Carbohydrates functional properties

Carbohydrates: Functional Properties NFS 360 Basil K. Dalaly Professor Department of Health and Nutritional Sciences South Dakota State University

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Carbohydrates: Functional Properties 

Following  

  

is a listing of possible roles:

flavor enhancer and sweetener flavor and color due to caramelization cara ca rame meliliza zati tion on an and d browning reaction serve as water binders contribute to texture (starch viscosity) serve as a hygroscopic nature/water absorption

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Carbohydrates: Functional Properties        

Y Y easts easts

grow on CHO in food regulate gelation gela ge lati tion on of pectin pect pe ctin in disperse molecules of protein or starch preservation control crystallization structure due to crystals effect osmosis effect color of fruits 4

Important

  

Sweetness Solubility Hygroscopicity and Water binding   

Reduces aw Humectancy H2O migration (moisture barrier) 



Characteristics of Sugars

The smaller, the better

Formation  

of colors

Caramelization Maillard reactions 5

Relative sweetness of various carbohydrates fructose

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.

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Tagatose



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 ster st ereo eo-is -isome omerr of fructo fructose se

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Sweetness 

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

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Important




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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Important



Hygroscopicity 



Solvation/ solubilization of sugars

Disadvantage: 



High number of OH groups.

Advantage: 




Caking and lumps

Fructose

is the more hygroscopic. 10

Important

  


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

  

Break down of glycosidic bonds Ring size alterations and Anomeric shifts Formation of new glycosidic bonds.

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Important



2nd step (Prolonged heating)  



Dehydration Introduction of double bonds in the sugar rings

Conjugated double bonds 




Hexose

hydroxymethylfurfural hydroxymethylfurf ural (HMF)

Higher temp and higher pH=higher reaction rate 12

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Important


Crystalline forms of sugar: Closely   

packed in an organized pattern. Table sugar: granulated sucrose Confectionary sugar Raw sugar 



Brown sugar 



2-3 % impurities (further purification) Molasses

Crystalline glucose 14

Important



Liquid forms Corn syrups   



characteristics of sugars

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

Molasses  

<25% water and <5% ashes Sucrose, fructose and glucose 15

Important



Maple  



characteristics of sugars

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 17

Polysaccharides Functions in Foods 

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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V Viscosity iscosity,,  





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

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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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Polysaccharides Functions in Foods



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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Am A mylose

vs. A Am mylopectin Amylose Amylose

Amylopectin Amylopectin

MW MW

lower

h higher i g h er

Glucosidic bond S h ap e Shape

a 1- 1-4 4

a1- a1 -4 4 & a1- a1-6 6

Linear Linear

branched

ess Y Y e

No No

higher

lower lower

Gelation Retrogradation Retrogradation

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Polysaccharides Functions in Foods Starch : Organization

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Proportion of Amylose to Amylopectin is Important   

Grains Legums Waxy

15- 15-30 30 % amylose 30- 30-70 70 % amylose 0 % amylose

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Amorphous Region loose association of starch molecules that is accessible to water

Crystalline Region close association of starch molecules. Causes the reflectance of polarized light (birefringence) 27

Starch



Reversible swelling 

Undamaged, Undamage d, raw starch granules + cold water



Small increase in volume

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

Gelatinization:: swelling and disorganiza- Gelatinization disorganiza- tion of starch granules heated in water Measures of gelatinization      

Swelling of granules Increased viscosity Increased translucency Increased solubility Loss of birefringence Increased susceptibility to enzymes

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Starch Gelatinization 

following: ing: Heating causes the follow 

Water absorption



Rupturing



Starch network network formed



Hydrated network with water pockets



Point at which rupture occurs differs



Gelatinization!

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Molecular

explanation:



Heat = vibration of atoms



Vibration = breaks hydrogen bonds



Rupture and parting of starch strands



Water trapped trapped = increased viscosit y



Forming of hydrogen bonds = gels

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Gelatinization only occurs with heat and water



Dr y heating = dextrinization

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

5% Corn starch = start of heating onl y has water absorbed onto granule surfaces Granules still clumping

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40oC more water as absorbed and granules start to separate

A At

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65oC more water as absorbed and granules start to rupture

A At

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Starch Gelatinization 

A At

70oC further rupture, leakage

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Starch Gelatinization

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Starch Gelatinization

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Main

determinants of gelatinization:



Water content



Starch concentratio concentration n



Nature of starch



Degrading enz ymes



Other environmental factors 39

Starch Star ch Gran Granule ule - Gel Gelati atiniz nizati ation on

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Starch granules contain both linear amylose and branched amylopectin. amylopectin.

amylose forms a gel due to hydrogen bonding between the linear chains. 41

Raw, uncooked starch starch granul granules heat heated in wat water

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Some granul granules have coll collapsed. apsed.

atinizat izatiion Gelati

and pasti pasting are compl complete 43

Now

we start to cool. cool.

