The Storage of Grain and Aging of
Flour, And Its Effects On Flour
Functionality
Omar Miranda
1
Garcia ,
Andrew
2
Ross ,
Ph.D
Bioresource Research1, Department of Crop and Soil Science2,
Oregon State University, Corvallis, OR, 97331
Introduction: Wheat
• Annual global production ~ 600
million metric tons
• USA produces ~ 50 to 60 million
metric tons
• Oregon produces ~ 2 million
metric tons valued at around $500
million
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Wheat types
• Wheat can be found in:
1. hard and soft
2. red and white
3. and in winter and spring growth
habits
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Project focus
• The project focused on soft white (SW)
winter wheat: the main wheat class
produced in the Pacific Northwest.
• Used for baked products such as:
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Grain anatomy and
composition
Grain anatomy
Caryopsis
1. Outer Bran
2. Endosperm
3. Germ
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Flour is primarily endosperm and has
3 main functional components
1. Starch
2. Gluten proteins
3. Arabinoxylans
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3
Flour has 3 main
functional components
• All 3 contribute to overall water
absorption of flour.
• Absorption is highly relevant to
preparation of doughs and batters for
baked goods.
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Relevance
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Starch
• 70% of wheat flour weight: consists of
two types of polymeric glucose:
1. Amylopectin (75%)
2. Amylose (25%)
• Packaged in “granules”
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Starch granules
(Vandeputte & Delcour, 2004)
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Damaged starch granules
• Up to 10% of
granules are
damaged during
milling
• Damaged
granules have
higher absorption
capacity
Gluten
• Found in the endosperm as
gluten-forming proteins.
• Two main components:
1. Polymeric glutenins
2. Monomeric gliadins
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2
Gluten
•
Characteristics of gluten make it the
main quality determinant in bread
making.
•
Though its not a key determinant for
cookie performance, it is a key
determinant of flour functionality for
crackers
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2
Arabinoxylans
•
Arabinoxylans (AX) are located in the
cell walls of the endosperm.
•
Contribute to the texture (softness or
hardness) of the kernel.
•
Two categories:
1. Water un-extractable (WUAX)
2. Water extractable (WEAX)
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Arabinoxylans
• Negative impacts:
Smaller cookie
diameters
• Positive impacts: in
bread-making
WEAX
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2
Flour composition
• Variation in flour composition is
economically and functionally important
for manufacturing processes and the
resulting end-products.
• Different types of wheat are differentially
suitable for any particular end product.
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2
Flour for bread
Production
• High Water
absorption
• High gluten
strength
• Moderately high
damaged starch
• High WEAX
Flour for cookie
Production
• Low water
absorption
• Minimal gluten
strength
• Low damaged
starch
• Low AX
Wheat Flour Aging
• Naturally occurring maturation of
flour when exposed to oxygen and
light.
• Modification of flour parameters.
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Hypothesis
• In SW wheat, aging may increase
absorption properties of the flour.
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Aims
The aim of this study was to determine
if absorption capacity of SW wheat
flour changes as a response to grain
storage and flour aging using Solvent
Retention Capacity Test (SRC: a
measure of flour absorption capacity
and functionality).
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Aims
To determine if SRC testing can be
done immediately after harvest and/or
milling or whether a period of aging
was necessary to obtain valid flour
functionality measurements.
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Materials and Methods
Materials and testing schedule
• Double aging study
 Grain and Flour
•
4 Different varieties were chosen
 Based on preliminary data obtained
from surveying grain from a
prior harvest
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Materials and testing schedule
• Grain from 4 soft-wheat varieties
1. Tubbs
2. Goetze
3. Skiles
4. Bobtail
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Materials and testing schedule
Grain Aging
Week 0
Week 3
Week 6
Week 12
Week 24
Milling
0
0
0
0
0
1
1
1
1
1
Flour Aging (days)
3
6
13 27
3
6
13 27
3
6
13 27
3
6
13 27
3
6
13 27
SRC Test
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Milling Process
• Milling aims to separate the
anatomical parts of the kernel to
produce flour with minimal inclusion of
bran particles
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Milling Process
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SRC profile
• Four tests, using 3 different aqueous
solutions and water:
• Water
• 5% (w/w) Sodium Carbonate
• 50% (w/w) Sucrose
• 5% (w/w) Lactic Acid
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SRC workflow
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Principle of SRC
Small molecules dissolve in excess
amounts of solvent, but specific macro
polymers can hydrate and easily
entangle rather than dissolve.
