a study on the production of soap based on tangerine peel essential oils

THAI NGUYEN UNIVERSITIES UNIVERSITY OF AGRICULTURE AND FORESTRY DANG MAI HUONG A STUDY ON THE PRODUCTION OF SOAP BASED ON TANGERINE PEEL ESSENTIAL OILS BACHELOR THESIS Thai Nguyen, 2023.

THAI NGUYEN UNIVERSITIES

UNIVERSITY OF AGRICULTURE AND FORESTRY

DANG MAI HUONG

A STUDY ON THE PRODUCTION OF SOAP BASED ON TANGERINE PEEL ESSENTIAL OILS

BACHELOR THESIS

Thai Nguyen, 2023

Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor of Food Technology Student name Dang Mai Huong

Tangerine peel with experiments to determine the optimal points of material – water ratio, NaCl concentration, extraction temperature, and extraction time Particularly, to produce a maximum volume of 1.81 ml Tangerine peel essential oils, the hydro-distillation operation requires a material – water ratio of 1:5 g/ml, a NaCl concentration in the water of 2%, an extraction temperature of 105oC, and an extraction time of 120 minutes The essential oils were then incorporated in a cold process of soap making to produce soap bars After sensorial tests to determine the suitable ingredients and their amounts, the process was completed with palm oil as the oil for saponification, 2% of Tangerine peel essential oils, 2% of turmeric powder as colorant, and 3% of glycerol This formula gave an excellent quality soap bar with a total sensorial score of 18.80/20 Most of the attributes meet the Keywords: Tangerine peel; essential oils; extraction; saponification

Number of pages: 70

Date of Submission: 16/08/2023

ACKNOWLEDGEMENT

I feel obliged, yet honored to acknowledge that this thesis and all the research work were completed thanks to the great effort and support from many individuals and collectives

First, as my supervisor, Dr Pham Bang Phuong had passionately been providing numerous informative and helpful approaches and advices, which were keys to the completion of this study It has been one of my greatest honors having worked under his supervision For that, I am really grateful

I also want to deliver my utmost gratitude to the Faculty of Biotechnology – Food Technology in Thai Nguyen University of Agriculture and Forestry, particularly all the personnel including the lecturers and the officials The facility as well as the instructions I received during my work were enlightening as they showed me interesting yet practical perspective of the future career that I am pursuing Furthermore, the faculty’s enthusiasm made me feel really comfortable and appreciated

In addition, during my research, I had also received much needed help and support from my family, seniors, and friends I would like to express my sincere thanks to them

Wish us all the best!

DANG MAI HUONG

1.4 Limitations 6

CHAPTER II LITERATURE REVIEW 8

2.1 Overview of soap products 8

2.1.2 General information 8

2.1.2 Materials for soap production 9

2.1.3 The effects of soap products 11

2.2 Soap production techniques 12

2.2.1 Popular process of saponification 12

2.2.2 Industrial production chain 14

2.3 Tangerine peel 15

2.3.1 General information 15

2.3.2 Beneficial effects of mandarin peel essential oil 15

2.3.3 Extraction of essential oil 16

2.4 Status of research on the interested subjects 18

2.4.1 Research status on the world scale 18

2.4.2 Research status on the Vietnamese scale 19

2.4.3 Status of the soap market 20

2.5 Assessment on literature review 20

3.4 Experiment design and method 25

3.4.1 Essential oil extraction method 25

3.4.2 Soap making method 29

3.4.3 Output evaluation 34

3.4.4 Product finalization 36

3.5 Data analysis 37

PART 4 RESULT AND DISCUSSION 38

4.1 Optimization of the Tangerine peel essential oil extraction 38

4.1.1 The material – water ratio 38

4.1.2 The NaCl concentration in the water 39

4.1.3 The extraction temperature 41

4.1.4 The extraction time 42

4.2 Determination of the ingredients for soap making based on

Tangerine peel essential oils 44

4.2.1 The oil for saponification 44

4.2.2 The proportion of Tangerine peel essential oils 45

4.2.3 The proportion of colorant 47

4.2.4 The proportion of glycerol 48

4.3 Evaluation of the output soap based on the criteria of TCVN 2224:1991 49

LIST OF FIGURES

Figure 2.1 The saponification reaction between a fatty molecule and an alkali 8 Figure 2.2 Industrial production process of soap bar products 14 Figure 3.1 Cao Bang Tangerine and the peel 22 Figure 3.2 The cold process of hydro-distillation for extracting essential oil 26 Figure 3.3 The cold process of soap making applied in this study 30 Figure 4.1 The essential oils extracted from Tangerine peel

