Crude oil refers to the primary oil produced from vegetable oils without refining (its main component is a mixture of glycerol tri-fatty acids (commonly known as neutral oil); it also contains non-glycerin substances, collectively referred to as impurities). Because of the simple processing technology, crude oil contains many impurities and is easy to oxidize and deteriorate, so it is not suitable for long-term storage. The edible oil squeezed out by the screw press is not processed by the crude oil refining equipment, but also belongs to crude oil. Refined oil means that crude oil is refined through crude oil refining equipment, and the refined edible oil must meet the quality standards set by the country, mainly because the moisture, impurities, acid value, and peroxide value of the oil meet the quality set by the country Standard; and it is not easy to rancidity and deterioration, and is good for storage, and does not produce a lot of oil fume during cooking; such oil belongs to refined edible oil.
The main difference between crude oil and refined oil lies in the processing technology of crude oil and refined oil.
1. Crude oil processing technology Crude oil refers to the primary oil produced from vegetable oils that has not been refined. For example, a screw oil press is used to squeeze oil, and the continuous rotation of the screw shaft drives the screw to reduce the lead or gradually increase the diameter of the root circle, so that the volume of the squeezing chamber is continuously reduced to produce a squeezing effect; Squeeze out from the gap of the pressing cage, and at the same time compress the residue into crumb-like cakes, which are continuously discharged from the end of the pressing shaft. The oil squeezed by the screw press can be divided into three stages in general, namely the feed (pre-compression) section, the main squeezing (oil output) section, and the cake (heavy pressure oil) section. The processing of oil refining equipment belongs to crude oil.
2. Refined oil processing technology
Mechanical method: including precipitation, filtration, and centrifugal separation, mainly used to separate some peptic impurities suspended in the oil from mechanical impurities;
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, and alkali refining is treated with alkali to remove free fatty acids and oxidation. Mainly used for decolorization.
Physical and chemical methods: mainly include hydration, decolorization, steam distillation, etc. Hydration mainly removes phospholipids, 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 in 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 large amount of oily smoke during cooking and maintains the oil flavor.