The Advanced Approaches to Nutritional and Breadmaking Quality of Wheat, Barley and Rye Flour

Abstract: This work is focused on the characterization and rapid analytical determination of cereal flour quality with regard to nutritional and breadmaking quality. Starch， protein and non-starch polysaccharides are the main components of cereals. The content and quality of proteins and content of damaged starch is important because of the technological quality of flours. The high content of high molecular weight proteins is substantial for bread technology especially， while soluble protein fractions and non-starch polysaccharides are important for nutrition. The set of wheat， barley and rye flours and their blends were analyzed and their properties and their qualitative parameters were determined. Principal component analysis (PCA) was used on Fourier transform-infrared (FT-IR) spectra in the 1，200-800 cm-1 wavenumber region and significant correlations of various nutritional and breadmaking parameters were observed. Results showed that the FT-IR spectroscopy and PCA can serve for rapid screening and classification of cereal flour quality.

Key words: Cereals， flour， quality， FT-IR spectroscopy， PCA.

1. Introduction

Cereals play the main role in the agricultural production of the majority of countries. This fact is connected first of all with the importance of cereals in nutrition. The greatest part of wheat and rye is used for bread and bakery products in Northern， Central and Eastern Europe and they contribute to an important source of protein and dietary fiber in the diet as well as in the Czech Republic. Wheat is the most important crop for breadmaking because of its supreme baking performance in comparison with all other cereals. Only wheat proteins can make the three-dimensional network (gluten structure) of wheat dough during mixing and kneading of dough. However， wheat is lower in dietary fiber content and the nutritive value of bread could be increased by a supplementation of rye and barley or an addition of isolated dietary fiber into the bread formula [1-3]. However， Hung [4] presented a new kind of whole waxy wheat with higher dietary fiber content than regular whole wheat flour. Among commonly grown cereals， whole grain rye has the highest dietary fiber content [5]. Rye is considered to be a healthy cereal with regard to a number of bioactive compounds such as phenolic acids， lignans and also alkylresorcinols [6]. Recently we have observed a renewed interest in barley for food production [7]. As the latest investigations were accomplished in barley breeding， the new beta-glucan-rich barley for baking was developed [8]. Hull-less cultivars of barley have better nutritional value than hulled ones with regards to higher protein and soluble dietary fiber content. A hull-less barley flour was incorporated into white and wholegrain wheat bread and the bread showed acceptable and desirable nutritional and sensory properties [9].

The main components of cereals are carbohydrates(unavailable: non-starch polysaccharides， dietary fiber

and available: starch) and proteins. Starch is a major food reserve providing a bulk nutrient and energy source with high glycemic response in the human diet[10]. The content of starch in a cereal grain varies but generally it is between 60% and 75% of the weight of the grain. During cereal processing and grain milling in particular， the content of damaged starch is raised in the flour and can influence the technological quality of flour and handling of dough. Starch granule size distribution is an important factor that affects the quality of final cereal products. The effects of wheat starch granules size distribution were observed on mixing and breadmaking quality [11]. The determination of total or damaged starch can be carried out by chemical end group analysis or modern enzymatic methods. Determination of starch content by hydrochloric acid dissolution consists of break-down of starch in acid and measuring of the optical rotation of formed products in solution. The determination is more exacting and Carrez solutions(one of them contains cyanide) are necessary to protein precipitate. Measurement of total or damaged starch by enzymatic kit is rapid， easy but expensive.

The content of proteins in the fully-grown grains varies from 8% to 15% in dry matter. Dominant part of proteins is stored in endosperm and aleuronic layer of cereal grain. Cereal proteins have a high content of glutamine and proline and a very low content of essential amino acids as lysine and threonine. The earliest classification of cereal storage proteins is based on their solubility properties and it is often called Osborne fractionation [12]. Albumins and globulins belong to water-soluble fractions with low molecular weight and especially have the nutritive importance. Gliadins (prolamins) and glutelins have higher molecular weight (from 30 kDa to 20 MDa) and they are extracted in alcohol-water mixture and alkaline-water mixture， respectively. The ratio between high and low molecular weight gluten fractions is predominant for baking performance. Therefore， it seems that the greater the content of large molecular weight glutenin subunits， the larger the glutenin polymers and the stronger the flour [13]. Tatham [14] published the up-to-date review of wheat， barley and rye prolamins structure， physical chemistry and their functional properties. Protein in flour can be determined chemically by the Kjeldahl method， but the procedure is very complex. The indirect test by near-infrared spectroscopy (NIR) is very widely used in the milling industry but calibration should be carrying out carefully. The particular protein fractions can be separated by liquid chromatography with reverse phase and UV detection. The baking quality of gluten can be expressed by degree of sedimentation(according to Zeleny) of flour suspended in a lactic acid solution during standard time interval.

