Salem Hamdi

Chemical composition and functional properties of gum exudates from the trunk of the almond tree (Prunus dulcis).

The physicochemical components and functional properties of the gum exudates from the trunk of the almond tree (Prunus dulcis) have been investigated, along with the emulsification and foaming properties. The gum exudates are composed on dry weight basis by 2.45% of proteins, 0.85% of fats and 92.36% of carbohydrates. The latter consist of arabinose, xylitol, galactose and uronic acid (46.8 : 10.9 : 35.5 : 6.0 mass ratio) with traces of rhamnose, mannose and glucose. Moreover, gum exudates are rich in minerals, such as sodium, potassium, magnesium, calcium and iron. The emulsifying capacity was studied for a 20% w/w olive oil in water emulsion as a function of gum concentration (from 3% to 12% w/w in the aqueous phase) as well as pH levels (from 3.0 to 10.0). The most stable and homogeneous emulsion was prepared with an 8% w/w aqueous almond gum solution at a pH between 5.0 and 8.0. In particular, for the same formulation, the emulsion processed by high pressure homogenization (5 passes at 200 MPa) resulted to be extremely stable under accelerated ageing, exhibiting no significant change in droplet size distribution for 14 days at 55 °C. All the tested systems exhibited an extremely low foaming capacity.

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.

Pumpkin (Cucurbita maxima) Seed Proteins: Sequential Extraction Processing and Fraction Characterization

Seed proteins extracted from Tunisian pumpkin seeds ( Cucurbita maxima ) were investigated for their solubility properties and sequentially extracted according to the Osborne procedure. The solubility of pumpkin proteins from seed flour was greatly influenced by pH changes and ionic strength, with higher values in the alkaline pH regions. It also depends on the seed defatting solvent. Protein solubility was decreased by using chloroform/methanol (CM) for lipid extraction instead of pentane (P). On the basis of differential solubility fractionation and depending on the defatting method, the alkali extract (AE) was the major fraction (42.1 (P), 22.3% (CM)) compared to the salt extract (8.6 (P), 7.5% (CM)). In salt, alkali, and isopropanol extracts, all essential amino acids with the exceptions of threonine and lysine met the minimum requirements for preschool children (FAO/WHO/UNU). The denaturation temperatures were 96.6 and 93.4 °C for salt and alkali extracts, respectively. Pumpkin protein extracts with unique protein profiles and higher denaturation temperatures could impart novel characteristics when used as food ingredients.

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.

Functional Properties of Protein Fractions Obtained from Pumpkin (Cucurbita Maxima) Seed

Protein fractions were extracted from pumpkin (Cucurbita maxima) seeds with deionized water, salt solution, and alkali solution, and characterized under alkaline (pH 8) and ionic strength conditions for protein solubility, interfacial pressure, and functional properties. The supernatants obtained from the protein fractions after hydration and centrifugation were designed deionized water supernatant, salt solution supernatant, and alkali solution supernatant. All protein fractions showed poor foamability and very low stability. The designed deionized water supernatant presented the highest emulsifying properties. In terms of stability, designed deionized water supernatant emulsions flocculate during storage but with low rates of coalescence compared to the two other fractions.

Physicochemical, Rheological, and Thermal Properties of Six Types of Honey from Various Floral Origins in Tunisia

The present study was undertaken to determine the physicochemical, rheological, and thermal properties of six types of Tunisian honey samples from various floral origins (eucalyptus, orange, thyme, mint, rosemary, and horehound). All the honey samples exhibited non-Newtonian behavior at a shear rate ranging between 0.01 and 500 s–1, with the highest levels of viscosity (µ) being observed for thyme, followed by eucalyptus, rosemary, mint, orange, and horehound honeys, respectively. The effect of temperature on the dynamic viscosity of the samples followed an Arrhenius-like pattern, with activation energy values ranging from 21.23 to 34.91 kJ/mol. The results from oscillatory rheology analysis also revealed that the loss modulus predominated over the storage one in the whole frequency range. As determined by differential scanning calorimetry, the glass transition (Tg) and melting temperatures of the Tunisian honey samples varied between –41.55 and –47.06 °C and between 197.9 and 221.1°C depending on their sugar compositions, respectively.

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.