EFFECT OF HEAT AND MASS TRANSFER AND THERMAL RADIATION ON A STEADY MHD CONVECTIVE FLOW WITH VISCOUS DISSIPATION AND SUCTION/INJECTION

Our motive is to examine the impact of thermal radiation and suction or injection with viscous dissipation on an MHD boundary layer flow past a vertical porous stretched sheet immersed in a porous medium. The set of the flow equations is converted into a set of non-linear ordinary differential equations by using similarity transformation. We use Runge Kutta method and shooting technique in MATLAB Package to solve the set of equations. The impact of non-dimensional physical parameters on flow profiles is analysed and depicted in graphs. We observe the influence of non-dimensional physical quantities on the Nusselt number, the Sherwood number, and skin friction and presented in tables. A comparison of the obtained numerical results with existing results in a limiting sense is also presented. We enhance radiation to observe the deceleration of fluid velocity and temperature profile for both suction and injection. While enhancing porosity parameter accelerates velocity whereas decelerates temperature profile. As the heat source parameter increases, the temperature of the fluid decreases for both suction and injection, it has been found. With the increasing values of the radiation parameter, the skin friction and heat transfer rate decreases. Increasing magnetic parameter decelerates the skin friction, Nusselt number, and Sherwood number.

DRYING OF ZUCCHINI AND CARROT SLICES: INFLUENCE OF TISSUE STRUCTURE ON MASS TRANSFER PARAMETERS

The present work aimed mainly at investigating the influence of tissue structure on dehydration characteristics of zucchini and carrot. Microwave power levels of 100, 350, 550 and 750 W used to dehydrate the samples with thicknesses of 3, 5, 7 and 9 mm. The results showed that moisture removal from the slices occurred in a short accelerating period at the process beginning followed by a falling rate period. The moisture diffusivity increased with both increasing microwave power and the samples thickness where the average values for zucchini and carrot slices changed from 1.17×10-8 to 9.42×10-8 and from 0.73×10-8 to 5.51×10-8 m2 s-1, respectively. The average activation energy for zucchini and carrot slices varied in the range of 1.22–1.68 and 1.57–1.84 W g-1, respectively and decreased with increasing samples thickness.

ANTIOXIDANT AND ANTIMICROBIAL ACTIVITY OF BIOACTIVE CHITOSAN FILMS

Interest in the development of films for food preservation is increasing due to the improvement achieved in the food preservation time with the advent of new packaging technologies. Chitosan is a widely used biopolymer produced from the deacetylation of chitin, which has a good capacity to form suitable films as food packages. On the other hand, bioactive compounds such as gallic acid and salicylic acid act as inhibitors of the oxidant activity of free radicals and delay the decomposition of food. In this sense, the preparation of chitosan films modified with the mixture incorporation of salicylic acid/sorbitol or gallic acid/Tween 80 was proposed, using sorbitol or Tween 80 as plasticizers. Both films (chitosan/gallic acid/Tween 80 and chitosan/salicylic acid/sorbitol) showed a good antioxidant capacity in while the chitosan/gallic acid/Tween 80 film evidenced its antimicrobial activity against Escherichia coli ATCC 25922 causing a diminution of unit forming colony

DRYING, COLOUR AND REHYDRATION CHARACTERISTICS OF ORANGE SLICES UNDER INFRARED RADIATION HEATING

The effect of different infrared (IR) powers on drying of orange slices was investigated in infrared dryer. The orange slices dried at 62, 74 and 88 W infrared powers and constant slice thickness of 6 mm. Results showed that drying, colour and rehydration characteristics of orange slices were greatly influenced by infrared power. The drying data were fitted with five mathematical models available in the literature. Based on the statistical tests applied to make an assessment, the model of Midilli and Kucuk was found to satisfactorily explain drying kinetics of orange slices for all drying conditions. The Fick’s diffusion model was used to calculate the effective moisture diffusivity (Deff) of orange slices. The value of Deff varied from 1.59×10-10 to 2.49×10-10 m2/s. It was found that the effective moisture diffusivities increased with increasing IR power. Activation energy was estimated by a modified Arrhenius type equation as 2.11 kW/kg. As the infrared power increased, the rehydration ratio was found to be reduced. Furthermore, with increase of infrared power, the values of a and DE increased, whereas the values of L, b and C decreased.

CHEMICAL CONSTITUENTS AND ACETYLCHOLINESTERASE ACTIVITY FROM Polyalthia sumatrana (Miq.) Kurz

This study was carried out to investigate the phytochemicals from Polyalthia sumatrana and their acetylcholinesterase inhibitory activity. Fractionation and purification of the leaves of P. sumatrana led to the isolation and identification of five alkaloids; boldine (1), norboldine (2), liriodenine (3), predicentrine (4), laurotetanine (5) together with β-sitosterol (6), β-sitostenone (7), vanillin (8), vanillic acid (9) and cinnamic acid (10). The structures of these compounds were obtained by analysis of their spectroscopic data, as well as the comparison with that of reported data. Acetylcholinesterase inhibitory activity revealed that all isolated alkaloids were found to inhibit AChE with percentage inhibition values ranged from 45.0 to 80.6%.

