Farm to Fork
Extracting of oil from the seed
Extraction is the first step in the refining process. Oils and fats are extracted from their original source (the seeds, fruits or other oil-bearing raw materials) using a variety of different methods. In some cases, for example virgin olive oil, the oil is extracted directly from the fruit by means of a simple mechanical press and used without the need for any further processing. This process is known as cold pressing. For most oils however, the process is more complex. Modern oil mills extract oil using a combination of pressing, cooking and solvent extraction. This process is often carried out in the country of origin.
The seed/bean is cleaned and dried and foreign material is removed. Crushing used to be done between mill stones that later became steel rolls. Seeds with a high oil content like rapeseed and sunflower seed are usually mechanically pressed in expellers after a preheating step in indirectly heated conditioners. The oil bearing material is fed into one end of a cylinder where a power-driven worm conveyor forces the material to the other end of the cylinder and out against resistance. The pressure exerted in the process squeezes out the oil.
Solvent extraction is used to separate oil from seeds/beans. The pre-processed seeds/beans are treated in a multistage counter current process with solvent until the remaining oil content is reduced to the lowest possible level. The mixture of oil and solvent is separated by distillation and the solvent is recycled into the extraction process and the crude oil is stored ready for refining.
Refining of oil
The purpose of refining edible oils and fats is to remove free fatty acids and other undesirable elements naturally present in the raw material which will result in a clear, bright, pale coloured oil with no off flavours or odours and enhanced keeping properties. There are some exceptions, principally products known as ‘virgin’oils, where the extracted oil receives little or no processing in order to maintain their distinctive odour, colour and taste.
Whilst the processes used can vary depending on the type and nature of the particular oil, most oils are processed in three stages, neutralisation, bleaching and finally deodorisation.
Removal of “free” fatty acids: The crude oil is neutralised using a mild alkaline solution in order to remove any free fatty acids (those elements which may have broken away from the triglyceride molecule) which, over time, would otherwise react with oxygen and cause the oil to go rancid. This forms a neutralised oil and soap solution which is then physically separated from the neutralised oil. The oil is then washed to remove traces of soap and then dried
This process is not a chemical reaction: Colour and impurities are removed by mixing the oil with a naturally occurring bleaching clay (Fullers earth), which is subsequently filtered out to leave a clear, clean oil.
A vacuum steam distillation process that removes unwanted smells and tastes in the oil by heating to high temperatures, typically using high pressure steam, under a tight vacuum and blowing steam though the heated oil.
There are several methods used to modify oils. Three of the most common methods are:
Different oil types can be blended or mixed together in varying proportions for many different uses, most notably for specific functionality or to meet particular nutritional requirements.
Many oils are liquid at room temperature. These oils can be changed into semi-liquid or solid oils to improve their functionality. By varying the process conditions a wide range of products can be manufactured from the same starting material. This process has been used for over one hundred years.
This is a simple process whereby an oil which is normally solid at room temperature can be separated into two ‘fractions’. One of the fractions will be more liquid than the start material and one of the fractions will be more solid. Again this process is carried out to achieve a wider range of products.
Bottling and Labelling of Oil
Transportation: Once fully refined, the oil is distributed to the larger manufacturers in bulk tankers or to a refilling plant where it is filled into smaller containers (cartons, tins,bottles) for supply to the foodservice and retail sectors.
Legislative controls: The general provisions of the Food Safety Act 1990 (as amended) provide a general control on the quality and purity of edible oils. In addition there are a number of other regulations which control specific areas including labelling.
It is a legal requirement that labelling must be easy to understand, clearly legible and indelible. It must appear on the packaging itself or on a label securely attached to it and must be clearly visible. Legislation forbids misleading claims as to the nature, substance or quality of the food.
All edible oils and fats shall be marked or labelled with the following:-
- Name of the food
- Net contents by weight or volume
- List of ingredients (where required)
- Best Before date
- Name and address of party responsible
Use of The End Product
Refined oils are an essential ingredient in the preparation and manufacture of a wide range of food products we currently enjoy not to mention an important part of our diet. The largest users of edible oils are the margarine, baking and frying industries who account for over half of total usage. Other users include restaurants, catering, fish and chip shops and domestic use. Oils and fats are also used in the manufacture of paints, varnishes, printing inks as well as in the pharmaceutical industry and personal care.