Role of Hexane in oil seed extraction

Oil extraction and hexane?
Am I reading it right? Yes! you are right!

Its not surprising if you are not able to figure out how hexane is involved in extracting oil that we consume. Nothing to be apprehensive about, as food grade hexane is universally permitted for extracting oil from seeds and is safe for consumption within the prescribed permissible limits. Now lets get to the core of it by understanding hexane and the processes involved in extraction.

oil seeds
Hexane in Solvent extraction method

Hexane in its pure form is a colorless liquid , and its boiling point is between
50℃ – 70℃ all of which work in favor for oil extraction. To begin the process of solvent extraction, oil seeds (soybean, rapeseed etc.) are removed of impurities and dried to reduce moisture content. The next step is to crack the seeds for size reduction, they are then flattened to form flakes which increases the surface area to facilitate easier extraction. In the succeeding step food grade hexane is fed as counter current and the solvent extracts oil from the flakes. Then the solvent is evaporated from the oil solvent mixture and from the defatted flakes by exposing them to steam by direct or indirect method. The solvent is condensed to recover back hexane. The oil which is devoid of the solvent undergoes further processing to achieve commercial quality.

The oil content in the flakes after removes by solvent extraction method is only 1/2% which is far less when compared to other methods of extraction which may range anywhere between 30- 45%.

Extraction of oil from seeds is carried out by three method

  • Hydraulic press
  • Expeller pressing
  • Solvent extraction

The Solvent extraction process scores over the other two methods by the following advantages

  • Maximum oil recovery
  • Lesser working cost
  • Cheaper price tags for end users
  • Production meets demand
  • The extracted oil is low in sedimentation
  • Solvent loss is low

Why hexane for oil extraction and not other solvents?

  • Hexane has greater ability to extract oil when compared to other solvent like petroleum ether and ethyl acetate.
  • With a boiling point of 69℃ it is able to retain its liquid state at all atmospheric conditions other than for extreme climates.
  • Its reasonable volatility aids easy removal from solids and oil, using low energy.
  • When compared to other solvents hexane records the lowest skin irritation.
  • It aggressively mixes with the vegetable oil and washes it out with out disturbing fiber, protein, sugar and undesired gums.
  • It is low in odor and does not cause discomfort during exposures.

Hexane considerably scores over all other solvents and is the universally accepted chemical for solvent extraction. The method by itself uses lesser hp and maintenance is also minimal. The process flow is quiet similar with slight variation depending on the seed that’s involved in extraction. Seeds that are subjected solvent extraction process are rape seed, canola, sunflower, safflower, Soybean etc. Pure Chemicals Co. has 36 years of experience in chemical industry and is one of the largest supplier of hexane for all the big names in edible oil extraction industry that follow solvent extraction process.

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