Extraction optimisation,antioxidant activity and inhibition on α-amylase and pancreatic lipase of polyphenols from the seeds of Syzygium cumini

The objectives of this study were to determine the optimal extraction conditions of polyphenols from Syzygium cumini seeds by response surface methodology and investigate their antioxidant activity and inhibition on α-amylase and pancreatic lipase. As results, the optimal extraction conditions in the ultrasonic extraction process which maximised total polyphenols content, minimised the IC₅₀ values of α-amylase and pancreatic lipase were determined as follows: extraction time 60 min, ethanol concentration 63% and solvent/solid ratio 44 mL g⁻¹. The main phenolic compounds in partially purified fraction of Syzygium cumini seeds were catechin, epicatechin, kaempferol, gallic, 5-caffeoylquinic, caffeic and ferulic acids. In addition, the partially purified fraction inhibited 87.66 ± 5.55 and 86.61 ± 3.15% of α-amylase and pancreatic lipase, respectively. The results suggested that Syzygium cumini seeds could be explored as a natural antioxidant and could be used as a source of highly antidiabetic and anti-obesity bioactive compounds.     

Optimisation of digestion method for determination of arsenic in shrimp paste sample using atomic absorption spectrometry

The microwave digestion method was developed and verified for the determination of arsenic in shrimp paste samples. Experimental design for five factors (HNO₃ and H₂O₂ volumes, sample weight, microwave power and digestion time) were used for the optimisation of sample digestion. For this purpose, two level half factorial design, which involves 16 experiments, was adopted. The concentration of arsenic was analysed by graphite furnace atomic absorption spectrometry. Design Expert® 7.0 software was used to interpret all data obtained. The combination of 2 mL HNO₃ and 1 mL H₂O₂ volumes, 0.1 g sample weight, 1400 W power and 5 min digestion time was found to be the optimum parameters required to digest the shrimp paste samples. Tests with spiked samples presented good recoveries with relative standard deviations between 0.32% and 5.35%.     

Degradation kinetics of β-carotene in carrot slices during convective drying

The β-carotene degradation was investigated in carrot (Daucus carota L. cv Nantes) slices during convective drying at three temperatures (45, 55, and 65°C) at an airflow rate of 0.2 m s^–1. Degradation kinetics of β-carotene in carrot slices during convective drying followed a first-order reaction. Drying temperature showed a significant effect on the degradation of β-carotene in carrot slices. The range of the reaction rate constants for β-carotene loses were 0.23 ± 0.08 –0.48 ± 0.04 h^–1. The activation energy of β-carotene degradation is found 33.33 ± 0.05 kJ mol^–1. Half-life time was calculated as 3.02 ± 0.04 h at 45°C, which dropped to 1.43 ± 0.03 h at 65°C.     

Effect of methyl methacrylate content on coatings’ properties of palm oleic acid-based macromer

The macromer was synthesized using medium oil length oleic acid, phthalic anhydride, and glycerol. The synthesized macromer and methyl methacrylate (MMA) were copolymerized by free radical polymerization in toluene. The ratio between the macromer and MMA changed, and the effects on different properties of the copolymers, such as glass transition temperature (T _g) and film properties, were studied. The macromer and copolymer structures were characterized by FTIR and ¹H NMR spectroscopies. The coatings prepared with the highest ratio of MMA exhibited better overall physico-chemical properties. Alternatively, Tafel polarization curves showed that the corrosion rate value in NaCl solution decreases significantly when the MMA content is increased. Dynamic mechanical analysis results revealed that the increasing amounts of MMA lead to increasing T _g values of copolymers.     

Microstructure and phase composition of cordierite-based co-clinker

The aim of this work is to study the effect of phase composition and microstructure of cordierite-based co-clinkers on the electrical properties and coefficient of thermal expansion of cordierite briquettes. To achieve this aim talc and kaolinite samples were collected from quarries in the Egyptian desert. The samples are characterized using XRD, XRF, polarized light, cathodoluminescence and SEM microscopy attached with EDAX, in addition to X-ray micro-computed tomography (3D- µXCT). The electrical properties and coefficient of thermal expansion of the cordierite briquettes are determined using HiTESTER instrument and automatic Netzsch DIL402 PC dilatometer, respectively.Five talc-based batches were shaped and fired in the temperature range 1000–1350 °C for 2 h. The microstructural and physical characteristics of the resulted cordierite-based co-clinkers depend mainly on the viscosity of the liquid phase developed during firing. The microchemistry of the cordierite briquettes confirms their enrichment of both cordierite and ferroan-cordierite crystallized directly from locally developed melts. The dielectric constant and loss factor values for cordierite briquettes allow their possible use as insulator components in electronic applications.     

