The twin-screw extrusion technology, an original and powerful solution for the biorefinery of sunflower whole plant

The objective of this study was to evaluate the feasibility of an aqueous process for the biorefinery of sunflower whole plant using a twin-screw extruder. Aqueous extraction of oil was chosen as an environment-friendly alternative to the solvent extraction. The extruder was used to carry out three essential unit operations: grinding, liquid/solid extraction, and liquid/solid separation. Wringing out the mixing was effective. However, drying of the cake meal was not optimal. Lixiviation of cotyledon cells was also incomplete. Extraction efficiency depended on operating conditions: screw rotation speed, and input flow rates of whole plant and water. In the best conditions, oil yield was 57%. Residual oil content in the cake meal was 14%. These conditions leaded to the co-extraction of proteins, pectins, and hemicelluloses. The corresponding protein yield was 44%. Oil was extracted in the form of two oil-in-water emulsions. These hydrophobic phases were stabilized by phospholipids and proteins at interface. An aqueous extract containing part of the water-soluble constituents, mainly proteins and pectins, was also generated. As a mixture of fibers and proteins, the cake meal was molded by thermo-pressing. Panels produced had interesting mechanical properties in bending. The obtained fractions may have applications as bases for industrial products

Thermo-mechanical behaviour of the raffinate resulting from the aqueous extraction of sunflower whole plant in twin-screw extruder: manufacturing of biodegradable agromaterials by thermo-pressing

Biorefinery of sunflower whole plant can be realized using a twin-screw extruder. Thermo-mechanical fractionation and aqueous extraction are conducted simultaneously. A filter section is outfitted along the barrel to collect continuously an extract and a raffinate (cake meal). Oil yield obtained is 53%. Proteins are partly extracted at the same time, just as pectins and hemicelluloses. Protein yield is 46%. Cake meal is relatively moist (66% for the moisture content). It is first dried to make easier its conservation. It is largely composed of lignocellulosic fibres (59% of the dry matter) from depithed stalk. Lipid content is 13% of the dry matter or 35% of the oil in whole plant. Protein content is 7% of the dry matter or 45% of the proteins in whole plant. DSC measurements indicate that denaturation of proteins is almost complete in the cake meal. DMTA spectrum of its milled powder reveals a significant peak at high temperature (between 175 and 200°C). As already observed with industrial sunflower cake meal, it can be associated with the glass transition of proteins. As a mixture of fibres and proteins, the cake meal can be considered as a natural composite. It is successfully processed into biodegradable and value-added agromaterials by thermo-pressing. As for DMTA analysis, the glass transition of proteins in the cake meal is also observed with PVT analysis at around 180°C. It makes easier the choice of the best thermo-pressing conditions to produce panels with higher mechanical properties in bending. These properties increase simultaneously with temperature, pressure and time chosen for molding operation. The highest flexural strength at break (11.5 MPa) and the highest elastic modulus (2.22 GPa) are obtained for the next molding conditions: 200°C and 320 kgf/cm2 during 60 s. Drop angle measurements show that the corresponding panel is also the most resistant to water. No significant transition is observed inside this panel above 0°C and until 200°C with DMTA analysis. Proteins ensure the agromaterial cohesion without any phase change in this temperature range, and fibres entanglement also acts like reinforcement. This panel could be used as inter-layer sheets for pallets or for the manufacturing of biodegradable containers (composters, crates for vegetable gardening) by assembly of panels

Thermo-pressing of cake meal from sunflower whole plant, one only operation for two actions : expression of residual oil and molding of biodegradable agromaterials