with different material – water ratios 39 Figure 4.2 The essential oils extracted from Tangerine peel

with different NaCl concentrations 40 Figure 4.3 The essential oils extracted from Tangerine peel

with different temperatures 42 Table 4.4 The amount of essential oils extracted using different ranges of time for extraction 42 Figure 4.4 The essential oils extracted from Tangerine peel

with different points of time 43

LIST OF TABLES

Table 3.1 Instruments and laboratory equipment used in the study 23

Table Error! Use the Home tab to apply 0 to the text that you want to appear here Chemicals used in the study 24

Table 3.3 The investigated points of material – water ratios

for Tangerine peel essential oil extraction 27 Table 3.4 The investigated points of salt concentration in the water

for Tangerine peel essential oil extraction 27 Table 3.5 The investigated points of extraction temperature

for Tangerine peel essential oil extraction 28 Table 3.6 The investigated points of extraction time

for Tangerine peel essential oil extraction 28 Table 3.7 The tested types of oil for saponification 31 Table 3.8 The tested proportion of Tangerine peel essential oil 31 Table 3.9 The amount of turmeric powder added in the saponification process 31 Table 3.10 The amount of glycerol added in the saponification process 32 Table 3.11 The sensorial score of different quality levels 33 Table 3.12 The criteria for toilet soap product based on TCVN 2224:1991 34 Table 4.1 The amount of essential oils extracted

using different material – water ratios 38 Table 4.2 The amount of essential oils extracted

using different NaCl concentrations in water 39 Table 4.3 The amount of essential oils extracted

using different temperatures for extraction 41

Table Error! Use the Home tab to apply 0 to the text that you want to appear here The amount of essential oils extracted

using different ranges of time for extraction 41 Table 4.5 Sensorial score of different types of oil for soap making 44 Table 4.6 Sensorial score of different amount of Tangerine peel essential oils added in soap making 46 Table 4.7 Sensorial score of different amounts of turmeric powder

added in the process 47 Table 4.8 Sensorial score of different amounts of glycerol added in the process 48 Table 4.9 Test results on the criteria for a toilet soap product

based on TCVN 2224:1991 49 Table 4.10 Description of the Tangerine peel essential oils-based soap product 52 Table 4.11 The estimated price of a Tangerine peel essential oils-based soap bar 53

CHAPTER I INTRODUCTION 1.1 Research and rationale

World population increasing along with the social complexity is creating numerous challenges for humanity One of them is the issue of personal hygiene The dense populations become a potential source of spreading infectious diseases (Jaul & Barron, 2017) The COVID 19 pandemic that ravaged the world since 2020 started from China, the world’s most populated country Furthermore, the pandemic occurred more severely in densely populated countries Another example is the Ebola outbreak from 2013 – 2016, which was the spreading of a fatal viruses in Africa, a region with many people but poor health facilities The large population also makes access to health care much more difficult, especially in developing countries (Dyett & Thomas, 2019; Greguš & Guillebaud, 2020) In Vietnam, the phenomenon in which hospitals were overloaded has been recorded in many advanced medical centers for years Furthermore, when the quality of small regional health care centers cannot meet the demand, such a phenomenon becomes more serious as people from afar move to provincial hospitals These consequences have set a new demand for quick health care products, further improving the ability to protect the health of oneself From this demand, a new foundation for personal care products was set, making ways to not just research and development but also an entire new market

Personal care products like soap or hand sanitizer are the priority when it comes to personal hygienic issues They are potent disinfectants that are capable of eliminating microbes while cleaning the human body Amidst the COVID pandemic in 2021, the consumption of personal care products sky-rocketed

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(Chowdhury et al., 2020) They played a significant role in preventing the further spread of the disease Furthermore, this line of products even provides aesthetic values, including body fragrance, skin feel, and comfort In reality, the need for personal care products has been rising these years as more and more diseases emerge while the awareness of people toward hygiene is constantly raised (Knowles et al., 2020) While the market has been stuck with recurring types of hand sanitizers made of a fat and an alkali added with chemical fragrance, this sets a new requirement of renewing this product line for the global market, in general, and the Vietnamese market, in particular As a result, research for new types of personal care products like soap is definitely a relatively comprehensive solution