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Starch Gelation: Gelation: Amylose is the glue  glue glue that holds the gel together  

Therefore, waxy starches do not gel They form thick, cooked pastes and are frequently the starting material in the production of modified food starches

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Not

ce area areass of asso assocc at on. on. Th Thes esee are are ca ed jun junct ct on on ones es..

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water ater

water ater water ater

water ater

water ater water ater

starch gel This is a starch This gel

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Gelatinization to Gelation

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  

Ret etrogradation etro rogr grad adat atio ion n

and an d Synersis

Amylose netw Amylose network ork is held held in place place by by H bonds bonds H bonds are continuously breaking and reforming Constant rearrangement of amylose liquid escapes = Syneresis 50

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

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Examples

 



of starch retrogradation

Staling of bakery goods Separation in gravies and old pudding

Reversed by re-heating

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

Factors affecting gelatinization, retrogradation, and gel for mation Sugar 

Competes for water and plasticizes junction

zones; decreases gelatinization and gel strength, increases gelatinization temp.

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A Acid 

Hydrolysis of acid sensitive glycosidic linkages produces smaller pieces of starch molecules; decreases gel strength, Faster gelatinization.

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Polar lipids retard gelatinization 



form complexes with amylose

Stirring/shearing/pumping 

Collapses swollen granules; this decreases

gel formation and gel strength

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Polysaccharides Functions in Foods Thickening 



ability Potato>waxy corn>waxy rice>waxy sorghum>tapioca>wheat Wheat flour is less effective 



+ pro prote tein in,, - st star arch ch

Pastry and cake flour better than wheat flour 

- protein 56


Role of sugar  





Role of lipids 



Competes with starch for water > translucency, < gelatinization rate, < viscosity,< gel strength Reduces swelling and interferes with junction zones Retards swelling and interferes with junction zones.

Role of acid 

Breaks down starch (runny product) 57


Modified starches 



The definition for modified starch is: Starch which has been treated physically or chemically to modify one or more of its key physical or chemical properties. Modified starches can have functional properties used in large scale food production that native starches do not provide. 58


In modified starches, only very few of the OH groups are modified. Normally, ester or ether groups are attached at a very ve ry low DS. DS values are often <0.1 and range 0.0020.0 0.002 02--0.2. -0 0.2. .2. Thus, Thus, there ther th ere e is, ~ one one substitution group on every 5- 5 -500 500 glucose units. 

DS, average # of of esterified este es teri rifi fied ed or etherfied groups/monosaccharide groups/monosaccha ride unit 59

Polysaccharides Functions in Foods Modified 

Pre-gelatinized  



starches

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. gelatinization temp, < gel strength Gum candies and confections 60


Starch can be Chemically Modified to create a wide range of functionalities      

Hydrox Hyd Hydroxyethyl roxyet yethyl hyl sta starch starches rches es Cationic starches Starch acetates Starch succinates Starch Phosphates Hydrox Hyd Hydroxypropyl roxypr ypropy opyll sta starch starches rches es 61

Polysaccharides Functions in Foods  



Pregel Pre Pregelatinized gelati atiniz nized ed Sta Starc Starches rches hes Bleached Starches, treatment with low concentrations of oxidizing agents Dextrins/ Dextrins /Maltodextrins Maltodextrins

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Polysaccharides Functions in Foods  

Cross linked Starch Reinforced with covalent bonds Higher stability   



Heat Agitation Low pH

Sterilized or canned products 

Baby foods, cream corn 63

Polysaccharides Functions in Foods Production of    

from Starch

Corn starch Glu Fru DE = weight of Glu/ total weight * 100= % of reducing sugar Methods   



HFCS

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

Glu

r

Fru

; Isomerase 64

Polysaccharides Functions in Foods Vegetable   

Gums

Hydrocolloids Long chain of monosaccharides Sources Seaweed  

Carrageenan Carragee nan & 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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Polysaccharides Functions in Foods 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

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