1

FOOD SCIENCE AND TECHNOLOGY AGRICULTURAL TECHNOLOGY

BRAWIJAYA UNIVERSITY 2012

ENDRIKA WIDYASTUTI

09/03/2012 2

Starch Ingredients

Must be cooked

Gel slowly

Show syneresis

Break down under shear

Break down under acid conditions

Forms complexes

Amaranth starch

(Bar: 1 µm)

Arrowroot starch

(Bar: 20 µm)

Buckwheat starch

(Bar: 5 µm)

Cassava starch

(Bar: 10 µm)

Corn starch

(Bar: 10 µm)

Oat starch

(Bar: 5 µm)

Potato starch

(Bar: 50 µm)

Rice starch

(Bar: 2 µm)

Kidney bean starch

(Bar: 20 µm)

Unheated starch granule

Heated starch granule

What is STARCH ?

Complex carbohydrate made up of two components

Components: Amylose (linier chain)

Amylopectin (branched chain)

Properties(viscosity) depend on amounts of the components

Amylose

Linear component of starch

Contains 1,4-alpha-glucosidic bonds

Molecular weight: less than 0.5 million

Can form coils which will trap iodine and turn blue

Branched component of starch

Contains 1,4-alpha-glucosidic as well as 1,6-alpha-glucosidic bonds

Molecular weight: 50-500 million

Limited coiling causes purplish-red color when iodine added

Amylopectin

Amylopectin in Granules

Amylopectin structure (Chaplin, 2004)

Amylopectin General Structure

Amylose vs. Amylopectin

Starches usually contain more amylopectin than amylose

Generally roots/tubers contain more amylopectin than cereals

Roots/Tubers: 80% amylopectin Cereals: 75% amylopectin Waxy corn and rice contain virtually all

amylopectin

Characteristics of Amylose and Amylopectin

FORM

Essentially linear

Branched

LINKAGE

-1,4 (some -1,6)

-1,4; -1,6

POLYMER UNITS

200-2,000

Up to 2,000,000

MOLECULAR WEIGHT

Generally <0.5 million

50-500 million

GEL FORMATION

Firm

Non-gelling to soft

CHARACTERISTIC AMYLOSE AMYLOSPECTIN

Starch Composition

Starch % amylose % amylopectin

Tapioca 17% 83%

Potato ~20% ~80%

Wheat 25-26% ~75%

Corn 24-28% ~75

Waxy corn ~0% ~100%

Hi amylose

Rice

~ 75%

22%

~ 25%

78%

Starch Granule

Made in the cytoplasm of plant cells

Amylopectin forms in concentric circles with amylose dispersed in between

Held together by hydrogen bonds

The granule swells when heated in water

Starch Granule

Granule Structure

Functions

Gelatinization Structure in baked products

Thickener in sauces, soups, and dressings

Dextrinization

Gelation Pie filling

Gelation

As a starch paste cools, a gel is formed

Free amylose molecules lose energy as the temperature decreases and form hydrogen bonds

The bonds create a network that holds the swelled granules in place

Gelatinization

When starch is heated in water

Hydrogen bonds break, allowing water to enter the granule and the granule swells

Amylose migrates out of the granule

H-bonding between water and amylopectin increases

Reduced free water changes the viscosity of the starch mixture, thickening it

Gelatinization and Temperature

Gradually thicken with temperature

Can be heated to 100oC without much granule rupture

If held at 95oC will implode and lose viscosity

Gelatinization and Type of Starch

Best thickening ability: potato starch

Worst thickening ability: wheat starch

More amylopectin=more translucent=more stringy

Gelation and Starch Source

The more amylopectin (less amylose), the softer the gel

Potato starch=high amylopectin=good thickening agent=soft gel

Corn starch=less amylopectin=less effective thickening agent=strong gel

Viscosity and Type of Starch

Gelatinization and Sugar

Used together in pie fillings and puddings Sugar competes with the starch for water

so less water available for gelatinization Delays gelatinization and decreases

viscosity Increases gelatinization temperature The more sugar added, the longer the

delay Disaccharides have a stronger effect than

monosaccharides

Gelatinization and Acid

Used together in fruit pie fillings, specifically lemon fillings

Acid breaks down starch molecules so the paste is thinner

Decreases viscosity Acid effect can be minimized by adding

after gelatinization or heating rapidly

Gelation and Other Effects

Heating Moderate temperature and rate of heating

Enough amylose needs to be released from the granule without the granule bursting

