Influence of hydrocolloids on dough handling and technological properties of gluten-free breads

Accepted Manuscript Influence of hydrocolloids on dough handling and technological properties of glutenfree breads Shabir Ahmad Mir, Manzoor Ahmad Shah, Haroon Rashid Naik, Imtiyaz Ahmad Zargar PII:

S0924-2244(16)30020-6

DOI:

10.1016/j.tifs.2016.03.005

Reference:

TIFS 1781

To appear in:

Trends in Food Science & Technology

Received Date: 22 January 2016 Revised Date:

25 February 2016

Accepted Date: 15 March 2016

Please cite this article as: Mir, S.A., Shah, M.A., Naik, H.R., Zargar, I.A., Influence of hydrocolloids on dough handling and technological properties of gluten-free breads, Trends in Food Science & Technology (2016), doi: 10.1016/j.tifs.2016.03.005. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Influence of hydrocolloids on dough handling and technological properties of gluten-

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free breads

Shabir Ahmad Mirab, Manzoor Ahmad Shahb*, Haroon Rashid Naikc, Imtiyaz Ahmad

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Department of Food Technology, Islamic University of Science and Technology,

b

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Awantipora, Jammu and Kashmir, 192122, India

Department of Food Science and Technology, Pondicherry University, Puducherry, 605014,

India c

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Zargarc

Division of Post Harvest Technology, Sher-e-Kashmir University of Agricultural Sciences

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and Technology of Kashmir, Jammu and Kashmir, 190025, India

*Corresponding author:

India

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Department of Food Science and Technology, Pondicherry University, Puducherry, 605014,

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Email: [email protected]

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Abstract Background The development of gluten-free breads has attracted great attention as a result of better

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diagnoses of relationship between gluten-free products and health. The market demand for gluten-free products is increasing day by day due to growing number of celiac disease cases. Development of gluten-free bread remains a technological challenge due to the key role of

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gluten in the breadmaking process and in bread structure, appearance, texture and shelf life. Scope and Approach

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This review covers recent advances in the application of hydrocolloids in dough handling, technological and nutritional properties of gluten-free breads, which affect its quality and value. Key Findings and Conclusions

Gluten-free breads results from the combination of different ingredients and hydrocolloids

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required to building up network structures responsible for bread quality. Various gluten-free formulations have applied hydrocolloids to mimic the viscoelastic properties of gluten. In addition, the impact of different hydrocolloids on the characteristics of dough and bread

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quality is known to be highly dependent on raw materials, the nature and quantity of hydrocolloids. Hydrocolloids improve the texture, increase the moisture content and extend

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the overall quality of bread. The results of the reviewed studies indicate that some of those products were acceptable and presented similar or better sensory attributes than control formulations and some were even comparable to their wheat-based counterparts. Based on successful applications of hydrocolloids, it is suggested that novel nutritious ingredients, combined with hydrocolloids can be added to gluten-free bread formulations to improve the quality of life.

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Keywords: Gluten-free bread; hydrocolloids; dough handling; bread structure; technological properties

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1. Introduction The demand of gluten-free products, especially bread is increasing as a result of the increase of celiac disease diagnosis (Cureton & Fasano, 2009). Market trends and the

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increasing diagnoses of celiac disease have encouraged extensive research for the development of gluten-free breads (Houben et al., 2012). Nevertheless, production of high

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quality gluten-free bread is a big challenge due to the absence of gluten, which confers unique viscoelastic properties to dough. Generally, bread development without gluten has involved the use of diverse ingredients and additives with the purpose of imitating the viscoelastic properties of the gluten and consequently to obtain quality bread products (Sciarini et al., 2010; Hager & Arendt, 2013; Demirkesen et al., 2014).

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To overcome this challenge, gluten-free bread formulations involving diverse approaches, such as the use of different gluten-free flours (rice, maize, sorghum) (Schober et al., 2005; Sciarini et al., 2010; Mancebo et al., 2015), pseudocereals (quinoa, amaranth,

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buckwheat) (Hager & Arendt, 2013; Mariotti et al., 2013), legume flours (soya, chickpea, pea) (Aguilar et al., 2015), starches (corn, potato, cassava) (Lazaridou et al., 2007; Mahmoud

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et al., 2013), and ingredients such as hydrocolloids, emulsifiers and shortenings or combinations thereof as alternatives to gluten, to improve their technological, sensory and nutritional properties, and also the shelf-life which leads to an increased final price (Demirkesen et al., 2014; Ronda et al., 2015). Several additives are used to provide the dough properties and technology properties of bread (Demirkesen et al., 2013; Capriles & Areas, 2014). Among the additives, hydrocolloids are one of the commonly used to achieve this target (Houben et al., 2012;

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Matos & Rosell, 2015). Therefore, the applications of hydrocolloids or gums in gluten-free bread formulations are a promising alternative for the expansion of high-quality breads for a targeted consumer. Hydrocolloids consists a number of water soluble polysaccharides with

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varied chemical structures providing a wide range of functional properties that make them suitable for different applications in bread industry (Lie & Nie, 2015). The hydrocolloids improve dough development and gas retention through an increase in viscosity, producing

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gluten-free breads with higher baking and quality properties (Capriles & Areas, 2014).

Investigations on gluten-free products, especially bread, have focussed on improving

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technological parameters including volume and crumb hardness in addition to sensorial perception (Houben et al., 2012; Kittisuban et al., 2014). Several hydrocolloids have shown the acceptable quality gluten-free breads (Table 1). In addition being applied as gluten substitutes in gluten-free breads, hydrocolloids have been used to improve texture, to increase the moisture retention, and to enhance the overall quality properties of the bread (Rojas et al.,

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1999).

There are numerous research papers and academic reviews which have focussed on the effect of additives on gluten-free bread. However, to the best of our knowledge, there is

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no such review focussing specifically on the influence of hydrocolloids on properties of gluten-free breads, which is a commonly used additive in the bread industry. Thus, the

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objective of this paper is to review the latest findings on the effect of hydrocolloids on glutenfree bread formulas, with particular emphasis on dough handling, technological and nutritional properties.

