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Department of Plant Sciences, North Dakota State University, Fargo, ND 58105
* Corresponding author (John.Davies{at}ndsu.nodak.edu)
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Abbreviations: PPO, polyphenol oxidase
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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A potential target end-use market for specialty wheat is the Asian noodle market. Approximately half of all wheat flour used in Asian countries is used for noodle making (Miskelly and Gore, 1991). Cantonese style noodles are a type of yellow alkaline Asian noodle that have a firmer "mouth-feel" or "bite" than other noodle types, and they are made out of hard wheat flour, ranging from 10.5 to 13.5% protein (Hatcher, 2001). Historically, wheat producers in the U.S. northern Plains produce high protein content wheat, so acceptance of high protein flour for Cantonese noodles may promote development of noodle and dual-purpose wheat cultivars targeting both an export and domestic market, as described by Lang et al. (1998).
A major quality requirement for Cantonese noodles is the lack of noodle discoloration. Color of the noodle is the main initial determinant of consumer appeal (Miskelly, 1996). A bright and yellow noodle color 24 to 48 h after production is desired for Cantonese style noodles (Kruger et al., 1992; Morris et al., 2000). Discoloration is typified by a gray or brown color change from the characteristic cream or yellow color of the noodle product after storage. When noodles are exposed to air, enzymatic and nonenzymatic reactions result in pigmentation or discoloration (Moss, 1971). Cantonese noodles, which are sold fresh and may be stored for as long as 48 h or more before use, are particularly susceptible to discoloration (Miskelly, 1984; Morris et al., 2000). The discoloration of Cantonese noodles is influenced by processing methods, storage conditions, contaminants and some intrinsic wheat grain quality characteristics (Kruger and Reed, 1988; Miskelly, 1984; Moss, 1971).
Polyphenol oxidase (E.C 1.14.18.1 and E.C 1.10.3.2, syn; tyrosinase, catecholase, o-diphenol oxidase), an oxidative enzyme present mainly in the bran of wheat (Kruger, 1976), is a major factor in Cantonese noodle discoloration. High kernel PPO activity results in decreased noodle brightness (Baik et al., 1995; Kruger et al., 1992; Moss, 1971). Flour protein content also affects noodle discoloration, with high protein resulting in decreased noodle brightness (Baik et al., 1995; Lang et al. 1998; Miskelly and Moss, 1985; Moss, 1971). High flour ash is associated with decreased brightness of noodles (Kruger et al., 1994; Miskelly, 1984; Oh et al., 1985). Some studies have shown that white grain wheat is superior to red in noodle brightness (Miskelly, 1984; Oh et al., 1985; Park et al., 1997). Hard wheat also has significant starch damage after milling compared with soft wheat and this negatively affects noodle brightness and yellowness (Miskelly, 1984, Oh et al., 1985; Preston et al., 1995).
Expression of wheat quality characteristics is influenced by genotype, environment, and their interaction components. These components have been shown to affect PPO activity (Baik et al., 1994; Park et al., 1997; Park et al., 2000), kernel color (Orth and Shellenberger, 1988; Wu et al., 1999), ash content (Busch et al., 1969; Peterson et al., 1986; Shuey, 1975), and grain protein content (Busch et al., 1969; Peterson et al., 1992).
There have been few reports detailing the characteristics of spring wheat genotypes developed for the U.S. northern Plains and targeting an Asian noodle market. This is likely because hard red spring wheat is traditionally used for bread products, and environmental conditions are conducive to producing high protein wheat. However, to explore new markets and end-uses for spring wheat, breeders in the U.S. northern Plains need to identify suitable genotypes, and they need to know how the environment is influencing these genotypes for noodle quality traits.
The objectives of this study were to (i) examine wheat quality traits correlated to Cantonese noodle color from selected spring wheat genotypes, (ii) assess the influence of the genotype x environment interactions in the expression of these traits, (iii) determine the Cantonese noodle color quality from selected spring wheat genotypes, and (iv) predict the feasibility of developing hard spring wheat genotypes in the U.S. northern Plains for a Cantonese noodle market.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Experimental Design and Environments
The experimental design was a randomized complete block with six replicates. Main effects were genotypes (9), locations (4), and years (2). Locations represented the west central, east central, and eastern regions of North Dakota, and they were situated at Minot (48° 11' N lat., 101°18' W long., elev. 539 m), Carrington (47° 27' N lat., 99° 08' W long., elev. 483 m), Casselton (46° 53' N lat., 97° 18' long., elev. 288 m), and Prosper (47° 0' N lat., 97° 7' W long., elev. 284 m). Soils consisted of a Williams series (fine, loamy, mixed, superactive, frigid typic Argiustolls) at Minot, a Heimdal (coarse-loamy, mixed, superactive, frigid, Calcic Hapludolls)–Emerick series (coarse-loamy, mixed, superactive, frigid, Pachic Hapludolls) at Carrington, and a Beardon (fine-silty mixed superactive, frigid, Aeric Calciaquolls)–Perella series (fine-silty, mixed, superactive, frigid Typic Endoaquolls) at Casselton and Prosper.
