HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION FACULTY FOR HIGH QUALITY TRAINING GRADUATION PROJECT Thesis code: 2022-18116018 PROPERTIES OF POWDERS AND FILMS FROM KARAYA GUM
INTRODUCTION
Introduction
As industrialization and modernization progress, the demand for higher quality food, consumption, and living conditions continues to rise, enhancing the overall quality of life Consequently, the food technology industry is rapidly evolving, aiming to improve health outcomes for the population, particularly in Vietnam In response to these demands, food factories are innovating by producing fast foods, canned goods, and ready-made products that prioritize convenience, long shelf life, and food safety This advancement heavily relies on the use of diverse food additives, especially those derived from natural sources, which are continuously researched and developed for application in the food sector.
Karaya gum (KG) is a widely utilized food additive known for its low cost, abundant availability, and excellent gel-forming and water-absorbing properties, making it an effective structural stabilizer in food products To explore the structure, characteristics, and applications of KG in the additive industry, we conducted a study titled "Properties of powders and films from karaya gum modified by bicarbonate hydrolysis and esterification."
Objectives of the study
To investigate the effects of modified KG and its similarities or differences from the original KG, we conducted modifications through hydrolysis and esterification Subsequently, comparative studies were performed to analyze the characteristics of KG before and after these modifications.
Object and scope of the study
- Scope of the study: this study was carried out on a laboratory scale.
Research content
Research on modification of KG by hydrolysis and esterification, investigation of solubility, viscosity, moisture uptake, infrared spectrum, and emulsification ability of KG before and after modification.
Scientific and practical significance
- Research the properties of KG before and after modification
- Enhancing the value and application of KG more widely in the food additive industry and other fields
- Apply the ability to create films to make active films to replace plastic films, help protect the environment, limit mold
OVERVIEW
Karaya gum
Karaya Gum, derived from the dried exudates of the Sterculia tree (family Sterculiaceae), is collected after the tree is tapped or as natural exudates Among the various species, Sterculia setigera is recognized as a significant source of commercial Karaya Gum globally, particularly found in the Sudanese savanna forests.
Sterculia setigera, a deciduous tree The southern portion of the Blue Nile, southern Kordofan, the
The Nuba Mountains, Bahr el Ghazal area, and Red Sea Hills are prime locations for sourcing trees used in various industries (D Le Cerf, 1990) KG is an economical and widely accessible raw material, commonly found in pharmaceutical and dental adhesive formulations Additionally, it serves important roles in the food industry as a thickener, stabilizer, and emulsifier (Hassan, 2010).
Sterculia is a drought-tolerant plant found primarily in South and Southeast Asia, including countries like Laos, China, Thailand, Cambodia, India, and the Philippines, as well as in Africa In Vietnam, it thrives in the Central Highlands and South Central provinces, particularly in Kom Tum, Gia Lai, Dak Lak, Khanh Hoa, Ninh Thuan, and Binh Thuan The best quality Sterculia is found in the wild in Phuoc Dinh commune (Ninh Phuoc - Ninh Thuan) While Sterculia is also cultivated in rainier areas like Hanoi and Ho Chi Minh City for shade, the excessive rainfall negatively impacts its quality.
The tree typically reaches an average height of up to 30 meters and features gray-brown bark that is either broken or mottled Its young leaves exhibit a pinkish hue, with petioles measuring 10 to 20 centimeters and palmately complex structures that have an acute base on extremely short petioles, clustered at the apex The flowers, measuring 20 to 25 millimeters in diameter, are arranged in loose, racemose panicles that are 10 to 15 centimeters long These apetalous flowers have a deeply 5-partite calyx, which is glabrous with a red interior and greenish lobes The stamens form a column with anthers that transition from yellow to crimson The woody-fibrous follicles are stout, dehiscent along the ventral suture, and typically found in clusters of 2 to 5, maturing to a green or reddish color with thick walls, measuring 5 to 8 centimeters long and nearly as wide The seeds are purplish black, velvety, ellipsoid or oblong in shape, measuring 2.5 to 3 centimeters long, and feature a small waxy yellow rudimentary aril at one end.
Figure 2.1 Sterculia tree and KG
After reaching maturity between 5 to 7 years, KG is harvested by making small holes in the trunk, allowing the exudates to flow out The trunk of the Sterculia tree heals after harvesting, preparing it for future crops The harvested gum is typically ivory white, with possible variations of slight yellow or opaque white, and possesses a sweet taste along with cool properties Rich in trace elements and minerals, including 102 mg of magnesium, 360 mg of potassium, and 50 mg of zinc, KG offers numerous health benefits and applications in various industries Its high value is reflected in its market price, ranging from 200,000 to 300,000 VND per kilogram.
KG offers numerous health benefits, including blood sugar regulation, liver detoxification, and cooling effects, while also providing essential fiber These properties contribute to preventing acne related to internal heat and reducing the risk of liver cirrhosis.
KG is rich in essential minerals like potassium (K), sodium (Na), calcium (Ca), and zinc (Zn), which help prevent skin aging and nourish the blood Additionally, KG supports the digestive system due to its strong water-absorbing properties, promoting intestinal swelling and facilitating digestion As a result, KG is regarded as an effective remedy for constipation, flatulence, and heartburn.
KG offers a light sweet taste that is highly beneficial for individuals with high blood pressure and diabetes, while also preventing heart disease and atherosclerosis Additionally, it serves as a denture adhesive in dentistry and possesses antibacterial properties, making it a key ingredient in dental disease medications Furthermore, KG aids insomniacs in achieving better, deeper sleep and helps reduce stress after long working days, making it an excellent food choice for health promotion and recovery.
