Hydrocolloids are a group of water-soluble polysaccharides with different chemical structures, high molecular weight and hydrophilic long-chain molecules.
1. Hydrocolloids in GF Bread
In GF doughs, hydrocolloids are used to create a viscoelastic network in order to balance the lack of gluten. Comprehensive reviews about the impact of the hydrocolloids on dough handling, technological and nutritional properties of GF breads underlined their function as structuring agents, mimicking the gluten network because of the ability to bind water
[1][2][3][4]. In addition, hydrocolloids bring positive effects on the viscoelastic properties of the GF dough and bread texture
[4].
A recent review stated that HPMC is the most favorable hydrocolloid in GF bread manufacturing
[5]. HPMC forms a gel network on heating and shows lower variability than other hydrocolloids
[6]. The presence of HPMC in the GF system makes the starch granules adhere to one another, and there is more space to entrap water in the system
[2]. HPMC, together with the components from the rice flour, form hydrophilic bonds that are beneficial to the water absorption and contribute to the stability and homogeneity of the GF dough
[7]. Factors that are related to HPMC functionality were related to the type of flours used, the presence of other ingredients and the percent of methoxyl groups contained in the HPMC molecule
[8]. Besides the HPMC addition and hydration levels, Morreale et al.
[7] pointed out the importance of HPMC viscosity to obtain GF rice breads with optimal quality.
The charge and the molecular weight of the hydrocolloids are amongst the main factors that influence bread quality
[2][9]. The polar charge has an effect on the water affinity. Negatively charged hydrocolloids are more prone to build intermolecular hydrogen bonds with water, while uncharged hydrocolloids have intramolecular hydrogen bonds that reduce the interactions with water
[2]. In a GF bread formulation based on potato starch, Horstmann et al.
[9] suggested that negatively charged hydrocolloids such as sodium alginate and pectin create repulsive forces with negatively charged phosphate groups of the potato starch, delaying the pasting and gelatinization of starch granules, leading to lower viscosity and therefore to higher bread volume due to the high gas cell expansion. On the other hand, hydrocolloids with a neutral charge and higher molecular weight, such as GG and locust bean gum, create hydrogen bonds with leached amylose that leads to higher viscosity, thus lowering the elasticity and decreasing bread volume due to limiting gas expansion. Moreover, the molecular weight affects the water holding capacity of hydrocolloids
[2][10]. Funami et al.
[10] correlated higher water holding capacity for hydrocolloids with a higher molecular weight. Because of the higher molecular weight of certain hydrocolloids (XG, CMC, agarose and β-glucan) and due to increasing concentration, Lazaridou et al.
[11] attributed the reduced loaf volume in GF bread formulation based on rice flour, corn starch and sodium caseinate.
Besides the factors mentioned above, the impact of hydrocolloids on the bread quality also depends on the level of the hydrocolloid used, the type of flour and other ingredients, as well as on the interaction with other components in the GF system
[1]. Regarding the presence of other ingredients, it was shown that protein addition at certain levels of addition causes antagonistic interaction with the hydrocolloids. For example, in a formulation with rice flour-cassava starch and 5% HPMC, the addition of soy protein isolate (1%, 2%, 3%) and egg white solids (5% and 10%) reduced dough stability by lowering the hydrocolloid functionality, modifying the available water within the dough, weakening the interactions between hydrocolloid and starch and, consequently, reducing the foam stability
[12]. Besides HPMC, other hydrocolloids such as XG and methylcellulose were reported to be used together with rich protein sources in GF formulations
[13].
Dough hydration in GF bread is an important feature of final product quality. The correct volume of water is significant for strengthening the three-dimensional dough structure
[7]. It is generally known that the greater the hydration, the higher the increment of the bread volume; there is a maximum hydration level after which the dough collapses during the baking process
[14]. Recently, Sahin et al.
[15] proved that Farinograph was a better tool in establishing the optimal amount of water in GF rice breads with different hydrocolloids as compared to the common method that uses the calculation based on the water hydration capacity of the individual ingredients: flour, starch and hydrocolloids. The authors stated that the advantage of the Farinograph method is that it takes into account the temperature changes during mixing and its effect on hydration, simulating the real process. Moreover, the Farinograph method provides data for dough stability and development time.
