Free Lipids in Air‐Classified High‐Protein Fractions of Hard Winter Wheat Flours and Their Effects on Breadmaking Quality

Free lipids (FL) were extracted from straight‐grade flours (SF) and the air‐classified high‐protein fractions (ACHPF) of nine hard winter wheats. The mean values of FL contents in 10 g (db) SF and ACHPF were, respectively, 92.8 and 178.5 mg for total FL, 74.1 and 141.9 mg for nonpolar lipids (NL), 12.8 and 20.9 mg for glycolipids (GL), and 4.9 and 12.0 mg for phospholipids (PL). FL compositions of SF and ACHPF showed nonsignificant differences in NL (80.7 and 81.1% of the FL) but significant differences in GL (13.9 and 12.0% of the FL) and PL (5.4 and 6.9% of the FL). Fortification of SF with ACHPF by blending to reach 13% protein content increased gluten quantity and thereby loaf volume but decreased gluten index, loaf volume regression, and crumb grain scores. NL contents showed significant relationships with dry gluten contents (r = 0.79) and gluten index (r = ‐0.83) values, indicating that high NL content in ACHPF could decrease gluten quality of fortified flours. Thus, an optimum balance should be maintained during fortification.     

Gluten,Pasting, and Mixograph Parameters of Hard Winter Wheat Flours in Relation to Breadmaking

Flour gluten, pasting, and mixogram characteristics of 12 hard winter wheat cultivars grown in six counties in Kansas were analyzed using the Glutomatic System, a Rapid Visco-Analyser, and MIXSMART computer software, respectively, to investigate their relationships with breadmaking. Gluten contents and hydration amounts had significant correlations with water absorption. In addition, gluten parameters were significantly correlated to kernel hardness. One of the most difficult challenges in mixograph usage is to find the optimum water absorption of a given flour. Flour protein contents (FP) and near-infrared hardness scores or FP and gluten parameters could predict mixograph water absorptions, showing R² values of 0.842 or 0.814, respectively, by multiple regression analysis. For our set of 72 wheat samples, computer-analyzed mixograph parameters were significantly correlated to conventional parameters. Computer-analyzed mixograph midline peak times and bandwidths at 6 min were highly correlated to conventional mixograph mix times and mixing tolerances, respectively. Flour pasting temperatures complemented FP in predicting loaf volumes. The ratios of FP to pasting temperatures had a significant curvilinear relationship with loaf volumes showing an R² of 0.725.     

Levels of Protein and Protein Composition in Hard Winter Wheat Flours and the Relationship to Breadmaking

Protein and protein fractions were measured in 49 hard winter wheat flours to investigate their relationship to breadmaking properties, particularly loaf volume, which varied from 760 to 1,055 cm³ and crumb grain score of 1.0–5.0 from 100 g of flour straight‐dough bread. Protein composition varied with flour protein content because total soluble protein (SP) and gliadin levels increased proportionally to increased protein content, but albumins and globulins (AG), soluble polymeric proteins (SPP), and insoluble polymeric protein (IPP) levels did not. Flour protein content was positively correlated with loaf volume and bake water absorption (r = 0.80, P < 0.0001 and r = 0.45, P < 0.01, respectively). The percent SP based on flour showed the highest correlation with loaf volume (r = 0.85) and low but significant correlation with crumb grain score (r = 0.35, P < 0.05). Percent gliadins based on flour and on protein content were positively correlated to loaf volume (r = 0.73, P < 0.0001 and r = 0.46, P < 0.001, respectively). The percent IPP based on flour was the only protein fraction that was highly correlated (r = 0.62, P < 0.0001) with bake water absorption followed by AG in flour (r = 0.30, P < 0.05). Bake mix time was correlated positively with percent IPP based on protein (r = 0.86) but negatively with percent SPP based on protein (r = ‐0.56, P < 0.0001).     

