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Undergraduate Honors Theses

2018-04-23

Waste Vegetable Oil Properties with Usage and Its Impact on Waste Vegetable Oil Properties with Usage and Its Impact on

Artisan Soap Making Artisan Soap Making

Jenalyn Thorpe

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BYU ScholarsArchive Citation BYU ScholarsArchive Citation Thorpe, Jenalyn, "Waste Vegetable Oil Properties with Usage and Its Impact on Artisan Soap Making" (2018). Undergraduate Honors Theses. 30. https://scholarsarchive.byu.edu/studentpub_uht/30

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Honors Thesis TITLE

WASTE VEGETABLE OIL PROPERTIES WITH USAGE

AND ITS IMPACT ON ARTISAN SOAP MAKING

by Jenalyn Thorpe

Submitted to Brigham Young University in partial fulfillment of graduation requirements for University Honors

Chemical Engineering Department Brigham Young University

June 2018

Advisor: Randy Lewis

Honors Coordinator: Dean Wheeler

ii

iii

ABSTRACT

WASTE VEGETABLE OIL PROPERTIES WITH USAGE AND ITS IMPACT ON ARTISAN SOAP-MAKING

Jenalyn Thorpe

Chemical Engineering Department

Bachelor of Science

This thesis examines the impact of vegetable oil usage in industrial and home

settings on the properties of the vegetable oil and how its usage in soap affects the final

product. Waste vegetable oil (WVO) is often used to make soap as a way to be more

environmentally-friendly and create soap at a low cost in developing countries. Two

settings are examined: home usage (i.e. short-term, small-scale usage) and industrial (i.e.

long-term, almost continuous usage).

This thesis found that lightly used oil (household use) had little to no impact on

the quality of the oil, except for its scent. This resulted in a bar of soap that had very

similar properties to soap made from fresh oil, except for it was somewhat brittle.

However, when oil was used extensively the properties of the oil changed dramatically,

including a deepening of the color, free fatty acid (FFA) content increase to

approximately 5%, and an acquired scent. This resulted in a bar of soap that was darker in

color, and had less lather than fresh oil soap (by 1.4 on a scale of 5). The industrial WVO

had the advantage of reacting quickly with the lye to make soap, allowing the soap

making process to take less time, and for the bar of soap to reach a usable stage quicker,

most likely because of the high FFA%. These results demonstrate that using lightly or

heavily used vegetable oil in soap results in a high-quality product for a very low cost.

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ACKNOWLEDGEMENTS

I would like to acknowledge the help and contribution of my team members

through Global Engineering Outreach: Abbey Wilson, Connor Weeks, and Joshua Frei.

They were instrumental to making (so many) batches of soap, researching,

communicating with Porcón—and ultimately implementing the process developed in the

Granja Porcón community. I’m also grateful to Randy Lewis for his mentorship; to

Matthew Memmott, for agreeing to be my reader and providing support; to Laura Kneib

(owner of F.R.O.G. Soap) for her willingness to share her expertise on working with

waste vegetable oil (WVO) in soap-making; to Sam Thorpe, for his continued support

and encouragement.

vi

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TABLE OF CONTENTS

TITLE .............................................................................................................................................. i

ABSTRACT ................................................................................................................................... iii

ACKNOWLEDGEMENTS ............................................................................................................ v

TABLE OF CONTENTS .............................................................................................................. vii

TABLE OF TABLES .................................................................................................................... ix

TABLE OF FIGURES ................................................................................................................... ix

1. INTRODUCTION ...................................................................................................................... 1

2. EXPERIMENTAL ...................................................................................................................... 4

3. RESULTS AND DISCUSSION ............................................................................................... 10

4. CONCLUSIONS..................................................................................................................... 244

REFERENCES ........................................................................................................................... 277

APPENDIX ................................................................................................................................. 299

viii

ix

TABLE OF TABLES

Table 1: Scale for Measure of Soap Quality ................................................................................... 7

Table 2: Linear Regression Parameters for FFA Content vs Time ............................................... 12

Table 3: Characteristics of Industrial WVO vs New Oil Soap ................................................... 222

Table 4: Characteristics of Household WVO vs New Oil Soap ................................................. 233

Table 5: Summary of NaOH (g) to Titrate 1 mL of Each Oil Sample and Corresponding FFA%

..................................................................................................................................................... 299

Table 6: Summary of Average HSV Values for Industrial and Household Use Oil Samples .... 311

Table 7: Summary of Scent Test Perception Numbers for Industrial and Household Use Oil

Samples ....................................................................................................................................... 322

TABLE OF FIGURES

Figure 1: Saponification reaction. Image is modified from Đokić, et al. ....................................... 2

Figure 2: Soap mixture at trace. ...................................................................................................... 9

Figure 3: Free fatty acid content of industrial peanut oil with time, with 95% confidence interval

bands. ............................................................................................................................................ 11

Figure 4: FFA content (%) plotted against time (i.e. sample number) for household use samples.

