**1. Introduction**

As one of humanity's most important staple foods over time, bread has evolved into various forms, with distinctive and different characteristics. Bakers have made, and continue to make, traditional varieties based on accumulated knowledge, adapting existing methods and developing new ones, aiming at the best use of the available raw materials to obtain bread with the desired quality [1].

Wheat flour is the primary raw material for bread production in most of the world's regions and is a versatile raw material, accepting many additions in specific proportions [2,3]. Because the quality of wheat and flour varies greatly, improvers are added to wheat flour and dough in small amounts to obtain the desired and consistent bread quality [4]. The improver selection is made according to what needs to be improved and the flour's main technological properties, especially the power of flour and its ability to form gases to obtain the best possible result [5].

**Citation:** Vartolomei, N.; Turtoi, M. The Influence of the Addition of Rosehip Powder to Wheat Flour on the Dough Farinographic Properties and Bread Physico-Chemical Characteristics. *Appl. Sci.* **2021**, *11*, 12035. https://doi.org/10.3390/ app112412035

Academic Editor: Silvia Mironeasa

Received: 9 November 2021 Accepted: 10 December 2021 Published: 17 December 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

The most-used improvers in the bakery are amylolytic enzymes such as α-amylase from cereal malt [6,7]), fungal α-amylase from *Bacillus subtilis* [8] or *Lactobacillus plantarum* [9], β-amylase [10], and fungal amyloglucosidase from *Aspergillus niger* [11]; as well as proteolytic enzymes such as malt proteases [12], proteases from *A. oryzae* [13] and vegetable proteases (papain, bromelain); pentosanases such as exogenous or fungal xylanases [14–16]; fungal lipases [17]; lipoxygenases from wheat or soy flour [12]; transglutaminase produced by the bacterium *Streptoverticillium* [12]; cellulases [10]; natural emulsifiers such as lecithin from oil demucilagination [18,19]; synthetic emulsifiers such as polyalcohol esterified with paraffin chains [20]; oxidizing agents such as L-ascorbic acid (E300) [21], KBr (E924) [22,23], KI (E917) [24]; and reducing agents such as L-cysteine [25].

Ascorbic acid (AA) has been used as an improver in breadmaking since 1935 [26]. AA is added either into flour or directly into the dough. The role of AA in baking is to mediate the oxidation reactions that stabilise the dough for preserving its elastic and viscous properties so that the dough can retain gases and go through the stages of the breadmaking process (stretching, shaping, etc.) [26,27]. In addition to improving the ability of gluten to retain gases, ascorbic acid also contributes to faster proofing, as well as obtaining a piece of bread with a larger volume, a more delicate crumb, smaller and more pores, and to reduce the thickness of the bread crust. These changes also result in a softer crumb, making the bread look fresh for longer [28].

Although AA, the reduced form of vitamin C, is naturally present in many fruits and vegetables, most of the AA that supplies the bakery industry is obtained through chemical reactions that use glucose as a raw material [29]. Therefore, AA is classified as the chemical compound, E300 [30].

Sahi [31] presented some research results performed at Campden BRI, UK, where synthetic AA was replaced with AA-rich plant materials. Acerola cherry (*Malpighia emarginata*) extract was used in the research. Disclosed experimental data showed that the addition of acerola cherry extract leads to a dough with good farinographic properties. Thus, the dough development time was equal to that obtained for the control sample with synthetic AA. The softening degree in kneading tests in the farinograph was reduced to 64 Brabender Units (BU) but was close to dough with synthetic AA (70 BU) and lower than the control (120 BU). The bread volume, crumb structure, and texture were similar to bread obtained with chemical AA [31]. This research paved the way for more extensive possibilities of plant material selections to replace synthetic AA, especially when a clean label is desired [31].

Fruits of rosehip (*Rosa canina* L.) are recognised as a vegetal source rich in vitamin C, with the content in fresh rosehip varying between 100 and 1.400 mg/100 g (0.1–1.4%), with average values of 400–800 mg/100 g [32,33].

