J. E. Dexter

Phenolic content and antioxidant activity of pearled wheat and roller-milled fractions

ABSTRACT Wheat contains phenolic compounds concentrated mainly in bran tissues. This study examined the distribution of phenolics and antioxidant activities in wheat fractions derived from pearling and roller milling. Debranning (pearling) of wheat before milling is becoming increasingly accepted by the milling industry as a means of improving wheat rollermilling performance, making it of interest to determine the concentration of ferulic acid at various degrees of pearling. Eight cultivar samples were used, including five genotypes representing four commercial Canadian wheat classes with different intrinsic qualities. Wheat was pearled incrementally to obtain five fractions, each representing an amount of product equivalent to 5% of initial sample weight. Wheat was also roller milled without debranning. Total phenolic content of fractions was determined using the modified Folin-Ciocalteau method for all pearling fractions, and for bran, shorts, bran flour, and first middlings flour from roller milling. A...

Physicochemical properties of hull-less barley fibre-rich fractions varying in particle size and their potential as functional ingredients in two-layer flat bread

The performance of barley fibre-rich fractions (FRF), as high dietary fibre ingredients, in two-layer flat bread was investigated. In addition, the effects of particle size reduction by pin milling on functional properties of FRF were studied. FRF enriched in non-starch polysaccharides (β-glucans and arabinoxylans) were obtained by roller milling of hull-less barley. Pin milling (PM) of FRF significantly reduced their particle size, slightly increased the solubility of β-glucans and arabinoxylans, and increased the viscosity of water slurries containing FRF. The addition of 20% of barley FRF to wheat flour significantly increased dough water absorption and weakened the dough properties, as indicated by farinograph mixing curves, but the FRF-enriched doughs exhibited good handling characteristics at the dividing and sheeting stages. The appearance, diameter, layer separation, crumb, and aroma of the FRF-enriched flat breads were comparable to that of the control. The PM of FRF did not significantly affect the dough handling or the quality characteristics of flat breads. The addition of 20% of barley FRF to wheat flour flat bread provided substantial health benefits by significantly increasing the total and soluble dietary fibre contents and by decreasing starch digestibility.

Fusarium Head Blight: Effect of Fungal Proteases on Wheat Storage Proteins

ABSTRACT The effect of proteolytic enzymes, associated with Fusarium head blight, on wheat storage proteins and dough functionality was studied. Fusarium damaged kernels (FDK) and sound kernels were hand-picked from F. graminearum Schwabe and F. avenaceum (Fr.) Sacc. infected samples of bread and durum wheat. Scanning electron microscopy revealed significant degradation of endosperm protein in FDK. Storage proteins from FDK and sound kernels were analyzed by SDS-PAGE, RP-HPLC, and SE-HPLC. Total storage protein was lower in FDK but no significant qualitative differences in protein were detected by either RP-HPLC or SDS-PAGE. SE-HPLC was used to follow the hydrolysis of wheat storage protein by proteolytic enzymes found in FDK and a pure culture of F. graminearum. Selective inhibition of proteolytic activity by p-chloromercuribenzoate, and not soybean trypsin inhibitor or iodoacetic acid, suggests that the F. graminearum protease is an alkaline protease. Farinograph and extensigraph curves showed that the ...

Effect of Fusarium head blight on semolina milling and pasta-making quality of durum wheat.

ABSTRACT Ten durum wheat cultivars harvested in Manitoba in 1995, which were downgraded primarily because of fusarium-damaged (FD) kernels, were subjected to mycological tests and evaluated for semolina milling and pasta-making quality. Fusarium graminearum was the primary fungus infecting kernels. The ratio of FD to deoxynivlaenol (DON) level varied slightly among cultivars but was generally near unity. Retention of DON in semolina was about 50%. FD had a negative impact on kernel weight and test weight, resulting in lower semolina yield. Semolina ash content and bran specks were not affected by FD, but semolina became duller and redder. FD had no effect on protein content, but gluten strength was weaker probably due to a lower proportion of glutenins as shown by reversed-phase high-performance liquid chromatographic analysis of sequentially extracted gluten proteins. The influence of FD on gluten strength was not sufficient to alter pasta texture. FD had a strong adverse effect on pasta color. Even for ...

Relationship of creep-recovery and dynamic oscillatory measurements to durum wheat physical dough properties

ABSTRACT Durum wheat gluten strength is important in determining extrusion properties and pasta cooking quality. Durum wheats varying in strength were tested using an alveograph and a 2-g micro-mixograph, both widely accepted techniques for determination of physical dough properties. Doughs from the 2-g micro-mixograph were characterized by dynamic oscillatory and large deformation creep tests using a controlled stress rheometer. Mechanical properties obtained from both testing regimes were strongly correlated with many of the parameters provided by the alveograph and micro-mixograph. Maximum strain attained after 5 min creep ranged from 25% for the weakest cultivar, with a coefficient of variation among replicates of 16,000 Pa for the strongest, least extensible cultivars, with a coefficient of variation of ...