Prediction of Baking Characteristics of Hard Winter Wheat Flours Using Computer‐Analyzed Mixograph Parameters

The objective of this research was to determine whether computer‐analyzed (objective) mixograph parameters could replace conventional mixograph parameters in the evaluation of flour quality. The 642 hard winter wheat flours, collected from federal regional performance nurseries in 1995 and 1996, were analyzed by a conventional and computerized mixograph. Mixograph bandwidths at 6 min (BW6) showed the most significant linear correlation with subjective mixing tolerance scores (r = 0.81, P < 0.1%, n = 642). Prediction models of conventional and experimental baking parameters were developed by continuum regression using computer‐analyzed mixograph parameters of a calibration set (n = 282). The developed models could estimate conventional mixograph mixing time and tolerance scores, baking water absorption and mixing time, and bread loaf volume, showing R² values of 0.86, 0.74, 0.68, 0.80, and 0.51, respectively, for a validation set (n = 380). These results indicated that computer‐analyzed mixograph parameters could be applied to develop prediction models to be used for flour quality evaluation in wheat breeding programs.     

Variation in Polyphenol Oxidase Activity and Quality Characteristics Among Hard White Wheat and Hard Red Winter Wheat Samples

Polyphenol oxidase (PPO) has been related to an undesirable brown discoloration of wheat-based end products. Consumer acceptance and product quality are generally decreased by the darkening phenomena. Two sets of wheat samples (Triticum aestivum L.) were investigated for variation in grain and flour PPO levels. Samples included 40 advanced experimental hard white winter wheat lines grown at two Kansas locations and 10 hard red winter wheat genotypes grown at three Nebraska locations. The variability in grain and flour PPO activities was influenced by growing location and population for the hard white wheat samples. There also was a significant influence of population by growing location interactions on PPO activity in both grain and flour. Genotype and growing location both contributed to variability in flour PPO activity among the hard red wheat samples. The variation in flour PPO activities among growing locations appeared larger than variation produced by genotypes tested for the hard red wheat samples. Quality parameters, such as wheat physical properties, flour protein and ash contents, grain color, and milling yield significantly correlated with grain and flour PPO activities. Among red wheat samples, flour PPO activity was related to 100 kernel weight, first reduction flour yield, and flour ash content. Grain PPO activity was related to variation in grain color observed among hard white samples. The relationship of quality characteristics with grain and flour PPO activities varied among white and red wheat samples.     

Comparison of Asian Noodles from Some Hard White and Hard Red Wheat Flours

Asian noodles were prepared by an objective laboratory method that included adding optimum water to the dry ingredients, mixing the ingredients to homogeneous salt distribution, and sheeting of the dough under low shear stress. The lightness (L*) values of alkaline‐ and salt‐noodle doughs made from 65% extraction hard white wheat flours (except KS96HW115 flour at ≈70% extraction) were higher than those from 60% extraction hard red wheat flours (except Karl 92 flour at ≈70% extraction). A hard white spring wheat, ID377s, and a Kansas line of hard white winter wheat, KS96HW115, to be released in 2000, gave the highest L* values for dough sheets stored for 2 and 24 hr at 25°C. Cooking losses were 5–9 percentage points higher for alkaline noodles than salt noodles, but the cooking yields of the two types of Asian noodles were almost the same. Cooked alkaline noodles made from a high‐swelling flour (SP₉₃≈21 g/g) gave higher tensile strength than those made from several low‐swelling flours (SP₉₃ ≈15 g/g) with the same protein contents (≈12.5%). However, the cooked salt noodles gave the same tensile strength.     

Lipids in Japanese Noodle Flours

Lipids in Japanese salt and alkaline noodle flours and in Australian soft white wheat (SWW) flours were extracted and compared. Nonstarch lipid (NSL) and free lipid (FL) levels ranges were 1.33–1.71% and 0.84–1.04%, respectively, for nine Japanese salt noodle flours compared to 1.43–1.50% and 0.97–1.00% for three Australian SWW flours used mainly to prepare salt noodle. The six Japanese alkaline noodle flours averaged ≈15% less NSL and 20% less FL than the Australian flours. The NSL was separated by column chromatography into nonpolar lipid (NL), glycolipid (GL), and phospholipid (PL) fractions. The NSL extracted from salt noodle and Australian flours contained ≈36% more NL than that from alkaline noodle flour. The composition of NSL was similar for salt noodle and Australian SWW flours but was different for alkaline noodle flour. Japanese salt noodle flour could be differentiated from alkaline noodle flour by the higher levels of NSL and FL, although those elevated levels may be caused in part to the somewhat higher extraction rate for the salt-noodle flours. However, two parameters independent of extraction rate, the ratios of NL/PL and NL/ash were 47 and 15% higher, respectively, in the salt vs. alkaline noodle flours.     

