Nesrine Mahfoudhi

Effectiveness of almond gum trees exudate as a novel edible coating for improving postharvest quality of tomato (Solanum lycopersicum L.) fruits

The use of coatings is a technique used to increase postharvest life of the fruit. Almond gum exudate was used, in comparison with gum arabic, at concentrations of 10% as a novel edible coating, to preserve the quality parameters of tomato (Solanumlycopersicum). Fruits were harvested at the mature-green stage of ripening. Results showed that the coatings delayed significantly (p < 0.05) the changes in color, weight loss, firmness, titratable acidity, ascorbic acid content, soluble solids concentration, and decay percentage compared to uncoated control fruits. Sensory evaluation proved the efficacy of 10% almond gum and gum arabic coatings to maintain the overall quality of tomato fruits during storage period (20 days). In addition, the difference between gum arabic and almond gum coatings was not significant (p > 0.05) except for pulp color. Therefore, we can suggest the use of almond gum exudate as a novel edible coating extends the shelf-life of tomato fruits on postharvest.

Nutritional composition of Zizyphus lotus L. seeds

BACKGROUND Zizyphus lotus seeds are an unutilized source of vegetable oil and protein and nothing has been reported on their physicochemical characteristics which would indicate the potential uses of these seeds. RESULTS The percentage composition of the Zizyphus lotus seeds is (on a dry-weight basis): ash 1.05%, oil 32.92%, protein 19.11%, total carbohydrate 40.87% and moisture 6.05%. Calcium, potassium and magnesium constitute the major minerals of Zizyphus lotus seeds. The seed proteins are rich in threonine, glutamic acid, leucine, arginine and aspartic acid (26.73%, 17.28%, 13.11%, 9.47% and 7.76%, respectively). The main fatty acids of the oil are oleic (61.93%), linoleic (18.31%) and palmitic (9.14%) acids. Glycerol trioleate (OOO; O: oleic acid) was the most abundant triacylglycerol, representing 26.48% of the total triacyglycerols. β-Tocopherol was the major tocopherol (130.47 mg 100 g(-1) ). This oil was rich in Δ7-campestrol and β-sitosterol (147.82 and 82.10 mg 100 g(-1) oil), respectively. CONCLUSION Zizyphus lotus seeds are rich in fat and protein which are of potential industrial significance. In addition, Zizyphus lotus L. seed oil contained many bioactive compounds. This fact is of great economic interest owing to several applications of Zizyphus lotus L. seeds in the food, cosmetics and medicinal industries.

A Comparative Study on Physicochemical, Rheological and Surface Tension Properties of Tunisian Jujube (Zizyphus lotus L.) Seed and Vegetable Oils

The physicochemical, rheological, surface tension and emulsifying properties of Tunisian jujube (Zizyphus lotus L.) seed oil were investigated and compared with six edible vegetable oils ( olive, corn, soybean, sunflower, groundnut and rapeseed). These results showed that total phospholipids and total tocopherols contents were significantly higher (P < 0.05) in jujube seed oil than those in edible vegetable oils. It was also shown that all oil samples exhibited Newtonian behaviors at shear rate ranged from 10 to 1000 s-1 and the highest viscosity η was observed in jujube seed oil, followed by olive, rapeseed, groundnut, corn, soybean and sunflower oils. In addition, the interfacial tension value of jujube seed oil was significantly lower (17.56 mN/m) than the corresponding of edible vegetable oils. The emulsions were prepared with different type of oil samples and they were kept for 60 days under 4, 30 and 55 °C for stability test. Our results showed that mean droplet size d4,3 of jujube seed oil emulsion was significantly smaller ( P < 0.05) than those of vegetable oils studied. Moreover, jujube seed oil emulsions were stable for 2 months with an average diameter of 213.34 nm. According to the results, jujube seed oil has rheological, interfacial tension, and emulsifying properties that may become interesting for specific applications in several segments of food, cosmetic, pharmaceutical and agrichemical industries.