Rosehip fruits have been used, as a powder or an extract, in various formulas in baking to enhance the bread's nutritional value [34–36]. However, no research or trial has been developed to investigate the replacement of synthetic AA with rosehip fruits. Therefore, the research presented in this work is original and aims to study the influence of the rosehip powder (Rp) addition as a natural substitute for synthetic AA on the dough farinographic properties and bread quality.

#### **2. Materials and Methods**

#### *2.1. Materials*

The white wheat flour (WF, type 550) was purchased from Dizing SRL, Brusturi, Neamt County, a local milling and breadmaking company. It was not treated with ascorbic acid or other improvers.

The rosehip (*Rosa canina* L.) fruits were collected from the Dofteana area, Bacau County, at the maturity stage to benefit from the higher content of bioactive compounds. After discarding the achenes (the real fruits) containing the seeds, the dried sepals, and the remainder of anthers and filament, the hypanthium (fleshy shell or pulp) was dried in the dark at atmospheric conditions to avoid the loss of vitamins. The dried pulp of rosehip fruits was ground by an ultra-centrifugal laboratory mill, ZM 200 Retsch (18.000 rpm, 4 min) to obtain the Rp, then was sieved to select the particles around 180 μm in size, similar to wheat flour granularity. The obtained Rp was stored in airtight brown glass jars in the dark and was kept cold until use.

The Rp additions were selected based on the regular supplementation of wheat flour with ascorbic acid and the vitamin C content of Rp. Usually, the wheat flour is supplemented with 2 to 10 g ascorbic acid per 100 kg flour (10 mg/100 g), where the higher quantities in the interval are used for flour with lower quality indicators. Calculations based on the vitamin C content of Rp, just before the addition to flour (420 ± 16.09 mg/100 g), served to select the Rp addition levels used in the research, which were 0.5–2.5%.

Other ingredients used for breadmaking, i.e., salt and compressed yeast, were purchased from the local market (Bacau, Romania). Pakmaya compressed yeast was produced by Rompak SRL, Pascani, Iasi County, Romania.

Ascorbic acid was purchased from Enzymes & Derivates, Costis, a, Neamt County, which is a local supplier of ingredients for the food industry.

Chemicals and reagents, such as ethanol (C2H5OH, with a minimum of 95% *w*/*w*), concentrated sulphuric acid (98%), copper sulphate (CuSO4·5H2O), boric acid (H3BO3), clorhydric acid, and borax (Na2B4O7·10H2O) of an analytical grade were purchased from Merck (Darmstadt, Germany). Calcium chloride, natrium hydroxide, natrium chloride, and phenolphthalein of an analytical grade were purchased from Sigma-Aldrich (Steinheim, Germany).

#### *2.2. Proximate Compositions*

The proximate compositions of WF, Rp, and mixtures of wheat flour with 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of Rp were determined according to the official methods of analysis from the Association of Official Analytical Chemists [37] and the American Association of Cereal Chemists International [38], and in force standards, as follows: moisture content (SR 90:2007 [39]), ash content (SR EN ISO 2171:2010 [39]), protein content (SR EN ISO 20483:2014 [39]) through the Kjeldahl method using a nitrogen-to-protein conversion factor of 6.25 for Rp and 5.7 for wheat flour and flour mixtures (AACC method 46-11.02 [38]), lipids through an organic solvent extraction (Soxhlet method) (AOAC method 983.23 [37]), carbohydrates through the Luff–Schoorl iodometric method (AOAC method 920.183 [37]), wet gluten (SR 90:2007) [39], dry gluten (SR EN ISO 21415-3:2007) [39], the gluten deformation index, acidity, the sedimentation index, granularity (SR 90:2007) [39], and ascorbic acid (vitamin C) through the indophenol method (AOAC method 967.21 [37]).