Effect of Exogenous Lipase on Dough Lipids During Mixing of Wheat Flours

In control dough, endogenous wheat lipase was inactive, because the triacylglycerol (TAG), 1,2-diacylglycerol (DAG_1,2), and 1,3-diacylglycerol (DAG_1,3) fractions of nonpolar lipids were not affected by mixing. Conversely, the free fatty acid (FFA) and monoacylglycerol (MAG) fractions decreased, mainly due to the oxidation of polyunsaturated fatty acids (PUFA) catalyzed by wheat lipoxygenase. Addition of exogenous lipase to flour (15 lipase units [LU] per gram of dry matter) resulted in substantial modification of nonpolar lipids during dough mixing. Due to the 1,3 specificity of the lipase used in this experiment, the TAG and DAG_1,3 fractions decreased, whereas the MAG and FFA fractions increased. The DAG_1,2 fraction increased at the beginning of mixing and decreased after 40 min of mixing. Moreover, part of the PUFA released by lipase activity was oxidized by wheat lipoxygenase, resulting in major losses of PUFA. Conversely, the net content of the saturated and monounsaturated fatty acids (SMUFA) remained constant, because the free SMUFA content increased primarily at the expense of the esterified forms. For a constant mixing time of 20 min, increasing the amount of lipase added to dough (from 2.5 to 25 LU/g of dry matter) resulted in a linear decrease in the TAG fraction and a linear increase in the SMUFA content in the FFA fraction. At the same time, the PUFA content of the FFA fraction increased only for additions of lipase to flour of >5 LU/g of dry matter, due to partial oxidation by wheat lipoxygenase.     

Comparison of Quality Characteristics and Breadmaking Functionality of Hard Red Winter and Hard Red Spring Wheat

Various whole‐kernel, milling, flour, dough, and breadmaking quality parameters were compared between hard red winter (HRW) and hard red spring (HRS) wheat. From the 50 quality parameters evaluated, values of only nine quality characteristics were found to be similar for both classes. These were test weight, grain moisture content, kernel size, polyphenol oxidase content, average gluten index, insoluble polymeric protein (%), free nonpolar lipids, loaf volume potential, and mixograph tolerance. Some of the quality characteristics that had significantly higher levels in HRS than in HRW wheat samples included grain protein content, grain hardness, most milling and flour quality measurements, most dough physicochemical properties, and most baking characteristics. When HRW and HRS wheat samples were grouped to be within the same wheat protein content range (11.4–15.8%), the average value of many grain and breadmaking quality characteristics were similar for both wheat classes but significant differences still existed. Values that were higher for HRW wheat flour were color b*, free polar lipids content, falling number, and farinograph tolerance. Values that were higher for HRS wheat flour were geometric mean diameter, quantity of insoluble polymeric proteins and gliadins, mixograph mix time, alveograph configuration ratio, dough weight, crumb grain score, and SDS sedimentation volume. This research showed that the grain and flour quality of HRS wheat generally exceeds that of HRW wheat whether or not samples are grouped to include a similar protein content range.     

Physicochemical and Rheological Properties of Chinese Soft Wheat Flours and Their Relationships with Cookie‐Making Quality

The relationship of solvent retention capacity (SRC) values with four solvents, alveograph and farinograph properties, and cookie‐baking performance was evaluated with 20 Chinese soft wheat genotypes, including four cultivars and 16 advanced lines grown in the 2009–2010 season. Significant positive correlations were observed between water SRC (WSRC), sodium carbonate SRC (SOSRC), lactic acid SRC, and sucrose SRC (SUSRC) values. WSRC, SUSRC, and SOSRC showed significant positive correlations with farinograph water absorption (WA), alveograph P (tenacity), and P/L (ratio of tenacity to extensibility). Cookie diameter was significantly correlated with wet gluten (r = –0.491, P < 0.05), WSRC (r = –0.882, P < 0.001), SUSRC (r = –0.620, P < 0.01), SOSRC (r = –0.712, P < 0.001), P (r = –0.787, P < 0.001), L (r = 0.616, P < 0.01), P/L (r = –0.766, P < 0.001) and WA (r = –0.620, P < 0.01), respectively. SRC values were effective predictors of cookie quality in Chinese soft wheat. Alveograph parameters were more closely correlated to cookie quality than were farinograph parameters.     