EFFECTS OF MOLAR RATIO, FREQUENCY, WATER CONTENT AND TEMPERATURE ON DIELECTRIC PROPERTIES OF DEEP EUTECTIC SOLVENTS

In this study, deep eutectic solvents (DESs) were prepared using choline-chloride as the hydrogen-bond acceptor and glycerol, formic acid and acetic acid as the hydrogen-bond donor. The effect of different process parameters such as molar ratio (1:2, 1:3 and 1:4), water content (15%, 30% and 45%), temperature (25, 50 and 75 °C) and frequency on dielectric properties of the DESs were examined. In conclusion, the highest dielectric constant value was detected at 25 °C for all DESs. Moreover, for all DESs, it was found that a decrease in water content resulted in a decrease in both dielectric constant and loss factor values. This can be explained by the absence of free water molecules which are responsible from dipole rotation mechanism. In light of the results, if DES will be used in microwave extraction, formic or acetic acid containing DESs might give more successful results compared to the one with glycerol.

A two-parameter model for the determination of the partition coefficient for TRS in a culture medium

A two-parameters model was applied for the determination of the activity coefficient for a culture medium, and compared with Henry's law, the extended UNIQUAC, and experimental data obtained from an experimental setup system, consisting of a liquid culture media Thiobacillus (ATCC 290) with hydrogen sulfide (H2S), dimethyl sulfide (DMS), methyl mercaptan (MM), and dimethyl disulfide (DMDS), respectively. The ANOVA indicates that the use of Henry's law is not appropriate for MM and H2S with R2adj values of -106.15% and -53.33%, respectively. The extended UNIQUAC model and the two-parameter model were able to describe the system with values of 76.94% and 94.15% for DMS and DMDS in the case of UNIQUAC Extended, respectively, and 88.50% and 98.08% using the two-parameter model. These results show that the two-parameter model is able to describe the system, using a low number of parameters. However, the extended UNIQUAC shows better results but presenting a high level of over-parameterization. Henry's law showed significant deviations, not being representative of all analyzed cases. The two-parameter model is presented as an alternative to describing systems in which vapor-liquid mass transfer is involved in culture media, providing a better approximation than traditional models and lower calculation costs than complex models.

DESIGN, CONSTRUCTION AND TESTING OF A COLD STORE WITH WATER-COOLED CHILLER

Objective of this research was to design, construction and test of a cold store with chiller unit. Dimensions of the cold store were 5x4x3m. Heat load was calculated and capacity of cooling system was determined. Ambient temperature was set 2oC and relative humidity 90% for cold store testing. Ambient temperature, relative humidity and air velocity were measured for 3 different levels and 12 points for each level in the cold store. Total heat load and capacity of cooling system were calculated 5222 kcal/h. and 6.07 kW respectively. The descriptive statistics were calculated for the ambient temperature; mean, 2.82oC, standard deviation 0.02oC and CV(%) 0.56, and for the relative humidity; mean 88.01%, standard deviation 0.61 (%) and CV(%) 0.70 and for the air velocity mean 0.37m/s, standard deviation 0.22 m/s, CV 33.45 %. Even the air velocity CV was high, the ambient temperature and relative humidity variations were evaluated very good.

THE EFFECT OF DRYING TEMPERATURE, CUTTING TYPES, STORAGE DEGREE AND PERIOD ON PHYSICAL, CHEMICAL AND PHYSICOCHEMICAL PROPERTIES OF RED CAPIA PEPPER

This work was undertaken to evaluate the effects of different drying temperatures ​​(50, 60 and 70 oC) and cutting types (ring and cube) on the physical, chemical and physiochemical properties of red capia pepper during storage (14 days) both at room temperature and cold storage. Convective drying (CVD) at 50, 60 and 70 oC was applied to obtain dried red capia peppers. The effects of CVD on color values (L*, a*, b*), rehydration ratio, selected chemical properties (dry matter, pH and titratable acidity) and bioactive compounds (total phenolic content and antioxidant capacity) of thirteen dried red capia peppers were compared. The samples dried at 60 oC in ring forms under cold storage (6R-CD samples) showed the highest dry matter, pH, titratable acidity and rehydration ratio (87.06%, 5.69, 807.15 mg citric acid/100 g, 6.72%, respectively). The closest L*, a*, b*values to the fresh pepper samples were achieved for 6R-CD samples (L*:29.87, a*:12.83, and b*:17.03). In addition, 6R-CD samples resulted with highest antioxidant capacity and total phenolic content in all storage times.

CFD MODELLING AND VALIDATION OF AMBIENT FACTORS IN EVAPORATIVE COLD STORE FOR PEACH STORAGE

Spatial variation of temperature and relative humidity were estimated with Computational Fluid Dynamics (CFD) at top, middle and base levels for peach storage at +1oC and 90% relative humidity and verified with measured data in a cold store with evaporative cooling system. Storage temperature was +1oC and relative humidity 90% for peach storage. Ansys Fluent Software was used for CFD modelling. CFD models were validated with sensors measurements. Results were evaluated by using descriptive statistics, relative error and variance analyses. Mean difference between the model and measurements was calculated as 0.51oC for ambient temperature and as 3.47 % for relative humidity. Relative error of the CFD model was calculated as 9.77 for the ambient temperature and 1.29 for relative humidity for peach storage. The developed CFD models estimated the ambient factors with an acceptable error in the evaporative cold store for peach storage.