Oldest Manufactured Products Soap Biology Essay

Another necessary ingredient in soapmaking is oil. The fat comes from both animal and plant (Watson, 2007). The nature and the properties of the oils and fats used in the manufacture of soap will determine the properties of the soap and also the cost of production (Trew et al., 2010; Moulay et al., 2011). The physical, chemical and Soapmaking properties of the oils should be fully understood when producing soap. The art of Soapmaking will lie in choosing the appropriate oils to produce the qualities needed for the soap since different oil has different properties (Donkor 1986). It is necessary that all animal and vegetable oils and fats to be used for soap-making should be from unsaponifiable matter and they should have good colour and appearance and be in a fresh condition (Simmons et al., 2007).

Tree nuts are rich in monounsaturated fatty acids, predominantly in oleic acid. They contain much lower amounts of polyunsaturated fatty acids, predominantly linoleic acid and small amounts of saturated lipids. Tree nut oils are also used as ingredients of some skin moisturizers and cosmetic products (Shahidi et al., 2005). Some examples of this type of oil are coconut oil, almond oil and palm kernel oil and which are also the most common oil used to make soap (Donkor, 1986; Shahidi et al., 2005; Ward, 2007). They also saponify easily with strong alkaline solution and they are more suitable for the cold process Soapmaking (Donkor, 1986; Warra et al., 2010).

They contain appreciable quantities of palmitic and stearic acids. Although these types’ oils or fats produce slow-lathering soaps, the lather produced is more stable over a longer period of time when compared to nut oils (Donkor, 1986). Soap-making industries commonly manufacture household soaps with a mixture of 75-85 % of hard fats and the rest being lauric fats such as coconut oil and palm kernel oil to be able to meet the soap detergency criteria such as firm texture and foaming (Moulay et al., 2011). Examples of hard fats are palm oil and animal tallow (Donkor, 1986).

They have substantial amounts of unsaturated acids, namely oleic, linoleic and linoleneic acids. Depending on their fatty acids composition, the physical and chemical properties, the soapmaking properties of these oils will vary (Donkor, 1986). Very fine oils contain less than 1 per cent acidity. Commercial oils are graded according to their free acidity, for example, under 5 per cent or under 10 per cent. The desired price of the resultant soap will determine the grade to be used for the soap (Simmons et al., 2007). Examples of soft oils are olive oil and castor oil (Donkor, 1986; Simmons et al., 2007; Ward, 2007; Warra et al., 2010). These oils have very good lather properties and lather freely (Donkor, 1986).

In soap-making, it is preferable to use soft water. Chemical treatments are to be undertaken if the water supply is hard. Softening agents such as lime and soda ash together, soda ash alone, or caustic soda are often used (Simmons et al., 2007). The total permissible amount of water is around 17 percent (Toedt et al., 2005).

Soaps have become a beauty product in many countries and today soaps with different shapes, colour and fragrance are produced. Most scents in soaps come from oils. These are essential oils extracted directly from plants, or fragrance oils that are synthesized artificially from coal tar chemicals (Ward, 2007). Since perfumes are very volatile at high temperatures, they are added to the soaps at low temperatures. Some synthetic perfumes and essential oils may cause soap to darken rapidly on keeping, for example clove oil, and vanillin and other oils may decompose the soap. Therefore due consideration must be given to the action of the particular perfume on the soap. Suitable oils for soapmaking are lavender oil, lemon grass oil and citronella oil (Donkor, 1986).

In soapmaking, all fats and oils used consist of a mixture of compounds of glycerol with fatty acid which occur in nature in the form of triglycerides (Donkor, 1986). In 1000 fatty acids known, only 20 or less are present in significant amount in most important oils and fats (Shahidi, 2005). Saturated fatty acids are of more interest to soapmakers since they have good cleaning properties and lather whereas unsaturated fatty acids are liquids which have poor lather properties (Oghome et al., 2012). Generally the acids used for soap making lie between the ranges from C12 to C18. Below this range, the high water solubility leads to poor surface activity and above this range the water solubility is too low for use (Reinish, 1952). Some examples of fatty acids are lauric and myristic acids which are present in coconut oil and palm kernel oils, palmitic and stearic acids are present in palm oil (Dunn, 2010). Most soap bars are formed from reactions of palmitic, lauric, myristic, stearic or oleic acids with a base (Ward, 2007; Oghome et al., 2012). The main conditioning fatty acids are oleic, linoleic and linolenic. As they increase in size from lauric to stearic, the melting point of the oil increases. The longer the fatty acid chain, the harder will be the soap (Oghome et al., 2012).

These oils are normally complex mixtures of dozens of chemical compounds. Some compounds present in a given essential oil will react with alkali and there will be others that will not.  To be able predict which essential oils will react with alkali, the list of components is examined and it is noted which of them are reactive (See Appendix A). Such compounds consist of esters, phenols, and acids (Tisserand et al., 2011).

A stick blender is then used to reach tracing time faster (about 2 – 5 minutes). The trace stage has been reached when the soap mix has changes from a totally liquid state to a cream like consistency. To know if the soap mix has reached trace, the stick blender must leave a visible trail behind when lifted from the mix. Trace time depends on the oil used, stirring speed and tool type.

The soap will pass through the "gel phase" if the moulds are well insulated. The gel phase will indicate that the saponification reaction is producing natural heat which helps in converting lye and oil into soap.

After 24 hours the soap are then unmolded and can then be cut into appropriate sizes. The soap is then stored for the compulsory "curing time" for about 4 weeks in a cool, dry, and airy room. During curing time, the excess water present in the soap is rid off and the soap is turned into a milder, harder and longer lasting bar. The soap will also obtain its final color and texture during the curing time. A longer curing time will yield a harder and richer soap.