Bread making potential of Triticum aestivum and Triticum spelta species

2.1 Plant materials/agronomic trials

The analyzed grain samples were obtained from a three-year field experiment (2014-2016) conducted at the Experimental Station in Osiny (51°35’, 21°55’), Institute of Soil Science and Plant Cultivation, State Research Institute, Puławy, Poland. The experiment was situated on pseudopodic soil, pH 6.76. Crop rotations with 50, 75 and 100% proportions of cereals were used. Crops in different crop rotation are presented in Table 1. Wheat cultivation was performed in accordance with good agricultural practice standards (nitrogen fertilization, sowing term and sowing density). The fertilization level was carried out by balance method taking into account the content of bioavailable forms of phosphorus and potassium and the content of mineral nitrogen in the soil. The crops were protected against weeds, diseases and pests by applying Alister Grande (active substances: diflufenican, mesosulfuron-methyl, iodosulfuron methylsodium) 1.0 l ha^-1, Capallo 337 SE (active substances: fenpropimorph, epoxiconazole, metrafenone)1.5 l ha^-1 + Fury 100EW (zetacypermethrin) 0,1l ha^-1 + Medax Top 350 SC (mepiquat chloride, prohexadione calcium) 0,8 l ha^-1. Harvest was performed at full maturity phase.

2.2 Grain and flour quality parameters

Gluten content, gluten index, Zeleny sedimentation index, falling number and alveograph properties were determined to assess the baking quality of the tested wheat species. A hammer mill (FN 3100, Perten Instruments, Sweden) equipped with a 0.8 mm sieve was used to grind each wheat sample to wholegrain flour for gluten and falling number analyses. Wet gluten content and gluten index were determined according to ICC Standard No. 155 (Glutomatic 2200, Perten Instruments, Sweden). The gluten index (GI) is a method of analysing wheat protein that provides simultaneous determination of gluten quality and quantity. The GI value expresses a weight percentage of the wet gluten remaining on sieves after automated washing in salt solution and centrifugation (Centrifuge 2015, Perten Instruments, Sweden). GI allows for a reliable prediction of bread-making quality. Zeleny sedimentation index was determined according to ISO 5529 (Shaker Brabender, Germany) and falling number according to EN ISO 3093 (Falling number 1800, Perten Instruments, Sweden). A Sedimat laboratory mill (Brabender GmbH & Co. KG, Germany) was used to grind each sample to flour for the Zeleny sedimentation test.

2.3 Rheological tests

Rheological properties of dough were studied using the alveograph test (ISO 27971). Grain samples were adjusted to 16% moisture content with water. After conditioning overnight for 24 h ± 1 h, grain samples were milled in a Chopin-Dubois 1 laboratory mill to obtain flour for the determination of the rheological properties of dough by Chopin alveograph. Gluten extensibility (alveograph L (mm)), tenacity (alveograph P (mm)), baking value (alveograph W(×10-4J), tenacity/extensibility ratio (alveograph P/L), dough swelling index G (ml), and elasticity index Ie (%) were determined according to the alveograph manufacturer’s instructions (Chopin, France), using 220 g flour samples and constant water absorption (55%) (ISO 27971).

2.4 Protein fraction composition

To determine the content of particular protein fractions, a 3 grain sample was ground in an IKA A10 laboratory mill (Labortechnik) in such a manner so that all particles could be sieved through a 400 μm mesh sieve (ether particles smaller than 250 μm accounted for 90%). The samples were degreased with petroleum ether in Soxhlet extractors (16 hours). After evaporation of the solvent, 100 mg portions of powder were weighed out and placed in Eppendorf tubes, and then three protein fractions were extracted according to [24].

1. Albumins + globulins – double extraction of 1 cm³ of the mixture (0.4 mol/L NaCl + 0.067 mol/L HKNaPO₄ with a pH of 7.6

2. Prolamins – triple extraction of 1 cm³ of the mixture (60% ethanol)

3. Glutelins – double extraction of 1 cm³ of the mixture (50% propanol 1+2 mol/L urea 0.05 mol/L Tris-HCl (pH 7.5) + 1% DTE under nitrogen.