....................................................................................................................................................... 13

Figure 5: Industrial oil samples, from clean (0) to WVO (W)...................................................... 14

Figure 6: HSV values of industrial oil with time. ....................................................................... 166

Figure 7: A comparison of home-usage oil samples, from least used (left) to most used (right).

..................................................................................................................................................... 177

Figure 8: HSV values over time for household use oil samples. ................................................ 188

x

Figure 9: Scent of industrial oil with time. ................................................................................. 199

Figure 10: Impact of fry time on scent of household use samples................................................ 20

Figure 11: A visual comparison of industrial WVO (left) vs. clean oil soaps (right) made with

peanut oil. .................................................................................................................................... 211

Figure 12: A comparison of household WVO (left) vs clean oil soaps (right) made with soybean

oil. ............................................................................................................................................... 233

1

1. INTRODUCTION

1.1 WVO Problem Worldwide

Waste vegetable oils (WVOs) are commonly produced in high quantities in many

countries, with the highest being in the US (10 million tonnes per year) [1]. They are

commonly produced as by-products of community living where foods are fried. In the

United States, the EPA (Environmental Protection Agency) warns that vegetable oils can

cause significant effects to the environment, including: fouling shorelines; coating

animals and plants and suffocating them through depletion of oxygen; destroying food

supplies, breeding animals, and habitats; and being toxic [2]. Large generators of used oil

are required to properly store and dispose of WVOs.

WVO oil consumption is also a sizable problem in Peru. Peru produced 270

tonnes of vegetable oil in 2014, with another 38 tonnes imported; an estimated third of

this oil is discarded as WVO. While estimates are not precise, much of the household

WVO goes down the drains or is disposed of in the trash, while much of the industrial

WVO (i.e. from restaurants) goes to Bioils, a company that collects WVO across South

America and sends it to Europe, where Royal Dutch Shell converts it into biodiesel [3].

Small, remote towns like Porcón, Peru (population 2000, approximately 30 km

from the nearest sizeable city) do not have access to WVO collecting facilities and create

such small quantities of WVO that biodiesel production is not feasible [4]. However, this

WVO can be recycled to lessen environmental impacts and enhance the community by

using the WVO as the primary feedstock in a soap-making process. Such a process can

also provide a means for developing communities to improve personal hygiene [5].

2

1.2 Saponification Process

Soap is created through saponification through alkaline hydrolysis of

triacyclglycerols, the primary component of vegetable oils. The alkaline reactant used in

this process is commonly industrially purified NaOH or KOH, although lye can also be

created using ash with somewhat inconsistent results. Triacyclglycerols are main

constituents of vegetable oil, although their precise make-up of triacyclglycerols and free

fatty acids varies depending primarily on type of oil and its usage. [6]. While WVO is

variable in its composition, it can be used as the primary feedstock in soap-making after

treatment (generally filtration to remove entrained particles) to ensure its quality. This

reaction is shown below in Figure 1, where the primary reactant is the triglyceride—an

ester derived from fatty acids (shown by the R groups below). This is reacted by the

alkali (or base or lye, here NaOH) to form glycerol (left in as part of the soap product)

and soap molecules. Free fatty acids (in the form of RCOOH) will also react with NaOH

to form soap molecules. The glycerol, a side product in the soap making process, is left

inside the soap structure.

Figure 1: Saponification reaction. Image is modified from Đokić, et al.

3

1.3 Soap Making in Remote Areas

Soap making can be advantageous for small towns where WVO production may

be variable and limited and labor is scarce, making biodiesel production inopportune.

Small-scale soap making processes have been implemented in developing communities

across the world [7]. Although sources for sodium hydroxide may vary in remote areas,

small quantities of sodium hydroxide can be found commercially, such as through

Mercado Libre (equivalent to the U.S. Amazon) in Peru.

Adding a soap-making process to the community of Porcón, Peru will be

advantageous in more than one way. Hand-made artisan soaps will add to the diverse

handcrafted souvenirs offered to tourists visiting Porcón and offer an additional stream of

revenue. Additionally, a soap-making process can help the people of Porcón to be more

environmentally aware and to reduce waste (household and restaurant WVO) by using it

to create valuable products.

1.4 Understanding Properties of WVO through Usage

The characteristics of soap vary greatly depending on the types of oils or fats that

are used to create it. Different vegetable oils have different compositions of fatty acids

which affect properties such has hardness or lather. Vegetable oil also changes properties

with usage. For example, fatty acids can be freed from triglyceride structures causing the

smoke point to decrease; scents of foods fried can be left behind in the waste oil; the

color of the oil can darken; and particulates and water molecules can be left behind from

food items and become incorporated into the oil [8]. These side effects have the potential

4

to impact the quality of the bar of soap created—and have implications for other usages

(such as re-using oil again for frying or using the WVO in biodiesel production). As

usage situations vary, two scenarios were studied for WVO production—industrial (long-

term, almost continual usage of frying oil) and home usage (limited, short-term oil usage

in small quantities over a cook stove).