The polysaccharide's molecular weight is said to be in the range of 9,000–16,000 kDa or from
9 x 10 6 to 16 x 10 6 g/mol The average molecular weight of native gum which dissolves in the cold water is e 2–5 x 10 6 g/mol by using light scattering
The chemical composition of Sterculia (KG) varies significantly based on tree species and origin KG primarily consists of high molecular weight acetylated polysaccharides, particularly of the substituted rhamnogalacturonoglycan type Hydrolysis reveals that KG contains approximately 30–43% galacturonic acid, 13–26% galactose, and 15–30% rhamnose Additionally, it has about 37%–40% uronic acid residues and around 8% acetyl groups, with free acetic acid released during aging Native KG is insoluble in water, swelling only due to acetyl groups, with 10% solubility in cold water and 30% in hot water Deacetylation with dilute ammonia increases solubility to 90%, while alkaline treatment alters its properties and enhances water solubility Notably, KG has a lower protein content compared to other exudate gums, at approximately 1%.
The gum main chain is formed by α-D-galacturonic acid and L-rhamnose units Side chains are linked to the main chain by 1,2-β-D- galactose bounds or 1,3-β-D-glucuronic bound for galacturonic (Figure 1)
Figure 2.2.Chemical structure of KG
The gum was physico-chemically analyzed The composition of cations has been determined
Calcium is the most abundant mineral found in gum, followed by magnesium, potassium, sodium, iron, manganese, cobalt, zinc, and copper The estimated values for the Blue Nile and Kordofan samples indicate moisture levels of 12.5% and 13%, ash content of 7.1% and 7.0%, pH values of 4.8 and 4.7, nitrogen content of 0.08% for both, and protein levels of 0.56% for each sample, as detailed in Table 2.1.
; +3), viscosity (720 ; 690) ml/gm, equivalent weight (680 ;655) and uronic acid (27.3 ; 29.6)%
Table 2.1.The physicochemical properties of KG from Blue Nile and Kordofan
Table 2.2.Mineral composition of KG (àg/g) from Blue Nile and Kordofan regions
The insolubility of OKG in water is primarily influenced by the quantity of acetyl groups and the interactions with multivalent metal ions, although the exact impact of these factors on GK's insolubility remains unclear (Postulkova et al., 2017) The specific positioning of acetyl groups within the KG chain is not fully understood, but they can attach to the primary hydroxyl group on the sixth carbon of the galactose unit, contributing to the hydrophobic nature of OGK (Verbeken et al.) Acetyl groups, which constitute about 8% of the weight, can be removed from the OGK backbone under alkaline conditions (Wuts & Greene, 1999) Additionally, divalent ions, such as Ca²⁺, can crosslink anionic groups through electrostatic interactions, potentially affecting OGK's solubility (Singh & Sharma, 2009) Strong hydroxide treatment can convert polyvalent ions to monovalent ions, further increasing GK's solubility (Silva et al., 2003).
According to a study by (Postulkova, Chamradova, Pavlinak, Humpa, Jancar, & Vojtova,
2017) the best conditions for increasing KG’s solubility after hydrolysis with 1M NaOH and 1M
KOH with 2% KG solubility in water at ambient temperature Due to the feature of esterification by Tetrapropenyl succinic anhydride by glucosyl groups connected to carboxyl groups present in
Esterified KG exhibits higher solubility than unhydrolyzed KG but lower than hydrolyzed KG due to the replacement of some hydroxyl groups with ester groups Esterification enhances particle size, solubility, swelling, and water absorption (Ačkar et al., 2015) The process disrupts hydrogen bonds within the molecules, preventing re-bonding and rendering the esterified complex resistant to reversible deterioration.
2.1.3 Properties a Physical properties: KG has a pink-grey color and a slightly acidic flavor and smell when plastified with various chemicals such as glycols; it can produce soft films when plastified with various chemicals such as glycols b Solubility: KG has a great capacity to bond with water molecules; however, gum particles are not totally solubilized, resulting in a process known as swelling, which is defined as an increase in total volume in relation to dry mass of up to 60 times the original volume KG has less solubility compared to commercial gum on the market due to the presence of the acetyl group c Rheological properties: Because of the acetyl groups in the gum's structure, KG is the least water-soluble of the gum group In 0.5% dispersions, the viscosity of KG is around 120-400 centipoices (cPs), while in 3% dispersions, it is around 10,000 cPs Viscosity increases linearly in a concentration-dependent manner in low-concentration solutions until it reaches 0.5% KG concentration With increasing time, viscosity in powdered form diminishes
The stability of KG dispersions is significantly affected by pH, with optimal stability observed at a pH range of 4.5-4.7 for a 1% dispersion Introducing acids or alkalis reduces viscosity, but complete hydration of the gum prior to pH adjustments can enhance it However, when the pH exceeds 8, irreversible changes occur, compromising the gum's dispersion properties due to the loss of acetyl groups KG dispersion is resilient in acidic conditions, thanks to its high uronic acid content, and can endure hydrolytic activity even at a 10% hydrochloric acid concentration Additionally, KG dispersion is thermolabile; heating alters the polymer conformation, leading to increased solubility and a permanent reduction in viscosity Cold water dispersions can reach concentrations of 5%, while hot water at low pressures can achieve 18% to 20% Furthermore, most gum products are vulnerable to microbial attack unless antibacterial agents like benzoic acid, sorbic acid, or para-hydroxybenzoates are incorporated, as specified in food formulations.
