PaPer Ital. J. Food Sci., vol. 27 - 2015 495 - Keywords: buckwheat; biscuit; dough; storage; texture - Impact of buckwheat flour granulatIon and supplementatIon level on the qualIty of composIte wheat/buckwheat gInger-nut-type bIscuIts b. fIlIpčev*, o. ŠImurIna and m. bodroža-solarov Institute of Food Technology, University of Novi Sad, Bul. cara Lazara 1, 21000 Novi Sad, Serbia *Corresponding author: Tel. +381 21 485 3778, email: bojana.filipcev@fins.uns.ac.rs AbstrAct Effects of gradual wheat flour substitution with buckwheat flour in ginger-nut biscuit formula- tion were investigated regarding dough characteristics, physical and textural characteristics of fi- nal product assessed after baking and 30 days of storage. buckwheat flour was added at 30, 40, 50% levels and two granulations (fine and coarse). Addition of buckwheat flour significantly in- creased dough hardness and decreased adhesiveness. spread significantly increased in biscuits with 40% and 50% of coarse buckwheat flour. biscuits containing coarse flour were harder and more fracturable than the control, whereas those with fine flour tended to be softer and less frac- turable. textural properties were significantly correlated to protein stability to heat and retrogra- dation tendency of starch in biscuit dough as well as moisture content. mailto:bojana.filipcev@fins.uns.ac.rs 496 Ital. J. Food Sci., vol. 27 - 2015 IntroductIon Ginger-nut biscuit (Gnb) is a sweet biscuit containing honey and aromatic spices (cin- namon, ginger, cloves), which is very popular globally. by this term, variety of sweet biscuit types are described. they may range from thin (less than 3 mm thick), crisp varieties with smooth surfaces to thicker (over 3 mm thick), smaller in diameter and softer varieties with prominent cracks on top surface. the large variation in ingredients and their proportions contributed to a wide range of biscuit types. For example, the finest quality nürnberg Leb- kuchen does not even contain flour but nuts and candid fruits deposited on thin wafer base whereas the Polish Pierniki Toruńskie is made from the highest quality flour. the similar feature in all of them is that they all contain honey and spices. In serbia, ginger-nut bis- cuits are traditionally produced by artisans, although their production has been indus- trialized (GAVrILoVIĆ, 2003). In appearance, they mostly resemble the gingersnaps from the united states: usually circularly shaped, over 6 mm thick with cracks on the top sur- face and soft crumb. Formulations of Gnb typically include 35- 50% honey, 28-32% sugar, 0-5% fat on a flour weight basis (GAVrILoVIĆ, 2003), whereas the levels of major ingredients in common sweet biscuits are 30-75% sugar, 15-50% fat and 7-20% water (MAnLEY, 2000). According to PY- LEr (1998), basic ratios of flour, fat and sug- ar in cookies vary from 100:30:30; 100:50:50 to 100:50:variable depending on processing type but may considerably deviate. Gnb flour can be specified as a wheat flour with good bread-making performance (quality group b, peak amylogram value 300 b.u.), preferably of higher extractions (ash contents 0.8-1.15% d.b.) due to higher protein, hydrocolloid and enzyme content as opposed to the quality re- quirements in common biscuit production. the flour in common biscuits is usually soft wheat flour with lower protein content and moisture absorption and ash contents 0.34-0.38% d.b. (PYLEr, 1998) and weak gluten (PArEYt and dELcour, 2008). In contrast to common bis- cuits whose final moisture content is low and ranges between 1-5% (cHEVALLIEr et al., 2000, 2002), the lowest recommended moisture con- tent in Gnb is 7% (GAVrILoVIĆ, 2003). below this value, the quality deteriorates due to in- creased hardness, fracturability and crum- bling. the crumb of Gnb is porous with dens- er or looser pore structure, soft and elastic. Its upper surface is cracked which is a com- mon pattern with formulations high in sugar and low in fat and is attributed to sugar re- crystallization on the surface area (PArEYt et al., 2009). Gnb is traditionally perceived as healthi- er in relation to other types of sweet biscuits probably because they contain honey and low amount of fat. As such, they