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Instrumental and Sensory Characteristics of a Baked Product Containing Barley
Flour with Varying Amounts of Beta-Glucan and Sugar Substitute
by
Niti Lathia
A Thesis submitted to the
Graduate School-New Brunswick
Rutgers, The State University of New Jerseyin partial fulfillment of the requirements
for the degree of
Master of Science
Graduate Program in Food Science
written under the direction of
Dr. Henryk Daun
Dr. Paul Takhistov
and approved by
________________________
________________________
________________________
New Brunswick, New Jersey
October 2011
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ABSTRACT OF THE THESIS
Instrumental and Sensory Characteristics of Baked Product Containing Barley
Flour with Varying Amounts of Beta-Glucan and Sugar Substitute
By Niti Lathia
Thesis Directors:
Dr. Henryk DaunDr. Paul Takhistov
The objective of this study was to determine the influence of varying levels of
beta-glucan in barley flour on selected properties of a model baked product. Another aim
was to reduce sugar levels in the product by incorporating a natural sweetener stevia and
to monitor its influence using instrumental and sensory analysis. Batter rheology was
studied using a lubricated squeezing flow technique, pasting profiles of the barley flours
were determined with a rheometer, viscoelastic properties were evaluated using dynamic
oscillatory rheology to measure G and G, and firmness of the baked products was
monitored using a texture analyzer, for changes occurring due to varying -glucan levels
in barley flour and removal of sugar. L a* b* color values of barley flour and muffins
were obtained using a colorimeter. A descriptive sensory panel was trained to observe
changes in product attributes when stevia was used to replace sugar in the high beta-
glucan product.
Water absorption index was found to be significantly higher for high -glucan
barley flour. The color of both barley flours also had a significant difference in L*
(lightness) and b* (yellowness) values. Similarly, muffin samples prepared without
sugar, using stevia, were significantly lighter in surface color (higher L*), while the
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interior colors were darker (higher b*). Low beta-glucan dough showed a lower biaxial
extensional viscosity compared to the high beta-glucan dough, which indicates that the
level of beta-glucan present in the barley flour has an impact on the dough viscosity. The
pasting profiles of the flours were also found to be significantly different, where the high
beta-glucan barley flour resulted in a significantly higher peak viscosity but lower peak
time compared to low -glucan barley flour. Muffin firmness was found to be
significantly higher when sugar was omitted from the formulation, but there was no
significant difference in firmness among the two beta-glucan levels in the muffins. The
sensory descriptive panel found significantly higher firmness, surface roughness, and
bitterness attributes for the high -glucan muffins prepared with stevia. Additional
efforts will be needed to mask the undesirable attributes in the model baked product
occurring due to the removal of sugar.
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Acknowledgement
First and foremost, I would like to express my sincere gratitude towards both of
my thesis advisors, Dr. Henryk Daun, who brought the project to my attention, and
equally to Dr. Paul Takhistov whose lab I conducted my research in. Both professors
have provided guidance, support, encouragement, and have had patience in explaining
my numerous inquiries throughout the duration of my project research. Secondly, I
would like to thank Dr. Kit Yam for being on my thesis defense committee, whose input
and suggestions I value. In addition, a big thank you to my lab mates for their assistancewith learning new instrumentation as well as providing a fun learning environment.
Also, I appreciate the efforts of the undergraduate team of students that participated in the
sensory portion of this research as panelists; your help and cooperation was greatly
appreciated.
Most importantly, I would like to thank my parents and family for providing the
financial support for my graduate studies as well as love, encouragement, moral support,
providing comfort during the challenging times, and accepting my absence while I
worked towards completing my degree. I have relied on them for guidance and strength
throughout my academic career. Thank you for your confidence and unwavering support.
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TABLE OF CONTENTS
Page
ABSTRACT OF THESIS ii-iii
ACKNOWLEDGEMENTS iv
TABLE OF CONTENTS v
LIST OF ABBREVIATIONS vii
LIST OF TABLES viii
LIST OF ILLUSTRATIONS ix
LITERATURE REVIEW CHAPTER ONE
1.0 Introduction 1
1.1 Health Benefits of Barley 4
1.2 Chemical and Physical Characteristics of Barley 10
1.3 -Glucans and Arabinoxylans 13
1.4 Properties and Molecular Interactions among Major Food Components 17
1.5 Beta-glucan extraction 17
1.6 Water absorption capacity and effect on end-products 19
1.7 Rheological Properties Influenced by barley flour beta-glucan content 21
1.8 Stevia as a Sweetening Agent in Consumer Products 22
1.9 Conclusions from Literature Review and Objectives for Research 24
MATERIALS AND METHODS CHAPTER TWO
2.1 Ingredients Used in Baking Procedures and Analytical Measurements 26
2.2 Water Absorption Index of Low and High -glucan Barley Flour 27
2.3 Microbakery Model Formulations for Barley Muffins 29
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2.4 Rise and Moisture Loss of Muffins 32
2.5 Rheological properties of barley dough using lubricatingsqueezing flow technique 33
2.6 Pasting Properties of High -glucan and low -glucan barley flours 36
2.7 Dynamic Rheological Properties of Muffin Batter 39
2.8 Assessing Muffin Firmness Using a Texture Analyzer 40
2.9 Evaluation of Colors Using a Colorimeter 42
2.10 Nutritional Comparison of Muffins 44
2.11 Sensory Methodologies Used to Evaluate Muffin Products 45
RESULTS AND DISCUSSION CHAPTER THREE
3.1 Water absorption values for barley flours 50
3.2 Increase in Muffin Heights After Baking 51
3.3 Muffin Moisture Loss After Baking 53
3.4 Rheological Properties of barley flour doughs and muffin batters 55
3.5 Pasting properties of barley flours 62
3.6 Color values for Barley Flour Varieties 64
3.7 Muffin Surface Color 66
3.8 Muffin Interior Color 71
3.9 Muffin Firmness 74
3.10 Nutrition Facts for Muffin Formulations 77
3.11 High -glucan Muffin Sensory Quantitative Descriptive Analysis 79
3.13 Conclusions and Suggestions for Future Work 85
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LIST OF ABBREVIATIONS
United States Department of Agriculture (USDA)
National School Lunch Program (NSLP)
National Health and Nutrition Examination Survey (NHANES)
Dietary Reference Intakes (DRI)
Recommended Daily Allowances (RDA)
Coronary Heart Disease (CHD)
Low density lipoprotein (LDL)
Food and Drug Administration (FDA)Code of Federal Regulations (CFR)
Apparent Biaxial Extensional Viscosity (ABEV)
The International Commission on Illumination (CIE)
Rapid Visco Analyzer (RVA)
Quantitative Descriptive Analysis (QDA)
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LIST OF TABLES
Table 1: Nutritional Composition of Sustagrain Barley
Table 2: Average Nutrient Comparison for Hulless Barley, Oats, and barley variety
Prowashonupana (Prowash) Barley
Table 3: Formulations for Muffin Batters Used to Prepare a Model Baked Product
Table 4: Reference standards for selected attributes used in Spectrum DescriptiveAnalysis panel
Table 5. Descriptors used to evaluate muffin samples in the QDA panel
Table 6: Water Absorption indices of high and low -glucan barley flour
Table 7: Percentage Increase in Muffin Height (Rise) After Baking
Table 8: Percentage Decrease in Muffin Weight (Moisture Loss) After Baking
Table 9: Pasting profile for low and high -glucan barley flours
Table 10: Consistency index and flow behavior index for muffin batter with varyingamounts of beta-glucan and sugar
Table 11: Average L a*b* Values for low -glucan and high -glucan Barley FlourVarieties
Table 12: Average L, a*, b* color values for surface color of muffins prepared with lowor high -glucan barley flour with 100% sugar
Table 13: Average L, a*, b* color values for surface color of muffins prepared with lowor high -glucan barley flour with 0% sugar
Table 14: The average L, a*, b* color values for interior color of muffins prepared withlow or high -glucan barley flour with 100% sugar
Table 15: The average L, a*, b* color values for interior color of muffins prepared with
low or high -glucan barley flour with 0% sugar
Table 16: Average maximum peak force to compress muffins as a measure of firmness
Table 17: Nutrition Facts for Muffin Formulations
Table 18: The mean values of each attribute measured by the QDA panel for muffinsprepared with Sustagrain flour with 100% sugar and 0% sugar, sweetened with stevia
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LIST OF ILLUSTRATIONS
Figure 1: Molecular Structure of -(1 3)- and -(1 4)-glucan
Figure 2: Structural elements present in arabinoxylans
Figure 3: Extraction and purification of -glucans from barley and oats
Figure 4: Structural Components of Stevioside, Rebaudioside A, and Steviol
Figure 5: Nutrition Label for Bobs Red Mill Ground Flaxseed Meal and Bobs Red Millbarley flour
Figure 6: Example of water separated from barley flour after centrifugation
Figure 7: Apparatus and set-up of TA.XT2 Texture Analyzer for Lubricated Squeezing
Flow Technique Analysis of Doughs Prepared Using Barley FloursFigure 8: Typical RVA pasting profile of a normal maize starch for viscosity andtemperature as a function of time
Figure 9: Water absorption indices of high and low -glucan barley flour
Figure 10: Percentage Increase in Muffin Height (Rise) After Baking
Figure 11: Percentage Decrease in Muffin Weight (Moisture Loss) After Baking
Figure 12: Biaxial Extensional Viscosity as a Function of Biaxial Strain Rate forSustagrain Dough and Bobs Red Mill Barley Flour Dough
Figure 13: Pasting profile for low and high -glucan barley flours
Figure 14: Strain vs. shear rate relationship of muffin batter with varying levels of beta-glucan and sugar
Figure 15: Effect of % Strain on G of muffin batters containing varying amounts of beta-glucan
Figure 16: Effect of % Strain on G of muffin batters containing varying amounts ofbeta-glucan
Figure 17: Average L a*b* Values for low -glucan and high -glucan Barley FlourVarieties
Figure 18: Visual Difference in Flour Color.
