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a Univ. of Idaho Aberdeen Research and Extension Center, P.O. Box 870, Aberdeen, ID 83210
b Dep. of Plant Sci. and Plant Pathology, Montana State Univ., Bozeman, MT 59717-3140
c Pendleton Flour Mills, 463 W. Hwy 26, Blackfoot, ID 83221
d Northern Agric. Res. Center, Star Route No. 36, Box 43, Havre, MT 59501
* Corresponding author (jmmartin{at}montana.edu).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Recent cropping diversification has prompted development and deployment of hard white spring wheat in the Pacific Northwest of the USA. Asian customers desire hard white wheat for manufacturing noodles largely because of its brighter flour and product color (Hatcher and Kruger, 1993). Asian consumers use 30 to 45% of their wheat in noodles (Miskelly, 1996). Additionally, domestic bread bakers use hard white spring as an alternative to hard red spring. Advantages to hard white spring wheat derive from the absence of red seed coat pigments that are found in hard red spring wheat. Red pigmentation discolors flour at high extraction levels and subsequently taints noodle color. Additionally, the lack of the red pigment results in lighter-colored whole wheat bread products. The USA does not currently produce hard white spring wheat in quantities sufficient for the export market, and produces limited quantities for the domestic bread market.
The utility of hard white spring wheat in two markets (bread and noodles) provides marketing advantages and unique challenges. In particular, lower protein wheat is needed for noodle manufacture than is typically desired for making bread. Protein levels in wheat are influenced by cultivar (genotype), N management, and by environmental conditions. Growers may manipulate the first two factors through cultivar selection and N application. However, environmental conditions may work either in support or opposition to cultivar selection and management. For instance, despite N management for high yield and low protein, a low-rainfall season will tend to produce a crop with low yield and high protein.
The lack of environmental predictability, and to a certain extent market conditions, has made the idea of dual-purpose hard wheat attractive. That is, if the grain does not meet quality specifications for one use, there is potential for placement of the grain in the alternative market. Grain protein concentration is heavily influenced by genotype. Yet, a range in grain protein concentration may be obtained when the same cultivar is grown across a range of environments, thus producing grain with variable end-use qualities. A challenge is that genetic factors for noodle vs. bread quality may work in opposition. For instance, Lang et al. (1998) found that superior noodle color characteristics were negatively correlated with bread loaf volume in a set of hard white spring wheat genotypes tested across three environments. However, much of this negative relationship could be attributed to grain protein, in that high protein was associated with high loaf volume and poor noodle color (Lang et al., 1998). Similar results were found by Habernicht et al. (2002), with a set of hard winter wheat genotypes grown in several dryland environments.
For this report, we assessed the relative influence of genotype, N management, and location on quality characteristics of a set of spring wheat cultivars that provided a range in gluten strength and acceptability for bread and Asian noodle quality. Additionally, given the possibility of grain entering market channels for either bread or noodle production, we were interested to identify grain characteristics that may provide direction to growers and buyers as to market suitability.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Milling and Baking Analysis
Total grain protein of samples was determined with a near-infrared analyzer (AACC Method 39-10A), calibrated by automated combustion analysis of total N content (Model NFP-428, LECO Corp., St. Joseph, MO), and corrected to 12% moisture. Samples were tempered (AACC Method 26-10) and milled with a Brabender Quadramat Senior Mill (AACC Method 26-21A). Flour protein concentration was determined by the same protocol as whole grain protein. With the Minolta CR-310 Chroma Meter (Ramsey, NJ), flour color was measured against the Commission Internationale de D'Elairage L*a*b* color scale. Brightness was measured by the L* axis, red-green colors by the a* axis, and yellow-blue colors by the b* axis.
Bread quality evaluations involved standard AACC mixograph and 100-g flour pup loaf tests (American Association of Cereal Chemists, 1995; Baley et al., 2001). Mixograph mixing time and absorption were scored for each sample. Tolerance to mixing was scored (1–8) by visual comparison of mixographs to standard mixograph reference charts, adjusted for protein content (Pomeranz, 1987). Dough was prepared for baking, noting water absorption and mixing time, by a protocol consistent with a 90-min, sugar-based fermented dough system. The bread formula contained 100 g flour, 6 g sugar, 3.5 g shortening, 1.8 g yeast, 1.5 g salt, 180 µg g–1 Doh-Tone (American Ingredients Co., Kansas City, MO), and 150 µg g–1 ascorbic acid oxidant. The finished loaves were analyzed for bake volume by measuring the displacement of canola seeds and crumb grain scored on a subjective 0 to 5 scale (5 = best).