Dietary fiber is the edible part of the plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine[15]. Detailed medical experiments indicated [16， 17] that dietary fiber can stimulate weakening of hunger， stimulating peristaltic movements， reducing the level of blood glucose， regulating the activity of microbial flora， lowering of cholesterol blood serum level and decreasing of the risk of civilization diseases [18].

Dietary fiber can be classified into water-soluble(SDF) and water-insoluble dietary fiber (IDF) according to their water solubility. The significant components of cereal water-soluble fiber are ?-glucans， arabinoxylans， galactomannans， fructans and arabinomannans which can form viscous solutions. Water-insoluble dietary fiber consists of cellulose， hemicelluloses and lignin primarily. Lignin is a lipophilic phenolic polymer that can absorb bile acid [3]. The content of ?-glucans and fiber is determined mostly enzymatically. Determination of fibre content is time consuming and expensive(enzyme assay kit， reagents).

Original gravimetric， enzymatic and chemical methods of analysis were not capable to determine reproducibly and quickly the properties and constituents of grain mixtures. On the other hand，

vibrational spectra have recently found their importance in qualitative food analysis [19]. Mid infrared spectroscopy in the wavenumber range 4，000-400 cm-1 is a rapid， sensitive and versatile tool for elucidating the structure and physical properties of starch [20] and other carbohydrates [21]. The most important strong absorptions for starch are at 1，150， 1，075 and 1，015 cm-1 assigning the bending vibration of (CO) groups， and medium absorptions at 845 cm-1 assigning the bending vibration (C1-H) of ?-anomer [20， 22].

Proteins have several strong absorptions in infrared region due to the presence of peptide bond CO-NH. The strongest are stretching vibration of (N-H) groups at wavenumber 3，300-3，200 cm-1 (Amide A)， stretching vibration of (C = O) at 1，690-1，620 cm-1(Amide I)， bending vibration of ?(N-H) (Amide II) at 1，550-1，500 cm-1 and bending vibration of(N-H)/(C-H) at 1，300-1，200 cm-1 (Amide III) [23].

Absorbance of specific peaks in the mid infrared spectrum can be correlated with particular cell wall molecules: cellulose 1，162， 1，120， 1，059， 1，033， 930 and 898 cm-1; ?-glucan 1，151， 1，140， 1，076， 1，041， 1，026， 916 and 840 cm-1; arabinoxylans 1，166 and 998 cm-1; glucomannan 1，150， 1，092， 1，064， 1，034， 941， 898， 872 and 814 cm-1; and arabinogalactan 1，139， 1，078， 1，043， 985， 880 and 842 cm-1 [24-26]. The characteristic wavenumbers for cell wall non-starch polysaccharides were selected on the basis of the application of chemometric analysis [24]. It was also proved to be useful for a quick evaluation of polysaccharides used as additives in foodstuffs [27].

The aim of this work was to determine the quality of selected flours using several analytical methods to find the relationship among flour quality parameters. The set of Czech and Moravian wheat， barley and rye flours and their blends were analyzed and their qualitative parameters， such as content of moisture， ash， protein and starch， protein fractions， value of sedimentation Zeleny test， solvent retention capacity profile， gluten index， content of soluble， insoluble and total dietary fiber and ?-glucans， were determined. Fourier transform-infrared spectroscopy and principal component analysis were applied to correlate various nutritional and breadmaking parameters.

2. Materials and Methods

2.1 Sample Characterization

Totally 34 samples of commercial flours from wheat (Triticum aestivum) (winter)， barley (Hordeum vulgare) (2-rowed， spring， hull-less) and rye (Secale cereale) were analyzed. 7 samples of wheat flours growing in 2010 in different Czech regions， 12 samples of wheat flours growing in 2010 in different regions of Moravia， 3 samples of barley flours (Czech region， 2010 crop)， 1 sample of bar1ey bran (Czech region， 2010 crop)， 1 sample of rye flour (Czech region， 2010 crop) and 10 samples of flours blends were used as experimental materials (Table 1). The blends were prepared by mixing in various proportions of cereals (20%， 30%， 40%， 50% and 60% portions of barley to wheat; and blends wheat:rye:barley 30%:10%:60%， 25%:15%:60% and 20%:20%:60%). Samples no. 15 and 16 were wheat flours for biscuits and cookies， samples no. 17 and 18 were blends wheat-rye flours for bread and bakery production. Samples no. 19-34 were wheat flours for bread production. All flours were sieved through a 0.8 mm sieve.

