Ramune Kuktaite

Wheat gluten polymer structures : The impact of genotype environment and processing on their functionality in various applications

ABSTRACT For a number of applications, gluten protein polymer structures are of the highest importance in determining end-use properties. The present article focuses on gluten protein structures in the wheat grain, genotype- and environment-related changes, protein structures in various applications, and their impact on quality. Protein structures in mature wheat grain or flour are strongly related to end-use properties, although influenced by genetic and environment interactions. Nitrogen availability during wheat development and genetically determined plant development rhythm are the most important parameters determining the gluten protein polymer structure, although temperature during plant development interacts with the impact of the mentioned parameters. Glutenin subunits are the main proteins incorporated in the gluten protein polymer in extracted wheat flour. During dough mixing, gliadins are also incorporated through disulfide-sulfhydryl exchange reactions. Gluten protein polymer size and complexi...

Molecular structure of citric acid cross-linked starch films

The effect of citric acid (CA) on starch films has been examined. A new method to detect cross-linking of starch by CA in solution-cast films by molecular weight measurements is described. Furthermore, we managed to distinguished between free, mono- and di-esterified CA and quantify di-ester content within starch films by using a modification in the method of complexometric titration with copper(II)-sulfate. Cross-linking of starch by CA occurred at low temperature, 70°C, which we assumed is so far the lowest temperature reported where cross-linking reaction occurred. This is essential for starch coating applications within paper industry since no high temperatures for curing will be required. However, curing at 150°C and high CA concentrations, 30 pph, increased cross-linking reaction. Furthermore, the physical properties like water solubility, gel content and glass transition temperature, were highly reflected by changes in the molecular structure i.e. cross-linking and hydrolysis, as well as CA content and curing temperature.

Mineral Composition of Organically Grown Wheat Genotypes: Contribution to Daily Minerals Intake

In this study, 321 winter and spring wheat genotypes were analysed for twelve nutritionally important minerals (B, Cu, Fe, Se, Mg, Zn, Ca, Mn, Mo, P, S and K). Some of the genotypes used were from multiple locations and years, resulting in a total number of 493 samples. Investigated genotypes were divided into six genotype groups i.e., selections, old landraces, primitive wheat, spelt, old cultivars and cultivars. For some of the investigated minerals higher concentrations were observed in selections, primitive wheat, and old cultivars as compared to more modern wheat material, e.g., cultivars and spelt wheat. Location was found to have a significant effect on mineral concentration for all genotype groups, although for primitive wheat, genotype had a higher impact than location. Spring wheat was observed to have significantly higher values for B, Cu, Fe, Zn, Ca, S and K as compared to winter wheat. Higher levels of several minerals were observed in the present study, as compared to previous studies carried out in inorganic systems, indicating that organic conditions with suitable genotypes may enhance mineral concentration in wheat grain. This study also showed that a very high mineral concentration, close to daily requirements, can be produced by growing specific primitive wheat genotypes in an organic farming system. Thus, by selecting genotypes for further breeding, nutritional value of the wheat flour for human consumption can be improved.

Structure and morphology of wheat gluten films: from polymeric protein aggregates toward superstructure arrangements.

Evaluation of structure and morphology of extruded wheat gluten (WG) films showed WG protein assemblies elucidated on a range of length scales from nano (4.4 Å and 9 to 10 Å, up to 70 Å) to micro (10 μm). The presence of NaOH in WG films induced a tetragonal structure with unit cell parameters, a = 51.85 Å and c = 40.65 Å, whereas NH(4)OH resulted in a bidimensional hexagonal close-packed (HCP) structure with a lattice parameter of 70 Å. In the WG films with NH(4)OH, a highly polymerized protein pattern with intimately mixed glutenins and gliadins bounded through SH/SS interchange reactions was found. A large content of β-sheet structures was also found in these films, and the film structure was oriented in the extrusion direction. In conclusion, this study highlights complexities of the supramolecular structures and conformations of wheat gluten polymeric proteins in biofilms not previously reported for biobased materials.

Mechanical Properties and Network Structure of Wheat Gluten Foams

This Article reports the influence of the protein network structure on the mechanical properties of foams produced from commercial wheat gluten using freeze-drying. Foams were produced from alkaline aqueous solutions at various gluten concentrations with or without glycerol, modified with bacterial cellulose nanosized fibers, or both. The results showed that 20 wt % glycerol was sufficient for plasticization, yielding foams with low modulus and high strain recovery. It was found that when fibers were mixed into the foams, a small but insignificant increase in elastic modulus was achieved, and the foam structure became more homogeneous. SEM indicated that the compatibility between the fibers and the matrix was good, with fibers acting as bridges in the cell walls. IR spectroscopy and SE-HPLC revealed a relatively low degree of aggregation, which was highest in the presence of glycerol. Confocal laser scanning microscopy revealed distinct differences in HMW-glutenin subunits and gliadin distributions for all of the different samples.

Contribution of organically grown crops to human health.