2. EXPERIMENTAL

2.1. Oil Characterization

2.1.1. FFA Content

Refined vegetable oils contain less than 0.05% free fatty acids, or FFA [9].

However, triglycerides can break down in the presence of water, heat, or other elements

to which they are exposed during use. The free fatty acid content can be measured by

titrating the oil with NaOH (1% wt) and phenolphthalein, an indicator that turns pink

when the pH of the solution exceeds approximately 8.0. In the presence of lye, the fatty

acids will quickly react (in comparison to the triglycerides, that react relatively slowly

through the saponification process). NaOH solution is added until it is in slight excess,

turning the solution pink. The amount of NaOH that must be added to the solution to

neutralize any FFA present is representative of the how broken down the oil molecules

have become during usage scenarios. The approximate free fatty acid content (%) in the

oil is determined by dividing the mL of NaOH solution by 1.3. Titrations were performed

at least two times (more if results were inconsistent with each other) to ensure

consistency and representativeness for each sample [10].

5

2.1.2. Color

Color is important aesthetically and because it affects the color of the final bar.

Color can be measured through an online color summarizer for different qualities of the

color [11]. While there are several ways to measure the color of the samples, color was

measured in terms HSV, a common system for measuring the type of color. HSV stands

for hue, saturation, and value. Hue describes the color; saturation is a measure of how

intense the color is, and value is a measure of how much white or black (i.e. brightness) is

incorporated with the color. Saturation and value are normalized to a scale of 100, where

100 for saturation is completely saturated (i.e. vibrant and not faded); and for value is

completely bright (or no black blended). Hue is expressed in terms of angle in the color

circle with red being 0, followed the other colors rainbow order until 360 [11].

To measure the color of the samples, a picture of each sample was taken on a

white background during the same time of the day (to keep background light constant).

All samples were taken in the same type of container to keep the thickness uniform

between samples, as the oil appears darker or lighter depending on its thickness. The

picture was then analyzed for its color content based on HSV, using an online color

summarizer that analyzes the color of each pixel in the picture taken. Average values are

reported below.

2.1.3. Scent

Much of the scent in WVO is eliminated during the saponification process;

however, odorous WVO can be unpleasant to work with and can also carry through to the

6

final bar of soap. Scent can be measured by perception on a scale of 1 to 5, as shown

below. Scent tests were performed twice for each unfiltered sample, and if the results

were more than 1 different, the scent tests were repeated until the results were consistent.

These tests were performed by one individual; however, the tests were performed for the

samples randomly and blindly as to remove as much uncertainty and bias as possible. The

average scent value is recorded in the Results section.

1—strong and lingering scent of fried food

2—noticeable and somewhat strong scent of fried food

3—mild scent of fried food

4—strong scent of oil, or very weak scent of fried food

5—no noticeable scent, neutral scent, or very weak scent of oil

2.1.4. Soap Quality

While soap cannot be produced for every sample of oil during usage, soap quality

can be assessed for clean and completely used oil. Soap was assessed for the following

qualities: hardness, lather, conditioning effect, and scent. Soaps were tested after they had

reached a safe pH range (8-10). Hardness is measured by dropping a hammer from a

fixed height on a screw and seeing how deeply the screw penetrates the soap. Smell is

judged by smelling the bar of soap after use. Lather is based off the number of bubbles

formed after lathering with soap for 10-15 seconds. Conditioning is how the hands feel

after washing with the soap.

7

Table 1: Scale for Measure of Soap Quality

Lather Conditioning Smell* Hardness

1 Excessive

bubbles

Feels like lotion was used Smells bad or

smells like oil

>2 turns deep

2 A lot of bubbles A little more moisturized Neutral 1-2 turns deep

3 Some bubbles Neutral <1 turn deep

4 Very few

bubbles

Takes some moisture Small divet

5 No bubbles Makes hands significantly

drier

No

deformation *The smell test was intended to also judge the effectiveness of added scents, so as no scents were added, the main concern is if the smell of the used oil can be detected.

2.2. Materials

Non-hydrogenated soybean oil was used to assess effects of household use;

peanut oil was used in an industrial setting. Although ideally these oils would be the

same, soybean oil was selected for household use tests because that is what is used in the

restaurants in Porcón, Peru. No industrial vendors that use soybean oil were willing to

provide samples. Soaps were made in silicon molds.

2.2.1 Industrial WVO

Industrial samples were collected every afternoon for a month—the usage period

of oil. Samples were collected at approximately the same time every day to ensure that

the amount of usage between each sample is the same. Samples were not collected on

Saturdays (where usage is approximately 20% that of weekdays) or Sundays, nor were

these days counted in the number of days. The industrial WVO was collected from a fast

food restaurant that has the fryer on and in use for approximately 74 hours every week.

