Properties of pectin powder and pectin films from pomelo, orange and dragon fruit peels

HO CHI MINH CITY – AUGUST 2022 PROPERTIES OF PECTIN POWDER AND PECTIN FILMS FROM POMELO, ORANGE AND DRAGON FRUIT PEELS... HO CHI MINH UNIVERSITY OF TECHNOLOGY AND EDUCATION FACULTY FOR

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

HO CHI MINH UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING FOOD TECHNOLOGY

DEPARTMENT OF FOOD TECHNOLOGY

GRADUATION THESIS Thesis ID: 2022-18116017

Major: FOOD TECHNOLOGY

Supervisor

HO CHI MINH CITY – AUGUST 2022

PROPERTIES OF PECTIN POWDER AND PECTIN FILMS FROM POMELO, ORANGE AND DRAGON

FRUIT PEELS

HO CHI MINH UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING FOOD TECHNOLOGY

DEPARTMENT OF FOOD TECHNOLOGY

GRADUATION THESIS Thesis ID: 2022-18116017

PROPERTIES OF PECTIN POWDER AND PECTIN FILMS FROM POMELO, ORANGE AND DRAGON

FRUIT PEELS

Major: FOOD TECHNOLOGY

HO CHI MINH CITY – AUGUST 2022

Supervisor

ACKNOWLEDGEMENT

First and foremost, we would like to thank all of the teachers in the Food Technology Department of the University of Technology and Education of Ho Chi Minh City for teaching and imparting so much knowledge during the study at school, creating all facilities and equipment to assist us in completing the thesis in the best possible way Furthermore, in order to complete and achieve the results we have today, we had to confront and overcome all of the difficulties and challenges encountered during and throughout the project In addition, our beloved classmates and families make significant contributions, motivation, and support to us

We would especially like to thank PhD Nguyen Vinh Tien, the teacher who guided this graduation project Throughout the project, he enthusiastically guided and imparted to us the necessary knowledge and skills to guide how to use tools and operate machines in the laboratory, timely comment At the same time, whenever we face difficulties in the research process, the teacher always create a welcoming and encouraging environment

Sincerely, we would like to express our gratitude to Ms Ho Thi Thu Trang of the Department of Food Technology for facilitating and assisting us in using the measuring tools and equipment available at the Faculty of Chemical and Food Technology's laboratory

We tried to learn and research as much as we could to complete the graduation thesis, but we are still limited in knowledge and experience, so there will be flaws We are looking forward to receiving feedbacks from teachers and friends in order to improve the thesis

We sincerely thank

TABLE OF CONTENTS

TABLE OF CONTENTS iii

LIST OF FIGURES vi

LIST OF TABLES viii

LIST OF ABBREVIATIONS ix

ABSTRACT 1

CHAPTER 1: INTRODUCTION 2

CHAPTER 2: LITERATURE REVIEW 4

CHAPTER 3: OVERVIEW 5

3.1 Introduction about pectin 5

3.1.1 Structure and chemical compositions of pectin 5

3.1.2 Classification of pectin 7

3.1.3 Properties of pectin 8

3.1.4 Pectin extraction technique 9

3.1.5 Applications of pectin 10

3.2 Overview about pomelo 10

3.2.1 Introduction about pomelo 10

3.2.2 Nam Roi Pomelo 11

3.3 Overview about white dragon fruit 12

3.4 Overview about green orange 12

CHAPTER 4: MATERIALS AND METHODS 14

4.1 Materials 14

4.1.1 Green orange peel powder 14

4.1.2 Nam Roi pomelo peel powder 14

4.1.3 White dragon fruit peel powder 14

4.2 Equipment for study 14

4.3 Research process diagram 15

4.4 Methods for the analysis of pectin 17

4.4.1 Investigate raw materials 17

4.4.2 Investigate factors affecting pectin extraction process 19

4.4.3 Pectin analysis 20

4.4.4 Determine the ash content of pectin 21

4.4.5 Fourier Transform Infrared (FT-IR) spectrum 21

4.4.6 Determine Equivalent Weight 22

4.4.7 Determine Methoxyl Content 22

4.4.8 Determine Total Anhydrouronic Acid Content 22

4.4.9 Degree of esterification 22

4.5 Methods for the analysis of pectin film 23

4.5.1 Investigate the effect of glycerol on pectin film 23

4.5.2 Investigate the effect of Ca 2+ on pectin film 23

4.5.3 Pectin films analysis 24

CHAPTER 5: RESULTS AND DISCUSSIONS 26

5.1 Determination of some basic chemical components in grapefruit, orange and white dragon fruit peels 26

5.2 Results of factors affecting pectin extraction process 26

5.2.1 Investigating the effect of extraction time on pectin extraction efficiency 26

5.2.2 The result of extraction temperature affects the extraction efficiency of pectin 28

5.2.3 The result of citric acid concentration affects the extraction efficiency of pectin 30 5.3 The results of moisture and ash content of pectin 32

