabilizers and gelling agents in foods.
• E.g. Ice cream, salad dressing and fruit pie fillings.

24. Carbohydrate in food
Many foods contain some carbohydrate but the amounts of sugars, starch and fibre
differ.
Sugars are naturally present in foods such as milk , fruits, vegetables and honey
Starch is present in foods such as potatoes, bread, rice and pasta.

25. Carbohydrate in food
Fibre is present in whole grains, fruits and vegetables, especially the skin
covering of seeds.
It is a mixture of substances (mainly complex carbohydrates) which cannot
be digested in the small intestine.

26. Carbohydrate and its functional properties in food products
Carbohydrates perform different functions in food products.
They:
• help cause the colour change of bread, toast and bakery products;
• contribute to the chewiness, colour and sweet flavour of caramel;
• thicken products such as sauces and custards.

27. Caramelisation
When sucrose (sugar) is heated above its melting point it undergoes a
physical change to produce caramel.
This happens more readily without water, however syrups will
caramelise with rapid heating.
This process is used extensively in the production of confectionary.
Overheating will cause the substance to become bitter and dark.

28. Gelatinisation
When starch is mixed with water and heated, the starch granules swell and eventually
rupture, absorbing liquid which thickens the mixture.
On cooling, if enough starch is used, a gel forms. This process is used in the production of
blancmange.

29. Other characteristics
Preserving
Sugar in high concentrations prevents the growth of micro-organism.
It is used extensively in the production of jam, marmalade and some
canned fruit. Sugar is an important ingredient in determining the
shelf-life of a product.
Flavouring
Sugar, e.g. sucrose, may be used to flavour many products such as drinks, cakes,
tomato sauce and confectionary. It supplies sweetness and mouth feel.

30. Other characteristics
Jelling
Some fruits, such as apples and blackcurrants, are rich sources of pectin. Pectin is used
as a jelling agent in the production of jam.