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CHAPTER 15
Gluten-Free Bread:Sensory, Physicochemical,and Nutritional Aspects
Ioanna Mandala1, Maria Kapsokefalou21 Laboratory of Engineering, Processing and Preservation of Foods, Department of FoodScience and Technology, Agricultural University of Athens, Athens, Greece2Unit of Human Nutrition, Laboratory of Food Chemistry and Analysis, Department of FoodScience and Technology, Agricultural University of Athens, Athens, GreeceFl
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CHAPTER OUTLINE
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List of Abbreviations 161Introduction 161An Emerging Need for NewGluten-Free Products 162Ingredients for the Formulation ofGluten-Free Breads:Physiochemical and SensoryAspects 162
our and Breads and their Fortification in Health and Disease Prevention. DOI: 10.101
opyright � 2011 Elsevier Inc. All rights reserved.
Frozen Gluten-Free Breads 165Iron-Fortified Gluten-FreeBakery Products 165Technological Issues 168Summary Points 168References 168
LIST OF ABBREVIATIONSHPMC Hydroxypropyl methylcellulose
NaFeEDTA Sodium iron (III) ethylenediaminetetraacetate
INTRODUCTIONCeliac disease (gluten-sensitive enteropathy or gluten intolerance) is a genetically based
autoimmune enteropathy caused by a permanent sensitivity to gluten (Rubio-Tapia andMurray, 2010). In susceptible individuals, the ingestion of gluten induces an immunologically
toxic reaction that results in damage to the mucosal surface of the small intestinedspecificallysmall bowel mucosal villous atrophy with crypt hyperplasia (Catassi and Fasano, 2008).
Celiac disease affects approximately 1% of most populations but remains largely unrecognized
(Rubio-Tapia and Murray, 2010), despite advances in diagnosis. Upon diagnosis, the celiacdisease patient is directed to a gluten-free diet for life. The gluten-free diet excludes the intake
of storage proteins found in wheat, rye, barley, and hybrids of these grains, such as kamut and
triticale. This diet prevents morbidity and reduces the incidence of the associated gastro-intestinal malignancy, but it is difficult to adhere to (Kupper, 2005), particularly because it
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excludes many products that contain gluten. It is therefore to the benefit of celiac diseasepatients to develop new gluten-free products suitable to their needs that will increase their
dietary choices and improve quality of life in general.
AN EMERGING NEED FOR NEW GLUTEN-FREE PRODUCTSThe unequivocal need for the development of new gluten-free products is emerging for several
reasons. First, the daily dietary requirements for essential nutrients of celiac disease patients arenot fully covered by existing products. Products of the gluten-free group, compared with their
gluten-containing counterparts, are lower in protein, vitamins, minerals, and dietary fiber
(Anton and Artfield, 2007; Thompson, 2000). Moreover, gluten intolerance is frequentlyassociated with low absorption of nutrients. Consequently, celiac patients face several nutri-
tion-related problems, such as weight loss, iron deficiency anemia, osteoporosis, fatigue
syndrome, and diabetes. In addition to nutrient content, gluten-free products based on starchare less tasty than the gluten-containing counterparts. In the case of bread, there is also a high
staling tendency due to the absence of gluten (Gallagher et al., 2003).
Second, the target group of gluten-free products is currently expanding to include, in addition
to celiac patients, people looking for nonallergenic ingredients and generally people who are
more careful about their diet not just for health reasons. This constitutes a new market thatneeds a variety of products. According to research, 15e25% of parents in the United States seek
gluten-free products for their children as part of a balanced diet.
Third, gluten-free products can function as prototypes for the development of other productstargeted to specific groups with specific nutritional needs (e.g., diabetics).
Gluten-free products constitute a growing sector in the food business. Between January 2008and June 2009, Mintel’s Global New Products Database found gluten-free to be the 10th most
popular claim for new product launches throughout Europe.