Agitation Agitation during cooling disrupts amylose

network

Should mix flavorings immediately after removing from heat

Gelation and Other Effects

Sugar Decreases gelatinization and amylose

release

Softer gel

Acid Decreases gelatinization by hydrolysis of

granules

Softer gel

Aging Gels

Syneresis Loss of water from a gel

Amylose molecules pull together, squeezing water out

Retrogradation Realignment of amylose molecules

Hydrogen bonds break and reform into more orderly crystals

Can by reversed by gently heating

Examples: refrigerated pudding, stale bread

Dextrinization

When starch is heated without water

A higher temperature is reached than

with water

Bonds break throughout the starch

forming dextrins

How to compare starches? Line spread test:

Measures thickening power Poor heated starch into cylinder, lift cylinder

and measure spread after specified time using concentric circles

Universal Texture Analyzer: Measures gel strength

Percent sag: Measures gel strength Measure molded gel height and compare to

unmolded gel height Stronger gel=small % sag, weaker gel=large %

sag

Visco/Amylo/Graph

ViscoAmyloGraph

Time

Vis

cosity

65oC

90oC

30oC

heating constant temperature

A m ylo se

S w e llin g C o llap se A g g reg a tio n

C

V isco s ityE

D

B

AT im e

A = P as te in itia tio n tem p era tu re

B = P eak P as te T im e

C = P eak V isco s ity

D /C = S tab ility ra tio

E /D = S e t b ack ra tio

50 65T em p 90 95 80

A m ylo se

S w e llin g C o llap se A g g reg a tio n

C

V isco s ityE

D

B

AT im e

A = P as te in itia tio n tem p era tu re

B = P eak P as te T im e

C = P eak V isco s ity

D /C = S tab ility ra tio

E /D = S e t b ack ra tio

50 65T em p 90 95 80

A m ylo se

S w e llin g C o llap se A g g reg a tio n

C

V isco s ityE

D

B

AT im e

A = P as te in itia tio n tem p era tu re

B = P eak P as te T im e

C = P eak V isco s ity

D /C = S tab ility ra tio

E /D = S e t b ack ra tio

A = P as te in itia tio n tem p era tu re

B = P eak P as te T im e

C = P eak V isco s ity

D /C = S tab ility ra tio

E /D = S e t b ack ra tio

50 65T em p 90 95 8050 65T em p 90 95 80

Starch Gelation and Pasting

Gelatinization and Pasting

“Starch gelatinisation is the collapse (disruption of molecular order) within the starch granule, manifested in irreversible changes in properties such as granular swelling, native crystalline melting, loss of birefringence and starch solubilisation. The point of initial gelation and the range over which it occurs is governed by the starch type, concentration, method of observation, granular type and heterogeneities within the granule population under observation.”

“Pasting is the phenomenon following gelatinisation in the dissociation of starch. It involves granular swelling, exudation of molecular components from the granule; and eventually the total disruption of the granules”

Pasting Cycle

Pasting characteristics of different native starches (from Food Additives, 2nd Ed 2002, Brane et al. Eds)

Gelatinization of starches

Type % Amylopectin % Amylose Gelatinization Range °C Granule Size m

Corn 73 27 62-72 5-25

Waxy Corn 99 1 63-72 5-25

High Amylose 20-45 55-80 67-100+ 5-25

Potato 78 22 58-67 5-100

Rice 83 17 62-78 2-5

Tapioca 82 18 51-65 5-35

Wheat 76 24 58-64 11-41

Exogenous and Endogenous Effects on Starch Pasting Characteristics

Acid

pH

Sugar

Lipids

Proteins

Shear

Vis

co

sit

y

T im e

C o rn s ta rc h + w ate r

C o rn s ta rch + w ate r + 1 .7 % a ce tic ac id

Vis

co

sit

y

T im e

C o rn s ta rc h + w ate r

C o rn s ta rch + w ate r + 1 .7 % a ce tic ac id

Vis

co

sit

y

T im e

C o rn s ta rc h + w ate r

C o rn s ta rch + w ate r + 1 .7 % a ce tic ac id

Effect of Acid on Starch Pasting

p H 4

p H 10

p H 2 .5

Vis

co

sit

y

T im e

p H 4

p H 10

p H 2 .5

Vis

co

sit

y

T im e

Effect of pH on Pasting of Corn Starch

Effect of Sugars on Pasting of Corn Starch

Perubahan pati pada:

1. Pra proses/pascapanen

2. Selama proses

3. Pasca proses/penyimpanan

09/03/2012 45

1. Bahan hasil pertanian masih melakukan respirasi

2. Terjadi hidrolisis: (produk mjd lebih manis)

Pati -> maltodekstrin dan gula

3. Terjadi oksidasi:

Glukosa -> energi, CO2 dan air

46

4. Perubahan proporsi pati -> perubahan

tekstur dan rasa bahan (menjadi manis)

5. Pengendalian perubahan dapat ditekan

dengan perlakuan pendinginan (paling ekonomis)

09/03/2012 47

a. Swelling

b. Gelatinisasi

c. Retrogradasi

d. Esterifikasi

e. Hidrolisis

f. Isomerisasi

09/03/2012 48

09/03/2012 49

?

1. Pati bila diberi air akan mengalami pengembangan volume

2. Kekuatan swelling sebanding dengan

meningkatnya suhu larutan pati

1. Peristiwa rusaknya ikatan antarmolekul pada larutan pati dengan naiknya suhu

2. Larutan pati mengalami gelatinisasi (kanji) dan viskositas menjadi tinggi (lebih kental).

09/03/2012 50

09/03/2012 51

09/03/2012 52

1. Terjadi ikatan balik (set back) pada ikatan hidrogen antara gugus OH pada pati

2. Terjadi selama pendinginan.

3. Pati menjadi tidak terlarut.

09/03/2012 53

Amilosa

09/03/2012 54

4. Berhubungan dengan jumlah cabang pada rantai pati

5. Pati ber-amilopektin tinggi (jagung ketan) tidak mengalami retrogradasi pada pendinginan/ pembekuan.

09/03/2012 55

2. Sifat larutan pati hasil esterifikasi:

a. lebih tahan terhadap panas

b. kemampuan hidrolisis rendah

c. stabil dalam pH rendah

d. swelling dapat dihambat meskipun dalam air panas atau mendidih.

1. Pati -> esterifikasi antara gugus OH -> panjang rantai dapat diatur

09/03/2012 56

3. Produk pati ini banyak digunakan sebagai: a. makanan bayi b. salad dressing c. Stabiliser d. pengental

09/03/2012 57

-Dilakukan dengan: a. pH rendah b. Pemanasan suhu tertentu (mempercepat kerja enzim) c. tekanan tinggi d. Penambahan enzim (amilase) -hasil dari proses: pati --> dextrin maltosa -> glukosa

09/03/2012 58

-Banyak digunakan dalam industri bahan pemanis

dari tepung tapioka

-> industri HFS (High fructose syrup).

09/03/2012 59

09/03/2012 60

09/03/2012 61

09/03/2012 62

09/03/2012 63

a. Proses isomerisasi merupakan perubahan glukosa -> fruktosa

b. Tingkat kemanisan fruktose

meningkat 3 kali lipat dibanding

glukosa

09/03/2012 64

3. Menggunakan enzim isomerase

4. Teknik yang digunakan adalah imobilized

enzyme

-enzim diambil dari mikroba dan dijerap

dalam matrik resin

-larutan glukosa dilewatkan kolom yang berisi

imobilized enzim

1. Higroskopis,

Tepung yang mengandung gula reduksi cenderung mudah menyerap uap air, kemasan harus kedap air, dan ruang RH rendah

2. Perubahan aroma

Timbulnya bau (jawa=apek) yang dimulai dengan menyerap uap air atau penyimpanan yang terlalu lama

09/03/2012 65

3. Perubahan warna

Timbul warna kuning kecoklatan akibat oksidasi dan penyimpanan terlalu lama

4. Serangga dan Rodentia

Akibat sanitasi gudang dan kemasan yang kurang baik

09/03/2012 66

Sumber Pati Amilosa (%) Ukuran Granula

(Um)

Rerata Ukuran

(Um)

Beras ketan 0 2 – 15 6

Jagung ketan 70 4 – 20 10

Jagung 28 5 – 25 14

Ubi kayu 17 3 – 30 14

Ubi jalar 18 4 – 40 7 dan 20

Gandum 26 3 – 35

Ubi garut 21 9 – 40 19

Sagu 26 15 – 50 23

Kentang 20 10 - 100 33