can be seen as a convenient medium for providing further im- provement in nutritional value and functional- ity by replacing a part of wheat flour with oth- er nutritionally more valuable cereal or non- cereal flour. one such ingredient having an excellent reputation for its nutritious quali- ty and abundance in bioactive compounds is common buckwheat. buckwheat is most com- monly used for producing flour and groats. While groats are mainly used for porridge and in various ethnic dishes, buckwheat flour is used as an ingredient in a variety of baked, cooked and extruded products: breads made from wheat-buckwheat flour blends at differ- ent ingredient proportions, flat bread, pas- ta (pizzoccheri in Italy), noodles (soba in Ja- pan, extruded noodles in china and Korea), pancakes, breakfast cereals (based on extru- dates made from buckwheat, rice, and/or corn blends), and biscuits (buckwheat added at 20- 30% wheat flour basis). results from previous studies (FILIPČEV et al., 2012) revealed that buckwheat flour has a po- tential as an ingredient in Gnb formulation but a main disadvantage was related to the coarse granulation of commercially available buck- wheat flour which reflected gritty texture of the final product. therefore, this study was conduct- ed to investigate the effect of substitution level and granulation of wholegrain buckwheat flour on dough characteristics and Gnb physical and textural characteristics. the effects of three sub- stitution levels (30%, 40%, 50%) and two flour granulation sizes (fine (FbF) and coarse (cbF)) were studied. MAtErIALs And MEtHods Materials commercially available wheat flour (WF) type 850 (ash content 0.81% dry basis, moisture con- tent 12.53%), and wholegrain buckwheat flour (ash 2.20% d. b., moisture content 12.31%) were used in the experiment. other ingredients hon- ey, vegetable fat (from sunflower), sugar, naH- co 3 , lecithin and spice (cinnamon) were obtained from a local food store (novi sad, serbia). the purchased buckwheat flour was coarsely gran- ulated. to obtain finer granulation, it was re- milled on a Falling number 3100 mill (Perten Instruments). the granulation of used flours is given in table 1. Water absorption capacity of flours Flour sample (5 g) was mixed with an excess of distilled water (25 ml), kept at ambient tem- perature for 30 min and then centrifuged at Ital. J. Food Sci., vol. 27 - 2015 497 2000 x g for 15 min. Water absorption capaci- ty was expressed as g of water bound by 100 g of dry matter. Syneresis degree of wheat and buckwheat flours the method described by sInGH et al. (2003) was used. Flour suspensions (6 % w/v) were heated in a water bath to 90°c and held 20 min at this temperature. cooled flour paste (30 mg) was poured into a centrifuge tube. the tubes were stored for 1 and 10 days at 4°c. syneresis was measured as % of water expelled after cen- trifugation of sample. Biscuit making Gnb was prepared by substituting wheat flour with buckwheat (0, 30, 40, 50 %). Formu- lae are found in table 2. Firstly, a basic dough was formed by warming a mixture of honey, sugar and water to 80°c and adding part of the flour (75% of total) to a hot mixture. the mix- ture was mixed to obtain a thick, homogenous mass. After cooling to 40°c, basic dough was sprinkled over with flour, covered with a plas- tic foil, and left to rest at ambient temperature for two days. other ingredients (remaining flour amount, spices, raising agents dissolved in wa- ter, fat and lecithin) were added and mixed us- ing a kitchen mixer with a spiral hook for 10 min. the amount of added water was adjusted table 1 - Particle size distribution of used flours. Particle size Wheat flour Coarse buckwheat Fine buckwheat (weight %) (WF) flour (CBF) flour (FBF) >350 mm 0.00 55.30 5.74 >250 mm 0.02 9.40 11.32 >180 mm 0.40 4.76 11.11 >150 mm 1.32 3.80 8.90 >105 mm 22.54 10.14 18.86 >85 mm 26.85 9.80 30.76 bottom 48.87 6.80 13.31 table 2 - Ginger nut biscuits formulations. Ingredients, g Control Biscuit supplemented Biscuit supplemented with CBFa with FBFa Wheat flour 100 70 60 50 70 60 50 Buckwheat flour 0 30 40 50 30 40 50 Honey 50 50 50 Sugar 10 10 10 Vegetable fat 5 5 5 NaHCO 3 2.1 2.1 2.1 Spice blend 2 2 2 