Ahmed Al-Alawi

Sensory and textural changes in maturing Omani dates

The astringency and texture of the Omani date variety khalas were examined at progressive levels of maturity. Astringency was measured using descriptive sensory analysis, while texture was measured with a texture meter. The phenolic (referred to as ‘tannin’) and polygalacturonic acid (referred to as ‘pectin’) contents of the dates were measured by colorimetry. It was found that astringency closely followed levels of tannin content measured on a fresh weight basis. The most astringent dates were at the kimri and tamar stages of maturity, which also had the highest fresh weight tannin content of 2.8 and 1.5 g kg−1 respectively. The least astringent dates were at the rutab stage of maturity, which also had the lowest fresh weight tannin content (1.0 g kg−1). On a dry weight basis the tannin content decreased as the dates matured. The texture of the dates closely followed the degree of methylation of the date pectin. The softest dates were at the tamar stage of maturity, with a degree of methylation of 39%, while the hardest dates were at the kimri stage, with a degree of methylation of 72%. The polygalacturonic acid content did not appear to affect the texture, since the fresh weight polygalacturonic acid content was higher at the tamar stage (11–13 g kg−1) than at the kimri stage (6–9 g kg−1) of maturity. Traditionally, dates at the rutab stage are preferred since they are considered the sweetest and softest. Although tamar dates have the highest sugar content, owing to moisture loss, rutab dates may be preferred not necessarily for their great sweetness and soft texture, but rather for their lack of astringency. © 2000 Society of Chemical Industry

Drying Kinetics and Allicin Potential in Garlic Slices during Different Methods of Drying

Drying kinetics of garlic cloves was investigated by drying 5 mm thick slices in air, vacuum, and nitrogen atmosphere. The drying coefficient and lag factor were estimated from the slope and intercept of the moisture ratio time plot based on a model by Dincer-Hussain. Both drying coefficient and lag factor increased with increasing drying temperature. The diffusivity estimated from the Ficks law of diffusion and Dincer-Hussains model differed, because Ficks law assumes negligible external mass transfer, whereas Dincer-Hussains model considers both internal and external mass transfer resistance. Allicin, which is rapidly produced by the action of alliinase on alliin when fresh tissue is crushed, is the main biologically active phytochemical of garlic. Air drying at 50°C, vacuum drying at 50 and 60°C, nitrogen atmosphere drying at 40°C gave lowest losses of allicin potential. In general, the loss of allicin potential increased with increasing drying temperature, and drying below 50°C should be the best drying condition for the retention of allicin potential. This could be due to higher retention of alliinase activity during lower temperature drying. The loss of allicin potential decreased with the increase of slice thickness. This may be explained by lower structural damage and by lower shrinkage in the case of thicker slices.

Viscoelastic properties of pectin-co-solute mixtures at iso-free-volume states.

Small-deformation oscillatory measurements were performed on pectin-sucrose-glucose syrup systems at a total level of solids of 81%, with the polysaccharide content being fixed at levels of industrial use (1%). The experimental temperature range was between 50 and - 50 degrees C. Analysis of the temperature dependence of viscoelastic processes by the equation of Williams, Landel, and Ferry provides values of fractional free volume for the temperatures covering the glass transition region. The shift factors used in the conversion of mechanical spectra into master curves were normalised at suitably different temperatures so that their temperature dependence becomes coincident. The treatment implies an iso-free-volume state and relates to changes in the monomeric friction coefficient with increasing levels of intermolecular interactions in the mixture. A free-volume related glass transition temperature was defined and manipulated markedly by introducing pectin of variable degrees of esterification to the sucrose-glucose syrup system.

Characterization of Red Seaweed Extracts Treated by Water, Acid and Alkaline Solutions

Abstract Seaweed contained health functional polysaccharides and polyphenols. Five extracts were prepared from red seaweed Melanothamnus somalensis; two of these were aqueous at 20°C (F1) and 70°C (F2), followed by acid (F3), alkali (F4) and acid-washed (F5) treatments. Molecular characteristics of extracts were measured by high-performance liquid chromatography and Fourier transform infrared (FTIR) analyses. Health functionality was determined by sulfate and polyphenol contents, and thermal characteristics were determined by modulated differential scanning calorimetry. Extract F3 contained the highest levels of sulfate followed by F2, F1, F4 and F5, respectively. Similarly, F3 contained the highest polyphenol followed by F4, F2, F1 and F5, respectively. Molecular weight distribution of F1 showed wider distribution of sizes (MW: 1.0 × 103 – 3.0 × 107), and F5 showed a sharp peak (MW: 3.1 × 103); whereas F2, F3 and F4 indicated bimodal distribution. FTIR indicated that all fractions contained agar except F5 and sulfate ester group was attached to carbon 6 of the saccharide.

Optimal allocation of PV systems in distribution networks using PSO

This manuscript presents a case study to determine the optimal location and size of photovoltaic systems in an electric distribution networks using particle swarm optimization (PSO) such that network voltage profile is improved and losses are minimized. The distribution network of Masirah Island, Oman, is considered as a case study system. The test system is modeled and simulated using MATLAB load flow toolbox.

Red Seaweed (Hypnea Bryodies and Melanothamnus Somalensis) Extracts Counteracting Azoxymethane-Induced Hepatotoxicity in Rats

Background: Azoxymethane (AOM) is a well-known colon cancer-inducing agent in experimental animals via mechanisms that include oxidative stress in rat colon and liver tissue. Few studies have investigated AOM-induced oxidative stress in rat liver tissue. Red seaweeds of the genera Hypnea Bryodies and Melanothamnus Somalensis are rich in polyphenolic compounds that may suppress cancer through antioxidant properties, yet limited research has been carried out to investigate their anti-carcinogenic and antioxidant influence against AOM-induced oxidative stress in rat liver. Objective: This study aims to determine protective effects of red seaweed (Hypnea Bryodies and Melanothamnus Somalensis) extracts against AOM-induced hepatotoxicity and oxidative stress. Materials and Methods: Sprague–Dawley rats received intraperitoneal injections of AOM, 15 mg/kg body weight, once a week for two consecutive weeks and then orally administered red seaweed (100 mg/kg body-weight) extracts for sixteen weeks. At the end of the experiment all animals were overnight fasted then sacrificed and blood and liver tissues were collected. Results: AOM treatment significantly decreased serum liver markers and induced hepatic oxidative stress as evidenced by increased liver tissue homogenate levels of nitric oxide and malondialdehyde, decreased total antioxidant capacity and glutathione, and inhibition of antioxidant enzymes (catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase and superoxide dismutase). Both red seaweed extracts abolished the AOM-associated oxidative stress and protected against liver injury as evidenced by increased serum levels of liver function markers. In addition, histological findings confirmed protective effects of the two red seaweed extracts against AOM-induced liver injury. Conclusion: Our findings indicate that red seaweed (Hypnea Bryodies and Melanothamnus Somalensis) extracts counteracted oxidative stress-induced hepatotoxicity in a rat model of colon cancer.