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Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
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Flour and Bread from Black-, Purple-, and Blue-Colored Wheats Wende Li, Trust Beta Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada
CHAPTER OUTLINE List of Abbreviations 59 Introduction 59 Quality and Traits 60 Antioxidant Properties 62 Technological Issues 65
Problems of quality and technical processes 65 Adverse reactions 66
Summary Points 66 References 66
LIST OF ABBREVIATIONS BGW 76 Black-grained wheat 76 DPPHl 2,2-Diphenyl-1-picryhydrazyl free radical HMW-glu High-molecular-weight glutenin IVPD In vitro protein digestibility MPT Midline peak time ORAC Oxygen radical absorbance capacity PWB Purple wheat bread SDS Sodium dodecyl sulfate WWB Whole wheat bread WFB White flour bread
INTRODUCTION Wheat is one of the most important grains in our daily diets. In recent years, bioactive compounds in wheat have attracted increasingly more interest from both researchers and food manufacturers because of their benefits in promoting health and preventing disease. For example, wheat bran extracts significantly inhibited lipid peroxidation in human low-density lipoprotein in vitro (Yu et al., 2005). Wheat with high levels of antioxidant activity has the potential for value-added use, particularly in the formulation of functional foods. Flour and Breads and their Fortification in Health and Disease Prevention. DOI: 10.1016/B978-0-12-380886-8.10006-6 Copyright Ó 2011 Elsevier Inc. All rights reserved.
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Unlike red and white wheats, blue-, purple-, and black-colored wheats contain natural anthocyanin compounds. The role of anthocyanin pigments as medical agents has been wellaccepted dogma in folk medicine throughout the world, and in fact these pigments are linked to an amazingly broad-based range of health benefits (Lila, 2004). Based on the potential of these colorful-grained wheats, several functional foods have been developed from these wheats in recent years, including purple wheat bran muffin (Li et al., 2007a) and antho-beer made from purple-grained wheat (Li et al., 2007b), soy sauce (Li et al., 2004), vinegar, breakfast cereal and instant noodles produced from black-grained wheat, and fine dried noodles made from blue-grained wheat (Pei et al., 2002).
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Neither blue- nor purple-colored wheat pigmentation originated in common wheat (Knievel et al., 2009). Knott (1958) found the blue seed color of blue-colored wheat to be inherited from Agropyron chromosome additions or substitutions into common wheat rather than a natural occurrence among common wheat species. Zeven (1991) reported that the blue aleurone trait was introgressed into common wheat from blue pigmented Triticum boeoticum, Agropyron tricholphorum, Agropyron glaucum, and, most frequently, from Agropyron elongatum. For example, blue-colored wheat cultivar Leymus dasystachys, which is related to the Agropyron genus, was crossed with common wheat to produce blue-colored wheat (Zeven, 1991). Purplecolored wheat was discovered in tetraploid durum, Triticum dicoccum, in east African areas such as Ethiopia, and it was introgressed into common wheat (Zeven, 1991). Copp (1965) reported that a stable hexaploid wheat with purple grain color was obtained from the cross Triticum dicoccum var. Arraseita Perc. Triticum aestivum L., and its purple grain color was as intense as that in the original tetraploid purple-colored wheat. Above “Triticum dicoccum var. Arraseita Perc.” was purple tetraploid wheat from Abyssinia, with the purple pericarp color being inherited as a monofactorial dominant character in tetraploid wheats (Sharman, 1958). Above “Triticum aestivum L.” was commercial hexaploid wheat (Copp, 1965). The breeding process of black-grained wheat cultivar was as follows (Sun et al., 1999). A blue-grained hexaploid wheat (allo substitution line “blue 1”) was first bred by scientists from Shanxi Academy of Agricultural Science in the 1970s, and then through the breeding effort of 20 years, the scientists bred a purple-grained hexaploid wheat (“purple 12-1”), a blueepurple-grained hexaploid wheat (“blueepurple 114”), and a black-grained hexaploid wheat (“black 76”). The blue 1 was bred by crossing common hexaploid wheat (Triticum aesticum) with Agropyron glaucum. Purple 12-1 was bred by crossing common hexaploid wheat (T. aesticum) with Elymus dasystachys. However, blueepurple 114 was bred by crossing blue 1 with purple-grained tetraploid wheat. Finally, black 76 was bred by crossing blueepurple 114 used as the female parent with purple 12-1 as the male parent. Another purple-grained wheat (T. aestivum) cultivar was UM 606a (Hard Federation//Chinese Sping/Nero/3/3) Pitic 62) (Dedio et al., 1972), derived from the crosses of “Chinese Spring” with the purple T. durum cultivar “Nero” (Piech and Evans, 1979). In bread wheats (T. aesticum), white and red wheats are common, but purple- and blue-colored wheats are rare (Zeven, 1991). Researchers reported on purple-colored bread wheat accessions that had cultivars K-49990, K-55583, and K-59158, derived from the crosses of common bread wheats by “T. aethiopicum” (purple-colored tetraploid wheat from Ethiopia) (Zeven, 1991). Although pigments exist in wheat grains at very low concentrations, they substantially influence the quality of wheat products such as bread, pasta, and noodles (Abdel-Aal and Hucl, 2003). Because of the colorful appearance of black, blue, and purple wheat grains, they are currently produced only in small amounts for making specialty foods (Abdel-Aal et al., 2006). However, it is useful to understand the antioxidant properties, qualities, and traits of these colored wheat grains in order to increase their production and use.
