ENDRIKA WIDYASTUTI FOOD SCIENCE AND TECHNOLOGY AGRICULTURAL TECHNOLOGY BRAWIJAYA UNIVERSITY 2012

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FOOD SCIENCE AND TECHNOLOGY AGRICULTURAL TECHNOLOGY BRAWIJAYA UNIVERSITY 2012

ENDRIKA WIDYASTUTI

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09/03/2012 2

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Starch Ingredients

 Must be cooked

 Gel slowly

 Show syneresis

 Break down under shear

 Break down under acid conditions

 Forms complexes

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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)

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Unheated starch granule

Heated starch granule

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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

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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

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 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

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Amylopectin in

Granules

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Amylopectin structure (Chaplin, 2004)

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Amylopectin General Structure

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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

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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

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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%

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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

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Starch Granule

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Granule Structure

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Functions

 Gelatinization

 Structure in baked products

 Thickener in sauces, soups, and dressings

 Dextrinization

 Gelation

 Pie filling

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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

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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

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Gelatinization and Temperature

 Gradually thicken with temperature

 Can be heated to 100^oC without much granule rupture

 If held at 95^oC will implode and lose viscosity

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Gelatinization and Type of

Starch

 Best thickening ability: potato starch

 Worst thickening

ability: wheat starch

 More

amylopectin=more translucent=more stringy

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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

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Viscosity and Type of Starch

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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

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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

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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

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Gelation and Other Effects

 Sugar

 Decreases gelatinization and amylose release

 Softer gel

 Acid

 Decreases gelatinization by hydrolysis of granules

 Softer gel

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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

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Dextrinization

 When starch is heated without water

 A higher temperature is reached than with water

 Bonds break throughout the starch forming dextrins

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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

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Visco/Amylo/Graph

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ViscoAmyloGraph

Time

Viscosity

65^oC

90^oC 30^oC

heating constant temperature

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A m y lo s e

S w e llin g C o lla p s e A g g r e g a tio n C

V is c o s ity E

D

B

A

T im e

A = P a s te in itia tio n te m p e r a tu r e B = P e a k P a s te T im e

C = P e a k V is c o s it y D /C = S ta b ilit y r a tio E /D = S e t b a c k r a tio

5 0 6 5

T e m p 9 0 9 5 8 0

A m y lo s e

D

B

A

T im e

5 0 6 5

T e m p 9 0 9 5 8 0

A m y lo s e

D

B

A

T im e

5 0 6 5

T e m p 5 0 6 5 9 0 9 5 8 0

T e m p 9 0 9 5 8 0

Starch Gelation and Pasting

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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”

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Pasting Cycle

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Pasting characteristics of different native starches

(from Food Additives, 2^nd Ed 2002, Brane et al. Eds)

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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

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Exogenous and Endogenous Effects on Starch Pasting Characteristics

 Acid

 pH

 Sugar

 Lipids

 Proteins

 Shear

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Viscosity

T im e

C o r n s ta r c h + w a te r

C o r n s ta r c h + w a te r + 1 .7 % a c e tic a c id

Viscosity

T im e

Viscosity

T im e

Effect of Acid on Starch Pasting

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p H 4

p H 1 0

p H 2 .5

Viscosity

T im e

p H 4

p H 1 0

p H 2 .5

Viscosity

T im e

Effect of pH on Pasting of Corn Starch

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Effect of Sugars on Pasting of Corn Starch

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Perubahan pati pada:

1.

Pra proses/pascapanen

2.

Selama proses

3.

Pasca proses/penyimpanan

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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

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4. Perubahan proporsi pati -> perubahan tekstur dan rasa bahan (menjadi manis) 5. Pengendalian perubahan dapat ditekan dengan perlakuan pendinginan (paling ekonomis)

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a.

Swelling

b.

Gelatinisasi

c.

Retrogradasi

d.

Esterifikasi

e.

Hidrolisis

f.

Isomerisasi

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?

1. Pati bila diberi air akan mengalami pengembangan volume

2. Kekuatan swelling sebanding dengan

meningkatnya suhu larutan pati

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1. Peristiwa rusaknya ikatan antarmolekul pada larutan pati

dengan naiknya suhu

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

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1. Terjadi ikatan balik (set back) pada

ikatan hidrogen antara gugus OH pada pati

2. Terjadi selama pendinginan.

3. Pati menjadi tidak terlarut.

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Amilosa

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4. Berhubungan dengan

jumlah cabang pada rantai pati

5. Pati ber-amilopektin

tinggi (jagung ketan) tidak mengalami retrogradasi

pada pendinginan/

pembekuan.

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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

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3. Produk pati ini banyak digunakan sebagai:

a. makanan bayi b. salad dressing c. Stabiliser

d. pengental

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-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

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-Banyak digunakan dalam industri bahan pemanis dari tepung tapioka

-> industri HFS (High fructose syrup).

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a. Proses isomerisasi merupakan perubahan glukosa -> fruktosa b. Tingkat kemanisan fruktose

meningkat 3 kali lipat dibanding

glukosa

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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

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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

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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

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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