Journal of Cereal Science 69 (2016) 174e181
Contents lists available at ScienceDirect
Journal of Cereal Science journal homepage: www.elsevier.com/locate/jcs
Effect of quinoa ﬂour on gluten-free bread batter rheology and bread quality Gulsum M. Turkut a, Hulya Cakmak a, Seher Kumcuoglu b, Sebnem Tavman b, * a b
Ege University, Graduate School of Natural and Applied Sciences, Department of Food Engineering, 35100, Bornova Izmir, Turkey Ege University, Faculty of Engineering, Department of Food Engineering, 35100, Bornova Izmir, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 July 2015 Received in revised form 4 March 2016 Accepted 5 March 2016 Available online 8 March 2016
A new gluten-free bread formulations composed of quinoa, buckwheat, rice ﬂour and potato starch were developed in the present study. Rheological characteristics of the bread batter with increasing amount of quinoa were determined; storage (G0 ) and loss modulus (G00 ) values were also measured for investigation of viscoelastic properties. To evaluate the quality of breads; technological and physical (bake loss %, speciﬁc volume, texture, microstructure, color), chemical (protein, moisture, ash) and sensory properties were determined. All batter formulations independent of the quinoa amount exhibited pseudoplastic behavior, and G0 values were found to be higher than G00 values in expressing the solid like characteristics of the batter. Amount of quinoa ﬂour addition did not present signiﬁcant difference on bake loss%, speciﬁc volume and protein content (p>0.05); however, 25% quinoa ﬂour bread displayed better results with its higher sensory scores and softer texture. Quinoa and buckwheat ﬂour mixture therefore will be a good alternative for conventional gluten-free bread formulations. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Quinoa Buckwheat Gluten-free Rheology
1. Introduction Prolamins in wheat, rye and barley are major sources for creating digestive problems in people with celiac disease (Capriles ^as, 2014). Nowadays, the treatment of this disease is only and Are possible by avoiding gluten in the daily diet. Gluten sensitivity ^as, represents the majority of food intolerance (Capriles and Are 2014), and the production of bread without gluten, is therefore essential. There are many conventional gluten-free bread recipes; however, the current technology of gluten-free bakery products is based only on starches from different botanical origins, such as corn and rice (Pruska-Kedzior et al., 2008). Unfortunately, those glutenfree products often have poor quality; lower loaf volume, poor texture (chalky and crumbly) and poor mouthfeel due to the lack of gluten elasticity and low nutritional value. Quality and shelf life of gluten-free breads can be improved by using pseudo-cereals such
Abbreviations: a, (þa: redness and a: greenness); b, (þb: yellowness and b: blueness); G0 , storage modulus; G00 , loss modulus; K, consistency index (Pa.sn); L, brightness (0: black, 100: white); n, power-law index; R2, coefﬁcient of determination; RMSE, root mean square error; g, shear rate (s1); h0, plastic viscosity (Pa.s); t, shear stress (Pa); t0, yield stress (Pa). * Corresponding author. E-mail address: [email protected]
(H. Cakmak). http://dx.doi.org/10.1016/j.jcs.2016.03.005 0733-5210/© 2016 Elsevier Ltd. All rights reserved.
as quinoa, buckwheat and amaranth with their nutritional value and the techno-functional properties (Torbica et al., 2010; ^as, 2014). Wronkowska et al., 2013; Capriles and Are Quinoa (Chenopodium quinoa) is an endemic crop of the Andean region (Stikic et al., 2012; Nascimento et al., 2014; Iglesias-Puig et al., 2015). It has been recognized as a very nutritious grain, due to the good quality and quantity of its protein and essential fatty acids (Hager, 2013). Essential amino acid content has also been found to be higher than that of wheat ﬂour (Stikic et al., 2012); especially, lysine (a limiting amino acid for cereals) was found to be twice higher than wheat ﬂour. According to the USDA nutrient database (2014), quinoa consists of 14.12% protein, 6.07% total lipid (fat), 64.16% carbohydrate and 7% dietary ﬁber. NASA declared that quinoa is an excellent crop with its good nutritional balance and that it can be used during long term human space missions (Schlick and Bubenheim, 1993). Clinical studies about the consumption of quinoa have indicated that childhood malnutrition and risk of cardiovascular diseases (by lowering triglycerides, LDL and cholesterol) may be reduced and help to modulate metabolic parameters (postmenopausal symptoms) in women with excess weight (Graf et al., 2015). In addition to good nutritional composition, quinoa does not contain any gluten, which has brought a new perspective to gluten-free bakery products. Buckwheat (Fagopyrum esculentum) is another pseudo-cereal