The starting material used in this study was a cake generated during thermo-mechanical fractionation of sunflower (Helianthus annuus L.) whole plant in a Clextral BC 45 (France) twin-screw extruder. It was slightly deoiled (17.6% dry matter for residual oil content), leading to an oil extraction yield of 46.1% (yield based on the residual oil content in cake). As it was a mixture of fibers and proteins, it could be considered as a natural composite that was processed successfully into fiberboards by thermo-pressing. This study aimed to evaluate the influence of thermo-pressing conditions on oil expression yield during molding and on flexural properties of fiberboards manufactured from this cake. An experimental design with three variables was realized: from 250 to 500 kgf/cm² for pressure applied (in 5 levels), from 60 to 300 s for molding time (in 7 levels), and from 600 to 1200 mg/cm² for cake quantity (in 3 levels). Temperature of the aluminium mold positioned between the two plates of the heated hydraulic press (PEI, France) with 400 tons capacity was 200°C. All fiberboards were cohesive. As an internal binder, proteins ensured the agromaterial cohesion, and fibers entanglement also acted like reinforcement. Thermo-pressing was not only a molding operation. It also consisted in increasing the oil extraction efficiency. Oil expression yield during molding increased with the increase of pressure applied, and especially with the increase of molding time. At the same time, it was not so much influenced by the modification of cake quantity. Highest oil expression yield was 58.8% in proportion to the oil that the cake contained, leading to a total oil yield (oil extracted by water in twin-screw extruder, and oil expressed during molding) of 77.8% in proportion to the oil that the sunflower whole plant contained. It was associated with the next thermo-pressing conditions: 469 kgf/cm² for pressure applied, 300 s for molding time, and 697 mg/cm² for cake quantity. Flexural properties of the corresponding fiberboard were 8.1 MPa for flexural strength at break, and 1778 MPa for elastic modulus. Its thickness was 5.40 mm, leading to a mean apparent density of 1.25. Such flexural strength at break was a bit lower (-25%) than the one of the most resistant fiberboard (10.8 MPa), manufactured from the next thermo-pressing conditions: 250 kgf/cm² for pressure applied, 300 s for molding time, and 807 mg/cm² for cake quantity. For such conditions, oil expression yield was 48.0% in proportion to the oil that the cake contained, leading to a total oil yield close (-8%) to the highest yield obtained (71.9% in proportion to the oil that the sunflower whole plant contained instead of 77.8%). Thermo-pressing of cake from sunflower whole plant led to two actions in a single step: the expression of part of residual oil in cake that contributed to the improvement of the oil extraction efficiency, and the molding of biodegradable fiberboards. Their flexural properties were promising. Moreover, because residual oil content in fiberboards was at least 8.0% dry matter, they were not too water-sensitive (i.e. more durable than other thermo-pressed agromaterials). Such fiberboards were value-added agromaterials that may have direct industrial applications. Indeed, they would be potentially usable as inter-layer sheets for pallets, for the manufacturing of biodegradable containers (composters, crates for vegetable gardening), or for their heat insulation properties in building trade

Aqueous extraction of oleic sunflower oil from whole plant by twin-screw extruder: feasibility study, influence of screw configuration and operating conditions

Aqueous extraction process using water alone as medium is an alternative to the solvent oil extraction process from oilseeds. It enables simultaneous recovery of oil and protein. The implementation of a co-rotating twin-screw extruder allows the aqueous extraction of oleic sunflower oil from whole plant. Screw configuration, screw rotation speed and whole plant input flow rate affect directly the efficiency of liquid/solid separation. Wringing out the mixing is possible because of the natural abundance of fibers in stalk. However, the compression of the vegetable matter is imperfect to allow an expedient separation of the two phases. Lixiviation of oilseeds is also incomplete. The highest oil extraction yield obtained is 64.9% and residual oil content of fibrous cake meal is always higher than 13.1%. Hydrophobic phase produced is an oil-in-water emulsion. Its stability is ensured by the presence at interface of natural surface-active agents also extracted during the process, phospholipids and proteins. Hydrophilic extract contains soluble proteins but also hemicelluloses and pectins. Originated respectively from stalk, pith and head, these two molecular families also have some interesting surface-active properties. So the aqueous extraction produces a second hydrophobic phase when it is realised from whole plant. This water-in-oil-in-water emulsion is denser than aqueous phase. Its stability is ensured by the presence at interface of phospholipids, proteins, hemicelluloses and pectins. Fibrous cake meal is richer in fibers (up to 45.6% of cellulose and lignins against 33.1% in the whole plant) and other insoluble components. It is possible to upgrade it by thermopressing in such a way as to manufacture sound insulation panels

