1. Polysaccharides 1

2. Introduction
Those carbohydrates that consist of more than 10 (sometimes defined as >20) monosaccharide units linked via a glycosidic bond
Glycosidic bond

3. Introduction
Those carbohydrates that consist of more than 10 (sometimes defined as >20) monosaccharide units linked via a glycosidic bond
Also called glycans
They are classified as:
Homo-polysaccharides
Glycans composed of a single monosaccharide unit with one or more type of glycosidic linkages
Example: Starch
Hetero-polysaccharides
Glycans composed of more than one type of monosaccharides
Examples: Gums, dietary fibers, pectinic substances, hemicellulose

4. Starch Second largest biomass on earth, after cellulose
The predominant food reserve substance in plants where it occurs as starch granules
1. Seeds (e.g. peas, grains, beans) ?
2. Roots, tubers , stems (e.g. potato, tapioca, pineapple) ?
3. Fruits (e.g. plantain, bananas) ?
4. Leaves (e.g. tobacco) ?
One of our main carbohydrate source (Two more?)
Primary use in foods
Vast number of uses and functionalities
Naturally present in plant derived foods
E.g. contributes to the texture of bread, cooked rice, pasta and potatoes, etc.
Added to foods for viscosity, gelling, moisture retaining, stabilizing, texturizing, thickening, anti-staling, film-forming, binding, foaming applications, etc. etc.

5. Uses of Starch Flavors and Beverage Clouds Canning Cereals and Snacks
encapsulation of flavors, fats,
spray dried flavors for dry beverage
beverage emulsions
liquid and powdered non-dairy creamers
Canning
filling viscosity aid
suspension aid for particulates
opacity agent
body for soups, sauces, puddings and gravies
aseptically canned products
beverages such as coffee, teas or chocolate
Cereals and Snacks
hot extruded snacks
chips, pretzels, etc.
extruded and fried foods
ready-to-eat cereals
Cooked Meat Binder
water binder for formed meat
smoked meats, low-fat meats
pet foods (dried and canned)

6. Uses of Starch Frozen Foods Bakery Dressings, Soups and Sauces
fruit fillings
meat pies
dairy products
soups, sauces
entrees
cream-based products
Bakery
pies, tarts
fillings, glazes
custards and icings
cakes, donuts
Dressings, Soups and Sauces
mayonnaise-type
pourable salad dressings (high shear)
spoonable dressings
instant dry salad dressing mixes
low-fat dressing
canned gravies and sauces
frozen gravies and sauces
soups and chowders
Confectionery
dusting powder, licorice
jelly gums, hard gums
panned candies

7. Polymer of D-glucose units Two major forms:
CHEMICAL STRUCTURE
Polymer of D-glucose units
Two major forms:
AMYLOSE : Large linear molecule with  1-4 glycosidic bonds
Some may have a few branches 4 1

8. AMYLOSE : Large linear molecule with  1-4 glycosidic bonds
Some may have a few branches
Linear, helical structure
Strong helical complex
Glucose units
Importance of structure: Determines its packing ability
e.g. Retrogradation

9. Polymer of D-glucose units Two major forms:
CHEMICAL STRUCTURE
Polymer of D-glucose units
Two major forms:
AMYLOPECTIN: Highly branched and very large molecule
Branches linked to the main chain via  1-6 bonds
Branches very close giving amylopectin a cluster structure
a (1-6) linkage 1 6

10. Polymer of D-glucose units Two major forms:
CHEMICAL STRUCTURE
Polymer of D-glucose units
Two major forms:
AMYLOPECTIN: Highly branched and very large molecule
Branches linked to the main chain via  1-6 bonds
Branches very close giving amylopectin a cluster structure

11. AMYLOPECTIN: Highly branched and very large molecule
Branches linked to the main chain via  1-6 bonds
Branches very close giving amylopectin a cluster structure
Helical branches

12. Starch
Summary of the different properties of amylose and amylopectin

13. Starch
The structure and ratio of amylose/amylopectin varies with starch variety and age of plant
Starch granule morphology also varies with plant source