QUALITY AND TRAITS Sun et al. (1999) reported on the nutritive composition of black-grained wheat 76 (BGW 76) and the common wheat, Jinchun 9. For example, their nutrient composition was as follows:
CHAPTER 6 Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
crude protein, 20.50% in BGW 76 and 12.90% in Jinchun 9; lipid, 1.60% in BGW 76 and Jinchun 9; carbohydrate, 62.10% in BGW 76 and 71.90% in Jinchun 9; crude fiber, 2.40% in BGW 76 and 2.10% in Jinchun 9; ash, 1.90% in BGW 76 and Jinchun 9; vitamin K, 11.47 mg/kg in BGW 76 and 7.01 mg/kg in Jinchun 9; calcium, 0.56 g/kg in BGW 76 and 0.14 g/ kg in Jinchun 9; phosphorus, 4.10 g/kg in BGW 76 and 2.41 g/kg in Jinchun 9; and selenium, 1.04 mg/kg in BGW 76 and 0.26 mg/kg in Jinchun 9. Compared with Jinchun 9, levels of crude protein, crude fiber, vitamin K, calcium, phosphorus, and selenium in BGW 76 were increased by 58.91, 14.29, 63.62, 300, 70.12, and 300%, respectively (Sun et al., 1999). In comparison with common bread wheats, Klasic (hard white wheat), Yecora Rojo (red grain wheat), and Glenlea (Canadian hard red spring wheat), crude protein, ash, and lipid were 17.71, 2.29, and 2.59% in the wholemeal of black-grained wheat; 14.07, 1.62, and 2.52% in the wholemeal of bread wheat Klasic; 13.67, 1.64, and 2.03% in the wholemeal of bread wheat Yecora Rojo; and 14.52, 1.88, and 2.89% in the wholemeal of bread wheat Glenlea, respectively (Li et al., 2004). The flour produced from black-grained wheat also showed the highest crude protein content in comparison with flours prepared from bread wheats Klasic, Yecora Rojo, or Glenlea. The nutritive composition of flour from black-grained wheat and bread wheats Klasic, Yecora Rojo, and Glenlea, respectively, was as follows: crude protein, 18.26, 13.76, 12.59, and 14.23%; ash, 0.95, 0.74, 0.70, and 0.96%; lipid, 1.56, 1.84, 1.31, and 2.18%; and carbohydrate, 75.03, 77.73, 79.32, and 76.03% (Li et al., 2004). Bean et al. (1990) reported that protein content ranged from 8.1 to 14.0% in the wholemeal of bread wheat Klasic and averaged 9.5% in its flour. The protein and ash contents were 14.2e15.7 and 1.55e1.64%, respectively, in the wholemeal of bread wheat Yecora Rojo, and they were 12.9e15.1 and 0.64e0.68% in its flour, respectively (Al-Mashhadi et al., 1989). Campbell (1970) reported that high protein content in grain seed was associated with dark seed color and shattering. Color determination indicated that black-grained wheat had low L) value compared with bread wheats Klasic, Yecora Rojo, or Glenlea (Li et al., 2004). The L) value is an indicator of the degree of whiteness; for example, the L) value was 98.04 for the white body reference and 34.51 for the black body reference. The L) values of seed, bran, wholemeal, and flour were 38.04, 62.66, 81.74, and 97.34 for black-grained wheat; 64.46, 71.95, 94.69, and 100.77 for bread wheat Klasic; 57.94, 71.95, 90.99, and 100.77 for bread wheat Yecora Rojo; and 55.77, 71.99, 89.39, and 97.90 for bread wheat Glenlea, respectively (Li et al., 2004). Because the L) value (38.04) of black-grained wheat was very similar to the L) value (34.51) of the black body reference, the seed color of black-grained wheat was also visually black. The high crude protein content of black-grained wheat appears to be correlated to its black (deep purple) seed color. The bread making quality of wheat is largely determined by the quantity and quality of the storage proteins of the grain endosperm or prolamins (Wall, 1979). Prolamins consist of glutenins and gliadins. Payne et al. (1987) reported on the effects of glutenin subunits and gliadins on bread making quality. It is important to fully understand protein properties of blue-, purple-, and black-colored wheats in order to predict their potential uses. Li et al. (2006) reported protein characteristics of black-grained wheat, three common bread wheatsdKlasic, Yecora Rojo, and Glenleadand the common steamed-bread wheat Taifeng. For example, sodium dodecyl sulfate (SDS) sedimentation values of their whole meals decreased in the order bread wheat Glenlea (16.9 ml/g) > bread wheat Klasic (16.5 ml/g) > bread wheat Yecora Rojo (15.0 ml/g) > black-grained wheat (13.3 ml/g) > steamed-bread wheat Taifeng (9.9 ml/g) (Li et al., 2006). The high SDS sedimentation value was associated with strong gluten strength because the SDS sedimentation value had a positive correlation with gluten strength (Dick and Quick, 1983). Gluten index decreased in the order Glenlea (99.37%) > Yecora Rojo (98.88%) > Klasic (98.66%) > black-grained wheat (69.74%) > Taifeng (50.09%) (Li et al., 2006). Therefore, low gluten index value indicated poor strength of wet gluten dough because there was a positive correlation coefficient (R ¼ 0.9606) between gluten
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index and SDS sedimentation value (Li et al., 1998). For bread making, the optimum gluten index range is between 60 and 90 (Perten, 1990), and the gluten index value (69.74%) of black-grained wheat fell in the optimum gluten index range. Mixograph curves and parameters derived from the curves are also useful tools for indicating good or poor gluten strength of different wheat cultivars. For example, the mixograph parameter midline peak time (MPT) shows the best correlation with gluten strength. A low MPT value is an indication of weak gluten strength. The MPT values of wheat flours in water decreased in the order Glenlea (6.27 min) > Yecora Rojo (6.11 min) > Klasic (5.41 min) > black-grained wheat (2.93 min) > Taifeng (2.26 min) (Li et al., 2006). The order of their MPT values was similar to that of their gluten index. MPT values also indicated that gluten strength of black-grained wheat flour was stronger than that of Taifeng wheat flour, but obviously it was weaker than that of bread wheat flours Klasic, Yecora Rojo, and Glenlea.
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In the case of pepsin, in vitro protein digestibility (IVPD) of whole meal and gluten at 24 h was 82.42 and 96.45% for black-grained wheat, 82.94 and 95.07% for steamed-bread wheat Taifeng, 87.23 and 95.42% for bread wheat Klasic, 84.43 and 95.37% for bread wheat Recora Rojo, and 84.04 and 94.62% for bread wheat Glenlea, respectively (Li et al., 2006). The wholemeal of Klasic had significantly higher IVPD (p < 0.05) than that of black-grained wheat, Taifeng, Yecora Rojo, and Glenlea, but there were no significant differences (p < 0.05) in IVPD among their glutens. Total essential amino acid and total amino acid were 4.23 and 15.54% in the flour of black-grained wheat, 3.48 and 13.13% in Taifeng flour, 3.10 and 11.63% in Klasic flour, 2.74 and 10.17% in Yecora Rojo flour, and 3.26 and 12.10% in Glenlea flour, respectively (Li et al., 2006). The increase in total essential amino acid in the flour of black-grained wheat was up to 21.55, 36.45, 54.38, and 29.75% higher than that in the flours of Taifeng, Klasic, Yecora Rojo, and Glenlea, respectively. Similarly, the increase in total amino acid in the flour of black-grained wheat was up to 18.35, 33.62, 52.80, and 28.43% higher than that in the flours of Taifeng, Klasic, Yecora Rojo, and Glenlea, respectively. High total amino acid content in the flour of black-grained wheat was associated with its high crude protein content. Dough stickiness values of flours decreased in the order steamed-bread wheat Taifeng (392.75 g) > bread wheat Yecora Rojo (313.05 g) > black-grained wheat (223.76 g) > bread wheat Klasic (186.01 g) > bread wheat Glenlea (182.67 g) (Li et al., 2006). A high dough stickiness value indicates stickier dough. Bakery characteristics are poor if the dough is too sticky. The flour from black-grained wheat had better baking properties than that obtained from Taifeng and Yecora Rojo, but its dough stickiness was somewhat stickier than that of flours from Klasic and Glenlea. The baking quality of wheat cultivars can be predicted according to their high-molecular-weight glutenin (HMW-glu) subunits. For example, Taifeng has HMW-glu subunits similar to Anza (2 þ 12 and 7 þ 8 subunits), Klasic has HMW-glu subunits similar to Yecora Rojo (1, 17 þ 18, and 5 þ 10 subunits), and black-grained wheat has HMW-glu subunits similar to Glenlea (2), 7 þ 8, and 5 þ 10 subunits) (Li et al., 2006). Because good baking quality is strongly correlated with the presence of 1 and 5 þ 10 or 2) and 5 þ 10 HMW-glu subunits and poor baking quality is usually associated with 2 þ 12 HMW-glu subunits, the HMW-glu subunits (2) and 5 þ 10) in black-grained wheat predict that blackgrained wheat can be classified as bread wheat (Li et al., 2006).
