Introduction to Food Science Chapter 6 Penfield and

Exits in Three States Gas – Steam 2. Liquid – Water 3. Solid –

Heat Transfer is necessary for conversion Conversion from: Water Vapor to Liquid to Solid

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 H H H Each molecule may

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

Water activity (a ) w 1. 00 – 0. 95 – 0. 90 –

Food Dispersions Solutions: Homogeneous mixture of molecules and or ions of different substances one

Food Dispersions Solutions: Sugar and Water Sodium Chloride and Water

Solubility is the amount of solute that can be dissolved in a given amount

Vapor Pressure - Pressure exerted by the gas above the liquid when equilibrium exists

Boiling Point- The temperature at which the vapor pressure equals the external pressure. Volatile

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

Osmotic Pressure – Osmosis is the passage of water molecules through a semipermeable membrane.

Colloidal Dispersions Sol - water is the continuous phase Gel - liquid-in-solid Emulsion –

Slides: 20

Download presentation

Introduction to Food Science Chapter 6 Penfield and Campbell 1990

Water The Universal Chemical

Exits in Three States Gas – Steam 2. Liquid – Water 3. Solid – Ice 1.

Heat Transfer is necessary for conversion Conversion from: Water Vapor to 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 H H H Each molecule may be connected to 4 other molecules

Natural Water is a solution.

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

Water activity (a ) w 1. 00 – 0. 95 – 0. 90 – 0. 80 - 0. 70 - 0. 60 - 0. 50 0. 20 Fresh Meat, fruit, vegetables Processed cheese, baked goods Aged cheese, and jams Molasses, dried figs Dried Fruit and corn syrup Chocolate, honey, noodles 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 semipermeable membrane.

Colloidal Dispersions Sol - water is the continuous phase Gel - liquid-in-solid Emulsion – liquid-in-liquid