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105 Cards in this Set
- Front
- Back
Water can be used in...
|
-beverages
-processing -harvesting -heating/cooling |
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Water Structure
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-H2O
-polar -forms hydrogen bonds |
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Free Water
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-bulk water
-solvent water |
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Bound Water
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-no removable
-hindered mobility -first water molecules to ineract with functional groups of solutes |
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Water Activity
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-measure of vapor pressure of water molecules in the space above a food in a closed container
-indicates the degree of available water |
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aldose
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aldehyde group
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Ketose
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Ketone group
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Pentose
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five carbons
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Hexose
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six carbons
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Carbohydrates in Water
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-very soluble in water
-form hydrogen bonds with water -polar |
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Functional Groups in Carbs
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-hydroxyls
-aldehydes -amines -acids -Phosphates |
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Simplest Carbohydrate
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Glucose
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Reducing Sugars
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sugars that contain a free aldehyde or ketone
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Aw of ideal pure water
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1
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Aw of ideal food with no water
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0
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Water Activity equation
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Aw= P/P0
p-paretial vapor pressure of water p0- vapor pressure |
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Water Sorption Isotherms
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tell the amount of water absorbed onto a component
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Desorption isotherm
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start with a smaple that is very wet and see how much moisture is lost
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sorption Hysteresis
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discrepancis between the adsorption and desorption data
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Aw values can be controleld by...
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types of salt
ex. hotdog experiment |
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Moisture Migration
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mixing ingedients with different moisture contents will cause moisture migration
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Moisture Migration is driven by...
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Aw potential not moisture content
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Humectants
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solutes that have a higher affinity to absorb water
-helps maintain soft texture at low Aw |
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Ways to lower water activity
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-add solutes like sodium chloride or sugars
-dehydration |
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intermediate Moisture foods (IMF)
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created by addition of solutes to lower water activity
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Tg
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temperature range at which amorphous or non crystalline solid changes from hard and brittle to soft and rubbery
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Maillard browning reaction
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-non oxidative browning
-consists of amino acid and a reducing sugar -aromas and flavors are formed -leads to undesirable brown color or to desirable colre (ex. bread crust) |
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Lipid oxidation can lead to:
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-off-flavors
-changes in color or texture -reduced shelf-life -impairment of nutritional quality |
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Enzymatic Reactions
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-water acts on the structure of the enzyme and substrate
-water may interrupt hydrogen bonding and change protein structure -water facilitates diffusion of substrates and catalysts for reaction -water may become a part of reaction (ex. hydrolysis) |
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Most abundant Carbohydrate
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cellulose
|
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Sweeteners
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-sucrose, fructose, glucose
-sugar alcohols also used to reduce calories |
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Naturals gums
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-water soluble polysaccharides
-extracted from land or marine plants -contributes viscosity or gelling ability |
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Guar Gum
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-endosperm polysaccharide of Cyamopsis tetragonolobus
-grown in india -hydrates to rapidly produce highly viscous solutions -viscosity no affected by changes in pH |
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Locust Bean Gum
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-derived from the seed of the carob tree, Ceratonia siliqua
-grows near Mediterranean -provides body, smoothness, and chewiness |
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Gum Arabic/Acacia
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-produced as teardrop shaped from the bark of Acacia trees
-dissolves in water -low viscosity solutions -decreases sugar crystallization in candies -aids in formation and maintenance of small ice crystals in frozen desserts |
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Gum Tragacanth
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-collected from bushy shrubs in Iran, Syria, and Turkey
-occurs in bark wounds -found in salad dressings and sauces -excellent stability in heat and acidic conditions |