ANTIOXIDANT PROPERTIES Purple wheat flour bread (PWB) and two bread controls, whole wheat meal bread (WWB) and white flour bread (WFB), were prepared according to the method described by Ge´linas and McKinnon (2006), and their antioxidant properties were evaluated. Their 2,2-diphenyl1-picryhydrazyl free radical (DPPHl) scavenging activity and kinetics are shown in Table 6.1 and Figure 6.1, respectively. Purple wheat bread PWB had the highest DPPHl scavenging activity (47.58%) at 60 min compared to wholemeal bread WWB (34.06%) and white
CHAPTER 6 Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
TABLE 6.1 Free Radical Scavenging Activity of Bread Extracts Reacting with DPPHl (at 60 min)a Bread
DPPHl Scavenging (%)
Whole wheat meal bread Wheat white flour bread Purple wheat flour bread
34.06 32.20 47.58
Source: Reprinted from our unpublished data. a Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. DPPHl scavenging activity was determined according Li et al. (2007a). Results are expressed as mean, n ¼ 2.
DPPH radical scavenging (%)
50
40
30
20 Whole wheat meal bread 10
Wheat white flour bread Purple wheat flour bread
0 0
10
20
30
40
50
60
Reaction time (min)
63 FIGURE 6.1 Radical scavenging activity kinetics of bread extracts reacting with DPPHl for 60 min. Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. DPPHl scavenging activity was determined according to Li et al. (2007a). Results are expressed as mean, n ¼ 2. Source: Reprinted from our unpublished data.
bread WFB (32.20%). The DPPHl scavenging activity from kinetics curve was also in the order PWB > WWB > WFB (see Figure 6.1). The DPPHl scavenging activity of whole meal in several wheat genotypes was 33.51% for black-grained wheat, 25.57% for purple-grained wheat, 23.66% for blue-grained wheat, and 25.40 % for white-grained wheat (Li et al., 2005). The oxygen radical absorbance capacity (ORAC) of three bread extracts decreased in the same order PWB (12.09 g/kg) > WWB (10.64 g/kg) > WFB (8.88 g/kg) as that of DPPHl scavenging activity (Table 6.2). A high ORAC value is an indication of high antioxidant capacity in sample extract. Total anthocyanin content in PWB was 78 mg/kg (Table 6.3). Anthocyanin was not detectable in WWB and WFB. Anthocyanins are members of the bioflavonoid phytochemicals, which have been recognized to have health-enhancing benefits due to their antioxidant activity and anti-inflammatory and anticancer effects (Abdel-Aal et al., 2006). The total anthocyanin content of bran, wholemeal, and flour ranged between 415.9e479.7, 139.3e163.9, and 18.5e23.1 mg/kg in blue-grained wheat; 156.7e383.2, 61.3e153.3, and 3.1e14.3 mg/kg in purple-grained wheat; and 9.9e10.3, 4.9e5.3, and 1.5e1.7 mg/kg in red-grained wheat, respectively (Abdel-Aal and Hucl, 2003). Siebenhandl et al. (2007) reported total anthocyanin contents of 225.8 and 17.0 mg/kg in the bran and flour of bluegrained wheat and 34.0 and 8.2 mg/kg in the wholemeal and flour of purple-grained wheat, respectively. Hosseinian et al. (2008) reported total anthocyanin contents of 500.6 mg/kg in normal purple-grained wheat and 526.0 mg/kg in heat-stressed purple-grained
SECTION 1 Flour and Breads
TABLE 6.2 ORAC Values of Bread Extracts Reacting with 2,20 -Azobis (2-Methylpropionamide) Dihydrochloridea Bread Whole wheat meal bread Wheat white flour bread Purple wheat flour bread
Equivalent of Trolox (g/kg) 10.64 8.88 12.09
Source: Reprinted from our unpublished data. a Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. ORAC was determined according to Li et al. (2007a). Results are expressed as mean, n ¼ 2.
TABLE 6.3 Total Anthocyanin Content of Bread Extracts Determined Using the pH Differential Methoda Bread Whole wheat meal bread Wheat white flour bread Purple wheat flour bread
Equivalent of Cyanidin 3-Glucoside (mg/kg) Not detectable Not detectable 78
Source: Reprinted from our unpublished data. a Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. Total anthocyanin content was determined according to Li et al. (2007a). Results are expressed as mean, n ¼ 2.
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wheat, and they confirmed that cyanidin 3-glucoside was the predominant anthocyanin (103.0 mg/kg) in normal purple-grained wheat. The major anthocyanins were delphinidin 3-glucoside (56.5 mg/kg), delphinidin 3-rutinoside (49.6 mg/kg), cyanidin 3-glucoside (20.3 mg/kg), and cyaniding 3-rutinoside (16.8 mg/kg) in blue-grained wheat (Abdel-Aal et al., 2006) and cyanidin 3-glucoside (19.73e46.44 mg/kg) in purple-grained wheat (Abdel-Aal and Hucl, 2003). Anthocyanins make an important contribution to the antioxidant capacity of black-, purple-, and blue-colored wheats in comparison with that of red and white wheats, which contain only very low levels of anthocyanin (Abdel-Aal and Hucl, 2003). Total phenolic contents of PWB, WWB, and WFB are shown in Table 6.4. PWB showed the highest total phenolic content, and total phenolic contents decreased in the same order of PWB (1111 mg/kg) > WWB (1005 mg/kg) > WFB (515 mg/kg) as that of DPPHl scavenging activity and ORAC. Ge´linas and McKinnon (2006) reported that total phenolic contents (gallic acid equivalent), which ranged from 522 to 866 mg/kg for the wholemeal of organic white wheat varieties, were up to more than 1000 mg/kg for their wholemeal bread and approximately 400 mg/kg for their white bread. Baking slightly increased the level of total phenolic content in bread crust (Ge´linas and McKinnon, 2006), likely due to the Maillard reaction. Total phenolic contents (ferulic acid equivalent) were 1973.5 and 811.6 mg/kg in the wholemeal and flour of purple-grained wheat and 7616.4 and 646.5 mg/kg in the bran and flour of blue-grained wheat, respectively (Siebenhandl et al., 2007). The total phenolic contents (ferulic acid equivalent) of bran and wholemeal were, respectively, 2415 and 1108 mg/kg in black-grained wheat, 2290 and 929 mg/kg in purple-grained wheat, 1416 and 706 mg/kg in blue-grained wheat, and 2215 and 817 mg/kg in white-grained wheat (Li et al., 2005). A high correlation (R ¼ 0.96) was found between total phenolic content and DPPHl scavenging activity for wheat wholemeals (Li et al., 2005). High total phenolic levels are also an indication of high antioxidant capacity. Because there are differences in phenolic content among wheat genotypes, the level of phenolics in bread will be affected by the raw wheat material ingredients used.
CHAPTER 6 Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
TABLE 6.4 Total Phenolic Content of Bread Extracts Determined Using the FolineCiocalteau Methoda Bread
Equivalent of Ferulic Acid (mg/kg)
Whole wheat meal bread Wheat white flour bread Purple wheat flour bread
1005 515 1111
Source: Reprinted from our unpublished data. a Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. Total phenolic content was determined according to Li et al. (2007a). Results are expressed as mean, n ¼ 2.