Plot Seeding, Maintenance, and Harvest
Seed for sowing was treated with a flowable fungicide having the active ingredients carboxin (5,6-dihydro-2-methyl-N-phenyl-1,4-oxathiin-3-carboxamide), imazalil {1-[2-(2,4-dichlorophenyl)-2-(2-propenyloxy)-ethyl]-1H-imadzole}, and thiabendazole [2-(4-thizolyl)-benzimidazole] (‘RTU-Vitavax extra’, Gustafson LLC, Plano, TX) at the rate of 3.25 mL kg-1 to control common root rot. Seed was sown by machine in four rows spaced 30.5 cm apart in each plot. Each experimental unit consisted of a field plot having a final harvest measurement of 2.88 m2 in 2000 and 4.44 m2 in 2001. In 2000 and 2001, plots were planted and harvested at four locations in North Dakota. Planting dates for 2000 were 23 April at Casselton, 25 April at Prosper, 28 April at Minot, and 1 May at Carrington. Planting dates for 2001 were 1 May at Minot, 2 May at Carrington, 15 May at Prosper, and 17 May at Casselton. Crop management practices were standard for spring wheat production in the U.S. northern Plains. Foliar fungicide treatments having propiconazole 1-((2-(2-,4-dichlorophenyl)-4-propyl-1,3-dioxoan-2-yl)methyl)-1 H-1,2,4-triazole (‘Tilt’, Syngenta Crop Protection, Inc., Greensboro, NC) as an active ingredient were applied at the rate of 292 mL ha-1 and a treatment having the active ingredient tebuconazole (alpha-[2-(4-chlorophenyl)-ethyl]-alpha-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol) (‘Folicur’, Bayer Corp., Pittsburgh, PA) was applied at the rate of 292 mL ha-1 to control foliar and head fungal diseases. Plots were harvested using a small-plot combine in 2000 on 7 August at Minot, 8 August at Carrington, 9 August at Casselton, and 10 August at Prosper, and in 2001 on 6 August at Minot, 10 August at Carrington, 13 August at Prosper, and 16 August at Casselton. Harvested material from each experimental unit was cleaned with a Carter-Day Dockage tester (Carter-Day Co., Minneapolis, MN).
Analysis of Wheat Grain and Flour Quality Characteristics
The PPO assay was similar to that described by Anderson and Morris (2001). Five kernels from each sample were placed into a 15-mL centrifuge tube. A 1.5-mL solution with 5 mM L-DOPA (L-3,4-dihydroxy phenyl-alanine) phenolic substrate and 50 mM MOPS (3-[N-morpholino] propanesulfonic acid) buffer (cat. # D9628, M1254, Sigma-Aldrich Corp., St. Louis, MO) adjusted to pH 6.5 was added to the centrifuge tube and placed on a shaker (IKA-Werke GMBH and Co. KG, Staufen, Germany) for 1 h, after which 1 mL was transferred to an 1-mL volume cuvette. Optical densities were determined with a DU640 Spectrophotometer (Beckman Instruments Inc., Fullerton, CA) at A475 nm. A standard curve was established by using mushroom PPO (6050 units mg-1 solid, cat. # T7755, Sigma Corp. St Louis, MO) and converting measured optical densities to PPO activity units. Polyphenol oxidase activity units were defined as causing a change in A265 nm of 0.001 AU min-1 at pH 6.5 and 25°C in a 3-mL reaction mix containing L-dopa and L-ascorbic acid. Polyphenol oxidase assays were conducted in triplicate, and the average reading was recorded for each sample.