2. Why need gluten-free breads? Celiac disease is one of the most common lifelong disorders on a worldwide basis. It is an immune-mediated enteropathy triggered by the ingestion of gluten in genetically susceptible individuals and is characterized by a strong immune response to certain amino

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acid sequences found in the prolamin fractions of wheat, barley and rye (Hill et al., 2005; Rosell et al., 2014). This disorder damages the villi, tiny hair like projections in the small intestine that absorb nutrients due to an immunological reaction to gluten resulting in damage

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to the mucosa and generalized malabsorption of nutrients (Cureton & Fasano, 2009). At present, the only effective treatment for celiac disease is strict adherence to a gluten-free diet, through permanent withdrawal of gluten from daily food. In addition to

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patients with celiac disease, many individuals cannot tolerate gluten proteins due to Ig-E mediated allergic reactions and they too must avoid gluten containing foods (Matos & Rosell,

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2015).

Bread is mostly consumed as major dietary source of calories (Phimolsiripol et al., 2012; Mir et al., 2014; Ho et al., 2015). Increasing numbers of diagnosed cases and growing awareness makes the availability of gluten-free breads an important socioeconomic and health issue. The production of high quality gluten-free bread made from ingredients other

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than wheat flour represents a major technological challenge. So it is necessary to develop the gluten-free breads with consumer acceptability. 3. Hydrocolloid functionality

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Gluten is the main structure forming protein present in wheat, barley and rye. Gluten is responsible for the viscoelastic properties of dough which is compulsory to retain gas

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produced from yeast fermentation and oven rise during the production of bread (Houben et al., 2012). The replacement of gluten is a major challenge for food technologist to produce the breads with desirable quality and technological properties. Hydrocolloids are one group of additives which fulfil this need. Hydrocolloids are

used in gluten-free breads to improve dough handling properties and to enhance the quality and shelf-life of bread. They are capable of controlling the rheology and texture of aqueous systems throughout the stabilization of emulsions, foams and suspensions (Li & Nie, 2015).

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Hydrocolloids are water-soluble polysaccharides with diverse chemical structures depend on the type and provide a broad range of techno-functional properties, which make them extensively use in the food industry. They are used as structuring agents to mimic the

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viscoelastic properties of gluten. With the same aim of reinforcing dough structure, proteins have been added to gluten-free recipes, and cross-linking enzymes help to create a protein network.

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The gluten-free bread quality is mainly influenced by the nature, content and properties of hydrocolloids, which increase dough foam stability by increasing viscosity,

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flocculation and coalescence, preventing effects on the dough aqueous phase and thus on the stability of the liquid film surrounding gas bubbles (Dickinson, 2010). Generally neutral hydrocolloids are less soluble whereas polyelectrolytes are more soluble, but the hydration kinetics depends on many factors. Carboxymethylcellulose (CMC), guar and xanthan are soluble in cold water; however, carrageenan, locust bean gum and many alginates require hot

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water for efficient hydration. The water held specifically through hydrogen bonding or structuring of water and also by inter-molecular and intra-molecular voids. All hydrocolloids interact with water, reducing its diffusion and stabilizing its presence. The interactions

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between hydrocolloids and water depend on hydrogen bonding and therefore on temperature and pressure in the same way as water cluster formation (Anton & Artfield, 2008; Capriles &

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Areas, 2014).

Hydrocolloids exhibit a wide range of conformations in solution as the links along the

polymeric chains can rotate relatively freely within valleys in the potential energy landscapes. Conformationally stiff hydrocolloids present essentially static surfaces encouraging extensive structuring in the surrounding water. Water binding properties affects the texture properties, prevents syneresis and may have substantial economical benefit. The hydrocolloids tie up water and increasing the plasticizing of food components. They can also affect ice crystal

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formation and growth, thus influencing the texture of frozen breads. Some hydrocolloids, such as locust bean gum and xanthan gum, may form stronger gels following a freeze thaw cycle due to kinetically irreversible changes resulting from forced association as water is

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removed during freezing (Giannouli & Morris, 2003). The effect of hydrocolloids varies according to the other ingredients used during the production of gluten-free bread. The magnitude of hydrocolloid effect on dough and bread

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properties is dependent on chemical structure, amount used, interactions with other ingredients and the parameters of the process (Houben et al., 2012; Hager & Arendt, 2013).

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Hydrocolloids provide the desired results to some extent, but among the various hydrocolloids, hydroxypropylmethylcellulose (HPMC) and xanthan gum are mostly commonly used in gluten-free breads due to their promising effects on the quality of the final product (Hager & Arendt, 2013; Mancebo et al., 2015). 4. Dough handling properties

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Dough properties of gluten-free breads have been determined (Table 2). The dough suitable for production of bread needs to have a property that enables it to stretch in response to the expansion of leavening gas. Dough films which surrounding the gas bubbles must have

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sufficient strength to prevent collapse and the same time are capable of stretching without rupturing (Singh & MacRitchie, 2001). Dough properties are measured using numerous

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rheological techniques. The most often used instruments are the farinograph, mixograph, extensograph and alveograph (Mancebo et al., 2015). The Brabender farinograph is designed to record changes of dough consistency during kneading under standard conditions, i.e. throughout dynamic deformations. The Brabender extensograph records the dough resistance to stretching and the distance the dough stretches before it ruptures. The Kieffer dough and gluten extensibility rig is commonly method used to evaluate dough quality, especially

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extensibility (Kieffer et al., 1998). These instrumental properties of dough quality correlate with final product quality. The rheological characterisation of gluten-free doughs is usually related to quality

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indicators of end-products and provides important information for food technologists, allowing the appropriate selection of ingredients to optimise the final product (Lazaridou & Biliaderis, 2009). The mechanical properties of gluten-free doughs measured by fundamental

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rheological methods including oscillatory tests, such as strain and frequency sweeps, as well as creep-recovery tests on gluten-free dough formulations (Lazaridou & Biliaderis, 2009;

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Moreira et al., 2011). Oscillatory shear measurements are widely used to simultaneously evaluate the viscoelastic properties, i.e. elastic (G') and viscous (G") moduli (Sivaramakrishnan et al., 2004; Lazaridou et al., 2007). Creep-recovery tests are useful to establish links with results from empirical techniques. This test consists of the application of a constant stress; when the stress is released, some recovery is observed as the material

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attempts to return to its original shape.

