Ultrafiltration and thermal processing effects on Maillard reaction products and biological properties of date palm sap syrups (Phoenix dactylifera L.).

The effect of ultrafiltration process and temperature concentration on MRPs content and antioxidant, antimicrobial and cytotoxic properties of date palm sap syrups were investigated. MRPs were analyzed by HPLC. Antioxidant activity was evaluated by reducing power and DPPH free radical and H2O2 scavenging activities. Antimicrobial activity was evaluated by the agar disk diffusion method. In vitro cytotoxic activity was examined by cell proliferation assay. Date sap syrups displayed strong antioxidant activities which are correlated 5HMF and 2F contents. In addition, concentration at 100 °C, unlike ultrafiltration process, enhanced significantly the antioxidant activities sap syrups and total phenolic contents. The antimicrobial activities showed marked activity against S. enterica, P. aeruginosa, S. aureus, L. monocytogenes with an inhibition zone of 21, 34, 27 and 34 mm respectively. Cytotoxicity assays showed that sap syrups can inhibit the proliferation of HeLa cell lines at high concentration.

Technological properties of milk gels produced by chymosin and wild cardoon rennet optimized by response surface methodology.

The aim of this paper was to optimize extraction conditions of C. cardunculus rennet by response surface methodology, in order to maximize its milk-clotting activity (MCA). The second objective was to examine the effect of different amounts of the optimized extract and the type of milk, on technological characteristics of the obtained gels. Results of the central composite design showed that the optimum extraction conditions, corresponding to maximum MCA (9.550CAU/mL), were selected as follows: Grinding time 30s, pH 3, extraction time 50min and solid to liquid ratio 15g/100mL. According to technological properties, it can be concluded that C. cardunculus extract exhibited an excellent efficiency on raw milk, in term of dynamic moduli and gel firmness, as compared to chymosin. A good gelation time and WHC were also obtained. Consequently, the optimized C. cardunculus rennet has the potential to be employed as an efficient milk-clotting agent.

The addition effect of Tunisian date seed fibers on the quality of chocolate spreads.

Novel chocolate spreads were enriched by soluble and insoluble dietary fibers from Tunisian Deglet Nour date seeds at 1, 2, 3, 4, and 5% levels in the conventional chocolate spread. Defatted Deglet Nour date seeds, date seed soluble fiber concentrate (DSSFC) and date seed insoluble fiber concentrate (DSIFC) were characterized by high levels of dietary fibers (80-90%). Chocolate spread enriched with 5% of DSSFC presented the highest oil binding capacity (304.62%) compared to the control (102%). Whatever the DSIFC and DSSFC incorporation levels, no significant difference was recorded between the firmness, chewiness, and adhesiveness of prepared chocolate spreads compared to the control (p < .05). Sensory evaluation revealed that all prepared chocolate spreads enriched by DSIFC and DSSFC were accepted by panelists. These results indicated the value of date seeds as new source of dietary fibers to develop chocolate spread and could also improve health benefits and functional properties. PARACTICAL APPLICATION: Tunisia is considered to be one of the dates-producing countries. The mean annual yield of date fruits is about 200,000 tons. From this, around 20,000 tons of date seeds could be collected. This by-product of date processing industries could be regarded as an excellent source of dietary fiber with interesting technological functionality and many beneficial effects on human health. Then, date seeds could present a value addition by extraction and use of date seed fiber concentrate in chocolate spread formulation.

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.