Recently, the demand for organic or natural-based products is becoming a major concern on a global scale The soap line is not an exception New products such

as soap derived from bitter melon (Momordica charantia) or cinnamon (Cinnamomum verum) have been introduced and received positive feedback from

customers They were proved to be potent at both cleaning and providing special benefits like unique fragrance or skin soothing effects However, there is still much potential to exploit in terms of natural-based soap products in the scene where Vietnam is a tropical country that hosts various valuable herbs and plants A new soap derived from a new natural ingredient would not only solve the need for the personal care product market that is rising but also create more options for customers while utilizing local specialties Based on the aforementioned

rationales, the “Study on the production of soap based on Tangerine peel

essential oils” was selected for execution

1.2 Research’s objectives

There were 04 specific objectives of this study:

+ Distill and retrieve the essential oils from Cao Bang Tangerine peels

+ Investigate the production process for a soap product incorporated with the Tangerine essential oils

+ Evaluate the output product in terms of sensorial properties and storability

+ Design the package for the soap product and execute calculations for commercialization

1.3 Research questions and hypotheses

This study was conducted based on the following hypotheses and questions: + Question 1: What are the optimal conditions for extracting tangerine peel essential oil using industrial scale methods?

This question led to many hypotheses regarding the suitable methods for essential oil extraction in this study Hydro-distillation and cold press were among the most prominent considerations In addition, there were hypotheses regarding the default points of research for finding optimal factors

+ Question 2: Is tangerine peel essential oil suitable for making a soap product? Question 2 also referred to the methods for making soap and the hypothesis of suitability for incorporating tangerine peel essential oil to a soap formula

1.4 Limitations

Despite the utmost effort of the implementer as well as the supervisors, this study remains with few limitations that require much help, comments, and recommendations from the instructors, lecturers, and experts in the field Here

are the most eminent limitations that the implementation of this study encountered:

+ Research capabilities: The implementer had studied both theoretical foundations and realistic foundations before conducting research protocols However, there are still limitations that may impede accuracy or further achievement of this project

+ Differences in approaching: The approaches that this study had selected possess many differences compared to many methods used by many studies in the same fields That is why there was a lack of comparative means, which could reduce the objectivity of the findings from this study

+ Variable instruments: Instruments used in this study also affected the results and also reduced the range of comparisons with other articles The depreciation of the instruments should also be considered in limitations of not just this study but also many others

+ Risk management: The study had employed a few methods to manage the risks while implementing research However, it is difficult to achieve an absolute result and there was definitely likelihood of error

CHAPTER II LITERATURE REVIEW 2.1 Overview of soap products

2.1.2 General information

In the Vietnamese standards, “Soap” refers to many different types of product lines This study was focusing on the soap bar for personal care (toilet soap – according to TCVN 2224:1991) In terms of chemistry, “soap” is a result of the saponification process occurring due to the reaction between fat or oil and a strong alkali like Sodium Hydroxide (NaOH) or Potassium Hydroxide (KOH) The reaction is showed in Figure 2.1 below:

Figure 2.1 The saponification reaction between a fatty molecule and an alkali

Based on the reaction in Figure 2.1, it is clear that the nature of the saponification process is a simple reaction between an ester and an alkali, creating a salt and an alcohol (glycerol) The salt has the characteristics of a detergent when it can cover the dirty molecule while also exerting hydrophilic properties, creating the rinsing effect with the flow of water to remove the dirt Furthermore, according to the study of Giuliano & Rybak (2015) on the anti-microbial mechanism of

soap products, the soap molecules can also disrupt the cell membrane of microbes

The secondary product of this process is glycerol According to Milani & Sparavigna (2017), it is commonly used in skincare and cosmetic products due to its excellent moisturizing properties It helps to attract and retain moisture in the skin, keeping it hydrated and supple Additionally, glycerol has humectant properties, meaning it can draw moisture from the air, further enhancing its moisturizing effects (Azelee et al., 2019) Beyond skincare, glycerol is also utilized in food and pharmaceutical industries, as a solvent, sweetener, and preservative Its wide range of applications makes glycerol a valuable and multifunctional compound

