Search

Search Results

• 1. [Article] Two Studies Addressing Practical Needs of Wheat Farmers, Processors, and Breeders : Changes in Falling Number and Alpha-amylase During Grain Storage, and Improved Predictions of Wheat-flour Dough Properties

  Wheat (Triticum aestivum) is a globally traded staple food crop. The diverse and pleasing nature of wheat-derived products is a result of the complex interactions of the polymeric components from the wheat ...

  Citation × Citation Citation Abstract Copy Title: Two Studies Addressing Practical Needs of Wheat Farmers, Processors, and Breeders : Changes in Falling Number and Alpha-amylase During Grain Storage, and Improved Predictions of Wheat-flour Dough Properties Author: Adams, Mike R. Wheat (Triticum aestivum) is a globally traded staple food crop. The diverse and pleasing nature of wheat-derived products is a result of the complex interactions of the polymeric components from the wheat endosperm. Changes in the functionality of these polymeric components, as a result of changes in growing conditions or different genetics, impacts market price and end-product quality and directly affects farmers and processors. Wheat is of particular economic importance to the U.S. Pacific Northwest and, specifically, to the state of Oregon. Providing quality wheat for export is paramount to the survival of the Oregon wheat industry. This dissertation focuses on wheat quality from the perspective of serving the practical needs of farmers, processors, and wheat breeders. The first study, split into two portions, concerns pre-harvest sprouting (PHS) and grain storage. PHS increases alpha amylase (αA) activity in wheat, which, in excess, reduces wheat end-product quality. Falling Number (FN) is the primary test used by industry to gauge PHS damage in wheats. Direct measurement of αA activity is the fundamental frame of reference. The objective of these studies was to determine if FN and αA activity of wheat samples changed during storage and if changes were a function of storage time, storage temperature, and degree of PHS damage. Samples from three Idaho locations were used. These captured a wide range of PHS degree, and therefore, wide ranges of FN values and αA activities. Samples were subdivided and stored at -20°C, +20°C, and +40°C. Low FN values and high αA activities were observed in soft wheats from locations that had rain events prior to harvest. Overall, FN and αA activity had the curvilinear relationship expected from the literature, indicating the validity of the sample set with regard to the FN/αA relationship. Changes in FN and αA activity were observed over a 90 day period of grain storage. FN differed between growing environments, wheat varieties, and storage temperatures. αA activity also differed between growing environments and wheat varieties, but not between storage temperatures. Highest rates of increase in FN were observed in hard wheats with high initial (day 0) FN values. Lowest rates of increase in FN were observed in soft wheats with low day 0 FN values. This contrasted with the changes that occurred in αA activity. Decreases in αA activity over storage time were most prevalent in soft wheats, particularly sprouted soft wheats (i.e. those with day 0 αA activities > 0.1 Ceralpha Units: CU). There were small decreases in αA activity in hard wheats but the distinction between high and low αA activity samples was not as evident as in the soft wheats because the vast majority of hard wheat samples tested had αA activities < 0.1 CU. Decreases in αA activity were in general not associated with corresponding increases in FN values over grain storage time. Increases in FN values occurred at a higher rates as storage temperature increased, particularly in hard wheats with high day 0 FN. Grain storage was successful as a way to raise FN values to > 300 s in very few cases. Storage was not effective in decreasing αA activity from > 0.1 CU to < 0.1 CU. Increases in FN over storage time for the hard wheats significantly differed between locations. However, decreases in αA activities over storage time for the hard wheats were not significantly different between locations. This again highlights a lack of correspondence between increased FN and decreased αA activity, suggesting that these two factors are somewhat decoupled when looking at changes in stored grain. Temperature-induced gluten crosslinking was explored as possible explanation for drastic increases in unsprouted hard wheat FN observed in samples from one location. Total polymeric protein (TPP) content was assessed at the end of the study for unsprouted hard wheats stored at +40°C and -20°C as well as sprouted hard wheats from stored at -20°C. TPP content was assessed as % large unextractable polymeric proteins (%LUPP) and % total unextractable polymeric proteins (%TUPP) using size exclusion high