Gluten-free dough making process differs from that used for making gluten containing, generally due to the restrictions associated with the amount of water, which is

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responsible for dough consistency during mixing operation (Macro & Rosell, 2008), but also affects dough handling and baking properties (Gomez et al., 2013). Gluten-free breads are

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mainly starchy material where the gelatinisation of the starch has significant effect on the quality of bread. Starch gelatinisation takes place efficiently when water is present in sufficient quantity, because very often gluten-free doughs show more resemblance to batters. Moreover, when gelatinised starch is present at the initial stages of bread-making, it can significantly contribute to dough consistency (Sciarini et al., 2010). Hydrocolloids dramatically affect the flow behaviour of dough even though present at low concentrations. They are used to enhance viscosity, which leads to stabilization of

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ingredients by preventing settling, phase separation, foam collapse and crystallization. The viscosity property usually changes with concentration, temperature and shear strain rate in a complex manner dependent on the specific hydrocolloid and the presence of other ingredients

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used for bread making (Marcotte et al., 2001; Moreira et al., 2013). The viscoelasticity of rice-based dough showed great dependence on frequency, due to the lack of a strong elastic structure. Hydrocolloids increased the dependence of

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viscoelastic moduli and the viscoelasticity on frequency (Gujral et al., 2003). Demirkesen et al. (2010) observed that the blend of xanthan-guar gum produced the highest increase in

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viscoelastic moduli, and the lowest hardness in gluten-free bread. Sciarini et al. (2012a) reported a significant increase of the storage modulus with the addition of 0.5% carrageenan, which led to the highest increase in specific bread volume.

The consistency of rice dough increased during mixing, heating and cooling by the addition of HPMC as reported by Marco and Rosell (2008). Matos et al. (2013) evaluated the

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rice flour based gluten-free formulations containing potato or corn starch and hydrocolloids (HPMC, xanthan gum, or pectin). Dough Mixolab® parameters showed significant correlation coefficients with physical properties of bread, and moderate correlation

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coefficients with sensory characteristics. The thermal properties of a bread dough through differential scanning calorimetry consisting of a blend of corn and cassava starches with

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HPMC as a gluten mimic was studied by Kobylanski et al. (2004). The HPMC greatly influenced the transition temperatures of the dough. The results showed that onset temperature of starch gelatinization was dependent on the interactions between HPMC and water.

Cato et al. (2004) reported that the combination of CMC and HPMC showed the best in regards to dough viscoelastic properties. The dough is able to trap fermented gases and to develop a porous cell structure as well as good loaf volume. The positive effects of HPMC on

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rheological properties of rice dough have indicated favourable perspectives for the glutenfree bread industries (Sivaramakrishnan et al., 2004). Rheological measurements from oscillation tests and creep tests showed that rice dough with 1.5% and 3.0% HPMC had

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similar rheological properties to that of wheat flour dough. Shittu et al. (2009) reported that inclusion of xanthan gum had significant effects on the tenacity and extensibility on the composite flour-based dough.

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Lazaridou et al. (2007) investigated the effect of hydrocolloids on dough rheology in gluten-free formulations based on rice flour, corn starch and sodium caseinate (control).

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When pectin, CMC, agarose and xanthan were added to the formulation, the rheological behaviour of the doughs showed that xanthan gum had the most pronounced effect on viscoelastic properties, yielding strengthened doughs. Rheological properties of dough by oscillatory and creep measurements showed that the elasticity and resistance to deformation of gluten-free dough formulations supplemented with hydrocolloids followed the order of

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xanthan > CMC > pectin > agarose. Moreover, the addition of xanthan to the gluten-free formulation resulted in a farinograph curve typical of wheat flour doughs. Schober et al. (2008) investigated the effect of HPMC on viscoelastic properties of

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zein-starch doughs for leavened gluten-free breads. HPMC stabilized the gas bubbles and significantly improved the quality of dough, resulting in a loaf that resembled wheat bread.

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Confocal laser microscopy revealed finer zein strands in the presence of HPMC, while dynamic oscillatory tests showed that HPMC rendered gluten-like hydrated zein above its glass transition temperature. Mancebo et al. (2015) evaluated the interaction between HPMC (2-4 g/100 g of flour) and rice flour on rheological properties of gluten-free bread. HPMC addition had non-significant effect on pasting properties and compliance values, but increased G' and G" values. In addition, when the dough hydration level was increased, there was a

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decrease in the influence of hydrocolloids on dough rheology, specific volume and bread hardness. Lorenzo et al. (2009) studied the effect of hydrocolloids on refrigerated and frozen

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non-fermented dough. The results revealed that formulations containing xanthan gum exhibited the best elasticity and resistance to puncture regardless of other hydrocolloids present in the dough (guar or HPMC). A panel significantly preferred xanthan/HPMC dough

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over a commercial gluten-free dough. Dough formulated with xanthan/guar gums showed the highest values of elastic modulus, while the lowest values corresponded to the HPMC doughs

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(with or without xanthan gum). This effect has been attributed to the hydroxyl groups in the hydrocolloid structure which allow more water interactions through hydrogen bonding (Rosell et al., 2001).

Mahmoud et al. (2013) evaluated the dough properties of gluten-free bread. The results of the study showed that the gluten-free bread formulations based on rice flour, corn

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flour and potato starch blends with different levels of hydrocolloids successfully allowed the entrapment of air bubbles in dough and provided stability to the dough mixture during breadmaking.

