Trung K. Cao

Changes in secondary protein structures during mixing development of high absorption (90%) flour and water mixtures

ABSTRACT Wheat flour and water mixtures at 90% absorption (dry flour basis) prepared at various mixing times were examined using Fourier transform infrared (FT-IR) reflectance spectroscopy. Spectra were obtained using a horizontal attenuated total reflection (ATR) trough plate. The apparent amount of protein and starch on the surface of the dough varied with mixing time but this was likely due to the polyphasic nature of the substrate and the changing particle distributions as the batter matrix was developed. Deconvolution of the Amide I band revealed contributions from alpha helical, β-turn, β-strand, β-sheet, and random conformations. The ratio of β-sheet to nonsheet conformations reached its greatest value about the same time that the mixture was most effectively separated by a laboratory-scale, cold-ethanol-based method but before the peak consistency measured by a microfarinograph.

Substitution of Concentrated Ethanol for Water in the Laboratory Washing Fractionation of Protein and Starch from Hydrated Wheat Flour

ABSTRACT An unprecedented, ethanol-based, washing process was used at a laboratory scale to produce both concentrated protein and starch fractions from hydrated wheat flour. In this multistep process, flour was first hydrated and mixed to a batter and then chilled and rested. The cold batter was then mixed and washed in chilled and concentrated ethanol using a modified device that normally applies the water-based Martin process. Control of the separation was affected by each of these steps. For instance, the hydration of the flour, the time of mixing, the temperature of the wash, the ethanol concentration, and the time of washing were influential. The method produced a gluten concentrate similar in yield and protein content to that reported for a pilot-scale Martin process but without the need for added salt. Notably, ethanol washing resulted in nonsticky, partially disintegrated curds that dried easily, whereas water washing resulted in a sticky, glutinous, cohesive mass that dried slowly. The process ha...

Wheat Gluten Swelling and Partial Solubility with Potential Impact on Starch-from-Gluten Separation by Ethanol Washing

ABSTRACT Swelling of wheat gluten may be a contributing factor in washing or displacement separation of gluten and starch using cold ethanol. To test this hypothesis, dissolution and swelling (settled volume or mass absorption) of a commercial gluten are reported here for the first time as a function of both temperature and ethanol solution concentration. In this test system, instant and substantial volumetric swelling was observed over most of the range of ethanol concentrations but not at 100%, v/v, ethanol. Settled volume reached a maximum of 50–70%, v/v, ethanol, and this was up to 3.5× the volume in absolute ethanol at 22°C and 2× the volume at −15°C. This maximum closely corresponds to the maximum dissolution of whole gluten and prior literature reports of full dissolution of gliadin. The reduction of settled volume at low temperature reflects the possible role of undissolved, gliadin-class proteins in reinforcing the gluten structure and limiting the ultimate swelling. The data suggest gluten-swell...

Effect of Morphology of Mechanically Developed Wheat Flour and Water on Starch from Gluten Separation Using Cold Ethanol Displacement

ABSTRACT The mechanical development of wheat flour and water creates micro and macro structures in dough or batter that critically influence the ability to separate starch from protein by fluid displacement. This study sought to identify specific structural and rheological features and to relate these to separation as indexed by the separation factor. Structural features, especially protein and starch distributions, were examined using visible light microscopy applied to dough samples that had been exposed to a protein dye. Flour and water samples were developed in a Brabender microfarinograph at conditions (water content and time of development) generally suitable for use of the USDA Western Regional Research Center, cold-ethanol fluid-displacement method. No truly homogenous structures were observed. However, distinct segregation of protein and starch were apparent at all conditions. Structural features correlated qualitatively with the success of separation indexed by the overall separation factor (αp/...

Farinograph Responses for Wheat Flour Dough Fortified with Wheat Gluten Produced by Cold-Ethanol or Water Displacement of Starch.

ABSTRACT The objective of this research was to identify and define mixing characteristics of gluten-fortified flours attributable to differences in the method for producing the gluten. In these studies, a wheat gluten concentrate (W-gluten) was produced using a conventional process model. This model applied physical water displacement of starch (dispersion and screening steps), freeze-drying, and milling. W-gluten was the reference or “vital” gluten in this report. An experimental W-concentrate was produced using a new process model. The new model applied coldethanol (CE) displacement of starch (dispersion and screening steps), freeze-drying, and milling. Freeze-drying was used to eliminate thermal denaturation and thereby focus on functional changes due only to the separation method. The dry gluten concentrates were blended with a weak, low-protein (9.2%), soft wheat flour and developed with water in a microfarinograph. We found that both water and cold-ethanol processed gluten successfully increased the...

