Dandelion Flowers as an Additive to Wheat Bread: Physical Properties of Dough and Bread Quality

: Dandelion ﬂowers (DF) are a rich source of many phytochemicals which can reduce oxidative stress in the human body. The aim of this study was to assess the inﬂuence of dried and powdered DF addition into wheat ﬂour (WF) on dough and bread properties. WF was replaced with DF at levels 0, 1, 2, 3, 4, 5 and 6%. Physical properties of dough and quality of control and supplemented bread were studied. The addition of DF increased water absorption of ﬂour, development time and dough stability during mixing. However, these changes had no positive effect on bread quality. With an increase in the proportion of DF in the bread recipe, the volume of loaves and lightness of crumb decreased while its hardness and yellowness increased. As a result of these changes, the overall sensory acceptability of DF-enriched bread decreased. On the other hand, supplementation of WF with DF increased minerals, ﬁber and fat content in bread. Most importantly, DF enhanced the antioxidant capacity of bread and increased content of phenolics. Total phenolic content ranged from 1.00 mg GAE/g dry mass (DM) for control bread to 3.45 mg GAE/g DM when wheat ﬂour was replaced with 6% of DF. To summarize, we showed that DF can be a valuable ingredient for bread fortiﬁcation. However, the amount of WF replaced with DF should not exceed 2–3% while taking into account the sensory results.


Introduction
Bread is a staple food product in the daily diet of most people.A large portion of bread is made from refined flour.Such bread is attractive to consumers due to its soft texture, light-colored crumb, crispy crust and easy digestibility [1].However, during the milling of wheat grain into white flour, many nutritionally valuable compounds such as vitamins, minerals, dietary fiber and other phytochemicals are lost, which means that bread made from such flour is energy-dense food but low in biologically active compounds, and consequently has limited ability to protect the human body from various diseases [2].For this reason, it is reasonable to enrich wheat flour (WF) with natural and compound additives that are rich in phenolics.Flours from nonbread cereals and pseudocereals [3,4], legumes [5], oilseeds [6,7], herbs and spices [8][9][10][11], fruits and vegetables in various forms, e.g., dried or extracts [12][13][14], are valuable additives to wheat bread.Dandelion (Taraxacum officinale F.H. Wigg) is a plant with an exceptionally valuable chemical composition.It occurs in Europe as a common weed [15].Dandelion contains protein, fiber, fat, phenolic compounds, flavonoids, terpenoids, glycosides and various vitamins and minerals, including ß-carotene, provitamin A, vitamins C and D, B vitamins, iron, silicon, magnesium, sodium, zinc, manganese, copper and phosphorus [16][17][18][19].In food production, various anatomical parts of this plant (roots, leaves and flowers) can be used as a rich source of many phytochemicals and minerals for human nutrition [17].Roots of Taraxacum officinale are a rich in inulin, a polysaccharide with probiotic properties, used for the microbiological production of fructose syrup [20].The roots are also used for the production of tea and, after roasting, as a coffee substitute [21].Root extracts can also be applied as a natural preservative, delaying oxidation in food products [22].Young leaves of dandelion are usually eaten raw as an ingredient in cocktails or salads, e.g., in combination with lettuce or chives.They can also be cooked and, after draining, eaten with butter and sprinkled with pepper and salt.Dried leaves are used to prepare various soft drinks and wine.Dandelion flowers (DF) can be used as an additive during production of wines and desserts, and their extracts are used as flavoring ingredients for various food products, e.g., dairy desserts, cheeses, candies and cookies [15].In earlier studies [23], we successfully used dried and powdered Taraxacum officinale roots as an additive to wheat bread.These are the first studies aimed at determining the possibility of using dried DF powder as an additive to bread.The specific objectives of this work were (i) to determine the physical properties of dough with the addition of DF and (ii) to study the influence of physicochemical and sensory properties of DF-enriched bread.