#### *2.3. Farinographic Measurements*

The Brabender farinograph (Brabender Model E, Duisburg, Germany), according to SR EN ISO 5530-1:2015 [39] and the AACC method 54-21 [38], was used to determine the dough farinographic properties, namely: water absorption (WA in %), dough development time (DT in min), dough stability (DS in min), the softening degree (SfD in BU), and the Farinograph quality number (QN).

#### *2.4. The Breadmaking Procedure*

The doughs were prepared with the direct (one-stage) method (SR 91:2007 [39]) using the following recipe per 100 g of wheat flour: 1.5% salt, 1.8% compressed baker's yeast, 0–2.5% Rp, and water (58–65 mL), according to the water absorption of each mixture of WF and Rp. The quantities were calculated for 3 kg of wheat flour to obtain around 5 kg of dough. Mixing and kneading were performed in a Diosna dough mixer with a removable bowl, a 12 kg maximum dough capacity, and 0.44/0.9 kW of motor power. After 10 min of kneading, the dough was fermented for 150 min at 28–30 ◦C in the mixing bowl, divided into pieces of 380 g, moulded, and introduced into baking trays. After the additional 50–60 min of leavening at 30 ◦C in a continuous proofer, the samples were baked for 20 min at 230–240 ◦C. Proofing and baking were accomplished on the technological flow of the Dizing breadmaking company.

#### *2.5. Bread Characterization*

The bread samples were stored for 120 min at room temperature before analysis. The physico-chemical analysis of bread samples included the determination of the bread height, moisture, porosity, elasticity, and acidity of the crumb (SR 91:2007 [39]), as well as measuring the volume through the rapeseed displacement method (SR 91:2007 [39]).

#### *2.6. Statistical Analysis*

The results are reported as the average values of two or three replicates, along with their standard deviations (three replicates, especially for Rp and sensitive analyses). A oneway analysis of variance (ANOVA) was carried out with the Microsoft Excel programme, Microsoft Office 2010, to detect significant differences among results. Fisher's least significant difference (LSD) test at a 95.0% confidence level, used to determine differences between values, was applied using the Statgraphics Centurion XVI.I software (Statgraphics Technologies, Inc., The Plains, Virginia, USA).

#### **3. Results and Discussion**

#### *3.1. The Proximate Composition of the Flours*

The proximate compositions of Rp, WF, and the flour mixtures (WF–Rp) obtained with the addition of 0.5–2.5% are shown in Table 1.



WF—wheat flour, Rp—rosehip powder, WF–Rp—mixtures of wheat flour with rosehip powder, WF–AA—wheat flour with ascorbic acid addition of 2 mg/100 g. Different letters within the column indicate the values are statistically different at a 95.0% confidence level.

> Rp showed a vitamin C content of 420 ± 16.09 mg/100 g, which belonged to the interval of 100–1.400 mg/100 g [32,33,40–43]. Moreover, Rp contains a high ash content, indicating a high mineral salts content, low protein content, and high levels of fibres and carbohydrates (Table 1).

> Because Rp has a moisture content (13.40 ± 0.15%) lower than wheat flour(14.15 ± 0.06%), the addition of Rp in wheat flour resulted in a slight decrease in the moisture of the flour mixtures as the added amount of Rp increased. Thus, the lowest values of moisture (14.13%) were obtained with the addition of 2.0 and 2.5% of Rp into the wheat flour. According to the ANOVA, the differences between the moisture values of the samples were not significant (*p* > 0.05). This finding is due to the small amounts of the Rp additions. The results are consistent with other literature [44,45].

> The results presented in Table 1 indicated that due to the increase of the Rp addition, the ash content increased from 0.55 ± 0.01% in the control to 0.70 ± 0.07% in the sample with 2.5%. The ash content of the Rp used was 6.5 ± 0.07% which explains the ash increase in the flour mixtures. The results are similar to other data presented in the literature. Koletta et al. [46] reported an ash content of 0.63% in wheat flour and 1.26% in barley flour, and Cvetkovi´c et al. [47] obtained an ash content of 3.71% in dried rosehips.