The first two protein fractions were extracted at room temperature using an Eppendorf thermomixer (10-minute extraction). Glutelins were extracted at 60°C in the thermomixer. After each extraction, the mixture was centrifuged at 11000 x g. The collected fractions were lyophilized and then dissolved in 2 cm³ of the respective phase (1-3), cleaned through a Spartan – 3NY filter with a 0.45 μm mesh and transferred to glass vials. The determinations were made using a Hewlett Packard Series 1050 system with the following parameters: column RP-18 Vydac 218TPP54, 5 μm, 250 x 4.6 mm, pre-column Zorbax 3000SB-C18 4.6 x 12.5 mm, column temperature 45°C, mobile phase flow rate 1 ml per min, injection size of 20 μl. The separation was performed using a two-component gradient. The proportion of component A: 0 min 75%, 5 min 65%, 10 min 50%, 17 min 25%, 18 min 15%, 19 min 75%. The first gradient (A) was water with an addition of 0.1% TFA, while the second gradient (B) was ACN with an addition of 0.1% TFA. The detection was carried out using a detector manufactured by the same company, and the reading was done at a wavelength of 210 nm. The results were analyzed using HPLC 3D ChemStation software (Hewlett Packard).

2.5 Statistical analysis

Analyses of all parameters were performed in four replications. The data was computed by multi-way analysis of variance (ANOVA) and the least significant difference (LSD) multiple range test was used at the 0.05% level. STATISTICA 6.1 (StatSoft Inc., Tulsa, USA) software was used.

3.1 Factors influencing quality parameters

The results of the analysis of variance showed that almost all the factors had a significant effect on the different traits. Species was the most important factor explaining the variation, followed by share of cereals in crop rotation (SCCR) and G × SCCR interaction. Wheat species had a significant impact on most of the tested traits, except tenacity/extensibility ratio (alveograph P/L) and G (alveograph value). The share of cereals in crop rotation significantly influenced sedimentation index, falling number, baking value (alveograph W), extensibility (alveograph L), dough swelling index (alveograph G) and elasticity index (alveograph Ie). We also found interaction between cereals in crop rotation and species in gluten index, sedimentation index, strength, extensibility, tenacity/extensibility ratio (Table 2-6). The importance of crop rotation on the grain quality of wheat was confirmed by Babulicová et al. [25]. The authors found that in crop rotation with less share of cereals, the wet gluten content and gluten index were statistically higher than in crop rotation with a higher share of cereals. They also found that falling number and sedimentation index was not affected by the share of cereals in crop rotation.

3.2 Baking properties of tested wheat grain

The two tested species differed with respect to many quality traits. Triticum spelta had higher gluten content, falling number, and alveograph extensibility (L value) compared with Triticum aestivum, but lower gluten index, sedimentation value, and alveograph parameters such as: W, P, P/L ratio and Ie value (Table 7). The differences between Triticum aestivum and Triticum spelta in gluten content have been confirmed in a number of previous studies [26, 27, 28, 29]. According to Rachoń et al. [29], the differences between gluten content for spring spelt cv. Blauer Samtiger and spring wheat cv. Parabola equaled 8.9%. We found the difference to be 5.6%. Majewska et al. [30], showed that flours of spelt wheat cultivars such as: Ceralio, Schwabenkorn, Frankenkorn, Holstenkorn, Schwabenspelz, Ostro and Oberkulmer Rothkorn, were characterized by significantly higher wet gluten content (interval 27.3-45.6%) comparing to common wheat flour cv. Korweta (22.5%). Our study is in agreement with those findings; the differences between Bamberka and Rokosz cv. equaled 5.6%. When comparing our results to those described in the literature, we notice that cv. Rokosz was characterized by similar wet gluten content to the German spelt wheat cultivars (Schweizer, Altgold, Zeinnars, Weisser, Bastard, Burgdorf, Oberlander) in which the gluten content was in the range of 31-37% [31]. Furthermore, the research conducted by Krochmal–Marczak and Sawicka [32], showed that wet gluten content in spelt wheat (Frankencorn, Ceralio and Schwabencorn) was lower (in range of 23.5 – 27.5%). The wet gluten content was not influenced by the share of cereals in crop rotation or by the interaction between wheat species and percentage of cereals in crop rotation (Table 2). Our results are in contrast to results obtained by Babulicova and Gavurnicova [25]. They concluded that significantly higher wet gluten content was found in crop rotation with 60% share of cereals, compared with crop rotation with 80% share of cereals. Additionaly, according to Rachoń et al. [29], the wet gluten content is influenced by the level of inputs.

According to Capouchová [10] the gluten of spelt wheat has lower quality than the gluten of the common wheat, which is in agreement with our study. For baking purposes, wheat with a gluten index of 60-90% is most desirable. Wheat with an index of less than 50 is more difficult to process; the dough is sticky, and is mainly suitable for biscuits with an additional potential application in two-layer flat breads [33]. Common wheat cv. Bamberka was characterized by a significantly higher average gluten index (76.9) over the three years, compared to Rokosz cv. (35.4) (Table 7). The previous study [12] showed a large variability in gluten index from 10.2 to 34.2%. The ideal gluten index of 60-90% was not achieved by spelt in any crop rotation. However, we found an interaction in gluten index between crop rotation and wheat species (Figure 1). In cv. Rokosz, the lowest gluten index was in the 75% share of cereals compared with 50 and 100%. In cv. Bamberka on the other hand, the lowest gluten index was in the 100% share of cereals compared with 50% and 75%. Our results are in agreement with Babulicova and Gavurnicova [25]. Additionaly, one more study [34] reports that nitrogen fertilization had an important role in the gluten index value of spelt wheat.