2. Effect of Hydrocolloids on Dough Rheology
The rheological behavior of dough is an important topic that has drawn significant attention in the research community, as rheology is linked to baking properties and bread quality. For example, it a correlation was found between the rheological properties of dough samples, and the firmness of GF bread as higher viscoelastic values of dough resulted in bread with lower hardness
[16].
Hydrocolloids improve dough development and gas retention by an increase in viscosity, which will permit the production of improved GF breads
[17].
Rheological investigation of the hydrocolloids effect on GF dough is achieved not only by empirical methodologies such as farinograph, alveograph, extensograph and Mixolab determinations but also with typical rheometers through creep-recovery and oscillation tests, which include strain and frequency sweeps that allow evaluating the viscoelastic dough properties
[11][18][19]. The rheometer measures the deformation energy stored in the sample during a shear process, which represents the elastic component (G’—storage modulus), while the deformation energy used up and lost during shearing represents the viscous component (G”—loss modulus) of the dough. In GF bread, an equilibrium between elastic and viscous properties is needed
[11]. Atypical viscoelastic behavior is achieved when G’ values are higher than G” values, which enables gas cell expansion.
Mancebo et al.
[20] stated that the creep-recovery test might estimate the bread quality characteristics better than the oscillatory test because the low deformations used in the latter do not correspond to the real processing and baking conditions.
Table 1. Effect of hydrocolloids on dough rheology.
Type of Hydrocolloid |
Level Used * |
Other Ingredients |
Type of the Rheological Test |
Effect |
References |
GG |
1% |
chestnut flour with 4% chia flour |
Creep-recovery (rheometer) |
Improved the dough elasticity by 65.9% |
[21] |
HPMC |
2% |
Improved the dough elasticity by 64.8% |
Tragacanth gum |
1% |
Improved dough elasticity by 45.8% |
XG–GG (mix) |
0.5% |
100% rice flour, 8% sugar, 8% shortening, 2% salt, 1% instant yeast, 150% water |
Frequency sweep |
Increased elastic and viscous moduli |
[16] |
CMC |
1% |
70% rice flour, 30% buckwheat flour, 85% water |
Frequency sweep |
Increased complex modulus, improved the internal structure, increased the crumb porosity, similar to the standard wheat bread |
[19] |
HPMC |
1% |
70% rice flour, 30% buckwheat flour, 85% water |
HPMC |
1% |
70% rice flour, 30% buckwheat flour, 100% water |
HPMC |
1–1.5% |
75% corn starch, 25% rice flour, 2% yeast, 4% sunflower oil, 4% sucrose, 2% salt, 75–85% water |
Shear properties, Power law |
Improved viscosity |
[6] |
GG |
Carrageenan |
XG |
HPMC |
5.5% |
22.2% corn meal, 77.8% corn starch, 5.5% sugar, 2.2% salt, 1.1% yeast, 83.3% water |
Strain and frequency sweep measurements |
Increased elastic and viscous moduli |
[22] |
XG |
4% |
90% sorghum flour, 10% potato starch, 100% water, 6% sugar, 3% baking powder, 1.5% salt |
RVA |
Lowered viscosity 2.8 vs. 3.4 cP (control) |
[23] |
HPMC |
3% |
90% sorghum flour, 10% tapioca starch, 100% water, 6% sugar, 3% baking powder, 1.5% salt |
3.3 vs. 3.4 cP (control) |
XG |
3% |
90% sorghum flour, 10% rice starch, 100% water, 6% sugar, 3% baking powder, 1.5% salt |
3.0 vs. 3.4 cP (control) |
Psyllium and HPMC |
0–4% and 2–4% |
100% rice flour, 3% yeast, 1.8% salt, 10% oil, 5% sugar, 90–110% water |
Dynamic oscillatory and creep-recovery test |
Psyllium incorporation reduced the pasting temperature and compliance values and increased elastic and viscous moduli |
[20] |
XG |
0.5–1.5% |
60% rice flour, 40% buckwheat flour, 1.5% salt, 4.4% oil, 5.3% yeast, 80–90% water |
Frequency sweep test |
Elastic modulus from 4 to 22 times higher than control |
[24] |
PGA |
0.5–1.5% |
Elastic modulus from 1.5 to 3 times higher than control |
XG |