performance liquid chromatography (HPSEC). TPP content was not significantly different between storage temperatures for wheat varieties from the same location. %TUPP, but not % LUPP, was significantly lower in wheat varieties affected by PHS. Changes in FN at high storage temperature were not likely due to increased protein crosslinking. The second study aimed to validate the use of a rapid method for predicting dough strength at early generations in hard wheat breeding programs. Early generation quality screening improves breeding program efficiency. Hard wheats are used to make leavened bread products. The gluten proteins, particularly high molecular weight glutenin subunits (HMW-GS), form large, ramifying networks called the glutenin macropolymer (GMP). High GMP content is associated with increased dough strength and bread quality. Genetic differences in HMW-GS, and by inference, GMP, are responsible for differing dough properties between varieties. The Mixograph is used to measure dough mixing properties and predict end-product quality in breeding programs. GMP can also be measured as total polymeric protein (TPP) via HPSEC. The Solvent Retention Capacity (SRC) test has been proposed to predict hard wheat quality, specifically lactic acid SRC (LASRC). The objectives of this research were to provide preliminary information on the usefulness of using LASRC, on its own, to predict dough mixing properties, specifically as applied to early generation screening in a wheat breeding program, and to assess the relationship between LASRC and TPP. Wheat samples were categorized by flour protein concentration (FPC). Mixograph analysis was used as the baseline for dough properties and was analyzed both by eye and by the proprietary Mixsmart software. TPP content was assessed as %LUPP and %%TUPP. As a result of redundancy between the two TPP measures, only %LUPP was used for statistical analysis. Dough mixing parameters were slightly better correlated with LASRC than %LUPP. Correlations between LASRC, %LUPP, and dough mixing parameters were different between FPC categories, particularly in low FPC samples. A strict cutoff of 115% LASRC effectively screened out the bottom 10% of low quality hard wheats but retained a nearly equal amount of low quality hard wheats that would have been screened out by mixograph analysis. LASRC and %LUPP are not likely to be effective predictors of dough properties, but may have some value to screen for hard wheat quality in the early generations of a wheat breeding cycle. Title: Two Studies Addressing Practical Needs of Wheat Farmers, Processors, and Breeders : Changes in Falling Number and Alpha-amylase During Grain Storage, and Improved Predictions of Wheat-flour Dough Properties Author: Adams, Mike R. Wheat (Triticum aestivum) is a globally traded staple food crop. The diverse and pleasing nature of wheat-derived products is a result of the complex interactions of the polymeric components from the wheat endosperm. Changes in the functionality of these polymeric components, as a result of changes in growing conditions or different genetics, impacts market price and end-product quality and directly affects farmers and processors. Wheat is of particular economic importance to the U.S. Pacific Northwest and, specifically, to the state of Oregon. Providing quality wheat for export is paramount to the survival of the Oregon wheat industry. This dissertation focuses on wheat quality from the perspective of serving the practical needs of farmers, processors, and wheat breeders. The first study, split into two portions, concerns pre-harvest sprouting (PHS) and grain storage. PHS increases alpha amylase (αA) activity in wheat, which, in excess, reduces wheat end-product quality. Falling Number (FN) is the primary test used by industry to gauge PHS damage in wheats. Direct measurement of αA activity is the fundamental frame of reference. The objective of these studies was to determine if FN and αA activity of wheat samples changed during storage and if changes were a function of storage time, storage temperature, and degree of PHS damage. Samples from three Idaho locations were used. These captured a wide range of PHS degree, and therefore, wide ranges of FN values and αA activities. Samples were subdivided and stored at -20°C, +20°C, and +40°C. Low FN values and high αA activities were observed in soft wheats from locations that had rain events prior to harvest. Overall, FN and αA activity had the curvilinear relationship expected from the literature, indicating the validity of the sample set with regard to the FN/αA relationship. Changes in FN and αA activity were observed over a 90 day period of grain storage. FN differed between growing environments, wheat varieties, and storage temperatures. αA activity also differed between growing environments and wheat varieties, but not