Materials and Methods
The experiment was performed according to the scheme presented in Figure 1.For WF, DF and obtained bread, the basic chemical composition was determined.Moreover, the physical properties of dough were determined using farinograph tests, and the physicochemical properties of bread were studied.

Raw Materials
The basic raw material for the preparation of bread dough was WF type 750 (Polskie Młyny Sp. z o.o., Warsaw, Poland), fresh pressed yeast (Lallemand Sp. z o.o., Józefów, Poland), table salt (Cenos Sp. z o.o., Września, Poland) and DF.Taraxacum officinale flowers came from experimental microplots of IUNG-PIB in Puławy (Poland).After harvesting, flowers were dried in the laboratory dryer (SL W 1000 TOP, POL-EKO Apparatus, Wodzisław Śl ąski, Poland) at 40 • C until they reached 10% moisture content and then powdered in the impact mill W Ż-1 (Baking Industry Research Institute, Bydgoszcz, Poland) to produce particles smaller than 0.3 mm.

Farinograph Properties of Dough
The blends of WF with DF were prepared before the determination of dough properties.The WF was replaced with DF at 0, 1, 2, 3, 4, 5 and 6%.The assay was performed using a Farinograph-E model 810114 with a mixer for 50 g flour (Brabender Gmbh & Co. KG, Duisburg, Germany) according to AACC Method 54-21 [24].The device cooperated with a computer equipped with Farinograph v.5 program (Brabender Gmbh & Co. KG, Duisburg, Germany) for the calculation of farinograph indices.

Bread Preparation
The direct method was used for dough preparation [7].The basic bread dough recipe included 500 g of WF, 15.0 g of yeast, 7.5 g of salt, and water.Water addition was calculated based on farinographic water absorption.WF was replaced with DF in the amount of 0% (CS), 1% (D1), 2% (D2), 3% (D3), 4% (D4), 5% (D5) and 6% (D6).The dough ingredients were mixed (SP-800A mixer, Spar Food Machinery, Taiwan) for 4 min at speed 2 and then transferred to a D-32 fermentation chamber (Sveba Dahlen, Sweden).The total fermentation time was 1.5 h, but after 60 min, the dough was mixed for 1 min.The fermented dough was divided into 250 g pieces, shaped by hand and placed in the molds for final proofing.Baking was carried out in a baking oven (DC-32E, Sveba Dahlen, Fristad, Sweden) at 230 • C for 30 min.After baking, the loaves were weighed and cooled before analysis.

Volume, Density and Yield of Bread
After 2 h of baking, the breads were weighed, their volume was determined, and crumb-specific weight and yield of bread were calculated [7].The volume was determined using a 3D scanner (NextEngine, West Los Angeles, CA, USA), calculated using a computer program (MeshlLab, ISTI-CNR Research Centre, Rome, Italy) and then converted into 100 g of bread.The density of the crumb was also calculated [25].

Texture of Crumb
Texture analyzer type TA.XT2i (Stable Microsystem, Surrey, UK) was used to assess the mechanical properties of the bread crumb according to Texture Profile Analysis (TPA).The assay was performed according to the methodology provided in [26].Cylindrical samples (diameter 22 mm) were cut from slices of bread 20 mm thick, which were subjected to compression testing using a head equipped with a mandrel with a diameter of 25 mm, with the speed of the mandrel at 1 mms −1 .A 40% penetration of the sample was used with a 45 s interval between the first and second compression.From the obtained curves, hardness, elasticity, springiness, cohesiveness, gumminess and chewiness were determined.

Color Coordinates
The color coordinates of the crumb were determined by the reflection method in the CIE-L*a*b* system, where L* means lightness, a* red/green saturation and b* yellow/blue saturation.A CR-200 colorimeter (Konica Minolta, Osaka, Japan) was used for evaluation.The total color difference (∆E) was calculated between the bread made of WF and the DF-enriched bread [27].

