Cracking the Code: Mastering Seed Oil Processing

By Tom Seest

How Is Seed Oil Processed?

At SeedOilNews, we help people who are curious about seed oils by collating information and news about seed oils.

If you follow social media or podcasts, chances are good you have heard about the health risks associated with ultra-processed seed oils (canola, safflower, corn, and cottonseed oil). These highly processed oils have been linked to chronic diseases and other serious health issues.
Understanding why seed oils can be so harmful requires knowing their process – this includes chemical extraction, refining, and deodorization.

How Is Seed Oil Processed?

How Is Seed Oil Processed?

Is Your Health at Risk? The Truth About Chemical Extraction of Seed Oils

Oil extracted from various oil-bearing seeds and nuts can be processed into products ranging from food and cosmetics to biofuels, using various processes – with chemical extraction being one of the more popular methods used to do this.
Solvent extraction is the go-to choice for seed oil extraction and can be carried out using various solvents. When selecting a solvent for extraction purposes, the solubility of oil in said solvent should be assessed along with cost and safety considerations. Hexane has proven itself an ideal candidate as it has solubility properties, low boiling point temperatures, and minimal toxicity issues.
Hexane is a colorless and odorless liquid with an extremely low boiling point that quickly evaporates at room temperature, and its low flammability makes it safe to use. Hexane has become widely utilized as a solvent for the production of high-quality vegetable oils with reduced odor due to this efficient and eco-friendly production method.
Additionally to hexane, many other solvents have been developed for the extraction of oil from seeds and nuts. These include acetone, isopropyl alcohol, iso-hexane and supercritical carbon dioxide.
To achieve maximum efficiency in solvent extraction, seed flakes should first be dried and cracked in order to reduce moisture content and facilitate easier extraction. This can be accomplished by placing them in an airtight container and subjecting them to heat.
Expanding machines are another effective method for turning flaked seeds into pellets that can be extruded through expanding machines, creating larger bulk densities than flakes for improved solvent flow and drainage. Furthermore, pellets offer greater oxidation resistance, so they can be stored longer without quality degradation.
Solvent extraction is a chemical process that employs solvents to dissolve oil from raw materials and then wash it away after using heat treatment on the product. It provides an efficient means of producing edible oils as its high oil recovery rates allow for maximum return.
Hexane remains the primary oil extraction solvent for both conventional and green extraction processes; however, other solvents have also been put to the test as possible alternatives to this chemical solvent. Ethanol, isopropyl alcohol, and iso-hexane have all proven safer options compared to hexane.

Is Your Health at Risk? The Truth About Chemical Extraction of Seed Oils

Is Your Health at Risk? The Truth About Chemical Extraction of Seed Oils

Unlocking the Secrets of Seed Oil Refining

Refining seed oils is an integral component of production. This step involves taking several steps that aim to enhance its quality, flavor and aroma – some may involve physical actions while others use chemicals or processes.
Caustic soda can be used to remove free fatty acids and components such as residual phospholipids and sterols from crude oils, thus decreasing acidity and making the oil more easily soluble while simultaneously deodorizing it.
Step two of producing oil involves bleaching it to remove its natural hue and produce a more stable, neutral oil that’s suitable for commercial uses; however, bleaching also takes away many essential vitamins from its contents.
Bleaching processes produce trans fats, which can be hazardous to human health. They pose a particular danger to people at high risk for heart disease or high cholesterol levels.
Refining also strips oils of necessary antioxidants like phenols and vitamin E, which serve to protect them against rancidity and oxidation.
Seed oils typically contain polyunsaturated, such as omega-6 fatty acids that can become rancid over time when stored.
In order to prevent oxidation, most seed oils should be kept cold stored. Furthermore, these fats should only be used sparingly during cooking and should be combined with plenty of antioxidant-rich fruits and vegetables when consumed.
Studies have demonstrated that an excessive intake of omega-6 fatty acids may contribute to heart disease by increasing inflammation within the body.
Experts also believe that eating too much omega-6 fatty acids may contribute to autoimmune diseases and chronic health conditions by disrupting the balance between omega-6s and omega-3s in our bodies.
Seeds and nuts provide an effective way to achieve a proper balance of fatty acids as part of a well-rounded diet, thanks to their content of healthy monounsaturated and polyunsaturated fats as well as fiber, vitamins, minerals, and antioxidants that will ensure those fats stick around longer in your body.