2.2 Chemical Analysis

Moisture content was determined by drying at 105 °C to constant weight [28]. Ash content was determined by burning the samples at 925 °C to constant weight [28]. The soluble， insoluble and total dietary fiber content was determined according to the method AOAC 985.29 [29] combined with total dietary fiber assay kit K-TDFR (Megazyme International Ireland Ltd.， Wicklow， Ireland). The content of mixed linkage (1→3)(1→4)-?-D-glucans was determined according to the AACC Method 32-23 [30] combined with McCleary method assay procedure K-BGLU (Megazyme International Ireland

3. Results and Discussions

3.1 Breadmaking Characteristics of Flours

The higher content of ash had barley bran (3.8%) and blends (1.1%) (all values are related to dry matter)(Table 2). The content of total starch was determined from 62% to 73%. The average content of protein in flours was 12.7%， whereas the highest content of protein (15.2%) was found in sample no. 25 (wheat Moravian flour) and the lowest content (7.5%) was in sample no. 17 (wheat: rye Czech flour). The samples of Czech flours (samples no. 19 to 22) had higher content of protein in comparison to samples of Moravian flours (samples no. 23 to 34). The values of GI， Zeleny sedimentation and SRC of lactic acid(expression of glutelins quality) were not significantly distinct for wheat Czech and Moravian flours. An

addition of barley and rye to wheat flour caused a decrease of protein content in blends (decrease of value of Zeleny test and gluten index) and pronounced deterioration of breadmaking quality of flours. Wheat flours for bread production showed the higher content of gluten (Zeleny test， SRC of lactic acid) in comparison with blends. Wheat flours and blends did not show different value of gluten index.

Solvent retention profile of selected flours and their blends is showed in Fig. 1. The value of SRC of lactic acid characterized the high content of glutenins (high molecular fraction of gluten) in wheat flours and the low content of hordenins in barley flours (Table 2). The highest content of protein， glutenin (determined by

SRC of lactic acid) and glutenin fraction was determined in wheat Czech flour (sample no. 1). The content of glutelin decreased both in wheat and barley blends (samples no. 1 to 5) and in wheat， barley and rye blends (samples no. 7， 8 and 9). It corresponded to the decrease of protein content determined by Kjeldahl. The mentioned tendency corresponds to the results of fractionation (especially the content of glutelins).

The increased value of SRC of sucrose indicated higher content of arabinoxylans in rye (sample no. 14) and barley flour (sample no. 12). An addition of barley and rye to wheat flour resulted in increase of nutrition value of blends. The rye flour had higher value of SRC of sodium carbonate; it can mean more damaged starch and higher water absorption. An addition of barley and rye to wheat flours increased the value of SRC of sodium carbonate in blends. The rye flour had the highest value of SRC of water. The highest of water absorption was caused by the present of water-soluble components (?-glucans and arabinoxylans). On the contrary wheat flours had the lowest water absorption (low value of SRC of water). 3.2 Nutritional Characteristics of Flours

Generally， wheat flours had the lowest content of dietary fiber and ?-glucans (Table 3). An addition of barley or rye increased the content of fiber and?-glucans in blends. Brennan [5] and Rakha [18] described that the content of ?-glucans is about 1% in wheat grains， 1%-2% in rye and 5%-11% in barley. In our case， barley flour contained from 2.5% of?-glucan (sample no. 10) to 4.2% (sample no. 13). The highest content of total dietary fiber had blended flours (samples no. 6-9)， barley flour (sample no. 13) and rye flour (sample no. 14). The insoluble dietary fiber involved a predominant part of total fiber.

The portion of protein fractions of Czech flours and blends were not significantly different (Table 3). Only， rye flour (sample no. 14) had evidently higher content of albumins and globulins in comparison with other cereals. The most often published wheat and barley protein fraction proportions are 20%-25%， 40%-50%，

and 35%-40% for albumins and globulins， gliadins and glutenins， respectively [12]. Different fraction proportion is showed in rye: albumins 44%， globulins 10%， gliadins 21% and glutelins 25%. Some Moravian flours came from same place of origin (e.g. samples no. 23-25， or samples no. 29-31) and they had comparable contents of protein fractions. The higher content of glutenins and the lowest content of gliadins were found in samples no. 29， 30 and 31. The content of glutelins decreased in blends in accordance with a decrease of total protein content determined by Kjeldahl.