8

The oil is used to fry primarily chicken and potatoes. 20 samples were collected. These

samples were each tested for color, scent, and FFA value. Final WVO was used to make

soap samples.

2.2.2 Household WVO

Household samples were created by using soybean oil in frying. The oil was used

to fry assorted items, such as potatoes, donuts, onion rings, and battered fish (tilapia).

Samples were collected between frying like items. One batch of household oil was

created, with a total 12 samples. These samples were each tested for color, scent, and

FFA value. Final WVO was used to make soap samples.

2.4 Soap Creation

Soap was created by following a standard procedure as outlined below.

1. The desired amount of vegetable oil (unused or filtered WVO) was weighed,

generally 200 g.

2. Personal protective equipment (PPE) was donned. This included closed-toed

shoes, eye glasses or goggles, apron, and gloves.

3. The corresponding NaOH was weighed. This was determined using standard

saponification numbers: 0.133 for peanut oil and 0.136 for soybean oil [12]. The

saponification number means that for every gram oil, there is the corresponding

part of NaOH. Thus for soybean oil, each gram of oil requires 0.136 grams of

NaOH to completely saponify the oil.

9

4. The corresponding quantity of water was measured. Water and NaOH were used

in a 1:1 weight ratio.

5. The NaOH was slowly poured into the water and agitated until the NaOH was

fully dissolved in the water. Note that this is an exothermic process, so the

container would often become warm to the touch.

6. The lye solution was slowly poured into the oils and agitated with a stick blender.

The solution was mixed until the soap reached a phase called “trace.” At this

point, the mixture has reached a point where one can be assured that the

saponification reaction is occurring. Here the batter is thick enough that when

swirled on top of the soap mixture, a small amount stays on top of the mixture for

at least a few seconds. The

thickness of the mixture of this

point can be described by the

consistency of thick cake batter.

This is shown to the right in Figure

2. This generally takes 5-20

minutes.

7. When the solution reached trace, the batter was poured into molds.

8. The molded soaps were let to sit for 2-5 days.

9. The soaps were then unmolded, and let to sit for an additional 3-5 weeks.

10. The soap was tested with a pH strip (finished soap should have a pH in the range

of 9-10) to ensure that the soap was safe for use.

11. Once the soap was safe for use, it was analyzed for desired properties.

Figure 2: Soap mixture at trace.

10

3. RESULTS AND DISCUSSION

3.1. FFA Content

3.1.1. Industrial WVO

Industrial samples were titrated to determine the FFA% in each sample, and then

plotted against days of use to determine the correlation between FFA and oil usage. The

samples showed a strong linear correlation with time, with an R2 value of 0.89. This plot

is shown below in Figure 3. Note that the 95% confidence intervals are found tightly

around the data points taken. This suggests that each day of use contributes equally to the

breakdown of the triglyceride molecules found in the oil. Note that the exact amount of

usage each day might vary, which accounts for some of the variation seen; however, the

exact amount of usage the oil received each day was not available to account for that in

the trends. A full summary of titration values is found in Table 5 in the Appendix.

11

Figure 3: Free fatty acid content of industrial peanut oil with time, with 95% confidence interval bands.

Table 2 below outlines the linear regression parameters for FFA% as a function of

time. This is in the form y = mx + b, where y is the FFA% at time x (in days), and b is the

initial FFA% in unused vegetable oil. Note that the initial FFA% is 0.1585%. This is

close to the tabulated estimates that refined vegetable oil sold for use has less than 0.05%

FFA. Note that data could not be taken on the last day (the day that the oil was

discarded); however, another WVO oil sample from the same industrial setting had an

FFA value of 6.73%, a value that is higher than the day 30 predication for this batch of

oil (approximately 5%). This implies that there is deviation between batches. This was

-2

-1

0

1

2

3

4

5

6

0 5 10 15 20 25 30

Free

Fat

ty A

cid

Con

tent

(%)

Number of Days Used

Prediction

Upper 95 % Conf. Prediction Band

Lower 95 % Conf. Prediction Band

Upper 95 % Conf. Single Pt Band

Lower 95 % Conf. Single Pt Band

Experimental Data

12

not explored in this thesis; however, a more rigorous understanding of the usage of

vegetable oil would require additional data points from more than one batch of oil.

