Introduction to Food Science
Water
The Universal
Chemical
Exits in Three States
1,Gas – Steam
2,Liquid – Water
3,Solid – Ice
Heat Transfer is
necessary for conversion
Conversion from:
Water Vapor to Liquid
Liquid to Solid
Heat must be removed =
Exothermic
Liquid to Vapor
Solid to Liquid
Heat must be supplied =
Endothermic
Chemical Nature of Water
Covalent bonds between
O
H H
Chemical Nature of Water
Covalent bonds between
O O
H H H H
O O
H H H H
Each molecule may be connected to 4
other molecules
Natural Water
is a solution.
-Trapped in capillaries of food
-Water holding capacity
Water activity aw
Water
Water activity (aw)
1.00 – 0.95 Fresh Meat,fruit,vegetables
0.95 – 0.90 Processed cheese,baked goods
0.90 – 0.80 Aged cheese,and jams
0.80 - 0.70 Molasses,dried figs
0.70 - 0.60 Dried Fruit and corn syrup
0.60 - 0.50 Chocolate,honey,noodles
0.20 Dried milk,dried vegetable
Food Dispersions
Solutions,Homogeneous
mixture of molecules and
or ions of different
substances one of which
is water.
Food Dispersions
Solutions:
Sugar and Water
Sodium Chloride and Water
Solubility is the amount of solute
that can be dissolved in a given
amount of solvent at a given
temperature
Concentration- is the amount of
the solute dissolved in a specific
solvent
Saturated Solution - contains as
much solute as can be dissolved at
a given temperature.
Vapor Pressure - Pressure
exerted by the gas above the
liquid when equilibrium exists
The greater the concentration of
solute,greater the reduction in
vapor pressure
Boiling Point- The temperature
at which the vapor pressure
equals the external pressure,
Volatile solutes- Lower the
boiling point because of their
contribution to vaporization
Freezing point – Solutes despress
the freezing point of water by
disrupting structure,
Osmotic Pressure –
Osmosis is the passage of water
molecules through a semi-
permeable membrane.
Colloidal Dispersions
Sol - water is the continuous phase
Gel - liquid-in-solid
Emulsion – liquid-in-liquid
Water
The Universal
Chemical
Exits in Three States
1,Gas – Steam
2,Liquid – Water
3,Solid – Ice
Heat Transfer is
necessary for conversion
Conversion from:
Water Vapor to Liquid
Liquid to Solid
Heat must be removed =
Exothermic
Liquid to Vapor
Solid to Liquid
Heat must be supplied =
Endothermic
Chemical Nature of Water
Covalent bonds between
O
H H
Chemical Nature of Water
Covalent bonds between
O O
H H H H
O O
H H H H
Each molecule may be connected to 4
other molecules
Natural Water
is a solution.
-Trapped in capillaries of food
-Water holding capacity
Water activity aw
Water
Water activity (aw)
1.00 – 0.95 Fresh Meat,fruit,vegetables
0.95 – 0.90 Processed cheese,baked goods
0.90 – 0.80 Aged cheese,and jams
0.80 - 0.70 Molasses,dried figs
0.70 - 0.60 Dried Fruit and corn syrup
0.60 - 0.50 Chocolate,honey,noodles
0.20 Dried milk,dried vegetable
Food Dispersions
Solutions,Homogeneous
mixture of molecules and
or ions of different
substances one of which
is water.
Food Dispersions
Solutions:
Sugar and Water
Sodium Chloride and Water
Solubility is the amount of solute
that can be dissolved in a given
amount of solvent at a given
temperature
Concentration- is the amount of
the solute dissolved in a specific
solvent
Saturated Solution - contains as
much solute as can be dissolved at
a given temperature.
Vapor Pressure - Pressure
exerted by the gas above the
liquid when equilibrium exists
The greater the concentration of
solute,greater the reduction in
vapor pressure
Boiling Point- The temperature
at which the vapor pressure
equals the external pressure,
Volatile solutes- Lower the
boiling point because of their
contribution to vaporization
Freezing point – Solutes despress
the freezing point of water by
disrupting structure,
Osmotic Pressure –
Osmosis is the passage of water
molecules through a semi-
permeable membrane.
Colloidal Dispersions
Sol - water is the continuous phase
Gel - liquid-in-solid
Emulsion – liquid-in-liquid