Total Phenolics Content (TPC) and Antioxidant Capacity (AC)
Methanolic extracts of WF, DF and bread samples were prepared before the determination of TPC and AC.TPC was determined using the method described in [28] and expressed as milligrams gallic acid equivalent (GAE) per gram of dry mass (DM).Antioxidant capacities against ABTS and DPPH radicals were determined [29].The results of AC were expressed as the EC 50 index (mg DM/mL).This index shows the concentration that induces a response halfway between the baseline and the maximum AC of a sample [30].

Sensory Evaluation
The sensory analyses of the bread samples were performed using a 9-point hedonic scale, with scores ranging from 1 (dislike extremely) to 9 (like extremely) [31].Bread samples were assessed by 46 panelists (25 women and 21 men between 21 and 56 years old) for appearance, color, smell, taste and texture.Consequently, the overall acceptability of tested bread samples was determined.Before the test, participants received information about the study's purpose and gave their consent in accordance with the university's ethics committee.The analysis was performed at 20 • C in a room with white lighting.

Statistical Analyses
At least three replicates of each test were performed.Statistica 13.3 software (TIBCO Software, Palo Alto, CA, USA) was used to perform a statistical evaluation of the data.Analysis of variance (ANOVA) was performed, and the Tukey test was used for the determination of significant differences between means (α = 0.05).

Basic Chemical Composition
WF contained 0.71% ash, 2.93% fiber, 12.86% protein, 1.73% fat and 81.77% available carbohydrates.When compared with WF, DF was richer in all components except carbohydrates; ash content, fiber content and fat content were several times higher than in WF.Consequently, minerals, total dietary fiber and fat content increased with the addition of DF in the bread samples, whereas available carbohydrates decreased (Table 1).The chemical composition of bread depends strongly on used additives.Recently, many papers have been published on the nutritional value of bread enriched with various unconventional additives [32][33][34].Odunlade et al. [35] found that partial replacement of WF with vegetable leaf powder from African eggplant, pumpkin and amaranths increases the protein, fiber, fat and ash content in enriched bread.Mafu et al. [36] incorporated cricket powder into wholemeal wheat bread.They showed that this additive can be used as a valuable source of protein in a bread recipe.A similar trend was observed when cricket powder was incorporated into gluten-free bread [37].Other authors [38] revealed that enriching wheat bread with dried and powdered grape pomace had no significant influence on protein content, but the fiber, ash and fat content was increased in enriched loaves.

Physical Properties of Dough
The farinograph is an often-used tool to assess the baking properties of WF.It records the physical properties of the dough such as resistance to deformation and changes in dough consistency during dough kneading.The farinograph properties of dough often show significant correlations with bread quality features and especially with bread crumb characteristics [39].The partial replacement of WF with DF changed all determined dough properties (Table 2).Flour water absorption linearly increased from 5.67% (CP) to 61.23% (D6) with an increase in DF in the dough (r = 0.989, p < 0.05).A similar relationship was found between the development time of the dough and the percentage of DF in the bread recipe (r = 0.943, p < 0.05).These relationships can be caused by the higher fiber content in dandelion flour compared with WF.Fiber-rich additives lead to an increase in water absorption of flour and dough development time [40].The stability of dough during mixing also increased as a result of DF incorporation into the bread recipe.However, this relationship was not linear.This parameter is correlated with flour baking strength.Flour with a long stability time generally requires a longer kneading time and is more suitable for hearth bread production [39].DF had relatively little influence on the degree of dough softening when the level of the replacement of WF was from 2% to 4%.When flour was replaced with 1%, 5% and 6% of DF, a noticeable decrease in the degree of dough softening was found.This parameter corresponds to the susceptibility of dough to the resistance of mixing.A strong negative correlation was found between this parameter and the stability of dough during mixing (r = −0.915,p < 0.05).Presented results suggest that dried and powdered DF had a positive effect on dough rheological properties and strengthened the dough's tolerance to overmixing.According to published data, different fiber-rich additives usually increase the water absorption of WF blends and make the wheat dough more stable during mixing [41,42].Interestingly, powdered dandelion roots (DR) had the reverse effect on the physical properties of wheat dough as determined by using a farinograph.Recently, Cacak-Pietrzak et al. [23] found that replacement of WF with DR (from 1 to 6%) caused a decrease in the water absorption of flour blends and decreased the dough mixing tolerance.

