B. A. Marchylo

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 ...

Temperature as a variable in reversed-phase high-performance liquid chromatographic separations of peptide and protein samples: II. Selectivity effects observed in the separation of several peptide and protein mixtures

Changes in band spacing as a function of temperature and/or gradient steepness were investigated for four peptide or protein samples. Reversed-phase HPLC in a gradient mode was used to separate tryptic digests of tissue plasminogen activator and calmodulin. Additionally, a synthetic peptide mixture and a storage protein sample from wheat were studied. Simultaneous changes in gradient steepness and temperature were found to provide considerable control over band spacing and sample resolution. The effects of temperature and gradient steepness on selectivity in these systems appear to be complementary. Simultaneous optimization of both temperature and gradient steepness thus represents a powerful and convenient means of controlling band spacing and separation. Because of the complexity of these sample chromatograms, computer simulation proved to be a useful tool in both interpreting these experiments and in optimizing final separations.

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...

Analysis of wheat gluten proteins by matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) was used to analyze the protein composition in several common and durum wheat varieties. Mass spectra were obtained directly from crude and partially purified wheat gliadin and reduced glutenin subunit fractions. Mass spectra of the gliadins and the low molecular weight (LMW) glutenin subunits show a complex pattern of proteins in the 30–40 kDa range. The observed gliadin patterns may be suitable for differentiation between wheat varieties, but the complexity of the mass spectra precludes the use of MALDI/MS as a stand-alone technique for the identification of most individual gliadin components. The mass spectra of the high molecular weight (HMW) glutenin subunits are much simpler and the complete HMW subunit profile can be determined directly from a single mass spectrum. This may prove particularly useful in wheat breeding programs for rapid identification of lines containing subunits associated with superior quality. The correspondence between previously identified HMW subunits and the mass spectral peaks was established with MALDI measurements of HPLC-separated subunits. Delayed extraction proved effective in improving the mass resolution for the monomeric gliadins and LMW glutenin subunit fractions, with masses less than 40 kDa. However, it gave little improvement for the HMW glutenin subunits which have masses of ∽80 kDa.

Effects of nitrogen fertilizer on protein quantity and gluten strength parameters in durum wheat (Triticum turgidum L. var. durum) cultivars of variable gluten strength

ABSTRACT Field studies were conducted over three years at two locations in Saskatchewan, Canada, to determine the effect of nitrogen fertilizer on protein quantity and protein strength in 10 cultivars of durum wheat (Triticum turgidum L. var. durum) representing a range of gluten strength. Increasing nitrogen fertilizer resulted in increased protein content in all cultivars across environments. Cultivars were clearly differentiated on the basis of gluten strength using a gluten index (GI), SDS sedimentation (SDSS), alveograph indices of overpressure (P) and deformation energy (W), mixograph energy to peak (ETP), and mixograph bandwidth energy (BWE) at all fertilizer levels. Variable cultivar response to nitrogen fertilizer was observed only for protein content, GI, and alveograph W. The nature of the cultivar-by-fertilizer interaction for GI suggested that the conventional strength cultivars would benefit more from nitrogen fertilizer than the extra-strong types, which showed no change or slight decreases...

Combined Effects of Endoxylanases and Reduced Water Levels in Pasta Production

ABSTRACT The combined effects on pasta properties of 1) varying dosages of endoxylanases (EC 3.2.1.8) from Aspergillus aculeatus and Bacillus subtilis and 2) lower levels of water during pasta dough processing were studied. The A. aculeatus endoxylanase has high selectivity toward water-extractable arabinoxylan (WE-AX), whereas B. subtilis endoxylanase preferentially hydrolyzes water-unextractable arabinoxylan (WU-AX). Pasta was produced on a microscale (50.0 g) from the semolinas of both a strong (AC Navigator) and a moderately strong (AC Avonlea) durum wheat cultivar. The levels of added water in endoxylanase-treated pastas were adjusted to obtain the same maximal farinograph consistencies as for the control pastas. The extruded pastas were dried with drying cycles at 40, 70, or 90°C. Apart from increasing levels of solubilized arabinoxylans, these treatments had little effect on the color, optimal cooking time, and firmness of the resulting pasta. High enzyme concentrations and low (40°C) drying temper...

Environmental conditions affect semolina quality in durum wheat (Triticum turgidum ssp. durum L.) cultivars with different gluten strength and gluten protein composition

BACKGROUND Sowing time may impact semolina and pasta cooking quality by changing the environmental conditions during grain filling. The effect of an optimum and a delayed sowing time on semolina quality was studied by comparing six cultivars under irrigation, in order to isolate temperature from drought effects. RESULTS Protein content was higher in the old cultivars and in the late sowings, according to the number of days with temperature between 30 and 40 °C during ripening. Gluten index increased as temperature rose to a threshold of about 30 °C, then decreased under higher temperatures. Mixograph parameters were less sensitive to high temperatures. Gliadin:glutenin correlated with gluten strength. Spaghetti firmness and protein content were positively correlated independently of sowing date. Cultivars Trinakria and Cappelli had the highest spaghetti firmness (900 and 828 g). CONCLUSIONS Late sowings may represent a way of increasing pasta cooking quality whenever they place grain filling under thermal conditions able to increase protein percentage, although the accompanying decrease in yield may represent a drawback in environments prone to drought stress during ripening. The lower protein percentages of modern durum wheat cultivars under conventional sowing times results in a lower pasta cooking quality despite higher gluten strength.

A Standardized Method for the Instrumental Determination of Cooked Spaghetti Firmness

ABSTRACT A standardized method to determine cooked spaghetti firmness was developed. The effects of process and instrument variables were investigated and optimized to provide reproducible results between laboratories and to enable discrimination among samples with similar firmness characteristics. Commercial spaghetti samples of varying thickness were chosen to artificially create a range in firmness, and used to investigate the effect of a wide range of variables on cooked spaghetti firmness including sample preparation, cooking procedure, postcooking treatment, sample presentation, and instrument settings. Cooked spaghetti firmness determined using a TA-XT2i texture analyzer was significantly affected by optimum cook time, postcook cooling, rest time, and crosshead speed (P < 0.001), as well as strand length, spaghetti to cooking water ratio, number of strands cut, and strand position (P < 0.05). Although previous work showed a reasonable correlation between laboratories when using in-house methods (r ...