Carbohydrates functional properties

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Carbohydrates: Functional Carbohydrates: Functional PropertiesPropertiesNFS 360NFS 360

Basil K. DalalyBasil K. DalalyProfessorProfessor

Department of Health and Department of Health and Nutritional SciencesNutritional Sciences

South Dakota State UniversitySouth Dakota State University

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Carbohydrates: Functional Carbohydrates: Functional PropertiesProperties

Following is a listing of possible roles: Following is a listing of possible roles: flavor enhancer and sweetener flavor enhancer and sweetener flavor and color due to caramelization flavor and color due to caramelization

and browning reaction and browning reaction serve as water binders serve as water binders contribute to texture (starch viscosity)contribute to texture (starch viscosity) serve as a hygroscopic nature/water serve as a hygroscopic nature/water

absorption absorption

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Carbohydrates: Functional Carbohydrates: Functional PropertiesProperties

Yeasts grow on CHO in foodYeasts grow on CHO in food regulate gelation of pectin regulate gelation of pectin disperse molecules of protein or starch disperse molecules of protein or starch preservation preservation control crystallizationcontrol crystallization structure due to crystals structure due to crystals effect osmosis effect osmosis effect color of fruits effect color of fruits

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Important Characteristics of Sugars

Sweetness Solubility Hygroscopicity and Water binding

Reduces aw Humectancy H2O migration (moisture barrier)

The smaller, the better Formation of colors

Caramelization Maillard reactions

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Relative sweetness of various carbohydratesfructose 173

invert sugar* 120

HFCS (42% fructose) 120

sucrose 100

xylitol 100

tagatose 92

glucose 74

high-DE corn syrup 70

sorbitol 55

mannitol 50

trehalose (2 glucose units, C1-C1) 45

regular corn syrup 40

galactose 32

maltose 32

lactose 15

* invert sugar is a mixture of glucose and fructose found in fruits.

TagatoseTagatose

Tagatose, which is 92% as sweet as sugar (sucrose) with about a third of the calories, is currently being evaluated as a potential diabetes drug. Tagatose is a stereo-isomer of fructose

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SweetnessSweetness

Sucrose, glucose and fructose are Sucrose, glucose and fructose are the most common sweeteners in the most common sweeteners in nature. Glucose is always less sweet nature. Glucose is always less sweet than sucrose, whereas the sweetness than sucrose, whereas the sweetness of fructose is highly dependent on of fructose is highly dependent on temperature.temperature.

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Solubility Fru > Suc > Glu > Mal > Lac Temperature, Solubility True solutions. Saturated solutions. Supersaturated solutions. In making candies , solubility and ease of crystallization are key factors

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Hygroscopicity High number of OH groups.

Advantage: Solvation/ solubilization of sugars

Disadvantage: Caking and lumps

Fructose is the more hygroscopic.

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Caramelization Heat > 160°C (melting point) 1st step (Mild thermolysis)

Break down of glycosidic bonds Ring size alterations and Anomeric

shifts Formation of new glycosidic bonds.

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2nd step (Prolonged heating) Dehydration Introduction of double bonds in the

sugar rings Conjugated double bonds

Hexose hydroxymethylfurfural (HMF) Higher temp and higher pH=higher

reaction rate

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Crystalline forms of sugar: Closely packed in an organized pattern.

Table sugar: granulated sucrose Confectionary sugar Raw sugar

2-3 % impurities (further purification) Brown sugar

Molasses Crystalline glucose

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Important characteristics of sugars

Liquid forms Corn syrups

75% carbohydrate and 25% water Glucose, maltose and dextrins First stage of HFCS

Molasses <25% water and <5% ashes Sucrose, fructose and glucose

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Important characteristics of sugars

Maple syrup Evaporation of maple sap < 35% water Flavor comes from the evaporation process

Honey 17% water, 82.5% carbohydrates Fructose 38%, Glucose 31%, Maltose 7% and

Sucrose 2% Traces of minerals, vitamins and enzymes

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Polysaccharides Functions in Foods

Functions in Foods Properties and functions

Sugar units that formed them Type of glycosidic bonds Degree of branching

Dietary polysaccharides Insoluble and indigestible Structure to food (compactness, crispiness) Intestinal motility

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Water dispersible Thickening agents Viscosity used in 0.25-0.5%, indicating

their great ability to produce viscosity and to form gels

Gel forming ability Mouthfeel

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ViscosityViscosity, , Interaction PS-H2O depend on molecular size shape, function of rotations around the

bonds of glycosidic linkages Charge, number of OH groups (negative

charge, repulsion of like charges, > viscosity)

Linear > branched


Entanglement, highly branched PS will sweep out much less space than a linear PS (collide less frequently and produce a much lower viscosity than will linear molecules of the same DP).