0.5% |
45% rice flour, 45% cassava starch, 10% soy flour, 2% salt, 2% shortening, 3%yeast, 75% water |
Large deformation and frequency sweep |
Resistance: 35.6 vs. 46.3 g (control) |
[25] |
Carrageenan |
0.5% |
Increased moduli Elastic: 60.8 vs. 29.7 kPa (control) Viscous: 12.9 vs. 6.8 kPa (control) |
XG, CMC |
1% and 2% |
rice flour, corn starch, sodium caseinate, fresh yeast, sunflower oil, salt, sugar, 140–150% water |
Oscillation measurements |
Increased elasticity |
[11] |
The correct selection of the hydrocolloid and the amount of water in the recipe can lead to dough properties such as the wheat-containing one. In order to obtain high-quality GF bread, a high water content of up to 150% is needed
[16]. Investigating different types of hydrocolloids, Sabanis and Tzia
[6] found that XG required 10% more water than HPMC, GG and carrageenan in formulations based on corn starch and rice flour due to its higher water-binding capacity. Moreover, when increasing HPMC, GG and carrageenan addition levels from 1% to 2%, the water increased from 75% to 85%. In rice flour and cornstarch-based doughs prepared with different water amounts (130–150%), Lazaridou et al.
[11] reported a decrease in elastic modulus as the water amount increased.
Many research on GF dough formulations underlined that dough samples present viscoelastic properties up to 0.1% strain level and the decrease in linearity was very significant beyond 1% strain level, which indicates the breakdown of the GF dough structure
[11][22]. Similarly, with GF, wheat doughs showed linear viscoelasticity at strain levels lower than 0.1–0.25%
[26][27], while other systems have different viscoelastic regions; for example, zein suspensions had a linear viscoelastic region below 0.003% strain level
[28].
The addition of hydrocolloids to GF dough formulations showed increased elastic and viscous moduli. The elastic and viscous moduli of GF cornbread dough are increased with hydrocolloids addition, denoting a stronger dough structure formed by entrapping gas and retaining water, thus leading to higher viscosity
[22]. The authors found a higher increase for HPMC than guar-based doughs. The higher increase in moduli values produced by HPMC addition compared to other hydrocolloids was explained by its capacity to form a foam that enables it to entrap gas inside the dough structure
[2].
The oscillatory and creep tests showed that the elasticity and resistance to deformation of GF dough formulations supplemented with hydrocolloids followed the order: XG > CMC > pectin > agarose > β-glucan
[11]. The higher elasticity shown by XG was attributed to its property to form a weak gel at low shear rates.
Sciarini et al.
[25] used rheology at large deformation (resistance to penetration) and small deformation (frequency sweep) to study the hydrocolloids effect on GF dough prepared with rice flour, cassava starch and soy. The first method gives information about dough resistance, and XG showed the highest resistance, followed by CMC, alginate and carrageenan. The higher resistance given by XG was explained by its capacity to embrace a helix conformation in aqueous media, which changes the molecule into a rigid form. Regarding the frequency sweep tests, carrageenan was the only hydrocolloid, which showed a significant increase in both elastic and viscous dynamic moduli compared with a control dough; XG, alginate and CMC were similar to control.
Peressini et al.
[24] found that XG and propylene glycol alginate (PGA) enhanced the storage modulus of a rice–buckwheat dough, with greater effect for PGA. The rheological properties and crumb quality of dough were improved through the use of PGA, which is modified alginate characterized as amphiphilic with special surface activity and emulsifying capacity
[24][29]. A mixture of hydrocolloids improves both the structure and texture of the GF bread than the use of a single hydrocolloid. Zhao et al.