G.M. Turkut et al. / Journal of Cereal Science 69 (2016) 174e181
crop that attracts attention with its nutritional composition, since it contains 13.25% protein, 3.4% total lipid (fat), 71.50% carbohydrate, and 10% dietary ﬁber (USDA, 2014), as well as essential vitamins _ lu, 2015). Studies have shown that and minerals (Bilgiçli and Ibano g antioxidant capacity and amount of aroma compounds were improved in buckwheat bread compared to wheat ﬂour bread (Lin et al., 2008). Replacement of wheat ﬂour with an increasing amount of buckwheat ﬂour also increased the mineral content of breads; Cu, Fe, K, Mg, Mn, P and Zn were statistically higher than in the _ lu, 2015). control sample (Bilgiçli and Ibano g The aim of this study was to develop a new gluten-free bread formulation from different amounts of quinoa and buckwheat ﬂour incorporated into rice ﬂour and potato starch mixture. The effects of quinoa and buckwheat ﬂour were evaluated by means of rheological properties of bread batter as well as technological, physical, and sensory properties of gluten-free breads. 2. Materials and methods
Table 1 Bread formulations, ﬂour composition, ﬂour and bread properties, A: Gluten-free bread formulations for 100 g of total ﬂour þ starch basis; B: composition and water absorption capacities of ﬂours; C: baking properties of gluten-free breads. A Sample code Ingredients (On ﬂour þ starch %)
Rice ﬂour Potato starch Quinoa ﬂour Buckwheat ﬂour Salt Sugar Oil Yeast Xanthan gum Water
25 25 e 50 2 3 6 3 0.5 87
25 25 12.5 37.5 2 3 6 3 0.5 87
25 25 25 25 2 3 6 3 0.5 87
25 25 37.5 12.5 2 3 6 3 0.5 87
25 25 50 e 2 3 6 3 0.5 87
B Flour type
Moisture Ash1 Protein1 SDF1 IDF1 (%) (%) (%) (%) (%)
Quinoa Buckwheat Rice Potato starch
9.13a 9.95a 16.07c 11.22b
16.48c 119.87c 12.58b 102.67b 4.85a 146.16d e 67.79a
2.1. Materials Whole quinoa seed was purchased from Bora Tarim Urunleri Gida San. Tic. Ltd. (Istanbul, Turkey). Buckwheat seeds (Degirmen Tic., Izmir, Turkey), rice ﬂour (Kenton, Ankara, Turkey), potato starch, sugar, salt, sunﬂower oil, compressed yeast (Pakmaya, Izmir, Turkey) and xanthan gum (SigmaeAldrich) were purchased from local markets in Izmir. Quinoa and buckwheat seeds were ground in a lab scale hammer mill (Armﬁeld, UK), and then subjected to sieving. Flours having a diameter lower than 0.5 mm were used in the experiments. 2.2. Methods 2.2.1. Preparation of breads Gluten-free bread formulations are given in Table 1A. The formulation was developed according to the study of AlvarezJubete et al. (2010) with some major modiﬁcations: rice ﬂour and potato starch were kept constant at 50% of the total ﬂour and starch mixture, and buckwheat ﬂour was replaced with increasing amounts of quinoa ﬂour. The control bread (C) was composed of only buckwheat ﬂour, rice ﬂour and potato starch. The amount of water used in the formulations was kept constant at 87% (on ﬂour mixture basis) as recommended in the study of Alvarez-Jubete et al. (2010) and the structure of obtained mixtures were like a thick batter rather than dough. For the batter preparation, all ingredients except xanthan gum were mixed thoroughly for 10 min at low speed in a spiral mixer (Kitchen Aid 5k45 Mixer, USA). After the addition of xanthan gum, the batter was mixed for another 5 min at high speed. The batter was then divided into 400 g portions and poured into Teﬂon-coated baking pans. Finally, it was fermented in the fermentation chamber (Inoksan FGM 100, Turkey) at 35 C and 85% RH for 30 min. Following the fermentation step, the samples were baked at 200 C and 50% RH for 50 min in a convection oven (Inoksan FBE 010, Turkey). The bread was removed from the pans immediately after baking and cooled at room temperature (25 C) for at least 6 h before the analyses. 2.3. Rheological measurements Rheological measurements were conducted using a DHR3 rheometer (TA Instruments, USA). Bread batter were prepared according to the formulations given in Table 1A without adding any yeast to the formulations as recommended in the study of
2.35b 2.21b 0.55a 0.51a
15.54c 14.72b 7.07a e
2.09b 1.74a 1.49a e
14.39b 10.84b 3.39a e
Water absorption capacity (%)
C Sample code
Bake loss (%)
Speciﬁc volume (cm3/g)
C Q1 Q2 Q3 Q4
14.4a 15.4a 15.1a 15.1a 15.4a
1.87a 1.85a 1.76a 1.78a 1.73a
47.5c 44.3b 44.4b 41.2a 40.9a
7.65a 7.81a 8.40a 8.17a 8.18a
1.68a 1.36a 2.33a 2.16a 2.06a
0.940c 0.930c 0.930c 0.925a,b 0.910a
Different letters in the same column indicate signiﬁcant differences between means (p < 0.05). 1 On dry basis.