> The protein content (Table 1) of the flours decreased from 13.45 ± 0.03% in the control to 13.21 ± 0.04% in the sample with 2.5% Rp, i.e., a reduction of 1.78% compared to the control sample. This decrease is due to Rp, which has a lower protein content (4.89 ± 0.11%) than wheat flour.

Van Hung et al. [48] studied the quality of dough and bread made from whole wheat flour, intending to delay the ageing of bread. The wholemeal flour with which the studies were carried out had a significantly higher protein content than commercially available white wheat flour (13.5% compared to 12.6%).

Dall'Asta et al. [49] reported a study on the influence of a chestnut flour addition to white wheat flour on the bread's physicochemical properties and volatile components. The mixtures made were 80/20 and 50/50 white soft wheat flour/chestnut flour, with white flour alone as the control sample. As chestnut flour has a lower protein content than wheat flour, the obtained mixtures also had a lower protein content than the control sample. Thus, the protein content ranged from 13.2% for wheat flour to 5.8% for the 50/50 wheat flour/chestnut flour mixture.

According to the ANOVA, the differences between the protein content of WF and WF–Rp were not significant (*p* > 0.05).

The lipid content of Rp was 0.76 ± 0.05%, quite close to that of WF (0.83 ± 0.07%). The flour mixtures showed lipid contents situated between these values, almost without any variation, as the ANOVA analysis confirmed (*p* > 0.05) (data not shown).

A study by Sun et al. [50], regarding the addition of wheat germ flour (3%, 6%, 9%, and 12%) to white flour to obtain Chinese steamed bread, does not mention the lipid content of the resulted mixtures, only that of white flour (1.3%).

The different evolutions of lipid content could be achieved when the ingredients used have higher values. Pınarlı et al. [51] obtained pasta (macaroni) from durum wheat flour (semolina) mixed with 15% wheat germ, obtaining a significant improvement in nutritional value. Other authors, e.g., Arshad et al. [52] mentioned that they replaced up to 25% of wheat flour with defatted wheat germ and obtained improved functional and nutritional properties for prepared cookies.

The carbohydrate content for the control sample and flour mixtures had a very slight growth tendency with increased amounts of Rp added (Table 1). Wheat flour has a carbohydrate content of 70.68 ± 0.29% and Rp has a carbohydrate content of 73.66 ± 0.19%. The highest value of carbohydrate content, 71.04%, was obtained with the addition of 2.5% Rp, representing an increase of only 0.51% compared to the carbohydrate content of the control sample. According to the ANOVA analysis, this variation was not significant (*p* > 0.05) compared to the carbohydrate content of the control sample because the Rp was added in tiny proportions.

The fibre content of WF–Rp varied with Rp addition values, increasing by about 0.02% for every 0.5% of Rp added, from 0.1 ± 0.07% in white flour to 0.2 ± 0.06% in the mixture with an addition of 2.5% Rp. According to the ANOVA single-factor statistical analysis, the differences were not significant (*p* > 0.05).

The total fibre content of whole wheat flour obtained by Van Hung et al. [48] was 15.3%, divided into 11.2% insoluble and 4.1% soluble fibres. The white wheat flour used in their research contained 3.4% total fibre with 1.6% insoluble and 1.8% soluble fibres because most of the fibre, both soluble and insoluble, was removed with bran and germs. The authors [48] believed that wholemeal wheat flour with a high fibre content, especially insoluble fibre, is a suitable raw material for high-fibre foods. However, these authors found that a high fibre content dilutes gluten proteins during dough kneading, leading to a soft and inelastic dough. Thus, bread made from whole wheat flour has a significantly smaller specific volume and larger pores than bread made from white flour [48].