[29] stated that co-supported hydrocolloids (HPMC–PGA) improve the overall quality of GF bread; namely, HPMC acted as a skeleton, and PGA served as a supporting matrix. The dough structure was enhanced by the rearrangement of polysaccharide polymers.
In a formulation made with a mixture of rice and buckwheat flour, HPMC or CMC showed a reducing strength and extension of the 3D network in the dough rheological behavior. HPMC addition also showed a modification of the dough thermal behavior
[19].
It is known that hydrocolloids and starches that come from various botanical sources differ in functionality and properties related to granule size, composition or morphology that influence gelatinization, respectively. Thus, in GF sorghum bread formulations, the interaction between hydrocolloids (XG, HPMC and locust bean gum) and starches (potato, tapioca and rice) revealed that the best combinations in terms of bread quality were between potato starch (xanthan, tapioca starch) HPMC and rice starch (xanthan). Doughs with lower viscosities produced loaves with better crumb grain characteristics
[23].
Studying the interaction between different hydrocolloids, Mancebo et al.
[20] found no synergic effects between HPMC and psyllium in GF rice bread. Both hydrocolloids increased viscoelastic moduli, but only psyllium reduced the pasting temperature and compliance values, indicating higher dough strength
[20]. Psyllium has very similar rheological characteristics with XG, both being responsible for weak gelling properties. Psyllium shows important hydration capacity and gel-forming properties, able to entrap CO
2 [14].
By adding 5.5% psyllium to a formulation based on chickpea flour, an increase in consistency was shown during the initial stages of mixing at the beginning of heating related to protein network weakening as measured by the Mixolab technique
[30]. A favorable dough consistency explained the increased cohesiveness and springiness of the crumb, which are desirable outcomes in the GF bread-making process.
3. Effect of Hydrocolloids on Bread Hardness
Bread crumb hardness is an important textural attribute as it is associated with the perception of consumers for freshness as well as for its relation with product shelf life. Bread crumb texture is influenced by the ingredients and recipe used. Usually, hydrocolloid addition tends to decrease bread hardness. The type of hydrocolloid, concentration and interaction are the factors that contribute to the hardness of the bread crumb
[9]. As shown in
Table 2, different hydrocolloids decreased the hardness of GF bread.
Table 2. Effect of hydrocolloids on bread hardness compared to control.
Type of Hydrocolloid |
Level Used * |
Other Ingredients * |
Hardness, g or N ** |
References |
Carrageenan |
0.5% |
40% rice flour, 40% corn flour, 20% soy flour, 2% salt, 2% shortening, 3% compressed yeast, 158% water (flour basis). |
818 vs. 720 g |
[31] |
Alginate |
0.5% |
723 vs. 720 g |
XG |
0.5% |
402 vs. 720 g |
CMC |
0.5% |
639 vs. 720 g |
Gelatine |
0.5% |
730 vs. 720 g |
HPMC |
2% |
100% potato flour, 70% water, 1% yeast |
28.9 vs. 58.3 N |
[32] |
CMC |
1% |
32.7 vs. 58.3 N |
XG |
2% |
24.1 vs. 58.3 N |
Apple pectin |
1% |
33.6 vs. 58.3 N |
HPMC |
2% |
100% rhizome flour, 227% water, 1.5% salt, 3% yeast, 2% sugar, 2% oil |
316 vs. 263 g |
[33] |
HPMC, XG, GG |
0.29%, 0.21%, 0.50% |
323 vs. 263 g |
XG |
1.5% |
58.3% corn starch, 25% rice flour, 16.7% soy flour, 3.3% pre-gelatinized corn starch, 3.3% vegetable oil, 1.7% egg white, 1.6% salt, 1.6% sugar, 1.3% yeast, 0.42% sodium stearoyl lactylate |
5.1 vs. 26.2% |
[34] |
XG, CMC |
1%, 1% |
5.7 vs. 26.2% |
HPMC |
1.5% |
75% corn starch, 25% rice flour, 2% yeast, 4% sunflower oil, 4% sucrose, 2% salt, 80% water |
2.96 vs. 4.9% |
[6] |
GG |
1.5% |
3.46 vs. 4.9% |
Carrageenan |
1.5% |
3.94 vs. 4.9% |
GG |
5% |
100% fresh cheese, 50% tapioca starch, 20% pre-cooked corn flour, 10% margarine, 6% sugar, 97% milk |
