Investigating Lipids Suitable For Manufacturing Soap for a School Project
My school holds an annual fair for fundraising and this year I thought I would manufacture soap in order to sell at the arts and crafts stand. We have studied oils as part of the option Biochemistry and thought
this would be a way of going deeper while helping with the fundraising.
According to Thomssen1 “this term (soap) is applied to the salts of the non-volatile fatty acids”. Even when there is a wide variety of soaps, this author states that the term is limited to either the potassium
or sodium salt of a higher fatty acid. A fatty acid is a carboxylic acid that is biosynthesized starting from a chain of two carbons. As a result naturally, fatty acids always show even-numbered chains2, and taking
the definition into account we would be working with those in the range C18 to C22. The best sources of these acids are natural fats and oils.
Fats and oils are the names usually given to lipids of which around 99% of those of plant and animal origin can be chemically classified as glycerol esters of fatty acids3. I will need a lipid and either potassium or sodium hydroxide as raw materials.
The purpose of my investigation is, therefore, to determine a suitable lipid to be used in the manufacture of my soap to be used in the school project.
The factors that make a ‘suitable’ lipid include:
• Have good saponification properties
• Result in a soap that will appeal to potential buyers
• Be easy to be found in the city where I live (Kyiv)
• Be of low cost so that the overall cost of the soap is reasonable when compared with other soaps in the market
• It should not become easily rancid allowing me to store it in advance and work with it without major concerns during the manufacture of the soap The saponification reaction involves the use of alkali and while it can be done at cold it usually produces larger yields when using heat.
As heat encourages oxidation of lipids this underlines the need for the oil not to easily become rancid.This does present a challenge as a substantial amount of oils contain fatty acids with several double
bonds (polyunsaturated or PUFA) making them more prone to rancidity than animal fats which are richer in saturated fatty acids. The latter is far less reactive due to the strength of the C-C bond. Thomssen states that tallow, coconut oil, palm oil, olive oil, poppy oil, sesame oil, soya bean oil, cotton- seed oil, corn oil, and the various greases are the most commonly used ingredients for manufacturing soaps.
Tallow oil is commonly used in farms so presents a low level of attraction for potential buyers as this the audience is used to more sophisticated soaps.
Coconut and palm oil appears as quite interesting alternatives. Unfortunately after researching local shops it became evident that these oils can only be bought with great difficulty in Ukraine and are very expensive.
Sunflower oil is rich in PUFA (Polyunsaturated fatty acids) and it has to be blended with other oils for manufacturing soap. Soybean oil does not offer skincare benefits and its main value is that is cheap. It is
also recommended to blend it with other oils to improve quality5.
Olive oil, on the other hand, can be easily found in most large supermarkets and there is a wide selection of prices and varieties. When traveling in Spain and Greece I have seen soaps made of olive oil when
visiting local markets confirming this oil to have strong potential.
The main components of olive oils are triglycerides, a small amount of free fatty acids (FFA), glycerol, phosphatides, pigments, flavor compounds, sterols, and microscopic bits of olive6. The triglycerides in
this oil are richer in oleic acid, with less linolenic and linoleic acids. While the former has only one double bond (monounsaturated), the latter contains several double bonds and is therefore polyunsaturated. This makes this oil more resistant to oxidation than other vegetable oils.
Therefore olive oil appears as more “suitable” considering my first (and broad) purpose. It is quite relevant to avoid oxidation as this process results in decomposition products with undesirable smells.
The original research question can now be further narrowed down. I need to identify an olive oil that will result in the cheapest soap.
In order to this, I must select a chemical test that will support my choice.Several analytical tests exceeded my school’s resources. The saponification value emerged as both helpful and feasible with my current means. This value is defined as the number of milligrams of potassium hydroxide required to neutralize the fatty acids resulting from the complete hydrolysis of 1g of fat. It gives information concerning the character of the fatty acids of the fat- the longer the carbon chain, the less acid is liberated per gram of fat hydrolyzed. It is also considered as a measure of the average molecular weight (or chain length) of all the fatty acids present7. It is a good indicator of quality as it measures the alkali required to both saponify the combined acids and neutralize the free ones. The Saponification value for olive oil according to Thomssen1 is in the range 191-196 mg of KOH/1g of fat.
