LITERATURE REVIEW:

Oil used for

Soap prepared and

Reference

analysis

process followed

Toilet soap prepared

E. E. Mak-Mensah et.al (2011)

Neem oil

using neem oil

Apricot kernel oil and

Toilet soap prepared

Adel Y. Girgis et.al (1998)

palm stearin

Palm oil and castor oil

Soap prepared using

ShogeMansuratOluwatoyin (2011)

different blends

Sheabutter oil and

Soap prepared using

Eke U. B. Dosumu et.al (2004)

palm kernel oil

different blends

Sheanut oil and

Soaps prepared using

A.A. Warra et.al (2010)

groundnut oil

cold process synthesis

Various attempts have been made to produce soap by first decomposing the fat or oil into fatty acids and glycerin, and then converting the acids into the soap by treatment with sodium or potassium carbonate. Three conventional methods of soap making are generally used:

Semi boiling

Full boiling

Cold processed

Semi – boiling

The soft and hard oils or their blends are very suitable for this process in which the fat is first of all melted, followed by treatment with a weak 9-10% caustic soda solution followed by boiling of the mixture. The quantity of caustic soda required for the saponification of the oil is 14-15% of the weight of the oil. This weight of caustic soda is dissolved in ten times its weight of water to obtain a 9% solution. When the caustic solution is added into oil, then saponification starts when an emulsion is formed as the soap is stirred. More caustic solution is then added in to prevent the thickening of mass. After sufficient solution is added bit by bit to complete the saponification and the boiling of the mass continues until the soap was clear. During the boiling process moderate heat was maintained and each addition of caustic soda solution must be allowed to react with the oil before the next addition is made. A hurried addition in the initial stages of the process may retard the saponification, or at the final stages of the saponification may result in the drying of the soap, while judicious addition will keep the mass in a form of smooth homogeneous emulsion. If the soap shows any signs of separation and graining, further water is added to bring the mass to a homogeneous state. The ribbon test involves taking a small sample of the soap from the pan and cooling it. When a little quantity of this cooled soap is pressed in between the thumb and forefinger, the soap does not come out in the form of firm shiny ribbons with slight opaque ends and be clear when held against the light. If this cooled sample draws out in threads, there is excess water present in the soap, and more boiling is required to evaporate more water. If opaque ends appear and vanish, the soap is more oily and requires more caustic, while if the soap is graining, or turbid and white, it indicates a high level of presence of un reacted caustic, and requires more oil. A physical test - the taste test – is also done to determine the level of alkali. This test involves cooling a small quantity of the soap, and tasting it with the tip of the tongue. A sharp bite indicates too much caustic in the soap, while small bite indicates a high level of unsaponified fat or oil. A good soap gives a faint bite on the tongue.

After the completion of the boiling process, the fire is taken off, and the soap is allowed tocool with little stirring. At this point, perfume and colour can be added into the soap.

This process is not suitable for the production of toilet soap, can be used to produce laundry and all other types of soft and liquid soaps. The process does not permit the removal of waste alkali which contains the glycerine produced in the soap making process, and hence the glycerine, which tends to decrease the hardening property of the soap and improves the cosmetic property,

is retained in the finished soap. This method has some advantage over the other two since large quantities of good soap can be produced within a short time. The use of this method also allows a high percentage of fillers to be added in soaps, thus it increases the soap bulk.

2.1 Full Boiling:

The process consists of 4 stages:

Saponification of the oil with alkali

Graining out of the soap

Boiling on strength

Filling.

Saponification of the oil with alkali:

The process is started by putting the melted oil into the boiling tank and running a weak caustic soda solution into the oil. The mixture is then slowly boiled to start the saponification. The beginning of is denoted by the formation of emulsion. When saponification has started caustic soda of higher strength was frequently added in small quantities with continued boiling.Rapid addition of caustic alkali in the initial stages can also entirely delay saponification and in this case water should be added and the boiling continued till the excess alkali is taken up for the saponification to proceed. The end of saponification is determined by the „ribbon‟ and „taste‟ tests. When saponification is completed, the soap becomes very firm and dry with a permanent faint caustic like flavour on the tongue when cooled. The soap, which now consists of this imperfect soap together with water in which is dissolved glycerine and any slight excess of caustic soda, is then ready for graining out.

