Measurement of Zeta Potential of Polysaccharides and Fabricating Polysaccharide-polysaccharide Nanotubes

Biopolymer nanotubes (BNTs) are two-open ended cylindrical structures which can be used for nanodevices, medicine, and biology. Especially, fabricating BNTs using proteins is suitable for biological and biomedical applications due to their safety and biocompatibility. This study has been focused on fabricating BNTs using polysaccharides which have been proved to be safe by the FDA and used in food applications. The zeta-potential, surface charge, of different polysaccharides was measured to find the region of stability and isoelectric point from pH 4 to 11 by DLS. Next, xanthan and chitosan have been selected for fabricating BNTs because of their stability and dispersibility compared to the other polysaccharides. Two polysaccharide solutions were adjusted to pH 4 where the charge difference was the largest; and BNTs were fabricated at different mass ratio using a template assisted layer-by-layer method. Then, SEM images were taken to visualize the nanotubes. As a result, some nanotubes were seen in the SEM images; however, they did not have the optimal well defined form yet. Also, there were too many clusters instead of individual clear nanotubes. The interaction and the size of the proteins might be too large, so the polysaccharides tended to form globular structures instead of nanotubes. To fabricate BNTs, xanthan will be hydrolyzed to reduce size, and the mass ratio would be also reduced to decrease the interaction between two polysaccharides

Glutaraldehyde Crosslinked Zein Solutions Make Better Biodegradable Films

The corn protein, zein, is a byproduct of the ethanol production industry. Recently, zein has been used in the production of films and food packaging due to its biodegradability, low production cost, and abundance of corn in the United States. To improve overall quality of zein films, the mechanical properties and surface properties should be enhanced. Therefore, in this study, our aim is to improve the properties of zein films with glutaraldehyde (GDA) as a crosslinker. Zein was solubilized and mixed with 70% ethanol and GDA, then sonicated. Solutions were poured onto different surface materials, including polydimethylsiloxane (PDMS), polystyrene (PS), and glass petri dishes to create films. Cast solutions were placed in the oven for different length of time (i.e. 0 hour, 1 day, 3 day, etc). Water contact angle and FTIR measurements were conducted to understand the crosslinking mechanism of zein films and surface properties of zein to understand how it will perform. Measurements from water contact angle and FTIR showed changes caused by heating, with 6% GDA films having less increase in hydrophobicity than films with 0% GDA and the changes in the ratio of -helices and -sheet structures of zein as the duration of heating was increased. Casting zein films on different surfaces affected the hydrophobicity of films that were not heated, but films that were heated for 3 days in the oven did not have any significant differences

The SAOS, MAOS and LAOS behavior of a concentrated suspension of tomato paste and its prediction using the Bird-Carreau (SAOS) and Giesekus models (MAOS-LAOS)

The SAOS and LAOS behavior of tomato paste were investigated in this study. SAOS rheology was well predicted by the semi-empirical Bird-Carreau constitutive model. The LAOS (Large amplitude oscillatory shear) behavior of tomato paste was also investigated in depth in this study and non-linear rheological properties were obtained by utilizing Ewoldt-McKinley theory. These parameters offer new insights into the rheology of tomato paste and help understand structural changes which occur at different deformations (strain) and time scales (frequency). We plotted the intracycle normalized stress vs. normalized strain in the linear and non-linear regions offered new intracycle insights and observations. Tomato paste showed an irreversible structural change in LAOS evidenced by strain softening (in the mid-oscillatory region) followed by strain hardening (in the large oscillatory region). The nonlinear flow behavior simulated by the single mode Giesekus model gave good results up to moderate strains and frequencies. These results help gain better insights at large deformations, which occur during processing and consumption

Non-linear rheological behavior of gluten-free flour doughs and correlations of LAOS parameters with gluten-free bread properties

WOS: 000399267000005Predicting loaf volume development of gluten free baked products to have similar properties to wheat products remains a challenge and there is no good marker for loaf volume. Large Amplitude Oscillatory Shear (LAOS) flow experiments and baking tests were conducted on rice, buckwheat, quinoa, and soy flour doughs to understand if there is any correlation between the non-linear rheological properties and loaf volume. The challenging water absorption capacities were determined by matching the eta* vs. frequency data of the gluten free flours with that of the soft wheat flour dough with moisture content at 500 BU. 110%, 90%, 85%, and 160% water levels were found as optimal for rice, buckwheat, quinoa, and soy flour, respectively. The comparison of elastic Lissajous-Bowditch curves showed that the stronger nonlinearities were seen at low frequencies and the wider the loop, the weaker the structure and the more structural breakdown with an order of soft wheat, soy, buckwheat, quinoa and rice flour doughs. Secondary loops have been observed in viscous Lissajous-Bowditch curves which are related to the strong non-linearities in elastic stress. The distributions of elastic and viscous LAOS parameters showed that soy dough has the closest rheological performance to wheat dough among other dough samples, which has the highest protein content. G(L)'. and G(M)' values at 10 rad/s and 200% strain showed the best correlation among all LAOS parameters with the loaf volume. The strain stiffening/softening property e(3)/e(1) complemented the mechanistic explanations which were offered using G(L)' and G(M)' values. (C) 2017 Elsevier Ltd. All rights reserved