The lower the saponification value the less alkali will be required to manufacture the Soap. This is relevant as the quality of the alkali has a direct impact on that of the soap.
Thus, lower Amounts will allow us to use better quality material.
Types of olive oil
I was unable to find Ukrainian specifications for olive oil so I will use those of the International Olive The council which is mandatory for state members and closely followed by non-member states. IOC is
supported by the UN and while I was unable to find the Ukrainian policy in this regard, all oils to be considered originating in-state members. According to this organization, olive oils may be classified into:
• Extra virgin olive oil
• Virgin olive oil
• Ordinary virgin olive oil
• Virgin oil is not fit for consumption
• Refined olive oil
• Olive oil
• Olive-pomace oil
• Crude olive-pomace oil
• Refined olive-pomace oil
Of all these, it is the first type that is normally found in supermarkets in Kyiv. Its free acidity, expressed as oleic acid, has to be lower than 0.8g per 100g. As this oil is obtained by either cold pressing or centrifugation its characteristics are best preserved explaining the low amount of FFA (Free Fatty Acids).8
The use of lower quality olive oil often blended with other components (such as glycerin) is recommended at times for the manufacture of soap, but most luxury brands9 promote the use of high quality oil. As a matter of fact “Castile soap” which is the first olive oil soap ever made is claimed to have been manufactured with olive oil only10.
Costs would make lower-quality oils more attractive and research indicates they have better saponification properties11, but unfortunately I had to rely on products found in supermarkets in Kyiv and only high-quality types are offered. Nonetheless, the same references indicate that the oil should be fresh to avoid the appearance of DOS (Dreaded Orange Spots) in the soap bars. These spots result from oxidation processes and literature shows it is more common with low-quality oils and12. Extra virgin olive oil has a rapid turnover in gourmet supermarkets -in particular, bottles of smaller sizes-
therefore this would ensure a better shelf-life for our soap.
I have started answering my research question by identifying extra virgin oil as the most suitable of the different alternatives. I need to find oils that are regularly found in the supermarket and of these
chose the cheapest. So now my research question can be narrowed down to which is the cheapest oil with lower saponification value which may be locally purchased. Research in the local supermarkets
showed that the vast majority of this type originated in Spain, Greece or Italy, with a minor amount coming from Turkey. This is an extra bonus as would allow me to publicize my soap with the names of
these countries underlining its exotic origin.
I made a survey in the three most popular supermarkets in Kyiv and identified the five cheapest oils: Further (fractioned in Ukraine but produced in Spain), Monini (Italy), Creta D’Oro (Greece), Borges
(Spain) and RS (Spain). I chose the 250cm3 bottles as staff in the supermarket said this size had the most rapid turnover. Bottles had no information on production/expiration dates so I decided to buy
them early on Saturday when shelves are replenished. Date of production is a relevant variable but this was the best way I found for having some control over it. I immediately stored them in a box that was kept in a cool room from where they were removed for brief periods of time while performing the analysis. I removed them altogether so that any change would impact them all to the same degree.
I choose the procedure provided by Amrita University7.
• Fats and oils
• Round flask ( I used 250cm details3 as this fitted my condenser and the method provided no further )
• 100cm3 beaker
• Reflux condenser (with access to water)
• Boiling water bath (I used a heater and placed a beaker with water on it. I monitored the room pressure which remains constant in 1.00atm ensuring the boiling temperature was constant)
• 25 cm3 pipette
• 25 cm3 burette
• Ethanolic KOH (95% ethanol, v/v)
• Potassium hydroxide 0.5 M
• Fat solvent
• HCl 0.5 M
• Phenolphthalein indicator
1) Mass 1 g of fat in a tared beaker and dissolve about 3cm3 of the fat solvent (ethanol/ether mixture)
2) Quantitatively transfer the contents of the beaker three times with a further 7cm3 of the solvent.