16.5 vs. 20.0% |
[35] |
XG |
0.5% |
45% rice flour, 45% cassava starch, 10% soy flour, 2% salt, 2% shortening, 3% yeast, 75% water |
162 vs. 249 g |
[25] |
CMC |
0.5% |
113 vs. 249 g |
Carrageenan |
0.5% |
132 vs. 249 g |
Alginate |
0.5% |
141 vs. 249 g |
GG |
1.9% |
50% rice flour, 15% corn flour, 30.6% cornstarch, 4.4% potato starch, 1.6% salt, 5.1% yeast, 5.9% oil, 83.6% g water |
2.91 vs. 6 N |
[36] |
HPMC |
2.3% |
1.86 vs. 6 N |
Rice bread prepared with different types of hydrocolloids showed a softer crumb than control samples without addition, and the hardness increases with the following order: mix XG–GG < HPMC < guar < XG ≈ mix locust bean gum-XG < pectin < locust bean gum. The combination of hydrocolloids with an emulsifier such as DATEM further lowered the hardness values and improved bread quality regarding the specific volume and sensory properties
[16].
However, Calle et al.
[33] showed the highest value for hardness in the case of breads prepared with HPMC, XG and GG, but they attributed this increase to the type of flour used, a rhizome flour from
Colocasia spp. On the same level of hydrocolloids addition (2.5% reported to the amount of millet flour and tapioca starch), Chakraborty et al.
[37] showed that XG decreased the bread hardness as compared to other hydrocolloids, varying as follows: GG > GA > tragacanth > XG
[37]. On one side, XG was shown to have a softening effect over crumb hardness
[37][34], while other studies found an increase in crumb hardness
[6][11]. In line with the results of Lazaridou et al.
[11] for rice-based GF bread, Peressini et al. found elevation with XG level in the crumb firmness of rice–buckwheat bread
[24].
Differences may appear from the bread manufacturing process and especially from the amount of water used. Encina-Zelada et al.
[38] also showed that higher levels of XG (3.5%) at a constant water level (90%) led to an increased crumb hardness of bread formulated with 50% rice, 30% maize and 20% quinoa flours. By increasing the water content (to 110%), the hardness and consistency were decreased, producing bread with higher specific volume and softer crumbs; however, the high amount of water yielded stickier and less viscous doughs.
The capacity of the hydrocolloids to bind water helps to avoid water loss during bread storage. Sabanis and Tzia
[6] found that the crumb hardness increases in the following order: HPMC < GG < carrageenan.
At a higher concentration of GG, the hardness of GF cheese bread decreased. A mixture of GG and HPMC led to an increase in bread hardness, which was explained by the water competition among the hydrocolloids and between the hydrocolloids and tapioca starch, the main GF ingredient
[35].
In rice–buckwheat GF bread, the addition of XG or PGA improved crumb hardness by increasing the amount of water in the dough and, accordingly, the moisture content of the crumb because water has a plasticizing effect on the texture properties of the crumb cell walls
[24]. Propylene glycol alginate breads showed greater improvement in terms of increased specific volume, decreased crumb firmness and crumb structure than XG breads. The positive effects of PGA were explained by a combined effect of low dough viscosity and elasticity produced by the polymer and the capacity to form elastic films at the gas and liquid interface, thus protecting the gas cells from instability
[24].
By investigating the interactions between HPMC, psyllium and water in rice bread, no significant changes were recorded for specific bread volume when HPMC addition increased from 2% to 4% at different hydration levels between 90 and 110%. An opposite effect was observed in the case of increasing psyllium addition level from 0 to 4% when bread volume decreased and hardness increased. This outcome was diminished at higher water addition levels
[20].
This entry is adapted from the peer-reviewed paper 10.3390/foods10123121