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Moreira et al. (2013) investigated the effect of hydrocolloids on the rheology of gluten-free doughs based on chestnut and chia flour. The rheological characterisation of

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chestnut flour doughs with chia flour at 4.0 g/100 g flour basis and a hydrocolloid (guar gum, HPMC or tragacanth gum) at different concentrations (0.5, 1.0, 1.5, 2.0 g/100 g) was carried out at 30°C using a controlled stress rheometer. Measurements of shear (0.01-10 s-1), oscillatory (1-100 rad s-1 at 0.1% strain), creep-recovery (loading of 50 Pa for 60 s) and temperature sweep (30-100°C) were performed. The simultaneous presence of chia and hydrocolloids modified significantly the rheological properties of doughs. Apparent viscosity at constant shear rate, storage and loss moduli at constant angular frequency decreased with

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increasing hydrocolloid content, except that the loss modulus of the dough containing tragacanth gum exhibited a reverse trend. Creep-recovery data showed that doughs elasticity improved with the presence of guar gum (65.9%), HPMC (64.8%) or tragacanth gum (45.8%)

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at 1.0, 2.0 and 1.0 (g/100 g), respectively. The rheological characteristics of gluten-free doughs and their effect on the quality of leavened bread were studied using amaranth, chickpea, corn, millet, quinoa and rice flour

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(Buresova et al., 2014). The rheological characteristics (resistance to extension R, extensibility E, R/E modulus, extension area and stress at the moment of dough rupture) were

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observed by uniaxial dough deformation. The dough exhibiting stronger resistance to extension, greater extensibility and higher stress at the moment of sample rupture had better bread baking quality. Specific loaf volume of gluten-free breads was positively correlated with dough resistance (r=0.86), dough extensibility (r=0.98) and peak stress at the moment of dough rupture (r=0.96). The results indicated that the baking performance of dough is closely

deformation.

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related to the proportion of dough resistance and the ability to stretch under uniaxial

Buresova et al. (2016) studied the effect of calcium and sodium caseinate supplements

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(2 g/100 g) on the behaviour of rice buckwheat dough and was compared to the effect of xanthan gum and carboxymethyl cellulose. The addition of caseinates significantly increased

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dough weakening, which became similar to dough with xanthan gum. During heating, the gelatinization rate became similar to dough with carboxymethyl cellulose. Moreover, peak viscosity was decreased by the addition of hydrocolloids. Farinograph characteristics showed that addition of sodium carboxymethyl cellulose

(NaCMC) in rice based formula has a positive influence on the rheological properties of dough. Wheat and rice flour doughs were used as control formulations in this study. Results obtained were compared with standard wheat dough. The farinograph curve showed

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significant improvement of gluten-free dough by adding NaCMC; a 500 BU consistency was reached, but the development time of dough was higher compared to wheat dough development. Addition of NaCMC has shown appropriate rheological behaviour of dough

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which leads to a higher quality of bread in volume and sensorial properties. The rheological measurements showed high improvements for the rice dough samples with 0.5% and 1% NaCMC, thus, the farinograph indicated a higher water absorption, and dough stability for

the rice dough control sample (Nicolate et al., 2016)

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5. Technological properties

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these samples. In addition volume was also increased with 31% in 1% NaCMC compared to

The technological properties of gluten-free breads are very important for industry and consumer acceptability which affects its value (Table 3). Instrumental analyses, including loaf weight and volume, specific volume, color and textural parameters have been frequently used to characterize gluten-free breads (Kittisuban et al., 2014; Aguilar et al., 2015). The

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gluten-free bread crumb microstructure is also characterised by using image analysis or scanning electron microscopy (Schober et al., 2007; Demirkesen et al., 2014). In addition, sensory attributes and nutritional composition have been used for assessing gluten-free bread

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quality (Matos & Rosell, 2011; Matos & Rosell, 2012). Acs et al. (1997) investigate the effect of guar gum, locust bean gum, xanthan and

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tragacanth gum on quality of bread. The results showed that these gums could be efficiently substituted in place of gluten in gluten-free breads, resulting in a highly significant increase in bread volume and loosening of the crumb. The HPMC was reported to be the most suitable for volume expansion of rice bread among several gums (Kang et al., 1997). These studies showed the feasibility of the application of HPMC, carageenan, guar gum, locust bean gum and xanthan gum for the development of bread.

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Effect of hydrocolloid mixture in gluten-free breads was studied by Gambus et al. (2001). Breads were prepared from potato starch, corn starch, corn flour and pectin, guar gum or their 1:1 mixture. The loaves containing gum shown better quality as compared to those

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made with added pectin in regards to volume, crumb moisture content oven loss and baking efficiency. However, the use of a guar gum and pectin mixture in a 1:1 ratio eliminated unwanted texture features of breads that resulted when using single hydrocolloid. In addition,

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the bread containing the mixture of guar gum and pectin showed the lowest firmness value. The extent of gelatinization in the guar gum based breads was reduced by partial replacement

affecting the moisture content.

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of this hydrocolloid by pectin, which significantly decreased crumb hardening without

Gan et al. (2001) reported that CMC and HPMC are better gluten replacers than guar gum in gluten-containing breads made out of composite flours (50:50 wheat flour:rice flour). The CMC at 0.4% and HPMC at 1.7% gave higher quality properties than guar gum at 0.7%.

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Subsequently, Shittu et al. (2009) observed that oven spring, specific volumes of bread loaf and crumb softness were higher at 1% xanthan gum content. The addition of xanthan gave the composite bread a more open crumb structure and better sensory acceptability. In addition,

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moisture loss and crumb firming during bread storage were best reduced when 1% xanthan was added to bread formulation.

