TECHNOLOGY AND EDUCATION MINISTRY OF EDUCATION AND TRAINING HO CHI MINH CITY UNIVERSITY OF GRADUATION THESIS S K L 0 0 9 1 3 5 Effects of TiO2 on chitosan film and its application in p
INTRODUCTION
Pose the problem
Ethylene gas, recognized as the fruit ripening hormone, significantly contributes to the postharvest deterioration of fruits and vegetables To mitigate ripening, it is essential to reduce ethylene levels One effective approach involves using active packaging that incorporates TiO2 as ethylene scavengers Due to its double bond, gaseous ethylene is a highly reactive compound that can be modified or decomposed through various methods Ethylene scavenging can be achieved via chemical or physical techniques, with photocatalytic oxidation being a notable method that utilizes ultraviolet (UV) radiation and catalysts like titanium dioxide (TiO2) Despite the limited scientific literature on the use of TiO2 screens to influence fruit ripening rates, this scarcity underscores the rationale for selecting TiO2 as an ethylene scavenger.
During the COVID-19 pandemic in Vietnam, particularly during the pre-lockdown, lockdown, and second-wave periods, daily confirmed cases significantly impacted the stock returns of publicly traded companies Agricultural exports, especially seasonal crops like Thai jackfruit and dragon fruit, faced delays, with nearly 5,000 containers awaiting customs clearance Tien Giang, known as the "Fruit Garden" of Vietnam, has over 80,000 hectares dedicated to fruit cultivation, yet many fruit prices have plummeted due to the pandemic Passion fruit, however, has shown strong growth potential, contributing to the economy and providing jobs for farmers and businesses In 2021, Vietnam produced 5.4% of the world's passion fruit, ranking 7th globally To enhance lemon consumption and reduce losses from over-ripeness, research is being conducted on using TiO₂ chitosan film to extend the ripening period of passion fruit.
This study explores how different methods of producing TiO2 influence its photocatalytic properties Specifically, it highlights the significant impact of the calcination process on the size and photocatalytic efficiency of TiO2 By mimicking the production process, we can gain a deeper understanding of synthetic TiO2 and enhance its effectiveness.
Figure 1 1 Biggest passion fruit producer in the world
Topic goal
- Determine physical properties of synthesis TiO 2
- Determine effect of TiO2 film to passion fruit ripening
- Determine properties of Chitosan films combining TiO2
Subject and scope of research
- Passion fruit is treated by Chitosan films combining TiO2
- The study determines synthesis of TiO2 production
- The study determines physical properties of chitosan film combining with TiO 2
- The study determines the application and effect of TiO 2 – chitosan film (color, harness, weight loss, gas release)
- The study is done at food technology industry laboratory, University of Technology and Education, Ho Chi Minh city
Research content
- Effect of TiO2 to chitosan film including:
+ UV-vis absorption spectrum and light transmittance
- Application of TiO2 to fruit
The scientific and practical significance of the topic
The study result shows experimental synthesis TiO 2 production
The study result shows experiment of combing TiO 2 to chitosan film which can be use as reference
The study shows the effect of TiO2-chitosan film to passion fruit
The study shows statistic of properties TiO2-chitosan film
The study shows the application potential of using chitosan film covering passion fruit
OVERVIEW
Titanium Dioxide
Titanium dioxide (TiO2), also known as titania, is an inorganic compound that was discovered in the late eighteenth century and mass-produced in the early twentieth century due to its numerous benefits It is widely utilized across various industries, including paints, food, energy, adhesives, paper, plastics, rubber, printing inks, textiles, ceramics, and cosmetics The FDA permits the use of TiO2 as a food color additive, highlighting its significance in the food industry Additionally, titanium dioxide is a key ingredient in sunscreen products, as it effectively blocks ultraviolet light absorption, helping to prevent sunburn and reduce the risk of skin cancer.
Figure 2 1: Titanium dioxide powder 2.1.2 TiO 2 application
In 1916, titanium dioxide emerged as the most widely used white pigment due to its exceptional brightness and high refractive index, second only to a few materials The ideal crystal size for titanium dioxide is approximately 220 nm, which maximizes visible light reflection However, the rutile phase of titanium dioxide can lead to aberrant grain development, causing deviations in crystal size that affect its physical properties Purity plays a crucial role in determining the optical characteristics of the pigment, as even trace amounts of certain metals can disrupt the crystal lattice and impact quality Annually, around 4.6 million tons of pigmentary titanium dioxide are consumed globally, with usage expected to rise In powder form, it serves as a powerful opacifier and is widely used in paints, coatings, plastics, papers, inks, foods, dietary supplements, medications, and toothpaste, where it contributes to whiteness and opacity In 2019, it was found in two-thirds of toothpaste tubes in France and is commonly included in various food colorings In the painting industry, titanium dioxide is often referred to as "brilliant white" or "the perfect white," with optimal particle sizing enhancing its opacity.
Figure 2 3: Marshmallow which have TiO 2 as pigment 2.1.2.2 Thin films
The optical properties of titanium dioxide films, especially their birefringence, are extensively researched Titanium dioxide thin films are produced using serial bideposition and electron-beam evaporation on fused silica substrates, which involves rapid substrate rotation and oblique-angle physical vapor deposition to create nanostructured optical coatings with high birefringence A novel method for fabricating gold-loaded TiO2 thin films (Au/TiO2) has been introduced, enabling their use as recyclable surface-enhanced Raman scattering (SERS) substrates and multifunctional photocatalysts By depositing gold nanoparticles onto a dip-coated macroporous TiO2 thin film, SERS activity is achieved The high photocatalytic activity of TiO2 allows the substrate to decompose adsorbates into small inorganic molecules under UV light, facilitating self-cleaning for subsequent SERS detection cycles Experimental results indicate that Au/TiO2 is a promising candidate for SERS substrates and photocatalysts, demonstrating excellent recyclability in detecting organic contaminants.