New process for the biorefinery of sunflower whole plant by thermo-mechanical fractionation and aqueous extraction in a twin-screw extruder

Fractionation of sunflower whole plant is carried out with water in a twin-screw extruder. An extract and a raffinate are produced in a single step. Oil extraction yield is 55%. Lipids are extracted in the form of two oil-in-water emulsions: the higher hydrophobic phase and the lower one. Stability of both hydrophobic phases is ensured by the presence at interface of surface-active agents co-extracted: phospholipids and proteins. Pectins and non pectic sugars complete the dry matter of the lower hydrophobic phase. Hydrophobic phases may have applications for non food uses: biolubricants market, transport of active principles (odours, colours, bactericides, antifungals), and treatment of hydrophilic surfaces. They can be also used for oil production because their demulsification with ethanol is efficient. Oil recovery produces also a precipitate containing proteins with tensioactive properties. The extract contains also a hydrophilic phase (aqueous phase). This largest phase is an extract of the soluble constituents from whole plant: proteins from kernel, pectins from pith and head, and hemicelluloses from stalk. Valorization of hydrophilic phase is difficult because it is much diluted. Nevertheless, it would be potentially recyclable for aqueous extraction. It would be also possible to use it for the production of proteins with surface-active properties and pectins. The raffinate (cake meal) is rich in fibres and proteins with thermoplastic properties. It would be suitable for use in animal feeds and for energy production. It is also a natural composite, and it can be manufactured into biodegradable agromaterials by compression moulding. Panels can be used as inter-layer sheets for pallets or for the manufacturing of containers

Aqueous extraction of oil from sunflower seeds in batch reactor: reorganization of the mixing in three formulated fractions

Aqueous extraction process is an alternative to the solvent oil extraction process from oilseeds. It enables simultaneous recovery of oil and protein. Water extraction of sunflower oil is carried out with a mixer (model Waring Blendor, USA) as batch reactor (seeds/water: 15/85). This only apparatus carries out two essential unit operations: conditioning and grinding of sunflower seeds and liquid/solid extraction. However, lixiviation of kernels is incomplete. After five minutes of extraction, the mixture reorganizes by centrifugation in three formulated fractions: the insoluble phase (31.1% of the mixture), the hydrophilic phase (61.4% of the mixture) and the hydrophobic phase (7.5% of the mixture). Oil extraction yield obtained is 46.6%. Residual oil content of raffinate is 39.2% instead of 49.7% in sunflower seeds. Aqueous extraction process also results in an impoverishment of oil cake into water-soluble substances contained initially in kernels: proteins and minerals. Raffinate is on the contrary richer in insoluble proteins and fibers (26.1% for cellulose and lignins instead of 17.1% in sunflower seeds). An additional stage of extraction would allow a better oil impoverishment of the insoluble phase before its possible use for animal feeding. It would be also possible to upgrade it by thermopressing. Panels obtained have mechanical characteristics comparable with those of other experimental materials. Hydrophilic phase is the dominating fraction. It contains proteins (31.8% of dry residue), minerals (8.2% of dry residue) and hemicelluloses. Its oil content means that centrifugation does not allow an expedient separation between hydrophilic phase and hydrophobic phase. After concentration of organic substances by ultrafiltration, it is possible to collect proteins by isoelectric precipitation. These water-soluble proteins can be used for their surface-active properties. Hydrophobic phase is an oil-in-water emulsion. It is lighter than hydrophilic phase (0.94 for its density). Lipids represent 83.8% of its dry residue. Its stability is ensured by the presence at interface of natural surface-active agents also extracted during the process, phospholipids and proteins. Demulsification is possible by alcoholic extraction. It enables the edible oil isolation. Oil consumption is possible for human feeding but also for non food uses like biolubricants market. Hydrophobic phase can also be used without any modification for the manufacture of paintings and cosmetics or for the treatment of surfaces with hydrophilic matter

