Manel Masmoudi

Preparation and Characterization of Osmodehydrated Fruits from Lemon and Date By-products

An osmotic dehydration process (ODP) was established in order to formulate osmodehydrated fruits from lemon and date by-products. ODP was conducted at 40°C, maintained using an oven, or a water bath with continuous stirring. The kinetics of the osmodehydration in a water bath showed a better mass transfer. Then, osmodehydrated fruit (ODF) preparations of about 40°Brix were formulated using different isotonic solutions (sucrose, glucose/sucrose, glucose, and date juice). All the formulated products showed better characteristics (lower acidity, higher sugar content, etc.) than the untreated lemon by-product. The isotonic solution composition influenced their physical characteristics such as microstructure and viscosity. In fact, ODF prepared in glucose and glucose/sucrose solutions presented more open structures, lower viscosities, and water holding capacities (WHC) than the others. The products were microbiologically stable during 3 months at 4°C. These results support the valorization of lemon and date by-products as ODF that could be consumed or incorporated as an ingredient in food formulations.

Compositional, physical, antioxidant and sensory characteristics of novel syrup from date palm (Phoenix dactylifera L.).

This study is a contribution to valorise date palm sap (Phoenix dactylifera L.) by elaboration of high quality syrup. Sap was concentrated by evaporation and the obtained product was characterized by its physicochemical, rheological, thermal, sensory properties and by its antioxidant activity. Syrups from date palm sap have a good nutritional value marked by high amounts of sugars (58—75 g/100 g fresh matter basis), minerals (2.1—2.6 g/100 g fresh matter basis) and phenolics (147.61—224.55 mg of ferulic acid equivalents/kg fresh weight). Syrup also presents an antioxidant activity that appears related to total phenolic content. Rheological properties indicate that syrup preserves a Newtonian behavior from 10 °C to 55 °C well modeled by Arrhenius equation. Hedonic evaluation showed that consumers’ appreciation of date palm syrup was not significantly different to the most known sap syrup: maple syrup.

Influence of Olive Mill Wastewater (OMW) Spread on Carbon and Nitrogen Dynamics and Biology of an Arid Sandy Soil

Olive mill wastewater (OMW) contains large amounts of organic substances, including phenols, that can have negative environmental consequences when applied to soil. Because of the high concentrations of organic matter and mineral nutrients, OMW holds promise as a fertilizer source for cropping systems. The effects of the addition of 0.5, 1, or 2% OMW to a soil on carbon (C) and nitrogen (N) dynamics and microbiological characteristics of the soil were investigated. Mineral N presented a significant negative correlation with the amount of OMW. The total number of soil bacteria and fungi increased. However, the nitrifying population was sensitive to 2% OMW during the first month. The increase in microbiological activity accelerated the loss of soil organic carbon (SOC). However, the treated soil recovered the SOC, and the total C gains were 2.1, 1.9, and 2.4 g kg−1 for the three doses, whereas the SOC loss was 1.1 g kg−1 for the control.

Pectin extraction from lemon by-product with acidified date juice: rheological properties and microstructure of pure and mixed pectin gels.

The microstructure and the rheological properties of lemon-pectin mixtures were studied and compared to those of pure lemon (high methoxyl: HM) and date (low methoxyl: LM) pectins. Rheological properties were carried out in the presence of 30%, 45% and 60% sucrose, and increasing calcium concentrations (0-0.1%). The presence of date with lemon pectin led to a gel formation at 45% sucrose and in the presence of calcium, which was not the case for lemon pectin alone under the same conditions. It is suggested that lemon and date pectins interacted, leading to gel formations at different gelling temperatures, which were strongly dependant on degree of methylation. These results were confirmed by scanning electron microscopy, which revealed inhomogeneous gels where dense aggregated network and loose, open network areas were present. Addition of calcium to pectin mixture gels led to stronger and faster gel formation.

Effect of ultrafiltration process on physico-chemical, rheological, microstructure and thermal properties of syrups from male and female date palm saps

This study investigates the effect of the ultrafiltration process on physicochemical, rheological, microstructure and thermal properties of syrups from male and female date palm sap. All the studied syrups switched from pseudoplastic rheological behaviour (n=0.783) to Newtonian behaviour (n∼1) from 10 to 50 °C respectively and present similar thermal profiles. Results revealed that the ultrafiltration process significantly affects the rheological behaviour of the male and female syrups. These differences on rheological properties are attributed to the variation of chemical composition between sap and sap permeate syrups. Furthermore, the effect of temperature on viscosity of the syrups was investigated during heating and cooling processes at the same shear rate (50s(-1)). This study provides idea of the stability of the syrup by evaluating the area between heating and cooling curves. Actually, the syrup prepared from male sap permeate is the most stable between the four studied syrups.

Optimization of Insoluble and Soluble Fibres Extraction from Agave americana L. Using Response Surface Methodology

Experimental design methodology was used to determine significant factors affecting the extraction yield of soluble and insoluble fibres from Agave americana L. and in second time to find optimum conditions leading to the highest yield. Results clearly indicated that the temperature, the powder to water (P/W) ratio, and the agitation speed were the most important factors influencing fibres extraction yield which increased with temperature, P/W ratio, and agitation speed. Ionic strength affected significantly soluble fibre extraction yield and was the most important factor among nonsignificant ones influencing insoluble fibres extraction yield. Then, a Box-Behnken design was carried out to maximise fibres extraction. Selected optimal conditions were temperature: 90°C; P/W ratio: 0.1625; agitation speed: 400 rpm; and ionic strength: 1.5 g/L. These conditions yielded 93.02% and 80.46% of insoluble and soluble fibres, respectively. Concentrates showed high fibres purity and good functional properties.