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Figure 19: Surface color values for muffins prepared with low -glucan Bobs Red Millbrand barley flour
Figure 20: Muffins prepared with low -glucan Barley Flour
Figure 21: Surface color values for muffins prepared with high -glucan barley flour
Figure 22: Muffins prepared with high -glucan Barley Flour
Figure 23: Interior color values for muffins prepared with low -glucan barley flour
Figure 24: Interior Surface Images of Muffins Prepared with low -glucan barley Flour.
Figure 25: Interior color values for muffins prepared with high -glucan barley flour
Figure 26: Interior Surface Images of Muffins Prepared with high -glucan barley flour
Figure 27: Typical texture profile curve for high -glucan muffins prepared with 100%sugar and 0% sugar
Figure 28: The average maximum peak force to compress muffins as a measure offirmness
Figure 29: The mean values of attributes measured by the QDA panel for muffinsprepared with high -glucan barley flour with 100% sugar and 0% sugar, sweetened withstevia
Figure 30: Sweet steviol glycosides from leaves of Stevia rebaudiana
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CHAPTER 1
LITERATURE REVIEW
1.0 Introduction
The history of barley usage dates back to approximately 8000 B.C. and is
considered one of the oldest cultivated crops as it was a mainstay of ancient civilization
and contributed to the diet of working class people up until the end of the 19 thcentury.
Many food products such as porridges, broths, hard biscuits, and flat breads were
prepared utilizing barley. The fermentation of the grain led to the production of varioustypes of alcoholic beverages, beer being one of the most well-known and second highest
consumed alcoholic beverage today following wine (Jones 2009). Although barley has
lost its place as a primary staple for modern times, mainly due to the introduction and
proliferation of the wheat industry, the health benefits and functional food uses are being
discovered and it is emerging as a major ingredient in current food formulations
(Anonymous 2005).
The concept of functional foods has been gaining much attention in the recent
times. Although there is no legislative definition of a functional food, one of the well-
accepted definition is Food similar in appearance to conventional food that is intended
to be consumed as part of a normal diet, but has been modified to subserve physiological
roles beyond the provision of simple nutrient requirements (Sir, Kpolna et al. 2008).
Similarly, The Institute of Medicine's Food and Nutrition Board defined functional foods
as "any food or food ingredient that may provide a health benefit beyond the traditional
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nutrients it contains" (Hasler 1998). Thus, fiber rich foods can be considered as a
functional food as it provides health benefits to the consumer.
One pressing issue in the American schools has been that of childhood obesity.
Over one-third of children ages 12 to 19 years old are overweight (Ogden, Carroll et al.
2008) and the prevalence of childhood obesity has increased three-fold from 1980 to
2000 according to Center of Disease Control Health data Division of Adolescent and
School Health (2008). The health consequences and social difficulties associated with
childhood obesity make this a tremendously problematic situation. As a result, many
institutions and individuals are involved in trying to figure out the sources and solutionsto childhood obesity. National data show that children who participate in the National
School Lunch Program (NSLP) obtain over half of their daily total food energy from
school meals. Many social programs have been established at the schools, but the main
way to target the problem is by targeting food products that are consumed by the school
children. One such way is to introduce nutritionally-sound and wholesome food products
into the school lunch programs, which are consumed by children and adolescents
everyday in the public schools. It is crucial that the product shall maintain quality
through processing, storage, preparation, and serving. Most importantly, it should
provide sensory acceptability among children so that it will be fully consumed and thus
provide the intended nutritional and health benefits.
The United States Department of Agriculture (USDA) oversees a nationwide
program called National School Lunch Program (NSLP), which provides and manages all
breakfast and lunch meals being served to students in the public school system. The goal
of the program is to provide healthy, nutritious and wholesome food products to school
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children that choose to consume meals provided at the public schools. As part of the
NSLP, the USDA sets federal nutrition requirements for the schools to follow when
creating a menu plan. The nutritional values of the meals served to students are reported
to the government as a weekly average. Federal nutrition requirements are that the meals
meet one third of the Recommended Daily Allowances (RDA) for protein, calcium, iron,
vitamin A and vitamin C as appropriate for the levels for the age group served. The
meals should also be limited to 30% calories from fat and 10% calories from saturated
fat. Along with these guidelines, the schools should also try to be consistent with the
most current Dietary Guidelines of America (2005) (USDA 2009).One prevalent issue is the lack of consumption of fiber rich foods in childrens
diets. In a study conducted by The National Health and Nutrition Examination Survey
(NHANES), it was determined that grain based dessert products account for only 5% of
the total fiber consumption in the diets of children and adolescents between the ages 2-18
(2010). In 2002, the National Academy of Sciences released the Dietary Reference
Intakes (DRI) for macronutrients and fiber, which recommended that Americans of all
ages consume 14 g total fiber per every 1,000 kcal total energy intake, based on evidence
for reduced cardiovascular disease risk at that level. In addition, fiber protects against
constipation and has also been shown to have many other health benefits, including
decreased risk of some cancers, obesity, cardiovascular disease, and diabetes. One
striking result of this study was that the main sources of fiber in childrens diets were
foods that were relatively low in fiber density (eg, low-fiber fruits) (Sibylle, Diane et al.
2005). Thus, it is necessary to develop products with high fiber content which is aimed
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toward the school lunch program and can contribute to the total daily fiber consumption
recommendation as given in the DRI.
1.1 Health Benefits of Barley
Historically, barley has been used in many Asian, European, and African
countries in various products such as soups, flat breads, and porridges. Although the use
of barley declined through the 19thand 20thcentury as wheat and rice became more
prominent in the global diet, the various health benefits of barley are being discoveredand it is now known to be an excellent source of whole grain. Thus, it is becoming an
increasingly desirable product to use in formulations (Baik and Ullrich 2008). There are
numerous health benefits of barley flour, which are predominantly attributed to the fiber
present in the commodity.
1.1.1 Fiber content of barley
Dietary fiber is a major component of whole grains, which has low energy
density, and has been shown to act as a satiating ingredient. In fact, the current
recommendation for Americans for daily fiber consumption is between 25-35 g, with a
quarter of that amount required as soluble fiber (Hecker, Meier et al. 1998). One group
of dietary fibers, particularly the soluble fibers, is usually viscous or gel-forming.
Viscous dietary fibers, present in some whole grains such as oats and barley, create
gastric distention and delay gastric emptying. Subsequently, satiety-related hormones are
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produced, which signal fullness. Thus, the consumption of whole grains containing
soluble fibers has been shown to increase satiety and thus thought to reduce overall
energy intake in a meal. Compared to other grains, barley contains a relatively high
concentration of beta-glucan, a viscous and fermentable dietary fiber, and therefore may
be highly satiating. Sustagrain barley, which contains 50% of the soluble fiber as beta-
glucan, was given to human subjects to study its effect on satiety along with oatmeal and
rice products, which contain fewer grams of fiber per serving. It was found that the
barley product, which contained the highest amount of fiber, was the most satiating as it
left subjects feeling not as hungry for the next meal when compared to meals where therice and oatmeal products were consumed (Schroeder, Gallaher et al. 2009).