Graining out of the soap:

The objective of this is to separate the waste lye which is a mixture of glycerine produced during the soap boiling process and excess caustic soda solution from the soap. This is brought about by small use of common salt in dry form or as brine.

The term „graining‟ is used here because after the introduction of the salt, the homogeneous soap gives the appearance of grains. The graining is complete when the soap is practically free from foam and floats as clean soap on the lye. At this stage, this sample of soap taken from the tank consists of distinct grains of soap and a liquid portion which is easily separated.

2.2 Cold Process

This process involves the treatment of fat or oil with a definite amount of alkali and no separation of waste lye. Although it is possible with lot care to produce neutral soap by this process the soap is very liable to contain both free alkali and unsaponified fat. The process is usually based on the fact that the glycerols of certain low fatty acids oils (nut oils like coconut and palm kernel oils) readily combines with strong caustic soda solutions at low temperatures, and generate little heat to complete the saponification reaction.

In this process, it is absolutelynecessary to use high grade raw materials. Oils and fats should be freed from excess acidity because caustic soda rapidly neutralizes the free fatty acids forming granules of soap which grain out in the presence of strong caustic solution, and since the grainy soap is very difficult to remove without heat increase, the soap tends to become thick and gritty and sometimes discolors. The caustic soda being used should also be pure,it must contain as little carbonate as possible, and the water must be soft and all other materials carefully freed from all particles of dirt.

The process involves stirring into the milled fat in a tank, half of its weight of caustic soda solution of at thetemperature of 24°C for coconut and 38°C to 49°C for the blend. The pushing of the caustic solution into the oil must be done not only slowly and continuously.

When the solution is being run into the oil, the mixture must bestirred in only one direction. When all the caustic soda solution had been run into the oil and the mixture stirred for 30 to 45 minutes, chemical reaction takes place with lot of generation of heat, finally resulting in the saponification of the oil. The content of the tank looks thin, but after some few hours it becomes a solid mass. The edges of the soap becomes more transparent as the process advances further, and when the transparency has extended to the full mass, the soap is ready, after perfuming to be poured into moulding boxes for hardening, cutting and stamping.

A little caustic potash solutionis used to blend the caustic soda solution which greatly improves the appearance of the given soap, making it smoother and milder.

Toilet soaps can be classified according to the method of manufacture into the following classes:

cold processed soap,

milled ,

remelted

The process consists of melting the fat in a pan and sieving out all impurities in it, after settling.

The oil is then run into the pan and cooled to 35°C. The right quantities of dye and perfume are then stirred intothe oil. Dyestuff was dissolved in a small quantity of water and filtered to avoid specks of color in the soap. For carbolic varieties, the cresylic acid is not added till after the saponification of the given oil. After adding the dye and the perfume to oil, the required quantity and strength of caustic soda solution is to be run into it in a thin stream with the constant stirring until the oil is completely saponified and the mass begins to become thick. Finally the thickened mass is drained out into soap moulding boxes and then allowed to harden slowly.

Different Types of Soaps:

Milled Toilet Soap making

Almost all the high class soaps used in the market passthrough the milling process which generally consists briefly of thegiven operations: drying of soap, mixing of perfume, milling, compressing, cutting and stamping.

After the solidifying in soap frames, this soap contains 28-30% of water, and this quantity is reduced by half before any satisfactory milling is done. Drying is best done by chipping the given soap into smaller sizes and exposing the chips in trays to a current of hot air at 35-40°C. There are several forms of drying chambers in which the chips in the trays are placed upon a series of racks, one above the other and warm air circulated through.

