Explore the vast range of titles available.

Quality protein maize (QPM) represents an alternative protein source for food. This work aims to characterize fractions, molecular weights, and thermal stability of the proteins present in QPM protein concentrates obtained by isoelectric precipitation. Flours from two treatments, non-nixtamalized and nixtamalized, as well as three types of maize varieties: Sac Beh (QPM white), Chichén Itzá (QPM yellow), and Blanco Uxmal (control), were obtained. The experiment was conducted using a bifactorial 2x3 design. Four isoelectric precipitation pHs were evaluated, having the highest yield and maximum protein precipitation at pH 2,5 at 4 °C. The relative protein fractions in the maize varieties in both treatments showed more elevated amounts of prolamins (PR) and glutelins (GT) compared to the control. All QPM showed higher GT and lower PR. The denaturing electrophoretic profile (SDS-PAGE) showed molecular weights for the concentrates ranging from 17,6 to 225 kDa (non-nixtamalized), from 12,9 to 132,2 kDa (nixtamalized), and from the fractions with weights from 10,2 to 220,7 kDa. The thermograms showed a change in thermal stability in the concentrates from non-nixtamalized flour; there were no thermal transitions in the nixtamalized ones due to the denaturation of the proteins when obtaining the samples during nixtamalization of all the varieties studied.

This study investigated the effect of high temperature and drought (during grain-filling) on the quality and components yield of five winter wheat varieties. Drought and drought + heat were found to have a much greater influence on the yield and quality than heat stress alone. Averaged over the varieties, the yield losses were 57% after drought, 76% after drought + heat, and only 31% after heat stresses. The reductions in the unextractable polymeric protein fraction and glutenin-to-gliadin ratio indicated a poorer grain yield quality, despite the higher protein content. Quality deterioration was observed after drought or drought + heat, while high temperatures alone resulted in no change or in a better ratio of protein components. A significant negative correlation was observed between starch granule size and relative protein content after drought.

The prolamin box (P-box) is a highly conserved 7-bp sequence element (5'-TGTAAAG-3') found in the promoters of many cereal seed storage protein genes. Nuclear factors from maize endosperm specifically interact with the P-box present in maize prolamin genes (zeins). The presence of the P-box in all zein gene promoters suggests that interactions between endosperm DNA binding proteins and the P-box may play an important role in the coordinate activation of zein gene expression during endosperm development. We have cloned an endosperm-specific maize cDNA, named prolamin-box binding factor (PBF), that encodes a member of the recently described Dof class of plant Cys2-Cys2 zinc-finger DNA binding proteins. When tested in gel shift assays, PBF exhibits the same sequence-specific binding to the P-box as factors present in maize endosperm nuclei. Additionally, PBF interacts in vitro with the basic leucine zipper protein Opaque2, a known transcriptional activator of zein gene expression whose target site lies 20 bp downstream of the P-box in the 22-kDa zein gene promoter. The isolation of the PBF gene provides an essential tool to further investigate the functional role of the highly conserved P-box in regulating cereal storage protein gene expression

The microstructural characteristics were evaluated of two types of Italian Farro (Triticum turgidum ssp. dicoccum) with spring and autumn growth habits, the former with a vitreous tendency and the latter with a floury tendency. Common wheat flours and grains (Triticum aestivum) were used as controls. Protein fractions such as glutenin and gliadin were extracted from Triticum turgidum ssp. dicoccum flours and studied by SDS-PAGE in order to make a comparison between the electrophoretic analyses and microstructural studies which were conducted on the same samples using Scanning Electron Microscopy (SEM and Cryo-SEM). The results obtained by SDS-PAGE showed that the gliadin patterns of both emmer samples were similar, while the common wheat gliadins showed a band at 90 kDa that was not present in the gliadin fraction of emmer. When the glutenin patterns were analysed, the autumn emmer did not show the low molecular weight protein bands (16-23 kDa) whilst spring emmer wheat appeared more similar to common wheat. Regarding the microstructural characteristics of the kernels, spring (vitreous tendency) emmer showed starch granules covered by protein to a higher extent than autumn emmer. These differences were also observed in flours. The gluten of spring emmer wheat was observed as a homogeneous structure showing similarities with common wheat gluten, while autumnal emmer gluten appeared more heterogeneous and lacking in structure.