Fly Ash-based Geopolymer Lightweight Concrete Using Foaming Agent

In this paper, we report the results of our investigation on the possibility of producing foam concrete by using a geopolymer system. Class C fly ash was mixed with an alkaline activator solution (a mixture of sodium silicate and NaOH), and foam was added to the geopolymeric mixture to produce lightweight concrete. The NaOH solution was prepared by dilute NaOH pellets with distilled water. The reactives were mixed to produce a homogeneous mixture, which was placed into a 50 mm mold and cured at two different curing temperatures (60 °C and room temperature), for 24 hours. After the curing process, the strengths of the samples were tested on days 1, 7, and 28. The water absorption, porosity, chemical composition, microstructure, XRD and FTIR analyses were studied. The results showed that the sample which was cured at 60 °C (LW2) produced the maximum compressive strength for all tests, (11.03 MPa, 17.59 MPa, and 18.19 MPa) for days 1, 7, and 28, respectively. Also, the water absorption and porosity of LW2 were reduced by 6.78% and 1.22% after 28 days, respectively. The SEM showed that the LW2 sample had a denser matrix than LW1. This was because LW2 was heat cured, which caused the geopolymerization rate to increase, producing a denser matrix. However for LW1, microcracks were present on the surface, which reduced the compressive strength and increased water absorption and porosity.     

Reflection and transmission coefficient of yttrium iron garnet filled polyvinylidene fluoride composite using rectangular waveguide at microwave frequencies

The sol-gel method was carried out to synthesize nanosized Yttrium Iron Garnet (YIG). The nanomaterials with ferrite structure were heat-treated at different temperatures from 500 to 1000 °C. The phase identification, morphology and functional groups of the prepared samples were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. The YIG ferrite nanopowder was composited with polyvinylidene fluoride (PVDF) by a solution casting method. The magnitudes of reflection and transmission coefficients of PVDF/YIG containing 6, 10 and 13% YIG, respectively, were measured using rectangular waveguide in conjunction with a microwave vector network analyzer (VNA) in X-band frequencies. The results indicate that the presence of YIG in polymer composites causes an increase in reflection coefficient and decrease in transmission coefficient of the polymer.     

Solvent-Aided Crystallization for Biodiesel Purification

The application of solvent-aided crystallization (SAC) is based on the addition of a solvent, here 1-butanol, to crude biodiesel to catalyze the purification process by separating biodiesel from contaminants via crystallization process. Response surface methodology was applied to optimize the process parameters of SAC, represented by biodiesel purity. The purified biodiesel was analyzed by means of gas chromatography-mass spectrometry for the composition of the present fatty acid methyl ester (FAME). Under the predicted optimum process conditions within the experimental ranges for the highest biodiesel purity, the predicted biodiesel purity was 99.375 %.     

Review on Progressive Freeze Concentration Designs

Progressive freeze concentration (PFC) is a process where only a large single ice crystal is formed in the system and grown on the cooling surface so that the separation between the ice crystal and the mother solution is very easy. This makes the system very simple and leads to a lower cost. The conventional setup of PFC produces ice with high purity but lower productivity than suspension freeze concentration (SFC). The volume of ice produced is also usually low. Hence, continued areas of the development for PFC system include the quest for improved productivity and better efficiency. Different kinds of design have been investigated, which are easy to operate and cost-effective besides the ability to obtain high quality of product and better efficiency of the system. The PFC system is recognized as a good alternative if high-quality products can be produced with higher productivity. In this article, previous researches on PFC designs were reviewed for the purpose of providing an understanding on methods of designing a PFC system and also to provide references for future application of PFC.