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Guar gum has been also shown promising results by improving the volume and texture of frozen dough based bread (Ribotta et al., 2004). The use of HPMC has resulted in soft bread crumb loaves with higher specific bread volume, improved sensory properties and an enhanced shelf-life (Kittisuban et al., 2014). Similar behaviour has been reported for HPMC when the performance of bread stored at low temperatures was studied (Barcenas and Rosell 2006). Xanthan gum, HPMC and other hydrocolloids have been tested for their potential as bread improvers and antistaling agents (Guarda et al., 2004). The hydrocolloids

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were able to decrease the loss of moisture content of bread during storage, which consequently retarded the crumb hardening (Rosell et al., 2007). The combination of rice flour (45%), corn starch (35%) and cassava starch (20%)

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produced highly acceptable gluten-free bread (Lopez et al., 2004). Addition of xanthan resulted in a uniform crumb with well-distributed cells, and a pleasant flavor and appearance. Cato et al. (2004) investigated the loaf bread prepared from rice flour and potato starch,

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containing CMC, HPMC and guar gum, and compared with the wheat/rice mixtures bread. Evaluation of loaf volume, texture and crust and crumb color showed that HPMC had the

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most desirable effect on bread qualities. Sivaramakrishnan et al. (2004) confirmed the favorable effect of HPMC on the quality parameters of rice bread. Lee and Lee (2006) reported that the addition of HPMC decreased crumb hardness of fresh and stored gluten-free breads.

The textural comparisons of gluten-free bread containing xanthan (1.25%) or xanthan

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(0.9%) plus konjac gum (1.5%) have been studied by Moore et al. (2004). The results showed that, regardless of the addition of hydrocolloids, all gluten-free breads were brittle after 2 days of storage period, with decreases in springiness, cohesiveness and resilience. The

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differences among sorghum hybrids in the quality parameters of gluten-free breads were studied by Schober et al. (2005) using xanthan gum. The authors observed that increase in

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hydrocolloid content decreases the loaf specific volume. Consequently, the xanthan gum showed negative effects on crumb structure of sorghum breads. Ahlborn et al. (2005) revealed that a bread formulation containing rice, xanthan and

HPMC had showed a continuous matrix containing starch granule fragments. In addition of these hydrocolloids resulted in a formation of structure similar to gluten. Furthermore, the gluten-free rice bread had the highest sensory scores for moistness and freshness, which was due to the water-retention properties of xanthan and HPMC.

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Lazaridou et al. (2007) studied the effect of hydrocolloids on bread quality parameters in gluten-free formulations based on rice flour and corn starch. The extent of influence on bread quality was dependent on the specific hydrocolloid and its incorporation percentage.

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Generally, the volume of breads increased with addition of hydrocolloids except for xanthan; with increasing level of hydrocolloids, loaf volume decreased, except for pectin. High porosity values were found for breads supplemented with CMC and β-glucans at 1%

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concentration and pectin at 2%, whereas high crumb elasticity was exhibited by CMC, pectin and xanthan at 2%. The lightness (L*) value of crust was increased with the addition of β-

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glucan at 1%, whereas the whiteness of crumb was improved with inclusion of xanthan. Sensory evaluation results showed the highest score for overall acceptability to the glutenfree formulation supplemented with 2% CMC. During storage of breads a reduction in water activity and an increase in firmness of crumb were observed. Sciarini et al. (2012b) studied the effect of hydrocolloid on partial baked gluten-free bread. Hydrocolloid, especially CMC,

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had a positive effect on bread parameters and lowers the hardening during storage. The increase in crumb hardness was mitigated by hydrocolloid addition. CMC improved the specific volume, diminished crumb firmness and decreased amylopectin retrogradation.

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Overall, the crumb structure was observed to be more homogeneous for CMC based breads. Demirkesen et al. (2010) evaluated the effects of different combinations of

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hydrocolloids and emulsifiers on the quality of a rice-based gluten-free bread formulas. Results showed that 0.5% diacetyl tartatic acid ester of mono- and diglycerides combined with 0.5% xanthan–guar gum blend or xanthan–locust bean gum blend provided the best bread, with good volume and crumb texture and the highest scores for texture acceptability. Mahmoud et al. (2013) evaluated the quality of gluten-free bread, and the results showed that gums significantly improved the weight and roundness of gluten-free bread. All gluten-free bread formulations were sensory acceptable, since they resulted in highest scores in quality

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characteristics. The results concluded that the formulations (rice flour:corn starch:potato starch, 40:20:40) followed by

(rice flour:corn starch:potato starch, 40:40:20) with 3%

xanthan were the best formulation for the production of gluten-free bread.

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Mariotti et al. (2013) studied the influence of HPMC and dehulled and puffed buckwheat flour on the breadmaking properties of some commercial gluten-free bread mixtures. Addition of up to 40% buckwheat flour to the two optimized commercial gluten-

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free bread mixtures improved their leavening properties, which were correlated to final bread quality. The presence of a limited amount of puffed buckwheat flour, as well as of HPMC,

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proved useful in reducing diffusion and loss of water from bread crumb, and in limiting the interactions among starch and protein macromolecules, resulting in a softer gluten-free bread crumb and slower staling kinetics during storage.

Hager and Arendt (2013) investigated the influence of HPMC, xanthan gum and their combination on gluten-free breads. Effect of hydrocolloids on the gluten-free model systems

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varied according to the raw materials used. HPMC had a positive linear effect on volume of teff and maize breads and a negative linear effect on this parameter in rice breads, while the volume of buckwheat bread did not change. Xanthan addition had a negative linear effect on

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loaf volume of all breads. HPMC addition reduced crumb hardness of teff, buckwheat, maize and rice breads. Xanthan increased the crumb hardness of teff and buckwheat breads, while

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as rice bread crumb did not showed the significant effect. Crumb hardness values of maize breads were reduced by the addition of xanthan gum. The physical, textural and sensory properties of the gluten-free breads are largely

related to their structure at several levels that go from molecular to macroscopic levels. The microstructure of bread crumbs provides an accurate quantitative description of features of bread crumbs in terms of cell wall thickness, cell shape, void fraction and crumb fineness. Therefore, characterization of microstructure has an essential role in developing of products