5.4 Results of the properties of pectin 33

5.4.1 Equivalent Weight 33

5.4.2 Methoxyl content 34

5.4.3 Total Anhydrouronic Acid Content 34

5.4.4 Degree of Esterification 35

5.4.5 Result of FT-IR spectrum of pectin 35

5.5 Result of the properties of pectin-based films 40

5.5.1 Result of the tensile strength and the elongation at break of pectin films 40

5.5.2 Result of the thickness of the pectin film 43

5.5.3 Result of the moisture content of the pectin film 45

5.5.4 Result of the solubility and the swelling ability of the pectin film 47

5.5.5 Result of the water vapor permeability of the pectin film 51

5.5.6 Result of the FT-IR spectrum of pectin film 53

5.5.7 Result of transparency of pectin film 55

CHAPTER 6: CONCLUSION 58

REFERENCES 66 APPENDIX 72

LIST OF FIGURES

Figure 3.1: Nam Roi Pomelo 11

Figure 3.2: White dragon fruit 12

Figure 3.3: Vietnamese Green orange 13

Figure 4.1: Flowchart to study the influence of factors on the pectin extraction process and investigate the properties of pectin powder and pectin film 15

Figure 4.2: Flowchart of extracting pectin from peel powder 16

Figure 4.3: Flowchart of creating pectin film 17

Figure 5.1: Pomelo, orange, white dragon fruit peel powder (from left to right) 26

Figure 5.2: Effect of extraction time on pectin extraction efficiency 27

Figure 5.3: Effect of temperature on pectin extraction efficiency 29

Figure 5.4: Effect of citric acid concentration on pectin extraction efficiency 30

Figure 5.5: Pectin extract after precipitating with alcohol 32

Figure 5.6: Wet pectin extracted from pomelo, green orange and white dragon fruit peel powder (from left to right) 32

Figure 5.7: Pectin powder extracted from pomelo, green orange and white dragon fruit peel powder (from left to right) 33

Figure 5.8: Comparing FT-IR spectrum of pectin commercial, pomelo, orange and dragon fruit36 Figure 5.9: FT-IR spectrum of pectin (A) commercial, (B) pomelo, (C) orange and (D) dragon fruit 38

Figure 5.10: Tensile strength of glycerol-pectin films and calcium-pectin films with respectively different concentration of (A) glycerol at 0%, 10%, 30%, 50%, 70% and (B) calcium at 1%, 2%, 3% with constant glycerol 30% in the pectin solution 41

Figure 5.11: Elongation at break of glycerol-pectin films and calcium-pectin films with respectively different concentration of (A) glycerol at 0%, 10%, 30%, 50%, 70% and (B) calcium at 1%, 2%, 3% with constant glycerol 30% in the pectin solution 42

Figure 5.12: Thickness of glycerol-pectin films and calcium-pectin films with respectively different concentration of (A) glycerol at 0%, 10%, 30%, 50%, 70% and (B) calcium at 1%, 2%, 3% with constant glycerol 30% in the pectin solution 44

Figure 5.13:Moisture content of glycerol-pectin films and calcium-pectin films with respectively different concentration of (A) glycerol at 0%, 10%, 30%, 50%, 70% and (B) calcium at 1%, 2%, 3% with constant glycerol 30% in the pectin solution 46

Figure 5.14: Solubility of glycerol-pectin films and calcium-pectin films with respectively different concentration of (A) glycerol at 0%, 10%, 30%, 50%, 70% and (B) calcium at 1%, 2%, 3% with constant glycerol 30% in the pectin solution 49

Figure 5.15: Swelling ability of glycerol-pectin films and calcium-pectin films with respectively different concentration of (A) glycerol at 0%, 10%, 30%, 50%, 70% and (B) calcium at 1%, 2%, 3% with constant glycerol 30% in the pectin solution 50

Figure 5.16: Water vapor permeability of glycerol-pectin films and calcium-pectin films with respectively different concentration of (A) glycerol at 0%, 10%, 30%, 50%, 70% and (B) calcium at 1%, 2%, 3% with constant glycerol 30% in the pectin solution 52