Demirkesen et al. (2010a). All measurements were conducted at 25 C, using parallel plate geometry (40 mm diameter, with 1 mm gap). Amplitude sweep analyses were carried out between 103e102% strain to determine linear viscoelastic region of the batter samples. The amplitude sweep test results showed that all bread batter formulations showed a linear region between 0.1 and 10%; therefore, 0.1% strain was selected for frequency sweep tests for determining differences between samples. Frequency sweep experiments were carried out between a frequency of 0.1e10 Hz, and storage (G0 ) and loss modulus (G00 ) versus frequency values were recorded. Flow ramp tests were conducted at shear rate between 0.01 and 50 s1 under steady shear conditions. Bread batter formulations were prepared in two parallels, the rheological experiments were performed in triplicate, and their averages are reported in this study.
2.4. Analysis of ﬂour samples Water absorption capacity and protein content of ﬂour samples were measured according to AACC method no 56-11 and 46-12, respectively (AACC, 2010). Moisture (ICC, 1996), and ash contents (ICC, 1996) of the ﬂour were determined using ICC standard methods. Soluble and insoluble dietary ﬁber content of the ﬂours was determined by using AOAC method no 991.43 (AOAC, 1998).
G.M. Turkut et al. / Journal of Cereal Science 69 (2016) 174e181
2.5. Analyses of breads 2.5.1. Physical properties of bread Bake loss of breads was determined according to the following formula;
Bake loss ð%Þ ¼ ½ðWbb Wab Þ=Wbb 100
where Wbb is the weight of the loaf before baking and Wab is the weight of the loaf after baking and cooling (Alvarez-Jubete et al., 2010). Speciﬁc volume of the breads was determined by rapeseed displacement method according to AACC method 10-05 (AACC, 2010). Protein contents of breads were determined by AACC method 46-12 (AACC, 2010). Moisture (ICC, 1996) and ash contents (ICC, 1996) of breads were determined according to ICC standard methods. Water activity of the bread samples were measured using a Testo AG 400 measurement device (Lenzkirch, Germany). Data were obtained from the averages of three replicates of each formulation. 2.5.2. Texture of the bread crumbs Texture proﬁle analysis (TPA) of bread crumbs was performed the day after baking using TA-XT 2i model texture analyzer (Stable Micro System Co. Ltd., Surrey, England) equipped with a 30 kg load cell. A cylindrical probe of 36 mm in diameter was attached to the crosshead. The instrument test parameters included: pre-test speed: 2.0 mm/s; crosshead speed: 1 mm/s; post-test speed 5.0 mm/s and compression set to 40%. Bread loaves were sliced into 15 mm thickness and crusts were removed before analysis. Textural quality properties (hardness, springiness, cohesiveness, chewiness, adhesiveness and resilience) of bread slices were measured, but results of adhesiveness and resilience are not shown in the present study. All the tests were conducted in six parallels, and the average values are reported. 2.5.3. Scanning electron microscopy (SEM) images of ﬂours and breads Quanta FEG 250 Scanning Electron Microscope (FEI, Czech Republic) was used to examine ﬂour and crumb structures. Bread crumbs were cut into cubes (1 cm3) and dried in a freeze-drier (Armﬁeld, FT 33, England) for 6 h prior to microscopic analysis. An accelerating voltage of 7 kV and 10 kV was used for ﬂours and breads; system pressures were 80 Pa and 110 Pa for ﬂours and breads, respectively. Those obtained SEM images of ﬂours were evaluated with ImageJ software for determining particle size distribution. 2.5.4. Color analysis The crust and crumb colors were measured using HunterLab ColorFlex (Hunter Associates Inc., Reston, VA, USA). Averages of three measurements of L (brightness; 0: black, 100: white), a (þa: redness; a: greenness) and b (þb: yellowness; b: blueness) values were recorded. 2.5.5. Sensory analysis Sensory analysis was performed with a group of 25 semi-trained panelists, none of them having celiac disease, recruited among the staff, undergraduate and graduate students of Ege University Food Engineering Department. Panelists were asked to assess the glutenfree breads for ﬂavor, crumb hardness, crumb color and overall liking. Each sensory attribute was evaluated with a ranking test with a scale of “1” (the least) to “5” (the most). The sensory analysis was conducted in duplicate.