Table 2: Linear Regression Parameters for FFA Content vs Time Parameter Value Standard Deviation 95% CI

m 0.2934 0.2180 0.4645

b 0.1586 0.0144 0.0307

The increase in free fatty acid content in the oil had interesting implications for

the soap making process. Although the time to reach trace (a measure that the

saponification is well under way) was not thoroughly recorded for each batch of soap,

industrial WVO reached this point significantly quicker than any other batches of soap,

whether using clean oil (any type) or used soy (i.e. household WVO), which needed

longer mixing times or the addition of heat to reach this stage. In general, using industrial

WVO the soaps reached trace in less than 20 minutes, whereas the other soaps could take

up to an hour or longer (if using a whisk). The industrial WVO soaps also harden more

quickly, and reached a safe pH for use earlier. This phenomenon is most likely caused by

the high concentration of free fatty acids found in the industrial WVO that readily react

with the NaOH and catalyze the further reaction with the triglycerides. This idea is

supported by the fact that in biodiesel production, additional lye is added to account for

the fact that some of the WVO will react to make soap from the free fatty acids [10].

3.1.2. Household WVO

The FFA content for household oil samples is shown in Figure 4 below. Note that

there is essentially no correlation between sample number (i.e. time) and FFA%, as the

13

R2 value is 0.0014. This is likely because the oil was used for such a brief time that the

triglyceride molecules did not break down (to any significant effect) as the industrial oil

did. When the household WVO was used to make soap, it behaved similarly to clean

soybean oil in how it reacted with NaOH, which makes sense in terms of the relatively

similar chemical make-up. A full summary of titration values used to determine free fatty

acidy content can be found in Table 5 in the Appendix.

Figure 4: FFA content (%) plotted against time (i.e. sample number) for household use samples. Total time of frying for household use oil was approximately 2.5 hours, so each point represents roughly 15 minutes of frying.

y = 0.0014x + 0.373R² = 0.0014

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 2 4 6 8 10 12

Free

Fat

ty A

cid

Con

cent

(%)

Sample Number

14

3.2. Color

3.2.1. Industrial WVO

Figure 5 below shows the influence of usage on the oil color, where unused

peanut oil is on the left and WVO is on the right. There is a visible color gradient;

however, many of the middle samples are relatively similar in color.

Figure 5: Industrial oil samples, from clean (0) to WVO (W). Each number refers to how many days it has been used for.

Each sample was also looked at to see how HSV values changed through time,

and what type of rate of change occurred. This is shown in Figure 6 below, with a full

summary included in Table 6 of the Appendix. The value (i.e. brightness) of the oil

samples remains constant throughout, and the hue (i.e. color) of the samples remaining

15

relatively constant. The saturation (i.e. vibrancy of the color) increases with time,

demonstrating that the samples become more saturated in the color as time goes on. This

result matches visual perception—the samples become darker in color. Data points were

not able to be taken for the final sample of oil of that batch; however, a data point was

collected from a different batch. This is shown in Figure 6 all the way to the right (darker

points). Second order polynomials are included for the sample points that were taken

from the same batch. Second order polynomials were used to provide the best fit,

especially as the saturation of the samples increases more in earlier stages of usage than

later stages. The second order polynomial forecast to day 30 and the final points from a

different batch of used oil do not match up very well. This is likely because of the

differences that occur between batches of oil fried.

16

Figure 6: HSV values of industrial oil with time. Final points (all the way to the right) are WVO samples from a different batch of industrial vegetable oil. Lines between points are to guide the eye.

3.2.2. Household WVO

A comparison of oil samples taken while creating household WVO is shown

below in Figure 7, with the least used sample on the left, and the WVO shown on the

right. The samples do increase in darkness; however, this change is subtle and does not

significantly affect the color of the bar of soap (see Figure 12). This is not surprising, as

the household oil was only used for approximately 2.5 hours.

y = -0.029x2 + 0.614x + 42.27R² = 0.5061

y = -0.1016x2 + 5.0025x + 24.034R² = 0.8977

y = -0.0035x2 + 0.1482x + 70.625R² = 0.1148

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35

Val

ue

Time (days)

H-WVO S-WVO V-WVOH S VPoly. (H) Poly. (S) Poly. (V)

17

Figure 7: A comparison of home-usage oil samples, from least used (left) to most used (right).

These samples were analyzed to determine the precise color differences that occur

over time, as shown in Figure 8 (HSV values). A full summary can be found in Table 6 of

the Appendix. As can be seen, the HSV values remained relatively constant except for the

saturation level. The value and hue values (constant here) are relatively similar to that of

the industrial samples, confirming that the pictures were taken in relatively similar

lighting and that the oils can be compared for color changes. The saturation value also

starts at approximately the same value. Unlike the value and hue values, the saturation

18

value did change—that is, the color itself did not change dramatically, but it did become

more vibrant. This confirms what was visually seen—the samples become darker.

Figure 8: HSV values over time for household use oil samples. Lines between points are to guide the eye.

3.3. Scent

3.3.1. Industrial WVO

The industrial sample perceived scent was plotted against time in Figure 9 below.