Noodle Analysis
Chinese raw noodles were prepared by a method similar to Kruger et al. (1992) with the modifications described in Habernicht et al. (2002). Flour (100 g) was premixed at low speed on a National pup-loaf mixer for 1 min with 29.2 mL of a NaCl solution (4.29% w/v) during a 30-s time period. Mixing continued at medium speed for 5 min. Dough rested in a plastic bag for 30 min before sheeting with an Ohtake noodle machine (Ohtake Manufacturing Co., Ltd., Tokyo, Japan). Dough was folded and sheeted six times with a gap of 5 mm at 30°C. The dough rested 30 min before reduction sheeting, five reductions to a thickness of 1.2 mm. Dough sheets were stored in plastic bags at room temperature during evaluations. Noodle color was evaluated at 0 and 24 h after sheeting with the Minolta CR-310 Chroma Meter. The Chinese raw noodles were boiled and their texture profile after cooking evaluated as previously described (Lang et al. 1998, Habernicht et al. 2002). Texture characteristics (springiness, cohesiveness, adhesiveness, hardness, chewiness) were measured on five strands of rinsed noodles at 0 and 5 min after cooking with a TA-XT2 Texture Analyzer (Texture Technologies Corp., Scarsdale, NY) with a 6-mm flat Lexan probe.
Alkaline noodles were prepared as described in Guttieri et al. (2001b) by mixing 50 g flour to a crumbly consistency with 9 mL of alkaline salt solution (0.25% w/v Na2CO3, 1% NaCl) on a 35 g National pin mixer (National Manufacturing, Lincoln, NE) for 45 s. Dough was scraped down from the pins and bowl sides and mixed for another 45 s. Dough was collected and sheeted through an Atlas/Marcato (Wilton Industries, Woodridge, IL) hand-crank pasta maker at the zero (widest) setting for the first pass. The dough piece was folded twice and repeatedly passed through the sheeter until a sheet thickness of approximately 1.5 mm was achieved. The dough sheet was cut into three strips, stacked on a white tile, and measured for color at 0 and 24 h after sheeting as described for the Chinese raw noodles. Noodles were stored at room temperature in sealed plastic bags between color measurements.
Rapid Viscoanalysis of Flour Pasting
The flour pasting viscosity of each flour sample was determined with the Rapid Visco Analyser (Newport Scientific, Warriewood, NSW, Australia) to analyze 3 g of flour mixed with 25 mL of water. Pasting curves were determined with heating and mixing profiles from Guttieri et al. (2001a): flour suspension cycle of 10 s with a rotor speed of 960 rpm, followed by a 2-min pregelatinization step of 60°C at 160 rpm rotor speed (rotor speed held constant for all subsequent steps), a gelatinization step ramping the temperature to 93.5°C during a 6-min period, held at 93.5°C for a 4-min period, then cooled to 50°C for a 4-min period, and finally held at 50°C for 4 min. Peak flour pasting viscosity during the heating step was recorded in centipoise (cP = kg m2 s2), as were final viscosities during the 50°C holding cycle.
Statistical Analysis
The irrigated and rain-fed trials were analyzed independently by mixed effects analysis of variance with PROC MIXED in SAS (Littell et al., 1996). The analysis was combined across years, treating trial location, cultivar, and N as fixed effects and year, replication, and their interactions with location, cultivar, and N as random effects. Tests of significance of fixed effects were accomplished by combining the appropriate linear combination of mean squares using Satterthwaite's (Satterthwaite, 1946) approximation with the DDFM = SATTERTH option in PROC MIXED.