Figure 5.17: FT-IR spectrum of glycerol-pectin films at concentration 0%, 10%, 30%, 50%, 70% respectively of (A) pomelo, (B) orange, and (C) dragon fruit 54 Figure 5.18: FT-IR spectrum of calcium-pectin films at concentration 1%, 2%, 3%, respectively

of (A) pomelo, (B) orange, and (C) dragon fruit 54

LIST OF TABLES

Table 5.1: Moisture and ash content in pomelo, orange and white dragon fruit peel powder 26 Table 5.2: Investigating the effect of extraction time on pectin extraction efficiency 27 Table 5.3: Survey results on the effect of temperature on pectin extraction efficiency 28 Table 5.4: Survey results on the effect of citric acid concentration on pectin extraction efficiency 30 Table 5.5: Result of the moisture and ash content of extracted pectin samples 32 Table 5.6: Results of properties of pectin extracted from pomelo, green orange and dragon fruit peel powder 33 Table 5.7: Result of the tensile strength and elongation at break of pectin-based films 40 Table 5.8: Result of the thickness of pectin-based films 43 Table 5.9: Result of the moisture content of pectin-based films 45 Table 5.10: Result of the solubility and the swelling ability of pectin-based films 47 Table 5.11: Light transmittance of Gly-pectin films at three ranges 56 Table 5.12: Light transmittance of Ca-pectin films at three ranges 57

LIST OF ABBREVIATIONS

%T Transmittance

C Degree Celsius

AC Ash content

ATR Attenuated total reflection

AUA Total anhydrouronic acid content

FT-IR Fourier Transform Infrared Spectroscopy

GalA Galacturonic acid

MeO Methoxyl content

NaCas Sodium caseinate

NaOH Sodium hydroxide

pH Potential of hydrogen

PT/CHT Pectin/Chitosan

RG-I Rhamnogalacturonan-I

RG-II Rhamnogalacturonan-II

WPI- Whey protein isolate-

WVP Water vapor permeability WVTR Water vapor transmission rate XGA Xylogalacturonans

ZnO/Zn-NPs Zinc oxide/zinc nanoparticles

of tension strength for films created from low pectin Dragon fruit films exhibited a gradual decrease in solubility with increasing calcium concentration The report also

elongation, tension strength and low solubility for pectin films The pectin films were characterized by FT-IR, UV-VIS, and water vapor permeability analysis The overall findings of the study illustrated that the pectin films have the potential to be used as a promising food coating material in the future

Key words: pectin, Vietnammese pomelo, green orange, white dragon fruit, pectin films

CHAPTER 1: INTRODUCTION

At present, the increasing demand for plastic materials has had a significant impact on both human health and the living environment Therefore, it is of utmost importance to create edible biofilms that are resistant to microbes and meet food preservation requirements in order to ensure customer safety Edible films are usually produced mainly from non-toxic polysaccharide sources, including pectin Pectin has the ability to form films The benefit of pectin film is that it has very good oxygen barrier ability but has high water solubility Pectin is a gel-forming substance obtained from plants that is extensively employed in the production of food Pectin is fundamentally a heterogeneous linear polysaccharide, and depending on the source and extraction technique, it might have different properties Apple pulp and citrus peel, which serve

as the primary sources of raw materials for the manufacturing of commercial pectin, are plentiful natural sources of pectin Pectin is an excellent thickener, emulsifier, and stabilizer in addition to its excellent gelling abilities As a result, research, production, and application are of interest to many nations worldwide

One of the most significant sources of food waste is the fruit processing business There are approximately 50 - 70% of the fruit weight can be employed in the manufacturing process, with the remainder considered a by-product, comprising the peel, core, and seeds A huge number of some fruits can be squandered (mango 30 - 50%, banana 21%, pineapple 40-50% and orange (30

- 50%) These wastes may include considerable amounts of beneficial substances For instance, there are sugars, organic acids, essential oils, antioxidants, dietary fiber and antimicrobials, which can be converted into goods Commercialization can provide value while lowering trash disposal and environmental protection costs Pectin is one of the most essential compounds in fruit peel waste In 2020, the global demand for pectin is expected to reach 81.479 tons and tends

to increase by about 5% per year Correspondingly, the recovery of pectin from rind waste offers numerous commercial advantages

Nam Roi Pomelo (Citrus grandis Cv.), Green Orange (King Orange), and White Dragon fruit (Hylocereus undatus) are all varieties of citrus These three species of fruit are extremely popular

in Vietnam, with the fruit flesh being the most commonly used part The peeled portion of the fruit contains a momentous amount of pectin (10 - 22%) This is a great supply of raw materials for testing pectin manufacture As a result, we decided to conduct study on the topic: ―Properties

of pectin powder and pectin films from pomelo, orange and dragon fruit peels‖

- The factors affecting the extraction of pectin from pomelo, orange and white dragon fruit peels

- The process of extracting pectin from pomelo, orange and white dragon fruit peels

- The properties of pectin

- Application of pectin to form films and determine the properties of films

1.3 Object and scope of the research

- Research object: Pectin extracted from pomelo, orange and white dragon fruit peels

- Scope of the study: this study was carried out on a laboratory scale

- Provide complete pectin extraction process This serves as a premise for further studies

- Research the factors affecting the extraction process in order to improve the efficiency and quality