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with desired quality (Demirkesen et al., 2014). X-ray microtomography technique was successfully used for characterization of gluten-free bread structures. Demirkesen et al. (2014) studied the effect of gum and gum blend addition on crumb structure of gluten-free

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breads. X-ray microtomography results indicated that addition of different gums or gum blends produced porous crumb structure of gluten-free breads. 2-D and 3-D images of bread crumbs showed that the crumb structure of breads prepared with methylcellulose and agar

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were similar to the control bread crumb structure in terms of heterogeneity and contained many void spaces. The highest number of pores and lowest porosity and average area of

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pores was obtained from gluten-free breads prepared with the addition of xanthan, CMC, xanthan-guar gum, xanthan-locust bean gum and HPMC, which is associated to the finer texture of these crumbs. The hardness, cohesiveness and springiness values of breads were correlated with their internal structure in terms of porosity, number of pores and average size of pores. It was observed that gluten-free breads with the lower hardness and higher

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cohesiveness and springiness values had a lower porosity, a higher number of pores and a lower average size of pores.

Mohammadi et al. (2014) investigated the effect of xanthan gum and CMC (5–20 g

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kg-1) on the quality parameters of gluten-free bread, based on rice flour and corn starch. The increase in CMC concentration yielded bigger gas cells, leading to better crumb porosity

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appearance. The xanthan containing bread showed the highest moisture content, so increase in xanthan gum concentration was more effective in decreasing hardness and increasing elasticity, in both fresh and stored breads. Kittisuban et al. (2014) used response surface methodology to analyze the effects of

HPMC, yeast β-glucan, and whey protein isolate on physical properties of gluten-free bread baked from formulas based on rice starch. The percentages of HPMC, yeast β-glucan, and whey protein isolate incorporated significantly affected the spread ratio, specific volume,

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hardness, cohesiveness, chewiness, and crumb color L* and b* values. However, the springiness, crumb color a* value, and moisture content were not significantly affected by any formulations investigated. Using the quality of wheat bread as a reference, the optimal

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gluten-free rice bread was produced by incorporating 4.35 g/100 g HPMC, 1 g/100 g yeast βglucan, and 0.37 g/100 g whey protein isolate based on dry weight of rice starch into the formulation. Moreover, the optimized rice starch bread was found to be acceptable according

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to the results of sensory analysis.

Naji-Tabasi and Mohebbi (2015) studied the effect of cress seed gum and xanthan on

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gluten-free bread. The results exhibited that hydrocolloids increased the moisture content and specific volume of gluten-free breads significantly. Image processing showed that hydrocolloid addition increased pore area and had a positive effect on crumb color during storage. It is speculated that the hydrocolloid, by forming thick layer, influenced the stability of gas cells and caused more regular pores in gluten-free bread which was more noticeable in

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breads containing cress seed gum. Fractal values of gas cell boundaries indicated that the breads containing cress seed gum had more regular and smooth boundaries. Texture analysis by gray level co-occurrence matrix revealed a stable crumb texture during storage.

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Demirkesen et al. (2013) studied the effects of chestnut flour and xanthan-guar gum blend and the emulsifier diacetyl tartaric acid ester of mono- and diglycerides mixture

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addition on macro- and microstructures of rice breads baked in conventional and infrared– microwave combination ovens. The highest pore area fraction values were obtained in breads prepared by replacement of 46 % of rice flour with chestnut flour containing a xanthan–guar gum blend and the emulsifier mixture and baked in an infrared–microwave combination oven. On the other hand, rice breads containing no additives or chestnut flour had the lowest pore area fraction values. The more homogenous pore distributions were observed when hydrocolloids and an infrared–microwave combination oven were used. The presence of

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hydrocolloids and infrared–microwave combination oven increased the uniformity of the microstructure of rice and rice-chestnut based breads. Hydrocolloid supplements impacted bread crumb characteristics. An open structure

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was found in crumb with added carboxymethyl cellulose as well as xanthan gum. Hardness of rice buckwheat crumb without hydrocolloids (12.2 N) was decreased by xanthan gum (9.1 N) and carboxymethyl cellulose (9.3 N). The overall sensory acceptability of rice buckwheat

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bread (7.1) was increased by carboxymethyl cellulose (7.8). The acceptability of bread with xanthan gum (5.9) was negatively impacted by dry, coarse crust and extremely sticky crumb

6. Nutritional properties

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(Buresova et al., 2016).

The nutritional aspect of gluten-free breads is also compulsory to fulfil and satisfy the needs of consumer in addition to technological properties. Gluten-free breads showed the great variation in the nutritional composition (Capriles & Areas, 2014). The most common

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strategy to enhance the nutritional value of gluten-free breads is to include nutritionally valued raw materials in addition to hydrocolloids. Non-traditional flours such as pseudocereals flours (amaranth, quinoa and buckwheat), tuber flours (potato, cassava, sweet

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potato, taro and yams), and leguminous flours (chickpeas, beans, lentils, peas and soybean) are gaining popularity in the production of gluten-free breads with enhanced nutritional

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properties (Mariotti et al., 2013; Augilar et al., 2015). The other raw materials such as sorghum flour (Hager & Arendt, 2013; Onyango et al., 2011), chestnut flour (Moreira et al., 2013), tigernut flour (Demirkesen et al., 2013) and teff flour (Hager & Arendt, 2013) have also been used as innovative in gluten-free breads. However, good quality gluten-free breads have been developed after optimising the bread-formulation recipe. Hydrocolloid based gluten-free breads have also been incorporated with different sources of fibres, antioxidants, vitamins and minerals. Fibre sources such as rice bran

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(Phimolsiripol et al., 2012) and inulin (Krupa-Kozak et al., 2012) have been added to glutenfree formulas with the consequent improvement in the nutritional quality. Psyllium gum added to gluten-free breads had a laxative effect due to its bulking effect, and after ingestion

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it expands and forms gel-like mass in the colon (Mishra et al., 2014). The pomace of different fruits has also been successfully incorporated into gluten-free doughs to increase their nutritional value (Matos & Rosell, 2015; Mir et al., 2015). The level

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of micronutrients and vitamins in gluten-free breads has also been a point of attention and has been enhanced by incorporating different functional raw materials. Gluten-free breads have

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been fortified with these nutrients either alone or combination with other nutrients. Pseudocereals such as amaranth and quinoa have shown hypoglycaemic effects and have been recommended as an alternative to traditional ingredients in the formulation of bread with a lower glycaemic index (Alvarez-Jubete et al., 2010). In addition to that many other ingredients have been recently incorporated into gluten-free bread formulations including

nutritional quality.