Las prolaminas (zeínas) representan la principal proteína de reserva en el grano de maíz y poco se conoce sobre su participación en la textura de la tortilla. Para determinar su efecto, se evaluaron 6 híbridos de tipo normal y 6 de calidad proteínica (QPM, por sus siglas en inglés). Las variables químicas incluyeron prolaminas, amilosa y almidón. Se determinó la viscosidad de las harinas y la textura de las tortillas en términos de la fuerza de ruptura a tensión y elongación. El contenido de prolaminas en los maíces normales fue 64% más elevado en comparación con los QPMs. No se observó relación entre el contenido de prolaminas y las propiedades de viscosidad de las harinas, como tampoco se halló relación de esta fracción proteínica con la dureza de la tortilla, pero si con la elongación, que mostró una correlación negativa con la cantidad de prolaminas. Las tortillas con mejores características de textura fueron H-161 en maíces normales y H-143C en maíces QPM, ambos maíces presentaron los granos más pequeños dentro de su grupo. Los resultados muestran que un elevado contenido de prolaminas en el grano de maíz podría estar limitando la textura de la tortilla en términos de su elongaciónEffect of the prolamins in maize (Zea mays L.) grain on tortilla texture. The prolamins (zeins) are the main storage proteins in the maize grain. There are limited investigations related to their participation on tortilla texture. For determining their effect, normal (6) and Quality Protein Maize (QPM) (6) genotypes were used. The chemical variables comprised prolamins, amylose and starch in whole grain and endosperm. Viscosity of the raw endosperm flour was determined as well as the tortilla texture, expressed in terms of tension force and elongation. Prolamin content in the normal maizes was 64 % higher than that in the QPMs. It was not observed any relationship between prolamin content and flour viscosity. The prolamin content was not related with tortilla hardness, measured as the tension force to rupture the tortilla, but a negative correlation was observed with tortilla elongation. The tortillas with the best texture characteristics were from H-161nomal maize and H-143 QPM maize, both genotypes showed the smallest grain in its respective gruop. According to the results obtained in the present work, a high prolamin content in maize grain could be affecting tortilla elongation

Zeins are seed storage proteins that form accretions called protein bodies in the rough endoplasmic reticulum of maize endosperm cells. Four types of zeins, alpha, beta, gamma, and delta, aggregate in a distinctive spatial pattern within the protein body. We created transgenic tobacco plants expressing alpha-zein, gamma-zein, or both to examine the interactions between these proteins leading to the formation of protein bodies in the endosperm. Whereas gamma-zein accumulated in seeds of these plants, stable accumulation of alpha-zein required simultaneous synthesis of gamma-zein. The zein proteins formed accretions in the endoplasmic reticulum similar to those in maize endosperm. Protein bodies were also found in protein storage vacuoles. The accumulation of both types of zeins peaked early in development and declined during maturation. Even in the presence of gamma-zein, there was a turnover of alpha-zein, suggesting that the interaction between the two proteins might be transitory. We suggest that gamma-zein plays an important role in protein body formation and demonstrate the utility of tobacco for studying interactions between different zeins

Thioredoxin, a ubiquitous 12-kDa regulatory disulfide protein, was found to reduce disulfide bonds of allergens (convert S--S to 2 SH) and thereby mitigate the allergenicity of commercial wheat preparations. Allergenic strength was determined by skin tests with a canine model for food allergy. Statistically significant mitigation was observed with 15 of 16 wheat-sensitive animals. The allergenicity or the protein fractions extracted from wheat flour with the indicated solvent was also assessed: the gliadins (ethanol) were the strongest allergens, followed by glutenins (acetic acid), albumins (water), and globulins (salt water). Of the gliadins, the alpha and beta fractions were most potent, followed by the gamma and omega types. Thioredoxin mitigated the allergenicity associated with the major protein fractions--i.e., the gliadins (including the alpha, beta, and gamma types) and the glutenins--but gave less consistent results with the minor fractions, the albumins and globulins. In all cases, mitigation was specific to thioredoxin that had been reduced either enzymically by NADPH and NADP-thioredoxin reductase or chemically by dithiothreitol; reduced glutathione was without significant effect. As in previous studies, thioredoxin was particularly effective in the reduction of intramolecular (intrachain) disulfide bonds. The present results demonstrate that the reduction of these disulfide bonds is accompanied by a statistically significant decrease in allergenicity of the active proteins. This decrease occurs alongside the changes identified previously--i.e., increased susceptibility to proteolysis and heat, and altered biochemical activity. The findings open the door to the testing of the thioredoxin system in the production of hypoallergenic, more-digestible foods

The maize floury2 mutation results in the formation of a soft, starchy endosperm with a reduced amount of prolamin (zein) proteins and twice the lysine content of the wild type. The mutation is semidominant and is associated with small, irregularly shaped protein bodies, elevated levels of a 70-kDa chaperone in the endoplasmic reticulum, and a novel 24-kDa polypeptide in the zein fraction. The 24-kDa polypeptide is a precursor of a 22-kDa alpha-zein protein that is not properly processed. The defect is due to an alanine-to-valine substitution at the C-terminal position of the signal peptide, which causes the protein to be anchored to the endoplasmic reticulum. We postulated that the phenotype associated with the floury2 mutation is caused by the accumulation of the 24-kDa alpha-zein protein. To test this hypothesis, we created transgenic maize plants that produce the mutant protein. We found that endosperm in seeds of these plants manifests the floury2 phenotype, thereby confirming that the mutant alpha-zein is the molecular basis of this mutation

A method of the evidence for the presence of wheat, rye, and barley in gluten free foods, based on the polymerase chain reaction (PCR), was validated. DNA was isolated from foods by chaotropic solid phase extraction. The PCR method applied was focused on the intron of the chloroplast gene trnL and utilised primers WBR11 and WBR13. Electrophoresed wheat and rye DNAs were characterised by a 201 bp fragment, barley DNA by a 196 bp fragment. The validated PCR method was applied to the selection of 18 gluten free foods, previously found by ELISA method to contain 1 mg or more of gliadin per 100 g food. The presence of wheat was confirmed by PCR method in all foods analysed. The comparison with the results obtained by ELISA method reliably verified the detection limit of PCR method, i.e., 0.02% wheat.