Refining.

Refining

Midlands Nutritional Oils offers all of its seed oils in their most natural forms - Cold Pressed and unrefined. In recognition of varying customer requirements we can also refine any of our oil products specific to our customer’s needs. The most common requirement is the refining of seed oils to increase their stability and suitability to cosmetic formulations.

If a stable, clear, and odourless oil is required there are various refining techniques available. These methods fall into two categories: physical refining and chemical refining. Both techniques are, of course, suitable for use with food-grade products. Some customers, however, may wish to obtain as 'natural' an oil as possible, so physical refining methods are more appropriate.

Physical methods

  • Filtering.  The unrefined ‘crude’ oil taken directly from pressing is often cloudy because it contains fragments of seed material or sediment. This sediment can be removed by filtration (to a specific micron rating) to leave a clear, sediment free, and bright oil.
  • Deodorising. The strong flavour and pungent aroma of certain oils can be removed by heating the oil under high vacuum. All volatile components are driven off, including most oxidation products, leaving the oil virtually odourless.
  • Winterisation. Seed oils naturally contain varying amounts of waxes and gums that are suspended in the oil following extraction. These compounds can cause the appearance of haze or cloudiness in oils during their shelf life. For certain specifications and applications, this cloudiness is deemed unacceptable, particularly in clear-encapsulated products. Winterisation involves holding the oil at a low temperature to encourage these components to crystallise, allowing them to be removed by a final filtration.

Chemical methods

  • Degumming. Gums (phosphatides), plus any chlorophyll and destabilising metal ions, are removed by washing the oil with high purity water and food-grade phosphoric acid.
  • Neutralisation. The oil is treated with an alkali solution that neutralises any free fatty acids, which can then be removed, along with any lecithin and phospholipids.
  • Bleaching. The oil is mixed with a carefully measured quantity of diatomaceous earth which absorbs the colour components from the oil. The process is a gentle one, and does not involve the use of chemical bleach, as is sometimes assumed. This process also removes metal ions, any residual chlorophyll and other components that may adversely affect the stability of the oil.