The objective of this study was to assess the impact of pulsed electric field (PEF) treatment on the extraction of polyphenolics and antioxidant activity from downgraded date palm fruits. The PEF pretreatments (frequency: 30 Hz, time: 50 μs, pulse number: 240, the electric field strengths were found to be 1, 2, and 2.5 kV.cm⁻¹, and methanol (50%) and temperatures (20, 40, 50 °C)) were optimized and applied before extraction to produce an extract of date fruits with a high content of bioactive compounds. The extracts obtained immediately after pretreatments were analyzed for total polyphenolic content, antioxidant activity, and phenolic profiles. The results revealed that the PEF-assisted extracts at 2.5 kV.cm⁻¹ at T₅₀ °C exhibited higher polyphenol content (+27%) and antioxidant activity (+31%) and notably improved phenolic profiles compared to untreated extracts. PEF treatment processing significantly enhanced the bioactive components and antioxidant activities of date fruits over time, regardless of the treatment applied and the extraction’s temperature. Hence, the application of PEF combined with thermal processing can be an appropriate alternative treatment for a better extractability of bioactive compounds from fruit of dates and food byproducts. These biomolecules could be consumed as new food technology, incorporated as food additives, and nutraceuticals products.

The impact of hygienization as mild thermal pretreatment on the methane production of various organic wastes was investigated, including digestate issued from hydrolysis tank, thickened sludge from a municipal wastewater treatment plant (MWWTP sludge) and from a mixed domestic-industrial wastewater treatment plant (D-I WWTP sludge), sludge from a meat-processing plant (MP sludge), sieving rejection from a pork slaughterhouse, pork liver, cattle slurry, cattle scraping slurry and date seeds. They were thermally pretreated at 70 °C for one hour and subsequently put into AD digesters incubated at 37 °C for individual methane potential test. The modified Gompertz model was employed to evaluate the kinetic parameters of methane production curves (R² = 0.944–0.999). The results were compared with the untreated samples. Significant enhancement of methane potentials induced by thermal treatment (p < 0.05) was observed when it comes to the pork liver (+8.6%), the slaughterhouse sieving rejection (+11.1%), the thickened MWWTP sludge (+12.5%) and the digestate issued from hydrolysis tank (+18.0%). The maximum methane production rates of the 4 substrates mentioned above were increased by thermal pretreatment as well (from 13.5% to 64%, p < 0.05). The lag time of the methane production was shortened for the digestate from hydrolysis tank and the MWWTP sludge (by 48.6% and 62.2% respectively, p < 0.05). No significant enhancement was obtained for the cattle slurry, the cattle scraping slurry and the D-I WWTP sludge. Additionally, the maximum methane production rate and the methane potential were reduced by thermal pretreatment for the MP sludge and the date seeds respectively (p < 0.05). In this paper, possible mechanisms were discussed to explain the different methane production behaviors of substrates after the mild thermal pretreatment.

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Large amounts of secondary date waste (pulp and seeds) are produced and discarded in Tunisia without proper valorisation methods. To study the possibility of valorising different varieties of Tunisian date waste (pulp and seeds) via anaerobic digestion, batch biochemical methane potential (BMP) tests were carried out under mesophilic temperature. The bio-methane production curves were fitted to the model of modified Gompertz in search of the kinetic parameters. The bio-chemical characterisation of the substrates from different varieties (total and volatile solids, COD and contents in carbohydrates, proteins, lipids, polyphenols) was realised. Principal component analysis (PCA) was used to investigate the correlations between the model parameters and biochemical variables. Results show that the biochemical compositions of date pulp and seeds strongly depend on the varieties. The BMP are in the range of 0.295–0.345 and 0.267–0.327 Nm³ CH₄·kg COD⁻¹ for pulp and seeds respectively, resulting from the significant biochemical variance among the varieties. The BMP of date seeds was significantly correlated with their VS/TS ratio, carbohydrate and protein contents (p < 0.05). For the pulp, significant correlation was found between BMP, carbohydrate and lipid contents. PCA shows that certain varieties (like pulp and seeds of Deglet Nour and seeds of Bejou) are most suitable for being valorised by anaerobic digestion. The most suitable date varieties for this innovative approach were revealed. This research provided useful knowledge for bioconversion of waste date pulp and seeds to biomass energy. GRAPHICAL ABSTRACT

The effects of irrigation with saline water were studied on barley plants cultivated under arid conditions at the Institute of Arid Regions located in the South East of Tunisia. Two barley accessions (Karkeni and Bengardeni) and three regimes of irrigation as a function of the cultural evapotranspiration ETc (T0: 100% ETc, T1: 75% ETc and T2: 50% ETc) were used. Several parameters – gas exchange (A, E and gs), total flavonoid contents (TFC), total phenolic contents (TPC), phenolic compounds, antioxidant activity (DPPH and ABTS) and grain yield (GY) – were used to assess the effects of the studied factors on barley plants. Gas exchange parameters (A, E and gs) vary significantly between treatments. Salinity stress had no significant effect on TPC and TFC. Phenolic compounds varied significantly between treatments and accessions. In addition, their antioxidant activity based on DPPH and ABTS scavenging assays increased and are more important in Karkeni than Bengardeni under soil salinity. In addition, soil salinity decreased yield and yield components. Karkeni was more productive than Bengardeni.