INGREDIENTS FOR THE FORMULATION OF GLUTEN-FREE BREADS:PHYSIOCHEMICAL AND SENSORY ASPECTSMaize and rice are the main ingredients used for preparing gluten-free bakery products. Maizeand rice products are similar in taste, thus offering the consumer limited choice. Rice flour is
one of the most suitable cereal flours for preparing gluten-free products because it is natural,
hypoallergenic, and has a bland taste. It provides a high amount of digested carbohydrates buta low amount of proteins (prolamins), thus indicating the need for other components to
reinforce the batter matrix and the nutritional content of the final product.
There has been increasing interest in new gluten-free breads, whose formulations mainly involve
the incorporation of starches of different origin, other non-gluten proteins such as dairy proteins,
gums, and their combinations (Mariotti et al., 2009). These ingredients canmimic the viscoelasticproperties of gluten and result in improved structure, mouthfeel, acceptability, and shelf life of
these products (Gallagher et al., 2004). The successful production of gluten-free products is
a challenge, considering that gluten plays a major role in food structure and is involved in theformation of the three-dimensional network, which influences the textural and sensorial prop-
erties of the final product (Crowley et al., 2000). Furthermore, the development of new gluten-
free products is planned in order to reflect changing consumer lifestyles and needs.
Pseudocereals such as quinoa and amaranth can be used to enhance nutritional content,
particularly the protein content of the final product. Moreover, proteins from different sourcessuch as soybean, pea, egg albumen, and whey can be added to increase the nutritional value of
gluten-free products. By adding proteins, improvement in the quality of gluten-free bread due
to the formation of a continuous protein phase is also reported (Moore et al., 2004). It followsthat the selection of the proteins used in a gluten-free formulation is a critical issue.
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An example of the use of pseudocereals in gluten-free breads is the use of amaranth flour(Figure 15.1). Amaranth flour has high protein content, ranging from 14.5 to 17.8%. The
protein from amaranth flour is of high quality due to the high amounts of lysine- and sulfur-
containing amino acids (Gorinstein et al., 2002). In gluten-free products, amaranth flour canbe an alternative component for successful development of these complex mixtures. Tosi et al.
(1996) described the use of amaranth flour in gluten-free biscuits, whereas Schoenlechner et al.(2006) described a substitution of gluten-free flour by amaranth flour up to 100% for the
development of such products. Amaranth has been successfully used in gluten-free pasta
production (Chillo et al., 2007). Finally, gluten-free bread with enhanced nutritional value canbe produced using amaranth flour. In small amounts, amaranth flour can also improve dough
workability and volume of bread crumb. Furthermore, antifungal activity of amaranth has
been shown (Rizzello et al., 2009).
In a study on the sensory properties of gluten-free breads containing amaranth flour
(Schoenlechner et al., 2010), the addition of fat and albumen resulted in samples with higher
scores on mouthfeel, texture, and volume in comparison with samples without the addition offat or albumen. Samples were given to a trained panel (8 people at the University of Natural
Resources and Applied Life Sciences (BOKU), Vienna, Austria) and to an untrained panel
(52 people at the Agricultural University of Athens, Greece) to evaluate the sensory charac-teristics of the samples. According to both sensory evaluation protocols, the combined effect of
fat and albumen resulted in more desirable properties of the final products rather than the
effect of each ingredient separately. A 23 factorial screening experimental design was applied toinvestigate the influence of several variables on the quality of gluten-free bread that contained
amaranth. The variables were the amount of water (60, 70, and 80%), albumen (0, 2.5, and
5%), and fat (0, 2, and 4%). The effect of water and albumen content on response attributessuch as crumb firmness, crumb porosity, loaf circumference, and crumb relative elasticity are
shown in response surface plots (Figure 15.2). It was shown that water is a critical variable that
significantly influences the physical properties of the produced gluten-free breads. Increasedwater addition significantly decreased crumb firmness (Figure 15.2A) and slightly increased
relative elasticity (Figure 15.2B), which was accompanied by a significant increase in bread
circumference (Figure 15.2D). Moreover, it sharply increased the average pore size(Figure 15.2C). An increase in average pore size was accompanied by a decrease in pore
number. Variations in albumen concentration resulted in minor changes in the previouslymentioned response variables; average pore size and bread circumference were slightly
decreased. To a greater extent, albumen significantly influenced only crumb viscoelastic
character; relative elasticity was increased by the increased addition of albumen.