Basic Characteristics of Control and Enriched Bread
The yield of bread linearly increased with the addition of DF (r = 0.983, p < 0.001) from 143% (CS) to 147.9% (D6) (Table 3).It was caused by higher water absorption of DF-enriched flour.In addition, moisture content of crumb increased with DF percentage in the bread recipe from 43.7% (CS) to 46.8% (D6) (r = 0.900, p = 0.006).The addition of DF had a negative influence on bread volume as a result of weakening the gluten network structure.Bread volume decreased linearly with the level of DF in bread (r = −0.989,p < 0.001).Consequently, the crumb density increased from 0.273 g/cm 3 for CS to 0.352 g/cm 3 for D6.The volume of a loaf is an important quality parameter because it influences final gas retention in the loaf and affects consumer preference [27].Although consumers usually prefer higher volume and low-density crumb with soft texture, the reduction in bread volume influences the glycemic response and causes a reduction in glycemic index [28].Interestingly, farinograph data (Table 2) showed that DF strengthened the dough and increased water absorption of flour blends, development time and stability of dough, especially for D5 and D6 samples.However, these changes had no positive effect on bread volume.Thus, it can be concluded that although dough kneading of DF-enriched wheat dough strengthened the dough structure, during the next steps of bread production such as fermentation and baking, the reverse effect occurs, and the weakening of dough is observed.Consequently, the volume of bread decreased.Incorporation of nongluten ingredients into WF leads to the interactions of proteins with used additives, and during dough mixing and resting, the loss of some proteins from the gluten network is observed [43].On the other hand, the addition of some hydrocolloids as gluten substitutes can have a positive effect on the volume of bread [44,45].

Bread Texture
Bread texture is an important parameter for consumers' acceptance.This feature can be modified both by using additives and through processing.Replacement of WF with DF at a level higher than 2% significantly increased crumb hardness compared with the control sample (Table 4).It resulted from a lower volume of bread, which consequently produced a denser and more compact crumb.The coefficient of correlation between the volume of bread and crumb hardness was significant and negative (r = −0.907,p = 0.005).Crumb hardness ranged from 6.08 N (CS) to 10.63 N (D6).On the other hand, DF incorporation into bread had little influence on crumb elasticity and no significant impact on the springiness and cohesiveness of bread.Both gumminess and chewiness linearly decreased with the percentage of DF, mainly as a result of the increase in crumb hardness.The negative influence of different plant additives on wheat bread texture, as a result of gluten weakening, was observed by many authors [46,47].However, this effect is not always observed.Recently, Dziki et al. [48] showed that the replacement of WF with parsley leaf powder in the range of 1-5% does not have a negative influence on crumb hardness.This characteristic results mainly from used ingredients, bread density and moisture content.The additives which strongly increase crumb moisture have little influence on crumb hardness because water is a plasticizer, and higher water content in bread results in softer crumb [49].

Crumb Color
Color is an important determinant of food acceptability and is related to the AC of plant food [50].DF caused significant changes in color of the crumb (Figure 2).Lightness (L*) of bread samples decreased from 65.8 to 43.8 with the increased level of DF (r = 0.967, p < 0.05).The highest change in L* was found when WF was replaced with 1% of DF (decrease to 57.2).The redness (a*) of the crumb decreased when 1% and 2% of WF were replaced with DF.On the other hand, a higher level of WF replacement resulted in increased a* values, and crumb with 3, 4 and 5% of DF was characterized by similar hardness as the crumb of control bread.The highest redness was noted for the D6 sample (1.97) and the lowest for D1 bread (0.71).Enrichment of WF with DF resulted in increased yellowness (b*) of the crumb.However, no linear relationship was found between percentage of DF in the bread recipe and b* of bread.This parameter ranged from 15.9 for control bread to 22.0 when 3% of WF was replaced with powdered dandelion.∆E between the control bread and enriched loaves changed from 10.1 to 22.1 and increased linearly with the addition of DF (r = 0.99, p < 0.05).This indicates that the replacement of WF with DF at the level of 1% caused noticeable changes in the color of the crumb.DF are a rich source of carotenoids, especially lutein epoxide, responsible for the yellow color of dandelion petals [51].These compounds are mainly responsible for color changes of the crumb.Recently, Cacak-Pietrzak et al. [23] showed that dandelion roots also decreased the lightness and redness of wheat bread crumb but decreased yellowness.However, the range of these changes was lower compared with DF-enriched bread.