14. Starch

15. Starch
Different sizes and shapes of starch granules from different plant sources
Polarized light micrographs of potato starch
“Maltese cross”
10 μm
Amylose and amylopectin inside the granules are tightly packed via extensive H-bonding
-Crystalline property
Granules are insoluble in cold water
Corn starch (B) Wheat starch
(C) Potato starch (D) Rice starch

16. Starch
Different starch granules have also different x-ray diffraction patterns: A, B and C (combination of A+B)
X-ray diffraction studies show that the starch granule is a mixture of crystalline and amorphous regions
The crystalline region consists of starch in the form of a double helix – very stable
Hydrophobic and H-bonds
Insoluble in water at room T; need energy to break the bonds
Starch double helix

17. Crystalline and Amorphous

18.                                                                                                                                        <>
Maltese cross

19. Pea starch granules
Mutations can induce dramatic changes in starch granule morphology and thus modified function

20. Starch
The aforementioned variations lead to different functional properties, e.g.:
More H-bonds and packing  higher gelatinization temps.
Need more energy to disrupt the double helix
More phosphate groups  lower gelatinization T, higher viscosity and clarity of starch paste
Electrostatic repulsion due to charged P-group
Amylose/ Amylopectin ratio
Great effect on gelation and texture of starch pastes
Waxy starch: 0-8% amylose
Disperses more easily, produces a clear viscous paste rather than gels
Normal starch: 20-30% amylose
High tendency to form gels
High amylose starch: >50% amylose
Very high tendency to form gels

21. Gelatinization of Starch
Room Temp (27oC)
Heating (40oC)
Raw Starch
Swelling (50oC)
Swelling (60oC)
Rupturing (65oC)
Gelatinization and pasting (70-90oC)
Imploding (90oC)

22. Starch GELATINIZATION
When starch is heated sufficiently (to break the hydrophobic and H- bonds) in the presence of water the granule begins to swell (loses order):
Granule imbibes water
Viscosity is increased
Clarity is increased
Some amylose may leach out
Get loss of birefringence (“Maltese cross” disappears)
Starch goes from “glassy” to rubbery state (Tg)
E.g. uncooked vs. cooked spaghetti
The Tg varies depending on e.g. %H2O and starch type
Starch
Gelatinization T
Corn
62-70ºC
Waxy corn ºC
Sorghum
68-75ºC
Potato ºC
Tapioca ºC

23. Starch
PASTING
Second stage swelling occurs when starch is heated above the gelatinization T
This is needed to obtain maximum viscosity
More amylose is leached out and it eventually gels (retrogradation – on cooling)
Eventually the starch granule will completely disrupt
The end point T needed to obtain the maximum viscosity is starch dependent
Starch
End Point T
Corn
95ºC
Waxy corn
75ºC
Sorghum
Potato
70ºC
Tapioca
85ºC

24. Amylose
(linear)
Amylopectin
(branched)
A cereal starch gel showing how water is being trapped by the gel network

25. Starch granule
Corn starch granules
Wheat starch granules
Amylose
Amylose
Starch was heated at 80°C for 30 min

26. Starch
Changes in starch viscosity are evaluated using a Brabender amylograph
Starch slurry is heated (and cooled) at a constant rate with constant stirring and viscosity measured
Can get a lot of useful information from the amylographs
E.g if starch has high peak viscosity then you know they need more energy to stir and manipulate
By comparing different starches you can pick the one just right for your application

27. Peak viscosity

28. Each type of starch has a characteristic gelatinization/pasting profile

29. Starch STARCH GELATINIZATION
Gelatinization only occurs with heat and water
(Dry heating = Dextrinization)

30. Starch STARCH GELATINIZATION
When heating begins, water absorbed on granule surface; granules still clumped together (30oC)

31. Starch STARCH GELATINIZATION
At 40oC, more water absorbed and granules start separating

32. Starch STARCH GELATINIZATION
At 50oC, more water absorbed and granules start swelling; H-bonds within granule broken; Amylose leak out

33. Starch STARCH GELATINIZATION
At 65oC, more water absorbed and granules start rupturing;

34. Starch STARCH GELATINIZATION
At 70oC, more rupturing and leakage, Gelatinization: Loss of birefringence (Maltese cross disappears), more viscous, translucent, enzyme action; more clarity

35. Starch STARCH GELATINIZATION
At 90oC, optimum gelatinization; granules may disintegrate or implode, Overcooking could decrease viscosity !!

