Abdessalem Mrabet

Physico-chemical properties and DPPH-ABTS scavenging activity of some local pomegranate (Punica granatum) ecotypes

Peels and fresh pomegranate extracts were used in the present study for the determination of the physic-chemical properties and DPPH-ABTS scavenging activities. Total sugars of juice are fructose (ca. 7 g/100 ml) and glucose (ca. 8 g/100 ml). Contents of soluble proteins in juice extracts are about 7 g/l (Bradford assays) and 22% (Kjeldhal assays) from dry pulp. Minerals in peel and juice are respectively 9.43±0.93 and 9.46±1.05 mg/100 ml for posphorus and 210.86±10.70 and 271.94±60.59 mg/100 g for potassium. The sodium contents are nearly 7 mg/100 ml in both peel and juice. Highly antioxidant contents in peels were confirmed. Free radical scavenging is about 3.58±0.38 µg/ml in peel. The antioxidant capacity value determined by ABTS was 7.364±0.403 mM Trolox equivalent antioxidant capacity/100 g dry weight. These findings implied that bio-active compounds from the peel might be potential resources for the development of antioxidant function dietary food.

Simple phenolic composition, flavonoid contents and antioxidant capacities in water-methanol extracts of Tunisian common date cultivars (Phoenixdactylifera L.)

The purpose of this study was to determine and compare the phenolic acid composition, flavonoid content and antioxidant activity of fruits from common date cultivars. The simple phenolic content ranged from 15.73 (Mermella variety) to 54.66 mg/100 g fresh weight (Korkobbi variety). Korkobbi had also the highest content of total flavonoids (54.46 quercetin equivalents/100 g fresh weight). The percentage of inhibition can reach 83% in the lipoperoxyl radical of the Korkobbi variety, while it was about 95% with the Rotbi variety for OH·. The Trolox equivalent antioxidant capacity value provided a ranking in decreasing order at 6 min: Korkobbi > Bouhattam > Baht = Smiti > Bekreri = Garn ghzal > Mermilla = Kenta > Nefzaoui = Rotbi. It seems that the highest level of flavonoids in the Korkobbi variety was principally responsible for the highest antiradical efficiency of this cultivar.

Dietary fiber from Tunisian common date cultivars (Phoenix dactylifera L.): chemical composition, functional properties, and antioxidant capacity.

The dietary fibers (DF) of 10 date varieties from Tunisian oases have been investigated. Further knowledge on the content, composition, and technological applications of those fibers could support their genetic variability and promote the socioeconomical development of growing areas. The composition, water- and oil-holding capacities, solubility, and antiradical activity have been determined. The DF content ranged from 4.7% (Matteta, Rochdi) to >7% (Deglé Nour, Garen Gaze, Smeti). Composition varied significantly among cultivars, and the results evidenced that uronic acids and lignin determine to a great extent the organoleptic quality of dates. Many of the varieties that have been studied (Garen Gaze, Matteta, Kenta, Rochdi, Mermella, Korkobbi, Eguwa) were selected because of great interest from technological and functional points of view. Among their physicochemical characteristics, these samples presented water- and oil-holding capacities of higher than 17 and 4 mL/g fiber, respectively, which make them suitable for use as additives in fiber-enriched foods. Also, DF of Garen Gaze, Smeti, Mermella, and Eguwa had a high antiradical capacity (>230 Trolox equiv/kg fiber). It was concluded that some of these varieties could be grown as potential sources of DF, which could be included in the formulation of fiber- and antioxidant-enriched foods.

Microbiological and chemical characterisations of organic and conventional date pastes (Phoenix dactylifera L.) from Tunisia

Chemical and microbiological properties of organic and conventional date pastes produced from the Deglet Nour cultivar were investigated. Significant differences were observed in water content, sugar profiles, and pH among the date pastes. The low moisture and the high acidity of organic date paste were two important positive attributes for its storage and potential manufacturing uses. Before pasteurisation, moulds CFU’s of the organic paste was significantly (P <0.01) lower than those of the conventional one but no significant differences were observed for yeasts, coliforms and the total aerobic flora among the two date pastes. Considerable interest has developed on the preservation of conventional date paste by the use of natural additives such asJuniperus phoenicea and olive oil (conditioned paste). At a given mixture ofJuniperus and olive oil and after pasteurisation, mould CFU’s were reduced by 95% (P <0.01) whereas the reduction was only 84% for the yeast populations, after 45 days at 25 °C.