Unformatted text preview: uch as in fruit juices.
s Boiling of Water
At sea level 5 lb = 109C s 15 pounds = 121C s Principle in food industry used to destroy microorganisms.
s Factors affecting the Boiling Point of Water
s  Salts and Sugars. Dissolved substances elevate the boiling point and depress the freezing point of water. s They dilute the water molecules. Addition of Sugar
Amount of Sugar
s s s s 200g 400 g 600 g 800 g Decrease in freezing Point (C). 1.09 2.18 3.26 4.35 Factors affecting the boiling point of Water.
 Colligative Properties: Affect both boiling point and freezing point. s Water activity s Osmotic Pressure s Boiling Point s Freezing Point.
s Addition of Salt
Salt dissociates into two ions and has a double effect. s NaCl -- Na + 1 + Cl -1 s Principle used in the preparation of ice cream.
s Water in Food Preparation
Communities provide safe water s Bottled water companies make a lot of money s Hard water (Ca and Mg carbonate) s They precipitate out and can be seen in pan. " temporarily hard water" s Ca and Mg sulfate create "permanently hard water"
s Water in Foods
s Strong influence in: s Stability of Foods s Chemical Reactions s Bacterial growth Free and Bound Water
s Free water s Part of water is separated from other constituents. s Runs out when fresh fruits are cut s Much of water in fruits is free but unable to flow because is trapped by structural elements of food system. Bound Water
s Water that is bound to other substances and no longer exhibits flow properties and solvent capability associated with water. Bound Water
Water bound to other substances s No longer exhibits flow properties s Inability to be expressed from tissues s Inability to enter frozen state. s Bound to polar groups, starches, pectins, hemicellulose, gelatin and other proteins.
s Types of Water
Fenemma's definitions Type IV: Pure water Type III: Water in tissue membranes Type II: Hydrogen-bonded water into capillaries. Type I: Water adsorbed in monolayers on proteins and other components.
s Water Activity (Aw)
s Aw = Vapor press...
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- Fall '10
- Bound Water