2.5.6. Statistical analyses Results were analyzed using SPSS software version 20.0. Data were compared using analysis of variance (ANOVA) and the calculated mean values compared using Duncan's multiple range test with a signiﬁcance level of 95%. Rheological models were tested in Matlab software 7.12.0 (Mathworks Inc., USA) using curveﬁtting tool box. 3. Results and discussion 3.1. Composition of ﬂours Composition and water absorption capacities of the ﬂours used in this study are presented in Table 1B. These results were in accordance with the literature. Moisture content of quinoa ﬂour was given between 9.97 and 12.62%; ash was between 1.97 and 5.46%; and protein content was between 12.05 and 15.47% € mo €sko €zi et al., 2011; Repo-Carrasco-Valencia and Serna, 2011; (To _ € ste et al., 2014; Bilgiçli and Ibano lu, 2015). For buckwheat ﬂour, Fo g moisture content given in the literature was between 9.72 and 10.60%, ash was between 1.92 and 2.00%, and protein content was between 11.50 and 15.80% (Pruska-Kedzior et al., 2008; Bilgiçli and _ lu, 2015; Wronkowska et al., 2015). Ibano g Soluble and total dietary ﬁber content of quinoa ﬂour were found signiﬁcantly higher than buckwheat ﬂour as presented in Table 1B (p < 0.05). Insoluble dietary ﬁber of quinoa and buckwheat were found statistically in the same group (p > 0.05). Soluble dietary ﬁber content of raw quinoa seed is given from 1.41 to 2.3% on dry basis, and total dietary ﬁber is given from 13.40 to 15.99% on dry basis in the literature (Ruales and Nair, 1994; Repo-CarrascoValencia and Serna, 2011). For buckwheat seeds, soluble dietary ﬁber is given as 2.21% (He˛ s et al., 2014), and total dietary ﬁber is der et al., 2010). between 12.18 and 13.05% on dry basis (Le Water absorption capacity of ﬂour is related with protein (Ogungbenle, 2003) and ﬁber content (Torbica et al., 2010). Quinoa having higher soluble dietary ﬁber than buckwheat ﬂour then gradually increased the water absorption capacity of bread batter by replacement of buckwheat with quinoa ﬂour. Quinoa with its dietary ﬁber content is used to improve the structure of highly viscous food products such as dough and bakery products (Ogungbenle, 2003). 3.2. Rheological properties of bread batter Fig. 1 represents the effect of quinoa ﬂour supplementation on gluten-free bread batter rheology at constant water level without yeast addition. Shear stress (Pa) versus shear rate (s1) data was ﬁtted to power law (Eq. (2)), HerscheleBulkley (Eq. (3)), and Bingham model (Eq. (4)) as given in the following equations;
t ¼ KðgÞn
t ¼ KðgÞn þ t0
t ¼ t0 þ h0 g
where t indicates shear stress (Pa), g indicates shear rate (s1), K is the consistency index (Pa.sn), n is the power-law index, t0 yield stress (Pa) and h0 represents plastic viscosity (Pa.s). These rheological models were compared depending on R2 and root mean square error (RMSE), and the higher R2 with lower RMSE showed the best ﬁt among them. The rheological models ﬁtted to experimental data shows a good correlation (R2 ¼ 0.9079e0.9992),
G.M. Turkut et al. / Journal of Cereal Science 69 (2016) 174e181
although power law model presents statistically better results (Table 2). Flow behavior index values of power law model were found between from 0.18 to 0.30, and from 0.19 to 0.47 for Herschel-Bulkley model, therefore all the batter samples displayed shear thinning (pseudoplastic) behavior. Similar results were observed by researchers who studied rheological properties of rice bread dough containing different gums with or without emulsiﬁers (Demirkesen et al., 2010a) and gluten-free bread dough from corn starch and rice ﬂour, including hydrocolloids (Sabanis and Tzia, 2011). Addition of quinoa ﬂour signiﬁcantly affected K values and the viscosity. This could be related with the increasing amount of quinoa caused an increase in water absorption capacity of batter by higher soluble dietary ﬁber fraction than buckwheat as similarly € ste et al. (2014). Increasing amounts of quinoa ﬂour also stated by Fo resulted in a higher consistency index for power law model; on the contrary, increasing quinoa rate resulted in a decrease in K in Herschel-Bulkley model. Yield stress values and plastic viscosity of the batters shown in Herschel-Bulkley and Bingham model also increased with increasing quinoa rate. As stated in the literature, ﬁber supplementation in the gluten free bread dough inﬂuences the resistance to ﬂow by entanglement of ﬁber and increase the yield stress as well as apparent viscosity (Demirkesen et al., 2010b). Viscoelastic properties of all gluten-free batters are shown in Fig. 1B and C, depending on their frequency sweep responses. Storage (or elastic) modulus, G0 was greater than the loss (or viscous) modulus, G00 , and both increased with increasing frequency for all tested samples. This behavior indicates that those gluten-free batter formulations had a solid like structure. Similar observations have been stated in the literature. The elastic modulus of gluten-free dough prepared with