Sweet Clovers, a Source of Fibers Adapted for Growth on Wet and Saline Soils

Sweet clovers are legumes able to grow on most soils, and two sweet clover species, Melilotus albus and Melilotus officinalis have been introduced and are now cultivated on estuary land. We characterized the composition and morphology of sweet clover stems collected after the seeds had reached maturity. We also carried out histochemical analyses on transverse sections. The two species had similar morphological structures, which two fiber fractions: flexible long fibers and stiff, dense shives, accounting for about 12% and 88% of stem dry matter, respectively. Histological analysis revealed the presence of bundles of highly cellulosic bast fibers (lignocellulosic material: 71–78% of dry matter). The shives are a natural mesoporous material composed of 85–90% lignocellulosic fibers. Both fiber fractions displayed good thermal resistance to temperatures up to 225°C and a moderate affinity for water. These two types of fibers are similar to those of flax and hemp, suggesting their possible use for the same types of applications. Sweet clovers therefore constitute a new source of fibers that can be cultivated on wet and saline soils not otherwise suitable for agriculture

The thermo-mechano-chemical fractionation of sunflower whole plant in twin-screw extruder, an opportunity for its biorefinery

Biorefinery of sunflower whole plant is conducted according to an aqueous process using a twin-screw extruder. Aqueous extraction of oil is looked upon as an environmentally cleaner alternative technology to solvent extraction. Twin-screw extruder carries out three unit operations continuously: conditioning and grinding of whole plant, liquid/solid extraction and liquid/solid separation. Extraction efficiency depends on screw speed, and input flow rates of whole plant and water. In best conditions, oil yield is 57%, and residual oil content in cake meal is 14%. These conditions lead to the co-extraction of proteins, pectins and hemicelluloses. Oil is extracted in the form of two oil-in-water emulsions stabilized by phospholipids and proteins at interface. They could be used as co-emulsifiers for creams production in cosmetic industry. An aqueous extract containing part of the water-soluble constituents from whole plant, mainly proteins and pectins, is also generated. It can be recycled to the process. As a mixture of fibers and proteins, the cake meal can be moulded by thermo-pressing. Denser fiberboards have promising mechanical properties in bending. They could be used in furniture industry. Fiberboards with the lowest densities are more fragile but they could be used for their heat insulation properties in building industry

The aqueous extraction of sunflower oil from whole plant in twin-screw extruder, a first step for the manufacturing of biodegradable agromaterials by thermo-pressing

Twin-screw extrusion is an original solution for the biorefinery of sunflower whole plant according to an aqueous extraction process. In best operating conditions, oil yield is 57% and residual oil content in the cake meal is 14%. Oil is extracted in the form of two oil-in-water emulsions stabilized by phospholipids and proteins at interface. The cake meal would be suitable for use in animal feeds and for energy production in pellets burning furnaces. As a mixture of fibers and proteins, it is also considered as a natural composite. It can be processed into biodegradable agromaterials by thermo-pressing. During molding, part of residual oil is expressed (until 41% of oil from whole plant), leading to the increase of the total oil extraction yield (aqueous extraction in twin-screw extruder and expression during thermo-pressing): until 81% of oil from whole plant. Panels have promising mechanical properties in bending (until 12 MPa for stress at break). They are usable as inter-layer sheets for pallets, for their sound and heat insulation properties or for the manufacturing of containers by assembly of panels. Their hydrophobic character (8% for residual oil content in the panels) makes them resistant to water

The properties of cellulose insulation applied via the wet spray process

Cellulose fibre insulation is a sustainable thermal insulation material made out of recycled paper. It can be installed in open walled cavities using the wet spray method. The isotherm of loose cellulose insulation fibres was determined using dynamic vapour sorption to study their relationship with water. The types of water within the fibres, known as bound and unbound water was studied via a differential scanning calorimetry method. Wet spray cellulose samples were produced with varying water content and subjected to compression, and thermal conductivity testing. Results showed that density, modulus of elasticity, and thermal conductivity all increased with water dosage. The increase in these properties was higher when the material was sprayed with water than when it was dry compacted. These are factors which need to be considered for when applying wet-spray cellulose fibre insulation, in order to ensure the properties of the material are consisten