Hot Versus Cold Pressed Oils in Cosmetics
Hot Versus Cold Pressed Oils in Cosmetics
Sabrina Schrope
Cosmetic Chemist, Owner of Vitamin You
Overview
Plant oils can be derived from fruits, seeds, roots, and more but for this article we will focus primarily on seed oils. Regardless of the extraction method, the general process is: weaken the cell walls, extract the oil, then filter and purify the product.
There is a misunderstanding on the internet about "cold" pressed methods being at room temperature or even chilled as the name implies. However, both cold and hot press methods involve heating and roasting. Of course, there may be suppliers with different methods, but within the skincare industry both processes involve heating above room temperature.
The Process
1. Seed Defatting & Fragmentation
The first step is to prep the seeds to reduce unwanted plant parts, pesticides, and husks.
2. Seed Conditioning
Also called "roasting", the seeds are heat treated at temperatures 100-160C. Immediately afterwards, they're humidified and left to cool to "moisturize".
3. Oil Extraction
Oils can be extracted by a number of methods! Hydraulic presses use pressure to squeeze out oil and screw presses apply a high shear force to press out oils. Oils can also be expelled, which is more common with hot pressed oils.
Cold pressing can yield temperatures up to 85C but the oil produced is kept between 30-50C. The name can be misleading as this process is usually never "cold," instead the machinery used will produce heat on its own, regardless if the room is room temperature (22C).
Hot pressing yields temperatures above 100C and are usually done on oils needed for cooking. There have been studies done comparing the hot versus cold method and found that different temperatures do yield slightly different micronutrient and flavor profiles of the oil. I also read various online articles claiming this method adds "chemicals" to enhance the aroma, but have not found any industrial manufacturing logs to support this.
4. Oil Purification
Oils are then purified by filtration, sedimentation, or centrifugal separation. Again, different oils will require different purification methods. Once the oil is separated, antioxidants may be added to extend its shelf life for cosmetic use or is sent to be post-processed.
Post-Processes for Cosmetic Use
Advancements in cosmetic chemistry has made enhancing the skin profiles of plant oils possible. Some processes allow the oil to maintain its natural status (NDM), while others use synthetic materials that can no longer be claimed as "all natural" (NDS). Here are three natural processes that plant oils can undergo:
- High Pressure Splitting (HPS): Turns triglycerides into fatty acids.
- Hydrogenation: Makes an oil feel more buttery.
- Esterification: Improves the heaviness and spreadability of oils.
Conclusion
Plant oils are used in skincare to introduce micronutrients and improve the skin-feel of the product. Most of these oils are cold-pressed, which undergo pre-preparation, roasting, extraction, and purification. They can also be post processed to improve its consistency and heaviness. In general, hot pressed oils are used as cooking oils and not so much skincare, whereas cold pressed is used in a variety of industries.
References
Kaseke, T. Fawole, O. & Opara, U. (2022). “Chemistry and Functionality of Cold-Pressed Macadamia Nut Oil.” Processes 10 (1): 56. doi:10.3390/pr10010056
Siger, Aleksander; Józefiak, Marta (2016). “The effects of roasting and seed moisture on the phenolic compound levels in cold-pressed and hot-pressed rapeseed oil.” European Journal of Lipid Science and Technology. 118. doi:10.1002/ejlt.201500249