TABLE 6.5 Phenolic Acid Composition of Breads Determined Using the HPLC Methoda Phenolic acid
WWB (mg/kg)
WFB (mg/kg)
PWB (mg/kg)
Gallic acid Protocatechuic acid p-Hydroxybenzoic acid Vanillic acid Syringic acid m-Coumaric acid Caffeic acid p-Coumaric acid Ferulic acid Sinapinic acid Total phenolic acids
12 Not detectable 5 12 4 2 8 12 250 8 313
12 Not detectable 4 8 8 Not detectable 3 9 65 2 111
13 20 7 18 7 2 15 84 228 9 403
Source: Reprinted from our unpublished data. a Bread (2 g) was hydrolyzed in 60 ml of 4 M NaOH solution at 25oC for 4 h. Phenolic acid composition was determined according to Li et al. (2005f). Results are expressed as mean, n ¼ 2. PWB, purple wheat bread; WFB, white flour bread; WWB, whole wheat bread.
The phenolic acid composition of PWB, WWB, and WFB after hydrolysis is shown in Table 6.5. Ten types of phenolic acid were detected in PWB, 9 types of phenolic acid in WWB, and 8 types of phenolic acid in WFB. Major phenolic acids (>50 mg/kg) were ferulic acid (228 mg/kg) and p-coumaric acid (84 mg/kg) in PWB, ferulic acid (250 mg/kg) in WWB, and ferulic acid (65 mg/kg) in WFB. Total phenolic acids decreased in the same order of PWB (403 mg/kg) > WWB (313 mg/kg) > WFB (111 mg/kg) as that of total phenolic content. PWB had 3.63 and 1.29 times higher total phenolic acids than WFB and WWB, respectively. Siebenhandl et al. (2007) reported that ferulic acid was 851.7 and 180.1 mg/kg in the wholemeal and flour of purplegrained wheat and 3503.3 and 151.1 mg/kg in the bran and flour of blue-grained wheat, vanillic acid 35.1 and 9.9 mg/kg in the wholemeal and flour of purple-grained wheat and 99.8 and 10.1 mg/kg in the bran and flour of blue-grained wheat, and p-coumaric acid 24.3 and 4.6 mg/kg in the wholemeal and flour of purple-grained wheat and 456.6 and 6.3 mg/kg in the bran and flour of blue-grained wheat, respectively. The level of phenolic acids in the wholemeal of soft wheat cultivars ranged from 455.92 to 621.47 mg/kg for ferulic acid, 8.44 to 12.68 mg/kg for vanillic acid, 8.86 to 17.77 mg/kg for syringic acid, and 10.40 to 14.10 mg/kg for p-coumaric acid (Moore et al., 2005). Potential health benefits have been demonstrated for phenolic compounds because of their ability to act as antioxidants (Siebenhandl et al., 2007).
TECHNOLOGICAL ISSUES Problems of quality and technical processes Protein, flour, and dough quality of purple- and blue-colored wheats need to be evaluated for their potential in making bread products. It is important to breed black-, purple-, and
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blue-colored wheats as bread wheat in the future. It is valuable to investigate chemical transformations of phenolic acids and anthocyanins during baking.
Adverse reactions Although very little is known about adverse reactions to black-, purple-, and blue-colored wheats and their food products, known adverse reactions to wheat include allergies and celiac disease. Different clinical forms of wheat allergy include baker’s asthma, atopic eczema/ dermatitis syndrome, urticaria, and wheat-dependent, exercise-induced anaphylaxis.
SUMMARY POINTS l
l
l
l
l
l
l
66 l
Black-grained wheat contains a high crude protein content compared to that of common bread wheats Klasic, Yecora Rojo, and Glenlea. Black-grained wheat can be used as bread wheat for making bread because its HMW-glu subunits (2), 7 þ 8, and 5 þ 10) are similar to those found in the bread wheat Glenlea. Protein quality of black-grained wheat needs to be improved through breeding technology to increase its gluten strength, which is weak compared with that of common bread wheats Klasic, Yecora Rojo, and Glenlea. In addition to containing phenolic acids, black-, purple-, and blue-colored wheats also contain natural anthocyanins, whereas red and white wheats do not. Anthocyanins are important antioxidants and therefore likely to be beneficial in improving health and preventing some diseases. Anthocyanins and phenolic compounds make a major contribution to the antioxidant capacity of black-, purple-, and blue-colored wheats. Purple wheat bread showed the highest antioxidant capacity, with the antioxidant capacity of three bread products decreasing in the order purple wheat bread > whole meal bread > white bread. There is potential to use black-, purple-, and blue-colored wheats as novel ingredient resources for the development of value-added products.
References Abdel-Aal, E.-S. M., & Hucl, P. (2003). Composition and stability of anthocyanins in blue-grained wheat. Journal of Agricultural and Food Chemistry, 51, 2174e2180. Abdel-Aal, E.-S. M., Young, J. C., & Rabalski, I. (2006). Anthocyanin composition in black, blue, pink, purple, and red cereal grains. Journal of Agricultural and Food Chemistry, 54, 4696e4704. Al-Mashhadi, A., Naeem, M., & Bashour, I. (1989). Effect of fertilization on yield and quality of irrigated Yecora Rojo wheat grown in Saudi Arabia. Cereal Chemistry, 66, 1e3. Bean, M. M., Huang, D. S., & Miller, R. E. (1990). Some wheat and flour properties of KlasicdA hard white wheat. Cereal Chemistry, 67, 307e309. Campbell, A. R. (1970). Inheritance of crude protein and seed traits in interspecific oat crosses. Dissertations Abstracts International B, 31, 3111e3112. Copp, L. G. L. (1965). Purple grains in hexaploid wheat. Wheat Information Service, (19e20), 18. Dedio, W., Hill, R. D., & Evans, L. E. (1972). Anthocyanins in pericarp and coleoptiles of purple wheat. Canadian Journal of Plant Science, 52, 977e980. Dick, J. W., & Quick, J. S. (1983). A modified screening test for rapid estimation of gluten strength in earlygeneration durum wheat breeding lines. Cereal Chemistry, 60, 315e318. Ge´linas, P., & McKinnon, C. M. (2006). Effect of wheat variety, farming site, and bread-baking on total phenolics. International Journal of Food Science and Technology, 41, 329e332. Hosseinian, F. S., Li, W., & Beta, T. (2008). Measurement of anthocyanins and other phytochemicals in purple wheat. Food Chemistry, 109, 916e924. Knievel, D. C., Abdel-Aal, E.-S. M., Rabalski, I., Nakamura, T., & Hucl, P. (2009). Grain color development and the inheritance of high anthocyanin blue aleurone and purple pericarp in spring wheat (Triticum aestivum L.). Journal of Cereal Science, 50, 113e120.
