Water in foods
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| Water content of fruits&vege | 80-90%
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| Water content of muscle foods | 50-70%
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| Water content of processed foods | less than 40% in order to improve shelf life
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| Importance of water in foods | controls growth of microbes, affects chemical and enzymic reactions, affects physical properties - texture, affects stability and function of food chemicals (esp proteins and polysaccharides)
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| Water also | acts as a trasport medium and enables chemical and biochemical change
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| Structure of Water | hydrogen bonds continuously made and broken rapidly which makes it a non-permanent liquid structure
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| Each water molecule hydrogen | bonds to as many as four other water molecules at max
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| In liquid water, molecules have lots of energy | rotational energy, vibrational energy, kinetic energy
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| When temperature is lowered | all energies slow down and water molecules come together to form nuclei
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| Water molecules attach themselves to the nuclei | to form ice crystals
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| In ice each water molecule is bonded to | four other water molecules
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| freezing pt is below | 0 degrees fahrenheit
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| Water content of fruits&vege | 80-90%
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| Water content of muscle foods | 50-70%
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| Water content of processed foods | less than 40% in order to improve shelf life
🗑
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| Importance of water in foods | controls growth of microbes, affects chemical and enzymic reactions, affects physical properties - texture, affects stability and function of food chemicals (esp proteins and polysaccharides)
🗑
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| Water also | acts as a trasport medium and enables chemical and biochemical change
🗑
|
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| Structure of Water | hydrogen bonds continuously made and broken rapidly which makes it a non-permanent liquid structure
🗑
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| Each water molecule hydrogen | bonds to as many as four other water molecules at max
🗑
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| In liquid water, molecules have lots of energy | rotational energy, vibrational energy, kinetic energy
🗑
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| When temperature is lowered | all energies slow down and water molecules come together to form nuclei
🗑
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| Water molecules attach themselves to the nuclei | to form ice crystals
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| In ice each water molecule is bonded to | four other water molecules
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| Freezing pt is below | 0 degrees fahrenheit
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| What are the roles of water in food chem? | 1) to interact/bind with food components, 2) to transport molecules/reactants to facilitate chemical rxns, 3) to take part in reactions as a reactant
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| Gels | are formed when protein or polysaccharides interact and entrap water
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| Water interacts with | itself, micromolecules, macromolecules
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| Water activity (Aw) | is a measure of the extent to which the water in a substance has the properties of pure, unbound water. Its value is expressed in the range 0-1
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| Aw of 0 | when molecules are completely bound to each other like ice
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| Aw of 1 | when water is absolutely pure
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| Normal bacteria growth | Aw = 0.91
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| Normal yeasts | Aw = 0.88
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| Normal molds | Aw = 0.80
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| Halophilic bacteria (salt loving) | Aw = 0.75
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| Xerophilic molds | Aw = 0.65
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| Osmophilic yeasts (sugar loving) | Aw = 0.60
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| Microbiologically Stable Aw | example sugar syrup with 80% sugar, 20% water and Aw of 0.60
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| Microbiologically Unstable Aw | example sugar syrup with 60% sugar, 40% water and Aw of 0.95
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| High sugar activity | reduces water activity
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| Low Aw | lipid oxidation during food storage
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| High Aw | chemical rxn and microbial growth during food storage
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| To control water activity we can use | drying, freezing, adding salts and sugars
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Created by:
lindarim
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