The trend is generally linear, with the scent of the oil becoming more like the scent of

fried foods with time. The overall variation seen (as given by an R2 value of 0.3418) is

most likely because of timing of taking the sample with respect to filtration (industrial

vegetable oil is filtered multiple times during the day as it is used). Filtration removes

particles which can hold scent in them, so samples that were taken soon after filtration

most likely had less particles and therefore less noticeable scent. This is also most likely

partially because of imperfect perceptions of scent. Based on the linear correlation, the

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10

HSV

val

ue

Sample Number

H V S

19

final WVO oil has a scent rating of 1.7. A full summary of scent perception values can be

found in Table 7 of the Appendix.

Figure 9: Scent of industrial oil with time.

3.3.2. Household WVO

Each household oil sample was tested to determine strength of the scent of the oil

compared to what was fried in it, as shown in Figure 10 below. The strength of the oil

scent varies somewhat from sample to sample—this could be because of the specific

items that were fried in the oil, or because of other variations. This is seen by the overall

somewhat weak correlation, as the R2 value is 0.3146. However, the overall trend is

downward—that is, the longer the oil is used, the more it smells like the food that is

being cooked in it, which validates everyday experience. The scent of the oil reaches a

scent almost as poor as the industrial samples by the end of its usage. A full summary of

scent perception values can be found in Table 7 of the Appendix.

y = -0.063x + 3.6284R² = 0.3418

1

1.5

2

2.5

3

3.5

4

4.5

5

0 5 10 15 20 25 30

Ave

rage

Sce

nt S

core

Number of Days Used

20

Figure 10: Impact of fry time on scent of household use samples.

Significant to note, however, is that the overall scent that the household WVO

reaches is close to the industrial WVO (extrapolated 2.4 scent rating compared to 1.7 for

industrial WVO). This implies that household WVO retains the scent of food items more

readily than industrial WVO. This could be in part because of the frequent filtrations

done to the industrial oil, or the differences in usage. This could also be partially because

the two scenarios use different types of oils—soybean oil may more readily retain scents

than peanut oil. Another possible explanation is that most of the scent is held in the

particles entrained in the oil. The household use samples generally had more particles

than the industrial oil samples did, as the household use samples were not filtered at all

and the industrial samples were filtered some during usage of the oil.

y = -0.1432x + 4.005R² = 0.3146

00.5

11.5

22.5

33.5

44.5

5

0 2 4 6 8 10 12

Ave

rage

Sce

nt S

core

Sample Number

21

3.4. Soap Characterization

3.4.1. Industrial WVO

Industrial WVO was used to make soaps, and compared to pure peanut oil for

distinctive characteristics. A visual representation of the two bars of soap are shown

below in Figure 11, with WVO soap on the left and pure peanut oil soap on the right. The

WVO soap is significantly darker, with a slightly tan hue, where the pure peanut oil

appears white.

Figure 11: A visual comparison of industrial WVO (left) vs. clean oil soaps (right) made with peanut oil. The soaps were also compared on characteristics of hardness, scent, lather, and

conditioning effect, which are enumerated in

Table 3 below. WVO soap was harder, smelled approximately the same (i.e. neutral) and

had approximately the same conditioning effects (i.e. dry hands slightly); however, the

fresh peanut soap had significantly more lather than the WVO soap. The industrial WVO

soap most likely does not retain the scent of the WVO because the scent reacts in the

saponification reaction.

Note that the used peanut oil bars of soap were from multiple batches of soap,

some of which had additives. These were included in the data analysis as the additives

22

were intended only for coloring purposes, and as such were not anticipated to affect the

characteristics of the bars. Although it is possible that these additives did affect the

characteristics of the bar, the data trends suggest that the properties of the soap were

independent of these coloring additives for all properties except perhaps lather, which has

the widest range of results. All other bars of soap (fresh peanut and soybean oil soaps)

were from one batch of soap, which could result in some of the characterizations of the

soap being more reflective of the batch than the type of oil used to make the soap, as

batches naturally vary to some degree.

Table 3: Characteristics of Industrial WVO vs New Oil Soap

Used peanut Fresh peanut

Average* 95% CI Average* 95% CI

Hardness 3.85 (13) 0.23 3 (1) N/A

Scent 1.89 (9) 0.28 2.00 (5) 0.00

Lather 2.80 (10) 1.01 4.20 (5) 0.56

Conditioning effect 2.00 (10) 0.51 2.30 (5) 1.21

*number in parenthesis indicates the number of measurements averaged

3.4.2. Household WVO

A visual representation of the soap made from household WVO is shown in

Figure 12 (left) below, with clean soybean oil on the right. The soaps appear very similar,

as they have a color that is difficult to differentiate. The clean oil soap (right) appears that

it may be less hard, as there are a few soap shavings on the outside that may have come

off during handling.

23

Figure 12: A comparison of household WVO (left) vs clean oil soaps (right) made with soybean oil.

