How it works: Oilseed extraction can be done by mechanical extraction by pressing or by chemical extraction by dissolving the oil in a solvent. Cold-pressing is the simplest way to obtain these oils, but not the most efficient as the yields are relatively limited, especially when working with low-oil-content products. Pressing the seeds after cooking pretreatment obtains quantitatively higher-yield extraction process. In terms of quality, cold-pressing is the preferred method for virgin oils—virgin means they are consumed straight, without further refining—whereas precooking before pressing affords oils that are richer in micronutrients (vitamin E, phenolics, phospholipids). Solvent extraction is a technically more complex process technique that is applied to low-oil-content feedstocks as it is the only way to get satisfactory yields.
Service characteristics: We are equipped to offer pressed-extraction capacity, but most of the contracts we deliver are performed using solvent extraction processes.
These contracts generally require a custom engineering phase during which our teams will devise a protocol set to deliver the requirement process performances.
The main challenges are posed by:
- oilseeds that are not readily extractable, requiring specific preparation methods,
- fragile oils requiring special measures to protect compounds-of-interest against degradation,
- issues tied to undesirable compounds that the process needs to not extract or eliminate.
Our competitive strengths: The fact that we boast a wide range of equipment readily utilizable for pre-extraction preparation means we generally manage to find solutions to the problems we are asked to tackle.
Specific demands of percolation extraction: How well the extractor works will depend on how porous the extractate is. The percolation extractor does not work for powders and fine particulates, yet it is common knowledge that reducing the size of the solid fraction will improve the extractability of the oil.
There are ways and means to agglomerate dry flowables to lend them the requisite porosity, and some of them are in our skillset (granulation, pressing, extrusion, flaking).
How it works: Refining operations serve to purify crude oils, i.e. rid them of undesirable compounds. The list of undesirable compounds is long, and includes:
- Free fatty acids split from triglycerides by hydrolysis. Acidity in oils is a factor of poor conservation, as it promotes rancidification.
- Precursors of oxidation. Unsaturated oils are oxidation-vulnerable, as the oxygen attacks the double bonds within the fatty acid chains to form ‘epoxy’ groups, which are unstable and promote subsequent formation of secondary-stage oxidation compounds that generate rancid flavour.
- Pigments (carotenes, chlorophyll and its derivatives, polyphenols). Some of these pigments have pro-oxidant activity, and the colour change they bring poses appearance-quality problems, especially when they turn brown during deodorizing.
- Undesirable flavour compounds. Fatty acids are the main vectors of aroma. Crude oils generally reflect the oilseeds they came from, bringing flavour properties that consumers do not want (rapeseed oil that smells cabbage-like, soybean oil that smells runner bean-like, and so on.)
- Contaminants: exogenous substances not intentionally added and whose presence is considered undesirable. The equally long list of contaminants includes pesticide residues (chiefly of insecticides, like deltamethrin, used during commodity storage), polycyclic aromatic hydrocarbons (PAHs), phthalates from plastics, mycotoxins. Some of these contaminants can form during refining, like trans-fatty acids (trans-configuration isomers, mainly affecting polyunsaturated fatty acids), MCPD and glycidol esters. To find out more: OCL paper on contaminants.
Refining can be done by two methods: physical or chemical. Physical refining eliminates free fatty acids in the deodorizer under more severe temperature conditions than for chemical refining. Fragile oils—where fragile means rich in polyunsaturated fatty acids—are less amenable to physical refining.
What is dubbed ‘chemical’ refining consists in reacting a strong base with the free fatty acids to form a small amount of soap that can then be degummed by centrifugal separation. The base has to be dose-adjusted to acidity so that the triglycerides do not get saponified. This process if preceded by acid conditioning that serves to break down the complexes that form phosphatidic acid with the divalent Ca²+ and Mg²+ cations so that these compounds can recover amphiphilic properties making them removable as micelles. This neutralizing step is followed by water-washing (to remove surplus caustic) then drying. The next operation is bleaching, which consists in adding a small amount of active or inactive bleaching clay alone or in combination with special adsorbents like activated charcoal or synthetic silica that trap and hold the pigments and contaminants and are then removed by filtration. Oils containing waxy compounds may want to be treated by winterizing, an operation that crystallizes the waxes, making them removable by filtration. The waxes are not a health hazard, but they can cloud the oil during storage. Dewaxing prevents clouding, which may be a turn-off for undiscerning consumers. The last step in the refining process is deodorizing, where the oil is heated under high vacuum (2–5 mbar absolute pressure) up to temperatures of 160 to 270°C, augmented with direct steam injection designed to vaporize the recalcitrant volatile flavour impurities along with a number of contaminants. Physical refining will aim for temperatures over 240°C with vacuums under 2 mbar.
Service characteristics: Demand for refining is characterized by lot sizes running from a few kilos up to a tonne.
Customer requirements in terms of process tech are hugely diversified— some may demand just one unit operation such as filtration or deodorization, others may demand a stack of operations that mean we need to schedule chill-down periods and intermediate analytical control-checks.
Whatever the demand, the common denominator is that expectations hang on control of cross-contamination, quality of service delivery, and traceability of operations.
Our competitive strengths: Being backed by the ITERG’s analytical lab facilities means we can leverage the analytical competences needed to capture, understand and interpret any number of problems that may arise.
Being able to mobilize small pilot-scale test equipment means we can quickly run preliminary tests to resolve any uncertainty over results.
Being equipped with vast experience acquired on a broad spectrum of products means we can see problems coming before they happen. Our combinatorial library features over 100 different matrices—and counting. Customers can draw on this unparalleled expertise to gain valuable guidance on technical option decisions and on viable applications.
Recurrent contract services can be wrapped up into a statement of contract specs recapping all of your requirements and, if necessary, ruling on the acceptability thresholds for certain parameters (such as residual acidity of the oil). The statement of contract specs will specify key contractual requirements, such as the technological process pathways to follow and performance specifications to hit. It may also set out the arrangements for packaging, identifying and collecting finished product.
A purpose-dedicated scheduling tool running on the Visual Planning® platform enables us to allocate and book the equipment and staff needed while factoring in any number of project constraints dictating product logistics, storage and release.
We never start service delivery until we have first drafted in-depth protocols exhaustively listing out the operations to be performed.
The protocols are designed to so that our technicians have a clear vision of your expectations and can go on to interpret the protocol guidelines in exactly the right way.
The protocols come with report cards prepared to ensure that all the information input required to validate specs-compliant service delivery is collected and compiled.
Note too that our unit facilities are equipped with computer-networked measurement instruments enabling us to automatically measure the defining conditions for temperature and pressure of process operations. The data is charted as time-course curves and retained in the file record for each operation.
Control of cross-contamination
At the conclusion of each service operation, we run through cleandown procedures implemented as a counter-measure against any cross-contamination issues.
In the dry material/semi-solids unit facilities, where certain equipment hardware like screw conveyors cannot be completely drained and cleaned, a throughput barrel-head isolation procedure makes sure residual matter is not allowed to contaminate the following batches.
In the extraction-process unit facility, there is also a risk that the solvent may contain trace amounts of oil from the preceding product. We assay dry extract solvent as and when necessary, and if ever residues are detected, we re-distil the solvent.