buckwheat, rice and maize ﬂour was greater than loss modulus (Pruska-Kedzior et al., 2008). G0 and G00 values of control sample were smaller than the values of that batters containing quinoa ﬂour at each level. Also increasing amounts of quinoa ﬂour increases elasticity of the bread batter and €ste et al. improves the dough structure in the same way as gluten. Fo (2014) stated that gluten-free dough became more elastic with increasing the amount of quinoa bran at the same frequency range (1e10 Hz). Storage modulus of all formulations increased exponentially (R2 > 0.95), although the incline was sharper for the control sample at lower frequencies (0.1e1.0 Hz). Also, G00 values were found to be exponentially increasing (R2 ¼ 0.82e0.95) for all samples between the studied frequency ranges (1e10 Hz). 3.3. Evaluation of bread properties Baking properties of breads, i.e. percent of bake loss, speciﬁc volume, water activity, protein, ash and moisture content are shown in Table 1C. No signiﬁcant differences were observed in bake loss, speciﬁc volume, protein and ash values of breads containing different amounts of quinoa ﬂour (p>0.05). Baking loss was found in accordance with the study of Hager (2013), however the formulation was
rather different, and the gluten-free dough was prepared with a variable amount of water. Moisture of the samples was found between 40.9% and 47.5%. The control sample (C) which includes the highest amount of buckwheat ﬂour, had signiﬁcantly the highest moisture content, while Q4 bread had the lowest moisture. The moisture content of gluten-free bread signiﬁcantly decreased with increasing amount of quinoa ﬂour in gluten-free bread (p < 0.05). Alvarez-Jubete et al. (2010) indicated that bread with quinoa ﬂour (50% quinoa ﬂour, 50% rice ﬂour, 87% water) had lower moisture content than buckwheat ﬂour bread (50% buckwheat ﬂour, 50% rice ﬂour, 87% water) similar to our ﬁndings. Q4 bread (the highest percent of quinoa) had 40.9% moisture, while the control bread (the highest percent of buckwheat) had 47.5%. This could be attributed to the differences in soluble dietary ﬁber contents of the buckwheat and quinoa ﬂour. Speciﬁc volume is one of the primary quality parameters of bread. Although the negative effect of quinoa and buckwheat ﬂour on the speciﬁc volume of bread has been stated in the literature (Torbica et al., 2010; Stikic et al., 2012; Bilgiçli and _ lu, 2015; Iglesias-Puig et al., 2015), there was no signiﬁcant Ibano g difference (p>0.05) observed between samples containing different amounts of quinoa. Agents such as gums can help to retain gas in a gluten-free dough matrix (Delcour and Hoseney, 2010) and therefore it may help to retain the speciﬁc volume similar with the control sample and negative effect of quinoa ﬂour on speciﬁc vol€ ste et al. (2014) reported that the ume therefore compensated. Fo replacement of rice and corn ﬂour by 40% whole grain quinoa ﬂour signiﬁcantly increased bread volume, while addition of the same amount of quinoa bran signiﬁcantly decreased loaf volume. In addition, Sabanis and Tzia (2011) reported that higher consistency index values and apparent viscosity in their gluten-free dough resulted in lower speciﬁc volume. Sample Q4, having higher K value obtained from power law model, had the lowest speciﬁc volume among the samples, although the difference was not signiﬁcant (p>0.05) differing the given literature. Digital images of bread samples are shown in Fig. 2. 3.4. Result of texture analysis The results of texture proﬁle analysis of gluten-free breads are presented in Table 3A. The required force to compress foods between teeth demonstrates hardness since it stimulates the freshness perception of foods (Giannou and Tzia, 2007). Therefore, the bread with 25% quinoa ﬂour which had the lower instrumental hardness value had also the higher sensory ﬂavor score. As stated in Table 3A, the control bread had lower cohesiveness and chewiness. This can be related to the higher moisture content (47.5%) of the control bread. It was also observed that increasing the amount of quinoa ﬂour increased crumb hardness and chewiness. Wronkowska et al. (2013) stated in their study that amount of buckwheat ﬂour signiﬁcantly affects crumb hardness, because the increasing levels decreased the crumb hardness. For the control sample, which had the highest amount of buckwheat, the crumb texture was not signiﬁcantly different from Q3 and Q4 breads
Table 2 Statistical results of ﬁtted rheological models. Power law model
C Q1 Q2 Q3 Q4
117.80 120.60 144.80 181.80 182.60
0.18 0.29 0.29 0.29 0.30
0.9873 0.9943 0.9940 0.9992 0.9981
3.307 4.398 5.996 2.774 4.391
110.90 79.52 78.87 74.36 73.04
0.19 0.35 0.40 0.45 0.47
10.38 49.67 83.99 142.90 148.00
0.9799 0.9952 0.9968 0.9808 0.9958
4.341 4.197 4.519 13.910 6.723
154.90 181.50 223.30 277.90 279.80
2.02 4.07 5.38 6.64 7.17
0.9079 0.9398 0.9504 0.9254 0.9331
9.217 14.780 17.660 27.350 27.860
K; consistency index; n; ﬂow behavior index; t0; yield stress, h0; plastic viscosity.