Relationships among grain traits with bread and noodle quality traits were computed with either grain protein, test weight, or grain hardness as independent variables and individual bread or noodle quality traits as dependent variables using the moisture regime x location x N combination means for each cultivar (n = 28). Heterogeneity of slope among cultivars was evaluated with regression analysis with PROC GLM in SAS (SAS Institute, 1988), by testing for the interaction of the class variable, cultivar, and the independent continuous variable. The relationships between grain traits and bread and noodle quality traits were presented as Pearson's linear correlation coefficients for ease of comparison across relationships, as tests of significance for linear regression coefficient and linear correlation are equivalent (Steel and Torrie, 1980).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Main Effects of Treatments
Genotype was consistently the most important determinate of quality traits in both the irrigated and moisture-limited environments (Tables 2 and 3). The exceptional traits were the initial brightness (L*) of alkaline noodles and flour yield in irrigated environments where differences among genotypes were nonsignificant. Locations within the irrigated trials affected protein concentration (grain and flour), bread crumb yellowness (b*), initial brightness of the alkaline noodles, and most of the characteristics of Chinese noodles (Table 2). In contrast, the moisture-limited sites produced significant location effects for protein concentration (grain and flour), flour yield, and bread crumb yellowness (b*), but none of the Chinese noodle characters. Loaf volume was also affected by location in the moisture-limited sites (Table 3).
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Interactions among Main Effects
Few of the quality or agronomic traits were influenced by interactions among the main effects of location, N, or genotype in either the irrigated or moisture-limited environments. Only grain protein concentration in the irrigated trials and noodle hardness in the moisture-limited trials had a significant three-way interaction among the main effects. When location interactions with genotype were observed, they were smaller than the effects of genotype. Graybosch et al. (1996) used the ratio of cultivar F values to interaction F values to assess the relative importance of genotype x environment interaction. Applying that analysis to this data set, the smallest ratio of genotype to genotype x location was found for initial brightness of alkaline noodles in irrigated environments. Genotypic effects were not significant for initial brightness, and the F value for genotypes was only 1.7 times the magnitude of the significant genotype x location interaction. Because of the interaction of genotype x environment, initial brightness of the alkaline noodles may be difficult to improve through selection in irrigated environments, and likely would be difficult to predict on the basis of knowledge of the mean performance of cultivars or the location. The next smallest ratio of F values was found for flour ash, where the F value for genotype was five and six times greater than the genotype x environment interaction in the irrigated and moisture-limited environments, respectively.
Prediction of End Use from Grain Characteristics
In this research, we wanted to improve the understanding of whole grain characteristics that may be predictive of bread and noodle quality, and to determine if those trait associations were similar across cultivars. Grain characteristics were predictive of several important bread-making traits within cultivars (Table 4). Grain protein was negatively associated with flour ash for all cultivars, but responses varied with cultivars where r values ranged from –0.22 for Centennial to –0.80 for Lolo (Table 4). Grain protein was highly predictive for loaf volume (mean r = 0.83) and water absorption (mean r = 0.59). Increased test weight was always associated with decreased mixograph tolerance, but response varied with cultivar, and r values ranged from –0.13 for Centennial to –0.72 for Lolo. Test weight showed predictive value for both water absorption (mean r = –0.34) and loaf volume (mean r = –0.46), where associations were always negative for all cultivars. On average, grain hardness was not a reliable predictor of mixograph tolerance, water absorption, or loaf volume. Cultivars differed in response for grain hardness with flour ash. Centennial and Pomerelle, both soft textured wheats, showed lower correlations than the hard wheats (Table 4).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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In contrast to most end-use quality traits, location differences overshadowed genotype differences for grain yield (Tables 1, 2, and 3). This implies that cultivar selection by growers may be more meaningful in terms of end-use quality than for grain yield. However, the current pricing system whereby farmers are not paid for end-use quality means that growers place greater emphasis on grain yield than end-use quality traits when selecting cultivars.
Level of applied N was rarely important for end-use quality traits (Tables 2 and 3). When N application was significant, such as for grain protein in irrigated trials, genotype and location still tended to be more important. The lack of predictable effect of applied N probably relates to the unpredictable nature of production. In our experiments, two levels of fertilization included recommended levels for average predicted yield potential in each environment, and a level 15% below that recommended. In environments where actual rainfall limited yield potential, available N was probably in excess for both high and low treatments. In environments where rainfall exceeded expectations, available N was likely used by the plant for yield enhancement for both N levels. These results reflect the challenges faced by growers that may wish to manage a crop for a particular end use.