CHAPTER 6 Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
Knott, D. R. (1958). The inheritance in wheat of a blue endosperm colour derived from. Agropyron elongatum. Canadian Journal of Plant Science, 36, 571e574. Li, W., Corke, H., & Sun, S. C. (1998). Some characteristics of Chinese black-grained wheat flour. In H. Corke, & R. Lin (Eds.), Asian Food Product Development (pp. 76e82). Beijing: Science Press. Li, W., Sun, C., & Ren, G. (2004). Characteristic of black-grained wheat and its potential for utilization. China Condiment (Chinese), 26(1), 9e11. Li, W., Shan, F., Sun, S., Corke, H., & Beta, T. (2005). Free radical scavenging properties and phenolic content of Chinese black-grained wheat. Journal of Agricultural and Food Chemistry, 53, 8533e8536. Li, W., Beta, T., Sun, S., & Corke, H. (2006). Protein characteristics of Chinese black-grained wheat. Food Chemistry, 98, 463e472. Li, W., Pickard, M. D., & Beta, T. (2007a). Effect of thermal processing on antioxidant properties of purple wheat bran. Food Chemistry, 104, 1080e1086. Li, W., Pickard, M. D., & Beta, T. (2007b). Evaluation of antioxidant activity and electronic taste and aroma properties of antho-beers from purple wheat grain. Journal of Agricultural and Food Chemistry, 55, 8958e8966. Lila, A. M. (2004). Anthocyanins and human health: An in vitro investigative approach. Journal of Biomedicine and Biotechnology, 2004 306e313. Moore, J., Hao, Z., Zhou, K., Luther, M., Costa, J., & Yu, L. (2005). Carotenoid, tocopherol, phenolic acid, and antioxidant properties of Maryland-grown soft wheat. Journal of Agricultural and Food Chemistry, 53, 6649e6657. Payne, P. I., Seekings, J. A., Worland, A. J., Jarvis, M. G., & Holt, L. M. (1987). Allelic variation of glutenin subunits and gliadins and its effect on breadmaking quality in wheat: Analysis of F5 progeny from Chinese spring Chinese spring (Hope lA). Journal of Cereal Science, 6, 103e118. Pei, C., Sun, Y., Sun, C., Yan, G., & Ren, Y. (2002). Research and utilization of black-grained wheat. Seed (Chinese) (4), 42e44. Perten, H. (1990). Rapid measurement of wet gluten quality by the gluten index. Cereal Foods World, 35, 401e402. Piech, J., & Evans, L. E. (1979). Monosomic analysis of purple grain color in hexaploid wheat. Z. Pflanzenzu¨chtung, 82, 212e217. Sharman, B. C. (1958). “Purple pericarp”: A monofactorial dominant in tetraploid wheats. Nature, 181, 929. Siebenhandl, S., Grausgruber, H., Pellegrini, N., Rio, D. D., Fogliano, V., Pernice, R., et al. (2007). Phytochemical profile of main antioxidants in different fractions of purple and blue wheat, and black barley. Journal of Agricultural and Food Chemistry, 55, 8541e8547. Sun, C., Sun, Y., Yuan, W., Yan, W., Pei, Z., Zhang, M., et al. (1999). Breeding and qualitative analysis for black grain wheat 76 of superior quality. Acta Agronomica Sinica (Chinese), 25, 50e54. Wall, I. S. (1979). The role of wheat proteins in determining baking quality. In D. L. Laidman & R. O. Wyn Jones (Eds.), Recent Advances in the Biochemistry of Cereals (pp. 275e311). London: Academic Press. Yu, L., Zhou, K., & Parry, J. W. (2005). Inhibitory effects of wheat bran extracts on human LDL oxidation and free radicals. LWT e Food Science Technology, 38, 463e470. Zeven, A. C. (1991). Wheats with purple and blue grains: A review. Euphytica, 56, 243e258.
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6
Flour and Bread from Black-, Purple-, and Blue-Colored Wheats Wende Li, Trust Beta Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada
CHAPTER OUTLINE List of Abbreviations 59 Introduction 59 Quality and Traits 60 Antioxidant Properties 62 Technological Issues 65
Problems of quality and technical processes 65 Adverse reactions 66
Summary Points 66 References 66
LIST OF ABBREVIATIONS BGW 76 Black-grained wheat 76 DPPHl 2,2-Diphenyl-1-picryhydrazyl free radical HMW-glu High-molecular-weight glutenin IVPD In vitro protein digestibility MPT Midline peak time ORAC Oxygen radical absorbance capacity PWB Purple wheat bread SDS Sodium dodecyl sulfate WWB Whole wheat bread WFB White flour bread
INTRODUCTION Wheat is one of the most important grains in our daily diets. In recent years, bioactive compounds in wheat have attracted increasingly more interest from both researchers and food manufacturers because of their benefits in promoting health and preventing disease. For example, wheat bran extracts significantly inhibited lipid peroxidation in human low-density lipoprotein in vitro (Yu et al., 2005). Wheat with high levels of antioxidant activity has the potential for value-added use, particularly in the formulation of functional foods. Flour and Breads and their Fortification in Health and Disease Prevention. DOI: 10.1016/B978-0-12-380886-8.10006-6 Copyright Ó 2011 Elsevier Inc. All rights reserved.
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SECTION 1 Flour and Breads
Unlike red and white wheats, blue-, purple-, and black-colored wheats contain natural anthocyanin compounds. The role of anthocyanin pigments as medical agents has been wellaccepted dogma in folk medicine throughout the world, and in fact these pigments are linked to an amazingly broad-based range of health benefits (Lila, 2004). Based on the potential of these colorful-grained wheats, several functional foods have been developed from these wheats in recent years, including purple wheat bran muffin (Li et al., 2007a) and antho-beer made from purple-grained wheat (Li et al., 2007b), soy sauce (Li et al., 2004), vinegar, breakfast cereal and instant noodles produced from black-grained wheat, and fine dried noodles made from blue-grained wheat (Pei et al., 2002).
60
Neither blue- nor purple-colored wheat pigmentation originated in common wheat (Knievel et al., 2009). Knott (1958) found the blue seed color of blue-colored wheat to be inherited from Agropyron chromosome additions or substitutions into common wheat rather than a natural occurrence among common wheat species. Zeven (1991) reported that the blue aleurone trait was introgressed into common wheat from blue pigmented Triticum boeoticum, Agropyron tricholphorum, Agropyron glaucum, and, most frequently, from Agropyron elongatum. For example, blue-colored wheat cultivar Leymus dasystachys, which is related to the Agropyron genus, was crossed with common wheat to produce blue-colored wheat (Zeven, 1991). Purplecolored wheat was discovered in tetraploid durum, Triticum dicoccum, in east African areas such as Ethiopia, and it was introgressed into common wheat (Zeven, 1991). Copp (1965) reported that a stable hexaploid wheat with purple grain color was obtained from the cross Triticum dicoccum var. Arraseita Perc. Triticum aestivum L., and its purple grain color was as intense as that in the original tetraploid purple-colored wheat. Above “Triticum dicoccum var. Arraseita Perc.” was purple tetraploid wheat from Abyssinia, with the purple pericarp color being inherited as a monofactorial dominant character in tetraploid wheats (Sharman, 1958). Above “Triticum aestivum L.” was commercial hexaploid wheat (Copp, 1965). The breeding process of black-grained wheat cultivar was as follows (Sun et al., 1999). A blue-grained hexaploid wheat (allo substitution line “blue 1”) was first bred by scientists from Shanxi Academy of Agricultural Science in the 1970s, and then through the breeding effort of 20 years, the scientists bred a purple-grained hexaploid wheat (“purple 12-1”), a blueepurple-grained hexaploid wheat (“blueepurple 114”), and a black-grained hexaploid wheat (“black 76”). The blue 1 was bred by crossing common hexaploid wheat (Triticum aesticum) with Agropyron glaucum. Purple 12-1 was bred by crossing common hexaploid wheat (T. aesticum) with Elymus dasystachys. However, blueepurple 114 was bred by crossing blue 1 with purple-grained tetraploid wheat. Finally, black 76 was bred by crossing blueepurple 114 used as the female parent with purple 12-1 as the male parent. Another purple-grained wheat (T. aestivum) cultivar was UM 606a (Hard Federation//Chinese Sping/Nero/3/3) Pitic 62) (Dedio et al., 1972), derived from the crosses of “Chinese Spring” with the purple T. durum cultivar “Nero” (Piech and Evans, 1979). In bread wheats (T. aesticum), white and red wheats are common, but purple- and blue-colored wheats are rare (Zeven, 1991). Researchers reported on purple-colored bread wheat accessions that had cultivars K-49990, K-55583, and K-59158, derived from the crosses of common bread wheats by “T. aethiopicum” (purple-colored tetraploid wheat from Ethiopia) (Zeven, 1991). Although pigments exist in wheat grains at very low concentrations, they substantially influence the quality of wheat products such as bread, pasta, and noodles (Abdel-Aal and Hucl, 2003). Because of the colorful appearance of black, blue, and purple wheat grains, they are currently produced only in small amounts for making specialty foods (Abdel-Aal et al., 2006). However, it is useful to understand the antioxidant properties, qualities, and traits of these colored wheat grains in order to increase their production and use.
