Physico-chemical properties of irradiated poly (vinyl alcohol)–Ethylene glycol blend films by γ-rays and ion beam

Poly (vinyl alcohol) is blended with ethylene glycol by casting method to form PVA-EG blend films. These films were irradiated by both N2 ion beam extracted from dc ion source at different ion fluences and γ-rays with various irradiation doses. The effects of ion beam and γ-rays irradiation on the thermal, micro-hardness, and gel fraction properties of PVA-EG blend films were investigated. The gel fraction % and micro-hardness increase with increasing the γ-rays doses up to 150 kGy and then decreased, where they increased at all fluences of ion beam irradiation. The improvement in the gel fraction percentage and micro-hardness suggest that PVA-EG blend films exhibited a crosslink density. The thermal behavior was examined by thermogravimetric analysis and it shows different thermal patterns depending on the type and dose of radiation. The thermal stability parameters of γ-rays- and ion beam-irradiated PVA-EG samples were evaluated using the Ti, Ts, T0.5, Tf temperatures, and activation energy (Ea) values. The thermal stability parameters were dependent on both the type and extent of irradiation dose and fluence. Finally, there is a good agreement between the obtained results from different measurement techniques.

Kinetic and Thermodynamic Characterization of two Polygalacturonases Isolated from the Digestive Juice of the Snail Limicolaria flammea

Polygalacturonases are extensively used in food industries for pectic substances degradation. In this paper, we investigate on thermal stability parameters of two Polygalacturonases previously isolated from digestive juice of the snail Limicolaria flammea for several industrial applications such as fruit juice clarification. Thermal inactivation was carried out in the temperature range of 55°C to 80°C from 15 to 120 min. All results were statistically analysed. The results shown that thermal inactivation of studied acid phosphatases follows first order kinetics. At their optimum temperatures, these enzymes showed high half-lives ranging from 462.06 to 630.10 min and D values from 1535.00 to 2093.64 min suggesting that these two enzymes had a large thermal stability. The high values of ΔG# (93.96 to 94.97 kJ/mol) reveal a better resistance to denaturation. The relatively high activation energies (from 120.35 to 129.13 kJ/mol) and average enthalpy values (from 117.67 to 126.44 kJ.mol−1) could corroborate the good stability of these biocatalyst. All these results suggest that Polygalacturonases from digestive juice of the snail Limicolaria flammea may be profitably exploited in future food industrial applications.

Insight on Extraction and Characterisation of Biopolymers as the Green Coagulants for Microalgae Harvesting

This review presents the extractions, characterisations, applications and economic analyses of natural coagulant in separating pollutants and microalgae from water medium, known as microalgae harvesting. The promising future of microalgae as a next-generation energy source is reviewed and the significant drawbacks of conventional microalgae harvesting using alum are evaluated. The performances of natural coagulant in microalgae harvesting are studied and proven to exceed the alum. In addition, the details of each processing stage in the extraction of natural coagulant (plant, microbial and animal) are comprehensively discussed with justifications. This information could contribute to future exploration of novel natural coagulants by providing description of optimised extraction steps for a number of natural coagulants. Besides, the characterisations of natural coagulants have garnered a great deal of attention, and the strategies to enhance the flocculating activity based on their characteristics are discussed. Several important characterisations have been tabulated in this review such as physical aspects, including surface morphology and surface charges; chemical aspects, including molecular weight, functional group and elemental properties; and thermal stability parameters including thermogravimetry analysis and differential scanning calorimetry. Furthermore, various applications of natural coagulant in the industries other than microalgae harvesting are revealed. The cost analysis of natural coagulant application in mass harvesting of microalgae is allowed to evaluate its feasibility towards commercialisation in the industrial. Last, the potentially new natural coagulants, which are yet to be exploited and applied, are listed as the additional information for future study.