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Gel formation Polysaccharides can form gels that

do not involve normal junction zones Cross-linking

Interaction of 2 different polysaccharides

1st increase of viscosity 2nd gelation

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Starch Amylose (~25%)

a, 1-4 Glu (+ linear) Gelation in cooled, cooked pastes DP 350-1000

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Amylopectin a, 1-4 Glu , a 1-6 Glu (+ branched) Waxy Corn, rice, sorghum Non gelling Stable to freezing and thawing DP 1000s+++

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AmyloseAmylose AmylopectinAmylopectin

MWMW lowerlower higherhigher

Glucosidic Glucosidic bondbond

a 1-4a 1-4 a1-4 & a1-6a1-4 & a1-6

ShapeShape Linear Linear branchedbranched

GelationGelation YesYes NoNo

RetrogradatiRetrogradationon

higherhigher lowerlower

Amylose vs. Amylopectin

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Starch : Organization


Proportion of Amylose to Proportion of Amylose to Amylopectin is ImportantAmylopectin is Important

Grains 15-30 % amyloseGrains 15-30 % amylose Legums 30-70 % amyloseLegums 30-70 % amylose Waxy 0 % amyloseWaxy 0 % amylose

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Amorphous Regionloose association of starchmolecules that is accessible to water

Crystalline Regionclose association of starchmolecules. Causes the reflectance of polarized light (birefringence)

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Reversible swelling Undamaged, raw starch granules + cold water

Small increase in volume

Starch


GelatinizationGelatinization: swelling and disorganiza- : swelling and disorganiza- tion of starch granules heated in watertion of starch granules heated in water

Measures of gelatinizationMeasures of gelatinization Swelling of granulesSwelling of granules Increased viscosityIncreased viscosity Increased translucencyIncreased translucency Increased solubilityIncreased solubility Loss of birefringenceLoss of birefringence Increased susceptibility to enzymesIncreased susceptibility to enzymes

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Starch GelatinizationStarch Gelatinization

Heating causes the following:Heating causes the following: Water absorption Water absorption Rupturing Rupturing Starch network formedStarch network formed Hydrated network with water pocketsHydrated network with water pockets Point at which rupture occurs differsPoint at which rupture occurs differs Gelatinization!Gelatinization!

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Molecular explanation:Molecular explanation: Heat = vibration of atomsHeat = vibration of atoms Vibration = breaks hydrogen bondsVibration = breaks hydrogen bonds Rupture and parting of starch strandsRupture and parting of starch strands Water trapped = increased viscosityWater trapped = increased viscosity Forming of hydrogen bonds = gelsForming of hydrogen bonds = gels

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Gelatinization only occurs with heat and waterGelatinization only occurs with heat and water Dry heating = dextrinizationDry heating = dextrinization

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5% Corn starch = start of heating only has 5% Corn starch = start of heating only has water absorbed onto granule surfaceswater absorbed onto granule surfaces

Granules still clumpingGranules still clumping

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At 40At 40ooC more water as absorbed and granules C more water as absorbed and granules start to separatestart to separate

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At 65At 65ooC more water as absorbed and granules C more water as absorbed and granules start to rupturestart to rupture

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At 70At 70ooC further rupture, leakageC further rupture, leakage

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Main determinants of gelatinization:Main determinants of gelatinization:

Water contentWater content

Starch concentrationStarch concentration

Nature of starchNature of starch

Degrading enzymesDegrading enzymes

Other environmental factorsOther environmental factors

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Starch Granule - Gelatinization

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Starch granules contain both linear amyloseand branched amylopectin.

amylose forms a gel due to hydrogen bonding between the linear chains.

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Raw, uncooked starch granulesheated in water

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Gelatinization and pasting are complete

Some granules have collapsed.

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Now we start to cool.


Starch GelationStarch Gelation: Amylose is the : Amylose is the ““glueglue” that holds the gel together” that holds the gel together Therefore, waxy starches do not gelTherefore, waxy starches do not gel They form thick, cooked pastes and areThey form thick, cooked pastes and are

frequently the starting material in thefrequently the starting material in the

production of modified food starchesproduction of modified food starches

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Notice areas of association. These arecalled junction zones.

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water

water

water

waterwater

water

This is a starch gel

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Gelatinization to Gelation

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Retrogradation and SynersisRetrogradation and Synersis

Amylose network is held in place by H bonds H bonds are continuously breaking and reforming Constant rearrangement of amylose liquid

escapes = Syneresis

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Reversal of retrogradation depends on the percentage of amylose vs amylopectin. The more amylose, the harder it is to reverse.