KG serves as an effective bulk laxative by forming a mucilaginous gel when in contact with water, making it beneficial for treating diverticular disease Additionally, it is utilized in the production of pressure-sensitive masking tapes, medical jellies, pastes, dentine adhesives, and medical adhesive tapes for stomatitis treatment.
Introduction of ingredients
Glycerol, also known as glycerin or 1,2,3-propanetriol, is a colorless and odorless syrupy liquid with the chemical formula C3H8O3 This organic polyol complex contains three hydroxyl groups and three carbon atoms, giving it the IUPAC name 1,2,3-propanetriol Glycerol is non-hazardous, with a molecular weight of 92.094 g/mol, a boiling point of 290°C, and a melting point of 17.9°C.
Glycerol is not soluble in volatile and fixed oils, but it is highly soluble in water due to the polyol groups that can form hydrogen bonds with water molecules.
Glycerol plays a crucial role in maintaining the flexibility and strength of materials such as cellophane, high-quality paper, and textiles It is widely used in various industrial applications, including the production of resins, detergents, polymers, tobacco, cosmetics, and personal care products In the food industry, glycerol serves multiple functions as a smoothing agent, sweetener, humectant, and solvent for food colors and flavors, making it essential for the development of flexible and active films.
In the field of microbiology, glycerol compounds have the ability to stimulate the growth of microorganisms
The Henry's law constant for glycerol, indicating its maximum solubility, is calculated to be 9.75×10^{-6} Pa m^{3} mol^{-1}, reflecting its low volatility with a vapor pressure of 0.000106 hPa at 25℃ Glycerol is easily biodegradable and predominantly enters water upon environmental discharge, with minimal amounts found in sediment, air, or soil (M.J Wernke, 2014).
Figure 2.5.The chemical structure of glycerol (M.J.Wernke, 2014)
Sodium triphosphate (STPP) is a colorless, water-soluble salt available in anhydrous and hexahydrate forms, known for its alkaline properties This versatile chemical is widely used in various industries, serving as a food preservative and a key ingredient in cleaning products.
Sodium triphosphate, also referred to as pentasodium tripolyphosphate, is identified by the E451 food additive number in Europe This compound not only absorbs calcium and magnesium but also enhances alkalinity, complexes transition metal ions, and stabilizes metal oxide colloids Its significant surface charge enables the peptization and suspension of various soils.
Sodium tripolyphosphate has the molecular formula Na5P3O10 STPP is structurally composed of ten bonded oxygen atoms, three phosphorus atoms, and five sodium atoms
Figure 2.7.Sodium tripolyphosphate structure (Fahim, kheireddine, & belaaouad, 2013) ã The production process of STPP typically consists of three main steps
1 When phosphoric acid and sodium compounds, such as sodium hydroxide (NaOH) or sodium carbonate (Na2CO3), react, a mixture of monosodium phosphate (NaH2PO4) and disodium
12 phosphate is created (Na4HPO4) The production of phosphoric acid involves either a wet method or a calcination process
2 Insoluble contaminants are eliminated once the combination precipitates from solution into a solid
3 Heat the mixture until it thermally decomposes, or heat sodium tripolyphosphate (Na5P3O10) from mono- and disodium phosphate Additionally, heating makes sure that extra water is evaporated The range of temperature for heating the mixture is 500°C to 550°C
The reaction equation is: NaH2PO4 + 2Na2HPO4 → Na5P3O10 + 2H2O
The product is then ground into a fine powder, screened and packaged before being put on the market
The two primary methods for producing STPP grades are the traditional spray process and the single-stage dry method, each of which has pros and cons of its own
Figure 2.8 Flow chart showing the classic spray method (CM) and the dry single-stage method (DSM) of STPP production ã The usages of Sodium tripolyphosphate:
STPP serves multiple functions, including acting as a bleaching agent, corrosion inhibitor, anti-scale agent, detergent, dye, plating agent, surface treatment agent, solids separator, cleaning solvent, and degreasing agent It is widely utilized in industrial cleaners, surfactants, emulsifiers, and water softeners.
Sodium tripolyphosphate (STPP) serves as an effective detergent due to its ability to adsorb calcium and magnesium, produce alkalinity, and stabilize metal oxide colloids Its primary role is to bind and neutralize the calcium and magnesium ions that contribute to water hardness STPP is widely utilized in the formulation of washing powders, dishwashing liquids, and industrial water softeners, thanks to its properties such as metal ion chelation, suspension, dispersion, emulsification, and pH buffering Additionally, it finds applications in leather goods, industrial washing, degreasing agents, and dyeing aids.
Sodium tripolyphosphate (STPP) is primarily used in the food industry to preserve red meat, poultry, and seafood by enhancing their moisture retention and softness during storage and shipping It is also commonly found in pet food, such as dog and cat food, where it helps bind water and maintain freshness Furthermore, STPP plays a role in preserving the quality of beverages, including milk and juices (Robinson, 2022).
STPP is a multifunctional ingredient recognized as safe (GRAS) by the FDA when used in the food industry according to good manufacturing practices Its safety has also been validated by the JECFA, confirming its roles as a sequestrant, binder, and thickener In the European Union, STPP is acknowledged as a food additive and can be utilized as a carrier for color anthocyanins and in the preparation of salted fish from the Gadidae family.
