W. Bushuk

Oxidative gelation studies of water-soluble pentosans from wheat

The gel formation potential of purified wheat water-soluble pentosans and their fractions, arabinoxylan and arabinogalactan, in the presence of H 2 O 2 /peroxidase was investigated by small amplitude oscillatory rheological measurements. Gelation proceeded in two stages: a rapid increase in gel rigidity ( G ´) during the first hour, followed by a much lower rate of gel development thereafter. Disappearance of feruloyl groups coincided with the first stage of the gelation process. Gel permeation chromatography on 8epharose CL-4B and Sephacryl 8-300 revealed that only arabinoxylan actively participated in the network. The rate and extent of gel rigidity development was dependent on polymer and oxidant concentration. Temperature had a negative effect on the gelation process. Gel network development with FeCl 3 was similar to that with H 2 O 2 /peroxidase, while (NH 4 ) 2 S 2 O 8 induced gelation at a much lower rate. The cross-linked pentosans and arabinoxylan held up to 100 g of H 2 O per g of polymer.

Discrimination of wheat class and variety by digital image analysis of whole grain samples

The application of digital image analysis for objective classification of wheat cultivars according to kernel type and identity was studied. Plan-form spatial shape features and Fourier descriptors of kernel perimeters were automatically determined from computed whole-grain contours. Perfect type classification was obtained for four durum wheat varieties in admixture with ten common wheats representing a broad range of kernel types. Likewise, samples of each of five Canada Western Red Spring (CWRS) wheat varieties were all correctly allocated to the CWRS class. None of 432 kernels of contrasting wheat classes was misclassified as CWRS wheat. Discrimination of Canada Western Red Winter, Canada Western Soft White Spring, Canada Utility and Canada Prairie Spring wheats was less satisfactory. Discrimination of varieties within classes gave inconclusive results with correct classification scores ranging from 15 to 96%.

An instrumental system for cereal grain classification using digital image analysis

A digital image processing system is described to facilitate objective inspection and classification of cereal grains. Digitized images of whole grain samples of hard red spring wheat, barley, rye and oats were obtained using a charge-coupled device (CCD) video camera interfaced to a custom-built data-acquisition system. Computer programs were written in assembly language for acquisition and preliminary processing of data from the CCD camera. FORTRAN77 programs were developed for image segmentation and feature extraction. Computed grain features include kernel length, width, area, aspect and thinness ratios, contour length and normalized central moments. Size and shape parameters were evaluated with regard to discrimination ability by stepwise discriminant analysis. Canonical discriminant analysis was applied to visualize cereal class differences and a linear discriminant model was derived. Approximately 1% of over 1100 kernels tested were incorrectly classified among wheat, oats, barley and rye in a four-way admixture. The feasibility of the methodology for instrumental determination of foreign material (‘Besatz’) in grain grading is discussed.

Wheat grain colour analysis by digital image processing I. Methodology

A colour digital image processing workstation has been developed to evaluate instrumentally the colour of individual cereal grains and other objects identified within digital images. Digital colour images were acquired by video digitization of the RGB (red, green, blue) signals produced by a Saticon-type video camera. A low-cost microcomputer-frame grabber system was used to control digitization, to perform image segmentation and to extract colour features. The equipment and methodology for colour measurement are described. Colour attributes of cultivars belonging to different wheat classes were examined. In general, significant differences were discerned between varieties of different class (e.g. amber durum and hard red) and some varieties within the same class (e.g. hard red spring varieties Neepawa and Columbus).

Effects of Wheat Bug (Eurygaster maura) Protease on Glutenin Proteins

ABSTRACT Proteolytic degradation of 50% 1-propanol insoluble (50PI) glutenin of six common wheat cultivars by wheat bug (Eurygaster maura) protease was investigated using reversed-phase HPLC. Wheat at the milk-ripe stage was manually infested with adult bugs. After harvest, bug-damaged kernels were blended (2:1, kernel basis) with undamaged grain of the same cultivar. Samples of ground wheat were incubated in distilled water for different times (0, 30, 60, and 120 min). The incubated whole meal samples were subsequently freeze-dried and stored until analysis. The degree of proteolytic degradation of 50PI glutenin was determined based on the quantity of total glutenin subunits (GS), high molecular weight GS (HMW-GS), and low molecular weight GS (LMW-GS). For ground wheat samples incubated for ≥30 min, 50PI glutenin was substantially degraded as evidenced by a >80% decrease on average in total GS, HMW-GS, and LMW-GS. Some cultivars showed different patterns of glutenin proteolysis as revealed by differences...