36. Starch
On cooling, gelatinized starch retains some of its crystal structure –Retrogradation
Starch paste on cooling form intermolecular bonds – gel
Gel structure mostly from Amylose bound to each other and from slight interaction with Amylopectin molecules.
This phenomenon is called retrogradation
Critical for ultimate rigidity of final product

37. Starch Retrogradation and staling
On cooling, amylose line-up and form H-bonds. They form crystals- Retrogradation
Starch granule
After gelatinization, amylose is removed from the granule

38. Viscosity
Gelation

39. Starch
Ratio of amylose to amylopectin and their size is important for the different behaviors seen:
 Amylose
swelling
greater loss of peak viscosity
Amylose
 swelling
stronger gels
Larger amylose/amylopectin
molecules
More viscosity
Weaker gels
Chemical groups and interactions with other ingredients also play an important role
E.g. potato starch and phosphate groups
Cereal starches and phospholipids

40. Starch Uses of High Amylose starch Stronger gels
High gelling capacity useful for making candies – decreases hardening times from 72 h to 24 h – reduces cost
Firm, crisp, crunchy films – coating battered products such as French fries, frozen fish, poultry, vegetables

41. Starch Uses of low Amylose starch Viscous pastes with stringy texture
Stabilizers and all-purpose thickeners for food products – particularly those which undergo large temperature changes during processing
Waxy starch do not lose water during freezing and thawing – frozen food products
Emulsifier for salad dressings

42. Starch Examples of starch properties and function
Cereal starches (corn, wheat, rice etc.)
A type (low mol. weight amylose and amylopectin with short branches)
High degree of packing/crystallinity
Higher gelatinization/pasting T
Low swelling power (10-20 g H2O/g dry starch)
Viscous, short bodied paste
Opaque gels on cooling

43. Starch Examples of starch properties and function
Root and tuber starches
B type (high mol. weight amylose and amylopectin with long branches)
Low degree of packing/crystallinity
Lower gelatinization/pasting T
High swelling power ( g H2O/g dry starch)
Highly viscous, long bodied paste
Weak clear gels

44. Starch Examples of starch properties and function
Waxy starches (waxy corn)
Genetically modified (bred) to contain only amylopectin
Less order and less packing (why? AP?)
Higher swelling power than cereal starches
Very heavy bodied and stringy
No or poor gelation

45. Starch Retrogradation and staling
When a hot starch is cooled it generally forms a viscoelastic, firm and rigid gel or precipitate
starch molecules are realigning and forming double helixes that then will aggregate  starch becomes progressively less soluble
Applies to the linear portion of the starch molecules
This phenomena is called RETROGRADATION
Happens far more rapidly with amylose vs. amylopectin
During heating amylose leeches out of the starch granule and gels on cooling
High mol. weight amylose less prone to escape
High conc. of amylopectin, e.g. in waxy maize, leads to less/slower retrogradation

46. Starch Retrogradation and staling
Retrogradation is the cause behind firming of bread as it cools after baking
Causes bread to become STALE on storage
First event: during baking amylose leeches out and retrogrades almost fully on cooling  positively affects texture by giving an elastic and tender crumb
Second event: On storage amylopectin branches slowly associates  crumb and bread hardens = STALING
Happens faster during refrigeration but is inhibited (slowed down during freezing)

47. Starch Some factors affecting retrogradation
Size of linear starch molecule
Smaller amyloses have more tendency than large to closely associate into “crystal precipitates”
Amylose/amylopectin ratio
More amylose = more and faster retrogradation (Why?)
The branches of amylopectin participate in retrogradation at later stages
Rate of cooling
Fast  Gel
Slow  Crystal precipitates
(retrogradation)