- Enhance the value and widen the range of applications of pomelo, orange and white

dragon fruit rind

CHAPTER 2: LITERATURE REVIEW

Mellinas et al [1] created pectin-based active films with a cocoa bean shell and zinc oxide/zinc nanoparticles (ZnO/Zn-NPs) at varied concentrations Finally, the photocatalytic activity of the nanoparticle-containing films was demonstrated, with photodegradation efficiency values approaching 90% after 60 minutes at 3 wt% ZnO/Zn-NPs loading Finally, the pectin-based bionanocomposites generated with cocoa bean shell waste extract and zinc oxide/zinc nanoparticles demonstrated tremendous potential for use as active packaging for food preservation

Mada T et al [2] used microwave aided extraction to obtain pectin from banana-papaya peel The optimal temperature, duration, and pH to achieve maximal yield (23.74%) and anhydrouronic acid (69.97%) were determined to be 73°C, pH 2, and 35 minutes, respectively Duan X et al [3] investigated the extraction of pectin from satsuma mandarin peel using high hydrostatic pressure-assisted citric acid or hydrochloric acid, and the physiochemical, structural, rheological, and emulsifying properties were compared to those of conventional citric acid and hydrochloric acid Citric acid was found to both improve pectin yield and have the highest yield (18.99 percent)

In Viet Nam, Thang et al [4] studied and developed a formula to make a complex alginate film, with the primary ingredient being pectin derived from passion fruit peel coupled with alginate, glycerol, and Ca2+ As a result, a formula for producing a complicated pectin-alginate film with the following composition was developed: The ratio of pectin:water 2.5 percent (w/v), pectin:alginate 65:35 (v/v), glycerol 20% (w/w), and Ca2+ 5% (w/w) is the most effective for the preservation of fresh passion fruit Simultaneously, the pectin-alginate film specifications were determined: thickness 0.139 ± 0.007 (mm), tensile strength 30.84 ± 1.87 (MPa), breaking elongation 28.23 ± 0.82%, moisture absorption 10.03 ± 0.48% Actual results show that pectin-alginate film has the effect of maintaining quality and extending the shelf life of fresh passion fruit up to 12 days

pectin-Phuong and Xo extracted pectin from Tiliacora triandra and had a DE = 48.36% They determined the functional properties of food packaging made from pectin extracted from Tiliacora triandra combined with chitosan with mixing ratios of 100:0; 75:25; 50:50; 25:75 and 0:100 The mixing ratio between pectin and chitosan affects the properties of the formed film such as thickness, tensile strength, elongation, elasticity, water vapor permeability, solubility, oxygen transmission The research results show that the film formed with the ratio of 50:50 is the best because it has low solubility of 9.09%, high breaking strength of 19.7 MPa, low water vapor permeability of 0.93 g.mm/m2.day.kPa, low water vapor transmittance 21.34 g/m2/day, low oxygen transmittance 51.49 cc/m2 And especially, films with the participation of chitosan are resistant to spoilage microorganisms in food preservation technology in general such as Saccharomyces cerevisiae, Aspergillus niger and E coli With these properties, the pectin-chitosan film with a ratio of 50:50 can be used as an active coating for food preservation [5]

CHAPTER 3: OVERVIEW

3.1 Introduction about pectin

The word "pectin" comes from the Ancient Greek word "pktikós," which meaning "curdled, coagulated" It is a structurally acidic heteropolysaccharide found in terrestrial plants leaf blades and primary and middle cell walls Galacturonic acid, which is a sugar acid generated from the sugar galactose, is the primary component of pectin Henry Braconnot was the first person who isolating and describing it in 1825 [6]

Pectin usually has a form in white to light brown powder which is manufactured mostly from citrus fruits and used as a gelling subtance in cuisine, most notably jams and jellies It is also used in dessert fillings, pharmaceuticals, desserts or play a role as a stabilizer for fruit juice and milk drinks, and as a source of dietary fiber

Fruit preservers maker collected dried apple pomace from apple juice producers and cooked them to extract pectin during the Industrial Revolution Following that, factories were developed

in apple manufacturing regions of the United States and Europe in the 1920s and 1930s to extract pectin from apple pomace and subsequently citrus peel [7]

In the past, pectin was once supplied as a liquid extract, but it is now more generally used as a dried powder, which is easier to reserve, handle and transport than a liquid pectin

Pectins are complex set of polysaccharides which found in most primary cell walls, according to plant biology Exocytosis transports pectin to the cell wall via golgi-produced vesicles [8] Pectin

is a crucial food element that serves as a gelling and stabilizing agent It is frequently deprived

by using chemicals or enzymes from fruits, particularly citrus fruits Pectin is considered as the most complicated macromolecule in nature since it can be composed of up to 17 distinct monosaccharides linked by over 20 different connections [9]