QUALITY AND TRAITS Sun et al. (1999) reported on the nutritive composition of black-grained wheat 76 (BGW 76) and the common wheat, Jinchun 9. For example, their nutrient composition was as follows:
CHAPTER 6 Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
crude protein, 20.50% in BGW 76 and 12.90% in Jinchun 9; lipid, 1.60% in BGW 76 and Jinchun 9; carbohydrate, 62.10% in BGW 76 and 71.90% in Jinchun 9; crude fiber, 2.40% in BGW 76 and 2.10% in Jinchun 9; ash, 1.90% in BGW 76 and Jinchun 9; vitamin K, 11.47 mg/kg in BGW 76 and 7.01 mg/kg in Jinchun 9; calcium, 0.56 g/kg in BGW 76 and 0.14 g/ kg in Jinchun 9; phosphorus, 4.10 g/kg in BGW 76 and 2.41 g/kg in Jinchun 9; and selenium, 1.04 mg/kg in BGW 76 and 0.26 mg/kg in Jinchun 9. Compared with Jinchun 9, levels of crude protein, crude fiber, vitamin K, calcium, phosphorus, and selenium in BGW 76 were increased by 58.91, 14.29, 63.62, 300, 70.12, and 300%, respectively (Sun et al., 1999). In comparison with common bread wheats, Klasic (hard white wheat), Yecora Rojo (red grain wheat), and Glenlea (Canadian hard red spring wheat), crude protein, ash, and lipid were 17.71, 2.29, and 2.59% in the wholemeal of black-grained wheat; 14.07, 1.62, and 2.52% in the wholemeal of bread wheat Klasic; 13.67, 1.64, and 2.03% in the wholemeal of bread wheat Yecora Rojo; and 14.52, 1.88, and 2.89% in the wholemeal of bread wheat Glenlea, respectively (Li et al., 2004). The flour produced from black-grained wheat also showed the highest crude protein content in comparison with flours prepared from bread wheats Klasic, Yecora Rojo, or Glenlea. The nutritive composition of flour from black-grained wheat and bread wheats Klasic, Yecora Rojo, and Glenlea, respectively, was as follows: crude protein, 18.26, 13.76, 12.59, and 14.23%; ash, 0.95, 0.74, 0.70, and 0.96%; lipid, 1.56, 1.84, 1.31, and 2.18%; and carbohydrate, 75.03, 77.73, 79.32, and 76.03% (Li et al., 2004). Bean et al. (1990) reported that protein content ranged from 8.1 to 14.0% in the wholemeal of bread wheat Klasic and averaged 9.5% in its flour. The protein and ash contents were 14.2e15.7 and 1.55e1.64%, respectively, in the wholemeal of bread wheat Yecora Rojo, and they were 12.9e15.1 and 0.64e0.68% in its flour, respectively (Al-Mashhadi et al., 1989). Campbell (1970) reported that high protein content in grain seed was associated with dark seed color and shattering. Color determination indicated that black-grained wheat had low L) value compared with bread wheats Klasic, Yecora Rojo, or Glenlea (Li et al., 2004). The L) value is an indicator of the degree of whiteness; for example, the L) value was 98.04 for the white body reference and 34.51 for the black body reference. The L) values of seed, bran, wholemeal, and flour were 38.04, 62.66, 81.74, and 97.34 for black-grained wheat; 64.46, 71.95, 94.69, and 100.77 for bread wheat Klasic; 57.94, 71.95, 90.99, and 100.77 for bread wheat Yecora Rojo; and 55.77, 71.99, 89.39, and 97.90 for bread wheat Glenlea, respectively (Li et al., 2004). Because the L) value (38.04) of black-grained wheat was very similar to the L) value (34.51) of the black body reference, the seed color of black-grained wheat was also visually black. The high crude protein content of black-grained wheat appears to be correlated to its black (deep purple) seed color. The bread making quality of wheat is largely determined by the quantity and quality of the storage proteins of the grain endosperm or prolamins (Wall, 1979). Prolamins consist of glutenins and gliadins. Payne et al. (1987) reported on the effects of glutenin subunits and gliadins on bread making quality. It is important to fully understand protein properties of blue-, purple-, and black-colored wheats in order to predict their potential uses. Li et al. (2006) reported protein characteristics of black-grained wheat, three common bread wheatsdKlasic, Yecora Rojo, and Glenleadand the common steamed-bread wheat Taifeng. For example, sodium dodecyl sulfate (SDS) sedimentation values of their whole meals decreased in the order bread wheat Glenlea (16.9 ml/g) > bread wheat Klasic (16.5 ml/g) > bread wheat Yecora Rojo (15.0 ml/g) > black-grained wheat (13.3 ml/g) > steamed-bread wheat Taifeng (9.9 ml/g) (Li et al., 2006). The high SDS sedimentation value was associated with strong gluten strength because the SDS sedimentation value had a positive correlation with gluten strength (Dick and Quick, 1983). Gluten index decreased in the order Glenlea (99.37%) > Yecora Rojo (98.88%) > Klasic (98.66%) > black-grained wheat (69.74%) > Taifeng (50.09%) (Li et al., 2006). Therefore, low gluten index value indicated poor strength of wet gluten dough because there was a positive correlation coefficient (R ¼ 0.9606) between gluten
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SECTION 1 Flour and Breads
index and SDS sedimentation value (Li et al., 1998). For bread making, the optimum gluten index range is between 60 and 90 (Perten, 1990), and the gluten index value (69.74%) of black-grained wheat fell in the optimum gluten index range. Mixograph curves and parameters derived from the curves are also useful tools for indicating good or poor gluten strength of different wheat cultivars. For example, the mixograph parameter midline peak time (MPT) shows the best correlation with gluten strength. A low MPT value is an indication of weak gluten strength. The MPT values of wheat flours in water decreased in the order Glenlea (6.27 min) > Yecora Rojo (6.11 min) > Klasic (5.41 min) > black-grained wheat (2.93 min) > Taifeng (2.26 min) (Li et al., 2006). The order of their MPT values was similar to that of their gluten index. MPT values also indicated that gluten strength of black-grained wheat flour was stronger than that of Taifeng wheat flour, but obviously it was weaker than that of bread wheat flours Klasic, Yecora Rojo, and Glenlea.