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Agar
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-bacteriological culture medium
-obtained from red marine algae in Japan -remains stable at temps above the initial gelation point -reduces syneresis -provides desirable texture in frozen desserts -provides stability in cheeses -retards staling in baked goods |
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Carrageenan
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-extracted from seaweed
-when cation is K+ a firm gel is produced -when cation is Na+ the polymer is cold water soluble and non-gelling -stable above pH 7 -degrades rapidly below pH 5 -added to chocolate milk to reduce chocolate particle precipitationg by forming weak get with milk protein |
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Alginates
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-extracted from brown algae
-forms gels at room temp in presence of Ca++ ions -provides body, texture, and resistance to ice crystals in frozen desserts -used in French salad dressing for thickening and emulsion |
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Dextrans
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-product of microbial biosynthesis
-increases moisture retention in candies -inhibits sugar crystallizaation and crystal growht -gelling agent in gum and jelly candies -water crystallization inhibitor -cant be used in foods in US or Europe |
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Xanthan Gum
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-cellulose chain with oligosaccharide groups
-soluble in hot or cold water -produces highly viscous solutions at low concentration -thermally stable -acidity have little effect on viscosity -used in beverages to enhance mouth feel and flavor release |
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Gellan
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-produced under aerobic condition
-requires Na+, K+, Ca++, or Mg++ to form a gel -useful where high gel strength is required |
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Carbohydrates
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-major engery source for animals
-help provide structure -fewer calories than lipids -sweeteners -provides texture -thickeners -dietary fibers -carbon sources |
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Most important ketose
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fructose
|
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Sucrose formation
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condensation reaction between glucose and fructose
|
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Most abundant Carbohydrate
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D-glucose
|
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Monosaccharides
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-smallest sugars
-building units of other carbs -3-9 carbons |
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d-sugars
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-sugar has -OH group on the right hand side
-most sugars in nature are D sugars |
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L-sugars
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sugar has first -OH group on left hand side
|
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Aldose
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-sugar containing an aldehyde
-ex. glucose, galactose, mannose |
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Ketose
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sugar containing a ketone
|
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glucose isomerase
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enzyme which helps catalyze the reaction that converts glucose to fructose
|
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Epimers
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differ in one configuration of a single asymmetric center
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Hemiacetal
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ring structure formed throug ha rxn between the aldehyde group and an -OH of the sugar
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Hemiketal
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ring sturcture fromed thorugh a rxn between the ketone group and an -OH of the sugar
|
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five member rings
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kinetically favored
|
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six member rings
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thermodynamically favored
|
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glycaric Acids
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sugars with 2 carboxyl groups (one on each end of sugar)
|
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Oligosaccharides
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-condensation products of monosaccharids
-monosaccharides units connected by glucosidic linkages -contain 2-10 sugar units -ex. Disaccharides |
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Disaccharides
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-smallestt oligosaccharide
-2 monosaccharide units -ex. sucrose (glucose and Fructose) -maltose (2 glucose units) |
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Trisaccharides
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oligosaccharides containing three sugar units
-ex. maltotirose (3 glucose units) |
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Cyclodextrins
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-cyclic nonreductin D-glucopyranosyl oligomers
-consist of 6,7, and 8 glucose units |
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Reducting sugars
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-any sugar having an aldehyde or ketone group that id readily converted into a carboxylic group by Cu or Ag
-rxns can easily be detected by color changes -ex. glucose, fructose, maltose, lactose |
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Polysaccharides
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-consist of more than 10 sugar units
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Homo-polysaccharide
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-glycan composed of a single monosaccharide unit with one or more types of glycosidic linkages
-ex. starch, glycogen, cellulose |
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Hetero-polysaccharide
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-glycans compose of more than one type of monosaccharide
-ex. gums, dietray fibers, pectinic substances |
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Starch
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-second largest biomass
-hundred of glucose units -major form of energy in plants |
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Starch is stored in...
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seeds, roots, fruits ,and leaves
|
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Starch consist of...