3.1.1 Structure and chemical compositions of pectin

One of the most abundant macromolecules is pectin which found in the fundamental cell wall of plants, and it can be found in both the matrix and the middle lamellae Pectin amounts, structure, and chemical composition vary between plants, over time within a plant, and in different parts of

a plant Pectin is a polysaccharide found in plant cell walls that enables for the elongation and growth of the main cell wall [10] Pectin is broken down by the enzymes pectinase and pectinesterase during fruit ripening, causing the fruit to soften when the middle lamellae break down and cells separate from one another

Galacturonic acid (GalA) is abundant in pectin, and it serves as the backbone for three additional domains: homogalacturonan (HGA), rhamnogalacturonan-I (RG-I), and rhamnogalacturonan-II (RG-II) [11] Galacturonic acid accounts for approximately 70% of pectin [12] Pectin is made

up of three covalently linked polysaccharides that form pectin networks in the cell wall matrix and middle lamellae

Figure 2.1 Pectin chemical structure

3.1.1.1 Homogalacturonan

Homogalacturonan is made up of linear polymers that are mostly made up of d-galacturonic acid units (not less than 65%) linked together by α-(1-4)-glycosidic linkages At C-6, the carboxyl groups in galacturonic acid units can be partially methyl esterified, and the free acid groups can

be partially or completely neutralized with potassium sodium or ammonium ions Depending on the source, pectins can potentially be acetylated on the O-2 or O-3 locations [13]

The quantity of carboxyl groups that can be esterified with methyl groups determines the degree

of esterification, also known as the degree of methoxylation Pectins are classified according to their degree of esterification of Pectin with lower than 50% of their carboxyl groups esterified are referred as low methoxyl (LM), whereas those with higher than 50% of their carboxyl groups esterified are known as high methoxyl (HM) [14] This property is related to therapeutic properties and gelling mechanisms

Xylogalacturonans (XGA) are homolagacturonans that have been substituted at O3 with a linked d-xylose-(1-3), which is then occasionally replaced at O-4 with another -linked d-xylose Xylogalacturonans have been found primarily in generative tissues like fruit and seeds, and they have been linked to archiving and reproduction fuctions in plant organs [15]

-3.1.1.2 Rhamnogalacturonan-I

RG-I features an alternating -l-Rhap backbone that connects to the 4-position of —d-GalpA, which connects to the Rhap's 2-position The neutral sugars arabinose and galactose extensively substitute RG-I, resulting in arabinan, galactan, and arabinogalactans in the side chains, which are mainly connected to the O-4 position of rhamnose [16] However, their relative proportions and chain lengths differ depending on the plant source [17] The RG-I backbone can contains up

to 300 rhamnosyl and 300 galactosyluronic acid residues

3.1.1.3 Rhamnogalacturonan-II

Rhamnogalacturonan-II has a greatly conserved structure and is composed of a linear backbone chain of galacturonic acid units replaced with l-rhamnose, d-galactose, and numerous uncommon

sugars like, aceric acid, apiose, 3-O-methyl-l-fucose, 2-O-methyl-d-xylose, deoxy-l-xylose, 3-deoxy-d-manno-octulosonic acid and 3-deoxy-d-lyxo-heptulosaric acid.Rhamnogalacturonan-II side chains are made up of 12 different types of sugars connected by more than 20 dissimilar linkages RG-II, the most structurally complicated pectin domain, has a high degree of conservation across numerous plant kind The cross-linking between the RG-II chains of two neighboring pectin molecules strengthens the pectin network Due to its structure, rhamnogalacturonan-II can create borate esters dimers [18]

3-C-carboxy-5-3.1.2 Classification of pectin

Pectin products on the market are diverse However, pectin can be classified as follows:

Classification based on the degree of methylation, pectin is divided into two types:

 High Methoxyl Pectin (HMP): DE > 50% or MeO > 7% This type of pectin may

increase the viscosity of the product To form coagulation, it is necessary to have pH from 3,1 to 3,4 and sugar concentration above 60%

 Low Methoxyl Pectin (LMP): DE < 50% or MeO < 7% is produced by reducing the methoxyl group in the pectin molecule Low methoxyl pectin can coagulate in a sugar-free medium They are often used as a film to wrap and preserve products

Classification based on the state, pectin is divided into:

 Concentrated liquid Pectin

 Dried pectin extract

 Pectin powder

Classification based on the speed of gel formation, pectin is divided into:

 Pectin with very fast gelling speed (Ultra Rapid Set)

 Pectin with fast gelation speed (Rapid Set)

 Pectin with medium gelation speed (Medium Set)

 Pectin with a slow gelation speed (Slow Set)

 Pectin with an extremely slow gelation speed (Ultra Slow Set)

Classification based on the application field, pectin is divided into:

 Food Pectin

 Pharmaceutical pectin: apple pectin, modified citrus pectin

Classification based on the source material, pectin is divided into:

 Pectin from apple pulp

 Pectin of citrus fruit

 Grape pectin

 Beetroot Pectin

 Sunflower Pectin

3.1.3 Properties of pectin

Clean water is used to dissolve pectin Pectinic and pectic acid monovalent cation salts are normally soluble in water, whereas divalent and trivalent cation salts are either weakly or insoluble When dry powdered pectin is combined with water, it immediately hydrates and clumps These clumps are made up of semidry pectin packets encased in a highly moist outer coating envelope To avoid clump formation, dry mix pectin powder with a water-soluble carrier substance or manipulate pectin with upgrade dispersibility due to distinctive manufacturing method [19]

At room temperature, HM-pectin is only stable in the pH range of 5 to 6, which is close to neutral Elimination, which causes chain cleavage and a quick loss of viscosity and gelling properties, starts when the temperature (or pH) rises The LM-pectin is a little bit more stable at these temperatures Even at ambient temperature, pectin is quickly de-esterified and degraded by alkaline pH levels While low molecule pectin are more robust and should lose little after one year of room temperature storage, powdered high molecule pectin lose their capacity to form gels when stored in damp or warm settings [19]

The capacity to create gels of pectin is the basis for its most significant application HM-pectin gels with acid and sugar In contrast to LM-pectin, HM-pectin does not have enough acid groups

to gel or precipitate with calcium ions It has been proposed that hydrophobic interactions and hydrogen bonds play crucial roles in the aggregation of pectin molecules The free carboxyl groups on pectin molecules and the hydroxyl groups of nearby molecules produce hydrogen bonds, which are what causes gel to develop The majority of the unesterified carboxyl groups are present as partially ionized salts in a neutral or very slightly acidic dispersion of pectin molecules

The carboxyl ions are transformed into unionized carboxylic acid groups when acid is introduced This decrease in negative charges lessens the forces that pull pectin molecules apart

as well as the forces that attract pectin to water molecules Sugar competes with water, causing the pectin to become even less hydrated These circumstances make it harder for pectin to remain

in dispersed condition

The degree of esterification also has an impact on how quickly gels are formed A higher DE results in a quicker setting Pectin has a DE of more than 72%, or rapid-set pectin, also gel at higher levels and lower soluble solids than slow-set pectin (DE of pectin from 58% to 65%) Divalent cations are necessary for the correct gel formation of LM-pectin The well-known "egg

- box" model is mostly used to explain the mechanism of LM-pectin gelation [20] Specific sequences of GalA monomer in parallel or adjacent chains are coupled intermolecularly through electrostatic and ionic bonding of carboxyl groups in junction zones generated by the side-by-side, ordered interactions of galacturonans

When pectin is exposed to a dehydrating substance like alcohol, it precipitates as a solid gel They are known to be insoluble in the majority of bio-colloids since they are particularly

responsive to dehydration and are affected by any other hydrophilic colloids as well The amount

of free carboxyl groups in pectin determines its negative charge, which is mostly what causes it

to precipitate [21]

3.1.3.1 Solubility

There are two forms of pectin, pectin soluble in water and pectin water insoluble Based on solubility, pH, temperature, the kind of solute, and the concentration of the solute are all variables that affect the solubility of pectin [22] [11] At pH 4, pectin becomes stable [23] Pectin's solubility is also influenced by its chemical makeup For example, monovalent cations of pectin are water soluble, whereas divalent or trivalent cations are not

3.1.3.2 Gelation of pectin

The capacity to form gel of pectin in the existence of acid, calcium, or sugar is one of its most intriguing features, and this makes it useful in many food-related sectors [24] Hydrogen bonding and hydrophobic interactions between polymer chains stabilize the pectin polymer [25]

3.1.4 Pectin extraction technique

3.1.4.1 Extract by water

There are number of free pectin in the plant cell wall, it can be easily extracted with water When combining pectin extraction in hot water for an extended period of time, the process efficiency increases However, if pectin extraction at high temperatures for a long period of time, the problem must consider is the pectin degradation as well as the energy factor

3.1.4.2 Extract by acid

Using acidified water and heat is the most common method for extracting pectin from plant tissue A long period of direct heating should be avoided because it may cause thermal degradation of the polymer Extraction conditions such as time, temperature and solvent ratio in different studies depend on the desired ratio of pectin and pectin to be obtained However, normally the temperature fluctuates from 50 to 100C during 0.5 to 5 hours To remove the pulp, the hot acid extract was filtered through a cheese cloth or using centrifugation The filtrate was then cooled to 4°C and precipitated with twice as much ethanol After mixing the solvent precipitate combination until the pectin floats, it is eliminated with cloth and dried [26]

3.1.4.3 Extract by enzyme

Enzymatic pectin extraction is both safer for the environment and more successful for pectin output Enzymes such as, hemicellulose, protease, polygalacturonase, cellulose, celluclast, alcalase and α-amylase and neutrase, xylase, cellulose, β-glucosidase, endopolygalacturonase, and pectinesterase are used in pectin extraction because enzymes have the ability to degrade pectin and change its physicochemical features