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dairy proteins, non-gluten vegetable proteins and isolate with the aim to increase their

Hydrocolloids also increased the nutritional value of gluten-free breads. Among the

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hydrocolloids, cellulose and its modified forms serve as dietary fiber (BeMiller, 2007). Nowadays, a wide range of hydrocolloids are thought to possess nutritive and physiological

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effects, including cereal β-glucan, pectin, inulin, gum arabic, resistant starches, levan, guar gum, chitosan, carrageenan, and others. Health benefits of these hydrocolloids are associated with appetite regulation (Dong et al., 2011; Li & Nie, 2015), bowel function, reduction of osteoporosis risk (Bosscher et al., 2006), and prevention of coronary heart diseases, type 2 diabetes mellitus and colon cancer (Hu et al., 2011). The bread was substituted with banana pseudo-stem flour (10%w/w) for that of commercial wheat flour, and added along with hydrocolloids (xanthan gum or sodium

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carboxymethylcellulose), which significantly increased the nutrient contents of composite breads. Chemical composition of composite breads were found to be rich in macro-and micro-minerals, total sugars, total pentosans, and resistant starch contents as compared to

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control bread. However, soluble pentosan, digestible starch, and total starch of the composite breads were observed to be lower than control bread. Additionally, all the composite breads (containing higher resistant starch) exhibited low in vitro starch hydrolysis rate and thus

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providing bread with lower glycemic index than the commercial white bread. Therefore, the banana pseudo-stem flour incorporated bread with added hydrocolloids could promote

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intestinal health and can be rendered suitable to be explored commercially as dietary supplement in people requiring low glycemic index breads (Ho et al., 2015; Matos & Rosell, 2015).

Hydrocolloids influence the digestion and absorption of available carbohydrates in a variety of ways. Studies indicated that a diet with guar gum prolonged mouth to cecum transit

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time, delayed gastric emptying, slowed down the increase in postprandial glycemia and provided benefits to colonic function (Cummings et al., 1978; Jenkins et al., 1979; Li & Nie, 2015). Guar gum in the intestine appears to inhibit the processes associated with digestion

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and absorption of available carbohydrates and thereby decreases the rate of glucose absorption into the hepatic portal vein that normally follows a starchy meal., The effect

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appears to be physical and starch fragments get caught up in the highly viscous network of guar gel, making them less accessible to digestive enzymes and slowing down their diffusion towards the small intestine. 7. Conclusion

Novel diagnosis methods and recent epidemiological observations have revealed the incidence of celiac disease. The alternative approaches have been developed to improve the quality of life of these patients. The replacement of gluten is major technological challenge

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for food scientists. Much research has been focussed on the development of gluten-free breads in an attempt to overcome the challenges of the absence of gluten. A range of ingredients, additives and processing aids are used for obtaining good quality products. In the

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bakery industry, hydrocolloids are of increasing importance as breadmaking improvers. They are widely used in baked goods to enhance dough handling properties, overall quality and to extend shelf-life. The use of hydrocolloids represents the most widespread approach used to

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mimic gluten in the manufacture of gluten-free breads, due to their structure-building and water-binding properties. Results from literature showed that textural parameters of gluten-

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free bread crumbs are strongly correlated with dough consistency and starch retrogradation. Based on successful applications of hydrocolloids it is suggested that novel nutritious ingredients, combined with hydrocolloids can be added to gluten-free bread formulations. 8. References

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Sciarini, L. S., Ribotta, P. D., Leon, A. E. & Perez, G. T. (2012b). Incorporation of several additives into gluten free breads: Effect on dough properties and bread quality. Journal of Food Engineering, 111, 590-597.

Shittu, T. A., Aminu, R. A., & Abulude, E. O. (2009). Functional effects of xanthan gum on composite cassava-wheat dough and bread. Food Hydrocolloids, 23, 2254-2260.

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Singh, H., & MacRitchie, F. (2001). Application of polymer science to properties of gluten. Journal of Cereal Science, 33, 231-243.

Sivaramakrishnan, H. P., Senge, B., & Chattopadhyay, P. K. (2004). Rheological properties of

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rice dough for making rice bread. Journal of Food Engineering, 62, 37-45.

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Table 1: Type of flour and hydrocolloids used in gluten-free breads

Mancebo et al. (2015) Naji-Tabasi & Mohebbi (2015) Demirkesen et al. (2014)

Xanthan gum, guar gum CMC, xanthan gum Carrageenan, alginate, xanthan gum, CMC Xanthan gum Xanthan gum, HPMC CMC, pectin, agarose, xanthan gum, β-glucan HPMC Xanthan gum

Demirkesen et al. (2013) Sciarini et al. (2012a) Sciarini et al. (2010)

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Cassava Rice, potato starch Rice, corn starch Rice Rice, potato starch, corn starch Rice Rice, potato starch Sorghum Rice, potato starch

HPMC Cress seed gum, xanthan gum Xanthan, guar, locust, methycellulose, CMC, HPMC HPMC CMC, Xanthan gum HPMC HPMC, Xanthan gum Guar gum, HPMC Xanthan gum, guar gum

Kittisuban et al. (2014) Mohammadi et al. (2014) Mariotti et al. (2013) Hager et al. (2013) Moreira et al. (2013) Mahmoud et al. 2013