Some users argue that it is unhealthy due to potential adverse effects, including allergic reactions, and that it contains chemicals typically found in detergents that are not safe for consumption.
Figure 2.9.The structure of Benzoic anhydride
“Benzoic anhydride is the organic compound with the formula (C 6 H 5 CO) 2 O It is acid anhydride of benzoic acid and the simplest symmetrical aromatic acid anhydride It is a white solid.”
In the presence of H3PO4, benzoic acid and acetic anhydride are heated to create benzoic anhydride
2C6H5CO2H + (CH3CO)2O → (C6H5CO)2O + 2CH3CO2H
Besides, according to Peter T Gallagher at el Palladium-catalyzed carboxylation of arenes with carbon monoxide at 15 bar results in the production of BA, with a yield from benzene of 32%
Zeavin et al investigated the reaction of benzoyl chloride with benzoic acid derivatives in the presence of pyridine, yielding asymmetric aromatic anhydrides with good to exceptional yields They noted that some of these anhydrides, such as 4-bromobenzoyl benzoic acid anhydride, exhibit instability, melting at 82–83 °C, hardening at 86 °C, and then melting again at 165–182 °C Upon solidification, the product was found to be a mixture of 4-bromobenzoic anhydride and benzoic acid.
Benzoic anhydride is primarily utilized as a benzoylating agent in the production of industrial chemicals Recent studies by D Seidel and colleagues have demonstrated the use of benzoic anhydrides and other cost-effective reagents in acylation processes to create compounds suitable for isomeric resolution Furthermore, benzoic anhydride serves as a key component in the production of dyes and intermediates.
Tetrapropenyl succinic anhydride (TPSA), also known as dodecenyl succinic anyhydride (DDSA), is one of the liquid anhydride hardeners
The molecular formula for TPSA is C16H26O3, representing its chemical structure defined by the arrangement of atoms and the bonds that connect them In the STPP+TPSA molecule, there are a total of 45 bonds, including 19 non-H bonds, three multiple bonds, six rotatable bonds, three double bonds, one five-membered ring, two aliphatic ester bonds, and one anhydride bond (-thio) Most molecular editors are capable of importing the TPSA string.
CC(C)CC(C)CC(C)C=C(C)C1CC(=O)OC1=O, enabling transformation back into two- dimensional or three-dimensional models of the TPSA compound
MATERIALS AND METHODS
Materials and equipment
- NaHCO3 1.5M, Acid acetic (CH3COOH) 20%,
- 4-digit scale, 2-digit scale, electronic caliper
- Heated magnetic stirrer, pH meter,
- Necessary tools such as erlen, barker, pipette, volumetric flask,
Analytical methods
• UV-Vis absorption spectrum and transmittance
Figure 3.1.Flow chart summary of the research process
3.2.2.1 Process of hydrolyzed KG in alkaline condition
Figure 3.2.Method of hydrolysis of KG
A total of 2g of KG was added to 100 mL of distilled water at room temperature and allowed to hydrate for 24 hours to facilitate swelling Following this, varying volumes of 1.5M NaHCO3 (10mL, 20mL, 40mL, and 80mL) were introduced to the KG suspension, which was then stirred and boiled for approximately 30 minutes until the KG dissolved To neutralize the excess NaHCO3 and eliminate any remaining CO2, 20% acetic acid was added The resulting mixture was then precipitated using 98% v/v ethanol, filtered, and washed twice with 70% v/v ethanol The precipitated HKG was cut into small pieces and dried at 55°C for 12 hours, after which the powdered samples were stored in zip bags.
Figure 3.3.Process of esterified KG with STPP+TPSA/STPP+BA
At room temperature, 2 g of the weighing KG was mixed with 100 mL distilled water To make
KG is hydrated in water for 24 hours before adding 80 mL of a 1.5M NaHCO3 solution, followed by stirring and heating for 30 minutes The mixture is allowed to react for 2 hours, then treated with 2 g of STPP and 1.42 mL of tetrapropenyl succinic anhydride (or 1.7 g of benzoic anhydride), and neutralized with 20% acetic acid to achieve a pH of 4.0 to 4.5 The conditioned KG is kept at 4°C for 12 hours, after which the esterified KG is precipitated using 98% ethanol, filtered, and washed twice with 70% v/v ethanol The precipitate is then cut into small pieces and dried for 12 hours at 55°C Finally, the powder samples are finely ground and stored in zip bags.
Starch-gum films were developed following the method of Anjum Nawab et al., with modifications Initially, 0.3g of MKG powder was dispersed in 40ml of distilled water for 24 hours Subsequently, 0.3g of cornstarch and varying concentrations of glycerol (10%, 15%, 20%, and 25% v/w) were added to the gum mixture The combined mixture was heated to 95°C and maintained for 20 minutes to ensure complete gelatinization of the starch After homogenization into a uniform solution, it was poured into a petri dish, dried at 45°C for 24 hours, and then stored at 80% relative humidity for a minimum of 48 hours (Nguyen et al., 2022).
3.2.3 Characterization of Modified KG Powder
Fourier transform infrared spectroscopy (FTIR) is utilized to identify and classify molecules based on their atomic vibrations, which absorb specific frequencies of infrared radiation Analytes with functional groups such as esters, aldehydes, and carboxylic bonds (C-O, C=O, O-H) can absorb in the mid-infrared region The analysis involves measuring samples with infrared wavelengths ranging from 400 to 4000 cm\(^{-1}\) The dried powder sample is placed on a diamond ATR substrate for scanning the IR spectrum (Nguyen et al., 2022).