Lecithin 1 1 1 Water 20 18 17 16 20 21 22 a CBF-coarse buckwheat flour; FBF-fine buckwheat flour to obtain a maximally soft dough with accepta- ble handling characteristics. the consistency of dough was evaluated subjectively by an expe- rienced baker. dough moisture content ranged between 17.8-21.7%. After mixing, the dough was sheeted on a pastry break to 10-mm thick- ness (sfogliatrice Mignon, Maestrino, Pd, Italy). the dough was cut to a diameter of 60 mm and baked for 15 min in a deck oven at 170°c. Af- ter 1 hour of cooling at room temperature, the biscuits were packed in polyethylene bags and stored at room temperature. Texture profile analysis of biscuit dough dough characteristics were evaluated us- ing a texture analyzer (tA.XtPlus stable Micro systems Ltd., surrey, uK) equipped with a 30- kg load cell. texture Profile Analysis (tPA) was employed to measure dough properties as de- scribed by (GALLAGHEr et al., 2005). doughs were prepared as for the baking test and cut into round pieces (60 mm). A 36-mm cylindrical aluminium probe was used in two compression cycles at test speed 1.0 mm/s. Pre and post- test speeds were 2.0 mm/s. the force was meas- ured at 45% compression. the recovery peri- od between the strokes was 5 s. the following 4 parameters were recorded: hardness, adhe- siveness, cohesiveness and springiness. seven measurements per each biscuit type were made. Measurements were performed on dough after the resting period. 498 Ital. J. Food Sci., vol. 27 - 2015 Analysis of thermo-mechanical properties of biscuit dough by Mixolab Mixing and pasting properties of the ginger nut biscuit doughs were studied on Mixolab (chopin, tripette and renaud, Paris, France). this device measures in real time the torque produced by dough during mixing at conditions of controlled temperature regime which include dough heating to 90°c, maintenance at constant temperature and dough cooling to 50°c. In this way, the behaviour of both proteins and starch under dual mechanical shear stress and tem- perature constraint can be measured (rosELL et al., 2006). usually, individual flours or flour blend slurries are analysed in this way. In our study, previously prepared Gnb dough was sub- jected to analysis using a modified Mixolab pro- tocol. For the assays, 80 g of dough was insert- ed to Mixolab bowl, followed by the next regime: mixing speed 80 rpm, tank temperature: 30°c, 1st plateau temperature 30°c, duration of first plateau 5 min, heating rate 4.0°c/min, 2nd pla- teau temperature 90°c, duration of 2nd plateau 7 min, cooling rate 4.0°c/min, 3 rd plateau tem- perature 50 °c, duration of 3rd plateau 5 min. Main derived parameters from the Mixolab curves are: development (c1) or maximum torque reached during mixing at 30°c, protein weakening (c2) or the minimum torque produced as a consequence of heating and mechanical stress, maximal torque (c3) produced during the heating stage as a consequence of starch gelati- nization, minimal torque at the stage of cooling (c4) and the torque after cooling at 50°c (c5). Measurements were replicated twice for each biscuit dough type after the resting period. Textural analysis of ginger nut biscuits Hardness and fracture of Gnb were measured 24 h post-bake by penetration test on tA.XtPlus texture Analyzer (stable Micro systems, England, uK). the test mode was force in compression. A 5 kg load cell was used. the sample was placed on the platform with a holed plate and centrally punctured with a 2 mm cylinder probe through the sample at test-speed 0.5 mm/s. Hardness of the sample was calculated from the area under the curve whereas fracturability was calculated from the linear distance. Four biscuits from each treatment were punctured five times in an ‘X’ pat- tern avoiding the outer 1 cm to prevent from edge effects. Biscuit dimensions and density diameter (width) and height (thickness) of biscuits were measured using a vernier calli- per. diameter was calculated as an average of long and short diameter. spread was calculat- ed from the ratio of width and height. For the measurements, twelve randomly chosen biscuits were taken. density was calculated as a ratio of biscuit mass and volume. since biscuits had a regular