Effect of ultrasound and green solvents addition on the oil extraction efficiency from rapeseed flakes.

The current procedure of rapeseed oil extraction is based on a first extraction step by pressing followed by a second extraction step with hexane. This solvent being toxic for the users, the consumers and the environment, its use could be forbidden within the coming years. Stimulated by a stringent regulation, the research activity for the replacement of toxic solvents shows a significant development. The aim of this study was to select alternative solvent to hexane such as ethanol or isopropanol, and, to adjust the oil extraction process by developing an ultrasound assisted method. The objective was to reach a comparable efficiency but also to enhance the oil quality. When applied to isopropanol, the ultrasound assisted extraction method has shown promising results, and comparable to those obtained with hexane (oil yield of 80% for hexane and 79% for isopropanol at optimum extraction conditions (20min of ultrasound pretreatment followed by 2h of additional solid/liquid extraction)). Conversely, in studied conditions, ethanol did not seem to be an appropriate alternative solvent to hexane as the extraction yields obtained by using this solvent were quite low.

Impact of ultrasounds and high voltage electrical discharges on physico-chemical properties of rapeseed straw's lignin and pulps.

In this study, ultrasound (US) and high voltage electrical discharges (HVED) were combined with chemical treatments (soda or organosolv) for rapeseed straw delignification. Delignification was improved by both physical pretreatments. US increased the extractability of hemicelluloses and HVED induced a partial degradation of cellulose. Best synergies were observed for HVED-soda and US-organosolv treatments. The obtained lignin fractions were characterized with 13C NMR and 2D 1H-13C HSQC. It was observed that the physical treatments affected the syringyl/guaiacyl (S/G) ratios. The values of S/G were ≈1.19, 1.31 and 1.75 for organosolv, HVED-organosolv and US-organosolv processes, suggesting recondensation reactions. The lignin fractions obtained from HVED-organosolv treatment contained less quantity of p-coumaric acid and ferulic acid as compared to those extracted by US-organosolv. Thermogravimetric analysis (TGA) revealed a better heat resistance of physically extracted lignins as compared to the control. The enzymatic digestibility increased by 24.92% when applying HVED to mild organosolv treatment.

Pulsed electric field pretreatment of rapeseed green biomass (stems) to enhance pressing and extractives recovery.

The objective of this study was to investigate the effects of pulsed electric field (PEF) pretreatment on the valorization of extractives (proteins and polyphenols) from rapeseed green biomass (stems) by pressing. The effect of pressure, electric field strength and pulse number on the juice expression yield, total polyphenols and total proteins content in the expressed juices were studied. Experiments conducted under optimal conditions (E = 8 kV/cm, tPEF = 2 ms, P = 10 bar) permitted to increase the juice expressed yield from 34% to 81%. Significant increases in total polyphenols content (0.48 vs. 0.10 g GAE/100g DM), in total proteins content (0.14 vs. 0.07 g BSA/100g DM) and in consolidation coefficient (9.0 × 10(-8) vs. 2.2 × 10(-8)m(2)/s) were also observed after PEF pretreatment. The recovered press cake was well dehydrated with an increase of dry matter content from 8.8% to 53.0%.

Impact of pulsed-electric field and high-voltage electrical discharges on red wine microbial stabilization and quality characteristics.

AIMS: In this study, pulsed-electric fields (PEF) and high-voltage electrical discharges (HVED) are proposed as new techniques for the microbial stabilization of red wines before bottling. The efficiency of the treatment was then evaluated. METHODS AND RESULTS: PEF and HVED-treatments have been applied to wine for the inactivation of Oenococcus oeni CRBO 9304, O. oeni CRBO 0608, Pediococcus parvulus CRBO 2.6 and Brettanomyces bruxellensis CB28. Different treatment times (1, 2, 4, 6, 8 and 10 ms) were used at 20 kV cm(-1) for the PEF treatments and at 40 kV for the HVED treatments, which correspond to applied energies from 80 to 800 kJ l(-1) . The effects of the treatments on the microbial inactivation rate and on various characteristics of red wines (phenolic composition, chromatic characteristics and physico-chemical parameters) were measured. CONCLUSIONS: The application of PEF or HVED treatments on red wine allowed the inactivation of alteration yeasts (B. bruxellensis CB28) and bacteria (O. oeni CRBO 9304, O. oeni CRBO 0608 and P. parvulus CRBO 2.6). The electric discharges at 40 kV were less effective than the PEF even after 10 ms of treatments. Indeed, 4 ms of PEF treatment at 20 kV cm(-1) were sufficient to inactivate all micro-organisms present in the wines. Also, the use of PEF had no negative impact on the composition of wines compared to the HVED treatments. Contrary to PEF, the phenolics compounds were degraded after the HVED treatment and the physico-chemical composition of wine were modified with HVED. SIGNIFICANCE AND IMPACT OF THE STUDY: PEF technology seems to be an interesting alternative to stabilize microbiologically wines before bottling and without modifying their composition. This process offers many advantages for winemakers: no chemical inputs, low energy consumption (320 kJ l(-1) ), fast (treatment time of 4 ms) and athermal (ΔT ≈ 10°C).

Ultrasound-assisted green solvent extraction of high-added value compounds from microalgae Nannochloropsis spp.

The aim of this work was to investigate ultrasound (US)-assisted green solvent extraction of valuable compounds from the microalgae Nannochloropsis spp. Individual green solvents (water, ethanol (EtOH), dimethyl sulfoxide (DMSO)) and binary mixture of solvents (water-DMSO and water-EtOH) were used for the extraction procedures. Maximum total phenolic compounds yield (Yp ≈ 0.33) was obtained after US pre-treatment (W=400 W, 15 min), being almost 5-folds higher compared to that found for the untreated samples and aqueous extraction (Yp ≈ 0.06). The highest yield of total chlorophylls (Yc ≈ 0.043) was obtained after US (W=400 W, 7.5 min), being more than 9-folds higher than those obtained for the untreated samples and aqueous extraction (Yc ≈ 0.004). The recovery efficiency decreased as DMSO>EtOH>H2O. The optimal conditions to recover phenolic compounds and chlorophylls from microalgae were obtained after US pre-treatment (400 W, 5 min), binary mixtures of solvents (water-DMSO and water-EtOH) at 25-30%, and microalgae concentration of 10%.

Selective extraction from microalgae Nannochloropsis sp. using different methods of cell disruption.

This work studies the extraction of intracellular components from microalgae Nannochloropsis sp. with application of different cell disruption techniques, including pulsed electric field (PEF) (20kV/cm, 1-4ms, 13.3-53.1kJ/kg), high voltage electrical discharge (HVED) (40kV/cm, 1-4ms, 13.3-53.1kJ/kg), ultrasonication (USN) (200W, 1-8min, 12-96kJ/kg), and high pressure homogenization (HPH) (150MPa, 1-10 passes, 150-1500kJ/kg). The data evidence that electrically based disruption techniques (PEF and HVED) allowed selective extraction of water soluble ionic components and microelements, small molecular weight organic compounds and water soluble proteins. Microscopic and sedimentation stability analyses have shown that microalgae cells in HVED-treated suspension were noticeably agglomerated and could be easily settled in centrifuge. The electrically based disruption techniques were ineffective for delivery of pigments (e.g., chlorophylls or carotenoids) and their extraction required subsequent application of more potent disruption techniques. The obtained data have shown that HPH disruption technique was the most effective; however, this mode required the highest power consumption.