It is very important that the correct amount of moisture should be left in the soap, not too much or little - the exact point can be determined only by judgement and experience, and depends on the nature of the soap to be made and the quantity of perfume to be added. A range of ll-14% moisture is preferred. Below this range, the soap will crumble during the milling process and the finished soap will have the tendency to crack, while above the range, the soap will stick to the rollers of the milling machine, and mill only with difficulty.

Mixing of Perfume and Dye

When the soap chips have already been dried to attain the required water content, they are put into the amalgamator which is the mixing machine, and the required amount of preferred perfume and dye are added to mix thoroughly at room temperature.

The quantity of the perfume to be added varies considerably with the perfume type used. For cheap grade soaps are used, while for costly soaps is sometimes used.

Milling

From the amalgamator, the soap is put into the milling machine for the chips have to be milled into homogeneous thinsoap ribbons. Milling does not improve the quality ofthe soap but only gives a semi-transparent appearance to it.

2.4 Different types of soap making oils

Fats and oils are esters of different fatty acids and glycerol.Fats and oils are divided into three classes, fixed oils, mineral oils and essential oils. Fixed oils form the main raw materials for soap making as they decompose into fatty acids and glycerol when strongly heated, and can be easily saponified by alkali. Fixed oils, which include both animal and vegetable fats and oils, are further classified according to its physical properties as follows [13]:

a) Nut oils: These oils are characterized to be having large proportion of fatty acids with low molecular weight, especially lauric and stearic acid. Examples of these oils are coconut oil. These oils, when used in toilet soaps are the chief foam-producing ingredients.

They usually saponify easily with strong alkali solution. Once these oils have begun to saponify, the process proceeds rapidly with the evolution of heat. They require very large quantities of strong brine (1648”Be) to grain their soaps, and the grained soaps tend to carry more salt than other soaps. These oils are more suitable for the making of cold process soaps.

Hard fats: The hard fats contain appreciable quantities of palmatic and stearic acids. Examples of these oils are palm oil, animal tallow and hydrogenated fats. These oils produce slow-lathering soaps but the lather produced is more resistant over long periods of time than the nut oils. In soap making, they are first saponified with weak alkali, and in the final stages with stronger alkali solutions.

Soft Oils: These oils have substantial amounts of unsaturated acids, namely oleic, linoleic and linoleneic acids. The soap making properties of these oils vary with their fatty acid composition, and their physical and chemical properties of the acids. Examples of these kind oils are groundnut, cotton seed, fish oil and olive oil. These oils cannot produce a very hard soap when

used alone for soap making. They are generally blended with nut oils. Their soaps lather freely and have very good detergent properties.

Soap making involves a definite chemical decomposition of fats and oils into their constituent parts, like fatty acids and glycerol. The fatty acids combine with little caustic soda, potash or other base forming soap, and glycerol remains free.

All fats and oils used in soap making consist of a mixture of compounds of glycerol with fatty acid which occur in nature in the form of triglycerides. The most important of these acids from the soap maker‟s point of view are stearin, palmitin, olein and laurin. The presence of stearin and palmitin, which are generally solids at room temperature, gives firmness. The greater the percentage present the harder the oil, and the higher its melting point. Where olein is liquid at ordinary temperature, is the chief constituent, the oil is soft.

The soap making properties of fats and oils can be determined by the molecular weights of their fatty acids. With increasing the molecular weight in the case of naturally occurring saturated fatty acids in fat or oil, the following properties are found [13]:

.

The properties of their corresponding sodium soaps vary as follows with increasing molecular weight:

The solubility increases,

The lathering properties improve up to lauric acid and deteriorate from lauric acid upwards,

The stability of the lather increases,

The detergent action decreases,

The soaps have milder skin action as the series progresses,

 The property of holding filling solutions such as sodium silicate decreases.

This explains the reason why nut oil (such as coconut oil) soaps lather readily and profusely but not stably. They also have a firm texture and are hard but dissolve more readily in water than do soaps from the hard oils. They can also retain a good amount of water, and take up large quantities of fillers like sodium carbonate.