3.1.4.4 Extract by using microwave

Extraction with the aided of microwave relates to dielectric heating of plant compounds via microwave irradiation Dipolar rotation of water occurs as a result of microwave energy

absorption, resulting in heat creation within plant tissues Many researchers have lately examined microwave-assisted extraction and discovered that it can significantly boost the quality and yield

of pectin [27]

When the microwave power is increased due to an increase in microwave irradiation energy, the penetration of solvent into the plant matrix may be improved and solvent can be efficiently delivered to plant cells for pectin extraction The interaction of molecules with the electromagnetic field allows for a quick transfer of energy to the solvent and matrix, allowing for the dissolution of extractable components Water, as a polar solvent, can readily absorb microwave radiation, resulting in efficient heating Furthermore, microwave irradiation accelerates cell rupture by causing a sudden temperature increase and a surge in internal pressure within the cells of a plant sample, which promotes the destruction of the sample surface and, as a result, the exudation of pectin within the plant cells into the surrounding solvents, as well as the growth [28]

The increasing energy of microwave irradiation can enhance solvent penetration into the plant matrix and efficiently deliver to materials through molecular interaction with the electromagnetic field and offer a rapid transfer of energy to the solvent and matrix, allowing the extraction of components to dissolve When compared to conventional heating, the use of microwave assisted extraction to optimize the extraction process of pectin from apple pomace resulted in the highest yield from apple pomace as well as a shorter extraction time

3.1.5 Applications of pectin

In addition to gelling applications in foods, pectin is also used in the pharmaceutical sector Pectin has a major impact on blood cholesterol levels It has been reported to help lower blood cholesterol in a variety of persons and experimental scenarios after being thoroughly evaluated Consuming at least 6 grams of pectin per day is required to have a momentous cholesterol-lowering effect Pectin intake less than 6 grams each day are not effective [29]

Pectin is an intriguing potential for usage of pharmaceuticals, such as a medicine carrier in controlled release applications Many approaches, particularly ionotropic gelation and gel coating, have been employed to create pectin-based transportation systems These straightforward approaches, along with the low virulence property, make pectin an intriguing and prospective excipient for the pharmaceutical sector, both now and in the hereafter [30]

3.2 Overview about pomelo

3.2.1 Introduction about pomelo

The pomelo is the greatest citrus fruit in the Rutaceae family and the primary ancestor of the grapefruit It is a non-hybrid citrus fruit that is native to Southeast Asia Pomelo, which tastes like a sweet grapefruit, is widely consumed and utilized for celebratory occasions throughout Southeast Asia Unlike grapefruit, phytochemicals in pomelo have the potential to cause medication interactions Fresh pomelo peel contains about 0.15% essential oil, pectin (about 30%) and flavonoid compounds, limonene 41.45 - 84.62%, myrcene 8.28 - 50.66% [31]

Pomelo is a large tree, averaging about 3 to 4 m tall at maturity, the bark is pale yellow, and sometimes there is sap in the crevices of the stem The branches have long, pointed spines Leaves have gill-shaped liver, ovate leaves, 11 to 12 cm long, 5 to 6 cm in wide, both ends obtuse, whole, tough, petioles with large wing tips The flowers are double, single, clustered with 6-10 flowers and have a very pleasant scent Pomelo has globose, thick shell and color depending on variety Pomelo flowers are small white

3.2.2 Nam Roi Pomelo

Nam Roi pomelo is a famous pomelo variety in Vietnam, grown a lot in some provinces in the Southwest region (especially Vinh Long) Each year, this pomelo variety is harvested twice in August and December of the lunar calendar Today, Nam Roi pomelo is grown the most in Phu Huu, Chau Thanh, Hau Giang and Binh Minh, Vinh Long

Nam Roi pomelo (Citrus grandis Cv.) has few seeds or no seeds, the grapefruit segment is even, easy to separate, light yellow in color, succulent but drained, has a rich aroma, and carries many essential nutrients for the human body Nam Roi pomelo is a perennial plant with a wide canopy and an average height of 3 - 4m Flowers often grow in clusters in the leaf axils, each bunch has from 6 - 7 flowers, pomelo flowers are milky white Five pomelos are pear-shaped, wide-bottomed, often growing in a cluster of three, each with an average weight of 1.5 to 3 kg The thin grapefruit peel is easy to peel, turns yellow when ripe, and has a white flesh inside

In terms of growth, this plant has the ability to grow and develop quite well, can adapt to many different climatic conditions After 2.5 to 3 years, the tree can be harvested, the tree life is quite durable, can be harvested for up to 20 years, but the fruit quality is still very high [32]