The arabinoxylans present in barley are a source of insoluble fiber. It has been
found that enzymes present in the colon can specifically hydrolyze arabinoxylans,
resulting in arabinoxylan oligosaccharides. These oligosaccharides are said to have a
prebiotic effect, meaning that they promote the growth of beneficial bacteria in the gut.
Soluble dietary fibers play a role in the reduction of blood cholesterol and postprandial
blood glucose and insulin. Soluble arabinoxylans may possess these qualities as well
(Beaver 2008).
1.1.2 Effect of Barley on Glycemic Index and Insulin Response
The concept of glycemic index (GI) was first introduced in 1981 as a means for
identifying and classifying carbohydrate-rich foods based on their ability to raise
postprandial blood glucose levels. A lower glycemic response is desirable in both
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healthy and diabetic individuals as it prevents the spiking of blood glucose levels. In a
study done with South Asian chapati flatbreads which contained varying percentages of
barley flour mixed with wheat flour, it was hypothesized that high-molecular weight
barley -glucan added to a food product subjected to mild cooking would be effective in
lowering postprandial glycemia. As predicted, it was found that the higher levels of -
glucan resulted in lower serum glucose levels. The fiber may affect glycemic response
by forming a physical barrier to enzymatic hydrolysis of starch (KNUCKLES, HUDSON
et al. 1997). This suggests that the addition of high level of -glucan containing barley
would be beneficial those individuals and populations that have a prevalence of type-2diabetes (Thondre and Henry 2009).
In another study done with human subjects at a higher risk for insulin resistance,
they were fed varying amounts of -glucan containing Sustagrain barley. It was found
that those who consumed 10 g of -glucan in their diet showed significantly lower spikes
in blood glucose levels, which was measured over a two hour glucose tolerance test. This
is significant for those that are at risk for developing type-2 diabetes or have insulin
resistance, which is often seen in obese individuals and nowadays even in children.
Although a rather larger dose of the barley fiber containing food would need to be
consumed, it is a reasonable amount and shows that it could be very beneficial for
individuals who are at a higher risk for developing type 2 diabetes or have insulin
resistance (Kim, Stote et al. 2009). As this study was done in at-risk women whose
average age was 51.6, it is possible that the amount of barley -glucan necessary for a
similar effect on children or healthy individuals with normal blood glucose and regulated
insulin levels would be much lower.
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In a similar study done with 10 men who were fed bread products as a breakfast
meal prepared with three different levels (35, 50 and 75%) of the (13;14)--glucan
rich barley genotype Prowashonupana, 50% common barley, or 100% white wheat, and
their postprandial blood glucose and insulin responses were measured. It was found that
for the subjects that consumed the bread prepared with 50% and 75% Prowashonupana
barley had a statistically significant reduction in glucose response levels. For bread that
was prepared with a 50% common barley composition, there was not a significant
reduction in postprandial glucose levels. This is an important indication that the higher
percentage -glucan formulated bread had a much more beneficial effect on glucoselevels (stman, Rossi et al. 2006). There is strong evidence from numerous studies that
high fiber, particularly from -glucan in barley, has a beneficial effect on blood glucose
levels and thus could delay or prevent the onset of insulin resistance or diabetes.
1.1.3 Effect of Barley Fiber on Lowering Cholesterol
The fiber components of barley, particularly the soluble -glucan have been
shown to have a cholesterol-reducing effect in a study conducted using rats as a model,
where food products such as tortilla, granola bar, and pudding with added -glucan were
fed. The soluble fraction, which contains mostly pectin, arabinoxylan, and -glucan, has
the ability to lower blood serum cholesterol, through its tendency to increase viscosity in
the intestine, thus affecting the bile acid-cholesterol cycle. Through this mechanism, the
cholesterol-lowering effects occur by blocking the absorption of fat in the intestines
(Hecker, Meier et al. 1998). In another study conducted using human subjects who were
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fed a barley-rich diet, the low-density lipoprotein cholesterol concentration was
significantly lower at week four in the barley group than in the standard group, who were
not fed a diet containing barley (Li, Kaneko et al.).
Coronary Heart Disease (CHD) is the cause of almost 500,000 deaths annually
and the top risk factors for CHD include high total cholesterol levels and high levels of
low density lipoprotein (LDL) cholesterol. Supporting scientific evidence shows that
adding barley to one's diet can contribute to lowering serum cholesterol. As part of its
continuing initiative to provide Americans with the information they need to make
healthy nutritional choices about foods and dietary supplements, in 2005, the Food andDrug Administration (FDA) approved that whole grain barley and barley-containing
products are allowed to carry a claim that they reduce the risk of coronary heart disease
(CHD) under the Code of Federal Regulations (CFR 101.81). Whole barley and dry
milled barley products such as flakes, grits, flour, meal, and barley meal are all products
that can use this health claim. An example of the health claim that may be used on
products is: "Soluble fiber from foods such as [name of food], as part of a diet low in
saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [name of
food] supplies [x] grams of the soluble fiber necessary per day to have this effect." To
qualify for the health claim, the barley-containing foods must provide at least 0.75 grams
of soluble fiber per serving of the food, and the health claim in CFR 101.81 is based on
the consumption of total 3 grams of beta-glucan soluble fiber daily (FDA 2005; NBFC
2006). The addition of this health claim is very important as it is strongly supported by
scientific evidence and will make consumers more aware of the health benefits of
consuming barley products.
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1.1.4 Antioxidant potential from barley
Some recent studies have focused on demonstrating and studying the antioxidant
properties and compounds found in barley. Antioxidants or phenolic structured
antioxidant compounds have been detected in barley and recent studies have shown that
cereals contain more phytochemicals than previously considered. These constituents of
barley are considered to be the most important source of antioxidants in cereals and exist
in both the free as well as bound form. The majority of the free phenolics are found as
flavanol compounds, whereas the bound phenolics are mainly phenolic acids. Both ofthese groups are known to have antioxidant activity and possibly contribute health
benefits. Cereals are therefore claimed to be good sources of natural antioxidants.
Preliminary results suggest that these phenolic acids are absorbed in humans and that
their antioxidant activity may reduce the risk of coronary heart diseases, cancers, and
aging processes (Holtekjlen, Kinitz et al. 2006).
In addition to the potential health benefits associated with phytochemicals, these
phenolic compounds have important functional properties. Firstly, phytochemicals in
grains contribute to product quality in terms of color, flavor, and texture. The phenolic
acids and the flavanol polymers may be perceived as sour, bitter, and astringent.
Secondly, they also influence bread quality by interfering with the dough formation. The
changes in antioxidant properties were studied after baking bread containing barley. The
most significant change was seen among the different barley varieties, but much less after
storage or baking (Holtekjlen, Bvre et al. 2008).
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1.2 Chemical and Physical Characteristics of Barley
1.2.1 Sustagrain Barley Variety
The Sustagrain barley variety is a proprietary barley variety that was developed
by ConAgra Foods through a conventional barley breeding program at Montana State
University in the late 1970s. This particular variety is generically known as
Prowashonupana, which is a waxy, hulless barley variety that has a unique
macronutrient composition. The varietys name is an acronym that represents its grain
characteristics and lineage: PRO: high protein (high lysine); WA: waxy starch; SHO:short awned; NU: nude (hulless); and PANA: derived from the parent barley Compana.
It is much higher in fiber and protein, but lower in starch compared to many other
common cereal grains. Thus, this particular variety of barley can be used to formulate
products with desirable health benefits (Arndt 2006). Sustagrain barley is available as a
fine ground flour or and quick flakes which are tannish-brown in color (ConAgra).
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Sustagrain Barley Nutritional Data (100g Basis)
Calories 390 Vitamin A 0 IU
Calories from Fat 60g Vitamin C 0 mg
Fat 6.5g Calcium 33mg
Saturated Fat 1.8g Iron 3.6mg
Cholesterol 0g Vitamin B1 (Thiamin) 0.6mg
Carbohydrates 64.3g Vitamin B2 (Riboflavin) 0.3mg
Total Dietary Fiber 30g Vitamin B3 (Niacin) 4.6mg
Soluble Fiber 12g Potassium 452mg
Protein 18g Zinc 2.8mg
Sodium 12mg
Table 1: Nutritional Composition of Sustagrain Barley (ConAgra)
1.2.2 Chemical Composition of Sustagrain Barley (Prowashonupana)
The carbohydrate distribution in Prowashonupana barley is at least 30% dietary
fiber and less than 30% starch. This unique composition of fiber to starch is about 2-3
times the amount of fiber and about half the amount of starch compared with other
common cereal grains. Approximately half the dietary fiber, 50%, consists of -glucan.
This particular variety also provides other whole-grain nutrients including healthy lipids,
vitamins, minerals, tocotrienols, and phytonutrients (Arndt 2006).