Grain moisture was determined with a Motomco Moisture Meter 919ES automatic moisture tester (Dickey-John Corp., Auburn, IL) (AACC, 2000, Method 44-11). From each plot sample, 100 g of wheat grain was tempered overnight to 140 g kg-1 moisture for soft, and 160 g kg-1 moisture for hard wheat (AACC, 2000, Methods 26-10A and 26-95). Tempered grain samples were milled with a Quadrumat Junior mill (C.W. Brabender Instrument Inc., South Hackensack, NJ) (AACC, 2000, Method 26-50) then passed through a USA standard testing sieve No. 60 (250-µm aperture). Average flour yield obtained from milling was straight grade (720 g kg-1), based on the original grain sample weight and the total (break and reduction) flour product after sieving. Flour moisture and protein content were determined with an Infra-alyzer 400 near infra-red (NIR) machine (Technicon Instruments Corp., Elmurt, IL) (AACC, 2000, Method 39-11). Flour protein percentage results were expressed on a 140 g kg-1 moisture basis. Kernel color was measured by placing approximately 20 g of wheat kernels from each plot sample in the granular-material attachment (CR-A50) of a colorimeter (CR-310 Chroma Meter, Minolta Camera Co. Ltd, Ramsey, NJ). The colorimeter provides L*, a*, and b* chromatic scores, which are based on a tri-axial color space system where; L* = White–black (100 = pure white and 0 = black), a* = red–green, and b* = yellow–blue (CIE, 1976). The first color in the a* and b* parameters are in the positive direction and the second the negative. In this study the L* and b* chromatic scores were used to measure the brightness and yellowness of the noodles, respectively. The a* chromatic score was not used since it has not been widely adopted in previous Cantonese noodle discoloration studies. The ash contents for 3 g of flour obtained from each plot subsample were determined with a type 600 furnace (Barnstead/Thermolyne Corp, Dubuque, IA), and the results were expressed on a 140 g kg-1 moisture basis (AACC, 2000, Method 08-01). From each plot sample, 16 g of wheat grain was ground with a cyclone sample mill (UDY Corp., Ft. Collins, CO) to obtain whole-meal flour. Whole-wheat flour moisture was determined as described previously. Falling number tests were conducted on 8-g samples of whole-wheat flour to determine any sprouting damage with a Falling Number 1800 machine (Perten Instruments AB, Huddinge, Sweden) (AACC, 2000, Method 56-81B). All samples in this study were found to have falling numbers in excess of 300 s, indicating sound wheat (Data not shown).
Noodles
Yellow alkaline Cantonese style raw noodles were made in a process similar to that described by Morris et al. (2000). A Kan sui solution (0.9% sodium carbonate [Sigma Corp., St Louis, MO], 0.1% potassium carbonate [Sigma Corp., St. Louis, MO], and distilled water) was added to 25 g of flour adjusted to 380 g kg-1 moisture. The ingredients were mixed in a 100-g capacity bowl pin type mixer (National Manufacturing Co., Lincoln, NE) for 5 min to form the noodle dough. The dough was kneaded, rested, folded, and rolled with an Atlas model 150 domestic pasta machine (Marcato Co., Campodarsego, Italy) with decreasing gap size to a final thickness of 1.75 mm, measured with a micrometer thickness gauge (Mitutoyo dial indicator #2416F, Mitutoyo America Corp., Aurora, IL). The finished sheets were stored in sealed plastic bags at room temperature. Time-dependant discoloration measurements based on the L* and b* chromatic score were made on single sheets using a Minolta Colorimeter at 0 and 24 h on a white (L* 92.77, a* 0.67, b* 0.77) color paper background.
Statistical Analysis
Combined analysis of variance (ANOVA) to determine significant differences among components of analysis was calculated after testing error mean squares for homogeneity between environments by Bartlett's test. Genotype was considered a fixed factor; year and location or environment considered random. Where environments were not homogenous for error mean square, environment was used to replace year and location as a source of variation. Fisher's F-protected least significant difference (LSD) method was used to separate means. Appropriate error terms and degrees of freedom for F-tests of the ANOVA and LSDs were considered after calculation of expected mean squares (Cochran, 1951; Satterthwaite, 1946; Steel et al., 1997).
Correlation coefficients (r) were used as a measure of the phenotypic association between wheat kernel and flour quality parameters and noodle color. To obtain an estimate of r, Pearson's product-moment correlation coefficients were calculated for each environment after combining replicates within an environment. Environments were pooled after testing for homogeneity as in Steel et al. (1997). The Windows 2.0 version of Statistix (Analytical Software, Tallahassee, FL) was used in the calculation of ANOVA, LSD, and Pearson's product moment correlation coefficient values.
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RESULTS AND DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Genotype x Environment Interactions of Wheat Quality Traits Correlated to Cantonese Noodle Color
A combined ANOVA for PPO activity, flour protein, kernel brightness, and flour ash (Tables 2 and 3) indicates that these characteristics are affected by genotype and environment. Genotype x location x year or a genotype x environment interaction was significant for all traits. This suggests that expression of these traits for any specific genotype is affected by the location and year (environment) combinations as indicated by the large mean squares for the year x location source of variation. The lack of significant genotype x location interaction for PPO activity, flour protein, and kernel L* indicates that it may not be appropriate to test at single locations for these traits in the targeted region (Fehr, 1991). Selection among genotypes grown over a number of different locations and years for these traits would likely optimize the development of genotypes with desirable Cantonese noodle quality characteristics.
