In our daily life, we are faced with two kinds of edible oil production, they are cold pressed oil and hot pressed oil. While there exist great differences between them.
Firstly, the production process is different. The cold pressed oil is pressed at room temperature , the oil temperature is low, and the acid value is also relatively low. So there is no need to refine. We would get the oil products after precipitation and filtration. While in the hot pressed oil production process, we heat the seeds up or add chemicals to help. Some seeds like sesame seeds need to be hot pressed because they hold such little oil. Also, the raw oil is relatively dark after high temperature treatment, the acid value will rise, so the crude can be edible only after refining.
Secondly, the oil quality is distinctive. The cold pressed oil is with natural properties. It could avoid the adverse effects caused by traditional high temperature, retain the physiological active substance and its original taste and flavor. It is a pretty good choice for healthy life. Hot pressed oil is with pure taste. The oil plants are pressed after fried. It s mells good especially for oily plants like sesame seeds. while there are a series of changes in the oil plants. The process will destruct the plant cells, denature the protein, reduce oil viscosity, and improve the yield efficiency. What’s more, the bioactive substances in the oil such as vitamin E, sterol, Carotenoid will endure massive loss.
Thirdly, something about the cooking process. Cold pressed oil in deep-fried will not foam or silt. The condition is different when it comes to hot pressed oil.
Fourthly, they apply to diverse raw material. The cold pressed oil is always squeezed below 60℃. Some oil seeds such as camellia,coconut, flaxseed, hemp and olive seeds are suitable for that. However, the mashed material is then heated to 100-120℃ in a so-called cooker in the hot oil processing. Let’s take soybean, high erucic acid rapeseed, cottonseed, peanut and sesame for instance. The produced oil must be processed through oil refinning process, Because there is beany flavor in soybean oil, spicy flavor in high erucic acid rapeseed oil, toxin-cottorrpherol in rapeseed oil and aflatoxin in degenerative oilseeds. All above must be refined. Also the flavor of sesame oil and fragrant peanut can be got only after hot processing.
The last but not the lest, the oil yield. The oil yield achievable through cold pressing is typically between 34,5-35,9% of the total weight of the input material (in case of 42% oil content), while the hot one is normally between 35.7%-37.8%.