An alternative protein source for the development of gluten-free breads is carob seed. Carob
seed germ, in particular, has not been valorized as a functional protein source and has been
FIGURE 15.1Gluten-free breads containing amaranth. Freshly baked (left) and frozen bread stored for 10 days (right). Gluten-free breads have larger air cells than those of
wheat bread, but this structure is maintained during storage; thus, freezing can prolong their shelf life.
water
albumen
Cru
mb
re
la
tiv
e e
la
stic
ity
60 64 68 72 76 80 0 1 2 3 4 537
39
41
43
45
Estimated Response Surfacefat=2.0
Estimated Response Surfacefat=2.0
Estimated Response Surfacefat=2.0
60 64 68 72 76 80water
0 1 2 3 4 5
albumen
0306090
120150180
Cru
mb
firm
ne
ss
Estimated Response Surfacefat=2.0
water
albumenAve
ra
ge
p
ore
s
ize
60 64 68 72 76 80 0 1 2 3 4 51.21.6
22.42.83.2
water
albumen
Circ
um
fe
re
nc
e
60 64 68 72 76 80 0 1 2 3 4 512
13
14
15
16
A
C D
B
FIGURE 15.2The effect of water and albumen content in
amaranth-based gluten-free breads on the
response attributes crumb firmness (A), crumb
relative elasticity (B), crumb porosity (C), and
loaf circumference (D), shown in response
surface plots. The physical characteristics of
gluten-free breads were mainly influenced by
the initial dough water content. Specifically,
higher water addition decreased crumb
firmness and increased sharply the average air
cells size. Source: Reprinted with permission
from Schoenlechner, R., Mandala, I., Kiskini,
A., Kostaropoulos, A., and Berghofer, E.
(2010). Effect of water, albumen and fat on the
quality of gluten-free bread containing
amaranth. Int. J. Food Sci. Technol. 45,
661e669.
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neglected for many years by the food industry. However, the high protein content of the germ,
almost 50%, and its high content of lysine and arginine make carob germ fairly attractive forspecial dietary needs (i.e., clinical nutrition and gluten-free products) (Dakia et al., 2007).
Caroubin, the protein of carob germ, also has similar viscoelastic properties as gluten. Thus, its
potential as a food ingredient is high, and it could be considered a low-cost competitor toother food proteins such as dairy or soy proteins (Bengoechea et al., 2008).
Various sources of fiber are in use in gluten-free breads or being investigated for the devel-
opment of new gluten-free breads. For example, psyllium fiber was added to gluten-free breads(Mariotti et al., 2009), resulting in an increased fiber content of the bread (190e450% higher
than that of the control breads) and a softer crumb during a 4-day storage period. Furthermore,
it enhanced the physical properties of the produced dough due to the filmlike structure that itis able to form.
In one study, gluten-free bread enriched with resistant starch (20% substitution of the cornstarch used) raised the total dietary fiber content up to 89% compared to the control sample
(Korus et al., 2009). Furthermore, gluten-free breads contained more water than the control
and restricted bread staling. Compared to common sources of insoluble fibers, resistant starchmay have advantageous features that are both functional and nutritional. It is a natural white
source of dietary fiber, has a bland flavor, and gives a better appearance and texture and masks
flavor less than sources of insoluble fibers (Sajilata et al., 2006). Concerning its nutritionalcharacteristics, an interesting attribute of resistance starch is its pattern of fermentation in the
colon, principally the profile of short-chain fatty acids (Baixauli et al., 2008).
Few studies have investigated the effect of fibers that may have a prebiotic effect when added togluten-free products. Korus et al. (2009) added a range of different prebiotics to gluten-free
breads. Among them, inulin resulted in breads with high sensory scores and also reduced
staling. Inulin (8% inclusion level) increased fiber content from 1.4% (control) to 7.5%(control þ inulin) and crust color was enhanced (Gallagher et al., 2003). As inulin increases
the dietary fiber content of gluten-free bread, the nutritional value of the resulting product isincreased (Gallanger et al., 2004).