Statistically significant positive correlations were observed between ?-glucan and protein (r = 0.85， P < 0.05)， ?-glucan and SRC of sucrose (r = 0.93， P < 0.05)， between ?-glucan and soluble dietary fiber (r = 0.88， P < 0.05)， and ?-glucan and gluten value of Zeleny test (r = 0.81， P < 0.05). A strong positive correlation between the content of ?-glucan and protein and between ?-glucan and soluble fiber was confirmed with the results obtained by Holtekj?len[33]. Positive correlations were found between soluble dietary fiber and SRC of water (r = 0.95， P < 0.05)， between proteins and total dietary fiber (r = 0.88， P < 0.05)， and SRC of lactic acid and gluten value of

Zeleny test (r = 0.70， P < 0.05). Significant negative correlations were observed between content of ?-glucan and starch (r = -0.69， P < 0.05) and between proteins and starch (r = -0.83， P < 0.05).

3.3 FT-IR Spectroscopy and Principal Component Analysis

The transmission FT-IR spectra of flours and blends were recorded. The characteristic region of starch， non-starch polysaccharides and protein absorption was observed. PCA was used on IR data and PCA score allowed to separate the flours and their blends according to the content of starch and non-starch polysaccharides， especially ?-glucan and fiber content. The flours were separated to three clusters (wheat， blends， barley and rye) (Fig. 2).

The application of a PCA to the FT-IR spectra in the mid-infrared region was effective for fast distinction of various different types of flours on the basis of nutritional and breadmaking flour parameters.

4. Conclusions

An addition of barley or rye to wheat flour influenced the quality of flour blends significantly. The content of nutritive and healthy components(soluble proteins， fiber， ?-glucans and pentosans) was increased in blends， but the breadmaking quality decreased (higher content of damaged starch， higher water capacity and sticky dough).

FT-IR spectroscopy and chemometric analysis(PCA analysis) can be used to a fast screening of the cereal flour quality and to classification of flours on the basis the specific purpose of their uses.

Acknowledgments

This work was supported by the Ministry of Education， Youth and Sport of the Czech Republic (project No 321141615) and project New Food No QI111B053. The authors are grateful for the technical support from the Zeelandia Company (Mal?ice， Czech Republic).

References

[1] M.H. Alu′datt， T. Rababah， K. Ereifej， I. Alli， M.A. Alrababah， A. Almajwal， et al.， Effect of barley flour and barley protein isolate on chemical， functional， nutritional and biological properties of Pita bread， Food Hydrocolloids 26 (1) (2012) 135-143.

[2] D. Peressini， A. Sensidoni， Effect of soluble dietary fiber addition on rheological and breadmaking properties of wheat doughs， Journal of Cereal Science 49 (2) (2009) 190-201.

[3] S. Ragaee， I. Guzar， N. Dhull， K. Seetharaman， Effects of fiber addition on antioxidant capacity and nutritional

quality of wheat bread， LWT-Food Science and Technology 44 (10) (2011) 2147-2153.

[4] P. Van Hung， T. Maeda， M. Fujita， N. Morita， Dough properties and breadmaking qualities of whole waxy wheat flour and effects of additional enzymes， Journal of the Science of Food and Agriculture 87 (13) (2007) 2538-2543.

[5] A. Rakha， P. ?man， R. Andersson， Characterization of dietary fiber components in rye products， Food Chemistry 119 (3) (2010) 859-867.

[6] I. Bondia-Pons， A.M. Aura， S. Vuorela， M. Kolehmainen， H. Mykk?nen， K. Poutanen， Rye phenolics in nutrition and health， Journal of Cereal Science 49 (3) (2009) 323-336.

[7] B.K. Baik， S.E. Ullrich， Barley for food: Characteristics， improvement， and renewed interest， Journal of Cereal Science 48 (2) (2008) 233-242.

[8] K. Dieckmann， beta BARLEY-the new beta-glucan rich barley for baking and more， Baking+Biscuit International 1 (2011) 58-63.

[9] B. ?krbi?， S. Milovac， D. Dodig， B. Filip?ev， Effects of hull-less barley flour and flakes on bread nutritional composition and sensory properties， Food Chemistry 115(3) (2009) 982-988.

[10] K. Dewettinck， F. Van Bockstaele， B. K?hne， D. Van de Walle， T.M. Courtens， X. Gellynck， Nutritional value of bread: Influence of processing， food interaction and consumer perception， Journal of Cereal Science 48 (2)(2008) 243-257.