The wet gluten in flour mixtures with Rp varies inversely with the addition of Rp, decreasing from 34.10 ± 0.07% in the control sample to 33.25 ± 0.07% with a 2.5% addition of Rp due to the absence of gluten-forming proteins in Rp. According to the single-factor ANOVA statistical analysis, the variation was not significant (*p* > 0.05), with the decrease of gluten content representing about 0.17% at each addition stage.

Banu et al. [44] found a reduction in wet gluten from 25.0 ± 0.15% for the control sample–white wheat flour to 24.4 ± 0.19%, 24.2 ± 0.19%, 24.1 ± 0.17%, 22.9 ± 0.16%, 21.0 ± 0.15%, 19.9 ± 0.15%, and 18.4 ± 0.14% for mixtures of white wheat flour with wheat

flour bran (3%, 5%, 10%, 15%, 20%, 25%, and 30%, respectively), the variations being significant (*p* < 0.05). The reduction of wet gluten is greater in this study due to the higher additions of wheat flour bran.

The sedimentation index, a parameter that reflects the quantity and quality of proteins in flour (wheat), increased from 25.0 for wheat flour to 29.0 for flour mixtures with 1.5% and 2.5% Rp, respectively, the variations being significant (*p* < 0.05). These values are in the range of 20–39, corresponding to a good quality flour for baking [4]. The additions of Rp in white wheat flour had tiny values (0.5–2.5%), and the protein content and wet gluten varied very little. Therefore, it could be stated that the addition of Rp did not affect the quality of proteins in WF. However, the sedimentation index increased almost linearly for the first mixtures, namely, the samples with a 0.5–1.0% Rp addition (27.0 and 28.0) and stagnated for the subsequent three samples (29.0), namely, those with a 1.5%, 2.0%, and 2.5% Rp addition (data not shown in Table 1).

The vitamin C content in flour mixtures (Table 1) reflected the addition of 0.5–2.5% of Rp in wheat flour to obtain the mixture flours. The differences were significant (*p* < 0.05). It is equal to (0.5% Rp), or higher than, the usual AA addition to dough in breadmaking when WF has a good quality. AA is a pure and more stable compound than vitamin C in Rp, which can be degraded easily during storage time.

#### *3.2. Dough Farinographic Properties*

The farinographic properties of the dough, namely, water absorption, the dough development time, stability, softening degree, and the farinograph quality number are presented in Table 2.


#### **Table 2.** Farinographic properties of doughs.

WF—wheat flour, Rp—rosehip powder, WF–Rp—mixtures of wheat flour with rosehip powder, WF–AA—wheat flour with ascorbic acid addition of 2 mg/100 g. Different letters within the column indicate the values are statistically different at a 95.0% confidence level.

> Bread dough is a viscoelastic material that shrinks when sheared, combining Hooke's solid and a non-Newtonian viscous liquid. It has a non-linear rheological behaviour but, at very low stresses, it has a linear behaviour. The stress at which the dough has a linear behaviour depends on the type of dough, the mixing method, and the testing method [53]. Information on the rheological properties of the dough helps predict potential applications of wheat flour and the quality of the finished product [54].

> The farinograph, a physical dough testing device, was used to assess how adding Rp to wheat flour affected the rheological properties of the dough. It allowed for the evaluation of the performance of flour mixtures and the breadmaking potential. The two z-shaped blades of the farinograph mixer rotate at constant speeds and subject the dough to mixing at a constant temperature [54].

#### 3.2.1. Water Absorption

Flour hydration is essential because it affects the functional properties and the quality of bread [55,56].

The water absorption of the wheat flour and flour mixtures, corrected for 500 BU (Table 2), showed a linear (R<sup>2</sup> = 0.94) increase with the increase of the Rp addition to the flour, from 58.20 ± 0.00% for the control to 61.90 ± 0.00% for the 2.5% Rp addition. According to the ANOVA single-factor statistical analysis, the differences were significant

(*p* < 0.05). The control sample with AA at 10 g/100 kg showed a water absorption identical to that of the control sample.