Study of thermal stability of ascospores Aspergillus (Neosartorya) fischeri depending on the concentration of soluble solids in apple juice

Kinetic studies of the thermal inactivation of test crop spores are necessary to develop optimal heat treatment regimes for fruit juices. The purpose of the work is to study the dynamics of changes in the thermal stability parameters DT and z depending on changes in the soluble solids content in canned fruit products using the example of certain types of apple juice products with a pH of 3.80. The regularity of thermal inactivation of ascospores of the mesophilic mold Aspergillus fischeri in concentrated apple juice (JAC) with a soluble dry matter (RSV) content of 70%, in restored apple juice with RSV – 11.2%, and in restored apple juice with pulp with RSV – 16% was studied. The parameters of thermal stability were determined by the capillary method at temperatures of 80, 85, 90, and 95 °C. It was experimentally established that the heat resistance of A. fischeri spores in clarified apple juice was DT 95 °С = 0.16 min, and the parameter value z = 6.76 °C, in apple juice with pulp parameters: DT 95 °C = 0.24 min, z – 7.12 °C, in YaKS – DT 95 °C = 0.39 min, and z – 7.8 °C. The dynamics of thermal stability parameters D and z of A. fischeri mold fungus spores (test cultures) versus RSV concentration of juice products was established. The research results showed that with an increase in the concentration of RSV, the thermal stability of spores increases exponentially. The rate of increase in thermal stability decreases with increasing concentration of RSV. Since the concentration of RSV affects the rheological properties of the product (viscosity), this leads to a change in the kinetics of heating in products with convection heat transfer. Therefore, an increase in the concentration of RSV should inevitably lead not only to an increase in the thermal stability of spores of microorganisms, but also to a shift in the region of optimal modes of heat treatment of products toward an increase in the thermal load to ensure regulatory requirements for microbiological safety.

Effect of silanized sisal fiber on thermo-mechanical properties of reinforced epoxy composites

An effective method was adopted to improve the thermo-mechanical properties of the epoxy composite by functionalization of the sisal fiber. Initially, a neat sisal fiber was acetylated with molar solution of acidic mixture (0.5:1 of HNO3:H2SO4) that removed the content of lignin and hemicellulose and increased the crystallinity of the sisal fiber. The acetylated sisal ( a-sisal) fiber was further treated with 3-aminpropyltriethoxy silane to graft the silanol moieties on sisal fiber. The functionalization of the sisal fiber with 3-aminpropyltriethoxy silane exhibits the strong interaction with epoxy, resulting in homogenous dispersion of the sisal fiber in epoxy. The composite possesses great enhancement in thermal and mechanical properties. The tensile strength in functionalized sisal epoxy composite ( CP-f-Sisal) was significantly enhanced up to 23% in comparison to non-functionalized sisal epoxy composite ( CP-n-Sisal) by adding 15 wt.% of the sisal fiber. In addition, the functionalized sisal epoxy composite ( CP-f-sisal) shows better thermal stability as compared to non-functionalized sisal epoxy composite ( CP-n-sisal). Similar results are attributed by investigating the kinetics of thermal stability parameters that include activation energy and integral procedure decomposition temperature.

The photophysical and metal coordination properties of the N-CH3 substituted porphyrins: H(N-CH3) TPP vs H(N-CH3)OEP

The effect of N -methyl substitution on photophysical and metal coordination properties of the respective derivatives of octaethylporphyrin ( H 2 OEP ) and tetraphenylporphyrin ( H 2 TPP ) was studied by means of steady-state and time-resolved optical spectroscopies combined with semi-empirical quantum-chemical calculations and coordination chemistry methods. In case of H 2 TPP , the insertion of the methyl substituent into the center of the porphyrin macrocycle leads to noticeable nonplanar distortions of the molecule and is accompanied by changes of its photophysical and physicochemical properties towards those manifested by “classical” nonplanar porphyrins. Contrasting to that, N -methyl substituted H 2 OEP does not undergo significant nonplanar distortions and possesses photophysical characteristics mainly similar to unsubstituted H 2 OEP , except for the long-wavelength shift of the absorption and emission bands. The Zn coordination/ Zn complex dissociation and macrocycle thermal stability parameters were also determined for both N -methyl substituted and parent unsubstituted macrocycles, which correlate well with a higher degree of nonplanarity of the N -methyl substituted H 2 TPP as compared to H 2 OEP . Basing on the results of this study the conclusion postulated is that N -methyl substitution has a different effect on the photophysical and coordination properties of H 2 TPP vs. H 2 OEP .