Figure 2 4: Application of TiO 2 in thin film which use in energy film
2.1.2.3 Sunscreen and UV blocking pigments
Titanium dioxide (TiO2) serves multiple roles in cosmetic and skin care products, acting as a pigment, sunscreen, and thickener Notably, ultrafine TiO2, when combined with ultrafine zinc oxide, creates an effective sunscreen that helps minimize the risk of sunburn, early photoaging, photocarcinogenesis, and immunosuppression from excessive sun exposure Additionally, to enhance protection against visible light, these UV blockers are sometimes supplemented with iron oxide pigments.
The majority of physical sunscreens contain nanosized titanium dioxide because of its potent UV light absorption properties and resistance to discoloration when exposed to ultraviolet radiation
Titanium dioxide particles, typically ranging from 20 to 40 nm in size, enhance the stability and UV protection of sunscreen formulations These nanoscale particles scatter visible light less effectively than traditional titanium dioxide pigments, making them ideal for use in sunscreen lotions Additionally, titanium dioxide and zinc oxide are commonly used mineral UV blockers in sunscreens designed for babies and individuals with sensitive skin, as they are considered to be less irritating than other UV-absorbing ingredients.
Nano-sized titanium dioxide (nano-TiO2) is commonly used in sunscreens and cosmetic products to effectively block UV-A and UV-B rays, offering a safer and more environmentally friendly alternative to organic UV-absorbers The risk assessment for titanium dioxide nanomaterials in sunscreens is evolving due to the distinct properties of nano-sized TiO2 compared to its micronized counterpart Rutile, a form of titanium dioxide, is preferred in these products due to its superior UV absorption and established safety profile for skin application A 2016 study by the Scientific Committee on Consumer Safety (SCCS) concluded that nano titanium dioxide, composed of 95% to 100% rutile and 5% anatase, does not pose any significant risk of adverse effects when applied to healthy skin.
[14], unless the application method would result in a significant risk of adverse effects
Figure 2 5: Sunscreen product 2.1.2.4 TiO 2 photocatalysis
Photocatalysis has gained significant attention in recent years due to its diverse applications in environmental and energy-related products This technology is utilized in various sectors, including self-cleaning surfaces and systems for air and water purification.
TiO2 photocatalysis plays a crucial role in sterilization, hydrogen evolution, and photoelectrochemical conversion To enhance photocatalytic performance and explore new applications, the development of novel materials is essential The photocatalytic oxidation of gaseous ethylene involves ultraviolet (UV) radiation and a catalyst like titanium dioxide (TiO2) When exposed to UV light, the catalyst generates reactive oxygen species (ROS) that oxidize ethylene into carbon dioxide and water.
Figure 2 6: Mechanical of TiO 2 photocatalysis 2.1.2.5 Health and safety
Titanium dioxide, once deemed "totally harmless" and "completely nontoxic," faced a significant shift in perception when the European Union revoked its authorization for use in foods (E 171) on February 7, 2022, allowing a six-month grace period Inhalation of titanium dioxide dust poses risks, potentially irritating the nose and throat, while contact with eyes or skin can lead to irritation, including tearing, blinking, and minor transient pain.
Titanium dioxide has been linked to lung cancer and is classified as a Group 2B carcinogen by the International Agency for Research on Cancer (IARC), indicating it is possibly carcinogenic to humans The biological processes leading to lung cancer, such as particle deposition, reduced lung clearance, cell damage, fibrosis, mutations, and ultimately cancer, have been observed in both rats and individuals exposed to dust in occupational settings.
The International Agency for Research on Cancer (IARC) has highlighted the relevance of animal cancer findings to workers in industries exposed to titanium dioxide dust, particularly in situations with inadequate dust control during processes like packaging and maintenance While the study did not establish a direct link between occupational exposure to titanium dioxide and an increased risk of lung cancer, potential misclassification of exposure and low prevalence may have contributed to false negative results Current human research does not support a connection between titanium dioxide exposure and elevated cancer risk However, concerns arise regarding high levels of nano-particle-sized titanium dioxide, which may penetrate the body and reach internal organs, potentially leading to cancer.
Research indicates that exposure to titanium dioxide (TiO2) nanoparticles can lead to inflammatory reactions and genetic damage in mice, raising concerns about potential cancer risks and genetic disorders, particularly for individuals with occupational exposure The study emphasizes the need to limit ingestion of TiO2 through non-essential additives and food colors While TiO2 is associated with cancer risk, the exact mechanisms remain unclear; however, molecular studies suggest that cytotoxicity arises from interactions with the lysosomal compartment rather than recognized apoptotic pathways In response to these findings, the US National Institute for Occupational Safety and Health (NIOSH) has established exposure limits for fine and ultrafine TiO2 particles at 2.4 mg/m³ and 0.3 mg/m³, respectively, for time-weighted average concentrations.
Research indicates that smaller titanium dioxide particles may pose a greater carcinogenic risk compared to larger ones There is some evidence linking titanium to the rare yellow nail syndrome, potentially from medical implants or dietary sources However, Andrew Maynard, director of the Risk Science Center at the University of Michigan, has minimized the risks associated with titanium dioxide in food, stating that the material used by Dunkin' Brands and other producers is not new or classified as a nanomaterial Most food-grade titanium dioxide particles are significantly larger than the nanoparticle threshold of 100 nanometers.
Chitosan
Chitosan is a linear polysaccharide made up of D-glucosamine and N-acetyl-D-glucosamine linked at the β-(1-4) position, characterized by its biodegradability, biocompatibility, and nontoxicity Its high biodegradation properties make it valuable in the biomedical field Chitosan exhibits various physical properties, including high viscosity and the ability to complex and chelate, while being insoluble in water and organic solvents, yet soluble in aqueous acidic solutions like acetic acid This unique natural polysaccharide, derived from the deacetylation of chitin, is abundant in nature, with an annual synthesis of about 10 billion tons, making it the second most available biopolymer after cellulose, found in crab and shrimp shells, fungi, and insects The preparation of chitosan involves four key steps: demineralization, deproteinization, decoloration, and deacetylation.
Isopropyl alcohol
Isopropyl alcohol is a colorless, flammable chemical compound (chemical formula CH3CHOHCH3) with a strong alcoholic odor.[30]
In the Meerwein-Ponndorf-Verley reduction and other transfer hydrogenation processes,
Figure 2 8: chemical composition of isopropyl alcohol
Isopropyl alcohol serves as a versatile solvent and hydride source When heated with sulfuric acid, it can be dehydrated to yield propene or converted to 2-bromopropane using phosphorus tribromide Additionally, isopropyl alcohol can be transformed into acetone, a corresponding ketone, through dehydrogenation over a hot copper catalyst or by employing oxidizing agents such as chromic acid.