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Examples of starch retrogradationstarch retrogradation

Staling of bakery goods Separation in gravies and old pudding

Reversed by re-heating


Factors affecting gelatinization,Factors affecting gelatinization,

retrogradation, and gel formationretrogradation, and gel formation SugarSugar

Competes for water and plasticizes junctionCompetes for water and plasticizes junction

zones; decreases gelatinization and zones; decreases gelatinization and gelgel

strength, increases gelatinization strength, increases gelatinization temp.temp.

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AcidAcid Hydrolysis of acid sensitive glycosidicHydrolysis of acid sensitive glycosidic

linkages produces smaller pieces of linkages produces smaller pieces of starch molecules; decreases gel starch molecules; decreases gel

strength, strength, Faster gelatinization.Faster gelatinization.

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Polar lipids retard gelatinization Polar lipids retard gelatinization form complexes with amyloseform complexes with amylose

Stirring/shearing/pumpingStirring/shearing/pumping Collapses swollen granules; this Collapses swollen granules; this

decreasesdecreases

gel formation and gel strengthgel formation and gel strength

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Thickening ability Potato>waxy corn>waxy rice>waxy

sorghum>tapioca>wheat Wheat flour is less effective

+ protein, - starch Pastry and cake flour better than

wheat flour - protein

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Role of sugar Competes with starch for water > translucency, < gelatinization rate, < viscosity,<

gel strength Reduces swelling and interferes with junction

zones Role of lipids

Retards swelling and interferes with junction zones. Role of acid

Breaks down starch (runny product)


Modified starches The definition for modified starch is: The definition for modified starch is:

“Starch which has been treated physically “Starch which has been treated physically or chemically to modify one or more of its or chemically to modify one or more of its key physical or chemical properties.”key physical or chemical properties.”

Modified starches can haveModified starches can have functional functional properties properties used in large scale food used in large scale food production that native starches do not production that native starches do not provide.provide.

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In modified starches, only very few of In modified starches, only very few of the OH groups are modified. Normally, the OH groups are modified. Normally, ester or ether groups are attached at a ester or ether groups are attached at a very low DS. DS values are often <0.1 very low DS. DS values are often <0.1 and range 0.002-0.2. Thus, there is, ~ and range 0.002-0.2. Thus, there is, ~ one substitution group on every 5-500 one substitution group on every 5-500 glucose units.glucose units. DS, average # of esterified or etherfied DS, average # of esterified or etherfied

groups/monosaccharide unitgroups/monosaccharide unit

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Modified starches Pre-gelatinized

Heat, swell and dry again Minute rice, Instant puddings, oat meal.

Acid Breaks glycosidic bond outside (amorphous

region) Crystalline region is more difficult to swell:

requires a lot of energy. <viscosity, > gelatinization temp, < gel strength Gum candies and confections


Starch can be Chemically Modified to Starch can be Chemically Modified to create a wide range of functionalitiescreate a wide range of functionalities Hydroxyethyl starchesHydroxyethyl starches Cationic starchesCationic starches Starch acetatesStarch acetates Starch succinatesStarch succinates Starch PhosphatesStarch Phosphates Hydroxypropyl starchesHydroxypropyl starches

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Pregelatinized StarchesPregelatinized Starches Bleached Starches, treatment with low Bleached Starches, treatment with low

concentrations of oxidizing agentsconcentrations of oxidizing agents Dextrins/MaltodextrinsDextrins/Maltodextrins

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Cross linked Starch Reinforced with covalent bonds Higher stability

Heat Agitation Low pH

Sterilized or canned products Baby foods, cream corn

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Production of HFCS from Starch Corn starch Glu Fru DE = weight of Glu/ total weight * 100= % of reducing sugar Methods

Acid (HCl-0.12%) + temperature (120-160°C) Acid + enzyme (amylases and glucoamylase) Gelatinization + enzyme

Glu Fru ; Isomerase

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Vegetable Gums Hydrocolloids Long chain of monosaccharides Sources

Seaweed Carrageenan & salts; Agar; Alginates

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Seeds Guar, Locust bean gum

Bark (exudates) Gum arabic, Gum tragacanth, Karaya

Microorganisms Xanthan, Dextran, Gellan

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Uses of vegetable gums Crystallization Inhibitor Whipping aid Foam Stabilizer Form and stabilize emulsions Coating agent Prevent syneresis Suspend solids Act as a carrier (flavor) Bulking agents/fat replacers

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Carbohydrates functional properties