The solubility of KG powder was assessed by dissolving 0.2 g in 50 mL of distilled water for 24 hours at room temperature After centrifugation at 3000 rpm for 15 minutes, the clear solution was transferred to a Petri dish, weighed, and dried at 105°C for 24 hours The mass of the solids was then determined, and the solubility was measured in triplicate using the specified formula (Nguyen et al., 2022).
S% = (msol msoln) ×100 Where, msol: the mass of solid after drying (g) msoln: the mass of clear solution before drying (g)
The swelling capacity of a powder is defined by the amount of water it can absorb, with 1 gram of powder serving as the standard measure For complete dissolution, 0.2 grams of the powder should be immersed in 50 milliliters of distilled water.
The mixture was centrifuged at 3000 rpm for 15 minutes and then placed on a pre-weighed petri dish The combined weight of the petri dish and mixture was recorded before drying, followed by a drying period of 24 hours at 105°C After drying, the dishes were weighed again to determine the mass of the solids, with the experiment being repeated three times The swelling was calculated using a specific formula.
𝑚 𝑠𝑜𝑙 (ml/g) Where, msol: the mass of solid after drying (g) msoln: the mass of clear solution before drying (g)
Weigh 0.5 g of KG powder samples: original, hydrolyzed and esterified, put in a plastic petri dish and spread evenly Then weigh both the mass of the dough and the plastic dish The beakers were placed in an environment with a relative humidity of about 80% RH at room temperature The beakers are weighed every 1 h for 48 h The moisture absorption of the powder was determined from the increase in mass of the beaker after 1 h Plot a graph of the powder's moisture absorption over time The moisture absorption of the powder at time t is calculated by the formula:(Nguyen et al., 2022)
M%= (mt-mi mi ) × 100 Where, mt: is the mass of powder after time t (g) mi: is the initial mass of the powder at t = 0 (g)
The study involved preparing powder samples of OKG, HKG, and EKG, which were dissolved in water at concentrations of 0.5%, 1%, and 2% (w/v) using 30ml of water in each solution within a 100ml beaker Subsequently, 6ml of oil was added to each mixture, which was then homogenized at 8000 ± 200 rpm After homogenization, the emulsions were transferred into test tubes and observed over a period of 7 days The emulsion stability index (ESI) was calculated to assess the stability of the emulsions.
HE: the initial emulsion height (cm)
HS: the serum height (cm)
3.2.3.4.2 Oil particle size in emulsion
After homogenization, transfer a small sample of the emulsion into a test tube, then place a few drops on a slide for microscopic observation connected to a computer within a week (Wang, Tian, & Xiang, 2020)
50ml of distilled water is used to dissolve 0.1g of KG powder over the course of 24 hours For
15 minutes, centrifugation at a speed of 3000 rpm is employed to separate the insoluble materials
To determine the amount of soluble solids in a clear solution, 10 ml was dried at 105°C until a constant mass was achieved Following this, the mixture was diluted to achieve a dry matter concentration of 0.1 percent (w/v) The viscosity of the solution was then measured using an Ostwald capillary viscometer with a diameter of ỉ = 0.3 mm, timing the passage of the liquid through the device.
23 solution and drop of distilled water, and then calculate the relative viscosity (η) Measure 3 times for each sample Relative viscosity is determined by the formula: (Nguyen et al., 2022)
𝑡 𝑤𝑎 Where: tsoln: time the solution flows through the viscometer (s) twa: time taken for distilled water to pass through the viscometer (s)
0.25g of KG powder is dissolved in 50ml of distilled water in 15 minutes, and a few drops of phenolphthalein are added as an indicator The sample is titrated with NaOH 0.1N solution until the light pink of phenolphtalein appears After titration by NaOH, the sample is added with 15ml of NaOH 0.1N solution and heated for 30 min for the reactions to take place A 0.1 N HCl solution was prepared to titrate the sample, adding 0.1 N HCl slowly until the pink color in the mixture disappeared acid value= 𝑉 𝑁𝑎𝑂𝐻 𝐶𝑛 𝑁𝑎𝑂𝐻
VNaOH: the volume of NaOH 0.1N is titrated (ml) m: the weight of sample (g) nester + nCOOH in KG = 15.𝐶𝑛 𝑁𝑎𝑂𝐻 −𝑉 𝐻𝐶𝑙 𝐶𝑛 𝐻𝐶𝑙
DE=(nester+nCOOH)-acid value Where:
VHCl: the volume of HCl 0.1N is titrated (ml) m: the weight of sample (g)
DE: degree of esterification (mmol/g)
Tensile strength measurements of the films were conducted using a structural measuring device at room temperature (30°C) and controlled relative humidity The films were maintained at 80% relative humidity for 48 hours before testing Film samples, sized 40mm x 12mm, were secured at both ends to the device's axes The gauge was operated until the upper shaft began to rise, at which point the stretching continued until the film broke Each sample was tested three times in duplicate to ensure accuracy.
The elongation of the film was calculated according to the formula (Standard & ISO, 1996):
In there: Ɛ: is the strain value of the film at break in percentage (%)
L0: is the original length of the sample (mm) ΔL: is the additional length of the sample (mm)
3.2.4.2 Moisture content, water uptake, solubility
The 30x30 mm cut films were initially weighed (W0) and then dried at 105°C for 24 hours to obtain the weight after drying (W1) After drying, the films were soaked in 20 mL of distilled water at room temperature for 24 hours, followed by the removal of excess water with filter paper The film surfaces were then dried with a clean paper towel before weighing (W2) The samples were dried again at 105°C for another 24 hours, and the final weight (W3) was recorded once the films were completely dry Each sample was measured three times in duplicate (Nguyen et al., 2022).