Isopropyl alcohol effectively dissolves numerous non-polar substances and evaporates quickly, making it a preferred cleaning solution Unlike many common solvents, it typically leaves no oil residues and is largely non-toxic Its rapid evaporation and lower risk of corrosion compared to water make it ideal for cleaning oil-based residues.
Isopropyl alcohol, part of the alcohol solvent family alongside ethanol, n-butanol, and methanol, is commonly used for cleaning various items It effectively cleans eyeglasses, electrical contacts, audio and video tape heads, DVD and optical disc lenses, as well as removing thermal paste from heatsinks on CPUs and other integrated circuit packages.
Isopropyl acetate, a solvent formed from the esterification of isopropyl alcohol, can be converted into sodium isopropylxanthate, which serves as a herbicide and reagent for ore flotation when reacted with sodium hydroxide and carbon disulfide Additionally, isopropyl alcohol reacts with titanium tetrachloride and aluminum metal to yield titanium and aluminum isopropoxides, respectively, with the former acting as a catalyst and the latter as a chemical reagent Furthermore, isopropyl alcohol can function independently as a chemical reagent by serving as a dihydrogen donor in transfer hydrogenation.
Passion fruit
Passion fruit (Passiflora edulis) is a visually appealing and nutrient-dense fruit, highly sought after for its diverse uses in products like juice, jelly, and ice cream This perennial woody vine, native to tropical America (specifically Brazil), belongs to the Passifloraceae family The fruit is typically round or oval, featuring a smooth, waxy peel with subtle white spots, available in purple or yellow varieties The interior consists of aromatic membranous sacs filled with orange pulp There are two main varieties: the purple passion fruit (Passiflora edulis Sims) and the yellow passion fruit (Passiflora f flavicarpa Deg.), with the yellow variety being a mutation of the purple type or a natural hybrid with a closely related species.
Passion fruit trees can thrive in any region of the United States, but to achieve a high yield and abundant fruit production, specific ecological conditions must be met.
Purple passion fruit thrives in subtropical climates with an average altitude between 1,000 and 2,000 meters above sea level Consequently, purple passion fruit trees are frequently cultivated in the Central Highlands
Passion fruit thrives in well-drained, light-textured soil that is flat, warm, and moist The ideal soil should have a cultivable layer exceeding 50 cm in thickness, a humus content greater than 2 percent, and a pH level between 5.5 and 6.
The optimal temperature for passion fruit trees ranges between 20 and 25 degrees Celsius In northern highland provinces, where hoarfrost occurs, the cold conditions are detrimental to the growth of these trees, making cultivation nearly impossible Additionally, temperatures below 10 degrees Fahrenheit can be fatal for the plants.
Light: The plant prefers bright light
A consistent annual rainfall of 1,600 mm is essential for optimal growth During the fruiting stage, additional watering is crucial; otherwise, insufficient moisture can lead to underdeveloped, tough, and unattractive fruit that may ultimately drop prematurely.
Figure 2 9: passion fruit 2.4.2 Nutrition value of passion fruit
Passion fruit provides many vitamins, minerals, and fibers and is not fiber calories
Table 2 1: Nutritional composition of passion fruit per 100g
During the ripening process, fruits release higher levels of ethylene gas as a result of increased respiration A small concentration of ethylene promotes ripening in environments with controlled temperature and humidity, particularly near consumption areas Ethylene is the first identified plant hormone that plays a crucial role in regulating various processes related to plant growth, development, and responses to biotic factors.
15 abiotic stresses Ethylene is best known for its effect on fruit ripening and organ abscission, and thus has great commercial importance in agriculture[36]
Ethylene is a volatile chemical that plays a crucial role in the ripening of fruit, consisting of 2 carbon and 4 hydrogen atoms While it positively influences fruits by enhancing their color and metabolic activity, it also has negative effects on post-harvest storage The acceleration of ripening caused by ethylene can lead to a decrease in fruit quality and an increased vulnerability to diseases.
Figure 2 10: Ethylene effect to fruit ripening
Fruit ripening involves a series of changes that affect its color, weight, and composition, with qualities evolving through various growth stages For climacteric fruits like passion fruit, the process is driven by ethylene, leading to softening that impacts postharvest quality and storage As fruits ripen, they become more appealing, often turning sweeter, softer, and less green, despite an initial increase in acidity Additionally, the release of aroma volatiles enhances the fruit's flavor profile.
The plant hormone ethylene plays a crucial function in fruit ripening
Immature fruits contain low levels of ethylene, which increases as they mature, signaling the ripening process Post-harvest, ethylene production escalates, leading to a decrease in shelf life, storage potential, and increased susceptibility to diseases Fruits are categorized into two groups based on ethylene production: climacteric and non-climacteric.
Climacteric fruits, also referred to as autocatalytic fruits, can continue to ripen after being harvested due to their ability to produce ethylene In contrast, non-climacteric fruits do not produce ethylene and cannot ripen post-harvest The initial concentration of ethylene in climacteric fruits triggers an increase in their ethylene production, facilitating the ripening process.
Figure 2 11: Ethylene release of climacteric fruits and non-climacteric fruits
Table 2 2: Some fruits emit ethylene gas
VH = very high; H = high; M = medium; L = low; VL = very low
Effect of irradiation on the experiment
Photocatalysts are substances that accelerate chemical reactions when exposed to light, combining the concepts of photons and catalysts This process, known as photocatalysis, involves using light and semiconducting materials to initiate reactions For instance, titanium dioxide (TiO2) acts as a photocatalyst by absorbing UV light, which enhances the oxidation and decomposition of ethylene gas.
Research on fruit preservation
Some methods of preserving fruit
The primary factor influencing the metamorphosis of fruits and vegetables is respiration, which can lead to challenges in storability due to delayed respiration and nutrient consumption Storability refers to the ability of fruits and vegetables to maintain quality with minimal loss during storage To address these challenges, it is essential to regulate the respiration of the fruit, ensuring that they remain alive while simultaneously reducing their metabolism and respiration rates.
