How is edible oil refined? – Fortified Food Vehicles Series

Neutralization

The neutralization step is a “Go/No Go” step. Getting it ‘right first time’ is more a matter of skill and experience than analytical data (which provides the starting point), and fine-tuning is the norm. Low technology skills such as taste and a visual appraisal are used; pipework has viewing ports through which engineers can appraise color, turbulence, etc.; small sampling taps are placed as deemed appropriate. Samples are sent to the Quality Control (Process Control) laboratory, situated on the process floor, for confirmatory analysis using titration, rapid oven drying, and basic spectroscopic (colorimeters) techniques.

Parameters monitored are FFA, Soap, M&I, and Colour, all high to medium risk to the process.

Bleaching

Bleaching is a “Go/No Go” step with a duration difficult to predict (except in broad terms). While color is not the most technical reason for the process, it is the one demanded by the consumer who is increasingly insisting on a clear, bright, and, in many cases, colorless oil [7] [the exception is something like Red Palm Oil in which case the ‘redness’ is a positive quality criterion [8].

The oil will remain in the process until the color criteria are met. The bleaching process essentially removes some color from the oil; reduces how much chlorophyll and carotenoids the oil contains; removes soap, gums, and trace metals; and decomposes oxidation products. Bleaching earth itself accounts for 5-10% of overall refining costs, depending on a variety of factors, including oil type, dosage, oil contaminant levels, specification, and disposal cost.

Parameters monitored are FFA, Soap, Colour, Bleachability, and PV(Peroxide Value), all at high risk to the process. In addition, the flavor will now be checked – to ensure it is becoming ‘bland’.

Deodorise

Deodorization is another “Go/No Go” with a duration again difficult to predict. However, it is the last step in which basic end-use quality is determined for most edible oils. The oil will stay in the process until the product tastes smells, and looks correct according to the sensory inputs of the engineers. Then samples will be taken for confirmatory analysis.

Parameters monitored are FFA, Soap, Colour, Bleachability, and PV, all at high risk to the process. In addition, the flavor will now be checked – to ensure it is becoming ‘bland.’

Oil – at this point – must be capable of meeting a national standard for generic cooking oil.

Fractionate

All of the parameters being measured are checked to maintain the final quality – a low risk – but PV remains a significant risk to fortification.

Some oils require conversion to a more ‘fat like’ product (Vanaspati and Ghee) through hydrogenation [oils high in linoleic acids such as soybean and sunflower are used], and others require filtration such as Palm oil being converted to Palm olein through the removal of the fat like stearin. Other techniques, such as Interesterification and Winterization, may be required. These additional processes are carried out before fortification.

Hydrogenation

Hydrogenation of vegetable oil has been a common practice for over a century. It was introduced to convert unsaturated fatty acids in vegetable oils and marine or animal fats to make them more stable for oxidation. In this process, unsaturated double bonds in the fatty acids of oil molecules react with hydrogen atoms in the presence of a catalyst. Commercial hydrogenation of edible oils uses nickel catalysts. Other catalysts, such as platinum, palladium, copper, etc., have also been applied in hydrogenation applications but are not used in the commercial hydrogenation of edible oils. Hydrogenation has been used to improve the oxidative stability of vegetable oils for improved shelf life and to modify the solids content and melting characteristics of the oil to formulate shortening and margarine products with the desired physical properties.

Parameters monitored are IV and Solids, both of which are high risk to the process and final quality. The flavor is a medium risk, and any change to PV is a high risk to the fortification process. The Nickel catalyst may be monitored – a low risk – but it is not unknown for refineries to add very small quantities of catalyst [9] and shortcut the hydrogenation process.

Winterization

Winterization entails the fractional crystallization of oils and fats, which is then followed by the separation of solids to produce high-quality salad oils. To design an effective winterization process, it is critical to consider the cooling rate of oil, the temperature of crystallization, and the mobility of triglyceride molecules in the oil mass. These variables play a crucial role in separating solid fats as distinct crystals and facilitating their filtration from the oil.

Required, theoretically, in Rice Bran oil, common in sunflower oil. In lower technology countries, this may have been combined with a degumming process carried out by the supplier of the crude refined delivered product.

Interesterification

Interesterification modifies fats and oils to create food ingredients for various applications. This method can reduce levels of saturated and trans fatty acids in certain foods, providing an alternative to animal fats or partially hydrogenated oils.

Parameters monitored are FFA, M&I, Colour, and Bleachability, all high risk to the process, and PV for risk to fortification.