Factors Governing Pasting Properties of Waxy Wheat Flours

Waxy wheat (Triticum aestivum L.) contains endosperm starch lacking in amylose. To realize the full potential of waxy wheat, the pasting properties of hard waxy wheat flours as well as factors governing the pasting properties were investigated and compared with normal and partial waxy wheat flours. Starches isolated from six hard waxy wheat flours had similar pasting properties, yet their corresponding flours had very different pasting properties. The differences in pasting properties were narrowed after endogenous α‐amylase activity in waxy wheat flours was inhibited by silver nitrate. Upon treatment with protease, the extent of protein digestibility influenced the viscosity profile in waxy wheat flours. Waxy wheat starch granules swelled extensively when heated in water and exhibited a high peak viscosity, but they fragmented at high temperatures, resulting in more rapid breakdown in viscosity. The extensively swelled and fragmented waxy wheat starch granules were more susceptible to α‐amylase degradation than normal wheat starch. A combination of endogenous α‐amylase activity and protein matrix contributed to a large variation in pasting properties of waxy wheat flours.     

Correlation of Quality Parameters with the Baking Performance of Wheat Flours

The baking performance of a set of flours from 13 wheat cultivars was determined by means of two different microscale baking tests (10 g of flour each). In the micro‐rapid‐mix test the dough was mixed for a fixed time at a high speed, whereas the microbaking test used mixing to optimum dough consistency in a microfarinograph. Quality parameters such as sedimentation value, crude protein content, dough and gluten extension data, and microfarinograph data were also determined. Finally, quality‐related protein fractions (gliadins, glutenins, SDS‐soluble proteins, and glutenin macropolymer) were quantitated by extraction/HPLC methods with reversed‐phase and gel‐permeation columns. All quality parameters were correlated with the bread volumes of both baking tests. The results demonstrated that the microbaking test (adapted mixing time) was much more closely related to the quality parameters than the micro‐rapid‐mix test (fixed mixing time), which hardly showed any correlation. Among the standard quality parameters, only the crude protein content showed a medium correlation with the bread volume of the microbaking test (r = 0.71), whereas the contents of gliadins (r = 0.80), glutenins (r = 0.76), and glutenin macropolymer (r = 0.80) appeared to be suitable parameters to predict the baking performance of wheat flour. All other quality parameters were not or were only weakly correlated and unsuitable for predicting baking performance.     

Alkaline‐Carbonate Noodles from Hard Winter Wheat Flours Varying in Protein,Swelling Power,and Polyphenol Oxidase Activity

The effects of wheat protein and starch on yellow‐alkaline noodles have not been fully clarified. Twenty‐four hard winter wheats with varying protein, hot‐water swelling power (SP₉₅), and polyphenol oxidase (PPO) activity were milled into long‐patent and short‐patent flours. Protein, SP₉₅, and PPO activity in the 48 flours were 8.2–12.9%, 16.2–24.1 g/g, and 80–157 ΔA₄₈₀/mg of protein/min, respectively. Lightness of raw noodles declined with increasing protein and PPO levels but yellowness decreased and then increased. Tensile force to break the cooked noodles was positively correlated with SP₉₅ and protein. Compression (50%) force of noodles made from flour with high SP₉₅ ≈21 g/g, averaged ≈20% below those made from low SP₉₅ ≈17 g/g of flour. Compression force was measured in the long dimension of a single noodle strand using a rectangular probe. The instrumental measurements suggest that alkaline noodles made from a single‐null partial‐waxy wheat with medium SP₉₅ ≈19.9 g/g will have a tender bite and a cohesive texture compared with those from a low SP₉₅ wheat with a hard bite and fracturable texture. Furthermore, alkaline noodles from a double‐null partial‐waxy wheat with high SP₉₅ will have an extra soft bite unless flour protein is above ≈12.5%. Hard‐white, dual‐purpose wheat should have a low level of PPO and, depending on the preferred noodle‐eating texture, a low to medium SP₉₅ level. Such wheats with medium protein levels (11–12%) are well suited for alkaline noodles because of improved color and surface smoothness, whereas the same wheats with 12–13% protein are well suited for bread. Wheats with medium SP₉₅ also reduce cooking loss and increase cooked yield.     