Low temperatures play a vital role in inhibiting respiration and extending the storage life of fruits The technique of low-temperature preservation is well-established and widely used, making it the most common physical storage method By lowering the temperature, the metabolic activity of fruits is reduced, which in turn limits the growth of thermophilic microorganisms and slows down oxidation, ultimately decreasing the rate of fruit degradation Therefore, careful attention to temperature is essential for effective fruit preservation.
According to TCVN 9688:2013, the recommended cold storage temperature for Apples is approximately -1 to 0 degrees Celsius (ISO 1212:1995)
Certain cultivars of the Antilles group, such as Waldin, require storage temperatures between 10 and 12.5 degrees Celsius In contrast, Fuerte avocados, a hybrid from Mexico and Guatemala, can be stored at approximately 4.5 degrees Celsius for up to three weeks without any deterioration.
For optimal storage, avocados should be kept at a temperature of 7 °C If the storage temperature drops below 5 °C, the avocados may ripen improperly, resulting in subpar quality This guideline is based on TCVN 10921:2015 (ISO 2295:1974).
Controlled atmosphere storage preserves food by maintaining an airtight environment with specific concentrations of gases such as O2, CO2, and nitrogen This method significantly reduces the physiological metabolism of fruits and vegetables, allowing for minimal nutrient degradation Additionally, the strong antibacterial properties of this storage technique facilitate extended shelf life.
Several methods of degassing ethylene
- KMnO4 is the most frequently employed commercially available substance for controlling the activity and quantity of ethylene gas Nevertheless, due to the toxicity of KMnO4
Ingestion of potassium permanganate (KMnO4) can lead to severe health issues, including abdominal pain, bloody vomiting, dark brown fasciitis, mouth ulcers, and stomach perforation It may also cause septic shock, hepatitis, and urethritis, with necrosis occurring upon direct contact, making KMnO4 unsuitable for food use Ozone (O3) serves as an alternative oxidant; however, it is unstable and quickly decomposes into oxygen (O2).
Carbon-based ethylene adsorbents are crucial for controlling ethylene levels This approach does not eliminate ethylene; rather, it transforms it into a different gas, requiring an extra step for effective gas management.
Reasons for choosing a research topic
The rise in agricultural production has led to an urgent need for effective preservation methods to ensure consumer access to fresh products In Vietnam, signs promoting the sale of fruits like dragon fruit and watermelon highlight the issue, as these fruits are often sold at prices significantly lower than market value, resulting in financial losses for farmers and hindering economic growth The ripening of climacteric fruits, such as passion fruit, is influenced by ethylene, which affects their postharvest quality and storability A promising solution involves using TiO2 to treat the ethylene gas released during the ripening process of these fruits.
[37] to increase the shelf life of the fruit
Figure 2 16: current situation of VN agriculture
MATERIAL AND METHODS
Materials and methods
This study utilized two types of titanium dioxide: industrial-grade titanium dioxide sourced from a leading online supplier in Vietnam and synthesized titanium dioxide for research purposes Additionally, chitosan powder, acetic acid, glycerol, and other chemicals were procured from a local chemical supplier in Vietnam.
- UV-Vis Halo Vis 20 Spectrophotometer (Dynamica, Switzerland)
- 2- and 4-digit analytical balance (Sartorius, Germany)
- Necessary tools such as beaker, pipette, micropipette, volumetric flask, petri disk,
Determine the amount of gas released
Making coating on passion fruit
Determine the physical properties of films
Figure 3 1: research process diagram 3.3 Method
Titanium dioxide nanoparticles are synthesized using the sol-gel method, involving two distinct solutions The first solution comprises 147 mL of isopropyl alcohol and 50 grams of titanium butoxide in a 500 mL beaker, which is sealed and stirred for 30 minutes to stabilize The second solution consists of 200 mL of water and 12.5 mL of 0.25M HCl This second solution is then added to the first, and the mixture is stirred for 6 hours at room temperature (25°C) After stirring, the mixture is poured into petri dishes, with each dish containing 50 g of the solution, and dried at 150°C for 12 hours Once fully dried, the material is ground into powder and fired at 800°C for 3 hours, resulting in synthetic TiO2 in a white powder form.
3.3.2 Preparation of chitosan films coated with TiO2 to cover the fruit
This research utilizes two distinct types of titanium dioxide: the first is industrial TiO2 sourced from America, purchased from Shoppe, a leading online store in Vietnam The second type is synthesized in the laboratory following the procedure detailed in the course article[44].
Chitosan (CH) films were first prepared by blending the mixture of chitosan powder (4 % m/v) and acetic acid (1 % v/v) on a magnetic stirrer until complete dissolution before adding 30
The addition of glycerol is crucial for achieving the desired plasticity in chitosan films used for storing passion fruit; without it, the film is prone to breaking In section 2.1, titanium dioxide was prepared at varying concentrations of 0%, 20%, 30%, and 40% to identify the minimum effective concentration The chitosan film, enhanced with titanium dioxide, was then applied to passion fruit for preservation studies, with each sample tested three times to ensure accuracy Detailed information about the film mixture can be found in Table 2.3.
Table 3 1: Preparation of chitosan films coated with TiO2 modulated
Sample Total sample solution (g) Chitosan(g)
Table 3 2: Preparation of chitosan films coated with commercial TiO2
Sample Total sample solution (g) Chitosan(g)
3.3.3 Preparation of chitosan films coated with TiO2 on petri dish
This research utilizes two distinct types of titanium dioxide The first type is industrial TiO2 sourced from America, purchased from Shoppe, a leading online store in Vietnam The second type is synthesized in the laboratory following the procedure detailed in the course article[44].
Chitosan (CH) films were first prepared by blending the mixture of chitosan powder (2 % m/v) and acetic acid (1 % v/v) on a magnetic stirrer until complete dissolution before adding 30
The addition of glycerol is crucial for maintaining the plasticity of Chitosan films when storing passion fruit; without it, the films are prone to breaking In the experiment, a consistent amount of 0.4 g of solids was poured onto plates, and samples containing equal amounts of Chitosan, acetic acid, and glycerol were utilized to investigate the impact of varying TiO2 concentrations on the Chitosan film.