The moisture content (MC) is determined according to the following formula:
𝑊0 x100 (%) The following formula was used to calculate the water uptake (WU):
𝑊3 x100 (%) Water solubility (WS) is determined according to the following formula:
W0 is the initial film mass (g)
W1 is the weight of the film after drying (g)
W2 is the weight of the film after immersion (g)
W3 is the mass of the dried film after soaking (g)
The water vapor permeability (WVP) of the film was determined according to the ASTM E-
The 96 method involves using glass test tubes filled with dry silica gel to create a 0% relative humidity environment Film samples are sealed at the tube's mouth and placed in an environment with approximately 80% relative humidity at room temperature Over a period of 48 hours, the beakers are weighed hourly to measure the increase in mass, which is used to calculate moisture permeability A graph is plotted based on linear regression (r² > 0.99) to determine the slope from the data on the increasing mass of the cup over time.
RESULTS AND DISCUSSION
Characterization of modified KG powder
4.1.1 FTIR – Fourier Transform Infrared Spectroscopy of the powder and X-ray diffraction (XRD)
4.1.1.1 FTIR – Fourier Transform Infrared Spectroscopy
The FTIR spectrum reveals a material's capacity to absorb infrared light, enabling the identification of chemical bonds and their characteristic vibrations This technique facilitates the observation of structural changes in KG before and after the modification process.
Figure 4.1.FTIR spectra of hydrolyzed KG powders Table 4.1.Some characteristic peaks in FTIR spectra of the hydrolyzed KG powders
The FTIR spectrum, illustrated in Figure 4.1, reveals the presence of functional groups in the hydrolyzed KG powders, supported by the accompanying peak analysis table.
The hydrolysis samples exhibited similarities with increasing bicarbonate concentration, particularly at the absorption band of 3304 cm\(^{-1}\), where OH groups from galactopyranose and glucopyranose rings showed a consistent degree of association (Singh & Pal, 2008) Notably, at 2365 cm\(^{-1}\), differences emerged among the hydrolyzed samples; higher bicarbonate concentrations correlated with lower absorption frequencies, indicating that acetyl groups were replaced by OH groups, thus increasing hydrogen bonds The spectrum also revealed bands at 1718 cm\(^{-1}\), suggesting a richness in uronic acids characterized by carboxylic groups (CostaSilva et al., 2020) Additionally, a slight decrease in frequency was observed in hydrolyzed samples, with the carbonyl group C=O remaining partially intact due to incomplete removal of acetyl groups by the sodium bicarbonate hydrolysis agent In contrast, another study noted that the FITR spectrum of hydrolyzed samples lost the C=O stretching peak entirely when sodium hydroxide was used in a strong alkaline medium (Nguyen et al., 2022) Despite the partial loss of acetyl, an increase in OH groups was evident at the peak of 1402 cm\(^{-1}\) Furthermore, the spectrum of GK and other hydrolyzed samples in the fingerprint region (1200-950 cm\(^{-1}\)) corresponded to the C-O-C stretching vibration present in the gum ("IR Spectrum Table & Chart," 2022).
Figure 4.2.FTIR spectra of original, hydrolysis and esterified samples
Table 4.2.Some characteristic peaks in FTIR spectra of the modified KG samples
The spectra of esterified KG samples, along with hydrolyzed and OKG samples, reveal notable differences The ester sample combining STPP and TPSA exhibits spectral similarities to the original sample In the STPP+BA esterification combination, the peak at 1693 cm\(^{-1}\) indicates a stronger C=O bond due to the formation of carbonyl groups from benzoic anhydride during the esterification process Additionally, the peak at 1369 cm\(^{-1}\) shows a significantly stronger O-H stretching absorption compared to the OKG sample.
The X-ray diffraction of the KG samples H20, H80, STPP+BA, and STPP+TPSA is shown in figure 4.3 The diffraction lines of the samples have almost the same shape The diffraction line of H80 does not have any conspicuous sharp peaks, as can be seen in the diagram However, sample H20 has a little peak at angle 2θ = 22.09 o On the X-ray diffraction lines of the STPP+BA and STPP+TPSA samples, several strong peaks formed, starting with the H80 sample and continuing through the esterification phase Each of the three powder samples' amorphous characteristics are depicted in the figure (STPP+BA, STPP+TPSA and H20)
A study conducted by Yousuf, Wu, and Gao (2021) revealed that X-ray diffraction analysis of KG film produced a flat and non-greasy diffraction pattern, indicating the absence of oil.
The diffraction plots of the film samples, excluding the control sample, reveal distinct diffraction patterns and peak intensities, while the additional oleogel shows no significant peaks.
KG film lacks distinct peaks, a sign of crystal diffraction The film crystallized as a result of the interaction with the oil
KG is insoluble in water due to the presence of acetyl groups and interactions with multivalent metal ions in its structure An evaluation of the solubility and swelling ability of KG was conducted before and after modification, yielding significant results.
