The undersigned, appointed by the Dean of the - MOspace

89 Pages·2008·1.02 MB·English

PROPERTIES OF EXTRUDED WHITE CORN FLOUR-
HIGH AMYLOSE CORN STARCH PUFFS

A Thesis
presented to
the Faculty of the Graduate School
University of Missouri

In Partial Fulfillment
Of the Requirements for the Degree

Master of Science

by
ELIZABETH KOESTER

Dr. Fu-Hung Hsieh, Thesis Supervisor

DECEMBER 2008
The undersigned, appointed by the Dean of the Graduate School, have examined the
thesis entitled

PROPERTIES OF EXTRUDED WHITE CORN FLOUR-
HIGH AMYLOSE CORN STARCH PUFFS

presented by Elizabeth Koester,

a candidate for the degree of Master of Science,

and hereby certify that, in their opinion, it is worthy of acceptance.

__________________________________________________________________
Dr. Fu-Hung Hsieh, Departments of Biological Engineering and Food Science

__________________________________________________________________
Dr. Steve Borgelt, Department of Biological Engineering

__________________________________________________________________
Dr. Mark Ellersieck, Department of Statistics
ACKNOWLEDGEMENTS

I would first like to thank my advisor, Dr. Hsieh, for all of his support through my
Master’s project(s). I will never be able to thank you enough for all your help, advice,
guidance and understanding. I really appreciate you working around my crazy life the
last few years, allowing me to complete this degree.
A very special thank you goes out to Mr. Harold Huff for all of his technical
expertise and assistance and for demanding that I continue the project to completion.
Thank you so much for seeing me through the discouragement, frustration, anxiety and
sorrow that I experienced through the course of my Master’s experience. Your friendship
has meant so much to me, and I will always treasure the memories, laughs and a very
special dance.
I would also like to thank Dr. Mark Ellersieck and Dr. Steve Borgelt for serving
on my committee; I greatly appreciated your guidance and support.
Additionally, I would like to thank Drew and Hannah for reminding me that it’s
okay to ask for help and that I don’t always need to do everything myself. I really
enjoyed getting to know you both and really appreciate all the hard work you put into this
project.
Lastly I would like to thank my family for raising me in a loving Christian home
where I was taught that all things are truly possible and that no dream is too big. And
finally my husband, for helping me keep life in perspective and not letting me stay ‘lost
in the books’ for too long at a time.
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TABLE OF CONTENTS

ACKNOWLEDGEMENTS…………………………...…………………………………..ii
LIST OF TABLES………………………………………………………………………...v
LIST OF FIGURES……………………………………………………………………..viii
ABSTRACT……………………………………………………………………………...ix
Chapter
1. INTRODUCTION………………………………………………………………...1
2. LITERATURE REVIEW…………………………………………………………3
2.1. Extrusion ………………………………………………………………...3
2.1.1. Snack foods……………………………………………………4
2.1.2. RTE breakfast cereals…………………………………………6
2.2. Corn……………………………………………………………....………9
2.2.1. Starch………………………………………………………...10
2.2.2. Gelatinization………………………………………………...12
2.2.3. Retrogradation………………………………………………..13
2.2.4. High-amylose starch…………………………………………14
2.3. Water Activity…………………………………………………………..16
2.4. Glass Transition Temperature…………………………………………..17
3. MATERIALS AND METHODS………………………………………...………18
3.1. Raw Materials…………………………………………………………..18
3.2. Experimental Design……………………………………………………19
3.3. Extrusion………………………………………………………………..21
3.4. Analysis of Product Properties………………………………………….24
3.4.1. Length, width and expansion………………………………...24
3.4.2. Per piece weight……………………………………………...24
3.4.3. Bulk density………………………………………………….24
3.4.4. Apparent bulk density………………………………………..24
3.4.5. Specific volume……………………………………………...24
3.4.6. Color…………………………………………………………25
3.5. Texture Profile Analysis………………………………………………..26
3.6. Controlled Water Activity Analysis…………………………………….27
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3.6.1. Sample preparation at controlled water activity……………..27
3.6.2. Texture profile analysis at controlled water activity…….…...27
3.6.3. Glass transition……………………………………………….28
3.7. Data Analysis…………………………………………………………...29
4. RESULTS AND DISCUSSION………………………………………………....30
4.1. Extruder Responses……………………………………………………..30
4.1.1. Die temperature………………………………………………30
4.1.2. Product temperature………………………………………….30
4.1.3. Torque………………………………………………………..31
4.1.4. Specific mechanical energy………………………………….31
4.1.5. Die pressure………………………………………………….32
4.1.6. Extrusion parameter correlations…………………………….36
4.2. Product Properties………………………………………………………38
4.2.1. Length and width…………………………………………….40
4.2.2. Expansion…………………………………………………….41
4.2.3. Per piece weight……………………………………………...42
4.2.4. Bulk density………………………………………………….42
4.2.5. Apparent bulk density………………………………………..43
4.2.6. Specific volume……………………………………………...43
4.2.7. Color…………………………………………………………44
4.2.8. Product property correlations………………………………...51
4.3. Texture Profile Analysis………………………………………………..53
4.3.1. Breaking strength…………………………………………….53
4.3.2. Hardness……………………………………………………...53
4.4. Controlled Water Activity Analysis…………………………………….56
4.4.1. Equilibrated moisture content………………………………..56
4.4.2. Breaking strength………………………………….…………56
4.4.3. Hardness……………………………………………………...57
4.4.4. Glass transition……………………………………………….61
5. CONCLUSIONS AND RECOMMENDATIONS………………………………63
5.1. Conclusions……………………………………………………………..63
5.2. Recommendations………………………………………………………65
Appendix
A……………………………………………………………………………………...66
REFERENCES…………………………………………………………………………..73
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LIST OF TABLES