Genotypes performed relatively the same across locations and N levels for quality measures. No patterns emerged for interactions, as traits showing interactions were not consistent between the irrigated and moisture-limited trials. The similarity of genotype response across N levels might have arisen because N levels generally did not differ.
Although genotype had a major influence in the performance of grain in a specific end-use quality application, location effects also impacted fundamental properties of a given cultivar (Table 1). Thus, it would be desirable for growers and buyers to have the opportunity to determine the best end-use quality application for a given production lot based on measurable characteristics of the grain. In this regard, we looked at correlations among three grain characteristics that are simple to measure with end-use quality traits that may be ultimately important to grain buyers, and whether these relationships were specific to a given genotype. Bread quality traits were highly related to grain protein, as has been found in numerous studies (Peterson et al., 1992; Lang et al., 1998). For all traits, and especially final loaf volume, higher protein predicted desired changes in bread quality, meaning increased loaf volume, water absorption, dough strength measured by mixograph tolerance, and lower flour ash. On the other hand, higher test weight was associated with undesirable effects on bread quality traits. This presents somewhat of a dichotomy, as greater test weight is generally a positive factor in pricing grain.
Among noodle traits, color characteristics for Chinese noodles were most highly related to any grain characteristic (Table 5). High-protein grain tended to produce noodles with poor initial color and rapid color deterioration after they were manufactured. Alkaline noodle color traits were unrelated to grain protein. This is consistent with previous studies regarding the influence of protein on Chinese noodle color (Lang et al., 1998; Habernicht et al., 2002). Although protein can be an important determinant of color in an alkaline noodle (Miskelly, 1996), the higher pH of the alkaline noodle formula is closer to the optimum for polyphenol oxidase activity (Interesse et al., 1983). A number of studies have shown that polyphenol oxidase activity is related to the degree of time-dependent discoloration of noodles (Kruger et al., 1994; Baik et al., 1995; Park et al., 1997). Therefore, the elevated discoloration due to polyphenol oxidase activity tends to mask protein effects on color to a greater degree in alkali noodles than in Chinese noodles.
The positive effects of grain protein on both bread quality and noodle textural hardness suggests a synergy in management of wheat for both bread and noodle quality. Yet, the detrimental protein effect on noodle color creates an upper limit of acceptable protein concentration in most noodle flours. This suggests that to improve both textural and color components of Asian noodle quality, genotypes or environments that produce either (i) brighter flours against which the effects of the increasing protein concentration are minimized, or (ii) greater quality of protein per unit of protein to produce acceptable hardness values at lower protein concentrations. Selection experiments for components of protein quality such as loaf volume per concentration of protein could be used to verify the degree to which this conclusion can be generalized.
The large influence of genotypes noted may be reflective of the genotypes chosen. They span a wide range of gluten strength and grain protein concentration, and large genotype differences were to be expected. Klasic, Idaho 377s, Lolo, and MTHW9603 were considered dual-purpose wheats, while Hi-Line and the two soft wheats represented the extremes of good bread quality and traditional soft wheat product quality, respectively. A set of genotypes that spanned the range of bread and Asian noodle quality traits seemed appropriate to determine how and when genotypes might bridge across products (bread products vs. Asian noodles) to expand market opportunities. Furthermore, use of wheat in specialty bread products such as European and Chinese steam bread is increasing. Traditional pan bread traits, as measured here, are probably the best indicator of gluten strength and performance in other specialty bread products.
Our results have several implications. First, for the range of environmental conditions we encountered, it is apparent that genotype selection is critical for achieving a desired end use, with location effects being of secondary importance. Second, N management for a particular end use will be difficult, with N level being much less important than cultivar selection and location. Third, grain protein may be the best predictor of the suitability of a particular cultivar produced in a specific year for alternative end-use possibilities, with high-protein grain being most suitable for bread production, and low- and medium-protein, high-quality grain being more suitable for noodle production. And finally, genotypes tended to perform consistently across locations and N levels, and had a consistent relationship of grain traits with bread and noodle traits.
Received for publication February 25, 2003.
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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