FOOD 2010 Chapter Notes - Chapter 4: Glass Transition, Water Activity, Miscibility

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Chapter 4: Food Chemistry 1, Functional Groups and Properties, Water,
and Acids
4.1 The Nature of Matter
-its a review of Chem
4.2 Chemical Reactions in Food
-review of Chem
4.3 Functional Groups
-review of Chem
4.4 The Chemical and Functional Properties of Water
-solvation and dispersing agent
-food molecules can form H-bonds with water meaning that they can be dispersed or dissolved
-this means that they are soluble
-hydrophilic compounds (can easily H-bond)
-Hydration is process by which water molecules surround and interact with solutes by acting as a
solvent
-can disperce amphiphilic agents (part hydroscopic, part hydrophobic)
-micelles are formed
-water activity and moisture
-moisture: amount of water present in a food relative to all the solid constituents and non- water
liquids
-free water: lightly entrapped, so easily pressed from food matter
-absorbed water: associates by layers via intermolecular H-bonds around hydrophilic food
molecules
-bound water: (water of hydration) tight chemically bound situations [ in crystalline structure]
-aw: measure of the availability of water molecules to enter into microbial, enzymatic, or chemical
reactions.
-water as a component of emulsions
-immiscible with fat
-thus emulsifier is needed if need to have 1 continuous phase
-water and heat treatment
-important vehicle for heat transfer in foods during processing and preparation
-water acts as a conductor of thermal energy to food molecules, process = heat transfer
-water as an ingredient
-can have repercussions as it can
-act as solvent
-change state with temperature changes
-exhibit motion within a food system
-in frozen foods, stabilizing movement of water is desirable for better quality
-water as plasticizer
-lowers glass transition temperature (To @ which change in physiochemical state and the mobility of
the water and polymer molecule constituents of a food occurs)
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Document Summary

Food molecules can form h-bonds with water meaning that they can be dispersed or dissolved. Hydration is process by which water molecules surround and interact with solutes by acting as a solvent. Can disperce amphiphilic agents (part hydroscopic, part hydrophobic) Moisture: amount of water present in a food relative to all the solid constituents and non- water liquids. Free water: lightly entrapped, so easily pressed from food matter. Absorbed water: associates by layers via intermolecular h-bonds around hydrophilic food. Bound water: (water of hydration) tight chemically bound situations [ in crystalline structure] Aw: measure of the availability of water molecules to enter into microbial, enzymatic, or chemical reactions. 4. 4 the chemical and functional properties of water. Thus emulsifier is needed if need to have 1 continuous phase. Important vehicle for heat transfer in foods during processing and preparation. Water acts as a conductor of thermal energy to food molecules, process = heat transfer.

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