shape, their volume was approximated to the volume of cylinder according to formula V=p*(r/2)2*h where h is biscuit height and r is average biscuit diameter. Moisture content Moisture was calculated according to AoAc Method 926.5 (2000). two composite samples of each biscuit type were analyzed in duplicates. the composite samples were prepared by ho- mogenization of six individual biscuit samples. Statistical analysis An analysis of variance (AnoVA) of data was performed by using a statistica 7.1 statistical software package (statsoft Inc., tulsa, oklaho- ma). tukey’s post-hoc test was used to compare the means at 95% confidence interval. correla- tion analysis was conducted using spearman’s rank correlation coefficient applied to mean val- ues for each biscuit. rEsuLts And dIscussIon Water absorption capacity (WAC) and syneresis degree of used flours buckwheat flour showed higher WAc in com- parison to WF (table 3). this might be due to various reasons: higher hydration capacity of buckwheat starch in comparison to wheat starch (QIAn et al., 1998); presence of other hy- drophilic constituents in the wholegrain buck- table 3 - Water absorption capacity (WAc) and syneresis (%) of wheat and buckwheat flour. Flour WAC (g/100 g dry matter) Syneresis (%) 1 day 10 days Wheat flour 63.96a 9.27a 14.57a Buckwheat flour, coarse 101.10b 39.27b 46.86c Buckwheat flour, fine 104.14b 40.20b 42.67b a,b,c Figures followed by the same letters in a column are not significant- ly different (p>0.05). wheat flour (fibers). In contrast, bALJEEt et al. (2010) reported that buckwheat flour had low- er WAc, higher oil absorption capacity, high- er foaming capacity and higher least gelation concentration than wheat. WAc of FbF in- creased but not significantly in comparison to cbF which might be explained by the fact that milling does not tend to increase the amount of damaged starch in buckwheat. It has been shown by QIAn and co-workers (1998) that Ital. J. Food Sci., vol. 27 - 2015 499 buckwheat flour has lower amounts of dam- aged starch than wheat. the syneresis value (%) of cooked pastes from wheat and buckwheat flour significantly differed. WF showed much less syneresis than buckwheat. during storage, syneresis of the pastes increased. the highest syneresis was observed in the paste made from cbF (46.9%), followed by FbF (42.7%). the retrogradation properties of the flours are generally attributed to composition, ratio and interactions of flour constituents: proteins, starch, lipids, fibers. GNB dough characteristics the addition of buckwheat significantly in- creased dough hardness in comparison to the control (p<0.05) (Fig.1). the dough hardness in- creased remarkably in the case of finely ground buckwheat flour. tPA adhesiveness showed a de- clining trend which was significant in comparison to the control. dough springiness and cohesive- ness also tended to decline with increased propor- tion of buckwheat, but there were no significant differences between the samples. FbF increased dough cohesiveness in comparison to cbF. Fig. 1 - dough hardness, adhesiveness, cohesiveness and springiness for different formulations of Gnb. a,b,c ,… A, b,… Values followed by same letters of the same case are not significantly different (p>0.05). these effects can be related to the particular- ities of buckwheat flour and flour particle size. buckwheat is characterized by resistant starch, which may contribute to low viscoelastic proper- ties of dough and increased hardening (QIAn et al., 1998; dE FrAncIscHI et al., 1994; LI et al., 1997; QIAn and KuHn, 1999; YosHIMoto et al., 2004; HAtcHEr et al., 2008). the observed variations in dough hardness and adhesiveness were mainly due to the effect of buckwheat flour granularity. Even though WAc between FbF and cbF did not significantly differ, it seems that fin- er flour particles were able to absorb more water during mixing, thereby forming more cohesive and harder dough. Lowering of dough adhesive- ness and cohesiveness as a consequence of in- creasing amounts of coarse wheat flour was re- ported earlier (sInGH GurJAL et al. 2003). this coincides with our findings. Furthermore, dough made with wholegrain buckwheat flour was