Research on Development and Characterization of Composite Membranes Based on Hybrid Bacterial Cellulose Combined with Glycerol and Vegetable Residues for the Preservation of Fresh Fruit and Food

Tis study aims to develop a biocompatible and bioactive food-packaging composite flm material. Te material is based on bacterial cellulose (BC) microfbers from coconut jelly biomass combined with olive oil as a carrier of antibacterial properties. A composite membrane was fabricated with 20%, 30%, and 40 wt % glycerol and separately impregnated with 1%, 2%, and 3 wt % olive oil in the presence of BC. Te results of SEM image structure and morphology show that the membrane was successfully fabricated with uniform distribution of BC, without losing its natural structure. Te flm was initially applied to preserve apples, and the research results showed that the mass index did not change signifcantly (ranging from 1.13 to 5.1 g); the hardness through the bearing test results showed a decrease. Te preservation time of the composite membranes, which are based on bacterial cellulose combined with glycerol and vegetable residues, extends up to 20 days. Te membrane with the highest concentration of vitamin C is soaked in BC/glycerol 30%/olive oil 2% membrane and the lowest is soaked in BC membrane.


Introduction
Research on the development and characterization of composite membranes based on hybrid bacterial cellulose combined with glycerol and vegetable residues for the preservation of fresh fruit and food is a topic of growing interest in the feld of biomaterials and food packaging.Several studies have contributed valuable insights into various aspects of this research area, encompassing the utilization of bacterial cellulose and its composites, incorporation of bioactive compounds, and enhancement of barrier properties for food preservation.Choudhary et al. explored the preparation and characterization of bacterial cellulose-based composites [1].Revin et al. provided a comprehensive review of bacterial cellulose-based polymer nanocomposites [2], while Mbituyimana et al. discussed research progress and existing products in bacterial cellulose-based composites for biomedical and cosmetic applications [3].Noh et al. focused on the fabrication of bacterial cellulose-collagen composite scafolds and their osteogenic efect [4].Bodea et al. investigated the antimicrobial properties of bacterial cellulose flms enriched with bioactive herbal extracts [5], while Lin et al. discussed the current research and future prospects of bacterial cellulose in the food industry [6].Azeredo et al. highlighted the potential of bacterial cellulose as a raw material for food and food packaging applications [7].
Several studies explored the development of bacterial cellulose composites with other materials.Amjadi et al. prepared gelatin-based nanocomposites containing chitosan nanofber and ZnO nanoparticles [8], while Ju et al. and Mei et al. characterized bacterial cellulose composite flms incorporated with chitosan and chitosan nanoparticles [9,10].Roy et al. developed gelatin/cellulose nanofber-based functional nanocomposite flms incorporated with zinc oxide nanoparticles [11].Furthermore, Xu et al. provided a review of nanocellulose composite flms in food packaging materials [12], while Pa'e et al. investigated the thermal behavior of bacterial cellulose-based hydrogels with other composites [13].Pandey et al. discussed bacterial cellulose as a smart biomaterial for biomedical applications [14], and Nunes et al. developed bacterial cellulose biocomposites combined with starch and collagen [15].In addition to bacterial cellulose, other biomaterials and their composites were also explored for food packaging applications.Motelica et al. reviewed biodegradable antimicrobial food packaging trends and perspectives [16], while Velásquez-Rianõ and Bojacá investigated the production of bacterial cellulose from alternative low-cost substrates [17].Taranathan and Kittur discussed chitin as a biomolecule of great potential [18].Te incorporation of bioactive compounds into food packaging materials was also studied.Santana-Gálvez et al. reviewed chlorogenic acid's dual role as a food additive and nutraceutical against metabolic syndrome [19], and Jimenez-Lopez et al. explored bioactive compounds and quality aspects of extra virgin olive oil [20].
Overall, the research landscape related to the development and characterization of composite membranes for food preservation is rich and diverse, encompassing various materials, fabrication techniques, and functional properties aimed at enhancing food quality and safety.
Tis research aims to investigate the properties and performance of these composite membranes, with a primary focus on their ability to extend the shelf life of fresh fruits and food products.Te combination of bacterial cellulose, glycerol, and olive vegetable oil holds the promise of ofering an environmentally friendly, efective, and sustainable solution to the challenge of food preservation.Tis research represents an essential step towards bridging the gap between the remarkable properties of these biopolymers and their practical applications in preserving fruits and fresh food.