Protein Structural Features in Winter Wheat: Benchmarking Diversity in Ontario Hard and Soft Winter Wheat

A set of 32 winter wheat lines and varieties was selected to benchmark Ontario winter wheat as a first step toward improving quality. Protein secondary structure, total and accessible thiols, rheological properties, gluten aggregation kinetics, and network forming capabilities of different polymers were determined for each wheat line. Results revealed that there were statistically significant differences among the lines selected (P < 0.05). The differences between hard and soft wheat classes were not as large as would be expected, however, despite the range of quality parameters measured. Benchmarks revealed that several soft wheat lines outperformed hard wheat lines in standard breadmaking quality measures. Protein conformation changed significantly as the moisture content of the samples increased to mimic different model product systems: flour, dough, and batter. The conformation of the flour samples exhibited different patterns between hard and soft wheat classes, although these differences became narrower in the dough and batter states. Principal component analysis (PCA) factors included most quality parameters measured, with the notable exceptions of solvent retention capacity tests and total thiols. Protein conformation and accessible thiols were significant PCA factors that tended to override the rheological measures of quality they represented, suggesting that protein secondary structure and disulfide bonding patterns are fundamental aspects of rheological quality measures.     

Changes in the Element Composition of Flours during Maturation of the Winter Wheat Kernel

Abstract

An underappreciatel field of plant analysis is the change in the nutrient concentration of flours from winter wheat (Triticum aestivum L.) during maturation. The knowledge of these processes is important because breeding solely for higher yield has caused a decrease in the nutrient concentrations important for human nutrition. The difference in nutrient concentration of flours from grains of different spike positions is also an interesting field of plant analysis. The objective of this study was to study these processes to better understand the effect of these factors on flour quality. The concentration and amount of macro (nitrogen, phosphorus, potassium, calcium, magnesium) and micronutrients (copper, manganese, iron, zinc) were determined in the flours of grains of two genotypes from basal, central, and apical grain positions, from the 14th day to the 42th day after anthesis. Genotype and sampling time both affected the concentration of nutrients. The grain position on the head also influenced the N, Ca, K, Mn, P, and S concentrations. The amount of assimilated nutrients in flours increased until the middle of maturity, and then remained around specific values in the case of some elements. We describe the changes in concentrations of these nutrients based on changes in the assimilated mass.     

Quality of Hard Red Winter Wheat Grown Under High Temperature Conditions During Maturation and Ripening

High temperature during grain filling has been identified as a major factor in the end-use properties of bread wheat (Triticum aestivum L.). Our objectives were to assess the effect of high temperature during maturation on the grain characteristics, milling quality, and flour quality of hard red winter wheat. In three separate experiments, plants of wheat cultivar Karl 92 were subjected to regimes (day-night) of 20–20, 25–20, 30–20, and 35–20°C from 10 and 15 days after anthesis (DAA) until ripeness, and 25–20, 30–20, and 35–20°C from 20 DAA until ripeness. In other experiments, plants of wheat cultivars Karl 92 and TAM 107 were dried at 20 and 40°C, and spikes of Karl 92 were dried at different temperature and humidity conditions to asses the effects on quality of high temperature and drying rates during grain ripening. Flour yield correlated positively with kernel weight and diameter, test weight, and proportion of large kernels. Flour yield decreased as temperature increased and correlated negatively with hardness index and proportion of small grains. High growth temperatures and rapid grain desiccation decreased mixing time and tolerance of the flours. The greatest damage occurred when high temperature was maintained continuously from early grain filling until ripeness. Weakening of dough properties by rapid desiccation during ripening suggest that temperature, humidity, and possibly soil moisture all contribute to the final quality of bread wheat.     