re- ported to have lower adhesiveness in compari- son to the majority of other buckwheat flour frac- tions (IKEdA and KIsHIdA, 1992). Parameters related to thermo-mechanical be- haviour of Gnb dough made with coarse and fine buckwheat flour is given in table 4. buck- table 4 - dough mixolab parameters for different formulations of gnb (cbF-coarse buckwheat flour; FbF-fine buckwheat flour). Sample C1 C2 C3 C4 C5 C1-C2 C5-C4 (Nm) (Nm) (Nm) (Nm) (Nm) (Nm) (Nm) Control 3.45a 2.73e 3.04f 1.65e 1.66b 0.72a 0.005a CBF 30% 3.99b,c 1.20d 1.40c 1.39c 2.71e 2.79c 1.32d 40% 4.31c 0.86c 1.53c 1.54d 2.24d 3.45e 0.70b 50% 3.68a,b 0.68a 1.81d 1.62e 2.69e 3.00d 1.06c FBF 30% 4.22c 1.30d 1.30b 0.97b 1.85c 2.92d 0.88c 40% 4.19c 0.75b 2.00e 0.91b 1.52b 3.44e 0.61b 50% 5.32d 0.85c 1.10a 0.63a 0.95a 4.47e 0.32b a,b,c ,… Figures followed by the same letters in a column are not significantly different (p>0.05). 500 Ital. J. Food Sci., vol. 27 - 2015 wheat supplemented dough was characterized with higher maximal torque during mixing (c1) and lower resistance to thermal and mechanical stresses (low c2 and high c1-c2) than the con- trol dough. these effects seem to be more pro- nounced in the case of dough supplemented with coarse buckwheat flour. both buckwheat flours affected these parameters in a similar way. this behaviour is probably due to dilution of gluten by addition of non-glutenous buckwheat flour which contributed to the formation of weak- er protein network. the control dough showed higher maximal peak during heating (c3) than the buckwheat supplemented doughs. the de- crease in peak viscosity of the buckwheat sup- plemented doughs may be attributed to lower swelling of starch granules and poorer gelatini- zation which is probably due to native charac- teristics of buckwheat starch and limited water amount in Gnb doughs. similar results were reported by HAdnAĐEV and co-workers (2008), even in systems with higher moisture con- tent, resembling bread dough. the buckwheat doughs exhibited lower breakdown torque (c4) which indicates lower stability of warm gel. Final torque (c5) and total setback values (c5-c4) are parameters used to characterize starch retrogra- dation that occurs during cooling to 50°c. Final torque (c5) was lower in the control dough and dough made with fine buckwheat flour. the total setback was the lowest in the control dough fol- lowed by FbF dough. Hence, regarding the ability to resist retrogradation, the tested Gnb doughs follow the order: wheat dough > fine buckwheat flour dough > coarse buckwheat flour dough. Biscuit dimension, density and spread data related to the biscuit dimension and density is displayed in Fig. 2. Majority of the variables showed significant differences as compared to the control especially at higher replacement levels (40% and 50%). the height and diameter decreased with increasing levels of both FbF and cbF. despite general shrink- age, the interrelation between both dimensions was such that spread increased significantly at 40% and 50% of cbF addition whereas in other cases, spread did not significantly vary from the control. there was a strong inverse correlation between spread and height (r=-0.84, p<0.01) showing that reduction in height dominant- ly affected spread whereas spread and diam- eter were not significantly correlated (r=-0.17, p>0.01). the spread of the biscuit during bak- ing is caused by expansion of dough by leaven- ing and gravitational flow (HosEnEY and roG- Ers, 1994). It depends on factors that control dough viscosity: the amount of water free to act as solvent and the strength of dough (rAM and sInGH, 2004). It also depends on partitioning of available water between the ingredients. the lesser the amount of water held by ingredients, the more the amount of water is available to dis- solve sugar, decrease dough viscosity and in- crease spread (PArEYt and dELcour, 2008). coarse flour has been reported to contribute to greater spread (sInGH GurJAL et al., 2003; MAnLEY, 1991). substitution of wheat flour with a finely ground light and dark buckwheat flour (granulation size 100-150 mm) in sugar- snap cookie formulations lowered the cookie spread (MAEdA et al., 2004). It was also found that buckwheat