After the spiral oil press initially squeezes the oil crops, the crude oil squeezed out without filtering and refining is called crude oil. When crude oil is filtered and refined, the oil produced is called refined oil. Both There are big differences. Yuantong oil press will give a more detailed explanation.
Crude oil refers to animal and vegetable fats that have not been refined or leached. Its main component is a mixture of three fatty acids (commonly known as neutral oil); it also contains non-materials, collectively referred to as impurities. According to the dispersion state of impurities in the oil, they can be roughly classified into four categories.
1. Suspended impurities: including sediment, preforms, powder and other solid impurities. The existence of these impurities is conducive to microbial activities, making the oil easily hydrolyzed and rancid, and cannot be eaten;
2. Peptizing impurities: including fat, protein, carbohydrates, etc., the main of which is fat. The presence of these impurities not only makes the oil hydrolyzed and rancid, the appearance becomes turbid, but also produces a lot of foam and black precipitate during cooking; The color and flavor of stir-fried vegetables and fried foods also lose the nutritional value of the fat itself and have certain toxicity.
3. Oil-soluble impurities: including free fatty acids, pigments, hydrocarbon waxes, aldehydes, ketones, etc., as well as trace metals and environmental pollution, mercury, polycyclic aromatic hydrocarbons, aflatoxins, etc. The existence of these impurities is very harmful to the human body, and some impurities can also cause cancer to the human body.
4. Moisture: The crude oil contains a lot of moisture, and the presence of moisture can easily make the oil hydrolyzed and rancid. Refined oil refers to the refined oil that has been refined to remove harmful impurities such as edible and storage in the crude oil and meet the national quality standards.
There are three methods for refining crude oil:
1. Mechanical method: including precipitation, filtration, and centrifugal separation, mainly used to separate some peptic impurities suspended in the oil from mechanical impurities;
2. Chemical method: mainly includes acid refining and alkali refining, in addition to fatification, oxidation, etc. Acid refining is treated with acid to remove pigments and peptic impurities, while alkali refining is treated with alkali to remove free fatty acids. Oxidation is mainly used for decolorization.
3. Physical and chemical methods: mainly include hydration, decolorization, steam distillation, etc. Hydration mainly removes fat, decolorization mainly removes pigments, and steam distillation is used to remove odorous substances and free fatty acids. After refining crude oil, the moisture, impurities, acid value, and peroxide value of the oil meet the national quality standards, and it is not easy to rancidity and deterioration, and is advantageous for storage. It does not produce a lot of oily smoke during cooking and maintains the oil flavor.