Kinetic degradation and storage stability of β-carotene encapsulated by spray drying using almond gum and gum arabic as wall materials

Abstract The aim of this study was to evaluate the ability of almond gum, as a novel polymer, to encapsulate β-carotene by spray drying, in comparison with gum arabic. Encapsulation efficiency (EE) was around 66% and 70% using almond gum and gum arabic, respectively, and the reconstituted emulsions had relatively higher particle sizes than the fresh emulsions. A 60-day storage period at 25°C was carried out to investigate the effect of relative humidity (RH) on the kinetic degradation and on the decrease of the color of β-carotene powders. Results showed that β-carotene and color degradations were found to fit well with a first-order kinetic model. Degradation rates increased as RH increased, until a value at which the samples become sticky and collapsed (80% RH) when the degradation rate decreased. These results could prove that collapse phenomena were responsible for the decrease of the degradation rate by decreasing the diffusion of oxygen throughout the wall materials.

Extraction of Polysaccharide From Zizyphus Lotus Fruits

Abstract In this study, response surface methodology (RSM) was used to optimize the extraction conditions of polysaccharides from the pulp of Zizyphus lotus fruit. A central composite rotatable design (CCRD) was used for experimental design and analysis of the results to obtain the optimal processing parameters. Ethanol concentration, extraction temperature, extraction time and water to raw material ratio were found to have a significant effect ( p < 0.05) on the yield of Zizyphus lotus polysaccharide. The 3-D response surface and contour plots, derived from the mathematical model, were applied to determine the optimal conditions. The optimum conditions were as follows: water to raw material ratio 22.04:1, ethanol concentration of 83.30 %, extraction time of 2.65 h, and extraction temperature of 66.31 °C. Under these conditions, the experimental percentage value was 17.35±0.07 %, which is in well close agreement with the value predicted by the model (17.29 %). The results of physicochemical analysis showed that the main sugar composition of Zizyphus lotus polysaccharide, purified by Sephadex G-75 gel permeation chromatography, was glucose followed by arabinose, mannose and rhamnose.

Nanoemulsions as potential delivery systems for bioactive compounds in food systems: preparation, characterization, and applications in food industry

Abstract In recent years there was an increase in the area of nanotechnology applications in food industry. Nanoemulsions are heterogeneous systems consisting of two immiscible phases with one liquid phase being dispersed as nanometric droplets into another continuous phase. Each droplet of the dispersed phase is surrounded by a thin interfacial layer consisting o emulsifier molecules. Nanoemulsions are kinetically stable, requiring energy to be formed. They are highly stable to gravitational separation thanks to the small droplet sizes ranging from 50 to 200 nm. Depending on the affinity of the emulsifier to one of the immiscible phases, we distinguish oil-in-water (o/w) or water-in-oil (w/o) nanoemulsions. Recently, nanoemulsions become one of the most interesting fields of application in food industry, once they act as delivery systems for bioactive compounds. However, the main limitation for their application is their limited long-term stability as well as their nonstraightforward preparation methods.

Rheological and interfacial properties at the equilibrium of almond gum tree exudate (Prunus dulcis) in comparison with gum arabic.

Almond gum contains an arabinogalactan-type polysaccharide, which plays an important role in defining its interfacial and rheological properties. In this study, rheological and interfacial properties of almond gum and gum arabic aqueous dispersions were comparatively investigated. The interfacial tension of almond gum and gum arabic aqueous dispersions was measured using the pendant drop method in hexadecane. The asymptotic interfacial tension values for almond gum were significantly lower than the corresponding values measured for gum arabic, especially at high concentration. Rheological properties were characterized by steady and oscillatory tests using a coaxial geometry. Almond gum flow curves exhibited a shear thinning non-Newtonian behavior with a tendency to a Newtonian plateau at low shear rate, while gum arabic flow curves exhibited such behavior only at high shear rate. The influence of temperature (5–50  ℃) on the flow curves was studied at 4% (m/m) gum concentration and the Newtonian viscosities at infinite and at zero shear rate, for gum arabic and almond gum, respectively, were accurately fitted by an Arrhenius-type equation. The dynamic properties of the two gum dispersions were also studied. Both gum dispersions exhibited viscoelastic properties, with the viscous component being predominant in a wider range of concentrations for almond gum, while for gum arabic the elastic component being higher than the elastic one especially at higher concentrations. The rheological and interfacial tension properties of almond gum suggest that it may represent a possible substitute of gum arabic in different food applications.