TPC and AC
Dandelion flowers are a rich source of phytochemicals, especially flavonoids such as luteolin O-hexoside and luteolin [52], and phenolic acids [53].Phenolic compounds provide many health benefits.They can protect vitamins, lipids and proteins from oxidation and consequently decrease their biological degeneration [54].The total phenolic content in DF was 32.08 ±1.45 mg GAE/g DM.However, antiradical activity against DPPH and ABTS expressed by EC 50 index amounted to 8.20 ± 0.27 mg DM/mL and 8.63 ± 0.35 mg DM/mL, respectively.Replacement of WF with DF resulted in a linear increase of TPC in all enriched bread samples (r = 0.986, p < 0.05).TPC ranged from 1.00 mg GAE/g DM for control bread to 3.45 mg GAE/g DM for D6 bread (Table 5).Importantly, bread with 2% and 3% of DF characterized about twofold higher TPC compared with the unfortified product.The antiradical activity also increased with the percentages of DF in the bread recipe.Both in the case of DPPH and ABTS, the values of EC50 decreased as the content of DF in bread samples increased.It indicates that AC increased from 614.8 to 141.9 mg DM/mL and from 129.7 to 87.9 mg DM/mL in the case of DPPH and ABTS, respectively.A similar tendency was found when powdered dandelion root was used as an additive to WF [23].However, from comparing our results with the results obtained for bread enriched with dandelion root, it can be concluded that DF more effectively increased the AC of the bread sample when the same amounts of flour were replaced with these additives.Further, other studies confirm that DF as a component of foods could potentially bring many benefits for human health [55].Phenolic fractions from DF are recognized as a better source of phytochemicals, especially flavonoids, than leaves and can be a very promising source of many bioactive compounds with increased AC, beneficial for the prevention of diseases associated with high oxidative stress [56].

TPC and AC
Dandelion flowers are a rich source of phytochemicals, especially flavonoids su luteolin O-hexoside and luteolin [52], and phenolic acids [53].Phenolic compounds vide many health benefits.They can protect vitamins, lipids and proteins from oxid and consequently decrease their biological degeneration [54].The total phenolic con in DF was 32.08 ±1.45 mg GAE/g DM.However, antiradical activity against DPPH ABTS expressed by EC50 index amounted to 8.20 ± 0.27 mg DM/mL and 8.63 ± 0.3 DM/mL, respectively.Replacement of WF with DF resulted in a linear increase of TP all enriched bread samples (r = 0.986, p < 0.05).TPC ranged from 1.00 mg GAE/g DM control bread to 3.45 mg GAE/g DM for D6 bread (Table 5).Importantly, bread wit and 3% of DF characterized about twofold higher TPC compared with the unfort product.The antiradical activity also increased with the percentages of DF in the b recipe.Both in the case of DPPH and ABTS, the values of EC50 decreased as the con of DF in bread samples increased.It indicates that AC increased from 614.8 to 141.DM/mL and from 129.7 to 87.9 mg DM/mL in the case of DPPH and ABTS, respecti A similar tendency was found when powdered dandelion root was used as an additi WF [23].However, from comparing our results with the results obtained for bread riched with dandelion root, it can be concluded that DF more effectively increased AC of the bread sample when the same amounts of flour were replaced with these a tives.Further, other studies confirm that DF as a component of foods could poten bring many benefits for human health [55].Phenolic fractions from DF are recognize a better source of phytochemicals, especially flavonoids, than leaves and can be a promising source of many bioactive compounds with increased AC, beneficial fo prevention of diseases associated with high oxidative stress [56].