Unlocking the Secrets of Seed Oil Refining

Unlocking the Secrets of Seed Oil Refining

Is Your Cooking Oil Safe? The Truth About Bleaching

Bleaching is an essential step in refining and deodorizing seed oils, eliminating unwanted oil components that cannot be effectively eliminated through degumming and neutralization processes or that have an adverse impact on the physical or chemical properties of the finished product.
Bleaching of seed oils typically follows deodorization and before deacidification/refining processes, with its purpose being to remove potentially undesirable components such as aldehydes, phosphatides, peroxides, and ketones found in the oil; such components include aldehydes, oxidative trace metals, residual soap and gum residue, chlorophyll and phenolic compounds that could contaminate it further.
The bleaching process comprises several steps and has multiple effects on the quality of reclaimed oil. Many factors play a part in its success, such as clay adsorbent type and amount used, temperature, contact time, and vacuum levels.
Recent work has demonstrated that lower operating pressures (50 to 125 mmHg vacuum) can enhance bleaching efficiency by decreasing water evaporation rates and the interaction of air and oil, leading to greater adsorption rates of phospholipids and chlorophylloids, improved removal of red pigments, lower peroxide values, and anisidine levels – thus improving bleaching effectiveness.
Maintaining an oil slurry tank with moisture levels below 0.1% enhances adsorption rates and allows more effective removal of contaminants, such as chlorophyll, polycyclic aromatic hydrocarbons, residual soap residue, and trace metals. A low-pressure dryer before the slurry tank further assists this effect by decreasing water content before entering the bleachers.
To achieve optimal results, the rate of oil adsorption onto clay adsorbents is determined by the total contact time between them; this time can depend on the equipment used during bleaching processes and should ideally last between 15-45 minutes; batch systems typically employ longer contact times.
Adsorption rate is determined by the type and amount of clay adsorbents used; for instance, the activated carbon absorbs many organic contaminants like polycyclic aromatic hydrocarbons; it can also absorb some lipids and proteins; it serves well in chlorophyll removal as well as trace metal oxidation removal.

Is Your Cooking Oil Safe? The Truth About Bleaching

Is Your Cooking Oil Safe? The Truth About Bleaching

Is Your Cooking Oil Stripped of Nutrients During Deodorization?

Deodorization of seed oils is an integral component of refining. It removes components that compromise their flavor and odor while simultaneously improving quality by eliminating free fatty acids (FFAs) or objectionable volatile compounds from their constituent parts.
Deodorization is an essential step in processing vegetable oils destined for retail sale, particularly edible oils that need to be made odor-free for market consumption. At this stage, a steam stripping agent is used to reduce FFA and volatiles present in the oil so as to rid it of unpleasant flavors or odors.
Deodorizing seed oils requires various techniques, including deodorizers that operate under vacuum and those using superheated steam as a stripping agent. Such systems are usually integrated into deodorization plants that can handle multiple oils simultaneously – offering industrial plants with an economical and efficient solution for deodorization needs.
Deodorization processes go beyond simply eliminating odor, however. Some are designed to preserve micronutrients such as vitamins A and tocopherols within oil products for added nutritional value and extended shelf life. This could drastically improve their nutritional profile as well as their shelf life.
Packed columns and dual-temperature deodorizers are currently the go-to deodorization solutions in the industry, offering the perfect balance between residence time for actual deodorization (which should take longer at lower temperatures) and heat bleaching and stripping of volatile components (which takes place more rapidly at higher temperature).
Packed columns and dual-temperature deodorizers can be tailored to meet the specific requirements of different oil types, applications, and equipment configurations. Operating temperatures typically fall within the 220-260degC range depending on application specifications for the finished product.
These systems operate with a lower vacuum level than typical deodorizers, providing more delicate operation. The lower vacuum level protects the oil from oxidation while simultaneously making sure that FFA and other undesirable compounds are removed without leaving behind hydrolyzed molecules, thus optimizing the quality of finished oil products.

Is Your Cooking Oil Stripped of Nutrients During Deodorization?

Is Your Cooking Oil Stripped of Nutrients During Deodorization?

Be sure to read our other related stories at SeedOilNews to learn more about seed oils.