G.M. Turkut et al. / Journal of Cereal Science 69 (2016) 174e181
Fig. 1. Rheological properties of batters; A: ﬂow curves, B: storage modulus (G0 ), C: loss modulus (G00 ) of batter samples.
Fig. 2. Crumb (A), and crust (B) images of bread slices.
(p>0.05). The effect of buckwheat ﬂour may be suppressed by quinoa ﬂour, that is, breads made with quinoa ﬂour have comparably higher crumb hardness than breads with buckwheat ﬂour, as indicated by other researchers (Alvarez-Jubete et al., 2010). Also, Iglesias-Puig et al. (2015) reported that crumb ﬁrmness (hardness) increased when the amount of quinoa in wheat ﬂour þ quinoa ﬂour
mixture rose from 25 g/100 ge50 g/100 g. Crumb springiness values did not considerably change between quinoa breads and the control bread.
G.M. Turkut et al. / Journal of Cereal Science 69 (2016) 174e181
Table 3 Physical and sensorial properties of gluten-free breads, A: Texture proﬁle analysis, B: crumb and crust color, C: Sensory evaluation of gluten-free breads. A Sample code
Crumb hardness (N)
C Q1 Q2 Q3 Q4
0.81 0.84b 0.84b 0.81a,b 0.79a
24.3 16.4a 18.9a 32.6b 35.0b
5.39a 5.86a 5.77a 9.81b 12.17c
0.41 0.44a.b 0.47b 0.45a,b 0.42a
B Crumb color Sample code C Q1 Q2 Q3 Q4
51.4a 56.3b 58.5c 60.9d 65.5e
6.8e 6.6d 6.4c 6.0b 5.5a
10.3a 12.3b 13.8c 15.2d 16.9e
42.9a 44.2b 45.5c 46.4d 47.9e
14.9e 14.8d 14.4c 14.3b 14.2a
15.8a 16.1b 16.2c 16.5d 16.8e
C Sample code C Q1 Q2 Q3 Q4 aee
2.96 3.60a,b 4.24b 2.68a,b 3.48a,b
4.60 3.44b 3.04a,b 2.52a 2.44a
5.60 4.60c 4.00b 3.20a 2.64a
Overall liking 1.20a 2.80b 4.96d 2.48b 3.48c
Different letters in the same column indicate signiﬁcant differences between means (p < 0.05).
3.5. Scanning electron microscopy (SEM) analysis SEM images of the ﬂour samples used in the production of gluten-free breads are shown in Fig. 3. For comparison of particle size, images with the same magniﬁcation level are presented in this ﬁgure. The images were evaluated with ImageJ software and at least 50 different particles were measured from three different images for each ﬂour type for calculation of average particle size distribution. As can be seen in this ﬁgure, potato starch has the largest particle size, 16.86 ± 4.66 mm, while the smallest particle size was observed for quinoa ﬂour (1.43 ± 0.22 mm). The average particle size of buckwheat ﬂour was found as 4.74 ± 0.88 mm, and for the potato starch it was found as 5.78 ± 1.11 mm. SEM images of gluten-free bread crumbs are shown in Fig. 3. Up to 50% of quinoa ﬂour, starch granules are visible in the structure. Breads with 37.5% and 50% of quinoa ﬂour showed more homogeneous structure than the rest. Especially, less porous, and more sheet-like structure can be seen in the image of bread with 37.5% quinoa ﬂour. The sheet-like structure is attributed to gluten proteins (Fleming and Sosulski, 1978), which can withstand the pressure difference that occurs during baking. However, for gluten-free bread dough, this pressure difference cannot be tolerated and therefore smaller pores occur at the weakest points that are covering starch granules (Fleming and Sosulski, 1978). The smallest particle size distribution of quinoa ﬂour, especially at a higher quinoa ﬂour replacement level, may therefore affect the ﬁnal porous structure of the Q4 bread.