between storage temperatures. Highest rates of increase in FN were observed in hard wheats with high initial (day 0) FN values. Lowest rates of increase in FN were observed in soft wheats with low day 0 FN values. This contrasted with the changes that occurred in αA activity. Decreases in αA activity over storage time were most prevalent in soft wheats, particularly sprouted soft wheats (i.e. those with day 0 αA activities > 0.1 Ceralpha Units: CU). There were small decreases in αA activity in hard wheats but the distinction between high and low αA activity samples was not as evident as in the soft wheats because the vast majority of hard wheat samples tested had αA activities < 0.1 CU. Decreases in αA activity were in general not associated with corresponding increases in FN values over grain storage time. Increases in FN values occurred at a higher rates as storage temperature increased, particularly in hard wheats with high day 0 FN. Grain storage was successful as a way to raise FN values to > 300 s in very few cases. Storage was not effective in decreasing αA activity from > 0.1 CU to < 0.1 CU. Increases in FN over storage time for the hard wheats significantly differed between locations. However, decreases in αA activities over storage time for the hard wheats were not significantly different between locations. This again highlights a lack of correspondence between increased FN and decreased αA activity, suggesting that these two factors are somewhat decoupled when looking at changes in stored grain. Temperature-induced gluten crosslinking was explored as possible explanation for drastic increases in unsprouted hard wheat FN observed in samples from one location. Total polymeric protein (TPP) content was assessed at the end of the study for unsprouted hard wheats stored at +40°C and -20°C as well as sprouted hard wheats from stored at -20°C. TPP content was assessed as % large unextractable polymeric proteins (%LUPP) and % total unextractable polymeric proteins (%TUPP) using size exclusion high performance liquid chromatography (HPSEC). TPP content was not significantly different between storage temperatures for wheat varieties from the same location. %TUPP, but not % LUPP, was significantly lower in wheat varieties affected by PHS. Changes in FN at high storage temperature were not likely due to increased protein crosslinking. The second study aimed to validate the use of a rapid method for predicting dough strength at early generations in hard wheat breeding programs. Early generation quality screening improves breeding program efficiency. Hard wheats are used to make leavened bread products. The gluten proteins, particularly high molecular weight glutenin subunits (HMW-GS), form large, ramifying networks called the glutenin macropolymer (GMP). High GMP content is associated with increased dough strength and bread quality. Genetic differences in HMW-GS, and by inference, GMP, are responsible for differing dough properties between varieties. The Mixograph is used to measure dough mixing properties and predict end-product quality in breeding programs. GMP can also be measured as total polymeric protein (TPP) via HPSEC. The Solvent Retention Capacity (SRC) test has been proposed to predict hard wheat quality, specifically lactic acid SRC (LASRC). The objectives of this research were to provide preliminary information on the usefulness of using LASRC, on its own, to predict dough mixing properties, specifically as applied to early generation screening in a wheat breeding program, and to assess the relationship between LASRC and TPP. Wheat samples were categorized by flour protein concentration (FPC). Mixograph analysis was used as the baseline for dough properties and was analyzed both by eye and by the proprietary Mixsmart software. TPP content was assessed as %LUPP and %%TUPP. As a result of redundancy between the two TPP measures, only %LUPP was used for statistical analysis. Dough mixing parameters were slightly better correlated with LASRC than %LUPP. Correlations between LASRC, %LUPP, and dough mixing parameters were different between FPC categories, particularly in low FPC samples. A strict cutoff of 115% LASRC effectively screened out the bottom 10% of low quality hard wheats but retained a nearly equal amount of low quality hard wheats that would have been screened out by mixograph analysis. LASRC and %LUPP are not likely to be effective predictors of dough properties, but may have some value to screen for hard wheat quality in the early generations of a wheat breeding cycle. Close

• 2. [Article] Investigations of gluten proteins from functional and historical perspective

  Wheat (Triticum aestivum) is one of the world’s major staple food crops, with flour produced from starchy endosperm being used for breads, cakes, noodles and various other wheat-based foods. The unique ...