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amylose and amylopectine
|
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amylose
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-linear molecule containing tons of glucsoe units
-alpha 1-4 linkages |
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Amylopectin
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-highly branched
-alpha 1-6 linkages -cluster structure -phosphate derivative |
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Starch Categories
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-waxy
-normal -high-amylose |
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Starch granules
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-Maltese cross
-center of cross is know as hilum, organic center -once gelatinization takes place the maltese cross disappears -insoluble in cold water -absorb cold water and sweel -absorb hot water, swell, rupture, collapse, form a paste |
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Cellulose
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-present in vegetables and fruit
-cannot be digested by humans -glcose units with beta 1-4 linkages -gives tough texture to foods -linear structure prompts crystallization |
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Gums
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-provide thickening and stabilizing effects to food
-isolated from plant seeds, plant exudates, sea wees, microorganisms |
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Pectin Substance
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-can form two types of gels
-High DE pectin and Low Methoxy Pectins |
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High DE Pectins
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form gels at acidic pH and in the presence of a high concentration of sucrose
|
|
Low methoxyl Pectins
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-require divalent cations
-can be fromed without sugar and over a wide pH range -gels are brittle and less elastic |
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Hemicelluloses
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-group of polymers found in cell wall of plants
-good water binging capacity -not starch or cellulose |
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Pentoses
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have five carbons
|
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Hexoses
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have six carbons
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Carbohydrate in water
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-very soluble in water
-form hydrogen bonds with water -polar |
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complete oxidation of sugars leads to...
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CO2 and water
|
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Color Reactions
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-acids and formation of furfural and 5-hydroxymethylfurfural products will react with phenols or amines to form colored compounds
|
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Sugar Derivatives
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-amino sugars
-deoxy sugars -sugar acids -sugar alcohols -acetylated or methylated sugar |
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Fructooligosaccharides (FOSs)
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-oligomers of sucrose with additonal fructose glucosidic linkage to fructose part of sucrose
|
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Food Gums
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-stabilize
-emulsify -suspend -foam -gel -bind -form films -viscosity -texturize |
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Commercial uses of gum
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-thermal gelation of methylcellulose
-edible film production -suspension of particles in liquid -structural foams -binding in veggie patties |
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Glycogen
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animal storage
|
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Waxy Starches
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long bodied, stringy
|
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Non-waxy Starches
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short bodied, clean cuts
|
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Starch Forms
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-A and B forms
-A form is most common -dffer in physical properties |
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Starch gelatinization
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-granule swelling
-loss of birefringence and crystallinity -leaching of amylose -endothermic -glass transiton to rubbery state |
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Gelatinization
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-collapse of molecular order within the starch granule
-point of initial gelatinization and range over which it occurs is governed by starch concentration |
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Pasting
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-dissolution of starch
-granular swelling -exudation of molecular components from granule |
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Retrogradation
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-process when molecules begin to reassociate in an ordered structure
-crystalline order appears -starch becomes less soluble -transition from amorphous to crstalline state |
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Amylose and Retrogradation
|
-amylose associates parallel to one another
-affinity for water is decreased -size increase -precipitate forms |
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Modified Starches
|
-crosslinking of chains
-depolymerization -pre gelatinization -addition of functional groups |
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Unmodified Starches
|
clear cohesive pastes
|
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Crosslinked Starch
|
-distarch phosphate esters
-decrease rate and degree of granule swelling -more stable in high temps and low pH -mroe viscous |
|
Phosphate ester
|
-monoester phosphate and diester phosphate modified starch
-decrease gelatinization temp -increase clarity -stabilizes against retrogradation -increases freeze-thaw stability |
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Alkenyl Succinate Esters
|
-hydrocarbon chain
-emulsion stabilizers |
|
Hydroxyproply starch
|
-decrease gelatinization temp
-clear paste -do no retrograde -thicken |
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Dietary Fiber
|
-resistant to mammalian digestive enzymes
-chemically defined by solubility |
|
Categories of Dietary Fiber
|
-structural polysaccharides
-structural non polysaccharides -non structural polysaccharides |