3.3.3.1 Experimental arrangement to determine the effects of TiO2 on chitosan films
Different concentrations of commercial and homemade TiO2 were applied to petri dishes at a rate of 0.4 g solids per plate The liquid was dried in an oven at 45 degrees Celsius for 24 hours to remove moisture, leaving only the particles for film peeling The resulting film was stored in an airtight container with saturated brine to maintain humidity, which is crucial for film quality After stabilization, we evaluated the film's loss on drying, tensile strength (TS), elongation at break (E), water vapor permeability (WVP), water drop penetration time per film thickness (WDPT/d), and transparency of the blended films.
3.3.3.2 Method to determine the moisture content of chitosan films
The experiment on measuring film moisture was conducted as follows: a sample of film was cut and precisely weighed before being dried in a drying chamber at 105 degrees Celsius for
After being chilled in a desiccator with silica gel, the chitosan film was weighed to determine its mass loss This mass loss reflects the amount of water vapor released, indicating the film's moisture content.
The formula used when calculating the percentage of moisture content of chitosan films is:
3.3.3.3 Some mechanical properties of chitosan films
A texture analyzer was utilized to assess the tensile strength (TE) and elongation (EL) characteristics of the film The tensile strength is measured by the maximum load at the point of rupture, while the percentage of elongation is calculated by comparing the film's length at break to its original length before testing.
The expansion and solubility of chitosan film are evaluated by first drying the sample to a consistent weight and then soaking it in water for 12 hours After soaking, the sample is re-weighed following the removal of surface water, with excess moisture blotted away using paper towels The increase in weight is attributed to the water absorbed by the membrane Subsequently, the sample undergoes a second drying process until a constant weight is achieved, with the mass loss indicating the film's solubility.
Formula for calculating water absorption rate:
Formula for calculating film solubility:
3.3.3.4 The absorption spectrum and light transmittance
The transparency of the film was assessed by measuring the percentage of transmitted light with a UV-Vis spectrophotometer (UH-3500 Hitachi) Colorimetric films, cut into rectangles measuring 1.2 × 4 cm, were positioned in the cuvette slot perpendicular to the light beam Air served as the reference for the measurements, and the spectrum of each film was recorded across wavelengths ranging from 200 to 1100 nm.
3.3.3.5 The Water Vapor Permeability (WVP)
The moisture permeability of a membrane is influenced by the pressure differential between its exterior and interior In this study, the membrane is used to seal the cap of a glass vial, secured with paraffin, while the interior remains unfilled with silica gel to create a pressure difference A relief air gap of less than 1 mm is maintained below the film The cells are stored in hermetically sealed 500 mL chambers with a saturated sodium chloride solution at 25°C to achieve a 75% relative humidity difference After reaching steady-state conditions in 2 hours, the cell mass was measured hourly over a period of 0.5 days.
The Water Vapor Permeability (WVP) is determined using the formula where \( d \) represents the film average thickness in millimeters, \( m \) is the permeation rate in grams per hour derived from the linear regression of mass gain over time, \( A \) is the permeation area of \( 5.3106 \times 10^{-3} \) square meters, \( \Delta RH \) indicates the difference in relative humidity at 0.75, and \( P_w \) denotes the partial water vapor pressure at the test temperature of 3.167 kPa.
When selecting passion fruit, choose unripe fruits with smooth, glossy skin that is free of wrinkles and damage After careful sorting, the fruits are cleaned with water and a 20% salt solution They are then categorized into three groups: those wrapped in titanium dioxide film, those wrapped in chitosan film, and a control group of normal passion fruit Each group is placed separately for hardness measurement using a specialized machine Daily, the titanium dioxide-wrapped fruits are treated with ultraviolet (UV) light from a 5W lamp, positioned 10-15 cm away, for 180 minutes The quality of the passion fruit is evaluated every two days, with three iterations conducted for each treatment group.
The hardness of passion fruit is assessed using the Rockwell hardness test, which involves applying stresses with a tungsten carbide ball or a spheroconical diamond indenter Proper preparation of the testing and sitting surfaces is crucial, as inadequate preparation can lead to test failures or inaccurate readings After preparing the surface, a mild load of 3 or 5 kgf is applied to calibrate the testing apparatus, followed by a heavier load ranging from 15 kgf to 150 kgf, depending on the material's strength The depth of the indenter's penetration during the test is measured to calculate the hardness.
3.3.5 Passion fruit weight loss experiment
RESULT AND DISCUSSION
Synthesis of TiO2
Several methods for producing nano-sized TiO2 particles or TiO2 films have been developed
The sol-gel process, first introduced by Geffcken and Berger in 1939, has gained significant attention due to its simplicity, low reaction temperatures, and high product purity This widely used technique for producing TiO2 involves the reaction of precursors, such as titanium alkoxide, with water, typically in alcoholic solutions, and the addition of catalysts like hydrochloric acid to regulate the reaction.
Titanium dioxide nanoparticles are synthesized using the sol-gel method, which involves two distinct solutions The first solution is prepared by mixing 147 mL of isopropyl alcohol with 50 grams of titanium butoxide in a 500 mL beaker, followed by sealing and stirring for 30 minutes to stabilize the mixture The second solution consists of 200 mL of water and 12.5 mL of 0.25M HCl This second solution is then added to the first solution, and the combined mixture is stirred for 6 hours at room temperature (25 °C) Finally, the resulting solution is poured into petri dishes, with each dish containing 50 g of the mixture, and then dried in a dryer.
The process involves drying materials at 150 °C for 12 hours, followed by grinding the dried pieces into powder This powder is then fired at 800 °C for 3 hours, resulting in synthetic TiO2, which is obtained in a white powder form.
In this experiment, another type of TiO2 was used, the commercial TiO2 used to compare the efficiency in preserving passion fruit and affecting the film properties.