Different solvents exaggerate the
swelling of specific polymeric networks.
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Principle of SRC
Water SRC
Damaged starch
Arabinoxylan
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Sucrose SRC
Arabinoxylan
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Carbonate SRC
Damaged starch
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Lactic acid SRC
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Results
Water SRC
Swelling of all Functional Components
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Water SRC
Swelling of all Functional Components
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Sucrose SRC
Arabinoxylans & Gliadins
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Sucrose SRC
Arabinoxylans & Gliadins
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Carbonate SRC
Damaged Starch
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Carbonate SRC
Damaged Starch
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Carbonate SRC
Damaged Starch
Week 0: Days after milling
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Lactic acid SRC
Glutenin
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Lactic acid SRC
Glutenin
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Conclusions
• Systematic differences in SRC were
observed between varieties at all grain
storage and flour aging stages.
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Conclusions
• SRC values of SW wheat did change
in response to grain storage and flour
aging.
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Conclusions
• These results suggest that SRC testing
could be done immediately after harvest
and/or milling, if the primary aim was to
determine differences between varieties.
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Conclusions
• Being able to test differences between
varieties [genotypes] immediately after
harvest is vital for wheat breeding
programs due to the necessity for high
throughput in short time frames.
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Conclusions
• If the primary aim was to predict flour
functionality for commercial production
then the small but significant changes in
SRC across the grain storage and flour
aging periods need to be accounted for.
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Conclusions
• Water and sucrose SRCs showed small
but significant increases across the grain
storage and flour aging periods.
• Partially supports the original hypothesis.
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Conclusions
• Sodium carbonate SRC was significantly
higher when tested on freshly milled flour
from freshly harvested grain.
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Conclusions
• Lactic acid SRCs had significant
decreases across the grain storage and
flour aging periods.
• Partially refutes the original hypothesis.
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Further Research
•In parallel the oxidative gelation test
AX cross linking
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Further Research
AX cross linking
Means and 95.0 Percent LSD Interv als
450
P e a k V i sc .
430
410
390
370
350
0
1
3
6
13
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Flour Age - Days
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Further Research
AX cross linking
Tubbs
900
800
700
Viscocity (cP)
600
Week 0
Week 3
500
Week 6
400
Week 13
Week 24
300
200
100
0
0
50
100
150
Total Days Spent14Aging
200
250
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References
Bettge, A. D., & Morris, C. F. (2007). Oxidative gelation measurement and influence on soft wheat batter
viscosity and end-use quality. Cereal Chemistry, 84(3), 237–242. doi:10.1094/CCHEM-84-3-0237
Delcour, J. A., & Hoseney, R. C. (2010). Principles of Cereal Science and Technology (3, illustrated.).
AACC International.
Duyvejonck, A. E., Lagrain, B., Pareyt, B., Courtin, C. M., & Delcour, J. A. (2011). Relative contribution of
wheat flour constituents to Solvent Retention Capacity profiles of European wheats. Journal of Cereal
Science, 53(3), 312–318. doi:10.1016/j.jcs.2011.01.014
Hoseney, R. C. (1986). Principles of cereal science and technology (Vol. 327). St. Paul, Minnesota, USA;
American Association of Cereal Chemists.
Kweon, M., Slade, L., & Levine, H. (2011). Solvent Retention Capacity (SRC) Testing of Wheat Flour:
Principles and Value in Predicting Flour Functionality in Different Wheat-Based Food Processes and in
Wheat Breeding-A Review. Cereal Chemistry, 88(6), 537–552. doi:10.1094/CCHEM-07-11-0092
Oregon Agriculture & Fisheries Statistics. (2011, 2012). Retrieved May 23, 2013, from
http://www.oregon.gov/ODA/docs/pdf/pubs/agripedia_stats.pdf
Zeeman, S. C., Kossmann, J., & Smith, A. M. (2010). Starch: Its Metabolism, Evolution, and
Biotechnological Modification in Plants. Annual Review of Plant Biology, 61(1), 209–234.
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doi:10.1146/annurev-arplant-042809-112301
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Acknowledgments
•
The Multicultural Scholars Program (MSP)
•
National Institute of Food and Agriculture (NIFA)
•
US Department of Agriculture (USDA);
•
College of Agricultural Sciences, ER Jackman
Internship Support Program
•
College of Agriculture Sciences, Calvin & Merle
Smith Wheat Research Endowment Fund
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Acknowledgments
•
Wanda Crannell
•
Dr. Andrew Ross
•
Dr. Michael Penner
•
Dr. Katharine Field
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