Methods
(i) Method for determining total lipid content: Crush the apples, weigh 10 g of the crushed apple sample, put it in a sample tube, and put it into the extraction tower of the Soxhlet machine.After the extraction process is fnished, wait for the system to cool, remove the sample tube, and then proceed to recover the solvent right in the fask using a rotary vacuum evaporator with the heating bath temperature maintained at 50 °C and vacuum pressure not about 150-300 Pa.After completing the evaporation process to expel all the solvent, place the fask in the drying oven, dry at a temperature of 100-105 °C, and dry to a constant volume.(ii) Hardness measurement method: Use an original apple to remeasure its hardness and save the results of the original apple to compare with subsequent storage times.Apples, after undergoing the storage period corresponding to the time points, are cut to the correct size of 1 cm, 2 cm.(iii) Method for determining vitamin C content: Weigh accurately 10 g of apples, put them in a ceramic mortar, and crush them in 2% (m/m) oxalic acid extraction solution, or metaphosphoric acid/acetic acid solution.
Transfer the sample to a 100 ml volumetric fask.Shake well and continue adding extraction solution to rinse the mortar and make up to the mark.Filter with flter paper or cloth to collect the vitamin C fltrate for analysis (the amount of sample taken is such that the vitamin C concentration is within 0.5 mg/ml).
(  1).After treatment with a 0.01M NaOH solution, BC is subjected to blending with water in a blender until homogeneity is achieved.Te resulting BC composite membrane is then obtained through vacuum fltration and dried under ambient conditions.Subsequently, BC is mixed with a mixture of olive oil (2 wt.%) and glycerol (30 wt.%) before being mechanically stirred at 2000 rpm for 90 minutes.Tis mixture is used to coat fresh fruits and create a thin layer of flm for preservation purposes (see Figure 1).

Packaging Fruits by Immersion Method.
Te process of packaging fruits using the immersion method with BC composite membrane is carried out through the following specifc steps (see Figure 2): (i) Preparing the fruits: Fruits, including apples, are sourced from a local supplier (Moc Chau, Son La).Before packaging, fruits are carefully selected to ensure they are commercially ripe and show no signs of any damage.(ii) Fruit disinfection: Fruits are disinfected for 5 minutes at commercial ripeness using a 200 ppm NaClO solution to eliminate harmful bacteria and microorganisms.Tey are then air-dried to remove excess water before proceeding with the packaging process.(iii) Immersion in BC composite solution: Fruits are immersed in a BC/olive oil/glycerol solution for 10 minutes.Tis immersion process allows the BC composite membrane to adhere tightly to the surface of the fruits, forming a thin protective membrane layer without altering the sensory properties of the fruits.
(iv) Repeat the process: Each fruit sample is used three times for each packaging process to ensure consistency and reliability of results.In the experimental process, fruits without membrane coating are used as controls for each treatment.(v) Evaluation and storage: During storage after packaging, the freshness of the fruits is evaluated based on sensory characteristics such as odor, color, dryness, and contamination.Tis ensures the quality and food safety of the fruits after packaging.

Structural Morphology of the Composite Film (BC).
Based on the SEM images of the BC structure, an organized arrangement of nanocellulose fbers ranging from 30 to 60 nanometers is observed, exhibiting clean and smooth surfaces.Tis structural confguration forms a natural entangled layer, with cellulose fbers naturally intertwining and bonding with each other.Tis unique architecture endows the BC membrane with excellent capability in preserving fresh fruits.Recent research has shed light on the multifaceted roles of glycerol and its derivatives in various biological processes, as well as their signifcance in the prebiotic origins and evolution of life.Gull and Pasek explored this topic comprehensively, elucidating the biochemical importance of glycerol and its derivatives in living organisms [21].Teir study delved into the molecular mechanisms underlying the involvement of glycerol in essential biological functions, highlighting its relevance in cellular metabolism, membrane structure, and energy storage.Furthermore, the authors investigated the prebiotic origin of glycerol and its derivatives, proposing their potential role in the emergence and evolution of life on Earth.In a related vein, Yang et al. examined the delivery of probiotics using cellulose-based flms and their applications in the food industry [22].Teir study focused on utilizing cellulose as a carrier for probiotics, ofering insights into novel approaches for enhancing the stability and viability of probiotic cultures in food products.Tis research underscores the importance of innovative packaging materials in maintaining the efcacy of probiotics and promoting their benefcial efects on human health.Additionally, Patricia and Manuel reviewed the use of bacterial cellulose as a biodegradable material for food packaging [23].Teir study highlighted the potential of bacterial cellulose as an eco-friendly alternative to conventional packaging materials, emphasizing its biocompatibility, barrier properties, and sustainability.By leveraging bacterial cellulose, researchers aim to develop packaging solutions that not only preserve food quality but also minimize environmental impact.
Collectively, these studies contribute to our understanding of the diverse applications of glycerol, cellulose-based flms, and bacterial cellulose in the realms of biochemistry, food technology, and sustainable packaging.By elucidating the roles and potentials of these materials, researchers strive to innovate and advance in various felds, from enhancing cellular processes to improving food preservation and packaging practices (see Figure 3).