3) Add 25cm3 of alcoholic KOH and mix well, attach this to a reflux condenser
4) Set up another reflux condenser as the blank with all other reagents present except the fat
5) Place both flasks on a boiling water bath for 30 minutes.
6) After 30 minutes cool flask fast using cold water
7) Now add phenolphthalein indicator to both flasks and titrate with 0.5 M HCl.
8) Note down the endpoint of blank and test.
9) The difference between the blank and test reading gives the number of cm3 required to saponify 1g of the fat.
I followed my school’s safety measures by wearing safety glasses and doing the reflux in a fume hood.
The stock room did not have the required ether so I replaced it with n-hexane to mix with the Ethanol.
I did monitor pressure and time and kept all conditions under control to minimize this problem.
Determination of blank
The volume of ethanolic KOH: 25.00±0.05 cm3
The volume of CCl4: 7.00 ±0.05 cm3
[HCl]: 0.5 M
The mixture was prepared and left overnight in a cool area. It looked transparent and Colorless. I assumed this could not affect the analysis. Unfortunately the following morning the mixture’s color had changed to dark amber which strongly suggests a chemical reaction. I looked in references, but could not figure out any possible reaction. In the absence of a better The explanation I assume this was the result of impurities in the n-hexane which wasn’t very high quality.
|HCl 0.5 M||V initial±0.05 cm3||V final ±0.05 cm3|
I had to add about 9 drops of phenolphthalein as the amber color masked the pink. It was very difficult to establish the endpoint. I decided to eliminate this result and start all over again. Volumes of ethanolic KOH and solvent were kept constant. This time the sample did not change to a dark color and in every case the endpoint was established as that when the pink color of phenolphthalein disappeared.
|HCl 0.5 M||V initial±0.05 cm3||V final±0.05 cm3|
Pilot tests using Furchet and RS oils
|Trial||Mass flask±0.001g||Ma flask &oil±0.001g||VHCLinitial±0.05 cm3||VHCLfinal ±0.05
The mixture showed a light yellow which changed to light orange when the indicator was added. It was fairly easy to detect the change back to light yellow, but certainly not as simple as the simulation shows where the mixture turns colorless. It is important to underline that as the yellow was quite light there was no need to add more than the usual 3 drops of an indicator that reduces any error coming from this source.
Considering these data:
Blank av= 8.6 ±0.1 cm3
Results for pilot tests
The volume used of
|Further trial 1||1.059||9.0||Unacceptable result as
value is negative
|Further trial 2||0.974||8.3||8.6|
|RS trial 1||1.210||7.6||23|
|RS trial 2||1.165||8.1||12|
*Calculations according to the procedure below
Saponification value or a number of fat = mg of KOH consumed by 1g of fat.
Weight of KOH = Normality of KOH * Equivalent weight* volume of KOH in liters
The equivalent weight in an acid-base context is defined as: “The weight of a compound that contains ONE EQUIVALENT of a proton (for acid) or ONE EQUIVALENT of a hydroxide (for base)”13.
The volume of KOH consumed by 1g fat = [Blank – test] cm3
Thus, Saponification number=
=0.5 equivalents dm 3 x 56.00 mg equivalents - 1 x ( titer value of blank - titer value of sample ) dm3
Mass of sample (g)
These results have no reliability and are completely off the accepted ranges. Therefore, the procedure should be reconsidered.I was unable to establish the reaction taking place between the solvent and the alkali.Nonetheless, I realized that given the oils were already liquid there was no reason for using the
solvent.Thus, I decided to repeat the tests without any solvent.
Data collected using the new method
|Trial||Mass flask ±0.001g||Ma flask &oil ±0.001g||VHCLinitial ±0.05 cm3
In every case, the endpoint was established using a control so that no further titrant was added once the mixture matched the light yellow color of the control. As time passed by the alkaline solution also
acquired a slightly yellow shade.