Effects of Flour Particle Size and Starch Damage on Processing and Quality of White Salted Noodles

ABSTRACT Several reduction grinding conditions were used on a Canadian Western Red Spring (CWRS) farina to yield flours of comparable protein content within three specific particle size ranges (132–193, 110–132, 85–110 μm) at three starch damage levels (3.0, 3.9, 7.0 Megazyme units). White salted noodles (1% w/w NaCl) were initially processed at a fixed absorption (32%). Dynamic oscillatory and large deformation creep measurements indicated that doughs with lower starch damage, thick or thin, exhibited lower G′ (storage modulus), higher tan δ (G″ [loss modulus]/G′) values, and greater maximum strain during creep than doughs with higher starch damage. There were no clear trends between work input during sheeting and either starch damage or particle size. Instrumental texture analysis of raw noodles showed no significant differences due to either starch damage or flour particle size. Flours with fine particle size gave cooked noodles with the best textural attributes, whereas starch damage exhibited no cons...

Effect of Environment and Genotype on Durum Wheat Gluten Strength and Pasta Viscoelasticity

ABSTRACT Data on the quality of durum wheat genotypes grown under eight environments (site-year combinations) were evaluated to determine the relative effects of genotype and environment on quality characteristics associated with gluten strength, protein content, and pasta texture. The 10 durum wheat genotypes assessed in this study represented a range of gluten strength types from the very strong U.S. desert durum genotype, Durex, to the medium strength Canadian genotype, Plenty. Considerable genetic variability was detected for all quality characteristics studied. Genotype-environment interaction was significant for all quality parameters evaluated, with the exception of mixograph development time. Genotypeenvironment interaction was most important in determining protein content and least important in determining gluten index, gluten viscoelasticity, and SDS sedimentation volume. The nature of the genotype-environment interaction was evaluated by determining the number of significant crossover (rank cha...

Role of Gluten and Its Components in Determining Durum Semolina Dough Viscoelastic Properties

ABSTRACT Gluten was isolated from three durum wheat cultivars with a range in strength. Gluten was further fractionated to yield gliadin, glutenin and high molecular weight (HMW) and low molecular weight (LMW) glutenin subunits (GS). The gluten and various fractions were used to enrich a base semolina. Enriched dough samples were prepared at a fixed protein content using a 2-g micromixograph. Mixing strength increased with addition of gluten. Dynamic and creep compliance responses of doughs enriched with added gluten ranked in order according to the strength of the gluten source. Gliadin addition to dough resulted in weaker mixing curves. Gliadin was unable to form a network structure, having essentially no effect on dough compliance, but it did demonstrate its contribution to the viscous nature of dough (increased tan δ). Source of the gliadin made no difference in response of moduli or compliance. Addition of glutenin to the base semolina increased the overall dough strength properties. Glutenin source ...

Starch Participation in Durum Dough Linear Viscoelastic Properties

ABSTRACT The contribution of starch to dough rheological properties has been largely overshadowed by the role of gluten, receiving much less attention in comparison. The influence of starch granule surface properties on durum wheat dough linear viscoelasticity was investigated, and surface interactions between starch granules and gluten were assessed using a model system. Proportions of starch were substituted in dough on a volume basis with an inert filler (glass powder) with a similar particle size range. The doughs were subjected to dynamic and creep measurements. Dough linear viscoelastic properties were weakened on substitution of starch with glass powder at ≤50% substitution, inferring a reduction in adhesion at the matrix-filler (starch and glass powder) interface with declining proportions of starch granules. Surface modification of starch granules or glass powder altered dough rheological properties, confirming the importance of starch granule surface characteristics and the nature of protein-sta...

Roller Milling of Canadian Hull-less Barley: Optimization of Roller Milling Conditions and Composition of Mill Streams

ABSTRACT Roller milling of hull-less barley generates mill streams with highly variable β-glucan and arabinoxylan (AX) content. For high β-glucan cultivars, yields >20% (whole barley basis) of a fiber-rich fraction (FRF) with β-glucan contents >15% can be readily obtained with a simple short mill flow. Hull-less barley cultivars with high β-glucan content require higher power consumption during roller milling than normal β-glucan barley. Recovery of flour from high β-glucan cultivars was greatly expedited by impact passages after grinding, particularly after reduction roll passages. Pearling before roller milling reduces flour yield and FRF yield on a whole unpearled barley basis, but flour brightness is improved and concentration of β-glucan in fiber-rich fractions increases. Pearling by-products are rich in AX. Pearling to 15–20% is the best compromise between flour and FRF yield and flour brightness and pearling by-products AX content. Increasing conditioning moisture from 12.5 to 14.5% strongly improv...