  Citation × Citation Citation Abstract Copy Title: Investigations of gluten proteins from functional and historical perspective Author: Zhang, Ying Wheat (Triticum aestivum) is one of the world’s major staple food crops, with flour produced from starchy endosperm being used for breads, cakes, noodles and various other wheat-based foods. The unique bread making properties of wheat are primarily attributed to its gluten-forming storage proteins: gliadins and glutenins. This study investigated the gluten proteins from functional and historical perspectives. The first study examined primarily the functional role of gluten proteins in the outcomes of the standard Falling Number (FN) test. The FN test is used in the grain trade to screen delivered wheat for the presence of pre-harvest sprouting by indirectly measuring α-amylase through it effects on the physical consistency of a cooked flour-water suspension. Grain protein content (GPC) has been implicated as a potential modifier of FN independent of α-amylase or sprout status. In the gluten functionality study, we proposed a protein unfolding and crosslinking model, and hypothesized that gluten proteins with higher molecular weight distributions (MWD) would heatset faster, tightly cover starch granules, restrict water entry, and slow their disintegration. In contrast to our hypothesis, our results showed that samples with lower MWD had faster heatset times than samples with higher MWD according to a controlled heating test. We also hypothesize that increased granularity of hard wheat flour reduces the surface area to volume ratio so the starch granules embedded in the particles need more time to hydrate or swell. However, our results indicated that natural variations in flour particle size from a standard grinding procedure that used a 0.8 mm screen had no impact on FN. The second study looked at potential changes in gluten proteins in a historical set of wheat varieties spanning more than 110 years of production. The wheats were in two sets: soft wheats where there has been no systematic selection for increased dough strength in breeding programs, and hard wheats where there has been a concerted effort to increase overall dough strength over the last century. The sample sets also covered the eras before and after the introduction of the semi-dwarf wheats to the USA. The reason for this investigation is related to the circumstance that wheat is the cause of celiac disease (CD) and is implcated in the disputed condition, non-celiac gluten sensitivity (NCGS). Recently, diagnoses of CD at least have increased and there are suggestions that changes in gluten proteins in the modern era are responsible. Since it is primarily gliadins that trigger CD, it was considered worth investigating whether or not there have been any changes in the composition of gliadins over the last century. Sixty-two soft and 61 hard U.S. high production wheat varieties from 1900 to the present (with one from 1800) were collected and analyzed by RP-HPLC. These varieties were investigated to begin to answer whether wheat breeding for higher dough strength, or the incorporation of dwarfing alleles after the 1960s, was associated with observable changes in gliadin composition. ANOVA showed that there was no significant difference between soft and hard wheats in the relative abundance of α/β-gliadins. However, there were significant differences between hard and soft wheats in the relative abundance of ω- and γ-gliadins. ANOVA also showed that there was no significant difference between tall and dwarf wheats in the relative abundance of any of the three gliadin fractions. The ANOVA results suggested that deliberate breeding for dough strength, as illustrated by the hard versus soft wheat contrast, had not systematically changed the relative abundance of α/β-gliadins across the last 110 years, but had altered the relative abundance of the other two fractions. ANOVA results indicated no change in proportions of the three gliadin fractions after deployment of the dwarfing alleles suggesting the tall to dwarf change was independent of gluten composition. Second order polynomial regression analyses showed that the relative abundance of α/β-gliadins increased until around 1960 then decreased. The changes were more noticeable in the hard wheats. The converse was observed for ?-gliadins. This stepwise change questioned the association between CD increase and breeding for increased dough strength in hard wheats, since the relative abundance of α/β-gliadins did not keep going up, and α-gliadin is considered the major trigger force for CD initiation. In contrast, linear correlation analyses with each of 700, three second long fractions of the RP-HPLC chromatograms suggested that most changes were related to the soft wheat population. The discrepancy between the regression analyses of the three major fractions and the 700 small fractions may be related to the use of linear correlations in the latter when some relationships were clearly non-linear. Overall, our results did not fully support speculations that there have been profound changes in gluten composition related to the dwarfing alleles or selection for increased dough