The increase in water absorption is widely discussed in the literature. Thus, numerous papers mention the positive influence of protein quantity and quality on water absorption [55,57–59]. Moreover, Hefnawy et al. [60] and Mohammed et al. [61] reported increased water absorption with increased protein content with chickpeas in wheat flour.

Since the addition of Rp to wheat flour decreased the protein content of the flour mixtures, the reason for the increase in water absorption must be sought somewhere else, for example, in the influence of fibre content. Gómez et al. [62] added purified fibres of various origins (oranges, peas, cocoa, coffee, wheat, and microcrystalline cellulose) to wheat flour bread. They obtained an increase in water absorption with an increase in the percentage of added fibres. For example, with the addition of 2% and 5% orange fibre, the water absorption was 63.00% and 65.40%, respectively, compared to 58.70% in the control sample (white wheat flour). The water absorption capacity increased with the addition of fibres due to the hydroxyl groups in the chemical structure of the fibres that allows the binding of water through hydrogen bonds [62]. Many other researchers have come to the same conclusion. Thus, introducing high-fibre wheat bran to white wheat flour increased the water absorption from 57.10 ± 0.20% in the control sample to 68.20 ± 0.60% for an addition of 30% wheat bran [44]. Similarly, Lauková et al. [63] obtained an increase in water absorption from 58.00 ± 0.70% for the control sample to 75.30 ± 0.70% for an addition of 15% hydrated apple powder. Similar results were reported by Kohajdová et al. [64] with the addition of carrot powder (water absorption increased from 60.67 ± 0.35% for the control sample to 72.01 ± 0.25% for a 15% addition of carrot powder) and Ajila et al. [65] with the addition of mango peel powder (water absorption increased from 60.00% for the control sample to 68.00% for a 10% addition of mango peel powder).

#### 3.2.2. Dough Development Time

The dough development time (DT) is measured by adding water to the flour until the dough reaches its maximum consistency without breaking. Water hydrates the flour components during the mixing phase, and the dough develops [63].

The DT for the control sample was 6.70 ± 0.00 min and varied between 6.60 ± 0.14 min (1.0% Rp) and 7.20 ± 0.14 min (2.5% Rp) for the flour mixtures. According to the ANOVA, the differences were not significant (*p* > 0.05), although close to the limit (*p* = 0.054), so the Rp addition had a relatively small influence on DT (Table 2). The wheat flour control sample with the AA addition had a DT of 6.60 ± 0.14 min, lower than the WF control, reflecting that the AA addition to the flour reduces the DT.

A similar effect of DT variations has been reported in several studies. Sudha et al. [66] observed an increase in DT from 1.5 min (control sample) to 3.5 min (an addition of 15% apple pomace with dietary fibre resulting from the manufacture of apple juice), Lauková et al. [63] found an increase in DT from 3.5 min. (control sample) to 11.0 min for an addition of 15% hydrated apple powder in white wheat flour, and Kohajdová et al. [67] observed an increase in DT from 3.43 min (control sample) to 5.53 min (an addition of 15% apple powder).

Kuˇcerová et al. [68] added different Vitacel brand fibres (JRS Company, Rosenberg, Germany) to the wheat flour. They found a slight increase in DT with an increasing fibre addition from 1% to 3%, compared to wheat flour, as follows: from 1.1 min to 1.3 min for wheat fibre (WF 200), 1.5 min to 1.7 min for apple fibre (AF 400), 1.9 min to 2.2 min for potato fibre (PF 200), and from 1.3 min to 1.5 min for bamboo fibre (BF 300).

In the given examples, it is observed that although the DT has increased in direct proportion to the fibre additions, the differences are tiny. Nikoli´c et al. [69] made a similar statement for flour mixtures with variable buckwheat flour additions. They reported an increase of DT from 1.0 min to 1.2 min for buckwheat flour additions ranging from 1 g/100g to 20 g/100 g flour mixtures and a maximum value of 1.5 min for 30 g/100 g.