Effect of TiO2 on properties of chitosan films
Using two types of TiO2, synthetic TiO2 and commercial TiO2, to determine the influence of TiO2 on the properties of chitosan films
S20: Chitosan combine with synthetic TiO2 at 20%
S30: Chitosan combine with synthetic TiO2 at 30%
S40: Chitosan combine with synthetic TiO2 at 40%
C20: Chitosan combine with comercial TiO2 at 20%
C30: Chitosan combine with comercial TiO2 at 30%
C40: Chitosan combine with comercial TiO2 at 40%
Figure 4 1: Compare the moisture content of TiO 2 chitosan films Table 4 1: The moisture content of chitosan films and chitosan combine with TiO2
Moisture plays a crucial role in the effectiveness of packaging films, as it influences their ability to absorb moisture from moderately humid environments For food packaging films, it is essential to reliably maintain this property to protect perishable goods Accurately determining the moisture content of the film is vital for its application in food preservation To overcome the brittle and moisture-sensitive characteristics of individual cellulose hydrogels (CH), advancements in polymer production are necessary.
36 composites based on CH/IPA (Isopropyl alcohol) , such as films, is an appropriate solution for improving the quality of food packaging [47]
According to [48], the addition of TiO2 improves the water vapor barrier of the film
In this experiment, increasing the concentration of synthetic TiO2 in the chitosan film kept the moisture content constant In contrast, the moisture content of the film with commercial TiO2 rose as the TiO2 concentration increased This difference may be attributed to the presence of hydrophilic impurities in commercial TiO2, which contribute to higher moisture levels with increased concentration.
Chitosan films exhibited a higher moisture content compared to those supplemented with TiO2, with films containing commercial TiO2 showing greater moisture levels than those with synthetic TiO2 This indicates that the incorporation of TiO2 effectively reduces the moisture content of the chitosan films.
4.2.2 Effect of TiO2 on the swelling degree of the chitosan film
Figure 4 2: Swelling degree of TiO 2 – chitosan films
Table 4 2: Swelling degree of the chitosan film and chitosan films combine with TiO2
Increasing the amount of TiO2 does not affect the swelling of either synthetic or commercial TiO2 samples Generally, commercial TiO2 exhibits less swelling compared to synthetic TiO2, likely because its smaller particle size allows for easier dispersion within the polymer matrix of the chitosan film.
The pure chitosan film exhibits greater swelling compared to the chitosan film blended with TiO2, as the presence of TiO2 molecules restricts water absorption into the polymer's molecular structure, leading to a less swollen film.
4.2.3 Effect of TiO2 on the solubility of the chitosan film
Figure 4 3; Effect of TiO2 on the solubility of the chitosan film Table 4 3: Solubility of the chitosan film and chitosan films combine with TiO2
The graph indicates that synthetic TiO2 exhibits optimal solubility at 40% concentration, whereas commercial TiO2 reaches its peak solubility at 30% Additionally, commercial TiO2 demonstrates lower solubility compared to synthetic TiO2, likely due to the superior dispersion of commercial TiO2 molecules in water.
The pure chitosan film was most soluble in about 9.21%, the addition of hydrophilic TiO2 molecules increased the water resistance as well as the solubility of the film
4.2.4 .Effect of TiO2 on the Moisture permeability of the chitosan film
Figure 4 4: Effect of TiO2 on the moisture permeability of the film in 12 th hour
Table 4 4: Moisture permeability of the film in 15 th hour
Water Vapor Permeability (WVP) is crucial for determining the shelf life of packaged foods, as it directly affects moisture protection and food stability High water content can lead to spoilage or mold growth during storage In experiments, membranes with TiO2 demonstrated lower WVP compared to those made solely from Chitosan, with the Chitosan membrane achieving the best permeability at 15.09 percent As the TiO2 concentration increased from 20 percent to 40 percent, the moisture permeability of Chitosan membranes enhanced with synthetic TiO2 was recorded at 14.91 percent, 14.58 percent, and 14.68 percent, respectively For commercial TiO2, the moisture permeability values were 14.81 percent, 14.57 percent, and 14.83 percent at the same concentrations Both synthetic and commercial TiO2 effectively enhance moisture resistance at a concentration of 30%, as TiO2 hydrophilic molecules disrupt the molecular structure of polymeric films, preventing water permeation.
4.2.5 UV-vis Absorption spectrum and light transmittance of the film
To protect food from the effects of UV light, it is essential to prevent light from reaching it, making light transmission a key factor in evaluating the UV light blocking effectiveness of films The spectrum of various film types is illustrated in the figure below.
Figure 4 5: Light transmittance of chitosan and chitosan films incorporating TiO2
In comparison to films containing solely Chitosan, the addition of TiO2 significantly increases light reflection This is due to the fact that TiO2 absorbs UV-vis rays [51]
The light transmittance of films containing TiO2 decreases with increasing TiO2 concentration, showing no significant difference between 30% and 40% concentrations Commercial TiO2 is highly effective, blocking nearly all UV-vis radiation across most wavelengths Previous research indicates that chitosan films combined with TiO2 achieve effective contrast The impact of increasing synthetic TiO2 from 30% to 40% is minimal, and the efficiency of commercial TiO2 remains nearly the same across concentrations of 20%, 30%, and 40%.
4.2.6 FTIR of synthetic TiO2 and commercial TIO2
Wavelength (nm) Chitosan Syn TiO2 20% Syn TiO2 30% Syn TiO2 40%
CM TiO2 20% CM TiO2 30% CM TiO2 40%
Figure 4 6: FTIR spectra of TIO2
The FTIR spectrum analysis of TiO2 was conducted to verify the molecular interactions between titanium and oxygen The illustration below compares the FTIR spectra of synthesized TiO2 with that of commercial TiO2.
TiO2 exhibits a spectral range of 500 cm⁻¹ to 850 cm⁻¹, indicating the presence of titanium-oxygen bonds In synthetic TiO2, vibrations between 490 cm⁻¹ and 500 cm⁻¹ are clearly detectable, demonstrating successful modulation at the laboratory scale In contrast, commercial TiO2 presents challenges in observing these linkages, but this does not indicate the absence of TiO2.
