There are a number of suppliers of oil and fat products used for edible purposes. These products include, but are not limited to olive oil, peanut oil, soybean oil, sunflower oil, lard, shortening, butter and margarine.
The raw materials for these products include animal byproducts, fleshy fruits (palm and olive) and oilseeds. The crude fats and oils from these sources are recovered using a number of methods such as rendering, pressing and extracting with solvents. Some oils, such as virgin olive oil, are ready for consumption after this initial step (pressing), while others require additional processing. The extent of fat and oil processing depends on the source, quality, and nature of the end use.
Alkali Refining
The growing demand, in the United States especially, for bland-tasting, stable oils and shortenings for the end-user has driven the development of extensive processing techniques. The constituents of crude fats and oils that contribute to unwanted flavour and colour are free fatty acids, waxes, colour pigments, phospholipids (gums), oxidised products, metal ions and carotenoids.
Many of these undesirables can be removed by Alkali refining. Alkali refining is the removal of these unwanted items by a chemical reaction with an alkali (caustic soda). This process is completed by a four step process: Conditioning, Neutralisation, Washing, and Drying. The fats are heated between 40º and 85ºC and treated with an aqueous solution of sodium hydroxide or sodium carbonate.
Conditioning transforms non-hydrate phospholipids into their hydrate form by breaking down metal/phosphatide complexes with a strong acid. In neutralisation the removal of free fatty acids and residual gums takes place. Washing is the removal of residual gums by hot water. And drying is the removal of moisture under a vacuum.
Inductive Conductivity can be used to provide a continuous, online indication of the aqueous Alkali solution concentration. The aqueous emulsion formed by the impurities is drawn off the bottom of the tank (in batch refining) or centrifuged off (in continuous refining). After alkali refining, the oil is usually washed with water to remove any residual alkali or emulsion. Measuring the conductivity of this wash water can indicate its quality. Clean water with low dissolved solids will exhibit low conductivity.
Water Refining
Also known as degumming, water refining consists of treating the crude oil with a small amount of water. “Degumming” is where phosphatides in the oil are hydrated with water and then removed by separating in the Centrifugal Separators. The Degummed Oil is then subject to neutralisation with caustic soda where the free fatty acids are converted into residual gums and are separated in hermetic separators. The neutralised oil is then washed and dried.
The “gummy” emulsion of phospholipids created by the treatment with water is then centrifuged off. In the case of corn and soybean oil, this emulsion can be dried to produce a substance known as lecithin, which is used as an emulsifier in many applications. Because of this, the water used in the degumming process needs to be of high quality. Any impurities in the water will end up in the product after the drying process. Once again, conductivity can provide a low maintenance indication of water quality.
Deodorisation
Most fats, even after refining, have characteristic flavours and odours and vegetable fats especially have a relatively strong taste that is foreign to that of butter and are considered undesirable. In order to produce a tasteless, butter-like fat, these oils may undergo deodorisation. To do so steam is blown through the heated oil to distill the volatile components responsible for these flavours and odours. Of course, in order to generate steam you will need water, clean water. pH and conductivity measurements of the feed water are mandatory in this process to ensure the protection of the process equipment from corrosion and scaling. Other than water, you need heat to generate the steam. Proper control of excess oxygen in flue gas allows the boiler to be operated efficiently and safely.
Hydrogenation
For many purposes, it is desirable for the oil to be solid, or semi-solid (margarine and shortenings). The process that converts liquid oils to higher-melting solids is called hydrogenation. The process consists of dispersing hydrogen atoms to double bonds of a molecule through heated oil in the presence of a catalyst. Cylinders from a vendor may supply the hydrogen, but some plants produce it on-site. This usually involves the electrolysis of water to form oxygen and hydrogen. It is critical for the water used in the process to be pure.
Contacting conductivity can be used to ensure the quality of the water in order to prevent damage to the expensive equipment used to generate the hydrogen. The purity of the hydrogen used in this process is critical, both for the product quality, and the process efficiency. Gas Density can be used to measure the purity of the hydrogen gas leaving the generation system.
Processing of Oils
This range includes those refining processes that convert the crude oil into high quality oil products that are fit for human consumption and also the oil modification processes that ensure that the physical properties of the fats and oils meet market requirements at minimal cost.
Processing can remove the components of edible oils which may have negative effects on taste, stability, appearance or nutritional value. To the extent possible, processing should preserve tocopherols and prevent chemical changes in the triacylglycerol.
Edible Oil Processing is very essential parameter to remove harmful components from the oil.
(The author is quality executive at Gandour India Food Processing Pvt. Ltd, Hyderabad. He can be contacted at shareef.foodtech@gmail.com)