The Roles of Different Fats and Oils in Soap Making
Fats and Oils in Soap Making
- What is saponification
- Estimation of saponification of fats and oils
- Saturated fats
- Butters and additive fats
- Cocoa butter
- Shea butter
What Is Saponification?
Saponification is a type of chemical reaction between a strong alkali or base(such as sodium or potassium hydroxide) and a fat. Animal and vegetable fats and oils are made of ester molecules called triglycerides. An ester is a molecule that is formed from an alcohol and an acid. In the case of fats, glycerin is the alcohol, and the acids are fatty acids like stearic, oleic, and palmitic acids.
When the alkali solution is thoroughly mixed with the oils, a reaction called saponification begins. What this means is that the glyceride of the triglyceride breaks off to form glycerine and the sodium or potassium bond with the fatty acid to form soap. With sodium, you get bar soap; with potassium, you get liquid soap.
Every oil or fat has what is called a saponification number, which is determined by the amount of alkali needed to completely saponify the fat. This number is determined by titration a test sample with a standardized alkali and acid/base indicator.
Estimation of Saponification of Fats and Oils
Most people have heard about saturated fats and their link to obesity and heart disease and other ailments. But for soap, they are good. Saturated fats are usually solid at room temperature and consist of straight-chained molecules.
For bar soap, they give the soap hardness as helping the soap last longer in the shower. Most commonly used saturated fat used for commercial soap making is beef fat, also known as tallow. It is usually the first and most abundant ingredient in many soaps. It is widely available as a by-product from the meat industry and is therefore one of the cheapest fats. It created a white and very hard bar of soap. Many people with sensitive skin have problems with soaps made with beef tallow. So, they usually use body washes or seek out bar soap made from gentler vegetable sources
Another common saturated fat is coconut oil. It also gives a very hard white bar of soap, but unlike tallow, the fatty acids are shorter length carbon chains that increase water solubility. This greater solubility in water helps generate more suds and increases the cleaning ability. Unfortunately, soap made from coconut oil alone would be drying to the skin so some conditioning and moisturizing ingredients need to be added. Another very common saturated fat is palm oil. It is the go-to replacement for beef tallow for truly vegan soaps. It is also a good fat when skin sensitivity to beef tallow is an issue. A common recipe for homemade vegan soap consist of palm, coconut, and olive oil.
Unsaturated Fats (Liquid Oils)
The best ingredients to balance the saturated fats in a soap recipe are the unsaturated fats. By contrast, these are usually vegetable oils that are liquid at room temperature and consist mainly of bent and branched chain molecules. They have the property of acting as emollients or moisturizers in soap recipes. In the right proportions, they can effectively offset the drying qualities of saturated fats and create a bar soap that is hard, white, sudsy, and conditioning as well. One of the best condition oils is olive oil. It consists mainly of oleic acid, but the conditioning action mostly comes from the unsaponifiable, which are organic ingredients in the oil that are not acted upon by the alkali. One of which is squalane, which is used in many high-end antiaging cremes. Some other common vegetable oils are soybean, corn oil, safflower oil, castor oil, and sunflower oil. It should be noted that some vegetable oils, notably the polyunsaturated ones, have a shelf life and will darken and go rancid with age.
Butters, Additive Oils, Fats
If a more luxurious soap is desired, you can add special kinds of butters and fast to soap. They add to the smoothness and skin-conditioning properties by leaving a protective barrier on the skin to help moisturize without feeling greasy. Some butters like cocoa butter even have mild pleasant aromas that can add to the bathing experience.
You might already be familiar with cocoa butter in moisturizing creams, cosmetics, and lip balms. It imparts a silky smoothness to personal care products and is an excellent emollient. It's also one of the most stable fats at least partly due to the antioxidants present. It has a typical shelf life of two to five years.
Cocoa butter is extracted from the cocoa bean in tropical regions. It consists of roughly 60% saturated fats and 40% unsaturated fats. It is an offwhite to cream-colored solid which have a melting range of 93 to 101 degrees Fahrenheit, which is near body temperature. But, cocoa butter is stable and quite solid at room temperature. This makes cocoa butter perfect for its most common use of all: the manufacturing of chocolate products. All chocolates are made with cocoa butter including milk chocolate, white chocolate, and dark chocolate.
Shea butter is a buttery fat extracted from the African shea nut. It is a cream-colored fat this is softer than cocoa butter and does not have as much saturated fat. In its native land of Africa, it is used in food preparation. In fact, it is sometimes combined with other fats to substitute for the more expensive cocoa butter in chocolates. But the taste is different so 100% cocoa butter is the preferred fat for chocolate manufacture.
Shea butter also has the property of containing nonsaponifiable components. What this means is shea butter has ingredients that will not chemically interact with alkalies to form soaps. This gives shea butter its texture and emollient capabilities. The main fatty acids are the saturated stearic acid and the unsaturated oleic acid.