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Table 2: Average Nutrient Comparison for Hulless Barley, Oats, and barley variety
Prowashonupana (Prowash) Barley (Arndt 2006)
Microscopic and chemical analyses were conducted to compare the structure,
macronutrient distribution, and macronutrient content of Prowashonupana barley variety
to another type of waxy, hulless (naked) barley variety: Bz 489-30. Waxy naked barleys
have previously been reported to contain 51.760.5% starch, 12.616.6% protein, 12.6
20.5% dietary fibre, 2.63.3% fat and 1.53.5% ash, while the content of -glucan has
been shown to vary between 6 and 11% of dry matter. In contrast, the Prowashonupana
variety has been shown to have a lower starch content (21-31%), while the contents of the
dietary fiber, protein and fat have been shown to be high (33-36%, 18-22%, and 6%,
respectively). Furthermore, the content of -glucan has been reported to be 2-3 times as
high as in other naked waxy barleys, varying from 15-18% of dry matter. This study
closely analyzed the association between structure and chemistry in the barley grain.
Through chemical isolation methods it was found that the cellulose and arabinoxylan
content was higher in the Prowashanupana variety of barley. It was hypothesized that the
Nutrient (%)Hulless
BarleyOats
Prowash
Barley
Protein 13 15 20
Fat 3 6 7
Starch 60 59 21-30
Total Dietary Fiber 13 10 30
-Glucan 5 5 15
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thicker cell wall indicates a high content of -glucan while a large amount of starch
granules is associated with higher starch content. Fluorescence microscopy was used to
study the structural characteristics of the grains and it was observed that the
Prowashonupana barley variety had irregular endosperm cells with thicker cell walls, and
thus the higher -glucan content is unique to the Prowashonupana variety of barley
(Andersson, Andersson et al. 1999). These studies comparing different varieties of
barley with the Prowashonupana (Sustagrain) barley variety show that there is a definite
advantage to use the latter in product formulations that are geared towards providing a
nutritional and functional advantage.
1.3 -Glucans and Arabinoxylans
Arabinoxylans and mixed linkage (13)(14)--D-glucans, commonly
referred to as beta-glucans, are the major non-starch polysaccharides present in various
tissues of barley. Depending on the genotypic or cellular origin, both polymers exhibit
variations in their molecular structures. The molecular features of -glucans and
arabinoxylans are important in determining their physical properties, such as water
solubility, viscosity, and gelation properties as well as of their physiological functions in
the gastro-intestinal tract, which most notably provides the health benefits mentioned
previously. The potential application of -glucans as food hydrocolloids has been also
proposed based on their rheological characteristics. In addition to enhancing solution
viscosity, -glucans have been shown to gel under certain conditions. Arabinoxylans
have been shown to significantly affect cereal based processes such as milling, brewing,
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and breadmaking. Furthermore, arabinoxylans offer nutritional benefits of soluble and
insoluble fiber, and because of the presence of phenolic moieties in their molecular
structures, they may also have some antioxidant properties (Izydorczyk and Dexter
2008).
-Glucan is a trivial name for the glucose polymer found in the endosperm cell
walls of barley and oats. The -bond is not digestible by enzymes in human
gastrointestinal tract, resulting in the classification of -glucan as a soluble dietary fiber
(Burkus and Temelli 2005). -glucans consist of linear unbranched polysaccharides of
linked -(1 3)- and -(1 4)-D-glucopyranose units in a non-repeating but non-random order, as seen below:
Figure 1: Molecular Structure of -(1 3)- and -(1 4)-glucan (Chaplin 2009)
-glucans form 'worm'-like cylindrical molecules containing up to about 250,000
glucose residues that may produce cross-links between regular areas containing
consecutive cellotriose units. They form thermoreversible infinite network gels. 90% of
the -(1 4)- links are in cellotriosyl and cellotetraosyl units joined by single -(1 3)-
links with no single -(1 4) or double -(1 3)-links. The main use of -glucans is in
texturizing by functioning as a fat substitute, which is made possible by the increase in
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viscosity. One such product, Nutrim, is prepared by subjecting an aqueous suspension of
barley flour to a high temperature mechanical shearing in the presence of thermostable -
amylase, followed by centrifugations and drying of the supernatant. In addition to -
glucans (515%, depending on the -glucan content in barley used for extraction), a
Nutrim preparation contains also starch, amylodextrin, and proteins and has been used to
make low fat cheddar cheese (Izydorczyk and Dexter 2008). In a study done using a -
glucan fat substitute product called Trimchoice, it was found that a 35% substitution with
fat resulted in shortbread cookies that were comparable in terms of texture, color, and
taste with the full-fat control (Sanchez, Klopfenstein et al. 1995). High molecular weight-glucans are viscous due to labile cooperative associations whereas lower molecular
weight -glucans can form soft gels as the chains are easier to rearrange to maximize
linkages. Barley -glucan is highly viscous and pseudoplastic, both properties decreasing
with increasing temperature. Although these properties cause difficulty in the brewing
industry by negatively affecting fermentation and filtration, -glucans have important
functionality in foods as well as physiologically (Chaplin 2009).
Arabinoxylans are non-starch polysaccharides found in the cell walls of plants.
They are generally classified as hemicelluloses, or more specifically pentosans, a series
of 5 carbon sugars. Their general structure is comprised of -(1,4) linked D-
xylopyranosyl backbone with -L-arabinofuranose units attached as side residues via -
(1,3) and/or -(1,2) linkages (Beaver 2008). They are present in Prowashonupana barley
at 12% dry weight basis (Andersson, Andersson et al. 1999)
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Figure 2: Structural elements present in arabinoxylans (Izydorczyk and Dexter 2008)
The arabinoxylan structure affects its physiochemical properties. Arabinoxylans
have the ability to bind water which may alter the dough rheology, processing and
finished product attributes of many baked products. The high water holding capacity of
arabinoxylans delays starch gelatinization most likely by restricting the amount of water
available for starch gelatinization. The arabinoxylans also protect the starch from -
amylase enzymatic degradation which results in increased bread volume, better crumb
elasticity and increased shelf life (Beaver 2008).
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1.4 Properties and Molecular Interactions among Major Food Components
Along with the many physiological benefits of barley -glucans, these compounds
exhibit certain rheological and physical properties in the food matrix that make it a
suitable for various food applications. Such beneficial health effects have been attributed
to the solubility of -glucans in water and their capacity to form highly viscous solutions.
Cereal -glucans exhibit considerable diversity in their structures, including the ratio of
tri- to tetramers, the amount of longer cellulosic oligomers and the ratio of -(1-4):-(1-3)
linkages. These structural features appear to be important determinants of their physicalproperties, such as water solubility, viscosity, and gelation. The potential use of -
glucans as hydrocolloids in the food industry is based mainly on their rheological
characteristics, i.e. their gelling capacity and ability to increase the viscosity of aqueous
solutions. Thus, -glucans can be utilized as thickening agents to modify the texture and
appearance of food formulations or may be used as fat mimetics in the development of
calorie-reduced foods. -Glucan-rich fractions from cereals or purified -glucans have in
fact been successfully incorporated into products such as breakfast cereals, pasta, noodles
and baked goods (bread, muffins), as well as dairy and meat products (Lazaridou and
Biliaderis 2007).
1.5 Beta-glucan extraction
Extraction of -glucans can be done to verify the amount present in the barley
varieties. Subsequently, the properties of -glucans alone can be studied to model how
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they behave when subjected to thermal, chemical, and physical changes. Extraction and
isolation of pure -glucans from oat and barley are conducted using the procedure
outlined in Figure 3. Pure -glucan has been added to several baked products with
successful applications (Thondre and Henry 2009). It is to be noted that this procedure is
widely accepted and used to confirm the amount of -glucans present in a commodity.
Figure 3: Extraction and purification of -glucans from barley and oats (Biliaderis and
Izydorczyk 2007).
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1.6 Water absorption capacity and effect on end-products
The addition of -glucans to wheat flour used for bread-baking barley has been
shown to result in a higher water absorption capacity. The addition of -glucans to a
dough formulation also increases the development time, the stability, the resistance to
deformation and the extensibility of poor breadmaking quality doughs, as well as the
specific volumes of the respective breads, exceeding even that of the good breadmaking
cultivar. Traditionally, barley has not been used in bakery products because it lacks
substantial gluten proteins and the end-products have poor sensory qualities (Bhatty,1999). Furthermore, studies showed that addition of fibrous materials to wheat flour
weakens the crumb cell structure, due to the dilution and weakening of the wheat gluten
protein network. Similarly, Dubois (1978) emphasized that especially utilization of the
water-insoluble fractions impair the gas retention of the dough and thereby change the
texture and appearance of the baked product. More recent studies have demonstrated that
-glucan-enriched barley fractions, blended with wheat flour, can produce bread with
acceptable sensory properties (Skendi, Biliaderis et al. 2010).