Table 4 below enumerates the perceived characteristics of the household WVO

soap compared to fresh soybean oil. Household WVO received a 1 for hardness, because

each time when performing the test, the soap splintered into parts instead of the screw

sinking slightly into the soap—i.e. the soap is brittle. The fresh soy soap also received a

low score for hardness (2)—this is lower than peanut (used or fresh) soaps, which

suggests that peanut oil naturally produces harder soaps. The fresh soy soap has a slightly

more positive conditioning effect (3 is neutral effect, less is slightly drying); however,

overall the quality of the soaps was relatively similar between the two conditions.

Table 4: Characteristics of Household WVO vs New Oil Soap Used Soy Fresh Soy

Average 95% CI Average 95% CI

Hardness 1 (1) N/A 2 (1) N/A

Scent 2.00 (4) 0.00 2.0 (4) 0.00

Lather 3.75 (4) 2.00 4.0 (4) 1.52

Conditioning effect 2.25 (4) 0.80 3.0 (4) 0.88

*number in parenthesis indicates the number of measurements averaged

24

4. CONCLUSIONS

4.1 Summary of Results and Conclusions

The usage of the oil has the potential to significantly impact its qualities. For

example, oil used in industrial settings (i.e. long-term, intensive use) experienced a

notable change in properties, including increase in FFA content to approximately 5%, a

significant darkening of color, and the acquiring of scent of fried food. However,

household WVO remained largely the same as fresh oil for all characteristics except for

scent, which readily reached approximately the same scent of industrial WVO.

These changes in the oil had an impact on the quality of the soap that they were

used in. For example, industrial WVO soap was darker in color than soap made from

fresh peanut oil, and was harder; however, fresh peanut oil soap had more lather. The

qualities of scent and condition effect were not significantly affected between the two.

The industrial WVO had the very positive effect of accelerating the saponification

reaction, making it easy to make soap without the use of an electric mixture or the

addition of heat.

4.2 Implications for Soap-Making in Porcón, Peru

We anticipate that the WVO in Porcón, Peru will be similar to WVO created, as

the soybean oil used in the restaurants is discarded daily. As such, the oil will likely still

have the scent of the fried foods (primarily fish and potatoes), will be a slightly darker

color, although will have the same chemical make-up. If this is the case, the WVO will

create soap that is very similar to soap made from fresh soybean oil, although it may be

brittle and have somewhat less lather. These poor qualities may be partially overcome by

25

additions to the soap of salt (for hardness) and sugar (for lather), as well as making soaps

with a mixture of oils instead of one type. These changes could be explored more to

confirm that these changes would be effective. Overall, we anticipate that soap from

WVO in Porcón will give a high-quality product that will appeal to tourists (their

intended use for the soap).

4.2 Recommendations for Further Experimentation

Given limited resources and the time-consuming nature of the data collection, the

quantity of data collected was limited. To give more confidence in the results presented

in this thesis, the effects of usage on vegetable oil quality should be studied more

rigorously. For home use samples, we recommend taking samples as oil is used in frying

from multiple individuals (and cultures) that have assorted styles of frying—and different

foods that are fried. Additionally, for industrial samples, we recommend taking samples

from multiple fryers in the same usage, as well as from different restaurants. A broader

data set would give greater insight into the impact of usage on oil quality, as well as the

types of usage that most drastically affect the oil quality.

Additionally, as the oil types were different in the usage scenarios (peanut in

industrial, soybean in household), comparison between usage impacts between the two

scenarios is not perfectly valid. As such, we recommend sampling oil usage where the

type of oil used is the same. Other studies could also be done to analyze the relative

resistance of several types of oil to breakdown; however, these studies should be done

when comparing similar usage scenarios.

26

Also, characterization of soap properties was done with only 3 individuals; further

testing of the soaps from a varied audience would give greater confidence in the reported

soap characteristics in the report. We also recommend making multiple batches of soap

with the same type of oil to ensure that the characteristics of the soap are not batch-

specific, but are oil-specific.

Finally, additional work could be done to connect some of the properties

discussed above. For example, correlations and relationships could be developed between

the FFA content of the sample, its saturation, and the amount of mixing time for the soap

to reach trace. These correlations would allow for an easy way to predict the performance

of the oil in a soap-making setting.

27

REFERENCES

[1] Đokić M, Kesić Ž, Krstić J, et al. (2012), Decrease of free fatty acid content in

vegetable oil using silica supported ferric sulfate catalyst. Fuel 97:595–602. doi:

10.1016/j.fuel.2012.03.039.

[2] (2017) Vegetable Oils and Animal Fats. In: EPA. www.epa.gov/emergency-response/.

Accessed 27 Mar 2018.

[3] (2016) El aceite de cocina tiene futuro. In: LaRepublica.pe. larepublica.pe/domingo/.

Accessed 27 Mar 2018.

[4] Historia y Cultura. In: Granja Porcon. www.granjaporcon.org.pe. Accessed 27 Mar

2018.

[5] Ejemot-Nwadiaro RI, Ehiri JE, Arikpo D, et al. (2015), Hand washing for preventing

diarrhoea. Cochrane Database of Systematic Reviews. doi: 10.1002/14651858.cd004265.

