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Edible oil refining
Edible oil refining is a set of processes or treatments necessary to turn vegetable raw oil into edible oil.
Raw vegetable oil, obtained from seeds by pressing, solvent extraction, contains free fatty acids and other components such as phospholipids, waxes, peroxides, aldehydes, and ketones, which contribute to undesirable flavor, odor, and appearance; for these reasons, all the oil has to be refined.
Vegetable oil contains lecithins, phospholipids, and metals, which are generally called, because of their appearance, mucilaginous gums or simply gum. The process of elimination of the gums is called degumming. These gums are natural emulsifiers, that can cause an increase in viscosity which is an important parameter for the final product. Because of this physical problem, it is important to perform this first step since the high viscosity could create difficulties during the subsequent filtration steps.
Depending on the raw oil, these substances are more or less common, so degumming is not an obligatory step: it much depends on the value of lecithins of the source and the concentration of gums in the raw oil. For example, this step is more common in soybean and rapeseed oils, which contain much more gums, than sunflower oil. Because of that, different degumming processes are developed.
This process is generally used when low phospholipids content is present, such as in coconut and in palm oil. Raw oil is mixed with a solution of citric acid, in order to coordinate metals and phospholipids. Usually, the mixture is sent directly to the bleaching treatment.
In this process, the raw oil is treated with a water solution of a chelating agent. Similarly to the previous treatment, the solution coordinates metals and phospholipids, however the chelating agent used, such as EDTA, is able to remove more than 90% of phosphorus content in the matrix such as rapeseed oil.
Also abbreviated as TOD, this is the traditional process where raw oil is treated with acid water and then treated with base, either in this step or during the neutralization.
In this process, it is used the ability of gums to form micelles, which are then separated using a process similar to ultrafiltration. Using this principle, it is possible to separate not only gums, but also other impurities, such as fatty acids, to limit further processes of the oil and reduce waste and energy to purify it. However, it is required the use of hexane to form the micelles, and in the processes in which is possible to avoid it, the flux is low, so it is not feasible on an industrial scale.
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Edible oil refining
Edible oil refining is a set of processes or treatments necessary to turn vegetable raw oil into edible oil.
Raw vegetable oil, obtained from seeds by pressing, solvent extraction, contains free fatty acids and other components such as phospholipids, waxes, peroxides, aldehydes, and ketones, which contribute to undesirable flavor, odor, and appearance; for these reasons, all the oil has to be refined.
Vegetable oil contains lecithins, phospholipids, and metals, which are generally called, because of their appearance, mucilaginous gums or simply gum. The process of elimination of the gums is called degumming. These gums are natural emulsifiers, that can cause an increase in viscosity which is an important parameter for the final product. Because of this physical problem, it is important to perform this first step since the high viscosity could create difficulties during the subsequent filtration steps.
Depending on the raw oil, these substances are more or less common, so degumming is not an obligatory step: it much depends on the value of lecithins of the source and the concentration of gums in the raw oil. For example, this step is more common in soybean and rapeseed oils, which contain much more gums, than sunflower oil. Because of that, different degumming processes are developed.
This process is generally used when low phospholipids content is present, such as in coconut and in palm oil. Raw oil is mixed with a solution of citric acid, in order to coordinate metals and phospholipids. Usually, the mixture is sent directly to the bleaching treatment.
In this process, the raw oil is treated with a water solution of a chelating agent. Similarly to the previous treatment, the solution coordinates metals and phospholipids, however the chelating agent used, such as EDTA, is able to remove more than 90% of phosphorus content in the matrix such as rapeseed oil.
Also abbreviated as TOD, this is the traditional process where raw oil is treated with acid water and then treated with base, either in this step or during the neutralization.
In this process, it is used the ability of gums to form micelles, which are then separated using a process similar to ultrafiltration. Using this principle, it is possible to separate not only gums, but also other impurities, such as fatty acids, to limit further processes of the oil and reduce waste and energy to purify it. However, it is required the use of hexane to form the micelles, and in the processes in which is possible to avoid it, the flux is low, so it is not feasible on an industrial scale.