In a study done by Sharma and Gujral (2010), where several barley varieties were
used to determine differences in their water absorption, water solubility index, and oil
holding capacity, it was found that there was some difference among the different
varieties of barley. It was determined that the water solubility index ranged from 9.23%
to 11.77% in different cultivars. DWR-28 and RD-2552 varieties had highest and lowest
water solubility index respectively, however only DWR-28 showed significant difference
in water solubility index as compared to all other cultivars. The oil holding capacity
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significantly varied among the cultivars and ranged from 1.5 to 1.68 g/g, DWR-28 and
RD-2052 had highest and lowest oil holding capacity among the cultivars. Water
absorption capacity ranged from 1.38 to 1.63 g/g, the highest exhibited by PL-172 and
RD-2052 and lowest exhibited by RD- 2503. Bhatty (1993) reported similar value for
water holding capacity and oil absorption capacity for barley flour. The water absorption
capacity could be attributed to -glucan content in barley flour because there was positive
correlation (R = 0.843) between -glucan content and its water absorption capacity.
It is known that the flow behavior and gelling properties of -glucans can largely
vary with the concentration and the molecular size of the polysaccharide concentration.Thus, understanding the effects of barley -glucans with different molecular weights on
the rheological properties of wheat flour doughs with different breadmaking quality is
essential for determining both the dough handling properties during processing and the
quality of the end products. In a recent paper published by (Skendi, Papageorgiou et al.
2009), the effect of adding low (105Da) or high (2.03 x 105Da) molecular weight barley
-glucans in two wheat flours of different breadmaking quality were studied. Mechanical
spectra and creep-recovery analysis data within (low stress) and out (high stress) of the
linear viscoelastic region were obtained and revealed that the rheological behavior of -
glucan-enriched doughs depend on concentration and molecular weight of the
polysaccharide as well as on the flour type used. Addition of -glucan increased the G
values of the good breadmaking quality flour doughs, whereas decreased the G of the
poor quality wheat cultivar. Supplementation with -glucans increased the resistance to
deformation, flowability and elasticity of the doughs under low stress. Significant
correlations between frequency sweep and creeprecovery parameters of optimally
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developed doughs from both flours were found. The addition of -glucan in the dough
recipe of the poor breadmaking wheat flour may result in similar rheological responses to
those obtained from non-fortified good breadmaking quality wheat flour.
Many authors have reported that due to the -glucans ability to absorb high
quantities of water, doughs fortified with -glucans display a significant increase in the
farinograph water absorption values. It is generally recognized that water plays the most
important role on the viscoelastic properties of the dough during mixing; i.e. the
distribution of the dough materials, their hydration, and the gluten protein network
development strongly depend on the quantity of added water (Skendi, Papageorgiou et al.2010). Small deformation dynamic rheological tests and creep-recovery measurements
are often employed for dough characterization and the derived rheological data are
explored as predictors of breadmaking performance.
1.7 Rheological Properties Influenced by barley flour beta-glucan content
Rheology is concerned with how all materials respond to applied forces and
deformations. Basic concepts of stress (force per area) and strain (deformation per
length) are key to all rheological evaluations (Tabilo-Munizaga and Barbosa-Cnovas
2005). Shear-thinning behavior in foods may be conceptualized by the breakdown of
structural units in a food due to the hydrodynamic forces generated during shear. Most
non-Newtonian foods exhibit shear-thinning behavior, including many salad dressings
and some concentrated fruit juices. In fact, most foods fall into this non-Newtonian
category (Rao 1999). Beta-glucans are one such material that have been shown to exhibit
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such behavior and have demonstrated viscoelastic properties (Papageorgiou, Lakhdara et
al. 2005). Data reported on the consistency and viscoelastic properties of batter are
important in the development of new products (Kalinga and Mishra 2009).
Characterizing the mechanical behavior of food materials is complicated by the
fact that many food materials are viscoelastic, so their mechanical properties lie between
that of a purely elastic solid and that of a viscous liquid. Using oscillatory rheology, it is
possible to quantify both the viscous-like and the elastic-like properties of a material at
different time scales; it is thus a valuable tool for understanding the structural and
dynamic properties of food systems (Wyss, Larsen et al. 2007).
1.8 Stevia as a Sweetening Agent in Consumer Products
Stevia is a generic name for the sweetness-providing compounds, particularly the
steviol glycosides, extracted from the herb Stevia rebaudiana(Bertoni). It is generally
available as a mixture of steviol compounds, with the predominant sweetness compound
being Rebaudioside A (Carakostas, Curry et al. 2008). Stevia has negligible caloric value
for use in food products and beverages since it is used at a very low concentration. Stevia
leaf extracts exhibit a sweetening level of 15-30 times sweeter than sucrose, dependent on
the extract quality and raw material (SM Savita 2004). In 2008, stevia gained approval
for mainstream food usage from a dietary supplement status. Therefore, products
containing stevia launched thereafter, and have been gaining popularity among food
manufacturers because of its natural label and low-calorie benefits (Lord and Sant'Angelo
2010). Although stevia has been gaining acceptance and has increasing use in the food
industry in the past few years, there are technical issues with the product due to the
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presence of bitter compounds that are also incorporated into the sweetener during the
extraction process. There is also a lingering licorice aftertaste and sweetness at a higher
use concentration, which has been the cause for the limited acceptance of the product.
However, there are benefits of using stevia extracts, especially in baked products
where thermal processing occurs. Rebaudioside A has been shown to have thermal
stability in two specific studies. One was the use in pasteurized dairy product and the
other was in a laboratory baking study with temperatures up to 390 F. Due to its thermal
stability, stevia is suitable for baking applications. However, stevia is not the perfect
substitute for sugar in bakery applications. The sole function of stevia would be inproviding sweetness. Stevia lacks the ability to add texture, caramelize, feed the
fermentation of yeast or help tenderize a batter, all properties that sugar possesses. Also,
cakes made with stevia may not rise as well, and achieving a soft, chewy cookie may
require additional ingredients (Jones 2006).
Figure 4: Structural Components of Stevioside, Rebaudioside A, and Steviol
(Carakostas, Curry et al. 2008)
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1.9 Conclusions from Literature Review and Objectives for Research
Appealing to the heightened awareness of health issues such as childhood obesity,
prevalence of diabetes, and lack of fiber in the diet, more nutritious products need to be
made available to school children. As manufacturers make the changes to their products
to improve the nutritional value, the food quality should not diminish. Thus far, barley
flour has limited approaches in modern-day food products despite its known health
benefits. This may be attributed to the presence of a bitter taste and a strong whole-grain
character as well as the requirement of high sugar content in baked products to mask thistaste. However, the addition of sugar increases the caloric value of the product. To
address this issue, a natural sweetener called stevia will be studied by incorporating it
into a model baked product prepared with barley flour. The essential food quality
properties of color, taste, texture, and nutritional value will be used to assess the food
characterization of a barley flour containing product.
The specific objectives in this research include identifying key parameters
responsible for processing and to monitor the effect of water absorption with varying
levels of -glucans in barley flour, specifically noting how this difference affects some of
the rheological properties. Another aim is to reduce sugar levels in the product by
incorporating a natural sweetener called Stevia and to monitor its influence through
instrumental and sensory analysis. Finally, the instrumental findings of the research will
be compared with the sensory aspects of the model baked product to determine whether
there exists a detectable difference though a human response.
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CHAPTER TWO
Materials and Methods
A muffin type of baked product will be used as a model to assess the color,
texture, and sensory properties as an effect of the -glucan content and reduced sugar
levels on the final product. Most importantly, the interactions among the primary
components of the product need to be well-understood. Thus a model system of barley
flour, natural sweetener, water, and other minor components will be used to study the key
processing effects through instrumental and sensory analyses. The aim is to incorporate anatural sweetener while keeping the low-calorie and low glycemic index aim in focus. At
the same time, the functional changes occurring due to the reduction in sugar levels and
increased beta-glucan content will also be monitored.
Similarly, the type of fat used in the product formulation is intended to provide
some health benefit to the consumer in addition to its role in the baked product
formulation. Thus, flaxseed meal will be added to the product as it provides a source of
beneficial omega-3 fatty acids and adds fiber. In a study done by (Fiscus, Harris et al.