Gums are important ingredients in gluten-free bread formulations that may improve the
texture and the appearance of the final products. The addition of gums provides high doughconsistency, improves gas-retaining capacity, and results in products with a longer shelf life.
CHAPTER 15Gluten-Free Bread
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Different gums and different combinations may be applied in gluten-free product develop-ment. Among them, hydroxypropyl methylcellulose (HPMC), locust bean gum, guar gum,
carragenan, and xanthan gum provide the best results in the final products (Gallagher et al.,
2004; Lazaridou et al., 2007). Gum combinations such as xanthanelocust bean gum areeffective in improving dough structure (Demirkesen et al., 2010).
Complex formulations that appear promising in terms of technological improvement andnutritional quality can be developed. Clearly, new products differ in their degree of innovation
and, consequently, the effort invested in their development. Gluten-free products can be clas-
sified into the following categories: (1) reformulations (e.g., high-fiber gluten-free versions oftraditional antecedents), (2) new forms of existing products (e.g., frozen and par-baked), (3)
repackaging of existing products, and (4) innovative products (e.g., use of novel cereals) that are
technologically challenging and require good marketing (Kelly et al., 2008). Furthermore,ingredients for a new food product can be based on different criteria, such as function in the
product, cost, or availability. In the case of gluten-free products, labeling concerns are a key
issue; for example, a product that is labeled as causing an allergic reaction in consumers withceliac disease is to be avoided. The staling process is important in gluten-free products because
they contain a large amount of starch and its retrogradation influences the quality of the final
product. Hence, a reduced staling rate in gluten-free products is quite desirable. Water migrationand transformation in the starch fraction are important factors that can control staling.
FROZEN GLUTEN-FREE BREADSFrozen storage can be used for the production of gluten-free products with extended shelf life.
Par-baking bread production has great market potential in gluten-free cereal processingbecause a fresh product can be produced with a simple bake-off stage (Kelly et al., 2008). Most
of the gluten-free bread and rolls available on the market are par-baked, but there are no
publications in this area (Keller et al., 2008). Figure 15.1 shows gluten-free bread frozen stored.As expected, the structure of such products is different from that of a wheat bread. Pore size
and number differ; usually, the produced sample has larger pores and a lower volume than
wheat bread. Frozen storage can be successfully used for the production of gluten-free breads.The sensory characteristics of wheat breads containing gluten and gluten-free breads preserved
by using either microwave treatment or frozen storage are presented in Figure 15.3 (Liassi and
Mandala, 2007). According to the sensory characteristics presented, wheat breads seemed to befirmer, with lower deformability, and less crispy than gluten-free breads. On the other hand,
gluten-free breads were more adhesive and had greater chewiness. Frozen stored breads (wheat
breads and gluten-free breads) had the best appearance, aroma, taste, and textural character-istics. In addition, sensory attributes in ambient conditions and after microwave treatment had
only slight differences.
IRON-FORTIFIED GLUTEN-FREE BAKERY PRODUCTSThe immunologically toxic reaction that is induced by gluten in susceptible individuals results
in damage to the mucosal surface of the small intestine (Rubio-Tapia and Murray, 2010). Thisinterferes with the absorption of nutrients, including iron. Thus, the importance of celiac
disease as a possible cause of iron deficiency anemia is increasingly being recognized. It is
estimated that celiac disease may account for 3e5% of the prevalence of iron deficiencyanemia (Grisolano et al., 2004). Moreover, the gluten-free products are often low in micro-
nutrients, increasing the risk of deficiencies (Thompson, 2000). Fortified or enriched gluten-
free products are rare, but it has been suggested that the development of such products wouldimprove the quality of the diet (Kupper, 2005). Fortification is an effective approach to
increase dietary iron intake, provided that certain conditions apply (Hurrell et al., 2004).