Wheat grain colour analysis by digital image processing. II: Wheat class discrimination

The extent to which wheat grain colour, objectively measured by video colorimetry, can be used to distinguish kernel type according to wheat class and variety was investigated. Discriminant analyses were performed based on mean red (R), green (G) and blue (B) pixel reflectance (tristimulus) features obtained by colour digital image analysis. Colour data collected from individual kernels of 10 cultivars representing six Canadian wheat classes were used to develop discriminant models. Pairwise discrimination between selected varieties representing the different wheat classes was achieved with considerable success. Over all pairwise trials, 88 % correct varietal classification was achieved on average. In pairwise trials between certain red-grained varieties (cvs), e.g. Neepawa, Norstar or Glenlea and amber durum cv. Wakooma or white spring wheat cv. Owens, correct classification exceeded 96%. A more demanding discrimination problem of correctly classifying grain of single wheat varieties according to official grade class was also posed. Correct classification scores for individual varieties varied from 34 to 90%. Average correct classification scores for the Canada Western Soft White Spring, Amber Durum and Red Spring classes of wheat were 76, 76 and 62 %, respectively. Relatively lower scores of 56 and 34 % were achieved for the Canada Western Hard Red Winter and Canada Prairie Spring wheat classes. The average correct classification for hard red spring type kernels was approximately 90 %.

Effects of gamma-irradiation of wheat on gluten proteins

Abstract The effects of 60Co gamma-irradiation treatments (2·5, 5·0, 10·0 and 20·0 kGy) on the gluten proteins of two bread wheats and one durum wheat cultivar were investigated. Dough rheological properties of the flour processed from the irradiated wheat were also determined using a computerised micromixograph. Irradiation caused a significant deteriorating effect on all mixogram parameters. There was no observable effect of irradiation on gliadin proteins analysed by polyacrylamide gel electrophoresis. The 50% 1-propanol-insoluble (50 PI) glutenin fraction was highly affected by irradiation. By sodium dodecyl sulfate polyacrylamide gel electrophoresis, reduced 50 PI glutenin showed a noticeable reduction in band intensities of both high (HMW) and low molecular weight (LMW) glutenin subunits (GS) with increasing irradiation dosage greater than 5 kGy. The irradiation effect on 50 PI glutenin was further studied and quantified by reversed-phase high-performance liquid chromatography of glutenin subunits; there was a progressive decrease in the quantity of subunits with increasing irradiation dose level. Compared to non-irradiated wheat, the relative decline in total insoluble glutenin at the 20 kGy dosage level ranged from 34–49% depending on cultivar. Increasing levels of irradiation also progressively reduced the ratio of HMW:LMW-GS up to 13–15% at 20 kGy indicating that irradiation had a greater effect on the largest polymers of glutenin. The observed weakening of dough mixing properties and concomitant decline in the quantity of 50 PI glutenin with increasing levels of gamma-irradiation are consistent with a degradation of glutenin to a lower average molecular size by depolymerisation and/or disaggregation.

Comparison of physical properties of raw and roasted chickpeas (leblebi)

Abstract Physical properties of raw and roasted chickpeas (leblebi) were examined as a basis for evaluating the changes in structure and color that occur during leblebi production. Scanning electron microscopy (SEM) revealed that substantial structural changes occurred during processing. The raw chickpea was tightly packed while processing substantially increased the porosity of the chickpeas. The density measurement confirmed the SEM results. There were significant differences in the stiffness values of raw and roasted chickpea samples. The majority of the starch granules in the roasted chickpea sample retained strong birefringence. The roasted chickpea sample had a DSC endotherm at around 65°C comparable in size to that in raw chickpea, indicating that starch was not gelatinized during processing. Although there were slight differences in the X-ray diffraction patterns of the raw and roasted chickpea samples, they were both Ca type. The roasted chickpeas had lower L and higher a + and b + values compared to that of raw chickpeas. ©

Wheat intercultivar differences in susceptibility of glutenin protein to effects of bug (Eurygaster integriceps) protease

ABSTRACT Preharvest bug damage to wheat can cause significant losses in bread-making quality. One of the most prevalent forms of bug damage which frequently occurs in most countries of the Middle East, Eastern Europe and North Africa can be attributed to Heteropterous insects, particularly Eurygaster spp. Intercultivar differences in the susceptibility of glutenin to proteolytic degradation by the bug Eurygaster integriceps were investigated using six breadwheat cultivars of Turkish origin. Crude enzyme extract was prepared with distilled water from bug-damaged wheat. The freeze-dried extract was blended with sound samples of ground wheat, and the mixture was incubated in distilled water for 30 and 60 min at 37°C and subsequently freeze-dried. The proteolytic effects of bug damage were determined on large polymeric glutenin. The latter was measured as 50% 1-propanol insoluble (50PI) glutenin extractable with 50% 1-propanol in reductant dithiothreitol. The decreases in the amount of 50PI glutenin and the h...

Preparation of monoclonal antibodies against specific gliadin proteins and preliminary investigation of their ability to discriminate cereal cultivars

Monoclonal antibodies (MAbs) were prepared against γ-gliadin 45 and α-gliadin 74 from the common wheat cultivars Marquis and Marshall, respectively. Murine monoclonal antibodies were prepared and positive clones were detected using ELISA. MAbs prepared against gliadin 45 gave a low reaction in ELISA to extracts of einkorn, rye, barley and some common and durum wheats, and higher reaction to other common and durum wheats. Protein blotting of total gliadins separated by SDS-PAGE showed that MAbs against gliadin 45 bound to one discrete region corresponding to the location of gliadin 45. MAbs prepared against gliadin 74 gave a low reaction to rye, a medium reaction to barley, and a high reaction to all common and durum wheats and einkorn. Protein blotting showed that these MAbs bound to the region corresponding to α- and β-gliadins.