NON-LINEAR RHEOLOGICAL PROPERTIES OF SOFT WHEAT FLOUR DOUGH AT DIFFERENT STAGES OF FARINOGRAPH MIXING

WOS: 000386873100001During mixing of wheat flour doughs, the distribution of the gluten network changes as a result of continuously applied large deformations. Especially gliadin, changes its distribution in the whole network during mixing. It is possible to fundamentally explain the role of molecular changes in more detail using large amplitude oscillatory measurements (LAOS) in the non-linear region. Therefore, the purpose of this study is to understand the effect of mixing on the non-linear fundamental rheological behavior of soft wheat flour dough using LAOS. Dough samples were obtained at 4 different phases of the Farinograph mixing and LAOS tests were done on each of them. LAOS tets give in depth intracycle understanding of rheology. All samples showed strain stiffening S and shear thinning T behavior at large strains previously not known in the cereal rheology community. Increasing mixing time (phase 1 to phase 4) and decreasing frequency resulted in retardation in the break of strain stiffening as strain increases. The strain stiffening behavior started to decrease for the dough samples at the 3rd and the 4th phases of mixing. LAOS data enabled us to describe the non-linear rheological changes occurring both in the viscous part largely attributed to the starch matrix and elastic part largely attributed to the gluten network components of the soft wheat flour dough under large deformations.USDA Hatch funds; William R. Scholle Foundation; Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)This research was partly funded by USDA Hatch funds, the William R. Scholle Foundation, a Fellowship to Gamze Yazar from The Scientific and Technological Research Council of Turkey (TUBITAK). The authors gratefully acknowledge all of these funding sources which made this research possible

LAOS behavior of the two main gluten fractions: Gliadin and glutenin

WOS: 000415782300028Crude gliadin and glutenin fractions were studied using Large Amplitude Oscillatory measurements. LAOS measurements were carried out at three different frequencies (20, 10, 1 rad/sec) between the strain values of 0.01-200%. The beginning of non-linearity for glutenin occurred at similar to 2.5%, while an initial region of strain hardening was observed for gliadin (2.5-10%) at 1 rad/sec frequency and up to 15% at the higher frequencies applied. Lissajous curves showed in the elastic analysis of both fractions glutenin was more elastically dominated since Lissajous curves were narrower, while for gliadin the ellipses were much broader suggesting more fluid-like behavior and each ellipse depended on the magnitude of frequency. Decreasing frequency increased the viscous behavior of both glutenin and gliadin in the non-linear region, but the change in gliadin was much more pronounced. Gliadin molecules only display intramolecular disulfide bonds creating a great deal of mobility whereas for glutenin molecules, which contain both intermolecular and intramolecular disulfide bonds, the strong network structure formed by this molecular arrangement results in very pronounced strain stiffening. (C) 2017 Elsevier Ltd. All rights reserved

Effect of mixing on LAOS properties of hard wheat flour dough

WOS: 000382349300022Large Amplitude Oscillatory Shear (LAOS) tests were conducted at strains ranging from 0.01% to 200% and different frequencies (20, 10, 1, and 0.1 rad/sec) on hard wheat flour dough samples obtained from the different phases of Farinograph mixing: 1) at the first peak, 2) 5 min after the first peak, 3) 12 min after the first peak, 4) at the 20th min. All samples showed strain stiffening and shear thinning behavior in large strains. The gluten network is the origin of strain stiffening behavior and the rearrangement of the suspended starch matrix is the origin of shear thinning behavior. LAOS enables us to independently deconvolute these two events offering new insights into the structural origins of rheological properties in the non-linear region. Dough samples started to show strain softening and shear thickening after giving a peak around 100% strain due to the onset of the breakdown of the gluten network. (C) 2016 Elsevier Ltd. All rights reserved.USDA Hatch funds; William R. Scholle Foundation; Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)This research was partly funded by USDA Hatch funds, the William R. Scholle Foundation, a Fellowship to Gamze Yazar from The Scientific and Technological Research Council of Turkey (TUBITAK). The authors gratefully acknowledge all of these funding sources which made this research possible

Complexation with Polysaccharides Enhances the Stability of Isolated Anthocyanins

Isolated anthocyanins have limited colonic bioavailability due to their instability as free forms. Thus, many methods have been fabricated to increase the stability of anthocyanins. Complexation, encapsulation, and co-pigmentation with other pigments, proteins, metal ions, and carbohydrates have been reported to improve the stability and bioavailability of anthocyanins. In this study, anthocyanins extracted from purple potatoes were complexed with four different polysaccharides and their mixture. The anthocyanin–polysaccharide complexes were characterized using a zeta potential analyzer, particle size analyzer, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Complexes were subjected to simulated digestion for assessing the stability of anthocyanins. Furthermore, complexes were subjected to different pH conditions and incubated at high temperatures to monitor color changes. A Caco-2 cell monolayer was used to evaluate the colonic concentrations of anthocyanins. In addition, the bioactivity of complexes was assessed using LPS-treated Caco-2 cell monolayer. Results show that pectin had the best complexation capacity with anthocyanins. The surface morphology of the anthocyanin–pectin complex (APC) was changed after complexation. APC was more resistant to the simulated upper gastrointestinal digestion, and high pH and temperature conditions for a longer duration. Furthermore, APC restored the lipopolysaccharide (LPS)-induced high cell permeability compared to isolated anthocyanins. In conclusion, complexation with pectin increased the stability and colonic bioavailability and the activity of anthocyanins