2.1.2 Materials for soap production

The two compulsory ingredients for making soap are the fat (oil) and the alkali to take part in saponification There are also other ingredients employed for the process Specifically:

+ Theoretically, any type of fat or oil can be usable to make soap However, each type exerts distinct properties, making only a few suitable for the demand of customers in the market nowadays In the soap industry, especially in the Vietnamese market, there are 02 types of popular oils used for soap: coconut oil and palm oil The study of Boateng et al in 2016 compared these two types of oils in terms of soap making potential and showed that the coconut In addition, the study of Félix et al (2017) had indicated the use of animal fats, sesame oil, olive oil, and even the oil wasted from cooking in soap production

+ Regarding the alkali, there are 02 possible types: Potassium Hydroxide (KOH) and Sodium Hydroxide (NaOH) The difference in terms of saponification value (the saponification efficacy and the resulting salt) makes KOH a suitable alkali for liquid soap while NaOH is often used for soap bars a (Sousa et al., 2010) In the past, these two alkali for making soap were obtained from a process called leaching According to the description of Tukey Jr (1970), leaching involves the use of water to extract water-soluble compounds from the ash of hardwood trees like birch and oak These trees possess potassium and sodium carbonates, which create alkali in water Nevertheless, this technique is outdated Nowadays, most soap making manufacturers employ industrially-produced NaOH to make hand soap bars This compound can also be easily purchased on many platforms + Water is actually a mandatory ingredient for making soap It is responsible for dissolving the alkali According to the book “Basic soap making” of Letcavage (2009), the amount of water affects significantly on the formation and the texture of soap bars Furthermore, it also creates a medium for the addition of other ingredients

+ Additives and other ingredients have gradually become an essential part of soap making According to the books of Letcavage (2009) and Pierce (2013) on the recipe of soap making, the additives are often fragrances, colorants, exfoliants moisturizers, and preservatives In the studies of Rios (2016) and Dhakad et al (2018), which incorporated herbal essential oils into soap making, it was showed that essential oils often played roles as fragrances Some also exert properties of colorants or even provide anti-oxidation properties

2.1.3 The effects of soap products

Personal care soap products play a crucial role in maintaining hygiene and promoting overall well-being The article of Aiello et al (2008) on hand soap products showed that from a hygienic perspective, these products effectively remove dirt, oil, sweat, and impurities from the skin's surface By lathering and rinsing with soap, the natural oils and debris accumulated throughout the day are gently washed away, leaving the skin clean and refreshed This cleansing action helps to reduce the buildup of bacteria, germs, and pollutants, thereby minimizing the risk of infections and skin-related issues Regular use of soap also aids in the prevention of body odor, ensuring that individuals feel fresh and confident throughout the day

Beyond the hygienic benefits, personal care soap products offer aesthetic effects that contribute to an individual's overall appearance and self-care routine Soap formulations often incorporate ingredients like moisturizers, vitamins, and botanical extracts, providing nourishment and hydration to the skin These ingredients help to maintain the skin's natural moisture balance, keeping it soft, smooth, and supple Soap products designed for specific skin types or concerns, such as acne-prone or sensitive skin, offer targeted benefits, assisting in the management of these conditions Additionally, scented soap variants add a sensory delight to the bathing experience, with a wide array of fragrances available to suit personal preferences These have been reflected well in the study of McGhee et al in 2019 on the roles of hand soap amidst the COVID 19 pandemic

Regular use of personal care soap products promotes skin health and enhances the aesthetics of the body (McGhee et al., 2019; Dover et al., 2020) Clean, well-maintained skin contributes to a positive self-image and boosts self-confidence The tactile experience of lathering soap on the body, combined with the fresh and pleasant fragrances, can also evoke a sense of relaxation and rejuvenation, turning a simple daily task into a moment of self-care It is important, however, to select soap products that are suitable for individual skin types and to follow proper cleansing routines, as excessive or improper use may lead to dryness or irritation