flour of similar granulation dosed at 10-40% level (flour basis) decreased the spread in sugar snap cookies (bALJEEt et al., 2010). results obtained in this study con- firmed the relation between spread and flour granularity: in relation to the control, the addi- tion of cbF increased the spread. Higher biscuit spread is considered advantageous in biscuit making (PArEYt and dELcour, 2008). but, in contrast to majority of biscuits, the main qual- ity requirement for Gnb is well developed and soft crumb (GAVrILoVIĆ, 2003). therefore, high spread may not be necessarily considered as preferable in Gnb making since the increased thickness (height) is needed to develop a po- rous and soft crumb. regarding biscuit density, a general trend was Fig. 2 - Effect of Gnb formulation on biscuit dimensions (height, diameter, spread) and density. a,b,c ,… A, b,… Values followed by same letters of the same case are not significantly different (p>0.05). Ital. J. Food Sci., vol. 27 - 2015 501 Fig. 4 - Effect of Gnb formulation on biscuit hardness and fracturability measured after 24 h and 30 days. a,b,c ,… A, b,… Values followed by same letters of the same case are not significantly different (p>0.05). that density increased in the combined formu- lations. there was a strong inverse correlation between the biscuit dimensions and density r=- 0.97 (p<0.01) and -0.76 (p>0.05) for height and diameter, respectively, confirming that higher density reduces biscuit development. Biscuit moisture content Minimal moisture content required for the retention of freshness in Gnb is 7%. Moisture contents below this value render biscuits unac- ceptable owing to their increased tendency to dry out during storage. the moisture content of biscuits was significantly affected by the level of flour substitution with buckwheat flour as well as its granulation: increased buckwheat doses and coarse flour tended to decrease it whereas FbF increased the moisture content (Fig. 3). As a result, the composite biscuits with 40% and 50% of cbF were significantly lower in moisture (8.00-8.50%, p<0.05, respectively). other for- mulations had higher moisture contents with the highest registered in Gnb made with FbF and the control (≥ 10.0% moisture content). the water content in Gnb formula was significantly correlated to biscuit hardness (r=-0.84, p<0.01), dough cohesiveness (r=0.84, p<0.01) and c5 (r=- 0.92, p<0.01). these results indicate that higher moisture content is advantageous in this catego- ry of biscuits as it contributes to softer texture, more cohesive and stable dough. over time, a decrease in moisture contents was observed in all samples. the most marked moisture content decrease (by 8%-10.7%, p<0.05) were in the bis- cuits substituted with FbF and much less in oth- er samples (by 2.6%-3.8%), in spite of the lower syneresis degree of FbF. Although subjected to the high moisture loss, these biscuits remained higher in moisture content than the control due to higher initial moisture. during storage, mois- ture migration and evaporation occurs because gluten and starch undergoes such transforma- tions which result in water release (WILLHoFt, 1971; sEntI and dIMLEr, 1960). Biscuit texture characteristics Granulation of buckwheat flour affected hard- ness and fracturability of Gnb. In general, two trends were observed: as the level of cbF in- creased, hardness also increased, whereas the addition of FbF decreased hardness (Fig. 4). However, the produced results were similar to the control except in the case of Gnb made with 50% cbF, which produced significantly higher hardness. Fracturability showed a similar trend (Fig. 4). bALJEEt and others (2010) said that the addition of finely ground buckwheat flour decreased the hardness of composite biscuits. Increased hardness has been usually relat- ed to increased association of wheat proteins as correlated by GAInEs (1990) in sugar snap cookies and HAtcHEr et al. (2008) in the buck- wheat supplemented soba noodles. In contrast to common biscuits, good quality wheat flour is required in the production of ginger nut bis- cuits. consequently, its texture is related to the quality of flour proteins with the ability to pro- vide unique viscoelastic and network-forming properties. the results of this study showed a significant correlation (r=0.74, p<0.05) between the biscuit hardness and a Mixolab parameter Fig. 3 - Effect of Gnb formulation and storage time on bis- cuit moisture content. a,b,c ,… A, b,… Values followed by same letters of the same case are not significantly different (p>0.05). 