Variation of Free Asparagine Concentration and Association with Quality Parameters for Hard Red Spring Wheat Grown in North Dakota

Free asparagine in wheat is known to be a precursor for the formation of acrylamide, which is unacceptable to consumers owing to its potential risks to human health. This research was performed to determine variation of free asparagine concentration (FAC) in hard red spring (HRS) wheat grown in North Dakota. Quality traits and FAC were analyzed for 75 HRS wheat genotypes grown at three locations. The ANOVA indicated that growing location had a strong effect on FAC. The main effect of genotype and interaction of genotype × location were also highly significant (P < 0.001). The genotype × location interaction was also explored graphically using a biplot of principal components calculated from the genotype and genotype × environment interaction model. The biplot analysis revealed that the pattern of interaction of genotype × location might be a noncrossover type. Certain HRS genotypes were identified to have consistently low FAC across growing locations. The FAC showed low genotypic correlations with quality traits, indicating low level of linkage between FAC and quality traits for HRS wheat genotypes.     

Amyloplast Formation and Starch Granule Development in Hard Red Winter Wheat

Plastids in the coenocytic endosperm of young wheat caryopses were mostly in the form of pleomorphic proplastids with a few of the plastids containing small starch granules. Following cellularization of the coenocytic cytoplasm, the outer one or two endosperm cell layers became meristematic and continued to divide until about 14 days after flowering (DAF). During the first week of endosperm development, newly divided cells had plastids that were pleomorphic in shape, while subaleurone cells interior to the meristematic region contained amyloplasts that contained a single‐size class of starch granules (incipient A‐type starch granules). The pleomorphic plastids exhibited tubular protrusions that extended a considerable distance through the cytoplasm. Amyloplasts in cells interior to the meristematic region did not exhibit protrusions. Both subaleurone and central endosperm cells had amyloplasts that exhibited protrusions at 10–12 DAF, and some of the protrusions contained small starch granules (incipient B‐type starch granules). Protrusions were not observed in endosperm amyloplasts at 14 DAF. Two sizes of starch, large A‐type and smaller B‐type granules were present within the cells, however. Amyloplast protrusions were numerous again at 17 DAF in both subaleurone and central endosperm cells; at 21 DAF, a third size class of small C‐type starch granules was observed in the cytoplasm. Amyloplasts in the endosperm of wheat apparently divided and increased in number through protrusions because binary fission typical of plastid division was never observed. Protrusions were observed in the coenocytic cytoplasm, in dividing cells, in subaleurone and central endosperm cells at 10–12 DAF, and in subaleurone and central endosperm cells at 17 DAF. The results suggest that there are three sizes of starch granules produced at specific times during wheat endosperm development.     

Quality Response of Twelve Hard Red Winter Wheat Cultivars to Foliar Disease Across Four Locations in Central Kansas

Twelve hard red winter wheat cultivars were grown at four locations in central Kansas to evaluate the role of foliar fungal diseases on wheat end-use quality in 1995. Disease was allowed to develop naturally on control plots and was controlled partially on plots treated with a systemic fungicide. After harvest, wheat samples were evaluated for the impact of the disease complex (leaf rust, tan spot, speckled leaf blotch) on physical grain quality, grain protein, milling properties, flour absorption, and peak mixing time. Data were analyzed using a mixed model to account for random (location and block) and fixed (cultivar and fungicide) effects. Location significantly influenced quality characteristics except kernel size and peak mixing time. The magnitudes of variation among random effects on all quality characteristics were larger for location than for the interactions between location × cultivar and location × fungicide. The fixed effects portion of the analysis revealed that the cultivar × fungicide treatment interaction significantly affected test weight, kernel protein, and flour absorption. Fungicide treatment resulted in significant increases in yield and kernel weight. Cultivar significantly affected all quality characteristics except kernel size and peak mixing time. Disease resistance exerted a significant influence on yield and test weight. The economic benefit associated with improved wheat quality from fungicide treatment was variety specific. Three cultivars (TAM 107, Karl 92, and Ike), which account for 50% of the 1997 planted wheat acres in Kansas, demonstrated positive improvements in test weight and protein in response to fungicide treatment.