2.5 Castor Oil:

The oil is obtained from extracting or expressing the seed of a plant which has the botanical name Ricinuscommunis [7]. The oil is not only a naturally-occurring resource, it is inexpensive and environmentally friendly. Castor oil is viscous, yellow, non-volatile and non-drying oil with a bland taste and is sometimes used as a purgative. It has slightest characteristic odour while the crude oil tastes slightly acrid with a nauseating after-taste. Relative to other given vegetable oils, it has a good shelf life and it does not turn rancid unless subjected to excessive heat. India is the world‟s largest exporter of castor oil.

The extraction of oil from castor seed is by one or a combination of mechanical pressing and solvent extraction. In this process of mechanical pressing, the seeds are crushed and then adjusted to low moisture content by warming in a steam-jacketed vessel. Thereafter, the crushable seeds are loaded into hydraulic presses and they are pressed by mechanical means to extract oil. The oil coming from mechanical pressing has light colour and low free fatty acids [7]. However, mechanical pressing will only remove about 45% of the oil present and the remaining oil in the cake can be recovered only by solvent extraction. In the solvent extraction method, the crushed seeds are extracted with a solvent in a Soxhlet extractor or commercial extractor. Solvents generally used for extraction include heptane, hexane and petroleum ethers.

As in other vegetable oils, it is usual to refine the crude oil obtained from either mechanical pressing or solvent extraction. The main aim of this refining is to remove impurities (e.g., colloidal matter, free fatty acid, coloring matter) and other undesirable constituents, thus making the oil more resistant to deterioration during storage. Castor oil, like all other vegetable oils, have different physical and chemical properties that vary with the method of extraction. Cold-pressed castor oil has low a acid value, low iodine value and a little higher saponification value than the solvent-extracted oil, and it is little lighter in colour.

Castor oil-based synthetic detergents are very less prone to foaming and the disposal of the detergent is hastened since microbiological breakdown is simplified.

Fatty acid composition of this kind of castor oil is:

Ricinoleic 90%

Linoleic 3-4%

Oleic 3-4%

Castor in soaps contributes to fluffy, stable lather, conditioning, moisturizing, quicker trace, softer soap. It is often used to superfat soaps. Castor oil should be used at low percentages to avoid overly soft soaps. Also often used in balms, soaps, shampoos, hair oils, and other thick emulsions for the skin and hair.

2.6 Olive Oil:

Olive oil is one of the most common base oils used in soap making today. 100% olive oil soap, or “ Castile” soap has been made for centuries – and today, soap makers of all types usually include at least some olive oil in their blends.

Olives are a type of fruit called a drupe which is basically a type of fleshy fruit that has one hard seed at the center. First, the olives are generally crushed and ground into a paste. Then, the oil is to be separated from the paste by various methods. The first oil that has come from the very first crush is the “virgin” olive oil. The paste that is left behind after the first extraction is called “pomace.” Fatty acid composition of Olive oil:

Oleic 63-81%

Palmitic 7-14%

Linoleic 5-15%

Stearic 3-5%

Olive oil contributes to soap hardness, stable lather, slippery feel, conditioning, moisturizing. Olive Oil attracts external moisture to your skin, helping to keep skin soft and supple.

Pomace olive oil contains a larger proportion of unsaponifiable ingredients. This slightly affects its SAP value and imparts a greenish color to the oil and to soaps made with it. Pomace oil is preferred to grade A olive oil for soapmaking.

2.7 Neem Oil:

Neem oil is obtained from the seeds of the neem tree. the oil is greenish yellow, non-drying with an acrid and bitter taste, and an unpleasant garlic odour. The oil is extensively used to blend other oils in the making of both laundry and toilet soaps in India. The oil saponifies readily and gives a hard-grained soap with good and very stable lather. When used alone for the making of

soap it is very necessary to grain the soap as this helps to remove most of the disagreeable odour and colour. On the other hand, if it is used to make soap with other oils, it is advisable to first make neem oil soap. After the soap has been grained, the other oils are stirred into the soap and the required amount of caustic soda solution added to start the saponification again. Neem oil soap is used for both laundry and antiseptic purposes. Neem oil has been used in the manufacture of natural cosmetics, soap, toothpaste, hair and skin products, emulsions, liquors, ointments and medicinal cosmetics [5]. However neem oil can be produced mechanically (hot or cold press) or chemically (solvent extraction) from dried neem seeds. The best quality neem oil with a majority of phytoconstituents intact is obtained through cold press. In cold press the oil is lighter in colour and has a milder odour [6]. Moreover potential residual solvents in chemical extracted oil that may pose health hazards to consumers are eliminated since solvents are not used in the pressing techniques.

