The role of hexane solvent in the manufacture of “refined” oil


Refined vegetable oils are obtained from the seeds of various plants. Seed fats are polyunsaturated, which means they are liquid at room temperature. 

There are numerous varieties of refined vegetable oils, including canola or canola oil, soybean oil, corn oil, sunflower oil, safflower oil, and peanut oil. 

The collective term “vegetable oil” refers to a wide variety of oils that are obtained from palm, corn, soybeans or sunflowers. 

vegetable oil extraction process 

The process of extracting vegetable oil from seeds is not for the squeamish. Look at the stages of the process and decide for yourself if this is the product you would like to consume. 

So, seeds are collected first, like soybeans, rapeseed, cotton, sunflower seeds. For the most part, these seeds come from plants that have been genetically engineered to be resistant to the vast amount of pesticides that are used in the fields.

Seeds are cleaned of husks, dirt and dust, and then crushed. 

The crushed seeds are heated to a temperature of 110-180 degrees in a steam bath to start the oil extraction process. 

Next, the seeds are placed in a multi-stage press, in which oil is squeezed out of the pulp using high temperature and friction. 


Then the seed pulp and oil are placed in a container with a solvent of hexane and treated on a steam bath in order to squeeze out additional oil. 

Hexane is obtained by processing crude oil. It is a mild anesthetic. Inhalation of high concentrations of hexane results in a mild euphoria followed by symptoms such as drowsiness, headache and nausea. Chronic hexane toxicity has been seen in people who use hexane recreationally, as well as in shoe factory workers, furniture restorers, and auto workers who use hexane as an adhesive. Initial symptoms of poisoning include tinnitus, cramps in the arms and legs, followed by general muscle weakness. In severe cases, muscle atrophy occurs, as well as loss of coordination and visual impairment. In 2001, the US Environmental Protection Agency passed a regulation to control hexane emissions due to its potential carcinogenic properties and damage to the environment. 

further processing

The mixture of seeds and oil is then run through a centrifuge and phosphate is added to start the process of separating the oil and cake. 

After solvent extraction, the crude oil is separated and the solvent is evaporated and recovered. Makukha are processed to obtain by-products such as animal feed. 

The crude vegetable oil then undergoes further processing, including degumming, alkalizing and bleaching. 

Water degumming. During this process, water is added to the oil. Upon completion of the reaction, the hydrous phosphatides can be separated either by decantation (decantation) or by centrifuge. During the process, most of the water-soluble and even a small part of the water-insoluble phosphatides are removed. The extracted resins can be processed into lecithin for food production or for technical purposes. 

Bucking. Any fatty acids, phospholipids, pigments and waxes in the extracted oil lead to fat oxidation and undesirable hues and flavors in the final products. These impurities are removed by treating the oil with caustic soda or soda ash. Impurities settle at the bottom and are removed. Refined oils are lighter in color, less viscous and more prone to oxidation. 

Bleaching. The purpose of bleaching is to remove any colored materials from the oil. The heated oil is treated with various bleaching agents such as fuller, activated charcoal and activated clay. Many impurities, including chlorophyll and carotenoids, are neutralized by this process and removed using filters. However, bleaching increases fat oxidation as some natural antioxidants and nutrients are removed along with the impurities.

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