4.2.7 Mechanical Properties of TiO 2 and commercial TiO 2 with chitosan film
Figure 4 7 Tensile strength of synthetic TiO 2 and commercial TiO 2 with chitosan film chitosan
Figure 4 8: Elongation of synthetic TiO 2 and commercial TiO 2 with chitosan film Table 4 5: Elongation of synthetic TiO 2 and commercial TiO 2 with chitosan film
The mechanical properties of chitosan films, specifically tensile strength (TS) and percentage elongation at break (E), reveal significant variations based on TiO2 content Chitosan film exhibits the lowest tensile strength, while the addition of TiO2 markedly enhances this property Notably, the chitosan film with 30% TiO2 achieves the highest tensile strength at 86.601 Pa, surpassing films with 20% (41.254 Pa) and 40% (60.477 Pa) TiO2 Conversely, samples containing commercial TiO2 show a decrease in tensile strength with increasing TiO2 percentages, with the 20% commercial TiO2 sample demonstrating the highest strength at approximately 48% Unlike synthetic TiO2, the tensile strength of commercial TiO2 samples remains relatively consistent despite variations in TiO2 content.
Elongation data closely resembles tensile strength data, with chitosan film containing 30% synthetic TiO2 exhibiting the highest elongation among the samples Interestingly, chitosan samples do not have the lowest elongation; that distinction belongs to STiO2 (20%), which measures just 2% Overall, the results indicate no significant difference in elongation between chitosan, synthetic TiO2, and commercial TiO2.
4.2.8 Thickness of TiO 2 -chitosan film
Figure 4 9: Thickness of chitosan film with synthetic TiO 2 and commercial TiO 2
Table 4 6: Thickness of chitosan film with synthetic TiO 2 and commercial TiO 2
Figure 4.9 indicates that the C40 sample exhibits the greatest thickness, comparable to that of pure chitosan film In contrast, C20 and C30 samples show no significant difference between them This suggests that the thickness increases with the addition of 40% concentration of commercial TiO2 Conversely, the S20, S30, and S40 samples demonstrate a decreasing trend in thickness as the concentration of synthetic TiO2 in the chitosan film increases.
Application of TiO2- Chitosan films on passion fruit preservation
Using two types of TiO2 are synthetic TiO2 and commercial TiO2 for application in the preservation of passion fruit
S20: Chitosan combine with synthetic TiO2 at 20%
S30: Chitosan combine with synthetic TiO2 at 30%
S40: Chitosan combine with synthetic TiO2 at 40%
C20: Chitosan combine with comercial TiO2 at 20%
C30: Chitosan combine with comercial TiO2 at 30%
C40: Chitosan combine with comercial TiO2 at 40%
For purpose of data analysis and data interoretation, it is important to have uniform representation of hue derived from L, a, b space Using standard calculation for hue (arc tan(b/a))
If color located in quadrant I (+a, +b):
If color located in quadrant I (-a, +b):
If color located in quadrant I (-a, -b):
If color located in quadrant I (+a, -b):
4.3.1.1 Sample with UV and sample without UV
Figure 4 11: L of samples with and without UV
Time (days) control samples chitosan film Synthetic TiO2 (with UV) Synthetic TiO2 (no UV)
Figure 4 12: The hue angles of samples with and without UV
As passion fruit ripens, its color undergoes a noticeable change, which can be accurately measured using a portable digital color analyzer that provides L, a, and b statistics This analysis, conducted over four days, investigates the impact of TiO2 photolysis and highlights the influence of UV light on the fruit Additionally, the observed color change is linked to variations in other important characteristics of the passion fruit.
The analysis of figure 4.11 reveals that both chitosan film samples and control samples experience a slight decrease in lightness after two days, followed by a gradual increase on day four Notably, samples with TiO2 film show an increase in lightness on day two, particularly those without UV exposure, which later exhibit a downward trend In contrast, TiO2 film samples exposed to UV light continue to increase in lightness by day four, suggesting that UV exposure may enhance the lightness of passion fruit Figure 4.12 indicates that only the hue angles of chitosan film samples decrease slowly over four days, resulting in a redder appearance of the passion fruit By the end of the observation period, both the passion fruit sample with TiO2 and the control sample display a more yellow hue, with the synthetic TiO2 (without UV) sample showing the most significant color change and the highest level of yellowing.
4.3.1.2 Cold temperature (5 o C) and room temperature (25 o C) samples
Time (days) control samples chitosan film Synthetic TiO2 (with UV) Synthetic TiO2 (no UV)
Figure 4 13:L of TiO2-chitosan film under cold temperature and room temperature
Time (days) controlled samples (cold temperature) chitosan (cold temperature) sythetic TiO2 film (cold temperature) commercial TiO2 (cold temperature) controlled samples
Figure 4 14 The hue angles color of samples under cold temperature and room temperature
The study utilized a portable color analyzer to assess the impact of TiO2 photolysis over four days, focusing on the effects of UV light under cold and room temperature conditions Results indicated that the lightness of commercial TiO2 significantly increased on day 2 but dropped sharply to 41 by day 4, while synthetic TiO2 consistently decreased from 52 to 41 Both controlled samples at room and cold temperatures exhibited similar lightness trends, showing no significant changes over the four days However, the hue angle of cold temperature samples shifted towards red, contrasting with the room temperature samples The hue angles of synthetic TiO2 decreased from 35 to 30, indicating a redder tone, while commercial samples displayed drastic changes, with hue angles dropping from 44 to 32 before rising to 45, reflecting a transition from red to yellow due to the inherent white color of commercial TiO2.
Table 4 7: Formula of calculating weight loss percent
4.3.2.1 Samples with different amount of TiO2
Table 4 8: Weigh loss of samples with different amount percentage of TiO 2 in chitosan solution
20% TiO2 (g) 30% TiO2 (g) 40% TiO2 (g) Control sample (g)
Figure 4 15: Weigh loss of samples with different amount percentage of TiO 2 in chitosan solution
The study investigates the impact of varying percentages of TiO2, based on 2% chitosan, over a period of 6 days on weight loss, a key factor in the ripening of passion fruit The objective is to identify the most effective TiO2 concentration to enhance the storage longevity of passion fruit.