48. Starch Some factors affecting retrogradation 4. Temperature
Cooling accelerates
Freezing stops
Heating reverses (e.g. bread)
5. Interfering molecules
Fatty acids
Form insoluble complex with
starch and interfere with retrogradation
Emulsifiers/surfactants (both hydrophilic and hydrophobic nature)
Inhibit crystallization by complexing with helical amylose
Commonly used in dough for bread and other baked goods to increase shelf life

49. Starch Interactions of starch with other molecules Iodine
I3- complexes with both amylose (blue color) and amylopectin (red-purple color – branches are too short) helixes
Used to determine amount of amylose in starch
Has to be linear
Over 45 units
Under 12 units – no color

50. Starch Interactions of starch with other molecules
Fatty acids and polar lipids (e.g. emulsifiers)
Bind tightly into the hydrophobic region of the helix
Interfere with gelatinization and pasting
Entangle starch molecules and lead to less swelling, more opacity and “short” viscosity
Inhibit crystallization (retrogradation)
Surface active lipids can coat the starch granule and make it “waterproof”
Water
If too low  no gelatinization (need >60%)
Sugars
Compete for water  retard/delay gelatinization (Tg) pH
Acid can cleave the glycosidic bonds  less swelling/viscosity

51. Starch Starch modification Necessary for many food applications
Native starch is very sensitive to harsh processing and storage conditions:
Low pH
High and low Temperature
Pumping
Storage and transportation
Modifications can be chemical, physical and enzymatic
Limited number of modified starches approved by FDA
Have to be labeled as “modified food starch”

52. Starch Starch modification 1) Hydrolysis (Hydro - lysis)
Use acid to hydrolyze starch into smaller units
Need high heat (hot acid sprayed over starch)
Limited to non-crystalline region
Dark pigments and off-flavors can develop
Changes induced by decreased chain length
1. Sweetness increases (Why?)
2. Increased reactivity as reducing sugar (Why?)
3. Decreased viscosity and low peak viscosity (Why?)
4. Increased solubility (Why?)
5. Increased fermentability
6. Less swelling on heating
Get an increase in Dextrose Equivalence (DE) with increased hydrolysis
DE=100/DP (Measure of reducing group)
DP = Degree of Polymerization

53. Starch Starch modification (Hydrolysis cont.)
Products of acid hydrolysis
Thin boiled starch
Starch heated and sprayed with hot acid (or treated with hot HCl gas)  Starch neutralized  Starch washed and dried
Starch granule remains “intact”
Granule breaks easily when heated in water
Clearer and stronger gels than native starch
Gum candy (jelly beans, jujubes)
Films and adhesives (candy and nut coatings)
Processed cheese

54. Starch Starch modification (Hydrolysis cont.)
Can also use enzymes to hydrolyze starch
a – amylase
Endo-enzymes = cleave the glycosidic bond within starch in the non-crystalline regions (cleaves a- 1-4 linkage)
Products are DEXTRINS (small starch units), MALTOSE and MALTOTRIOSE
a -amylase

55. Starch Starch modification (Hydrolysis cont.)
Can also use enzymes to hydrolyze starch
-Amylase
Exo-enzyme = hydrolyzes starch at the non-reducing end
Product is MALTOSE (cleaves a- 1-4 linkage)
b-amylase

56. Starch Starch modification (Hydrolysis cont.) Amyloglucosidase
Exo-enzyme = hydrolyzes starch at the non-reducing end at -1-4 and -1-6 linkages
Product is D-GLUCOSE (low calorie beer)
Amyloglucosidase

57. Starch Starch modification (Hydrolysis cont.)
Iso-amylase & Pullulanase -> hydrolyze -1-6 bonds (remove branches)
Iso-amylase

58. Starch Starch modification (Hydrolysis cont.)
Products of enzymatic hydrolysis
Dextrins
Heated starch treated with enzymes (can also use acid)
Can produce a range of partially hydrolyzed starch polymers
Maltodextrin
<20 DE
Bland flavor, no sweetness
Good bulking agents
Good humectants/water absorbers at ~20 DE
Fat-like properties at ~5 DE
1-4 kcal/g