3.6. Color analysis Bread color is a result of complex chemical reactions between proteins and carbohydrates during the baking process. Moreover, the bread formulation itself could change the ﬁnal bread color. The effects of quinoa ﬂour on bread color are shown in Table 3B. Crust and crumb color of control and quinoa breads were statistically different (p<0.05), and the amount of quinoa ﬂour created a noticeable difference on all color parameters for both crumb and
crust. Especially, the yellowness of bread crumb was the highest in the highest quinoa replacement due to the characteristic quinoa color. Gluten-free breads are usually identiﬁed by having lighter color than wheat breads because of starches and rice ﬂour; thus, darker color in breads is favorable (Wronkowska et al., 2013). Although studies indicate that increasing the amount of both quinoa and buckwheat ﬂour statistically decreased the lightness values of crumb and crust (Alvarez-Jubete et al., 2010; Wronkowska et al., _ lu, 2015), there was no such difference 2013; Bilgiçli and Ibano g observed in the present study. This result could be related to the composition of gluten-free bread, since it contains a constant amount of rice ﬂour and potato starch. 3.7. Sensory evaluation Sensory evaluation of gluten-free bread was performed using a ranking test for different bread quality attributes. The results are presented in Table 3C. Differences in crumb color were clearly perceived by the panelists and these results are in agreement with the instrumental color values, that is, crumb lightness was increased with increasing amount of quinoa. Gluten-free bread with 25% quinoa ﬂour statistically had the highest average score in ﬂavor, and overall liking, while the control sample received the lowest average scores for those quality attributes. The difference in sensory hardness of breads was not clear as the instrumental values, but even so, the similarity in the hardness of Q1 and Q2 breads were perceived by the panelists. Sensory analysis of newly developed gluten-free breads may be conducted with people having celiac disease in future studies for further improvement of these formulations, since their sensory perception might differ from other people. 4. Conclusions Gluten-free bread batter was formulated with rice ﬂour, potato starch and buckwheat ﬂour which were replaced with increasing
180 G.M. Turkut et al. / Journal of Cereal Science 69 (2016) 174e181 Fig. 3. Scanning electron micrographs (10000) of ﬂour samples, A: quinoa, B: buckwheat, C: rice ﬂour, D: potato starch (in the upper row); scanning electron micrographs (2500) of the crumbs of control (C) and quinoa breads (in the lower row).
G.M. Turkut et al. / Journal of Cereal Science 69 (2016) 174e181
levels of quinoa ﬂour. The new gluten-free bread formulations were evaluated according to rheological properties, chemical composition, technological properties and sensory attributes. Quinoa ﬂour improved the technological properties of bread by gradually increasing the viscosity due to higher amount of soluble dietary ﬁber content compared to buckwheat ﬂour. This would compensate the structure loss associated to lack of gluten. It may be concluded from the present study that, 25% quinoa ﬂour formulation can successfully be incorporated into commercial gluten-free bread formulations without creating any negative effect on sensory properties; although the level of quinoa ﬂour may be reassessed according to preferences of people with celiac disease in future studies. Acknowledgments an for her help in The authors acknowledge Neslihan Bozdog dietary ﬁber analysis. This research was funded by Ege University Scientiﬁc Project Commision with project no: 14-MUH-013. References AACC, 2010. Approved Methods of the AACC. Methods 46-12.01, 56e11. American Association of Cereal Chemists, St. Paul, MN, 10e05.1. Alvarez-Jubete, L., Auty, M., Arendt, E.K., Gallagher, E., 2010. Baking properties and microstructure of pseudocereal ﬂours in gluten-free bread formulations. Eur. Food Res. Technol. 230, 437e445. AOAC, 1998. AOAC Ofﬁcial Methods of Analysis. Method 991.43, Total, Soluble, and Insoluble Dietary Fiber in Foods. Association of Ofﬁcial Analytical Chemists International, Gaithersburg, Maryland. _ lu, S¸., 2015. Effect of pseudo cereal ﬂours on some physical, Bilgiçli, N., Ibano g chemical and sensory properties of bread. J. Food Sci. Technol. 1e5. ^as, J.A.G., 2014. Novel approaches in gluten-free breadmaking: Capriles, V.D., Are interface between food science, nutrition, and health. Compr. Rev. Food Sci. F. 13 (5), 871e890. Delcour, J.A., Hoseney, R.C., 2010. Yeast-leavened Products. In: Delcour, J.A., Hoseney, R.C. (Eds.), Principles of Cereal Science and Technology. AACC International, St. Paul, pp. 177e206. Demirkesen, I., Mert, B., Sumnu, G., Sahin, S., 2010a. Rheological properties of gluten-free bread formulations. J. Food Eng. 96, 295e303. Demirkesen, I., Mert, B., Sumnu, G., Sahin, S., 2010b. Utilization of chestnut ﬂour in gluten-free bread formulations. J. Food Eng. 101, 329e336. Fleming, S.E., Sosulski, F.W., 1978. Microscopic evaluation of bread fortiﬁed with concentrated plant proteins. Cereal Chem. 55 (3), 373e382. €ste, M., Nordlohne, S.D., Elgeti, D., Linden, M.H., Heinz, V., Jekle, M., Becker, T., Fo 2014. Impact of quinoa bran on gluten-free dough and bread characteristics. Eur. Food Res. Technol. 239 (5), 767e775. Giannou, V., Tzia, C., 2007. Frozen dough bread: quality and textural behavior during prolonged storageeprediction of ﬁnal product characteristics. J. Food Eng. 79 (3), 929e934.