The controlled samples exhibited the highest weight loss of 40% after six days, while on day two, the 20% TiO2 passion fruits showed increased weight loss starting from day four, likely due to their younger age, higher metabolic rate, and softer rind tissue Conversely, the samples with 20% TiO2 experienced the least weight loss at only 5% By day six, the weight loss for both 20% and 40% TiO2 samples was similar at 37% Notably, the 30% TiO2 samples had the highest weight loss on day two, indicating that TiO2 concentrations influence the ripening process of passion fruit.
0 1 2 3 4 5 6 7 w eigl h t los s time (days) 20% TiO2 30 % TiO2 40% TiO2 controlled sample
52 significant difference in weight loss between samples with TiO2 and controlled samples It needs more repeated tests and samples to conclude the effect of a different percentage of TiO2
4.3.2.2 Samples with UV under cold temperature and room temperature
Figure 4 16: Weight loss between samples with TiO 2 in chitosan solution under cold temperature (5 o C) and control sample of room temperature after 4 days
The study investigates the impact of TiO₂ on passion fruit under cold temperatures, comparing treated and untreated samples Results indicate that control samples exhibited the highest weight loss, with a linear increase in weight loss percentage correlating with storage duration and temperature Notably, after four days at 25°C, the weight loss reached approximately 20% These findings align with Pruthi (1963), who noted that weight loss in purple passion fruit escalates with higher temperatures and extended storage Samples treated with TiO₂ under cold conditions demonstrated the lowest weight loss due to enhanced photolysis, while untreated samples and those with only chitosan experienced greater losses of 10.3% and 8.3%, respectively Thus, TiO₂ significantly benefits passion fruit preservation in cold storage.
4.3.2.3 Samples with UV and without UV
Time (days) control sample (room temperature) controlled sample (cold temperature) chitosan film
30% synthetic TiO2 samples (cold temperature) Commercial TiO2
Figure 4 17: Line chart show weight loss of sample with and without UV treating after 6 days
The study investigates the weight loss of samples treated with TiO2 both with and without UV exposure Results indicate that UV treatment enhances the effectiveness of TiO2, which is crucial for extending the storage life of passion fruit The controlled sample and the one without UV treatment exhibited similar and significant weight loss, while the TiO2-treated sample exposed to UV light showed reduced weight loss This highlights the importance of using TiO2 in conjunction with UV light to prolong storage duration.
4.3.3 Effect of hardness on fruit ripening
The ripening of climacteric fruits like passion fruit is influenced by ethylene, leading to a softening process that affects postharvest quality and storage capability To assess the impact of chitosan-coated TiO2 film on the hardness of passion fruit, we can simultaneously measure the hardness of wrapped and unwrapped samples The initial hardness on the first day is set at 100%, and as the days progress, the hardness percentage decreases, indicating the fruit's softening.
4.3.3.1 Passion fruit's hardness without UV exposure
Time (days) control fruit STiO2 ( with UV) STiO2 ( without UV)
Table 4 9: Prediction of fruit hardness during ripening
Figure 4 18: The line graph of the hardness change of passion fruit without UV irradiation
According to the line graph, there isn't much of a difference in the hardness of samples that are
The study examined the effects of varying TiO2 concentrations in chitosan films, specifically 20%, 30%, and 40%, compared to standard samples The standard sample maintained a TiO2 content of approximately 41.32% in the 30% and 40% samples, while the TiO2 hardness of the fruit decreased significantly to about 35.77% by the end of the study Additionally, the fruit's weight loss was less pronounced with higher TiO2 ratios, although it remained greater than that of the standard sample until reaching a 40% concentration Ultimately, no significant differences were observed between the samples.
4.3.3.2 Passion fruit's hardness with UV exposure
H ar d n es s Perc en ta ge (% )
Time (day) Synthetic TiO2 20% Synthetic TiO2 30% Synthetic TiO2 40% Control sample
Figure 4 19: The line graph of the hardness change of passion fruit with UV irradiation
The line graph indicates that UV radiation exposure enhances the stiffness of modified samples, bringing it closer to that of the reference sample On the fourth day of storage, the UV-irradiated samples with 30% and 40% TiO2 achieved hardness values of 50.57% and 44.56%, respectively, compared to 41.33% for untreated samples Reducing the TiO2 concentration to 20% resulted in a hardness approximately 37.55% lower than the standard sample under UV exposure Overall, while the differences among the samples are not pronounced, the highest hardness retention for the fruit is observed at a 30% TiO2 concentration.
4.3.3.3 Compare the difference hardness when storage at different temperature and different type of TiO2
H ar d n es s Perc en ta ge (% )
Time (day) Synthetic TiO2 20% UV Synthetic TiO2 30% UV Synthetic TiO2 40% UV Control sample
Figure 4 20: Compare the difference hardness when storage with prepared TiO2 and commercial TiO2
Research indicates that UV light irradiation of fruit, combined with a 30 percent concentration of TiO2, effectively preserves firmness Consequently, all subsequent trials maintained this fixed concentration of TiO2.
In the study of standard sample storage, various formulations of TiO2 were prepared, including 30 percent TiO2 with and without UV irradiation, as well as 30 percent commercial TiO2 subjected to UV irradiation Additionally, a sample coated solely with chitosan and without TiO2 was included The hardness measurements taken on the final day of storage revealed values ranging from 45 to 47 percent, with the commercial TiO2 at 30 percent with UV irradiation demonstrating the highest hardness at approximately 53.40 percent.
H ar d n es s p erce n ta ge (% )
Control sample Synthetic TiO2 30% UV Synthetic TiO2 30%
Figure 4 21: Compare the difference hardness when storage at different temperature
At lower temperatures, the hardness of the samples showed minimal variation, likely due to the limited sample size or the lack of significant impact from cold storage compared to normal temperature conditions.
In summary, UV-irradiated TiO2 demonstrates superior effectiveness in enhancing fruit hardness compared to unirradiated TiO2, particularly at a concentration of 30 percent However, it is important to note that cold storage does not influence fruit hardness.
The results showed that the tomato fruit treated with TiO2 had a different hardness with the control sample, Tomato fruit treated with TiO2 had stronger hardness than control sample
The experiment did not produce a significant difference in the hardness of the fruit, indicating that the number of samples was insufficient or that the conditions were not stable enough to yield accurate results.
4.3.4 Determine the amount of gas released during the ripening of passion fruit