Enzymatic and Chemical Cross-Linking of Bacterial Cellulose/Fish Collagen Composites-A Comparative Study.

This article compares the properties of bacterial cellulose/fish collagen composites (BC/Col) after enzymatic and chemical cross-linking. In our methodology, two transglutaminases are used for enzymatic cross-linking-one recommended for the meat and the other proposed for the fish industry-and pre-oxidated BC (oxBC) is used for chemical cross-linking. The structure of the obtained composites is characterized by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy, and their functional properties by mechanical and water barrier tests. While polymer chains in uncross-linked BC/Col are intertwined by H-bonds, new covalent bonds in enzymatically cross-linked ones are formed-resulting in increased thermal stability and crystallinity of the material. The C2-C3 bonds cleavage in D-glucose units, due to BC oxidation, cause secondary alcohol groups to vanish in favor of the carbonyl groups' formation, thus reducing the number of H-bonded OHs. Thermal stability and crystallinity of oxBC/Col remain lower than those of BC/Col. The BC/Col formation did not affect tensile strength and water vapor permeability of BC, but enzymatic cross-linking with TGGS improved them significantly.

The effect of thermal and irradiation treatments on structural and physicochemical properties of octenyl succinate maize starches.

The aim of this paper was to evaluate the effect of thermal treatment and UV irradiation on structural and physicochemical properties of octenyl succinate (OS) maize starches differing in content of OS groups (0.76%-2.38%). X-ray diffraction (XRD), gel permeation chromatography (GPC), and electron paramagnetic resonance (EPR) spectroscopy were used to estimate structural characteristics of octenyl succinate starches and their physically treated counterparts. Starch functional properties were also determined. XRD spectra and hydrodynamic volume distribution revealed that growth of octenyl succinate groups' content resulted in stabilization of starch structure, which was confirmed by processes of radical formation, stimulated by thermal and UV treatments. It was found, on the basis of measurements of water binding capacity, water solubility and intrinsic viscosity, that OSA addition changed physicochemical properties of starch and influenced the course of physical modifications. It was established that temperature affected starch properties to a greater extent than UV.

Changes in the physicochemical properties of barley and oat starches upon the use of environmentally friendly oxidation methods.

In this work, two environmentally friendly modification methods, UV irradiation and thermal treatment, were applied for the first time for modifications of oat and barley starches. Their impacts on starch properties were compared with those observed for starch oxidation with NaClO. XRD, EPR, FTIR, SEM and SEC methods were used to characterize the effects of modifications on starch structures. The decreases in molecular weight and crystallinity degree showed the destruction of starch structures upon prolonged UV irradiation and thermal treatment, more advanced in barley starch. The process of radical formation, studied by EPR, occurring to a larger extent in this starch, confirmed lower stability of barley starch structure. The alterations of starch structures correlated well with changes in its functional properties. It was found that UV irradiation was an effective oxidizing agent, whereas heating led mainly to the depolymerization of starch chains.

Effect of thermal treatment on potato starch evidenced by EPR, XRD and molecular weight distribution.

Effect of heating of the potato starch on damages of its structure was investigated by quantitative electron paramagnetic resonance (EPR) spectroscopy, X-ray diffraction and determination of the molecular weight distribution. The measurements were performed in the temperature range commonly used for starch modifications optimizing properties important for industrial applications. Upon thermal treatment, because of breaking of the polymer chains, diminishing of the average molecular weights occurred, which significantly influences generation of radicals, evidenced by EPR. For the relatively mild conditions, with heating parameters not exceeding temperature 230 °C and time of heating equal to 30 min a moderate changes of both the number of thermally generated radicals and the mean molecular weight of the starch were observed. After more drastic thermal treatment (e.g. 2 h at 230 °C), a rapid increase in the radical amount occurred, which was accompanied by significant reduction of the starch molecular size and crystallinity. Experimentally established threshold values of heating parameters should not be exceeded in order to avoid excessive damages of the starch structure accompanied by the formation of the redundant amount of radicals. This requirement is important for industrial applications, because significant destruction of the starch matrix might annihilate the positive influence of the previously performed intentional starch modification.