Blanks using a new method
|HCl 0.5 M||V initial±0.05 cm3||V final±0.05 cm3|
As a difference to the previous, the blank is really close to the value of the simulation which suggests the the new method is more reliable.
Results with the new method
The volume used ofHCL±0.1 cm3
(mg KOHg -1 oil) *
(mg KOHg -1
Further trial 1
|Further trial 2||1.239||11.9||192.09|
RS trial 1
RS trial 2
Calculation of errors:
The formula applied for determining the Saponification value is = (0.5equivalents dm-3-1x (titer value of the blank-titer value of sample)dm3)/Mass of the sample (g)
Therefore the overall error will be given by:
Error in titer in blank + Error in titer value of sample + Error in the mass of the sample.
The equivalent mass is an exact value and the concentrations of solutions will also be considered exact as they were prepared by the technician.
As we are working with different magnitudes I will find the %uncertainties so as to be able to add the values.
I will show the calculations on Monini 2 because its Saponification value falls within reference ranges,and being lower than others will require less alkali for the saponification which would reduce our costs.
%uncertainty in titer value of blank= uncertainty x 100 = (0.1cm3/20.4cm3)x 100 = 0.49%
%uncertainty in titer value of sample= uncertainty x 100= (0.1cm3/11.2cm3) x 100 =0.89%
%uncertainty in mass= uncertainty = 0.002 g x 100= 0.15%
affected value 1.347g
Thus, overall %error coming from the equipment would be: 1.53% ≈ 1.5%
In the case of the second trial done with Monini, Saponification value= 191 ± 3mgKOHg-1oil
Section E. Discussion of results and evaluation
Monini -in general, but trial 2 in particular-shows a result that is much closer to the references that the One shown in the simulation.
Considering the difficulties and limitations, tests should be run again to Obtain more reliable values. Unfortunately, this is a rather time-consuming method so there is no time for the current fair, but if the project proves successful I will repeat values for future events.The amended method produced results that are consistent with references and prove this method to be more reliable than the one suggested in the site in the lack of instructed solvent.
It is also cheaper and more environmentally friendly as organic solvents are rather polluting.
The differences between both trials fall within the range of error save for oil RS. Creta D’Oro also showed a larger difference between both values,
and once again the mass was higher than for the Remaining samples. This indicates that future analysis should be particularly careful to keep this variable controlled. Under my working conditions, the presented values are the best I could manage as the school was closed for summer and I had very little time availability.The entire investigation was performed with only one reflux condenser which is very time consuming and imposes severe limitations. I was actually able to complete the task because there were many flasks so I did not waste time drying them up.
The most relevant flaw is that blanks cannot be run in parallel.
The timing of the saponification also It proved challenging as was fairly long and requested a very good organization in particular because of the Laboratory was also used for other purposes.
The endpoint had limitations- even when matched with a control- as the change from light orange to light yellow is challenging. Next time I perform this test, I will work on a method based on curves which would be more reliable 14.
The school has probes and computer equipment that will make this method possible.The change of color of the ethanolic KOH suggests a chemical reaction, and this could interfere with The process. Hence, fresh solutions should be used at all times. This would be very possible if working with several reflux condensers as less time will be invested in performing the tests.
My initial purpose was to identify a lipid that could prove a valid alternative for manufacturing my soap for the fundraising fair. Consideration of the local market, references, and costs led me to opt for olive
oil. I then determined the saponification values of the five cheapest extra virgin oils that are found on a regular basis in Kyiv’s supermarkets. Results show no substantial difference in their saponification values
which are within the references’ range. Nonetheless, Monini shows the lowest Saponification Value and this would require lower amounts of alkali for producing the soap. Considering the cost of the oils differs in less than 2%, I will recommend my team use this oil as a raw component as this difference is less Significant than the cost of good quality alkali while also more environmentally friendly.
The next steps in my project require to identify whether NaOH or KOH results in better quality soap and optimizing the The manufacturing process of my soap.