2.2 Soap production techniques

2.2.1 Popular process of saponification

2.2.1.1 Hot process and cold process

The cold process is considered the fundamental protocols of soap making It covers from the input ingredients to the output product First, the process requires the mixing between the alkali and the water Afterward, the alkali solution is poured in the oil and the batch is stirred to achieve the “trace” state (thickening) At this state, the other ingredients and additives are added and the stirring continues to evenly distribute the ingredients Subsequently, the mixture is poured into molds, covered with an insulation layer and let sit for about 1 – 2 days for the soap to solidify Finally, the soap is cut into bars and the bars are cured for a few weeks for the soap to fully hardened and dried During the blending of materials and saponification process, precautionary practices such as wearing a goggle or use gloves are required as the alkali solution is often caustic materials (Eroglu et al., 2012).This process has been proved to be suitable for

small scale production like households, individuals, and laboratory purposes (Maotsela et al., 2019; Ott, 2021) The study of Maotsela et al even showed that the cold process can potentially utilize wasted cooking oil and tallow to produce toilet soap However, the inherent disadvantage of the cold process is that it takes too much time for the soap to be cured (30 days) Furthermore, there is a risk of contamination as during the drying and curing process, the soap is exposed to the environment

The hot process is considered a solution for the weakness of the cold process Most of the steps remain similar to the cold process but heat is applied during saponification and curing, making the production faster Nevertheless, the hot process contains a risk of damaging additives as it involves high temperatures (Furtado & May, 2004) Furthermore, the hot process also requires more in terms of equipment and techniques

2.2.1.2 Melt & pour and re-batching process

Melt & pour and re-batching are the two techniques of soap making that employ pre-made soap bases or soap bars In other words, these two techniques do not require saponification In both techniques, the pre-made soap is melted to a liquid state and additional ingredients are added to the solution The operation is relatively simple with an advantage of avoiding the saponification process, which is relatively difficult to control and can be risky The difference between these two soap making method is that melt & pour employs pre-made soap bases (Browning, 2002; Saxton et al., 2013) As a result, this technique highly facilitates customization for the soap and is often used to investigate the compatible of preservatives and other ingredients like herbal extracts and

essential oil On the other hand, re-batching uses pre-made soap bars instead of bases, according to Melina Coss with the book about handmade soap (2016) Therefore, the newly formed soap still contains properties of the previous soap, creating exotic colors and marbling effects on the soap

2.2.2 Industrial production chain

Soap production on industrial scales often involves a large volume of ingredients in one batch as well as the automation required for lowering production costs Depending on the desired type of soap or, input ingredients, available facilities and instruments, and even regional cultures, the production chain may vary significantly among different manufacturers Nevertheless, the general soap making process can be summarized via Figure 2.2 below:

Figure 2.2 Industrial production process of soap bar products

It can be seen that the production process on industrial scales is an adaptation from the hot process of soap making

2.3 Tangerine peel

2.3.1 General information

Tangerine (Quýt, Citrus reticulata) is a popular fruit in Vietnam and many Asian

countries like China and India As indicated in the scientific name, Tangerine belongs to the Citrus family with notable members like Orange and Lemon The pulp of this fruit is delicious and offers many health benefits like anti-oxidation and immunology enhancement (Yu et al., 2014) The season for harvesting often lasts for a few months from November The consumption market of Tangerine in Vietnam is considerably large when according to the Department of Statistics, the market had consumed over 10,000 tons of the fruit in 2021

Nevertheless, the subject of interest in this study is not the pulp of Tangerine but the peel According to the study of Singh et al (2020), the peel of Tangerine resembles many other types of Citrus fruit peel It has a diverse profile of phenolic compounds and flavonoids, which exert many beneficial bioactivities like anti-oxidation, anti-inflammation, and cardiovascular supporting effects More remarkably, this is a rich source of essential oils The studies of Johnson et al (2013) and Denkova-Kostova et al (2021) on the constituents of Tangerine peel essential oils showed that the main volatile compounds included D-limonene and cis-cinnamaldehyde as the two main constituents, along with some other minor compounds like α-pinene and β-pinene

2.3.2 Beneficial effects of mandarin peel essential oil

Tangerine peel essential oil, derived from the outer peel of Citrus reticulata,

offers a range of beneficial effects that make it a popular choice in aromatherapy and skincare With its sweet, citrusy aroma and diverse therapeutic properties,