1999), it was found that flaxseed substituted into whole wheat flour at 25% and 50%
levels showed similar sensory results to the control which used 100% wheat flour in the
preparation of peanut butter cookies and banana bread. Important food quality
characteristics such as flavor, texture, and mouthfeel were found to have no significant
difference between that of the control and the formulation with the flaxseed added.
Minor ingredients such as flavorings and leavening agents will present in the final
product, but not studied in depth in the analytical parts of the project. The main objective
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is to determine and examine the behavioral differences among the different barley flours,
considering Sustagrain barley flour as the high -glucan and a commercially available
brand of barley flour as the low -glucan counterpart.
2.1 Ingredients Used in Baking Procedures and Analytical Measurements
Two varieties of barley flour will be used to study the functional changes caused
by the varying amounts of beta-glucan present in the two brands of barley flour. One is
barley flour manufactured by Bobs Red Mill, a commercially available brand, which willbe considered as the low beta-glucan barley flour. The other is Sustagrain, which as
previously mentioned, is a high beta-glucan (15%) containing barley flour sold under the
ConAgra Mills brand. The main objective is to identify the key behavioral differences
with other food components and compare how the beta-glucan levels affect the water
absorption capacity, rheological properties of the batter, textural properties in a model
baked product, and the final product color.
Ground flaxseed meal supplied by the company Bobs Red Mill will be used in
the muffin formulations to obtain color and textural measurements. The company
website states the following on the product page, In a 2 Tablespoon serving size (13
grams) the fiber content is 1.33 grams of Soluble Fiber and 2.67 grams of Insoluble Fiber.
Ground Flaxseeds are a good source of Omega 3 Fatty Acids. In a 2 Tablespoon serving,
there is 2400 mg of Omega 3 (2010).
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Figure 5: Nutrition Label for Bobs Red Mill Ground Flaxseed Meal (left) and Bobs Red
Mill barley flour
2.2 Water Absorption Index of Low and High -glucan Barley Flours
The amount of water used for a baked product has a great effect on the outcome
of the final volume and texture (Osorio, Gahona et al. 2003). Therefore, it is necessary to
determine how much water would be absorbed into the flour prior to developing product
formulations. The water absorption index can be determined by simple methods using
barley flour and water. Water absorption capacity of flour was measured by the ratios
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f
wf
mmmWAI
+=
and centrifugation methods (Sharma and Gujral 2010) (Ding, Ainsworth et al. 2006).
0.12 g Sustagrain barley flour and Bobs Red Mill Barley flour were dispersed in 1 mL of
distilled water and placed in pre-weighed centrifuge tubes. The dispersion was stirred
using a stir-plate for 10 min followed by centrifugation for 25 minutes at 3000 rpm. The
supernatant was drained off by allowing the tubes to stand inverted for 10 minutes. The
water absorption index was calculated by dividing the weight of the flour and water
mixture obtained after draining off the supernatant by the original weight of the flour.
The averages of triplicate measurements are recorded. It was predicted that the higher -
glucan Sustagrain flour will have a higher water absorption index since increasingamounts of -glucans have been shown to absorb more water (Sudha, Vetrimani et al.
2007).
Water absorption index was calculated by:
where mf= mass flour and mw= mass water.
Figure 6: Example of water separated from barley flour after centrifugation
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2.3 Microbakery Model Formulations for Barley Muffins
A dessert type baked muffin product was used as a model to characterize the
instrumental changes occurring in the system as a result of -glucan levels in the barley
flour as well as study the changes occurring due to the removal of sugar from the
formulation. Muffins were prepared using the following formulations, with process
variations occurring in the type of barley flour utilized (high or low -glucan) and the
reduction in sugar levels, while using stevia to maintain sweetness levels. The recipe
ingredients were adapted from (Idzorek 2010) and modified based on preliminary baking
experiments and the quantities were reformulated and adjusted to accommodate small-scale baking experiments. Ingredients such as eggs, banana, sugar, baking soda, vanilla
extract, and salt were sourced from local supermarkets. Banana puree was used since
fruit purees demonstrate humectant properties, promote tenderness and retain moistness,
increase shelf life, and can replace some of the sugar and/or fat in muffins and cakes (Hui
2006). The banana puree would also be helpful in providing some of the necessary
moisture to hydrate the barley flour in the formulation. Stevia leaves extract was
obtained from Spectrum Chemical.
Each set of muffins were prepared with the use of 1) Bobs Red Mill Barley
Flour as the low -glucan type or 2) Sustagrain Barley Flour as the high -glucan flour.
Each formulation was prepared with the same ingredients, with the process variation
occurring in the sugar:stevia use levels, as well as the addition of ground flaxseed meal in
the 0% sugar formulations. Stevia has been shown to have a potency level perceived as
200-300 times sweeter than sucrose (1.0). However, the sweetness potency, or the
sweetness perception, in a product is highly dependent on the sucrose equivalency level.
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The stevia to sugar equivalency use level has been reported as 4-8%, with 6% level being
a reasonable average value (Prakash, DuBois et al. 2008). Initially, stevia sweetener
levels in the product formulations were based on the previously mentioned levels. Thus,
the amount of sucrose (9.88 grams) used in the full sugar control product required 0.59
grams of stevia (6.0%) to have a similar sweetness equivalency.
Preliminary baking experiments were done to test this level of sweetness using
stevia in the formulation and it was found to be too high of a sweetness level, which also
resulted in a strong bitter aftertaste. Stevia use level was thus reduced to 0.15 grams in
the formulations, or approximately 0.24% of the total formulation. This stevia use levelwas employed for baking done for instrumental measurements as well as preparation of
samples used in sensory panels.
Table 3: Formulations for Muffin Batters Used to Prepare a Model Baked Product
Ingredient (g)100%
Sugar
0%
Sugar
0% Sugar +
Flaxseed Meal
Barley Flour 16.5 16.5 16.5
Salt 0.05 0.05 0.05
Baking Soda 0.44 0.44 0.44
Vegetable Oil 5 5 5
Water 105 F 10 10 10
Banana Puree 25 25 25
Eggs 5.5 5.5 5.5
Sugar 9.88 0 0
Vanilla 0.3 0.3 0.3
Flaxseed Meal 0 0 2.25
Stevia 0 0.15 0.15
Total 72.67 62.94 65.19
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Although the total weight of the batter formulations differs, the process control
was applied by weighing out muffin batters equally into mini-muffin tins. Equal amounts
of batter were utilized in all baking processes for instrumental experiments and sensory
analysis.
Procedure for preparing muffins:
A Frigidaire Gallery consumer electric convection oven was used for the baking
experiments. The oven was preheated to 325F and the temperature was maintained
throughout the preparation of the batter and baking process. A ripe banana was pureed in
a food processor (Hamilton Beach) until it reached a smooth consistency and did notcontain any visible chunks. In a mixing bowl, the dry ingredients consisting of barley
flour, salt, flaxseed meal and baking soda were combined and set aside. In another
separate mixing bowl, oil, eggs, vegetable oil, and sweeteners were mixed and beaten
with a hand-held electric mixer (Sears) on speed 3 until thoroughly blended, for
approximately 15 seconds. Then the banana puree, vanilla, water and dry ingredients
were added to the mixture and beat with the mixer on speed 2 for 15 additional seconds
until all ingredients are blended and uniform in appearance. The batter was then weighed
out to 12 1 grams in a paper muffin mold placed into a mini-muffin pan and baked for
ten minutes. The pan was then rotated 180 and baked an additional two minutes.
Muffins were then removed from the oven and allowed to cool in the pan at room
temperature for two minutes. Then, the muffins were transferred to a cooling rack for an
additional 30 minutes at room temperature. Muffins were stored in a sealed plastic zip-
top bag at room temperature (25C) for further analysis. Texture, color measurements,
and photographs of the surface and interior were obtained within 12 hours of preparation.
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2.4 Rise and Moisture Loss of Muffins
The variation for this experiment included the use of high and low -glucan
barley flours in the model baked product as well as the complete removal of sugar. When
sugar was omitted from the formulation, stevia was used to maintain sweetness levels.
The heights of the muffins were evaluated by obtaining the height of the batter prior to
baking and calculating the percentage of rise, or increase in height, after muffins were
prepared. A toothpick was inserted into the center of the batter and the toothpick was
marked at the level of the batter. The toothpick was then removed. The initial height of
the batter was recorded by measuring the distance between the mark made on the
toothpick to the end of the toothpick with a ruler, in centimeters. Final heights were
obtained in the same manner after allowing the muffins to be cooled for 30 minutes. The
percentage rise, or increase in muffin height, was calculated by:
% increase in muffin height = hf hix 100%,hi
where hfis the final height and hiis the initial height of the muffins.
