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WATER
BEVERAGES
FUNCTIONS
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Solvent or dispersing agent
Ionization of acids and bases
Enzyme-catalyzed and chemical reactions
Heating, cooling medium
Cleansing agent
Gelatinization of starch
Tenderness of meat
Spoilage & micro-organisms
All food processing techniques involve water
STRUCTURE
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Hydrogen bonds between water molecules
Weak bonds
Bonds break and reform – dynamic
Coordination number – average number of nearest neighbors
Liquid state has smaller bond angle than solid state
STATES OF WATER
• Ice is lowest energy state, steam the highest
• Energy is lost as water cools
• Bond angle increases as water cools causing increase in volume –
significant in freezing of food
• Ice less dense than water
TERMS
• LATENT HEAT OF FUSION – removal of heat
• LATENT HEAT OF VAPORIZATION – heat to change liquid into a
gas
• SUBLIMATION – from frozen to gaseous state without becoming
liquid
CHANGE BOILING POINT
• Boiling point is temperature at which vapor pressure just exceeds
atmospheric pressure
• Atmospheric pressure decreases with increase in altitude
High altitudes vapor pressure is high 
Lower temperature for boiling
Cook foods longer
FREEZING POINT
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Solutes lower temperature of freezing
Sucrose and salt
1 mole/liter  decrease 0.52C
1 mole sucrose  boiling point at 100.52C
1 mole salt boiling point at 101.4C
Salt ionizes 2x the effect on freezing point
Salting for flavor no effect
USE OF ATMOSPHERIC PRESSURE
• PRESSURE COOKER OR CANNER- atmospheric pressure increased
by steam
more energy needed to make water boil
Higher temperature = faster cooking
• VACUUM PAN - make juice concentrates or preserves
Lowered pressure-less energy, water boils at lower temperature
evaporation occurs quickly less loss of volatile flavors
DISPERSING MEDIUM
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SUBSTANCES DISSOLVED, DISPERSED, OR SUSPENDED
SOLUTIONS
IONIC-with salts, acids, bases
MOLECULAR-with sugars-solubility increases as temperature
increases
COLLODIAL DISPERSIONS
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SOL - liquid that pours
GEL - 2 phase system - solid with liquid dispersed
Molecules too large to form solution - cooked starch, cellulose, pectins
Unstable - must be stabilized in food products
Important to food science
SUSPENSIONS
• Too large for colloidal dispersions
• Settle out
FREE, BOUND, ENTRAPPED WATER
• FREE - extracted by squeezing, cutting, pressing
• BOUND - cannot be easily extracted, structural bonding to other
molecules – lacks flow properties
• ENTRAPPED - immobilized in capillaries or cells
WATER CHARACTERISTICS
• PURITY- absence of harmful bacteria
• CEMICALLY IMPURE-air (nitrogen, oxygen, carbon dioxide)
• HARDNESS- measure in ppm or grains,
temporary - softens as boils, precipitates out
permanent - need chemical softeners
• SOFTNESS-no mineral salts, some organic matter
COFFEE
PROCESSING
• Beans – picked, partially dried, hull removed, roasted and ground
immediately or exported
• Some shipped as whole beans
• Processed wet or dry – dry more expensive but yields better flavor
ROASTING
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Steam bubbles form in green coffee bean
Increase porosity, makes high surface area
Makes bean light
Carbon dioxide fills holes left by steam, gives bouyancy
Oily surface due to breakdown of fats during heat of roasting
Color from green  brown
ROASTING
• Non-enzymatic browning – sugars + amino acids melanin pigments
• Carmelization of sugars – increases sweetness, increases dark color
• Carbon dioxide – gives “zest”
GRINDING
• Creates more surface area for hot water to extract compounds for
flavor, color, aroma
• Type of grind depends on equipment being used
CHEMICAL COMPOUNDS
VOLATILE COMPOUNDS
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Roasting creates volatile compounds
Unstable – flavor deteriorates rapidly
Responsible for aroma
Easily react with oxygen rancidity
BITTER SUBSTANCES
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Bitterness due to organic acids
Chlorogenic acid
Polyphenol compounds
Caffeine
Never boil coffee – temperatures >2000F increase solubility of organic
acids making coffee unpalatable
METHYLXANTHINES
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Caffeine and theobromine
Amount of caffeine depends on brewing method
Caffeine – stimulant on CNS, diuretic, coronary artery dilator
Theobromine – also found in cocoa and chocolate, less stimulating
than caffeine
DECAFFEINATION
• Soak green beans in steam or water
• Extract caffeine from water with a solvent such as methylene chloride (limited
by FDA) or ethly acetate
• May remove by filtering water through charcoal filter
• Removes 97% of caffeine
• Food scientists working on caffeine free bean through genetic engineering
INSTANT COFFEE
• Dehydrated coffee beverage
• Dried - fine spray of concentrate to hot air
• Frozen concentrate - then expose to vacuum (ice to vapor without
melting)
QUALITY
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Good flavor
Good aroma
Limit extraction of bitter substances
Freshness
Rich brown color, brightness
Sweetness
TIPS
• Pack in vacuum cans to preserve flavor and aroma
• Fresh, cold tap water for brewing
• Do not boil water because dissolved oxygen will escape  flat taste to
coffee
• Boiling causes loss of volatile compounds
• 190-2000F best brewing temperature
TEA
PROCESSING
• Leaves are picked
• Withered, rolled, oxidized, fired
• Oxidizing – fermenting – natural enzymes released by rolling cause
leaves to become darker
• Firing dries leaves, inactivates enzymes and decreases leaf moisture
TYPES OF TEA
• Green tea – leaves steamed or heated to destroy enzymes that oxidize
polyphenols, leaves dried
• Oolong tea – leaves repeatedly rolled and dried to oxidize polyphenols
• Black tea – leaves rolled and exposed to air, enzyme oxidizes
polyphenols, darkening the leaves
COMPOSITION
POLYPHENOLIC COMPOUNDS
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Catechins and flavonols
Varies depending on type of tea
Responsible for the flavor and strong astringency of tea
Green tea has greatest amount  metallic taste
Possible antioxidant, anticarcinogenic properties
Bind iron and prevent some from being absorbed from intestinal tract
OTHER COMPOUNDS
• Methxylxanthines-caffeine and theobromine in smaller quantities than
coffee
• Theaflavins – help decrease bitterness, give color
• Tannins – contribute to astringency and give reddish-brown color
GRADES OF TEA
Named by size of leaf
• Orange Pekoe
• Pekoe
• Souchonge
• Broken orange pekoe in tea bas
• Quality decreases as size increases
TIPS
• Heat water to just below boiling
• Do not steep too long – extracts bitter compounds, increase
astringency, elevate caffeine
CHOCOLATE AND COCOA
• Suspensions
• Pods open - seeds exposed so they ferment
• Enzymes - convert proteins to polypeptides and amino acids; sucrose to glucose
and fructose
• Dry beans then roast
• High roasting temperature and moisture cause hydrolysis of protein to react with
sugarsMaillard reaction - gives aroma and color