Figure 4.4.Solubility of KG samples
The solubility of hydrolyzed KG increases with the concentration of 1.5M NaHCO3 solution, with OKG exhibiting the lowest solubility at 0.05% This increase in solubility is attributed to the replacement of acetyl groups (COO-) with hydroxyl groups (OH-), with maximum solubility reaching 0.45% for KG hydrolyzed with H80, which is nine times higher than that of OKG The solubility of STPP+BA is 0.09%, approximately twice that of the original KG but five times lower than the hydrolyzed sample Meanwhile, STPP+TPSA shows a solubility of 0.2%, which is 2.25 times less than H80 and four times greater than OKG, due to the esterification of glucosyl groups connected to carboxyl groups in KG followed by a hydrolysis reaction.
NT H10 H20 H40 H80 STPP+TBA STPP+TPSA
The solubility of esterified KG is greater than that of unhydrolyzed KG but less than that of hydrolyzed KG, as ester groups replace some hydroxyl groups.
KG is a hydrophilic colloid with limited water solubility When mixed with aqueous liquids, it does not form a homogeneous solution; instead, it maintains its identity as a distinct particle that expands significantly in size.
Figure 4.5 Swelling of KG samples
The swelling of hydrolyzed samples increased steadily with the rising concentration of 1.5M NaHCO3 solution, indicating a strong correlation between water absorption and solubility in KG samples Hydrolyzed KG samples exhibited significant weight gain due to their high hydration capacity, with OKG and H10 showing similar swelling levels Notably, the water absorption at the highest hydrolyzed concentration (H80) was six times greater than that of unhydrolyzed KG Among the esterified KG samples, STPP+BA demonstrated less swelling compared to STPP+TPSA This increase in water absorption per gram of KG powder post-transformation is attributed to the higher number of hydroxyl groups in hydrolyzed KG as the concentration of NaHCO3 solution increased.
NT H10 H20 H40 H80 STPP+TBA STPP+TPSA
Figure 4.6.Moisture uptake of KG samples
The moisture uptake of hydrolyzed KG samples is significantly higher than that of esterified KG samples, correlating with the concentration of hydrolysis by NaHCO3 Hydrolyzed KG samples exhibited a rapid increase in moisture uptake from 0 to 15 hours, stabilizing thereafter Although esterified samples also showed a quick rise in moisture uptake during this period, they remained lower than the hydrolyzed samples, with both types surpassing the moisture uptake of unhydrolyzed samples Overall, most samples demonstrated a gradual increase in moisture uptake over 48 hours.
The original KG sample exhibits lower moisture uptake compared to modified KG samples due to its higher concentration of acetyl functional groups, which inhibit hygroscopicity Hydrolysis with NaHCO3 transforms acetyl groups into hydroxyl groups, resulting in increased solubility and moisture absorption in hydrolyzed KG In contrast, esterified KG has fewer hydroxyl groups, as some are converted to ester groups, leading to reduced water absorption and moisture uptake when compared to hydrolyzed KG samples.
The majority of the gum powders have substantially greater moisture uptake capacity than the original KG sample and very fast moisture uptake capacity when the original KG:KG, hydrolyzed
A comparison between KG and esterified KG samples reveals that the molecular structure, rich in hydroxyl groups from compounds like galactose, mannose, and glucose, leads to enhanced water solubility, moisture retention, stability, and productivity compared to OKG.
H10 H20 H40 H80 STPP+ BA STPP+TPSA OKG
Figure 4.7.Relative viscosity of powder samples
Characterization of modified KG film
4.2.1 Tensile strength (TS) and elongation at break (EAB)
The tensile strength of films is a crucial property for food packaging, as it determines their ability to withstand stretching and protect food during storage and transit The following results illustrate the tensile characteristics of KG films.
OKG H10 H20 H40 H80 STPP+ TPSA STPP+ BA
Table 4.5.Results of tensile strength and elongation at break
Sample %Glycerol Thickness TS (mPa) EAB (%)
Figure 4.15.Tensile strength and elongation at break of films at 10% of glycerol
The data in table 4.4 indicates that as glycerol concentration increases, the tensile strength of the film consistently decreases while the elongation at break rises This trend is observed in both esterified and hydrolyzed KG films Higher glycerol concentrations lead to a notable increase in elongation at break and a gradual decline in tensile strength, attributed to the weakening and increased flexibility of the film texture Additionally, the presence of hydroxyl (OH-) groups in the structure of OKG, as opposed to carbonyl groups, facilitates the binding of glycerol and water within the film.
KG interacts intramolecularly to form a strong network, resulting in hydrolyzed KG films that are less rigid and more pliable due to fewer cross-links When comparing KG esterified films to H80 films, the elongation at break (EBA) is lower However, the substitution of some OH- groups with ester groups makes the KG films less flexible than the H80 films.
OKG H10 H20 H40 H80 STPP+BA STPP+TPSA
The study by Yousuf, Wu, and Gao indicates that incorporating Schisandra chinensis oil and oleogel into the KG film formulation results in a reduction of the film's tensile strength.
Wu and Gao (2021) demonstrated that incorporating oleogel does not effectively reduce traction when oil is added They concluded that oleogel helps maintain the integrity of the biopolymer matrix in KG films However, the introduction of oil components into the film formulation is expected to disrupt the biopolymer network, leading to increased flexibility but reduced tensile strength (Fabra, Talens, & Chiralt).
In a study conducted by Gahruie, Ziaee, Eskandari, and HashemHosseini (2008), the incorporation of Zataria multiflora essential oil into basil seed gum films was shown to have a plasticizing effect This modification led to an increase in the elongation at break of the films, enhancing their flexibility and performance.