The initial weight, 12 1 grams, of the muffin batter was recorded by placing the
batter in mini-muffin tin foil cups and weighing them on a scale. After baking, the
muffins were allowed to cool for 30 minutes and final weights were recorded. The
percentage change in weight, considered as moisture loss, was calculated by:
% decrease in muffin weight = mi mf x 100%,mi
where mfis the final mass and miis the initial mass of the muffins.
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Average values of four replicates are reported for both the muffin rise and moisture loss
measurements.
2.5 Rheological properties of barley dough using lubricating squeezing flow
technique
The rheological properties of a dough are a great indicator of their behavior
during baking and determining the final product texture, rise, spread, and overall quality.
Cookie spread rate is governed by dough viscosity as doughs with lower viscosity had a
higher spread rate compared to doughs with a higher viscosity (HadiNezhad and Butler
2009).
Traditional determinations of rheological properties of wheat flour dough have
been carried out using tests and instruments such as the farinograph and alveograph,
which provide important information on rheological characteristics for the development
of baking products. However, it has been seen that these tests do not allow detecting
differences of composition of the flour and addition of ingredients, nor do they provide
detailed information on physical and characteristic properties of flow behavior (Osorio,
Gahona et al. 2003). Thus, a technique called lubricated squeezing flow viscometry has
been used to quantify changes in the behavior of doughs and can be used with high
viscosity materials. This technique can detect differences among the samples that cannot
be observed under shear conditions. It also solves two major problems that occur in food
viscometry: 1) the slip condition in the surface and 2) the inadvertent rupture of the
structure of the sample when introducing it in the reduced space of the conventional
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rheometer. This technique has been previously applied to several high viscosity products
such as peanut butter, cheese, cooked cornmeal dough, mayonnaise, tomato paste, tortilla
dough, wheat dough, yogurt, dulce de leche (milk sweet), refried beans paste and
mustard. The lubricated squeezing flow viscometry technique is one of the basic types of
biaxial extensional flow, which is the type of flow behavior that occurs during the baking
process.
Both low and high -glucan barley dough were subjected to this type of
compression analysis to look at the flow properties of the doughs and how they affect the
final product texture. Dough samples were prepared using the previously determined
water absorption index values. Water was added to the barley flours and mixed
continuously for 3 minutes to allow the formation of a cohesive textured dough (Sudha,
Vetrimani et al. 2007). A TA.XT2 Texture Analyzer was used for the lubricated
squeezing flow technique. The TA-4, 38 mm cylinder probe was attached to a 25 kg load
cell. The platform as well as the surface of the probe were well lubricated with
commercially available food grade, edible vegetable oil to minimize any effects of
friction (Osorio, Gahona et al. 2003) and (Stojceska, Butler et al. 2007). Pre-test and
post-test speeds were set at 1.0 mm/sec and the test speed, or deformation rate, or
crosshead velocity, was set to 0.1 mm/sec. Dough discs measuring 1 cm in height and 2
cm radius were formed and placed on the platform. They were allowed to rest for 5
minutes prior to testing in order to stabilize internal tensions. The dough was compressedto 60% of its original height, or 6.0 mm. The force, time, and distance parameters were
recorded automatically through the Texture Expert software. Samples were prepared and
run in triplicates with average values used for calculations of biaxial stress, biaxial strain,
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and biaxial viscosities. Calculations to obtain biaxial viscosity vs. biaxial strain rate
curves were obtained following detailed methodology in (Osorio, Gahona et al. 2003).
Apparent biaxial extensional viscosity (ABEV) was calculated by the following formula:
ABEV = 2Ftht/R2v
where Ftis the compression force (N) at time of t; htis the height of the dough sample
(m) at time t; R is the initial radius (m) of the dough sample; v is the crosshead speed
(m/s). Data points were obtained at each second time interval and plotted to obtain a
curve of the biaxial extensional viscosity versus biaxial strain rate.
Figure 7: Apparatus and set-up of TA.XT2 Texture Analyzer for Lubricated Squeezing
Flow Technique Analysis of Doughs Prepared Using Barley Flours
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2.6 Pasting Properties of High -glucan and low -glucan barley flours
Rheological properties of starch pasting are traditionally studied by an instrument
called the Rapid Visco Analyzer. The working principle of this type of equipment is that
the rheology is directly related to the microstructure of starch and is influenced by many
factors such as the amylose/amylopectin ratio, the chain length of amylose and
amylopectin molecules, the concentration of starch, shear and strain, and temperature.
The sample is heated over a range of temperatures and the viscosity is recorded over a
period of time. Starch granules are generally insoluble in water below 50C, so the
viscosity of the starch mixture is low below this temperature. When the starch granules
are heated, the granules absorb a large amount of water and swell to many times of their
original size.
As the instrument generates shear conditions, the viscosity increases when the
swollen starch granules squeeze past each other. The temperature at which the rise in
viscosity is seen is known as the pasting temperature, which indicates the minimum
temperature required to cook a sample. As a sufficient amount of starch granules are
heated, there is period of time where there is a rapid increase in viscosity as the
temperature increases. The peak viscosity occurs at the equilibrium point where starch
granules are completely swollen and just as they begin the retrogradation process. The
peak viscosity and temperature indicates the water binding capacity of the starch. As thetemperature is held constant over a period of time, the starch granules begin to rupture
and polymer realignment occurs, which is evident by the decrease in apparent viscosity of
the paste and is known as the breakdown viscosity, which occurs at the beginning of the
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cooling phase. The viscosity at this stage of heating also gives an indication of paste
stability. As the sample is cooled down back to the starting temperature, re-association
between the starch molecules, especially amylose, occurs to varying degrees, which
results in an increase in viscosity once again as a gel begins to form. This phase of the
pasting curve is referred to as the setback region, and occurs due to the retrogradation of
the starch molecules. The final viscosity gives an indication of the stability of the cooled,
cooked paste under low shear conditions (Cui and Liu 2005) and (Brabender 2005).
Below is a typical pasting curve used to illustrate the specific points in the pasting profile
determined during the duration of the run.
Figure 8: Typical RVA pasting profile of a normal maize starch for viscosity ( - ) and
temperature (---) as a function of time (Cui and Liu 2005)
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The pasting properties of high and low -glucan barley flours were studied using
a rheometer and a controlled temperature circulating water bath to emulate the Rapid
Visco Analyzer instrument. A Brookfield Digital Rheometer Model DV-III was used in
conjunction with a with a K10 model water bath circulator system controlled by a
Thermo Scientific Haake DC30 temperature control system, with an accuracy of 0.1C.
The pasting properties of the low and high -glucan barley flours was studied, as well as
with the addition of sugar with the same ratio to that in the muffin formulation. The
sample was prepared as a 5% wt/wt basis of barley flour in water suspension. Sugar was
present in the muffin formulations at 13.6% of the total formulation, therefore of sugar
was added was added to the 5% barley flour and water suspension at the same ratio. All
samples were mixed prior to transferring into the rheometer holding cell and allowed to
equilibrate for 3 minutes to reach an initial temperature of 50C. The shear rate was set
to 200 rpm or 68 1/s for the duration of the run and an SC4-31 spindle was used based on
manufacturers given maximum viscosity parameters. The temperature profile was set to
begin at 50 C, then increase to 95 C, hold at 95 C for 5 minutes, and then cool to 50 C
(Stojceska, Butler et al. 2007; Sharma and Gujral 2010; Sharma, Gujral et al. 2010; Sai
Manohar, Urmila Devi et al. 2011). Time (min), temperature (C), and viscosity (mPas)
were recorded by the Rheocalc Version 3.2 software. Peak viscosity (mPa s), breakdown
viscosity (mPa s), final viscosity (mPa s), setback viscosity (mPa s), peak time (minutes),
and pasting temperature (C) were obtained from the graph plotted through the durationof the sample run. Averages of triplicate values are reported.
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2.7 Dynamic Rheological Properties of Muffin Batters
An oscillating rheometer was used to directly study the rheological properties of
batters to characterize the behavior of -glucan concentration on the rheological
properties of the batter and resulting changes occurring during processing.
Apparent Viscosity
Muffin batters were prepared according to the same formulations used in baking
experiments and were run through a Rheometric Scientific ARES Rheometer to measure
the viscosity between strain rate of 1 to 398 s-1. The sample was loaded between two
parallel plate geometry probes and the gap was adjusted to 1.0 mm. All measurements
were made at 25C using 25 mm diameter parallel plates. Stress and strain rates were
recorded and plotted to obtain a stress vs. strain rate curve to fit a Power-law model to
obtain the flow behavior index (K) and the consistency index (n) from the slope of the
line. The flow behavior was described by power law model, where shear stress (Pa) was
related to the shear rate (1/s) and the consistency coefficient (K in Pasn), and flow
behavior index (n) were obtained by linear regression.