Figure 3.1: Nam Roi Pomelo

3.3 Overview about white dragon fruit

Pitaya is commonly associated with the fruit of the genus Stenocereus, whereas pitahaya or dragon fruit is associated with the fruit of the genus Selenicereus (formerly Hylocereus), both of them are members of the Cactaceae family Dragon fruit is grown throughout the world in, Mexico, Peru, Southeast Asia, South Asia, East Asia, the United States, the Caribbean, Australia, Mesoamerica, and other subtropical and tropical locations Dragon fruit peel has a pectin content

of about 12.5% to 15% depending on the ripeness as well as the type of fruit [33]

Sweet pitayas are available in three varieties, each having leathery, leafy skin:

Selenicereus undatus (Pitaya blanca or pitaya with white flesh, also known as Hylocereus undatus) has the pink skinned fruit with white flesh This is the most common type of dragon fruit

Selenicereus costaricensis has red-skinned fruit with crimson flesh inside (also known as Hylocereus costaricensis and maybe as Hylocereus polyrhizus)

The fruit of Selenicereus megalanthus is yellow with white flesh (Pitaya amarilla or yellow pitaya, also known as Hylocereus megalanthus)

Figure 3.2: White dragon fruit 3.4 Overview about green orange

Cam Sanh (Vietnamese green orange) is a citrus hybrid produced in Vietnam Despite its resemblance to mandarin or tangerine, Vietnammese green orange is Vietnamese meaning

"terracotta orange." The thick skin of the fruit, which is generally brilliant green, can also be half green and partially orange, or entirely orange Its flesh is orange, dark, and sweet This is the

most popular orange cultivar in Vietnam Orange peel is a rich source of pectin extraction, accounting approximately 40-45% of the total weight of processed citrus fruit It contains approximately 25-30% pectin

It is one of the many citrus fruits growing in the area Orange-colored chun or sen, yellow bak son, and pink hong orange-mandarin hybrids or "king mandarins" (C reticulata C sinensis); and

at least three non-hybridized mandarin (C reticulata) varietals The Cam Sanh is also known as

"king mandarin." One notable difference is that when the fruits develop in temperate climates, they turn a vibrant orange in response to colder temperatures

The green orange was imported to the United States in 1880 Vietnam's Mo Cay District, Ben Tre Province, and the northern hilly areas are where the tree is grown It was also grown in the Yen The region of Bac Giang Province's Bo Ha region, but it was destroyed owing to citrus greening disease Vietnammese green orange is now widely grown in northeastern Vietnam (particularly in Ha Giang, Tuyen Quang), as well as in several Mekong Delta districts in the south, including Tien Giang, Can Tho and Vinh Long [34]

Figure 3.3: Vietnamese Green orange

CHAPTER 4: MATERIALS AND METHODS

4.1 Materials

4.1.1 Green orange peel powder

Green orange peels were gathered from juice production plants in Thu Duc District, Ho Chi Minh City and transported to the laboratory for testing After eliminating the orange peel, it is washed, cut into small pieces and dried at 60oC until the moisture level is less than 10% The dried peels are then crushed by grinder and sieved using a 0.6 - 1.5 mm mesh sieve Orange peel powder was stored at room temperature in zip bags for further investigation

4.1.2 Nam Roi pomelo peel powder

Nam Roi pomelo peels were gathered from markets in Thu Duc District, Ho Chi Minh City and transported to the laboratory for testing After eliminating the outer skin of Nam Roi pomelo peel, it is washed, cut into small pieces and dried at 60oC until the moisture level is less than 10% The dried peels are then crushed by grinder and sieved using a 0.6 - 1.5 mm mesh sieve

Pomelo peel powder was was stored at room temperature in zip bags for further investigation

4.1.3 White dragon fruit peel powder

White dragon fruit peels were bought from markets in Thu Duc District, Ho Chi Minh City and transported to the laboratory for testing After eliminating the outer skin of white dragon fruit peel, it is washed, cut into small pieces with size of 3x3cm and dried at 60oC until the moisture level is less than 10% The dried peels are then crushed by grinder and sieved using a 0.6 - 1.5

mm mesh sieve Dragon fruit peel powder was reserve at room temperature in zip bags until further investigation

4.2 Equipment for study

- UV-Vis Halo Vis 20 Spectrophotometer (Dynamica, Switzerland)

- 2- and 4-digit analytical balance (Sartorius, Germany)

- Centrifuge Hettich (Germany)

- Heated shaker (Korea)

- Thermostat tank (Menmert, Germany)

- Convection oven (Japan)

- Electronic caliper (Germany)

- FT-IR - 4700 meter (Germany)

- Necessary tools such as beaker, pipette, micropipette, volumetric flask, petri disk,

4.3 Research process diagram

Figure 4.1: Flowchart to study the influence of factors on the pectin extraction process and

investigate the properties of pectin powder and pectin film