Table Page
2.2.1. Industrial uses of starch………......……………………………………………..12
3.1.1. Proximate composition of ingredients………………...…………...……………18
3.1.2. Percent composition of the four batches……………………………………...…18
3.2.1. Moisture content code assignments………………...…………………………...20
3.3.1. Screw profile……………………………………………………………...……..21
3.3.2. Extruder barrel zone temperatures………………………...…………………….22
3.6.1. Saturated salt solutions……...…………………………………………………..27
4.1.1. Effects of high-amylose corn starch, moisture content, and screw speed on
die temperature(°C)…….………………….…………………………………...33

4.1.2. Effects of high-amylose corn starch, moisture content, and screw speed on
product temperature (°C)…….………………………………………………...33

4.1.3. Effects of high-amylose corn starch, moisture content, and screw speed on
torque (%)……………………………………………………………………...34

4.1.4. Effects of high-amylose corn starch, moisture content, and screw speed on
specific mechanical energy (kJ/kg)…………………………………………….34

4.1.5. Effects of high-amylose corn starch, moisture content, and screw speed on
die pressure (kPa)………………………………………………………………35

4.1.6.1. Correlations between extrusion parameters……………………………………..36
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4.1.6.2. Correlations between extrusion parameters and product textural properties……37
4.2.1. Effects of high-amylose corn starch, moisture content, and screw speed on
puff length (mm)……………………………………………………………….46

4.2.2. Effects of high-amylose corn starch, moisture content, and screw speed on
puff width (mm)………………………………………………………………..46

4.2.3. Effects of high-amylose corn starch, moisture content, and screw speed on
puff expansion………………………………………………………………….47

4.2.4. Effects of high-amylose corn starch, moisture content, and screw speed on
per piece weight (g)……………………………………………………………47

4.2.5. Effects of high-amylose corn starch, moisture content, and screw speed on
bulk density (g/mL)…………………………………………………………….48

4.2.6. Effects of high-amylose corn starch, moisture content, and screw speed on
apparent bulk density (g/L)…………………………………………………….48

4.2.7. Effects of high-amylose corn starch, moisture content, and screw speed on
specific volume (mL/g)………………………………………………………...49

4.2.8. Effects of high-amylose corn starch, moisture content, and screw speed on
color (L)………………………………………………………………………..49

4.2.9. Effects of high-amylose corn starch, moisture content, and screw speed on
color (a)………………………………………………………………………...50

4.2.10. Effects of high-amylose corn starch, moisture content, and screw speed on
color (b)………………………………………………………………………...50

4.2.8.1,2. Correlations between product and textural properties.………………………..52

4.3.1. Effects of high-amylose corn starch, moisture content, and screw speed on
breaking strength (g/mm2)……………………………………………………..55

4.3.2. Effects of high-amylose corn starch, moisture content, and screw speed on
hardness (g)……………………………………………………………………55

4.4.2. Effects of high-amylose corn starch and water activity on breaking strength…..59

4.4.3. Effects of high-amylose corn starch and water activity on hardness……………60

vi
4.4.4. Effects of equilibrated moisture content on glass transition temperature and
Gordon-Taylor equation goodness-of-fit………………………………………..62
vii
LIST OF FIGURES

Figure Page
2.2.1. Amylose structure………………………………………………………………...10
2.2.2. Amylopectin structure……………………………………………………………11
4.2.1. Puffs containing 0% high-amylose corn starch…………………………………..38
4.2.2. Cross-sections of puffs containing 0% high-amylose corn starch…..……………38
4.2.3. Puffs containing 20% high-amylose corn starch…………………………………39
4.2.4. Cross-sections of puffs containing 20% high-amylose corn starch………………39
4.2.5. Puffs containing 40% high-amylose corn starch…………………………………39
4.2.6. Cross-sections of puffs containing 40% high-amylose corn starch………………39
4.2.7. Puffs containing 60% high-amylose corn starch…………………………………40
4.2.8. Cross-sections of puffs containing 60% high-amylose corn starch………………40
4.4.1. Isotherms as a function of high-amylose starch content……….…………………56
4.4.2. Effects of high-amylose starch content and water activity on breaking strength...59
4.4.3. Effects of high-amylose starch content and water activity on hardness………….60
4.4.4. Effects of equilibrated moisture content on glass transition temperature………...62

viii
PROPERTIES OF EXTRUDED WHITE CORN FLOUR -
HIGH AMYLOSE CORN STARCH PUFFS

Elizabeth Koester

Dr. Fu-hung Hsieh, Thesis Advisor

ABSTRACT

This study was conducted to determine the effect of high-amylose corn starch in
corn puffs on the extrusion parameters, product and textural properties and the glass
transition temperature. The data was analyzed in a randomized complete block design
(RCBD) in which the treatments were arranged in a 4 x 3 x 3 {high-amylose content (0,
20, 40 and 60%) x moisture content (20, 22, and 18 or 24%) x extruder screw speed (200,
300 and 400 rpm)} factorial arrangement of treatments with two replicants.
The collected results indicate that the maximum amount of expansion occurs
when the screw speed and moisture content are both decreased and the high-amylose corn
starch content is increased. The puff density increased and the specific volume decreased
when screw speed and starch content decreased and moisture content increased. While
the original puff breaking strength and hardness were only affected by the moisture
content, the puffs containing more high-amylose corn starch exhibited significantly
higher breaking strengths at higher water activities. The extruder responded to increases
in screw speed and starch content and a decrease in moisture content with increases in
temperature and specific mechanical energy. The Gordon-Taylor equation was used to
predict the effect of water plasticization on the high-amylose corn puffs.
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