Dynamic Oscillating Rheology
Oscillatory rheology is a standard experimental tool for studying behavior of
foods which exhibit viscoelastic properties, essentially those foods that are between
solids and liquids in their behavior (Wyss, Larsen et al. 2007). A Rheometric Scientific
ARES Rheometer was used to determine the oscillating rheology properties of the muffin
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batter. Initial experiments using barley flour solutions, based on approximate moisture
content in the muffin batter, were used to determine the frequency parameters at which
muffin batter samples would be tested. The frequency chosen for the duration of the
measurements was 20 s-1. The dynamic oscillatory-shear storage and loss moduli (G and
G) were measured and recorded as a function of % strain between 1 to 100%. All
measurements were made at 25C using 25 mm diameter parallel plate geometry with a
1.0 mm gap between the plates. Values reported are based on an average of 3 replicates.
2.8 Assessing Muffin Firmness Using a Texture Analyzer
As a measurement of food quality, texture is important for observing both
defective and acceptable food products. Texture can be defined as a group of physical
characteristics that arise from the structural elements of the food and are sensed primarily
by the feeling of touch, are related to the deformation, disintegration and flow of the food
when a force is applied (Taub and Singh 1998). A group of properties based on physical
structure, sense of touch, and functions of mass, distance, and time compose the
definition of texture (Bourne 2002). The classifications of this testing are puncture,
compression-extrusion, cutting-shear, compression, tensile, torsion, bending and
snapping and deformation. A comprehensive definition of food texture analysis and
methods for evaluation can be found at Bourne (2002), (Rosenthal 1999), and Texture
Technologies (2009).
The various methods for food texture analysis depend on the properties of the
food. A common texture instrument or universal testing machine measures force as a
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function of time and distance. A simple test of measuring the force to push a probe into a
food surface is used to measure texture known as a puncture test. The force to deform the
sample is similar to the way molar teeth bite and chew. However, the puncture test
assumes a semi-infinite geometry because of the small surface area measured. A
compression test will measure the larger surface area of the food sample by forcing it to
flow or fracture and deform dependent on its composition. This type of a compression
test is widely used in the industry as a measure of food quality during shelf-life studies
and to observe changes occurring due to ingredient modifications. When the direction of
the force applied to the sample is parallel to the direction it is sliding this is known asshear. A food product can also be measured for the force to be divided into two sections,
bent or pulled apart (Tabilo-Munizaga and Barbosa-Cnovas 2005). Using any test, the
most accurate data depends on a consistent sample temperature, size, shape, speed,
distance and direction.
Instrumental techniques do not completely indicate textural quality of a product
since they lack the uniqueness of consumers perception. A sensory texture analysis is
needed to measure the quality of a food dependent on its acceptability. However, human
experience of a trained expert can be compared to physical properties results for insight
on the reaction of texture differences. Using the human senses to manipulate the food
product by eating allows for many different variables to be identified. For example, in
study of apple firmness a difference of five Newtons using instrumentation is detectable
by human perception (Harker, Gunson et al. 2006). The process of eating can measure
the actions of biting, chewing, swallowing, etc. and determine which sensations are
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perceived at any given point. Since texture has a high affect on liking of the product, the
quality of a food can depend on the description of its meeting chosen standards.
Muffins that were prepared using the previously described formulations with low
and high -glucan flour with varying amounts of sugar:stevia ratios and the addition of
flaxseed meal were evaluated using the TA.XT2 Texture Analyzer. A compression test
was conducted on all the muffin varieties to determine the firmness and how it is affected
by each variation in the muffins and between the two types of flours. A TA-11, 1-inch
diameter cylinder was used with a pre-test, test, and post-test speed of 2.0 mm/sec.
Muffin samples placed on the testing platform and were compressed to 10 mm of theiroriginal height. An output of peak force (g) vs. time was obtained for each variety of
muffin in triplicate measurements, with average values reported (Texture Technologies,
Corp.). Differences between averages were determined by comparing muffin treatments
according to a t-test with a significance level of 5% (p = 0.05) using the Microsoft Excel
2003 Data Analysis ToolPak.
2.9 Evaluation of Colors Using a Colorimeter
Surface color is one of the important characteristics of baked products and is
considered as a critical index for judging baking quality. Baked products develop color
in the later stages of baking, simultaneously with crust formation and occur through
chemical processes including the Maillard reaction and sugar caramelization. The
Maillard reaction is responsible for color development at surface temperatures below
150C, while caramelization reactions occur when the product surface temperature
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exceeds 150C (Onishi M 2011). It will be important to monitor these color changes
differences that occur due to the removal of sugar from the product, which may affect the
caramelization reactions occurring at the higher temperature stage of the baking process.
A Minolta CM-2500d Spectrophotometer with Spectra Match software was
used to measure surface and interior color of the low and high -glucan barley flour
muffin varieties in L a*b* color space. The International Commission on Illumination
(CIE) (1976) color space measures L for the luminance or lightness component with a
range 0 to 100 (dark to light), and a* (from green to red) and b* (from blue to yellow).
After preparing muffin samples as described above, measurements were taken for surfacecolor on top of the muffin and the interior crumb surface color from muffins that were cut
longitudinally from top to bottom. Measurements were taken as an average of three
locations across the surface of the same muffin. Differences between average L, a*, and
b* values were determined by comparing muffin treatments according to a t-test with a
significance level of 5% (p = 0.05) using the Microsoft Excel 2003 Data Analysis
ToolPak. It was predicted that the omission of sugar from the formulation will have a
significant impact on the surface and interior crumb browning, thus resulting in color
differences. The generation of brown pigments during a caramelization and Maillard
browning reactions will be lacking when stevia is used in the muffin formulation.
The colors for the two barley flours were also obtained by taking three
measurements across different locations on a Petri dish containing the flours. Visual color
differences of the barley flours and muffin surface and interiors were observed and
recorded with digital photographs using a Sony DSC-H50 digital camera with automatic
camera shutter speed settings and compared with L a* b* color values obtained from the
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colorimeter to determine whether there were differences in the raw material and how they
would translate to changes occurring in the final product color.
2.10 Nutritional Comparison of Muffins
Nutritional values of barley muffin prototypes were evaluated using a software
called Recipe Calc, version 4.0 (Muller). Most ingredients nutrition facts were available
in the software database and were used as a basis for calculation of the finished product
nutrition facts. Ingredients that were not present in the database, such as specificproducts including the Sustagrain barley flour, Bobs Red Mill barley flour, and Bobs
Red Mill Flaxseed Meal, were added into the software using the nutrition label provided
on the package or supplied by the manufacturer. All ingredients were added and the
nutrition labels were prepared based on the quantities used in the product formulations
and calculated automatically in the software. According to the Food and Drug
Administration, it is best to determine the values for nutrition labeling by conducting
laboratory analyses on its products, but a manufacturer can use average values calculated
from ingredient composition databases as long as it is confident that the values are
accurate and accurately represent the characteristics of the product (Mermelstein 2009).
Although the generated nutrition facts may not be an adequate tool for in labeling for
manufactured products, they provide a clear method of comparison among the different
formulations and varieties of the muffins for research purposes, particularly to identify
changes in carbohydrate levels, to denote differences in sugar and fiber levels.
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2.11 Sensory Methodologies Used to Evaluate Muffin Products
Sensory evaluation is a scientific discipline used to evoke, measure, analyze, and
interpret reactions to those characteristics of foods and materials as they are perceived by
the senses of sight, smell, taste, touch, and hearing (Hui 2006). Sensory evaluation is a
technique that food scientists use the human body and its perception of the five basic
senses as a tool to measure differences and intensities of food characteristics. The
objective of the sensory panels pertaining to this research included looking at key
differences occurring due to the removal of sugar from the muffin formulations.
2.11.1 Quantitative Descriptive Analysis (QDA) Using Spectrum Method
Descriptive analysis methods involve the detection and the description of both the
qualitative and quantitative sensory aspects of a product by trained panels (Meilgaard,
Civille et al. 1999). Quantitative Descriptive Analysis (QDA) is the most sophisticated
sensory methodology. The results of QDA are a complete sensory description of the test
treatments (determined by the sensory panel), that provide a basis for relating specific
ingredients to specific changes in sensory characteristics of a product. QDA, particularly
the Spectrum Descriptive Analysis Method was chosen as the analysis tool for the study
since it yields quantitative data from panelist scores based on perceived intensities with
reference to pre-learned absolute intensity scales. The sensory findings may be u