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Introduction to Food Science

Introduction to Food Science. Chapter 6 Penfield and Campbell 1990. Water. The Universal Chemical. Exits in Three States. Gas – Steam Liquid – Water Solid – Ice. Heat Transfer is necessary for conversion Conversion from: Water Vapor to Liquid Liquid to Solid.

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Introduction to Food Science

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  1. Introduction to Food Science Chapter 6 Penfield and Campbell 1990

  2. Water The Universal Chemical

  3. Exits in Three States Gas – Steam Liquid – Water Solid – Ice

  4. Heat Transfer is necessary for conversionConversion from: Water Vapor to Liquid Liquid to Solid Heat must be removed = Exothermic

  5. Liquid to Vapor Solid to Liquid Heat must be supplied = Endothermic

  6. Chemical Nature of Water Covalent bonds between O H H

  7. 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

  8. Natural Water is a solution.

  9. Trapped in capillaries of food -Water holding capacity Water activity aw Water

  10. 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

  11. Food Dispersions Solutions: Homogeneous mixture of molecules and or ions of different substances one of which is water.

  12. Food Dispersions Solutions: Sugar and Water Sodium Chloride and Water

  13. 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 solventSaturated Solution - contains as much solute as can be dissolved at a given temperature.

  14. Vapor Pressure - Pressure exerted by the gas above the liquid when equilibrium existsThe greater the concentration of solute, greater the reduction in vapor pressure

  15. 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

  16. Freezing point – Solutes despress the freezing point of water by disrupting structure.

  17. Osmotic Pressure–Osmosis is the passage of water molecules through a semi-permeable membrane.

  18. Colloidal DispersionsSol - water is the continuous phase Gel - liquid-in-solid Emulsion – liquid-in-liquid

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