Successful fortification requires an iron compound that is adequately absorbed and does not
affect the sensory properties of the products. Iron has been known to affect the sensory
0
2
4
6
8
Crumb color
Crust color
Intensity
Muddy
Yeasty
SweetSalty
Hardness
Fracturability
Adhesiveness
Chewiness
AC 1
MW 1
MW 3
F
0
2
4
6
8
Pore size
Crumb color
Crust color
Soily
Bitterness
SourHardness
Fracturability
Adhesiveness
Chewiness
Crispiness
AC 1MW 1MW 3 F
A
B
FIGURE 15.3Sensory characteristics regarding the
appearance, aroma, taste, and texture of
(A) control gluten-containing breads and
(B) gluten-free breads stored in ambient
conditions (AC), after microwave
treatment (first and third day of storage;
MW1 and MW3, respectively), and after
frozen storage (F). The sensory
characteristics of the breads presented
(wheat or gluten-free) were negatively
influenced by microwave treatment or by
storage in ambient conditions. On the
contrary, frozen stored breads had good
appearance, aroma, taste, and texture.
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properties of a fortified food, particularly color and taste (Hurrell et al., 2004). Ferrous sulfateis the most popular source of iron for the fortification of various foods; however, other iron
forms may exhibit higher bioavailability than ferrous sulfate and may present alternative
choices (Lynch and Stoltzfus, 2003). Other iron compounds, such as iron gluconate or sodiumiron (III) ethylenediaminetetraacetate (NaFeEDTA) (Hurrell et al., 2004), have been studied
as well.
The fortification of gluten-free breads, however, presents further challenges. In general, the
taste of gluten-free bread is inferior to that of white wheat bread; therefore, the moderate scores
obtained were typical for gluten-free bread and were considered acceptable for such products.In one study (Kiskini et al., 2007), we produced gluten-free bread, fortified with iron, using
selected iron compounds (iron pyrophosphate, iron pyrophosphate with emulsifiers,
NaFeEDTA, electrolytic iron, ferrous gluconate, ferrous lactate and ferrous sulfate). Further-more, we tested the sensory characteristics of the iron-fortified product (mouthfeel texture,
crumb color, aroma, and taste) and compared iron dialyzability of various iron compounds.
We found that the most acceptable products were those fortified with ferrous pyrophosphatewith emulsifiers and ferrous pyrophosphate. Ferrous dialyzable iron (ferrous iron with
a molecular weight less than 8000, an index for prediction of iron bioavailability) was
measured under simulated gastrointestinal conditions. Ferrous dialyzable iron in gluten-freebread fortified with iron pyrophosphate with emulsifiers, NaFeEDTA, ferrous bis-glycinate,
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ferrous gluconate, or ferrous sulfate was higher than that in gluten-free bread fortified withelectrolytic iron, ferrous lactate, or iron pyrophosphate. When comparing iron-fortified wheat
or gluten-free breads (Kiskini et al., 2010), we observed that the effect of iron on the quality
characteristics of the breads investigated depended on iron type but not on iron solubility.Color, crust firmness, specific volume, cell number and uniformity, as well as aroma, were the
attributes that were mainly affected in iron-enriched wheat bread (Figure 15.4). According toprincipal component (PC) analysis, the total variation in all data was explained up to 96.18%
by PC1 (50.06%) and PC2 (46.12%). Component 1 was defined by the L/b value and the crust
firmness. Component 2 was defined by the specific volume, the firmness, the viscoelasticity,and the moisture content of the crumb (see Figure 15.4).
In gluten-free breads, differences between unfortified and fortified samples included color,
crust firmness, cell number, moisture odor, metallic taste, and stickiness. In some cases, thesensory scores were better for fortified samples. In general, we observed that differences in the
sensory characteristics of breads due to iron fortification were less pronounced in gluten-free
compared to wheat breads (Kiskini et al., 2010).