[6] Đokić M, Kesić Ž, Krstić J, et al. (2012), Decrease of free fatty acid content in

vegetable oil using silica supported ferric sulfate catalyst. Fuel 97:595–602. doi:

10.1016/j.fuel.2012.03.039.

[7] Hazeltine B (2001) Chapter 7 - Household Technologies. In: Bull C (ed) Field Guide

to Appropriate Technology, 1st edn. Elsevier Science & Technology, pp 684–687.

[8] Beck L (2017) 'Smoke point' matters when cooking with oil. In: The Globe and Mail.

www.theglobeandmail.com. Accessed 27 Mar 2018.

[9] Wang T (2011) Soybean Oil. In: Gunstone FD (ed). Vegetable Oils in Food

Technology: Composition, Properties and Uses, 2nd edn. Wiley-Blackwell, Ames, IO, pp

59–105.

28

[10] Blair G Titrating Oil. In: Utah Biodiesel Supply. www.utahbiodieselsupply.com.

Accessed 27 Mar 2018.

[11] Krzywinski M Image Color Summarizer. In: Image Color Summarizer - RGB and

HSV Image Statistics. http://mkweb.bcgsc.ca/color-summarizer/. Accessed 3 Apr 2018.

[12] Dunn KM (2010) Scientific Soapmaking: The Chemistry of the Cold Process.

Clavicula Press, Farmville, VA.

29

APPENDIX

Table 5: Summary of NaOH (g) to Titrate 1 mL of Each Oil Sample and Corresponding FFA% Industrial Samples

Household Samples

Sample NaOH

(g)

Average

NaOH

(g)

Average

FFA%

Sample NaOH

(g)

Average

NaOH

(g)

Average

FFA%

0 0.199

0.199 0.153

0 0.257

0.404 0.311 0.199 0.551

1 0.361

0.353 0.271 1 0.304

0.493 0.379 0.344 0.682

2 0.549

0.485 0.373 2 0.388

0.452 0.348 0.42 0.516

3 0.888

0.877 0.675 3 0.377

0.339 0.261 0.866 0.301

4 0.882

0.924 0.710 4 0.47

0.504 0.388 0.965 0.539

5 1.402

1.389 1.068 5 0.436

0.431 0.331 1.375 0.425

6

1.646

1.501 1.155 6

1.199 0.908 0.698

1.659 0.617

1.199 7

0.674 0.712 0.548

9 4.06

3.873 2.979 0.751

3.686 8

0.737 0.492 0.378

10 1.876

1.925 1.481 0.246

1.974 9

0.595 0.584 0.449

17 4.739

5.412 4.163 0.573

6.084

10

0.155

0.224 0.173 15

3.437 3.362 2.586

0.051

3.286 0.467

18 4.848 4.552 3.501 WVO 0.456 0.417 0.320

30

4.255 0.377

19 3.781

3.812 2.932

3.842

21 4.361

4.615 3.550 4.869

22 5.536

5.398 4.152 5.26

23 5.291

5.128 3.944 4.964

25 5.66

5.400 4.154 5.14

26 5.159

4.717 3.628 4.275

WVO 8.889

8.754 6.733 8.618

31

Table 6: Summary of Average HSV Values for Industrial and Household Use Oil Samples Industrial Samples

Household Samples

Sample H S V

Sample H S V

0 36 8 69

0 35 11 67

1 44 23 70

1 39 13 67

2 46 33 72

2 37 15 67

3 46 45 71

4 39 24 67

4 45 52 70

5 39 23 67

5 46 62 72

6 41 23 67

6 46 60 74

7 41 26 69

9 45 56 73

8 41 28 68

10 45 59 71

9 41 25 68

15 44 69 75

10 42 29 69

17 43 78 69

11 43 37 69

18 43 82 72

19 44 75 71

21 42 82 71

22 42 82 71

23 40 90 72

25 40 90 73

26 40 88 74

31 21 89 59

32

Table 7: Summary of Scent Test Perception Numbers for Industrial and Household Use Oil Samples

Industrial Samples Household Samples Sample 1 2 3 4 Average Sample 1 2 3 4 Average

0 5 5

5

0 5 5

5

1 3 4

3.5

1 3 2

2.5

2 2 2

2

2 3 3

3

3 5 4

4.5

3 4 4

4

4 2 2

2

4 3 5 3 4 3.75

5 2 3

2.5

5 4 4

4

6 3 3

3

6 3 4

3.5

9 5 4

4.5

7 2 2

2

10 2 3

2.5

8

15 4 2 4 3 3.25

9 4 3

3.5

17 2 2

2

10 3 2

2.5

18 2 4 2 2 2.5

11 2 2

2

19 3 4

3.5

21 2 3

2.5

22 2 2

2

23 3 1 3 3 2.5

25 3 2

2.5

26 1 2

1.5

31 1 1

1