Wheat proteins extracted from flour and batter with aqueous ethanol at subambient temperatures

ABSTRACT Contact of wheat flour with aqueous ethanol may enrich protein by starch displacement or deplete protein by extraction depending on 1) extraction conditions and 2) the form of the substrate. Extraction at subambient temperatures has not been described for specific gliadins for either dry flour with the protein in native configurations or for wet, developed batter or dough. This limits the ability to interpret technologies such as the cold-ethanol method. Here, we describe specific albumin and gliadin composition of flour extracts by capillary zone electrophoresis CZE in 0–100% (v/v) ethanol from –12 to 22°C. Extraction was reduced for albumin and gliadin protein as the temperature was reduced and the concentration range for extraction narrowed. Extraction dropped precipitously between 0 and –7°C for both albumins and gliadins. Electrophoretically defined gliadins extracted in constant proportion at 22°C and 30–80%(v/v) ethanol, but at lower temperature, the α-gliadins were enriched and β-gliadins...

Proteins Extracted by Water or Aqueous Ethanol During Refining of Developed Wheat Dough to Vital Wheat Gluten and Crude Starch as Determined by Capillary-Zone Electrophoresis (CZE)

ABSTRACT Fluids applied to large-sale, technical separation of wheat starch and protein also extract soluble proteins. The degree and rate of extraction and the specific components extracted depend on the flour, the flour hydration and development, the starch-displacing fluid composition, the temperature, and the mechanical processing method. This study sought to identify major extracted protein groups using high-performance capillary zone electrophoresis (CZE) applied directly to fluids obtained during laboratory-scale technical separations. A dough-ball or compression separation method was applied using a Glutomatic system and a batter or dispersion method was applied using a a McDuffie mixer and Pharmasep vibratory separator. Process fluids were water at 22°C to model commercial practice and 70 vol% ethanol in water at -13°C to model the cold ethanol process being developed here. Data were referenced to use of 70 vol% ethanol in water at 22°C in the Glutomatic compression method. The dough processed by...

Mixograph Responses of Gluten and Gluten-Fortified Flour for Gluten Produced by Cold-Ethanol or Water Displacement of Starch from Wheat Flour

ABSTRACT The total protein of gluten obtained by the cold-ethanol displacement of starch from developed wheat flour dough matches that made by water displacement, but functional properties revealed by mixing are altered. This report characterizes mixing properties in a 10-g mixograph for cold-ethanol-processed wheat gluten concentrates (CE-gluten) and those for the water-process concentrates (W-gluten). Gluten concentrates were produced at a laboratory scale using batter-like technology: development with water as a batter, dispersion with the displacement fluid, and screening. The displacing fluid was water for W-gluten and cold ethanol (≥70% vol, -12°C) for CE-gluten. Both gluten types were freeze-dried at -10°C and then milled. Mixograms were obtained for 1) straight gluten concentrates hydrated to absorptions of 123–234%, or 2) gluten blended with a low protein (9.2% protein) soft wheat flour to obtain up to 16.2% total protein. The mixograms for gluten or gluten-fortified flour were qualitatively and ...

Physical Characteristics of Genetically Altered Wheat Related to Technological Protein Separation

ABSTRACT Wheat protein is a technologically challenging substrate for food and nonfood applications because of its compositional diversity and susceptibility to denaturation. Genetic modification could be used to create cultivars capable of producing more uniform or focused and novel protein compositions targeted to nonfood uses. These lines could serve as expression systems for specific high-molecular-weight (HMW) protein polymers and would be new crops leading to more diverse agricultural opportunities. However, fundamental changes to the molecular architecture in such wheat seeds could also result in separation and processing issues, such that conventional methods of protein enrichment may need modification or even reinvention. Enriched gluten protein fractions were prepared from Bobwhite lines modified to overproduce HMW glutenin subunits Dx5 and/or Dy10. These lines serve as experimental models to test various approaches that may be taken for protein polymer enrichment. However, conventional wheat gl...

Mechanically Robust and Transparent N-Halamine Grafted PVA-co-PE Films with Renewable Antimicrobial Activity

Antimicrobial polymeric films that are both mechanically robust and function renewable would have broad technological implications for areas ranging from medical safety and bioengineering to foods industry; however, creating such materials has proven extremely challenging. Here, a novel strategy is reported to create high-strength N-halamine incorporated poly(vinyl alcohol-co-ethylene) films (HAF films) with renewable antimicrobial activity by combining melt radical graft polymerization and reactive extrusion technique. The approach allows here the intrinsically rechargeable N-halamine moieties to be covalently incorporated into polymeric films with high biocidal activity and durability. The resulting HAF films exhibit integrated properties of robust mechanical strength, high transparency, rechargeable chlorination capability (>300 ppm), and long-term durability, which can effectively offer 3-5 logs CFU reduction against typical pathogenic bacterium Escherichia coli within a short contact time of 1 h, even at high organism conditions. The successful synthesis of HAF films also provides a versatile platform for exploring the applications of antimicrobial N-halamine moieties in a self-supporting, structurally adaptive, and function renewable form.