A frozen iron-fortified gluten-free bread was developed to meet the market request for frozen
breads. In these frozen formulations, the iron compound remained in the aqueous environmentof the dough for a longer storage time than it would have in a fresh white wheat bread product,
thus interacting with the remaining ingredients and creating a challenge for maintaining its
sensory characteristics. In this experiment (Kiskini et al., 2007), the fortified products in the formof dough remained at �18�C for 10 days before they were baked and tested. Differences in
reactivity of the iron compounds in the physicochemical environment of the dough or of the
baked bread may explain the observed differences in scores assigned to the different formula-tions. However, it was difficult to explain why some iron-fortified samples were assigned better
scores than gluten-free breads. In the case of iron pyrophosphate with emulsifiers, the scores
were significantly higher than those of gluten-free breads in most attributes tested. This suggests
FIGURE 15.4Physical attributes and sample categorization in a biplot of two principal components. Numbers in bread samples correspond to
iron-type fortificants: CB1/GFB1, unfortified; CB2/GFB2, ferric pyrophosphate; CB3/GFB3, ferric pyrophosphate with
emulsifiers; CB4/GFB4, sodium iron EDTA; CB5/GFB5, ferrous sulfate; CB6/GFB6, elemental iron. Differences in the physical
characteristics of breads due to iron fortification were less pronounced in gluten-free compared to wheat breads. The unfortified
wheat bread was significantly different from all other samples. The ferric pyrophosphate-fortified bread (CB2/GFB2)
declined the most from the standard unfortified sample. Source: Reprinted with permission from Kiskini, A., Kapsokefalou, M.,
Yanniotis, S., and Mandala, I. (2010). Effect of different iron compounds on wheat and gluten-free breads. J. Sci. Food Agric.
90, 1136e1145.
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that iron fortification by this compound improves some sensory characteristics of gluten-freebreads. A plausible explanation may be that the emulsifier used in this formula led to a good
moisture distribution in the crumb and a desirable aerated structure. It was observed that the
crumb of this product had medium-sized air pores of good uniformity. Furthermore, its graincharacteristics (pore size and distribution) had the greatest similarities to those of the unfortified
sample. These observations suggest that further investigation of the physicochemical charac-teristics of the iron-fortified gluten-free breads is needed because it may reveal important effects
of iron compounds on the properties of the baked products. Furthermore, it may explain
differences noted by the trained panelists. Nevertheless, these results are promising for thedevelopment of iron-fortified gluten-free baked products. Identification of the appropriate iron
compound that will not cause adverse quality changes is still a challenge.
TECHNOLOGICAL ISSUESInnovative products that are technologically challenging require the development of complex
formulations that provide consumers superior quality products. Ingredients for the develop-ment of a new gluten-free bread type should be carefully chosen, and their selection should be
based on their high added value. Furthermore, they should meet the criteria of allergy
concerns, and any suspicious allergic substance is strictly inappropriate for celiacs and shouldbe avoided.
New products differ in their degree of innovation and consequently the effort invested in their
development, but high-quality products with good market prospects should be based ona great degree of innovation. Thus, innovative gluten-free products should be carefully
designed and further developed in order to fulfill consumers’ needs.
SUMMARY POINTSl Celiac disease is caused by a permanent sensitivity to gluten.
l The celiac disease patient is directed, for life, to a gluten-free diet.l The gluten-free diet excludes the intake of storage proteins found in wheat, rye, barley, and
hybrids of these grains, such as kamut and triticale.
l New gluten-free products will increase the dietary choices of celiac patients or othernutritionally conscious consumers and improve their quality of life.
l Gluten-free ingredients employed in the formulation of gluten-free breads include maize;
rice; amaranth; quinoa; starches of different origin; non-gluten proteins such as dairyproteins, gums, hydrocolloids, and their combinations; inulin; psullium; and gums
(HPMC, locust bean gum, guar gum, carragenan, and xanthan gum).l Fortified gluten-free breads, particularly those fortified with iron, meet the increased
nutrient needs of celiac patients.
l Achieving desirable physicochemical and sensory characteristics for the gluten-free breadsremains a challenge that drives continuous research in the field.
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