1 Daniel. 2 Plants need food and water 3 Animal needs food and water.
Food Physics. Water in Food Water has three states: Liquid, solid, & gas. In food water is either...
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Transcript of Food Physics. Water in Food Water has three states: Liquid, solid, & gas. In food water is either...
![Page 1: Food Physics. Water in Food Water has three states: Liquid, solid, & gas. In food water is either added, removed, or altered in food (typically altered)](https://reader036.fdocuments.net/reader036/viewer/2022082710/56649e6f5503460f94b6d12b/html5/thumbnails/1.jpg)
Food Physics
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Water in Food
• Water has three states: Liquid, solid, & gas.
• In food water is either added, removed, or altered in food (typically altered)
• Ice floats due to hydrogen being spaced further a part as compared to the usual alignment.
• “Tetrahedron” is the 4 hydrogen bonds that form between water molecules.
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Interfacial Tension
• Water has different forces– 1. Attraction to other water molecules.– 2. attraction of water molecules for the
surface they may be on.– 3. To each other when against air.
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Osmosis
• Osmosis—Flow of water molecules from a place of greater concentration to a place of lesser concentration.
• Example-All vegetable wilting.
• Why are vegetables kept wet at stores?
Turgor—Water pressure in cells to keep things like vegetables crisp..
Salt from dressings will take water out.
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• Osmosis takes place in all canned fruits.
• Microbes have a water concentration of 80% where salt and sugar at 40-50%.
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Water Activity
• Controlling water controls microbes.• Water activity is indicated by aw.• Common water activity formula is:Aw = Equilibrium relative humidity/ 100
Equilibrium Relative Humidity—reached when a food’s rate of water loss in the environment equals its rate of water absorption in the environment.
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• Definition of mole :1) The quantity of a substance whose mass, in grams, is equal to its formula weight. Ex: Iron (Fe) has a formula, or molecular, weight of 55.85 grams. One mole of iron would be 55.85 grams.
2) Avogadro's number: 6.022 x 10^23
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Moles in Water
• Water has a concentration of 55.6 moles.
• If 1 mole is added to 1000 grams of water it now contains 56.5.
• Water Activity is the number of water molecules relative to the total number of molecules present. What would the water activity be in this example:
![Page 9: Food Physics. Water in Food Water has three states: Liquid, solid, & gas. In food water is either added, removed, or altered in food (typically altered)](https://reader036.fdocuments.net/reader036/viewer/2022082710/56649e6f5503460f94b6d12b/html5/thumbnails/9.jpg)
• 55.6/56.6 = .982 which would mean that for every 1000 molecules of solution there is 982 water molecules.
• In this case humidity inside the food would be 98%.
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Proteins
• Proteins function around water.• Water & protein have a “synergistic”
relationship (mutual cooperation)• Proteins always have a single layer of
water around them.• The water layer is the reason why freezing
does not kill microbes.• Even freeze dried foods have a water
layer.
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pH Adjustment
• pH will change the water molecules around protein.
• Let’s take a closer look at this concept.
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• You have made curds and whey.
• The acid in vinegar stopped the amino acids from bonding which caused the curds. Basically the proteins collapsed out of the milk.
• Precipitate is the fall out materials technical name, something that comes out of a solution that has evaporated.
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Lipid Physics
• What is the difference between vegetable oil and shortening?
• Hydrogenation
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Role of Heat
• Oil is not passive in cooking.
• Melting Point-temp where fat becomes liquid.
• Smoke Point-release of volatile molecules.
• Flash Point-ignitable vapor, volatile molecules are heavier.
• Fire Point-oil will burn
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Hydrophobic
• Oil and water
• Immiscibility-inability of two liquids to mix.
• Water is dipolar (energy) and fat that has triacylglyceriades are not. Again with pH this does change in proteins that have lipids. Proteins will bond but the fat will not.
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Carb Physics
• Carbs absorb large amount of water in the polymer stage.
• A polymer is a large molecule (macromolecule) composed of repeating structural units typically connected by covalent chemical bonds.
• In this case the C, H, and O with oxygen holding various groups together.
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Starches
• Cold water little solubility, hot water it is spaghetti time.
• Starch gels, forms a viscous (does not flow well) liquid.
• Pudding is a common example due to the polysacs.
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Pectins• A polysaccharide extracted from the cell walls of
plants, especially of fruits; under acidic conditions it forms a gel. It is often used in processed foods, especially jellies and jams where it causes thickening (setting).
• Pectins are linear polymers of galacturonic acid joined by bonds that allow side sugar chains. Hydrogen during cooling bonds to lead to gels.
• Pectin has two gels: high methoxyl content and low content methoxyl.
• Both used to make jelly, one high sugar the other not.