Sensory Evaluation Results
The appearance of control bread (CS) and DF-enriched breads is presented in Figure 3. CS received the highest scores for all sensory attributes, such as smell, taste, texture, appearance and color.Consequently, the overall acceptability of CS was the highest (8.0 points).DF decreased the scores for all attributes.However, the highest decrease was observed in smell and appearance, especially when WF was replaced with DF at a level higher than 2%.When 3% of WF was replaced with DF, the enriched bread was slightly acceptable.In contrast, D4, D5 and D6 bread samples were assessed as neither like nor dislike, dislike slightly and dislike moderately for most of the sensory attributes, respectively (Table 6).The surface of the bread for these samples was nonhomogeneous, exhibiting holes and cracks, and the shape of the loaves was more irregular compared with other breads.Moreover, the crumb was more compact as a result of the higher density of enriched loaves.At 3% and higher addition of DF, a difference in taste was noticeable compared to the control bread due to the appearance of a bitter and grassy aftertaste.The aftertaste became more intense with the increase in the content of DF.Recently, other studies showed that also for powdered dandelion roots, the acceptable level of this addition in the bread recipe should not exceed 3% of WF replacement [23].Sensory acceptability is a key determinant of food consumption.Enrichment of WF with different additives can increase [57] or decrease [58] the overall acceptability of bread.The negative effect of enrichment on the volume of bread and texture of the crumb is most often observed [58][59][60].
higher than 2%.When 3% of WF was replaced with DF, the enriched bread was slightly acceptable.In contrast, D4, D5 and D6 bread samples were assessed as neither like nor dislike, dislike slightly and dislike moderately for most of the sensory attributes, respectively (Table 6).The surface of the bread for these samples was nonhomogeneous, exhibiting holes and cracks, and the shape of the loaves was more irregular compared with other breads.Moreover, the crumb was more compact as a result of the higher density of enriched loaves.At 3% and higher addition of DF, a difference in taste was noticeable compared to the control bread due to the appearance of a bitter and grassy aftertaste.The aftertaste became more intense with the increase in the content of DF.Recently, other studies showed that also for powdered dandelion roots, the acceptable level of this addition in the bread recipe should not exceed 3% of WF replacement [23].Sensory acceptability is a key determinant of food consumption.Enrichment of WF with different additives can increase [57] or decrease [58] the overall acceptability of bread.The negative effect of enrichment on the volume of bread and texture of the crumb is most often observed [58][59][60].

Conclusions
The partial replacement (from 1 to 6%) of WF with powdered flowers of Taraxacum officinale increased flour water absorption, development time and stability of the dough.However, the only positive effect of these changes was on bread yield.DF decreased the volume of bread and increased crumb hardness but enhanced the nutritional value of loaves.Ash content, total dietary fiber and fat content increased with the level of DF in the loaf recipe.In addition, the color of the crumb also changed after the fortification of bread with DF, particularly in decreased lightness and increased yellowness.Moreover, addition of DF increased TPC and AC of bread but decreased the linking scores for all sensory attributes.Replacement of WF with 2-3% of DF seems to be a compromise between the quality and increased health properties of DF-enriched bread.

Table 1 .
Basic chemical composition of WF, DF and bread (% DM)., 5 and 6% of DF, respectively.Data are presented as means with standard deviations (n = 3).Values of each parameter with different superscript letters a-g in the columns are significantly different (p < 0.05).

Table 2 .
Physical properties of control wheat dough and DF-enriched dough samples.

Table 3 .
Basic characteristics of control and DF-enriched bread.

Table 4 .
Texture of control and DF-enriched bread samples.

Table 5 .
Total phenolic content and antioxidant activity of control and enriched bread.