Tangerine peel essential oil provides numerous advantages for physical, mental, and emotional well-being First, Tangerine peel essential oil possesses uplifting and calming properties (Mirghafourvand et al., 2016; Kwangjai et al., 2021) The refreshing scent has been shown to promote relaxation, reduce stress, and alleviate anxiety Inhaling the aroma of this oil can help create a sense of tranquility and improve mood, making it a valuable tool for managing stress and promoting overall mental well-being Tangerine peel essential oil is renowned for its skin-enhancing properties (Kammoun Bejar et al., 2011; Gbaj et al., 2019) It exhibits excellent cleansing and purifying qualities, making it a popular ingredient in skincare products The oil helps to promote a clear, healthy complexion by minimizing the appearance of blemishes and supporting a balanced skin tone It also possesses mild astringent properties that can help tighten the skin and reduce the appearance of pores Additionally, the antimicrobial properties of Tangerine peel essential oil further contribute to its beneficial effects (Kirbaşlar et al., 2009) It possesses natural antibacterial and antifungal properties that can help combat harmful microorganisms Incorporating this oil into personal care products or diffusing it in the air can help purify the environment and support a clean, germ-free atmosphere It is obvious that these benefits of Tangerine peel essential oils are compatible to those that a personal care product like hand soap would provide to its customers

2.3.3 Extraction of essential oil

There are numerous methods of extracting volatile compounds out of a plant The most notable ones include hydro-distillation, enfleurage, and cold pressing The details of these methods are as follows:

+ Hydro-distillation is a traditional method used to extract essential oils from plant materials According to the study of Golmakani & Rezaei in 2008 on the method, it involves the use of water and heat to generate steam, which passes through the plant material, carrying the volatile essential oil compounds The steam is then condensed, separating the essential oil from the water, resulting in the final product

+ Enfleurage is an ancient technique used to extract fragrant compounds from delicate flowers that are too sensitive for traditional extraction methods (Soe’eib et al., 2017) It involves placing flower petals on a layer of fat, such as animal fat or vegetable oil, allowing the volatile compounds to infuse into the fat over time The fat is then repeatedly replenished with fresh petals until saturation Finally, the fragrant fat is washed with alcohol to separate the essential oil, resulting in a highly concentrated floral extract Enfleurage is a labor-intensive process and is less commonly used today compared to other extraction methods

+ According to “a review on cold press in oil extraction” of Cakaloglu et al (2018), cold pressing is a method used to extract essential oils from citrus fruits, such as oranges, lemons, or grapefruits It involves mechanically pressing or squeezing the outer rind of the fruit to release the essential oil The fruit is typically first punctured or scored to facilitate the oil's release This method does not involve heat or solvents, allowing for a more natural extraction process The resulting essential oil is typically highly aromatic and retains the characteristic scent of the citrus fruit Cold pressing is

commonly used for obtaining citrus essential oils due to its simplicity and ability to preserve the fragrance of the fruits

There are also a few other techniques used for extracting essential oils such as solvent extraction, super-critical fluid extraction, and maceration

2.4 Status of research on the interested subjects

2.4.1 Research status on the world scale

The research status on extracting essential oils in the world has reached advanced points for many different types of plant, including citrus relatives such as Tangerine Particularly, the studies of Xiong & Chen (2020) and Rajput et al (2022) had extracted essential oils from Tangerine from China and India, respectively, using super-critical CO2 as the solvent They both showed the potency of this technique as the temperature needed for the operation as well as the time is significantly lower compared to other techniques like solvent extraction and hydro-distillation The two studies also succeeded in identifying the composition of the essential oils and the bioactivities that the oils offer Supercritical fluid extraction is also favored by many other studies that extract Tangerine essential oils and characterize the extract (Chen & Huang, 2016; Rosa et al., 2019)

Other techniques also showed great promises in Tangerine peel extraction studies In Mexico, Dugo et al (2005) characterized the Tangerine essential oils using cold pressing for extraction The extract was showed to have a higher content of limonene, while γ-Terpinene, myrcene and α-pinene were the other most abundant hydrocarbons Zhao et al (2022) employed hydro-distillation and needed a material – solvent ratio of 1:17 g/ml, room temperature, and an

extraction time of 4 hours to yield the maximum amount of essential oils out of Tangerine peel Bustamante et al (2016) extracted the essential oils using hydro-distillation with the support of microwave and pressure The operation included a material – solvent ratio of 1:1.5 g/ml and the extraction time of only 20 minutes, greatly reduced compared to the conventional hydro-distillation in the study of Zhao et al (2022) Recently, the study of Rashed et al (2023) had successfully employed a complex two-phase extraction method with the assistance of not just microwave but also enzyme treatment The yield was significantly high with large size of D-limonene detected in the extract as well as the optimal creaming index and minimal degradation rate

