How to make sure the base substances in cosmetic is qualified?
Oil, fat,
and wax are the base materials in cosmetic and skin care products. The sources
are from plant, animal, mineral, and synthetic products. Animal fats are easy
to absorb by skin, but they are not easy to storage. Vegetable oils are wild
applied in cosmetics due to miscellaneous sources. The mineral oils are
difficult to absorb by skin, but their advantages are price is cheap, better to
isolate the skin with outer, and stable to storage. Synthetic products are
designed to improve the drawbacks of animal fats and vegetable oils. They may
be stable to storage, but they may hurt the skin.
The
structure of animal oil and vegetable oil is Triglyceride. The liquid phase is
oil, and the solid phase is fat. They can be fatty acid and fatty alcohol after
hydrolysis.
There are
3 methods to evaluate the quality of oil, fat, and wax.
Iodine
value (IV)
Iodine
value is mass of iodine in grams that is consumed by 100 grams
of a chemical substance. Iodine value used to determine the amount of unsaturation in fatty acids.
This unsaturation is in the form
of double bonds. The higher the iodine number is, the more unstable in the air
and high temperature is. That means the substance is easy to change its own
property.
Acid
value (AV)
Acid value is the
mass of potassium
hydroxide (KOH) in milligrams that is required to neutralize one gram of chemical substance. The acid number is used to quantify the amount of acid
present. The acid content in an alimentary fat or oil is given
by the quantity of free fatty acids
deriving from the hydrolytic deterioration of the triacylglycerols.
The acid value is based on the
quality will change after the oil are storage for a long time.
Saponification
value (SV)
It is the number of
milligrams of potassium hydroxide required to saponify 1g of fat under the conditions specified. It is a measure of the
average molecular weight (or chain length) of all the fatty acids present.
The acids exist in
vegetable oils such as oleic acid, palmitic acid, linoleic acid, γ-linoleic
acid, stearic acid, palmitoletic acid, ricinoleic acid.
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