59. Starch Starch modification ( Hydrolysis cont.)
Products of enzymatic hydrolysis
Corn syrups
A combination of enzymes used to produce corn syrups
Corn syrup solids
Hot starch hydrolyzed with enzymes and then dried
20-60 DE
High Fructose Corn syrup (liquid)
Gelatinized starch + enzyme  dextrose (liquid glucose)  glucose isomerase  Fructose (42%) + Glucose (58%)  Cation exchange column  high fructose corn syrup (>55% fructose) e.g. Colas

60. Starch modification Cross linked starch
Derivatized starch or substituted starch
Anionic (negative charges)
Cationic (positive charge)
Non-ionic (hydroxy alkyl starch)

61. Starch Starch modification 2) Cross-linked starches
Most common chemical modification method
Can react starch with a variety of bi-functional cross-linking reagents
E.g. sodium trimetaphosphate at alkaline pH followed by drying
Get phosphate diester bond (only need a few)
Results
resistance to granule rupture and degradation
Firmer texture and viscosity
Can tolerate harsh processing conditions
Acid, shear and thermal treatment (e.g. canning)
Very stable on processing and storage

62. Degree of cross linking
Application
Lightly cross linked
Neutral and slightly acidic foods
Medium cross linked
High acid foods;delay gelation for some canned foods; foods stored at low temperature;
Highly cross linked
High shear, high temperature

63. Starch Starch modification 3) Derivatized or substituted starches
Can react OH groups of starch with various compounds to change function
A) Oxidized starches
React starch with hypochlorite at pH 9-9.5
Increased whiteness and partial hydrolysis
More electrostatic repulsion  clearer pastes and less retrogradation and more stability
Cake flour and frying batter

64. Starch Starch modification (Derivatized starches cont.)
B) Phosphorylated starches
Treat starch with phosphates or polyphosphates
Starch gets a negative charge and thus there is more electrostatic repulsion between the starch molecules
Lower Tg, viscosity + clarity + stability (low retrogradation)
Can control viscosity by salt addition
Add salt and viscosity drops (“screens” electrostatic repulsion)
This starch is useful in products that are to be frozen and thawed and it is an excellent thickening agent

65. Starch Starch modification (Derivatized starches cont.)
C) Hydroxypropylated starches
Treat starch with propylene oxide (Starch-O-CH2-CHOH-CH3) at alkaline pH
Great cold-storage and freeze-thaw stability = clear paste with no retrogradation  used in frozen foods and desserts as thickening agent
Also smooth texture and often used to improve viscosity under acidic conditions

66. Starch Starch modification (Derivatized starches cont.)
D) Acetylated starches
Starch treated with acetic anhydride at alkaline pH
Can only be used at very low acetylation levels in foods
Low Tg, improved freeze-thaw stability, low retrogradation and good clarity
E) Succinated starches (Butanedioic acid )
Starch treated with succinic anhydride at alkaline pH
Get a negative charge = repulsion (similar to phosphorylated starch)
solubility and viscosity
Can make by treating with octenyl succinic anhydride (has a hydrophobic part)
Now have a hydrophilic and hydrophobic starch
Good emulsifier (stabilize both water and lipid phase)

67. Starch Starch modification 4) Physically modified starches
A) Pre-gelatinized starch
Starch paste heated in a drum dryer where granules almost instantaneously gelatinizes and pastes  paste dries off and is made into a powder
The powder is now soluble in cold water!
Provides instant viscosity upon addition (no heat needed)
Applications
Instant soups/puddings
Pizza toppings
Instant cakes etc.

68. Starch Starch modification (Physically modified starches cont.)
B) Cold water soluble/swelling starch
Starch (corn) heated in 70-90% ethanol (alcohol)
Swells extensively in cold water
Dispersible in sugar solutions (when stirred rapidly)
Pour in molds and you get gum candy on setting
Used in muffin batters to hold particles (e.g. berries)

69. Starch Starch modification (Physically modified starches cont.)
C) Resistant starch
Highly crystalline starch formed by repeated freezing and thawing (retrogradation) of high amylose starch
Non-crystalline regions removed by enzymes and the rest is resistant starch
Used as dietary fiber (non-digestive)