2.4.2 Research status on the Vietnamese scale

In Vietnam, scientific research on the extraction of Tangerine essential oils escalated in the recent 5 years with the domination of hydro-distillation The study of Trần et al (2019) study the effect of hydro-distillation and extracted essential oils composed of limonene (97.655%), followed by β-Myrcene (1.395%), 1R-α-Pinene (0.561%), L-β-pinene (0.264%), and Sabinene (0.126%) The operation included a material – solvent ratio of 1 g/4 ml of water, a temperature of 110oC – 120oC, and an extraction time of 150 minutes In the next year, Ngô et al (2020) utilize the support of microwaves in the hydro-distillation technique to extract Tangerine essential oils The results showed a great influence of 600 W microwave assistance when the material – solvent ratio was only 1 g/3 ml of water and the extraction time was only 55 minutes Through gas chromatography – mass spectrometry, the essential oils extracted from this study was showed to resemble the components in the study of Trần et al with limonene

(97.688%), sabinene (0.12%), β-myrcene (1.394%), (-)-β-pinene (0.273%), and 1R-α- pinene (0.525%) These studies have laid foundations for some Tangerine essential oil products on the Vietnamese market (Figure 2.3)

2.4.3 Status of the soap market

Recently, a new brand of organic-based soap products has emerged in the Vietnamese market The brand is called “sinh dược” with many different types of

hand soap that derive natural extracts, such as cinnamon (Cinnamonum verum), bitter melon (Mormodica charantia), and turmeric (Curcuma longa) These

products received much positive feedback from customers and often recorded high sales every month The brand has also been expanding to other product lines such as bath salts, fragrant essential oils, and organic-based detergents In addition to “sinh dược”, there are also few minor brands that offer organic soaps such as bamboo ash-based hand soap and sesame-based hand soap Nevertheless, the market has not recorded the introduction of any Tangerine peel essential oil-based soap product

2.5 Assessment on literature review

+ The nature of soap production is relatively simple with only the saponification reaction between fat and an alkali The products of such a process including glycerol and soap are utilizable in many ways, making a foundation for research and development The soap product line is also in a high demand from the market, especially in Vietnam Along with the increasing need for organic-based products, this is a huge opportunity for a new type of product

+ The materials for soap making are not difficult to reach with primarily many options for oils and even the alkali solution Additional ingredients and various

types of preservatives have also been proved feasible Furthermore, there have also been many studies regarding the production process of soap products with comprehensible operation

+ Tangerine peel is a relatively abundant material in particularly the Vietnamese market The essential oil of this material has many beneficial effects on the skin, which are compatible to the purposes of a hand soap products Furthermore, the research status has showed the feasibility of combining herbal essential oil in personal care products like hand soap

+ The realistic market of the hand soap product line remains limited in terms of options and variations for customers Furthermore, organic-based products are still considered a foreign term at supermarkets and grocery stores There is no soap products that derive the citrus essential oils, not to mention Tangerine peel’s alone Therefore, this is an opportunity for the development of a soap product based on Tangerine peel essential oil

CHAPTER III MATERIALS, RESEARCH CONTENT AND METHODOLOGY

3.1 Material

3.1.1 Material preparation

The Tangerine was collected from Cao Bang Province The pulp was then separated from the peel Subsequently, the peel was washed in tap water to remove foreign materials on the skin Finally, the peel was stored in cold temperatures (0 – 5oC) or cut into small pieces (3 cm x 1 cm) for immediate essential oil extraction

Figure 3.1 Cao Bang Tangerine and the peel

The oils to make soap included coconut oil, palm oil, and olive oil, which were purchased from local markets As these items are vulnerable to oxidation, they were stored in carefully sealed bottles at a cool and dry place, avoiding direct sunlight

In addition, the study also employed some plastic containers and other laboratory instruments like glass stirrer, glass test tubes, filtering paper, etc

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3.1.4 Research scale

The study was conducted on a laboratory scale located in the Faculty of Biotechnology – Food Technology – Thai Nguyen University of Agriculture and Forestry, Thai Nguyen City, Vietnam

Research period: 30/03/2022- 20/07/2022

3.2 Research content

There were 04 research contents in this study:

Content 1: Study the optimal conditions for the extraction of Tangerine peel

essential oil This study was to:

