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International audience; The present study was undertaken to establish a distinct relationship between blue crab chitosan (Cs) acetylation degree (AD) and molecular weight (Mw) and its structural features, thermal properties and bioactivity. Therefore, chitosans with different AD were prepared and Cellulase was used to produce Cs derivatives with decreasing Mw. Results clearly display a decrease of the ordered structure of Cs, with the increase of AD and the decrease of Mw. Thermal stability/degradation screening disclose a greater thermal resistance for Cs with lower AD and higher Mw. The anti-adhesive potential of Cs was, additionally, studied, as function of AD and Mw. The effectiveness of Cs in preventing biofilm adhesion was strongly influenced by its AD and Mw, with the lowest inhibition values for higher AD and lower Mw. Interestingly, the effectiveness of Cs in disrupting pre-formed biofilms increased with decreasing Mw. Moreover, Cs derivatives were found to be advantageously efficient in prolonging human blood clotting times, based on data of activated partial thromboplastin time, Quick time and thrombin time assays, typically for the intrinsic coagulation pathway. Accordingly, depending on the predicted application of Cs, either in food, biomedical and pharmaceutical industries, AD and Mw are critical traits to be inevitably reflected on.

Anchote (Coccinia abyssinica) starch films were prepared by a solution casting method with glycerol, 1-ethyl-3-methylimidazolium acetate, sorbitol or triethylene glycol as plasticizers. The effect of these plasticizers and their concentration on film microstructure, thermal, and mechanical properties was investigated. Scanning electron microscopy revealed that regardless of plasticizer type, films possessing higher plasticizer content had more homogeneous morphologies than those with lower plasticizer content. The FTIR spectra of films plasticized with 1-ethyl-3-methylimidazolium acetate had higher intensity peaks at 3150, 1400 and 1000 cm−1 when compared to other film peaks. These data show that 1-ethyl-3-methylimidazolium acetate plasticized films have decreased molecular order which results in less hydrogen bonding. For this reason, films developed from 1-ethyl-3-methylimidazolium acetate were more flexible than the others. The effect of plasticizers on the thermal properties of the anchote starch films was investigated using thermogravimetric analysis (TGA). Films made from 30% (w/w) plasticizer concentration exhibited higher thermal stability for all types of plasticizer. Mechanical testing showed that sorbitol films had the highest tensile strength, approximately 2 times that of the triethylene glycol plasticized film and 3 times that of the film made from 1-ethyl-3-methylimidazolium acetate.

The present work aimed at investigating an extraction protocol based on consecutive steps of isoelectric point (pH ~ 4.25) mediated gum swelling and deproteinisation as an alternative method to produce flaxseed gum extracts of enhanced techno-functional characteristics. The osidic and proximate composition, structure conformation, flow behaviour, dynamic rheological and thermal properties of gums isolated from brown and golden flaxseeds were assessed. Gum extraction under near-to-isoelectric point conditions did not impair the extraction yield, residual protein and ash content, whilst it resulted in minor changes in the sugar composition of the flaxseed gum extracts. The deconvolution of the GPC/SEC chromatographs revealed the presence of four major polysaccharidic populations corresponding to arabinoxylans, rhamnogalacturonan–I and two AX-RG-I composite fractions. The latter appeared to minimise the intra- and interchain polymer non-covalent interactions (hydrogen bonding) leading to a better solvation affinity in water and lyotropic solvents. Golden flaxseed gums exerted higher molecular weight (Mw = 1.34–1.15 × 106 Da) and intrinsic viscosities (6.63–5.13 dL g−1) as well as better thickening and viscoelastic performance than the brown flaxseed gum exemplars. Golden flaxseed gums exhibited a better thermal stability compared to the brown flaxseed counterparts and therefore, are suitable for product applications involving severe heat treatments.

WOS: 000442057700082 PubMed: 29859279 The objective of this study was to characterize on the chemical, mechanical, electrical and thermal properties of nanofibrillated cellulose based polyvinyl alcohol (PCNF) and silica (SiCNF) films obtained from Pulpzyme HC 2500 and Celluclast 1.5 L enzyme treated kraft-NaBH4 pulps. Morphological alterations were monitored with SEM. Thermal stability, chemical characterization and crystallization were determined using TGA and FT-IR. Young's and storage moduli of the films were determined via a universal testing machine and DTMA. Dielectric properties were evaluated using an impedance analyzer. In the PCNF films, new vibrations and chemical shifts were observed. The crystallinity values of the SiCNF films calculated from the FT-IR were in agreement with the TGA results, revealing that the lowest crystallinity value was in the SiCNF. The higher Young modulus and elongation at break value were obtained in the neat the CNF films while the lowest values were observed in the neat SiCNF films. However, the SiCNF films revealed higher thermo-mechanical property. The PCNF and SiCNF films exhibit more visible dielectric behavior than that of the neat CNF films. Higher thermal stability, thermo-mechanical and mechanical properties were determined in the Pulpzyme HC 2500 enzyme treated films. Hence, this study evidenced that the properties of CNF films having different matrix are influenced by both the enzymes employed. (C) 2018 Elsevier B.V. All rights reserved. TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [COST 1140022]; Istanbul University Research FundIstanbul University [4806, 19515] The authors thank TUBITAK (Project Number: COST 1140022) for support in this research. The authors also thank Istanbul University Research Fund for its financial support in this study (Project Number: 4806 and Project Number: 19515).

In this study, microcrystalline cellulose (MCC) was extracted from roselle fiber through acid hydrolysis treatment and its properties were compared with those of commercially available MCC. The physicochemical and morphological characteristics, elemental composition, size distribution, crystallinity and thermal properties of the obtained MCC were analyzed in this work. Fourier transform infrared spectroscopy (FTIR) analysis provided clear evidence that the characteristic peak of lignin was absent in the spectrum of the MCC prepared from roselle fiber. Rough surface and slight aggregation of MCC were observed by scanning electron microscopy (SEM). Energy dispersive X-ray (EDX) analysis showed that pure MCC with small quantities of residues and impurities was obtained, with a similar elemental composition to that of commercial MCC. A mean diameter of approximately 44.28μm was measured for MCC by using a particle size analyzer (PSA). X-ray diffraction (XRD) showed the crystallinity increased from 63% in roselle pulp to 78% in roselle MCC, the latter having a slightly higher crystallinity than that of commercial MCC (74%). TGA and DSC results indicated that the roselle MCC had better thermal stability than the roselle pulp, whereas it had poorer thermal stability in comparison with commercial MCC. Thus, the isolated MCC from roselle fibers will be going to use as reinforcing element in green composites and may be a precursor for future roselle derived nanocellulose, and thus a promising subject in nanocomposite research.