4.2.2 Moisture content, water uptake, solubility
Figure 4.16.Moisture content of samples according to glycerol concentration
Mo is tu re con ten t (% )
Original H10 H20 H40 H80 STPP+BA STPP+TPSA
Figure 4.17.Water uptake of samples according to glycerol concentration
Figure 4.18.Water solubility of samples according to glycerol concentration
A crucial characteristic of films made using OKG and modified samples is their water solubility, which includes water uptake as well as water solubility To strengthen product integrity
Original H10 H20 H40 H80 STPP+BA STPP+TPSA
Wa ter s o lu b ili ty (% )
Original H10 H20 H40 H80 STPP+BA STPP+TPSA
Water resistance and potential functionalities require water insolubility, but in cases like meal encapsulation or additives, water solubility before consumption is crucial The results indicate a consistent trend across the analyses of moisture, water uptake, and water solubility.
In general, the more glycerol concentration is present in the samples of modified KG film, the higher the moisture content, water absorption, and water solubility
The moisture level significantly influences the physical and barrier properties of KG films (AGHAZADEH et al., 2018) Glycerol concentration plays a crucial role in determining these properties, with the original sample exhibiting the highest water uptake, followed by hydrolyzed and esterified samples The observed increase in water absorption with higher glycerol concentrations can be attributed to glycerol's three hydrophilic hydroxyl groups, which enhance its solubility and hygroscopic nature Additionally, glycerol's flexibility allows it to form both internal and external hydrogen bonds, contributing to the overall characteristics of the films.
(Tarique, Sapuan, & Khalina, 2021) In the aqueous phase, glycerol is stabilized by a combination of intramolecular hydrogen bonds and intermolecular solubilization of hydroxyl groups
The incorporation of glycerol into film formulations enhances the distance between sample molecules due to its ability to interlace among them, thereby acting as an effective plasticizer (Tarique et al., 2021) This aligns with Sobral et al.'s findings that plasticizers disrupt intermolecular interactions among polymer molecules Additionally, higher concentrations of glycerol increase the film's moisture content, as its hydrophilic nature reduces the forces between adjacent macromolecules Consequently, the addition of glycerol significantly improves various properties of KG films, including moisture uptake, solubility, water absorption, and elongation of flexible film samples.
Water vapor permeability refers to the ability of a film to allow water molecules to pass through its substrate As ambient temperature and relative humidity increase, the film tends to absorb more moisture, leading to higher water vapor permeability This increased moisture content can cause the film to swell, further enhancing the transmission of water vapor Additionally, the properties of the film are greatly affected by the composition of the film-forming solution.
Low water vapor permeability is crucial in packaging as it helps minimize moisture transmission between food and its environment or between different components of a food product This characteristic significantly enhances the performance of packaging films.
Figure 4.19.Water vapor permeability of films
Original 10 20 40 80 STPP+BA STPP+TPSA w vp (x10 -9 )
Samples10%gly 15%gly 20%gly 25%gly
Table 4.6.The values of WVP of films
The water vapor permeability (WVP) of the KG film without oil or oleogel is 5.58x10⁻⁹ g.s⁻¹.m⁻².Pa⁻¹ (Yousuf et al., 2021) Incorporating oil into the films leads to a gradual decline in WVP, highlighting the superior water vapor barrier properties of oil-containing composite films When 10% glycerol is added, the WVP of the original KG film decreases to 2.52x10⁻⁹ g.s⁻¹.m⁻².Pa⁻¹, representing a two-fold reduction compared to the original KG film Similarly, films subjected to hydrolysis and esterification show moisture permeabilities ranging from 1.4 to 2.50x10⁻⁹ g.s⁻¹.m⁻².Pa⁻¹, which is nearly 50% lower than the initial KG film without glycerol.
Sample %Gly Wvp Sample %Gly Wvp
The incorporation of oil/oleogel into film formulations significantly reduces water vapor permeability (WVP) due to its hydrophobic properties The films' composition and spatial distribution within the substrate play a vital role in influencing WVP and other related parameters A critical factor is the hydrophilic to hydrophobic ratio of the film's constituents, as water vapor transfer predominantly occurs through the hydrophilic sections By increasing the hydrophobic components, the addition of oil to the macromolecular matrix effectively enhances the films' water vapor barrier Research by Yousuf et al (2021) demonstrates that integrating oleogel, a hydrophobic element, into film structures can lead to a substantial reduction in WVP, with a notable 61.64% decrease observed when oil concentration was increased to 7.5% compared to pure KG film.
4.2.4 UV-Vis Spectra and Transparency of the film
The transparency and ultraviolet barrier properties of films are essential for food packaging applications, with UV-vis spectroscopy playing a key role in assessing these characteristics These properties are vital in preventing oxidation, protecting sensitive components, and minimizing color loss in packaged products Additionally, film thickness significantly influences these measurements, as higher transmittance indicates greater transparency depending on the technique used.
Table 4.7.Average percent light transmittance of samples at UV-Vis region
Sample %Glycerol UV-Vis area
Table 4.7 reveals that most films exhibit low absorbance, with light transmittance and transparency not exceeding 10%, except for a few films that show slightly higher light transmission in the UV-vis region In this region, the majority of film samples demonstrate an increase in transmitted light However, the impact of varying glycerol concentration on the light transmittance and transparency of the films remains uncertain Additionally, incorporating maize starch into the film composition is anticipated to lead to reduced film transparency.