The increase in DT was explained by the slowdown in hydration rate and gluten development due to adding ingredients that increased the fibre content in the mixtures obtained [63,66].

#### 3.2.3. Dough Stability

The data relating to the influence of the Rp addition on dough stability (DSt) are shown in Table 2. DSt increased from 11.00 ± 0.00 min (WF control) to 11.50 ± 0.42 min (0.5% Rp), then decreased below the value for the control sample, reaching 9.70 ± 0.14 min for 2.5% Rp. The DSt of the control WF with added AA was 11.20 ± 0.00 min, a little higher than the DSt of the WF sample. According to the ANOVA, the differences were significant (*p* < 0.05).

DSt provides some indications regarding the tolerance of flour to mixing and kneading [70]. Thus, Nassar et al. [71] reported the increase of DSt from 4.9 min for the control sample to 12.4 min and 11.5 min with the addition of 25% flour from orange peels and orange pulp, respectively. The same effect was observed by Kohajdová et al. [72], who reported an increase in DSt after the addition of apple fibre from 6.40 ± 0.15 min for the control sample, to 9.30 ± 0.64 min for the mixture with 15% apple fibre, and from 9.40 min to 10.90 min with the addition of 15% apple pomace fibre [67]. Moreover, Lauková et al. [63] reported a significant increase in DSt from 6.7 min for the control sample to 11.6 min with an addition of 15% hydrated apple powder. These authors explained the rise of DSt through a higher interaction of fibres, water, and proteins in flour [63,67]. On the other hand, the DSt in this research was considerably higher than the values obtained by adding buckwheat flour, in which case the DSt increased from 0.3 ± 0.1 min for the control sample to 4.6 ± 0.3 min with an addition of 30 g of buckwheat flour/100 g of wheat flour [69]. The opposite effect was reported by Sudha et al. [66] after adding apple pomace powder to the wheat flour in different proportions. Thus, the DSt decreased from 4.2 min to 2.1 min with an addition of 15% apple pomace fibre. These results are supported by Rosell et al. [73], who observed a decrease in DSt with increased additions (12.5–25%) of quinoa flour to wheat flour, and Liu et al. [74] reported a reduction in DSt of up to 30% for potato flour additions to wheat flour.

#### 3.2.4. Softening Degree

The softening degree (SfD) in BU is determined from farinograms 10 min after the start of the experiment (data not shown) and 12 min after the curve reached the maximum (Table 2). An ascending variation of SfD at 12 min was obtained for increased Rp additions to the wheat flour. The SfD increased linearly (R<sup>2</sup> = 0.95) from 58.00 ± 0.00 (control) to 91.00 ± 1.41 (2.5% Rp). According to the ANOVA, the differences were significant (*p* < 0.05).

There were no findings regarding the degree of softening resulting from the farinographic analysis in the studies mentioned above [44,55,59,62–69].

Instead, other researchers have mentioned a decrease in SfD. For example, Anil [75] observed a reduction in the SfD from 78.0 ± 2.0 BU for the control to 61.0 ± 1.0 BU and 39.0 ± 2.0 BU for the addition of 5.0 and 10.0% crushed and roasted hazelnut powder, respectively. Moreover, Stojceska & Ainsworth [76] noticed an increase in DT and DSt and a decrease in SfD from 25 UB for the control sample to 15, 20, and 5 UB for 10%, 20%, and 30%, respectively, with the addition of brewers spent grains to wheat flour. It should be noted that the proportions of spent grains used in this research were much higher than 0.5–2.5% Rp and could help in increasing the SfD. In another study [77], the authors observed a decrease in the SfD from 60.0 ± 1.0 UB for the control to 20.0 ± 2.0 UB for the samples with additions of fibre concentrates from the pulp of dates, pears, and apples in proportions that ensured a 2% fibre intake.