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Rice Rice, corn starch Buckwheat Rice, maize, buckwheat Chestnut, chia Rice, corn starch, potato starch Chestnut, rice Rice, corn, soy Rice, corn, soy

References Ronda et al. (2015) Aguilar et al. (2015)

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Brown rice

Hydrocolloid HPMC Xanthan gum

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Type of flour Rice Chickpea, tigernut, corn starch Rice Rice, corn, corn starch

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Xanthan gum, HPMC HPMC Xanthan gum HPMC, CMC, guar gum Rice, corn starch, cassava Xanthan gum starch Rice HPMC

Shittu et al. (2009) Nunes et al. (2009) Lazaridou et al. (2007)

Lee and Lee (2006) Moore et al. (2006) Ahlborn et al. (2005) McCarthy et al. (2005) Schober et al. (2005) Cato et al. (2004) Lopez et al. (2004)

Sivaramakrishnan et al. (2004) CMC: carboxymethylcellulose; HPMC: hydroxypropylmethylcellulose

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Table 2: Dough properties of hydrocolloid based gluten-free breads

Rice

HPMC

Rice

HPMC

Chestnut, chia

Guar gum, HPMC

Buckwheat

Guar gum, HPMC, tragacanth gum

Rice, cassava, soya

Carrageenan, xanthan gum, CMC, alginate Carrageenan, alginate, xanthan gum, CMC Guar gum, HPMC, xanthan gum CMC, pectin, agarose, xantham gum

Dough property Increased elastic and viscous moduli values, increased creep recovery Increased dough elastic modulus and viscosity Increase elastic and viscous moduli values Gelatinization temperatures decreased with increasing hydrocolloid content, apparent viscosity at constant shear rate and storage and loss moduli at constant angular frequency decreased with increasing hydrocolloid content, Creep-recovery data showed that doughs elasticity improved with the presence of guar Increased strength to gas cells, increase in rheofermentographic indices, increased dough elasity, storage and loss moduli at constant frequency decreased with increase in hydrocolloid content expect tragacanth gum increase the loss modulus Increase storages modulus

References Naji-Tabasi & Mohebbi (2015) Ronda et al. (2015)

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Hydrocolloid Cress seed gum, xanthan gum

Mancebo et al. (2015) Moreira et al. (2013)

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Rice, corn, soy

Corn starch, cassava starch Rice, corn starch

Rice

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Type of flour Rice, corn, corn starch

Mariotti et al. (2013)

Sciarini et al. (2012b)

Increased consistency of dough and increased amylopectin retrogradatoin

Sciarini et al. (2010)

Increase elasticity, increased elastic modulus

Lorenzo et al. (2009)

Increased elasticity of dough, strenghtening dough, increased typical farinograph curve Increase visco-elastic moduli

Lazaridou et al. (2007)

Xanthan gum, Demirkesen et al. locust bean (2010) gum, guar gum, HPMC CMC: carboxymethylcellulose; HPMC: hydroxypropylmethylcellulose

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Table 3: Technological properties of hydrocolloid based gluten-free breads Hydrocolloid Xanthan gum

Bread property References Increased specific volume, reduced Aguilar et al. crumb hardness (2015)

Cress seed gum, xanthan gum

Improved colour, pore area fraction, increased moisture content, increased specific volume

Naji-Tabasi & Mohebbi (2015)

Brown rice

Xanthan gum, guar gum, locust bean gum, methycellulose, CMC, HPMC HPMC

Highest porosity values, increased cohesiveness and springiness

Demirkesen et al. (2014)

Buckwheat

HPMC

Rice, maize, buckwheat

HPMC, Xanthan gum

Chestnut, chia

Guar gum, HPMC

Rice, corn starch, potato starch Rice, corn, soy

Xanthan gum, guar gum

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CMC, Xanthan gum

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Rice, corn starch

Increased spread ratio, increase in specific volume Reducing crumb firmness, bigger gas cells leads to better crumb porosity Reduced loss of water, softer bread, slower staling kinetics, increased bread volume Increased volume, increased loaf specific volume, reduced crumb hardness Gelatinization temperatures decreased with increasing hydrocolloid content Lower loss of moisture, lower hardness

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Rice

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Type of flour Chickpea, tigernut, corn starch Rice, corn, corn starch

Rice

HPMC

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Rice

Increased specific volume, increased softening Carrageenan, Crumb firmness decreased, alginate, xanthan increased bread volume, increase gum, CMC cell average size Xanthan gum, locust Good volume bread and texture, bean gum, guar highest score for texture gum, HPMC Xanthan gum, Increased specific volume HPMC CMC, pectin, Increased volume, increase agarose, xanthan lightness (L*) value, high crumb gum porosity HPMC Decreased crumb hardness

Rice, corn, soy

CMC, xanthan gum

Rice

Rice, potato starch Rice, corn starch

Increased moisture and sensory properties

Kittisuban et al. (2014) Mohammadi et al. (2014) Mariotti et al. (2013) Hager et al. (2013) Moreira et al. (2013) Mahmoud et al. (2013) Sciarini et al. (2012a) Sciarini et al. (2010) Demirkesen et al. (2010) Nunes et al. (2009) Lazaridou et al. (2007) Lee & Lee (2006) Ahlborn et al. (2005)

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Rice, corn starch Rice

Xanthan gum, Konjac gum HPMC, guar gum, CMC Guar gum, pectin

Decrease in springiness, cohesiveness and resilience Increased specific volume

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Corn, corn Lowest hardness, decreased crumb starch, potato hardening starch CMC: carboxymethylcellulose; HPMC: hydroxypropylmethylcellulose

Moore et al. (2004) Cato et al. (2004) Gambus et al. (2001)

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Highlights •

Production of high quality gluten-free breads is a big challenge due to the absence of gluten, which confers unique viscoelastic properties to dough Hydrocolloids play an important for developing gluten-free breads

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Hydrocolloids significantly affect the dough handling and technological properties of

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gluten-free breads

Gluten-free breads are incorporated with various functional ingredients to increase

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their nutritional value