An increasing interest in organic agriculture for food production is seen throughout the world and one key reason for this interest is the assumption that organic food consumption is beneficial to public health. The present paper focuses on the background of organic agriculture, important public health related compounds from crop food and variations in the amount of health related compounds in crops. In addition, influence of organic farming on health related compounds, on pesticide residues and heavy metals in crops, and relations between organic food and health biomarkers as well as in vitro studies are also the focus of the present paper. Nutritionally beneficial compounds of highest relevance for public health were micronutrients, especially Fe and Zn, and bioactive compounds such as carotenoids (including pro-vitamin A compounds), tocopherols (including vitamin E) and phenolic compounds. Extremely large variations in the contents of these compounds were seen, depending on genotype, climate, environment, farming conditions, harvest time, and part of the crop. Highest amounts seen were related to the choice of genotype and were also increased by genetic modification of the crop. Organic cultivation did not influence the content of most of the nutritional beneficial compounds, except the phenolic compounds that were increased with the amounts of pathogens. However, higher amounts of pesticide residues and in many cases also of heavy metals were seen in the conventionally produced crops compared to the organic ones. Animal studies as well as in vitro studies showed a clear indication of a beneficial effect of organic food/extracts as compared to conventional ones. Thus, consumption of organic food seems to be positive from a public health point of view, although the reasons are unclear, and synergistic effects between various constituents within the food are likely.

Individual and interactive effects of cultivar maturation time, nitrogen regime and temperature level on accumulation of wheat grain proteins.

BACKGROUND Background and reasons for differences in wheat grain protein accumulation and polymerization are not fully understood. This study investigated individual and interactive effects of genetic and environmental factors on wheat grain protein accumulation and amount and size distribution of polymeric proteins (ASPP). RESULTS Individual factors, e.g. maturation time of a cultivar, nitrogen regime and temperature level, influenced grain protein accumulation and ASPP, although interaction of these factors had a greater influence. Early maturation time and long grain maturation period (GMP) in a cultivar resulted in high amounts of sodium dodecyl sulphate (SDS)-extractable proteins (TOTE) and low percentage of SDS-unextractable polymeric proteins in total polymeric proteins (%UPP). Cultivars with late maturation time and short GMP resulted in low TOTE and high %UPP. Late versus early nitrogen application regime resulted in low %UPP versus low TOTE and high %UPP, respectively. High versus low temperature resulted in high %UPP and low %UPP, respectively. Differences in ASPP at maturity started as changes in protein accumulation from 12 days after anthesis. CONCLUSION Length of GMP, especially in relation to length until maturity, governs gluten strength (%UPP) and grain protein concentration (TOTE). Length of GMP is determined by cultivar, temperature during GMP and late nitrogen availability.

Structural architecture and solubility of native and modified gliadin and glutenin proteins: non-crystalline molecular and atomic organization

Wheat gluten (WG) and its components, gliadin and glutenin proteins, form the largest polymers in nature, which complicates the structural architecture of these proteins. Wheat gluten, gliadin and glutenin proteins in unmodified form showed few secondary structural features. Structural modification of these proteins using heat, pressure and the chemical chaperone glycerol resulted in a shift to organized structure. In modified gliadin, nano-structural molecular arrangements in the form of hexagonal closed packed (HCP) assemblies with lattice parameter of (58 A) were obvious together with development of intermolecular disulphide bonds. Modification of glutenin resulted in highly polymerized structure with proteins linked not only by disulphide bonds, but also with other covalent and irreversible bonds, as well as the highest proportion of β-sheets. From a combination of experimental evidence and protein algorithms, we have proposed tertiary structure models of unmodified and modified gliadin and glutenin proteins. An increased understanding of gliadin and glutenin proteins structure and behavior are of utmost importance to understand the applicability of these proteins for various applications including plastic materials, foams, adhesives, films and coatings.

Protein network structure and properties of wheat gluten extrudates using a novel solvent-free approach with urea as a combined denaturant and plasticiser

This is, to our knowledge, the first success on solvent-free extrusion of wheat gluten (WG) into high quality films without using NaOH/salicylic acid. It was possible by using urea (concentrations: 10, 15 and 20 wt%) in the single screw-extruder process. Tensile testing, oxygen permeability, water vapor transmission rate, infrared spectroscopy (IR), confocal laser scanning microscopy (CLSM) and protein solubility were used to assess the properties of the extrudates. As the urea concentration increased, the strength and stiffness decreased while the extensibility increased. The oxygen permeability was low and increased, as did the water vapor transmission rate, with increasing urea concentration. The protein solubility of urea-containing films was found to be significantly lower than that of the native gluten and glycerol-plasticized WG extrudate. CLSM, together with the protein solubility, indicated that the urea films were aggregated/polymerized and IR spectroscopy revealed that these films contained a sizeable amount of β-sheets with a high degree of hydrogen bonds associated with protein aggregation. The aggregation did not change with increasing urea concentration, which suggests that the changes in the mechanical and permeability properties were due to urea-induced plasticisation.

Effect of Mixing Time on Gluten Recovered by Ultracentrifugation Studied by Microscopy and Rheological Measurements

ABSTRACT The effect of mixing time on gluten formation was studied for four commercial flour mixtures. The gluten phase was separated from dough using a nondestructive ultracentrifugation method. Small deformation dynamic rheological measurements and light and scanning electron microscopy were used. The recovered gluten was relatively pure with a small amount of starch granules embedded. The protein matrix observed by microscopy became smoother with prolonged mixing. No effect of overmixing was observed on the storage modulus (G′) of gluten for any of the flours. The amount of water in gluten increased from optimum to over-mixing for most of the flours. Increased water content during prolonged mixing was not related to an effect on G′. The Standard flour resulted in the highest water content of gluten, which increased considerably with mixing time. The Strong flour had the lowest G′ of dough, a high G′ of gluten, and no increase in gluten water content from optimum to over-mixing. The Durum flour did not ...