النشر العلمي

  • Influence of sonication process parameters to the state of liquid concentration of extracted rebaudioside A from Stevia (Stevia rebaudiana bertoni) leaves

The purpose of this work was to develop a process to obtain Stevia extract of a better quality and quantity under influence of ultrasound technique. The chemical compositions, anti-nutritional factor and heavy metals of raw material were tested firstly in (w w−1) in our previous work. The extraction process was assisted by ultrasonication at power 360 W for 12 min using three different types of solvents (water, ethanol and isopropyl alcohol) in different concentrations, that is, 10, 20, 30, 40, 50, and 60% (v v−1) to optimize the extraction process. Stevia leaves extractions, analyzed by HPLC, indicated that isopropyl alcohol (60% v v−1) gave the highest rebaudioside A yield (35 g 100 g−1). This optimum concentration was used in the next set of experiments to optimize ultrasonic power and time. Optimum applied power and sonication time was found 18 min and 480 W, respectively. The extraction yield obtained under optimum process conditions for water, ethanol and isopropyl alcohol were 32.79, 33.85 and 37.10 (g 100 g−1), respectively. Compared to classical methods like maceration and heat extraction, the utilization of ultrasound-assisted extraction proved to be a much simpler and efficient way to obtain rebaudioside A from Stevia rebaudiana leaves.

published in Arabian Journal of Chemistry

  • Physico-chemical Assessment and Rebauidioside A. Productively of Natural Sweeteners (Stevia Rebaudiana Bertoni)

Stevia rebaudian Bertoni, belonging to the Compositae family, is a sweet herb contains diterpene glycosides, namely, stevioside, rebaudiosides A–F, steviolbioside, and dulcoside A, which are responsible for the typical sweet taste. Stevia (Stevia rebaudian Bertoni) leaves were analyzed for their physiochemical properties, chemical composition and microbiological contamination in addition to rebauidioside A productively. The carbohydrates content was 63.10%, while the moisture, fiber, protein, ash, fat and reducing sugar contents were 10.73%, 5.03%,13.68%,12.06%,6.13% and 4.50%, respectively. Anti-nutritional value (tannin) was 5.43 %. The total soluble substance was 17.03%. The Stevia leaves showed a good antimicrobial agent for all tested bacterial groups including Coliforms, Staphylococcus. Rebauidioside A was extracted and purified from the dried Stevia leaves by ultrasonic-assisted extraction method. The optimum extraction time was 6 min in which the maximum rebauidioside A content was obtained (32.79 g/100 g). Results show that particle size of sample treated for 6 min is bigger than those for 12, 18 and 24 min. Application of ultrasound-assisted extraction on the Stevia plant substantially affects the Color, and particle size of the stevia leaf extract and rebauidioside A yield.

published in Journal of Food and Nutrition Research

  • Biosynthesis of 2-O-α-D-glucopyranosyl-L-Ascorbic Acid from Maltose by Cyclodextrin Glucanotransferase from Bacillus sp. SK 13.002

In this work 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) was synthesized by Cyclodextrin glucanotransferase (CGTase) from Bacillus sp. SK 13.002 with L-ascorbic acid (AA) as an acceptor and maltose as a glycosyl donor. AA-2G production was analyzed by HPLC and was confirmed by LC/MS results. The reaction parameters, such as pH (4.0-9.0), temperature (25-50°C), time (0-30 h), substrate ratios and enzyme concentration were optimized. The results showed that the optimum condition was pH 8.0 at 37°C for 24 h, 1:1 maltose to AA substrates mass ratio, and 200 U/mL of CGTase. Under these conditions, the production of AA-2G was 5.5 g/L, this result indicate that CGTase from Bacillus sp. SK 13.002 can effectively uses maltose as a glycosyl donor to produce AA-2G in high yield

published in Journal of Food and Nutrition Research

  • Physicochemical, Nutritional and Functional Properties of the Epicarp, Flesh and Pitted Sample of Doum Fruit (Hyphaene Thebaica)

Abstract In this study, the physicochemical, nutritional and functional properties of epicarp, flesh and pitted samples of doum fruit (Hyphaene thebaica) were assessed. Results on carbohydrate content revealed that the flesh, pitted fruit and epicarp samples contained 72.50%, 65.61% and 44.17% respectively. Total fiber was highly concentrated in the epicarp accounting for more than 40%. It was further revealed that the fruit contained substantial amounts of essential minerals as follows: sodium 364.7 mg/100 g, calcium 284 mg/100 g and iron 12.18 mg/100 g in the epicarp while the following were contained in the flesh part of the fruit: potassium 2947.6 mg/100 g, magnesium 185.62 mg/100 g and phosphorus 154.6 mg/100 g. Vitamin content was determined by RP-HPLC and the results showed that doum fruit is a good source of vitamin B-complex which was found it at high portion in epicarp with the variance of 3.6 mg/100 g in niacin (B3) content to 13.6 mg/100 g in pyridoxine (B6) content. Monosaccharide content was determined by using HPAEC-PAD and the results showed that the flesh of the doum fruit is a good source of glucose and fructose. There was a significant difference in color parameters between samples. Bulk density results were 0.73, 0.75 and 0.95 mg/ml for epicarp, pitted fruit and flesh respectively. It can be concluded that the doum fruit contained essential nutrients and functional properties which can be exploited for various useful applications.

published in Journal of Food and Nutrition Research

  • Electrochemical Genosensor To Detect Pathogenic Bacteria (Escherichia coli O157:H7) As Applied in Real Food Samples (Fresh Beef) To Improve Food Safety and Quality Control

ABSTRACT: The electrochemical genosensor is one of the most promising methods for the rapid and reliable detection of
pathogenic bacteria. In a previous work, we performed an efficient electrochemical genosensor detection of Staphylococcus aureus
by using lead sulfide nanoparticles (PbSNPs). As a continuation of this study, in the present work, the electrochemical
genosensor was used to detect Escherichia coli O157:H7. The primer and probes were designed using NCBI database and Sigma-
Aldrich primer and probe software. The capture and signalizing probes were modified by thiol (SH) and amine (NH2),
respectively. Then, the signalizing probe was connected using cadmium sulfide nanoparticles (CdSNPs), which showed welldefined
peaks after electrochemical detection. The genosensor was prepared by immobilization of complementary DNA on the
gold electrode surface, which hybridizes with a specific fragment gene from pathogenic to make a sandwich structure. The
conductivity and sensitivity of the sensor were increased by using multiwalled carbon nanotubes (MWCNT) that had been
modified using chitosan deposited as a thin layer on the glass carbon electrode (GCE) surface, followed by a deposit of bismuth.
The peak currents of E. coli O157:H7 correlated in a linear fashion with the concentration of tDNA. The detection limit was 1.97
× 10−14 M, and the correlation coefficient was 0.989. A poorly defined current response was observed as the negative control and
baseline. Our results showed high sensitivity and selectivity of the electrochemical DNA biosensor to the pathogenic bacteria E.
coli O157:H7. The biosensor was also used to evaluate the detection of pathogen in real beef samples contaminated artificially.
Compared with other electrochemical DNA biosensors, we conclude that this genosensor provides for very efficient detection of
pathogenic bacteria. Therefore, this method may have potential application in food safety and related fields.

published in Journal of Agricultural and Food Chemistry

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