Figure 1

Interaction between the wheat species and share of cereals in crop rotation in gluten index

The sedimentation index characterizes the viscoelastic features and quality of the proteins and it indicates the potential for the fermentation process in the dough. When comparing yearly averages, significantly higher values were found in the common wheat cv. Bamberka (41.1 ml), followed by cv. Rokosz (29.7 ml) (Table 7). The results agree with those obtained by other researchers [3, 12, 29] according to which the sedimentation index in the spelt wheat grain was lower than in the common wheat grain. The sedimentation index was also influenced by the share of cereals in crop rotation and the interaction between wheat species and crop rotation (Figure 2). In cv. Bamberka, the lowest value of sedimentation index was in the 100% share of cereals, but in cv. Rokosz, the highest sedimentation index was in the 100% share of cereals. Similar results were achieved by Babulicova and Gavurnicova [25], and López-Bellido et al. [35].

Figure 2

Interaction between the wheat species and share of cereals in crop rotation in sedimentation index

The falling number test is used to evaluate the amount of sprout damage and gives an indication of alpha-amylase activity in grains. We found that Triticum spelta had the highest falling number value compared with common wheat (Table 7). This is in agreement with other studies [12]. Available literature indicates a large variation in the value of the falling number in spelt varieties. According to Rachon [29], falling number values ranged from 228 (Ceralio variety) to 354 (Holstenkorn variety). However, according to Makowska et al. [31], the values of falling numbers ranged from 150 (variety Oberlander) to 228 (Bastard variety). The share of cereals in crop rotation significantly influenced the falling number. In both studied species, the highest falling number was in the 100% share of cereals in crop rotation but the lowest after winter rape in the 50% of cereals in crop rotation. Babulicova and Gavurnicova [24] did not find differences between falling number and crop rotation.

3.3 Rheological properties of dough

The rheological properties of spelt dough and wheat dough were assessed using an alveograph. Rheological features of dough are a function of the properties of flour’s components and their mutual interactions occurring as a result of hydration and energy supply during kneading. It is known that starch, gluten, pentosans and fat play a crucial role in forming wheat dough [36]. The analyzed wheat doughs differed in “W” value. Alveograph baking value (W), an indicator of baking quality, in tested wheat flour samples ranged from 69 to 420×10^-4J which according to Abramczyk and Stępniewska [37] indicates its wide technological suitability. Good quality wheat and improving wheat should be characterized by “W” values in the range 220-300×10^-4J and higher than 300×10^-4J, respectively, whilst confectionary wheat should be characterized by ”W” values in the range of 160 to 200×10^-4J [37]. In our study, the Bamberka was characterized by a good “W” value (312×10^-4J), but Rokosz by the lowest baking value “W” (146×10^-4J), which informs the potential user of grains about the lower quality of gluten complex and its suitability for production of, for example, waffles (Table 7). This results are confirmed by Sobczyk et al. [39]. Spelt wheat dough energy of 10 cultivars was lower compared to common wheat. They found differences between cultivars. The largest energy (71 cm²) was found for the dough of Schwabenkorn cv flour, while the smallest for the STH 8 line (24 cm²) and the Ostro cv (25 cm²). Grobelnik Mlakar et al. [40] reported similar values of this parameter (35-36 cm²) for the spelt dough. The tested spelt flours can be regarded as weak, according to the classification given by Boyacioglu and D’Appolonia [41].

Alveograph parameter (P), is considered as an indicator of the dough’s tenacity and is dependent on the viscosity of dough and a measure of the absorption capacity of flours. The highest alveograph tenacity (P) was detected for wheat variety Bamberka (118 mm), the lowest for cv. Rokosz (62 mm) (Table 7). Krawczyk et al. [9] assessing the Polish spelt genotypes showed that the values of this feature were very diverse and ranged from 54 mm (STH 12) to 218 mm (STH 11). Lower values of this parameter in spelt wheat were confirmed by Sobczyk et al. [38]. Alveograph parameter (L), which is related to dough extensibility and predicts the handling properties of the dough in the tested wheat samples, was in the range of 24 to 135 mm [38]. The highest extensibility was demostrated by Triticum spelta (88 mm) compared with common wheat (79 mm) (Table 7). Similar results were obtained by Sobczyk et al. [39]. They found that spelt doughs showed a lower resistance to extensibility compared to the wheat dough. The P/L index is a commonly used parameter in the wheat trade where a value of 0.50 indicates either resistant and very extensible dough or moderately extensible less resistant dough. The P/L value for Bamberka was 1.53, and for Rokosz 0.71 (Table 7). The value of 1.50 indicates very strong and moderately extensible dough, whilst raw material with a P/L value in the range of 0.40 to 0.80 is suitable for bakery production. Wheat suitable for confectionery products should exhibit aP/L value lower than 0.50 [38]. Dough obtained from cv. Rokosz was characterized by high tenacity and low extensibility (P/L index above 1.0).

