Solvent Extraction of Oil from Seeds

Oil is an important part of our food and there is always a great need for it. With our world so heavily dependent on Oil for meeting its food needs, Oil extraction and refining is an important process in today’s industry. Generally we source oil from oilseeds like Soybean and Rapeseed. They may also be found in vegetables and nuts.

Why we need the process of Solvent Oil Extraction?

We need this process for extracting oil from various sources in an efficient and definitive way. The previous processes had really less efficiency and required a huge amount of power. Also, almost 7-8% residual oil was left in the source from which oil was being extracted.

In comparison to the previous processes, Solvent Extraction leaves only around 0.5% residual oil, consumes less power, and also doesn’t have high maintenance requirements.

What is Solvent Oil Extraction?

Solvent Extraction is the process of diffusing a solvent through to the oil source which results in the formation of a solution consisting of oil in the solvent. In large industries, Pressing may precede the process of Solvent Extraction.

There are many solvents available for this process. But the most widely used, and most widely accepted, is Hexane. This is because of its physical properties and edibility of products of Hexane-based Solvent Extraction. The other notable solvents which are sometimes used in industries are Alcohol-water mixture, Butane, Isohexane, Heptane, and a few others.

Process of Solvent Extraction of oil from seeds

  • Preparation: First, it is necessary to maintain the right size of the seeds. Smaller the size of seeds, greater is the penetration by Hexane. However, if it’s too small, it may prevent the right penetration. Also, it is necessary to ensure maximum contact of the surface of seeds with solvent.
  • Oil Extraction: From the well prepared material (the source of oil), the oil is now actually extracted by using the solvent. The material is treated with the solvent at various stages here to enable enough percolation. This forms the oil with the solvent.
  • Treated Material is Desolventised: Now, after the extraction of oil, the seed is then subject to toasting. This process is generally combined with the processes of cooling and drying.
  • Distillation: One of the most important steps of Solvent Extraction is Distillation. This is the process by which we are able to separate solvent from the actual oil that we have extracted.
  • Solvent Recovery: The solvent is actually still fine and can used again for extraction processes. So, the solvent is recovered and reused for further processing of oils.
This is the process by which Solvent Oil Extraction is carried out in industries. But there are several factors which affect this process.

Factors affecting Solvent Extraction

  1. Water Content in Seed: Diffusion of solvent into the seeds is reduced if there is a high content of water in the seeds. Just a right amount of moisture is all that is needed.
  2. Temperature: Higher temperatures facilitate better extraction.
  3. Solvent Quantity: A high miscella concentration means less energy is required for the removing of solvent from the oil.
  4. Shape of Seed: The shape of seed should be such that it allows flexible movement of solvent in the seed.
Keeping these factors in mind, solvent oil extraction process can be best used for extracting oil from source materials. The de-oiled seed doesn’t have much value on its own after this process and must be further processes before use.

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