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Cantonese Noodle Color Quality from Selected Spring Wheat Genotypes
Noodle discoloration was evident in measurements of brightness and yellowness (Table 5). The genotype with lowest PPO activity did not necessarily produce the brightest noodle. IDO 488 had a moderate level of PPO activity, and IDO 470 had a low activity over environments (Table 4), yet IDO 488 produced a brighter noodle (Table 5). This illustrates that PPO activity, although an important factor in Cantonese noodle discoloration, is not the only factor impacting noodle quality. This result is consistent with Hatcher et al. (1999), who implied that noodle discoloration was not solely dependent on enzyme activity. White wheat genotypes produced the two highest noodle brightness means after 24 h. However, a non-significant correlation between noodle L* 24 h and kernel L* showed that a bright kernel color was not necessarily always associated with a bright noodle (Table 1). An example of this situation is MTHW 9420, which produced noodles that were duller than red-seeded genotypes after 24 h (Table 5). The two genotypes with the highest mean noodle brightness, IDO 470 and IDO 488, had readings approximating an L* reading of 72.00 after 24 h, which is considered the lower limit of brightness discoloration acceptable in the Cantonese noodle market. The noodle sheet brightness of IDO 488 demonstrates the advantage of a soft endosperm over a hard endosperm in color reflectance. The noodle made from soft endosperm reflects more light, whereas noodles made from hard endosperm are more translucent because of the properties of the protein-starch matrix (Oh et al., 1985).
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Our Cantonese noodle brightness readings at 24 h were low in comparison to other studies (Kruger et al., 1992; Lang et al., 1998; Habernicht et al., 2002). This might be due to the relatively high ash and protein content of the genotypes, differences in the flour extraction rates used, differences in the amount of water added to the dough mix, and differences in the alkali formulation used (Baik et al., 1995; Kruger et al., 1992; Miskelly and Moss, 1985). Premium noodle flour can also have an extraction rate as low as 45% and low ash contents of 3.2 to 4.0 g kg-1 (Miskelly, 1996; Hatcher, 2001). Therefore, some of the noodle sheets from genotypes that discolored in this study at straight grade extraction rates may discolor much less under lower extraction and compare more favorably in color.
Of the selected genotypes used in this study, IDO 470 had the best quality characters for producing Cantonese Asian noodles with desired color. The flour from IDO 470 produced an acceptable bright, yellow noodle after 24 h (Table 5). Genotype IDO 470 in addition to having a hard endosperm, desirable for the texture in a Cantonese noodle product, also had moderate flour protein concentrations ranging from 120 to 135 g kg-1, and it had high kernel brightness along with low grain PPO activity (Table 4).
Feasibility of Developing Hard Spring Wheat Genotypes in the U.S. Northern Plains for a Cantonese Noodle Market
For breeders in the U.S. northern Plains, the question is whether new genotypes need to exclusively target either an Asian noodle or a pan bread market or whether dual-purpose genotypes can be developed for both markets. Low grain PPO activity, flour ash, and moderate protein content are desirable for genotypes targeting a Cantonese noodle market, and white wheat with these quality characteristics produce a more desirable noodle color compared with red wheats. Notwithstanding the inherent problems associated with using a hard wheat to produce a bright noodle product and the existence of a environment, which favors the production of spring wheat with high grain protein, ash content, and kernel vitreousness, we suggest a breeder for the U.S. northern Plains can develop acceptable noodle quality wheat genotypes. Differences exist in genotypes for wheat quality traits related to a desirable noodle color (Habernicht et al., 2002), and these traits can be selected for while considering performance over multiple environments. This has been shown for, IDO 470, which produced an acceptable bright and yellow Cantonese noodle. In our study this genotype had flour protein levels at most environments in the range of 132 to 139 g kg-1, which translates to the range of 140 to 150 g kg-1 in grain protein (data not shown), well within the protein levels of spring wheat grown in the U.S. northern Plains. IDO 470 also had low PPO activity, a desirable wheat quality characteristic for noodle color. This genotype would be representative of the type of spring wheat to be developed for the quality requirements of the Cantonese noodle market.
There may also be the possibility of a developing dual-purpose genotype for bread and noodle end-uses (Habernicht et al., 2002). A dual-purpose genotype would likely have low PPO activity, low flour ash, and flour protein at approximately 135 g kg-1, which is adequate for general bread making purposes. Therefore, despite the inherent difficulties in developing a dual-purpose hard spring wheat genotype (Lang et al., 1998), a breeder could achieve success by targeting a Cantonese Asian noodle market while selecting for these wheat quality characteristics.
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ACKNOWLEDGMENTS |
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This research was based in part on work supported by the cooperative State, Education and Extension Service, USDA, under Agreement No. 99-34216-7498.
Received for publication September 1, 2002.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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