The share of cereals in crop rotation had an important influence on the parameters: ”W”, “L”, “G” and “Ie”. (Table 8). In both cultivars the “W” parameter was the highest in 50% of cereals in crop rotation but the smallest when wheat was grown in 100% share of cereals . In the available literature, there are few studies on the influence of agrotechnical factors on alveographic features in spelt wheat. Podolska et al. [34] showed that the baking value “W increased with anincrease in nitrogen dose. Similarly, the “P” value and “Ie” value increased with the applied dose of nitrogen from 37 to 45 mm and from 44.4 to 46.7 (%), respectively and was highest at the highest dose of nitrogen.

3.4 Protein fraction composition

In the current study, we found that the spelt wheat protein fractions had different compositions compared with common wheat. We detected larger fractions of albumins and globulins in Triticum aestivum compared with Triticum spelta. In common wheat, the total protein content equaled 21.6%, versus 20.4% in spelt wheat The smallest sub-fraction of gliadins was ω-gliadins, which ranged from 2.5% of total protein content in spelt wheat, to 3.0% in common wheat. The largest sub-fraction was α/β-gliadin, comprising 20.0% of total protein in spelt wheat, to 22.1% in common wheat. The γ- gliadin content ranged from 14.2% of total protein (spelt wheat) to 15.4% (common wheat)(Fig. 3). Research conducted by Mikos-Szymańska and Podolska [42] does not confirm these results. These authors reported that spelt wheat contained higher amounts of α / β gliadin and γ-gliadin compared to common wheat.

Figure 3

Proportion (%) of protein fractions in spelt and common wheat grains (protein =100%)

Slightly different gliadin contents in common wheat were reported by Konopka et al. [33], who detected 2% fewer ω-gliadins, 7% fewer α/β-gliadins and 2% fewer γ-gliadin compared with our results. According to the data in Table 7 and Figure 3, glutenins comprised 37.8 % of total protein content (common wheat) to 42% (spelt wheat). The baking value of flour is favorably influenced by an increase in the content of high molecular weight glutenin subunit (HMW-GS) and its ratio to low molecular weight glutenin subunit (LMW-GS) [42]. In our study the HMW-GS to LMW-GS ratio ranged from 0.38 (common wheat) to 0.40 (spelt wheat). Similar results for HMW-GS to LMW-GS ratio were obtained by Mikos-Szymańska and Podolska [42]. In spelt wheat this ratio was in the range of 0.40 to 0.45, compareed to 0.38 in common wheat [42].

Studies published by Stepien and Wojtkowiak [44] indicate that α/β-gliadins were the quantitatively predominant fraction of gliadin proteins in the grains of the examined wheat cultivars. This similarly indicated that the wheat cultivars differ from each other in the content of protein fractions. High molecular weight (HMW) and low molecular weight (LMW) subunits of glutenins are associated with dough energy and bread baking quality [15, 17]. The number of glutenin subunits is positively correlated with the dough energy and volume of bread, whereas the content of gliadins and a higher gliadin:glutenin ratio have a negative impact on these parameters [13, 17, 45, 46].

Despite the content of HMW proteins being lower in the grain of the examined cultivars, according to [17] they determine the properties of dough to a higher degree than do LMW proteins. Also, high temperature stress, drought, excess or deficiency of nutrients can affect the protein fraction. The studies by Stepien and Wojtkowiak [44] indicate that agrotechnical factors such as nitrogen fertilization and crop rotation have significant influence on HMW and LMW glutenins. Also Tóth et. al [47], found that low nitrogen and phosphorus treatments caused an increase in the gliadin and decrease in the glutenin fractions (HMW and LMW glutenins). Geisslitz et al [48] have shown that the ratio of gliadins and glutenins was influenced by the growing location, environmental conditions (temperature) and amount and time of fertilization, but Konopka et al. [33], found that the concentration of γ-gliadins and HMW and LMW glutenins decreased in the case of water deficit.