Microcalorimetry of the intestinal mucus: Hydrogen bonding and self-assembly of mucin

The effect of mucin hydrogen bonding on the structure of intestinal mucus has been studied with micro-differential scanning mirocalorimetry (μ-DSC), supported by spectroscopy. The experiments were performed in water–dimethyl sulfoxide (DMSO) solutions, using either water–DMSO mixtures of an appropriate DMSO content or water as blanks, as to isolate the effects of the solvent to hydrogen bonding. When using matched water–DMSO blanks, thermal events at low temperatures are linked to the negation of mucin–DMSO interactions, while events at higher temperatures are linked to the break-up of hydrogen bonds connecting the sugars of the individual macromolecules. When using a matched solvent as blank, alterations in Cp, such as increases at 10% and 15% DMSO, have been linked to the break-up and creation of quaternary structures. In the case of water as blank, a monotonic but not linear decrease in enthalpy, hence extent of hydrogen bonding, is observed. The above are complemented by UV spectroscopy: A blue shift of the conjugated aminoacids in the presence of DMSO suggests that the inherent stability of mucin is not only due to steric volume exclusions, but also due to extensive hydrogen bonding on behalf of the sugar moieties

Effect of barley β-glucan concentration on the microstructural and mechanical behaviour of acid-set sodium caseinate gels

The microstructural and mechanical properties of acid-set mixtures of sodium caseinate (2% w/w)/barley ß-glucans (2-6% w/w) were studied in an effort to evaluate the effect of these polysaccharides on the texture of fermented dairy products. The phase behavior of the blends was investigated using small deformation dynamic oscillation, differential scanning calorimetry, optical microscopy, and polymer blending-laws analysis. The work aimed to assess the topology of the phase separated mixture, the water holding capacity of its polymeric phases, and the thermal stability of the constituent networks. The mixed network properties were dominated by the protein component at low concentrations of ß-glucans (=3% w/w). In the concentrated regime, the system seems to have a bicontinuous topology governed by the mechanical strength and thermal stability of the ß-glucan network structure. Results could assist in optimising the use of sodium caseinate and ß-glucans as functional or as bioactive ingredients in acid-set dairy products

Rheological characterization of okra pectins

Polysaccharides from okra pods (Abelmoschus esculentus) were extracted using a sequential extraction protocol and compared with a simple extraction at pH 6. Rheological properties of three okra extracts were then investigated by means of molecular weight determination, dilute solution rheology, steady shear and oscillatory rheological measurements. The extraction protocols resulted in extracts of relatively high purity and multimodal molecular weight distribution. Furthermore, molecular parameters of the isolated biopolymers such as intrinsic viscosity, Huggins constant, critical concentration and coil overlap parameter were calculated from dilute solution viscometry. Investigation of the generalized flow behaviour using a modified Cross equation and Cox–Merz plots showed evidence that as concentration increases specific interactions start taking place among the polymeric chains that modify the rheological behaviour of the extracts. The change in the rheological behaviour could not only be explained by differences in the molecular weight of the samples but also should be attributed to the fine structure of the chains that are obtained under the different extraction protocols. Present investigation shows that further optimization of such protocols may result in polysaccharide fractions with specific rheological propertie

Okra extracts as emulsifiers for acidic emulsions

Extracts rich in pectins were isolated by aqueous extraction at pH 4.0 (OE4) and 6.0 (OE6) from okra (Abelmoschus esculentus) pods. They were examined in terms of their composition and emulsion stabilizing capacity in model acidic emulsions (hexadecane-in-water at pH 3.0). Extracted polysaccharides were assessed using size exclusion chromatography (SEC) and FTIR spectroscopy. The properties and stability of the resulting emulsions were examined by means of droplet size distribution and ζ-potential measurements, viscometry, fluorescence microscopy and protein interface concentration. As emulsifiers, both extracts produce emulsions of initially monomodal size distribution and of similar average droplet size, while ζ-potential was negative for both. The emulsions prepared using OE6 are relatively stable in terms of droplet size distribution and average droplet size after 30 days of storage, while emulsions prepared with OE4 increase in droplet size, in part attributable to Ostwald ripening. Determination of the protein interface coverage Γ suggests that the increased stability of the OE6 emulsions should be attributed to the higher protein load of the interfaces prepared using this extract, resulting to increased rigidity of the interface. Viscosity of emulsions containing OE6 was two times greater than OE4 while aging increases the viscosity of both emulsions. The present work suggests that okra extracts can be strong candidates for emulsification in acidic environments

The new V12 ultra small angle neutron scattering and tomography instrument at the Hahn Meitner Institut

The new V12 instrument at the Hahn Meitner Institute in Berlin is a multiple setup combining several techniques to investigate the internal structure of bulk samples. It consists of two double crystal diffractometers DCDs and an attenuation tomography device operating with monochromatic neutrons. The three instrument parts can be used independently at the same time. The DCDs are mainly used in the ultra small angle neutron scattering USANS regime, where they overlap the accessible range of small angle neutron scattering instruments, while tomographic methods collect real space information on a macroscopic scale. Together they enable structural investigations over six orders of magnitude 50 nm to 5 cm . Scattering and tomographic methods can even be combined by means of diffraction and scattering enhanced imaging. The sample environment can be varied over a large range of temperatures and pressures for USANS measurements and a polarized USANS option is availabl

Emulsifiers from mealworm

Aqueous extracts obtained from the larvae of Tenebrio molitor (“mealworms”) have been used as sole emulsifiers for oil–in–water emulsions. For an oil volume fraction of 0.2, they produced coalescence-stable droplets of a few μm at a minimal concentration of 1 g dL−1 and flocculated systems at higher concentrations. Size exclusion chromatography showed that the extracts consist of a polysaccharidic and a proteinic macromolecular population, and of smaller molecules; SDS-displacement experiments showed that proteins are found to be the main component that adsorbs and stabilizes the oil–in–water interfaces. This is verified by interfacial measurement experiments. Removal of the smaller molecules produced efficient emulsifiers without flocculation, suggesting that the latter is due to electrostatic phenomena, rather than depletion. The zeta potential of this purified extract was very sensitive to pH changes between 6 and 7, allowing for specialized/pH-sensitive uses. The results suggest that mealworm extracts show potential as emulsifiers without the need of further purification (e.g. protein isolation), and can lead to high added-value products, while avoiding the consumers’ subconscious connection of these ingredients to their original sources. © 2023 Elsevier Lt