[11] S.H. Park， J.D. Wilson， B.W. Seabourn， Starch granule size distribution of hard red winter and hard red spring wheat: Its effects on mixing and breadmaking quality， Journal of Cereal Science 49 (1) (2009) 98-105.

[12] T.B. Osborne， Proteins of the wheat kernel， Carnegie Inst. Washington， USA， 1907.

[13] W. Wang， K. Khan， Effect of the molecular weight distribution of glutenin protein from extra-strong wheat flour on rheological and breadmaking properties through reconstitution studies， Cereal Chemistry 86 (6) (2009) 623-632.

[14] A.S. Tatham， P.R. Shewry， The S-poor prolamins of wheat， barley and rye: Revisited， Journal of Cereal Science 55 (2) (2012) 79-99.

[15] AACC Report， Report of the dietary fiber definition committee to the board of directors of the American Association of Cereal Chemists， St. Paul， Minnesota， USA， 2001.

[16] H. Salovaara， T. Sontag-Strohm， H. Antilla， Physical state of soluble oat fiber and health claims， in: H. Salovaara， F. Gates， M. Tenkanen (Eds.)， Dietary Fiber-components and functions， Wageningen Academic Publishers， The Netherlands， 2007， pp. 91-112.

[17] P.J. Wood， Cereal ?-glucans in diet and health， Journal of Cereal Science 46 (3) (2007) 230-238.

[18] Ch.S. Brennan， L.J. Cleary， The potential use of(1→3)(1→4)-?-D-glucans as functional food ingredients， Journal of Cereal Science 42 (1) (2005) 1-13.

[19] M. Mathlouthi， J.L. Koenig， Vibrational spectra of carbohydrates， Advances in Carbohydrate Chemistry and Biochemistry 44 (1986) 17-19， 22-23.

[20] A. Ga?at， Study of the Raman scattering and infrared absorption spectra of branched polysaccharides， Acta Biochimica Polonica 27 (1980) 135-141.

[21] M. Ka?uráková， R.H. Wilson， Developments in mid-infrared FT-IR spectroscopy of selected carbohydrates， Carbohydrate Polymers 44 (4) (2001) 291-303.

[22] N. Dupuy， C. Wojciechowski， C.D. Ta， J.P. Huvenne， P. Legrand， Mid-infrared spectroscopy and chemometrics in corn starch classification， Journal of Molecular Structure 410-411 (1997) 551-554.

[23] P.R. Shewry， A.S. Tatham， P. Lazzeri， Biotechnology of wheat quality， Journal of the Science of Food and Agriculture 73 (4) (1997) 397-406.

[24] M.A. Coimbra， A. Barros， M. Barros， D.N. Rutledge， I. Delgadillo， Multivariate analysis of uronic acid and neutral sugars in whole pectic samples by FT-IR spectroscopy， Carbohydrate Polymers 37 (3) (1998) 241-248.

[25] M. Ka?uráková， P. Capek， V. Sasinková， N. Wellner， A. Ebringerová， FT-IR study of plant cell wall model compounds: Pectic polysaccharides and hemicelluloses， Carbohydrate Polymers 43 (2) (2000) 195-203.

[26] R. Sun， J.M. Fang， A. Goodwin， J.M. Lawther， A.J. Bolton， Fractionation and characterization of polysaccharides from abaca fibre， Carbohydrate Polymers 37 (4) (1998) 351-359.

[27] M. Cerna， A.S. Barros， A. Nunes， S.M. Rocha， I. Delgadillo， J. Copikova， et al.， Use of FT-IR spectroscopy as a tool for the analysis of polysaccharide food additives， Carbohydrate Polymers 51 (4) (2003) 383-389.

[28] ICC， Standards Methods， International Association for Cereal Science and Technology， 6th ed.， Vienna， Austria， 1996.

[29] AOAC， Official Methods of Analysis， Association of Official Analytical Chemists， 15th ed.， Washington， USA， 1990.

[30] AACC， Approved Methods of the American Association of Cereal Chemists， 10th ed.， St. Paul， Minnesota， USA， 2000.

[31] I. Michalík， Unified method for discontinual fractionation of cereal grain protein complex， Agriculture 48 (7) (1992) 333-341.

[32] ISO， International Standards， International Organization for Standardization， Geneva， Switzerland， 2007.

[33] A.K. Holtekj?len， A.K. Uhlen， E. Br?then， S. Sahlstr?m， S.H. Knutsen， Content of starch and non-starch polysaccharides in barley varieties of different origin， Food Chemistry 94 (3) (2006) 348-358.