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In the case of pepsin, in vitro protein digestibility (IVPD) of whole meal and gluten at 24 h was 82.42 and 96.45% for black-grained wheat, 82.94 and 95.07% for steamed-bread wheat Taifeng, 87.23 and 95.42% for bread wheat Klasic, 84.43 and 95.37% for bread wheat Recora Rojo, and 84.04 and 94.62% for bread wheat Glenlea, respectively (Li et al., 2006). The wholemeal of Klasic had significantly higher IVPD (p < 0.05) than that of black-grained wheat, Taifeng, Yecora Rojo, and Glenlea, but there were no significant differences (p < 0.05) in IVPD among their glutens. Total essential amino acid and total amino acid were 4.23 and 15.54% in the flour of black-grained wheat, 3.48 and 13.13% in Taifeng flour, 3.10 and 11.63% in Klasic flour, 2.74 and 10.17% in Yecora Rojo flour, and 3.26 and 12.10% in Glenlea flour, respectively (Li et al., 2006). The increase in total essential amino acid in the flour of black-grained wheat was up to 21.55, 36.45, 54.38, and 29.75% higher than that in the flours of Taifeng, Klasic, Yecora Rojo, and Glenlea, respectively. Similarly, the increase in total amino acid in the flour of black-grained wheat was up to 18.35, 33.62, 52.80, and 28.43% higher than that in the flours of Taifeng, Klasic, Yecora Rojo, and Glenlea, respectively. High total amino acid content in the flour of black-grained wheat was associated with its high crude protein content. Dough stickiness values of flours decreased in the order steamed-bread wheat Taifeng (392.75 g) > bread wheat Yecora Rojo (313.05 g) > black-grained wheat (223.76 g) > bread wheat Klasic (186.01 g) > bread wheat Glenlea (182.67 g) (Li et al., 2006). A high dough stickiness value indicates stickier dough. Bakery characteristics are poor if the dough is too sticky. The flour from black-grained wheat had better baking properties than that obtained from Taifeng and Yecora Rojo, but its dough stickiness was somewhat stickier than that of flours from Klasic and Glenlea. The baking quality of wheat cultivars can be predicted according to their high-molecular-weight glutenin (HMW-glu) subunits. For example, Taifeng has HMW-glu subunits similar to Anza (2 þ 12 and 7 þ 8 subunits), Klasic has HMW-glu subunits similar to Yecora Rojo (1, 17 þ 18, and 5 þ 10 subunits), and black-grained wheat has HMW-glu subunits similar to Glenlea (2), 7 þ 8, and 5 þ 10 subunits) (Li et al., 2006). Because good baking quality is strongly correlated with the presence of 1 and 5 þ 10 or 2) and 5 þ 10 HMW-glu subunits and poor baking quality is usually associated with 2 þ 12 HMW-glu subunits, the HMW-glu subunits (2) and 5 þ 10) in black-grained wheat predict that blackgrained wheat can be classified as bread wheat (Li et al., 2006).
ANTIOXIDANT PROPERTIES Purple wheat flour bread (PWB) and two bread controls, whole wheat meal bread (WWB) and white flour bread (WFB), were prepared according to the method described by Ge´linas and McKinnon (2006), and their antioxidant properties were evaluated. Their 2,2-diphenyl1-picryhydrazyl free radical (DPPHl) scavenging activity and kinetics are shown in Table 6.1 and Figure 6.1, respectively. Purple wheat bread PWB had the highest DPPHl scavenging activity (47.58%) at 60 min compared to wholemeal bread WWB (34.06%) and white
CHAPTER 6 Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
TABLE 6.1 Free Radical Scavenging Activity of Bread Extracts Reacting with DPPHl (at 60 min)a Bread
DPPHl Scavenging (%)
Whole wheat meal bread Wheat white flour bread Purple wheat flour bread
34.06 32.20 47.58
Source: Reprinted from our unpublished data. a Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. DPPHl scavenging activity was determined according Li et al. (2007a). Results are expressed as mean, n ¼ 2.
DPPH radical scavenging (%)
50
40
30
20 Whole wheat meal bread 10
Wheat white flour bread Purple wheat flour bread
0 0
10
20
30
40
50
60
Reaction time (min)
63 FIGURE 6.1 Radical scavenging activity kinetics of bread extracts reacting with DPPHl for 60 min. Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. DPPHl scavenging activity was determined according to Li et al. (2007a). Results are expressed as mean, n ¼ 2. Source: Reprinted from our unpublished data.
bread WFB (32.20%). The DPPHl scavenging activity from kinetics curve was also in the order PWB > WWB > WFB (see Figure 6.1). The DPPHl scavenging activity of whole meal in several wheat genotypes was 33.51% for black-grained wheat, 25.57% for purple-grained wheat, 23.66% for blue-grained wheat, and 25.40 % for white-grained wheat (Li et al., 2005). The oxygen radical absorbance capacity (ORAC) of three bread extracts decreased in the same order PWB (12.09 g/kg) > WWB (10.64 g/kg) > WFB (8.88 g/kg) as that of DPPHl scavenging activity (Table 6.2). A high ORAC value is an indication of high antioxidant capacity in sample extract. Total anthocyanin content in PWB was 78 mg/kg (Table 6.3). Anthocyanin was not detectable in WWB and WFB. Anthocyanins are members of the bioflavonoid phytochemicals, which have been recognized to have health-enhancing benefits due to their antioxidant activity and anti-inflammatory and anticancer effects (Abdel-Aal et al., 2006). The total anthocyanin content of bran, wholemeal, and flour ranged between 415.9e479.7, 139.3e163.9, and 18.5e23.1 mg/kg in blue-grained wheat; 156.7e383.2, 61.3e153.3, and 3.1e14.3 mg/kg in purple-grained wheat; and 9.9e10.3, 4.9e5.3, and 1.5e1.7 mg/kg in red-grained wheat, respectively (Abdel-Aal and Hucl, 2003). Siebenhandl et al. (2007) reported total anthocyanin contents of 225.8 and 17.0 mg/kg in the bran and flour of bluegrained wheat and 34.0 and 8.2 mg/kg in the wholemeal and flour of purple-grained wheat, respectively. Hosseinian et al. (2008) reported total anthocyanin contents of 500.6 mg/kg in normal purple-grained wheat and 526.0 mg/kg in heat-stressed purple-grained
SECTION 1 Flour and Breads
TABLE 6.2 ORAC Values of Bread Extracts Reacting with 2,20 -Azobis (2-Methylpropionamide) Dihydrochloridea Bread Whole wheat meal bread Wheat white flour bread Purple wheat flour bread
Equivalent of Trolox (g/kg) 10.64 8.88 12.09
Source: Reprinted from our unpublished data. a Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. ORAC was determined according to Li et al. (2007a). Results are expressed as mean, n ¼ 2.
TABLE 6.3 Total Anthocyanin Content of Bread Extracts Determined Using the pH Differential Methoda Bread Whole wheat meal bread Wheat white flour bread Purple wheat flour bread
Equivalent of Cyanidin 3-Glucoside (mg/kg) Not detectable Not detectable 78
Source: Reprinted from our unpublished data. a Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. Total anthocyanin content was determined according to Li et al. (2007a). Results are expressed as mean, n ¼ 2.