502 Ital. J. Food Sci., vol. 27 - 2015 related to the quality of proteins, c1-c2. As already noted, c1-c2 indicates protein weak- ening during heating: higher difference means increased protein weakening i.e. lower stabil- ity to heat. GAVrILoVIĆ (2003) suggested that Gnb hard- ness is also affected by starch pasting properties. In this study, significant correlation (r=0.84 and 0.81, p<0.01) was found only between hardness and Mixolab parameters which indicates starch gel retrogradation (c5 and c5-c4 (total setback), respectively) i.e. higher biscuit hardness can be related to higher setback and c5 values which are indicators of higher susceptibility to staling. the ability of the buckwheat starch to increase hardness of Gnb can be counteracted by us- ing ingredients able to retain more water (such as an observed decreasing trend for hardness in the biscuits made with FbF (Fig. 4)). Actual- ly, it was found that the moisture content sig- nificantly affected biscuit hardness; there was a significant inverse correlation between hardness and formula water content i.e. biscuit moisture content (r=-0.84 (p<0.01) and -0.74 (p<0.05), respectively). According to GAVrILoVIĆ (2003), fracturability of Gnb can be related to the presence of partially dehydrated gluten in the dough matrix. cHArLEs and co-workers (2004) proposed that the pres- ence of discontinuous phase in gluten network was related to an increase in fracturability in flaky snack. Here in the study, significant cor- relation was found between the biscuit fractura- bility and two Mixolab parameters related to the behaviour of protein during heating (c2 and c1- c2): c2 denotes the minimum torque produced during heating as a consequence of the begin- ning of protein weakening (r=-0.84, p<0.01) and c1-c2 can be associated with protein stability (r=0.95, p<0.01). Lower value of c2 and higher value for c1-c2 indicate lower protein stability. In other words, increasing fracturability of Gnb can be related to all such factors that may low- er the protein stability or discontinue the glu- ten network such as the addition non-gluten in- gredient like buckwheat, especially in the form of coarse flour. there was also a significant cor- relation between biscuit fracturability and set- back value (c5-c4) (r=0.78, p<0.05 ). over the 30-day trial period, a significant in- crease in hardness and fracturability occurred for Gnb made with FbF whereas all others showed insignificant increases as related to the initial values (Fig. 4). but, there were no signif- icant differences in hardness and fracturabili- ty within all biscuits measured after 30 days of storage. on the basis of the above mentioned high correlation between the texture and Mixolab parameters that indicate starch susceptibili- ty toward retrogradation, it could be thought that the lower the susceptibility of starch in biscuit dough to retrograde, the lower the bis- cuit hardness, fracturability and presumably its tendency towards staling. but, the results obtained after storage showed that Gnb made with FbF, which initially gave the softest bis- cuit and which paste had lower syneresis de- gree, significantly increased in hardness (in re- lation to the initial values). this could be due to higher moisture evaporation and more compact structure in comparison to the granular struc- ture of Gnb made with cbF. It is also worth noting that Gnb dough represents a low-mois- ture system containing up to 25% moisture and, in addition, interfering ingredients like sugar and fat which might have caused different be- haviour and tendencies regarding starch past- ing. Interestingly, dough hardness was strongly positively correlated with biscuit hardness and fracturability after storage (r=0.84 and r=0.81, p<0.01). In the literature, there is little data on the functional properties of buckwheat flour; more