n, M.E., Raskin, I., Graf, B.L., Rojas-Silva, P., Rojo, L.E., Delatorre-Herrera, J., Baldeo 2015. Innovations in health value and functional food development of quinoa (Chenopodium quinoa Willd.). Compr. Rev. Food Sci. F. 14 (4), 431e445. Hager, A.S., 2013. Cereal Products for Speciﬁc Dietary Requirements. Evaluation and Improvement of Technological and Nutritional Properties of Gluten Free Raw Materials and End Products. PhD Thesis. University College Cork, Ireland. recka, D., Drozd _ zy _ n ska, A., Gujska, E., 2014. Effect of boiling He˛ s, M., Dziedzic, K., Go in water of barley and buckwheat groats on the antioxidant properties and dietary ﬁber composition. Plant Foods Hum. Nutr. 69 (3), 276e282. ICC- International Association for Cereal Science and Technology, 1996. Methods: 104/1, 110/1 (Vienna). Iglesias-Puig, E., Monedero, V., Haros, M., 2015. Bread with whole quinoa ﬂour and biﬁdobacterial phytases increases dietary mineral intake and bioavailability. LWT-Food Sci. Technol. 60 (1), 71e77. der, I., Ada nyi, N., Daood, H.G., Sass-Kiss, A., Kardos-Neumann, A., 2010. Study of Le the composition and radical scavenging capacity of buckwheat seed and buckwheat leaf ﬂour of two cultivars grown in Hungary. Eur. Plant Sci. Biotechnol. 2, 87e92. Lin, L.Y., Hsieh, Y.J., Liu, H.M., Lee, C.C., 2008. Flavor components in buckwheat bread. J. Food Process. Pres. 33, 814e826. Ogungbenle, H.N., 2003. Nutritional evaluation and functional properties of quinoa (Chenopodium quinoa) ﬂour. Int. J. Food Sci. Nutr. 54 (2), 153e158. Pruska-Kedzior, A., Kedzior, Z., Goracy, M., Pietrowska, K., Przybylska, A., Spychalska, K., 2008. Comparison of rheological, fermentative and baking properties of gluten-free dough formulations. Eur. Food Res. Technol. 227, 1523e1536. Repo-Carrasco-Valencia, R.A.M., Serna, L.A., 2011. Quinoa (Chenopodium quinoa, Willd.) as a source of dietary ﬁber and other functional components. Cienc. Tecnol. Aliment. 31 (1), 225e230. Campinas. Ruales, J., Nair, B.M., 1994. Properties of starch and dietary ﬁbre in raw and processed quinoa (Chenopodium quinoa, Willd) seeds. Plant Foods Hum. Nutr. 45 (3), 223e246. Sabanis, D., Tzia, C., 2011. Effect of hydrocolloids on selected properties of glutenfree dough and bread. Food Sci. Technol. Int. 17 (4), 279e291. Schlick, G., Bubenheim, D.L., 1993. Quinoa: an emerging “new” crop with potential for CELSS. In: NASA Technical Paper. 3422. Stikic, R., Glamoclija, D., Demin, M., Vucelic-Radovic, B., Jovanovic, Z., MilojkovicOpsenica, D., Jacobsen, S.R., Milovanovic, M., 2012. Agronomical and nutritional evaluation of quinoa seeds (Chenopodium quinoa Willd.) as an ingredient in bread formulations. J. Cereal Sci. 55 (2), 132e138. € mo € sko € zi, S., Gyenge, L., Pelce der, A., Abonyi, T., Scho € nlechner, R., 2011. Effects of To ﬂour and protein preparations from amaranth and quinoa seeds on the rheological properties of wheat-ﬂour dough and bread crumb. Czech J. Food Sci. 29 (2), 109e116. Torbica, A., HadnaCev, M., Dap cevi c, T., 2010. Rheological, textural and sensory properties of gluten-free bread formulations based on rice and buckwheat ﬂour. Food Hydrocolloid 24, 626e632. USDA- United States Department of Agriculture, 2014. National Nutrient Database for Standard Reference Release, 27, p. 20035 (Quinoa- uncooked, and Buckwheat). Wronkowska, M., Christa, K., Ciska, E., Soral-Smietana, M., 2015. Chemical characteristics and sensory evaluation of raw and roasted buckwheat groats fermented by Rhizopus Oligosporus. J. Food Qual. 38 (2), 130e138. Wronkowska, M., Haros, M., Soral-Smietana, M., 2013. Effect of starch substitution by buckwheat ﬂour on gluten-free bread quality. Food Bioprocess Technol. 6, 1820e1827.