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wheat, and they confirmed that cyanidin 3-glucoside was the predominant anthocyanin (103.0 mg/kg) in normal purple-grained wheat. The major anthocyanins were delphinidin 3-glucoside (56.5 mg/kg), delphinidin 3-rutinoside (49.6 mg/kg), cyanidin 3-glucoside (20.3 mg/kg), and cyaniding 3-rutinoside (16.8 mg/kg) in blue-grained wheat (Abdel-Aal et al., 2006) and cyanidin 3-glucoside (19.73e46.44 mg/kg) in purple-grained wheat (Abdel-Aal and Hucl, 2003). Anthocyanins make an important contribution to the antioxidant capacity of black-, purple-, and blue-colored wheats in comparison with that of red and white wheats, which contain only very low levels of anthocyanin (Abdel-Aal and Hucl, 2003). Total phenolic contents of PWB, WWB, and WFB are shown in Table 6.4. PWB showed the highest total phenolic content, and total phenolic contents decreased in the same order of PWB (1111 mg/kg) > WWB (1005 mg/kg) > WFB (515 mg/kg) as that of DPPHl scavenging activity and ORAC. Ge´linas and McKinnon (2006) reported that total phenolic contents (gallic acid equivalent), which ranged from 522 to 866 mg/kg for the wholemeal of organic white wheat varieties, were up to more than 1000 mg/kg for their wholemeal bread and approximately 400 mg/kg for their white bread. Baking slightly increased the level of total phenolic content in bread crust (Ge´linas and McKinnon, 2006), likely due to the Maillard reaction. Total phenolic contents (ferulic acid equivalent) were 1973.5 and 811.6 mg/kg in the wholemeal and flour of purple-grained wheat and 7616.4 and 646.5 mg/kg in the bran and flour of blue-grained wheat, respectively (Siebenhandl et al., 2007). The total phenolic contents (ferulic acid equivalent) of bran and wholemeal were, respectively, 2415 and 1108 mg/kg in black-grained wheat, 2290 and 929 mg/kg in purple-grained wheat, 1416 and 706 mg/kg in blue-grained wheat, and 2215 and 817 mg/kg in white-grained wheat (Li et al., 2005). A high correlation (R ¼ 0.96) was found between total phenolic content and DPPHl scavenging activity for wheat wholemeals (Li et al., 2005). High total phenolic levels are also an indication of high antioxidant capacity. Because there are differences in phenolic content among wheat genotypes, the level of phenolics in bread will be affected by the raw wheat material ingredients used.
CHAPTER 6 Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
TABLE 6.4 Total Phenolic Content of Bread Extracts Determined Using the FolineCiocalteau Methoda Bread
Equivalent of Ferulic Acid (mg/kg)
Whole wheat meal bread Wheat white flour bread Purple wheat flour bread
1005 515 1111
Source: Reprinted from our unpublished data. a Bread (3 g) was extracted in 10 ml 95% ethanol:1 N HCl (85/15, v/v) at 25oC for 20 h. Total phenolic content was determined according to Li et al. (2007a). Results are expressed as mean, n ¼ 2.
TABLE 6.5 Phenolic Acid Composition of Breads Determined Using the HPLC Methoda Phenolic acid
WWB (mg/kg)
WFB (mg/kg)
PWB (mg/kg)
Gallic acid Protocatechuic acid p-Hydroxybenzoic acid Vanillic acid Syringic acid m-Coumaric acid Caffeic acid p-Coumaric acid Ferulic acid Sinapinic acid Total phenolic acids
12 Not detectable 5 12 4 2 8 12 250 8 313
12 Not detectable 4 8 8 Not detectable 3 9 65 2 111
13 20 7 18 7 2 15 84 228 9 403
Source: Reprinted from our unpublished data. a Bread (2 g) was hydrolyzed in 60 ml of 4 M NaOH solution at 25oC for 4 h. Phenolic acid composition was determined according to Li et al. (2005f). Results are expressed as mean, n ¼ 2. PWB, purple wheat bread; WFB, white flour bread; WWB, whole wheat bread.
The phenolic acid composition of PWB, WWB, and WFB after hydrolysis is shown in Table 6.5. Ten types of phenolic acid were detected in PWB, 9 types of phenolic acid in WWB, and 8 types of phenolic acid in WFB. Major phenolic acids (>50 mg/kg) were ferulic acid (228 mg/kg) and p-coumaric acid (84 mg/kg) in PWB, ferulic acid (250 mg/kg) in WWB, and ferulic acid (65 mg/kg) in WFB. Total phenolic acids decreased in the same order of PWB (403 mg/kg) > WWB (313 mg/kg) > WFB (111 mg/kg) as that of total phenolic content. PWB had 3.63 and 1.29 times higher total phenolic acids than WFB and WWB, respectively. Siebenhandl et al. (2007) reported that ferulic acid was 851.7 and 180.1 mg/kg in the wholemeal and flour of purplegrained wheat and 3503.3 and 151.1 mg/kg in the bran and flour of blue-grained wheat, vanillic acid 35.1 and 9.9 mg/kg in the wholemeal and flour of purple-grained wheat and 99.8 and 10.1 mg/kg in the bran and flour of blue-grained wheat, and p-coumaric acid 24.3 and 4.6 mg/kg in the wholemeal and flour of purple-grained wheat and 456.6 and 6.3 mg/kg in the bran and flour of blue-grained wheat, respectively. The level of phenolic acids in the wholemeal of soft wheat cultivars ranged from 455.92 to 621.47 mg/kg for ferulic acid, 8.44 to 12.68 mg/kg for vanillic acid, 8.86 to 17.77 mg/kg for syringic acid, and 10.40 to 14.10 mg/kg for p-coumaric acid (Moore et al., 2005). Potential health benefits have been demonstrated for phenolic compounds because of their ability to act as antioxidants (Siebenhandl et al., 2007).
TECHNOLOGICAL ISSUES Problems of quality and technical processes Protein, flour, and dough quality of purple- and blue-colored wheats need to be evaluated for their potential in making bread products. It is important to breed black-, purple-, and
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SECTION 1 Flour and Breads
blue-colored wheats as bread wheat in the future. It is valuable to investigate chemical transformations of phenolic acids and anthocyanins during baking.
Adverse reactions Although very little is known about adverse reactions to black-, purple-, and blue-colored wheats and their food products, known adverse reactions to wheat include allergies and celiac disease. Different clinical forms of wheat allergy include baker’s asthma, atopic eczema/ dermatitis syndrome, urticaria, and wheat-dependent, exercise-induced anaphylaxis.
SUMMARY POINTS l
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Black-grained wheat contains a high crude protein content compared to that of common bread wheats Klasic, Yecora Rojo, and Glenlea. Black-grained wheat can be used as bread wheat for making bread because its HMW-glu subunits (2), 7 þ 8, and 5 þ 10) are similar to those found in the bread wheat Glenlea. Protein quality of black-grained wheat needs to be improved through breeding technology to increase its gluten strength, which is weak compared with that of common bread wheats Klasic, Yecora Rojo, and Glenlea. In addition to containing phenolic acids, black-, purple-, and blue-colored wheats also contain natural anthocyanins, whereas red and white wheats do not. Anthocyanins are important antioxidants and therefore likely to be beneficial in improving health and preventing some diseases. Anthocyanins and phenolic compounds make a major contribution to the antioxidant capacity of black-, purple-, and blue-colored wheats. Purple wheat bread showed the highest antioxidant capacity, with the antioxidant capacity of three bread products decreasing in the order purple wheat bread > whole meal bread > white bread. There is potential to use black-, purple-, and blue-colored wheats as novel ingredient resources for the development of value-added products.
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CHAPTER 6 Flour and Bread from Black-, Purple-, and Blue-Colored Wheats
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