data exist on buckwheat starch. Furthermore, data on the ability of buckwheat starch to ret- rograde are rather contrasting. In the study of QIAn and colleagues (1998), besides increased hardness and stability, buckwheat starch gels exhibited lowered retrogradation as compared to cereal starches, even after storage. Lower susceptibility to retrogradation was also sug- gested in reports on thermomechanical proper- ties of buckwheat flour slurries or wheat/buck- wheat blends slurries (chopin’s Mixolab user’s Manual 2005, bAnu et al., 2010). In another study, however, a stronger retrogradation peak was observed in buckwheat thermogram than that in wheat (LIu et al., 2006). ZHEnG and as- sociates (1998) reported that buckwheat starch had a higher peak viscosity and setback value than maize and wheat starches which may sug- gest higher retrogradation tendencies in buck- wheat starch since setback viscosity indicates the degree of starch retrogradation, mainly its amylase fraction. starch pasting properties de- pend on the hydration level (ZHou et al., 2009). It was concluded that buckwheat starch gelati- nization temperatures and enthalpies increased along with the decrease of water content, which can be associated with an increased retrograda- tion tendency. Moreover, there is little data to relate starch pasting behaviour with the final properties in a biscuit-like products. It was reported that the addition of corn flour produced harder cookies than did the addition of potato flour, although corn flour had been shown to give lower syner- esis (retrogradation) than potato flour (sInGH et al., 2003). some authors did not find any correlation between pasting properties of bat- ters and characteristics of layer cakes (GÓMEZ et al., 2010). others suggested that dehulled buckwheat flour, although showing a tenden- cy to retrograde, can be used in buckwheat enriched products (MArIottI et al., 2008). In- Ital. J. Food Sci., vol. 27 - 2015 503 GLEtt and his team (2009) proposed that only specialty buckwheat flour with low paste vis- cosity is suitable for mixing with wheat flour to produce bread and cookies. Much earlier, Lor- EnZ and dILsAVEr (1982) mentioned that in- clusion of native buckwheat starches in cake formulations did not produce cakes of accept- able quality. concLusIons the results indicated that the addition of buckwheat significantly increased dough hard- ness and decreased dough adhesiveness. spring- iness and cohesiveness of buckwheat doughs were reduced but no significant difference with- in the samples was observed. the dimensions of Gnb decreased, but since the biscuit height was more affected by the ris- ing doses of buckwheat, the spread increased in the composite biscuits (significant difference was noted with cbF at 40% and 50% replace- ment level). Hardness and fracturability of Gnb increased with increasing doses of cbF where- as FbF decreased hardness and fracturability. However, a significant change was noted only with the addition of 50% cbF. Hardness and fracturability of Gnb signif- icantly correlated to the quality of proteins; lower stability of proteins to heat was associ- ated to increased hardness and fracturabili- ty in Gnb. tendency of starch gel in biscuit dough to retrograde was found to be in signifi- cant positive correlation with biscuit hardness and fracturability, however, after 30 days of storage, hardness and fracturability increased most markedly in the biscuits made with FbF which were initially softer than the others. bis- cuit hardness was in significant inverse re- lation with the formula water content which might additionally support the importance of protein quality and starch pasting behaviour to the quality of Gnb. comparing Gnb and common biscuits made from short and semi-sweet dough from litera- ture, it seems that Gnb exhibits different be- haviour. better quality characteristics are ob- tained when more water is added to the dough and increased spread cannot be regarded as positive since well-developed crumb is more advantageous for better textural properties. the addition of FbF to Gnb formulation is appropriate at the investigated doses. 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