- Determine the optimal material – water ratio

- Determine the optimal concentration of NaCl in the water

- Determine the optimal temperature for distillation - Determine the optimal distillation time

Content 2: Study the conditions and the ingredients for the soap production process, this content included:

- Determine the appropriate type of fatty oil for saponification - Determine the appropriate proportion of the added essential oil - Determine the appropriate additives and proportion

Content 3: Investigate the quality of the output essential oil-based soap This

content consisted of the headlines in TCVN 2224:1991

Content 4: Finalize the production process of the essential oil-based soap In this

content, there were 02 activities:

- Complete the production process of the soap - Calculate the expected cost and price for a soap unit

3.3 Method

3.3.1 Essential oil extraction method

The study employed the Hydro-distillation method for extracting the essential oil out of Tangerine peels (Bustamante et al., 2016) This method uses water as the solvent, which ensure the safety of the extract for consumption or direct usage on the human body The costs for extraction using this way are also more affordable Furthermore, hydro-distillation is applicable on industrial scale

The operation of the hydro-distillation technique is relatively simple The ingredients (Tangerine peel) was submerged in salted water for 2 hours The ratio between the water and the ingredients was fixed Afterward, the mixture was installed in a pressure cooker to initiate distillation at a certain temperature and for a certain amount of time After condensing the vapor coming from distillation, the liquid was separated using a separating funnel to achieve the essential oil

Subsequently, the raw oil was purified using Na2SO4 5% The purified oil was obtained after filtering the salt and all the sediments resulting from the previous step All the process can be summarized in Figure 3.2 as follows:

Figure 3.2 The cold process of hydro-distillation for extracting essential oil

Based on such operation, the study had set 04 adjustable parameters including the material – water ratio, the concentration of NaCl, the distillation temperature, and the distillation time Preliminary tests had given the default conditions of material – water ratio of 1:3 (v/w), the NaCl concentration of 1%, the temperature of 110oC, and the time of 90 minutes The 04 parameters for optimization as well as the investigated range are showed below:

+ The ratio between the material (Tangerine peel) and water:

Table Error! Use the Home tab to apply 0 to the text that you want to appear here The investigated points of material – water ratios

for Tangerine peel essential oil extraction Formula Material – water ratio (v/w)

+ The concentration of NaCl in the water:

Table Error! Use the Home tab to apply 0 to the text that you want to appear here The investigated points of salt concentration in the water

for Tangerine peel essential oil extraction

F7 3%

+ The distillation temperature:

Table Error! Use the Home tab to apply 0 to the text that you want to appear here The investigated points of extraction temperature

for Tangerine peel essential oil extraction

Table Error! Use the Home tab to apply 0 to the text that you want to appear here The investigated points of extraction time

for Tangerine peel essential oil extraction Formula Material – water ratio (v/w)

order to determine the most appropriate point of the parameter, the experiment measured the essential oil volume resulting from the distillation process

3.3.2 Soap making method

3.3.2.1 The cold process for soap production

The cold process of soap making of the study Warra et al (2010) was selected with few minor modifications as this method provides more control over the operation as well as the use of ingredients Furthermore, the process also suits the facility where this study was conducted All the steps are showed in Figure 3.2 below:

Figure 3.3 The cold process of soap making applied in this study

There were 04 factors selected for examination, which are showed with their investigated points as follows:

+ The type of fat/oil suitable for saponification

Table Error! Use the Home tab to apply 0 to the text that you want to appear here The tested types of oil for saponification

Formula Type of oil

+ The amount of additive (turmeric powder) added in the process:

Table Error! Use the Home tab to apply 0 to the text that you want to appear here The amount of turmeric powder added in the saponification process

Formula Proportion (%)

+ The amount of additive (glycerol) added in the process:

Table Error! Use the Home tab to apply 0 to the text that you want to appear here The amount of glycerol added in the saponification process

+ Texture (Weight factor 1): Determine externally by observation over the soap bar to check homogeneity, any cracks, or color anomalies

+ Color (Weight factor 0.8): Cut the soap bar into a half with a sharp knife Observe the cut section to check for color homogeneity

+ Odor (Weight factor 1): Smell the odor from the cut section of the soap bar

+ Skin feel (Weight factor 1.2): Add water on the soap and apply on the upper-side of the palm and evaluate the foam, the moisturizing effect, and smoothness, and the soothing effect