Neem oil is rich in essential fatty acids (EFAs), triglycerides, vitamin E and calcium. Because of its EFAs and vitamin D, neem oil penetrates deep within the skin to heal the minute cracks brought on by severe dryness. Fatty acids present in neem kernel oil are

oleic acid (52.8%),

linoleic acid (2.1%),

palmitic acid (12.6%) and

stearic acid (21.4%) and

other lower fatty acids (2.3%) [8] and

linolenic acid (1%) [17].

Acid value of neem oil is <20.0, [7]. Neem also stimulates collagen production, good for aging skin. Vitamin E acts as a free radical scavenger, by hindering the oxidizing processes in the skin. It promotes soft and supple skin, helps in reducing old scars and promotes healing. The neem soap will also be slightly antimicrobial. The neem soap will be acceptable to people suffering from skin diseases such as psoriasis and eczema who are allergic to soaps containing Diethanolamine, Isopropyl alcohol, Butylated toluene and Triclosan additives [8].

Neem Oil contributes to stable lather , conditioning. It is said to have the ability to treat a variety of skin disorders such as dandruff.

2.8 Coconut Oil

On an industrial scale, the dry process is the traditional method of extracting oil from the coconut [9]. This is done by crushing copra in an expeller, the trade name of the machine patented by V. D. Anderson. The meal may be further treated with solvents to extract residual oil. The dry process involves mechanical extraction of oil in crushers or expellers with copra as feedstock.

The wet-process feedstock is fresh kernel instead of copra. The extracted oil does not have to be refined, unlike the oil from copra. The co products of oil from the wet process are edible. In addition to oil, other edible co products are recovered from the kernel, namely, coconut flour, protein, carbohydrates, and vitamins. To encourage wider commercial application of this process, the following advantages are emphasized: superior quality of the oil product and the recovery of nutrient co products that would otherwise be lost in copra.

Refining:

Refining of crude fats and oils involves a series of steps for the removal of impurities from the glycerides to make the product suitable for human consumption and improve product shelf life. The impurities are generally fatty acids, phosphatides, metal ions, color bodies, oxidation products, solid particles, and volatiles that include objectionableodour. Crude coconut oil is refined by any of the following methods: (1) chemicalrefining (batch or continuous) and (2) physical refining.

Physical Refining

Coconut oil refiners have gained interest in the physical refining system as a substitute

for chemical refining for the following reasons: (1) physical refining has lower oil losses vis-a´-vis chemical refining; (2) pollution problems associated with soap stock acidulation is precluded;

(3) lower installation cost; (4) lower steam, water, and power consumption; and (5) distilled fatty acids are of a higher grade than the acid oil from chemical refining

Coconut oil composition

Coconut oil belongs to unique group of vegetable oils called lauric oils. The most abundant fatty acid in this group is lauric acid, CH3(CH2)10COOH. Other sources of lauric oils are palm kernel, cohune, and cuphea.

Table1. Composition of coconut oil[10]

More than 90% of the fatty acids of coconut oil are saturated. This accounts for its low iodine

value ranging from 7 to 12. The saturated character of the oil imparts a strong resistance to oxidative rancidity. Assessment

of the oil by active oxygen method (AOM) yielded results between 30 h and 250 h [10]. Although oxidative stability is reduced in some RBD oils, due to losses in the natural antioxidants of crude coconut oils, the addition of citric acid at the end of deodorization as the oil is cooled to 1000C was effective in regaining considerable oxidative stability in the oil [11].