strength in hard wheats. Title: Investigations of gluten proteins from functional and historical perspective Author: Zhang, Ying Wheat (Triticum aestivum) is one of the world’s major staple food crops, with flour produced from starchy endosperm being used for breads, cakes, noodles and various other wheat-based foods. The unique bread making properties of wheat are primarily attributed to its gluten-forming storage proteins: gliadins and glutenins. This study investigated the gluten proteins from functional and historical perspectives. The first study examined primarily the functional role of gluten proteins in the outcomes of the standard Falling Number (FN) test. The FN test is used in the grain trade to screen delivered wheat for the presence of pre-harvest sprouting by indirectly measuring α-amylase through it effects on the physical consistency of a cooked flour-water suspension. Grain protein content (GPC) has been implicated as a potential modifier of FN independent of α-amylase or sprout status. In the gluten functionality study, we proposed a protein unfolding and crosslinking model, and hypothesized that gluten proteins with higher molecular weight distributions (MWD) would heatset faster, tightly cover starch granules, restrict water entry, and slow their disintegration. In contrast to our hypothesis, our results showed that samples with lower MWD had faster heatset times than samples with higher MWD according to a controlled heating test. We also hypothesize that increased granularity of hard wheat flour reduces the surface area to volume ratio so the starch granules embedded in the particles need more time to hydrate or swell. However, our results indicated that natural variations in flour particle size from a standard grinding procedure that used a 0.8 mm screen had no impact on FN. The second study looked at potential changes in gluten proteins in a historical set of wheat varieties spanning more than 110 years of production. The wheats were in two sets: soft wheats where there has been no systematic selection for increased dough strength in breeding programs, and hard wheats where there has been a concerted effort to increase overall dough strength over the last century. The sample sets also covered the eras before and after the introduction of the semi-dwarf wheats to the USA. The reason for this investigation is related to the circumstance that wheat is the cause of celiac disease (CD) and is implcated in the disputed condition, non-celiac gluten sensitivity (NCGS). Recently, diagnoses of CD at least have increased and there are suggestions that changes in gluten proteins in the modern era are responsible. Since it is primarily gliadins that trigger CD, it was considered worth investigating whether or not there have been any changes in the composition of gliadins over the last century. Sixty-two soft and 61 hard U.S. high production wheat varieties from 1900 to the present (with one from 1800) were collected and analyzed by RP-HPLC. These varieties were investigated to begin to answer whether wheat breeding for higher dough strength, or the incorporation of dwarfing alleles after the 1960s, was associated with observable changes in gliadin composition. ANOVA showed that there was no significant difference between soft and hard wheats in the relative abundance of α/β-gliadins. However, there were significant differences between hard and soft wheats in the relative abundance of ω- and γ-gliadins. ANOVA also showed that there was no significant difference between tall and dwarf wheats in the relative abundance of any of the three gliadin fractions. The ANOVA results suggested that deliberate breeding for dough strength, as illustrated by the hard versus soft wheat contrast, had not systematically changed the relative abundance of α/β-gliadins across the last 110 years, but had altered the relative abundance of the other two fractions. ANOVA results indicated no change in proportions of the three gliadin fractions after deployment of the dwarfing alleles suggesting the tall to dwarf change was independent of gluten composition. Second order polynomial regression analyses showed that the relative abundance of α/β-gliadins increased until around 1960 then decreased. The changes were more noticeable in the hard wheats. The converse was observed for ?-gliadins. This stepwise change questioned the association between CD increase and breeding for increased dough strength in hard wheats, since the relative abundance of α/β-gliadins did not keep going up, and α-gliadin is considered the major trigger force for CD initiation. In contrast, linear correlation analyses with each of 700, three second long fractions of the RP-HPLC chromatograms suggested that most changes were related to the soft wheat population. The discrepancy between the regression analyses of the three major fractions and the 700 small fractions may be related to the use of linear correlations in the latter when some relationships were clearly non-linear. Overall, our results did not fully support speculations that there have been profound changes in gluten composition related to the dwarfing alleles or selection for increased dough strength in hard wheats. Close