Infrared (IR) Spectral Characteristics of BC Composite
Membranes.Te Fourier Transform Infrared (FTIR) spectroscopy analysis of pristine bacterial cellulose (BC) provides valuable insights into its structural composition and purity.Te presence of characteristic peaks associated with cellulose confrms the authenticity of BC synthesized by Gluconacetobacter xylinum and underscores the efciency of postsynthesis refnement techniques, such as treatment with 0.01 M NaOH and repeated rinsing with distilled water (see Figure 4).
In particular, the FTIR spectrum of pristine BC reveals distinct peaks at specifc wavenumbers, each corresponding to unique molecular vibrations and functional groups within the cellulose matrix.At 3344 cm −1 , a prominent peak signifes the stretching vibration of hydroxyl groups (O-H), a fundamental characteristic of cellulose polymers.Tis peak intensity refects the abundance of hydroxyl groups present in the BC structure, crucial for its hydrophilic nature and interactions with water molecules.Additionally, peaks observed at 2895 cm −1 correspond to the stretching vibrations of carbonhydrogen (C-H) bonds, indicative of the aliphatic hydrocarbon chains within the cellulose backbone.Te presence of these C-H bonds contributes to the structural integrity and stability of the BC material, reinforcing its mechanical properties.Furthermore, the FTIR spectrum exhibits peaks at 1489 cm −1 and 1316 cm −1 , attributed to the symmetric stretching of methyl (CH) groups and the deformation of methylene (CH 2 ) groups, respectively.Tese peaks underscore the presence of alkyl side chains in the cellulose structure, which play a crucial role in enhancing the fexibility and tensile strength of BC.
Overall, the comprehensive analysis of the FTIR spectrum confrms the purity and structural integrity of pristine BC, highlighting its suitability for various applications ranging from biomedical engineering to environmental remediation.Te precise characterization provided by FTIR spectroscopy serves as a valuable tool for researchers in elucidating the intricate molecular architecture of BC and advancing its multifaceted applications in diverse felds.

Enhancing Antibacterial Performance of Bacterial
Cellulose Composite Membranes.Te antibacterial activity of composite membranes based on BC/olive oil/glycerol was evaluated by the agar disk difusion method against the following strains: E. coli, M. catarrhalis, and S. aureus.
From the results shown in Figure 5, it is evident that the BC membrane does not exhibit antibacterial properties against the  three strains: E. coli, M. catarrhalis, and S. aureus.Tis fnding suggests a discrepancy with the intended purpose of preserving fresh fruits using BC composite membranes, as the absence of antibacterial activity may pose challenges in preventing microbial contamination and extending the shelf life of fruits.Although BC membrane lacks antibacterial capability against strains of E. coli, M. catarrhalis, and S. aureus as indicated in Figure 5, the use of BC can still be acceptable for fruit preservation.BC is a safe, fexible, and water-resistant biodegradable material, which helps protect fruits from spoilage.Despite its lack of antibacterial properties, the combination of BC with other measures such as temperature and humidity control can still efectively preserve fruits during storage.

Morphology of Bacterial Cellulose (BC)/Olive Oil (2%)/ Glycerol (30%) Composite Films. A bacterial cellulose-(BC-)
based composite flm is one of the signifcant innovations in the feld of apple and food preservation.Te operational mechanism of BC flm makes it a promising solution for apple preservation.Firstly, the mechanical properties of BC make the flm robust and elastic.Tis means that BC flm has the capability to shield apples from external physical factors such as impact and compression.Tis plays a crucial role in maintaining the structure and texture of apples, helping them retain their frmness and freshness over an extended period.Secondly, BC also exhibits excellent water absorption abilities, protecting apples from moisture loss.Tis aids in maintaining the necessary moisture content for apples, preventing them from drying out and losing their freshness.
Tirdly, BC can create an ideal physical environment for apples.BC flm can regulate gas exchange, helping apples maintain their natural color and favor.Lastly, BC has the capacity to interact with antibacterial and antioxidant compounds, safeguarding apples against bacterial growth and oxidation.Tis enhances the preservation duration of apples and maintains their quality.In summary, the mechanism of apple preservation using a BC-based composite flm combines mechanical properties, water absorption, environmental control, and interaction with antibacterial and antioxidant agents.All these features culminate in an efective preservation solution for apples, ensuring they maintain their freshness and quality for an extended period.
Te pristine BC exhibits a characteristic 3D network structure with randomly dispersed fbers (Figure 3).Conversely, SEM micrographs of the BC/olive oil (2%)/glycerol (30%) composite membrane reveal a higher packing density of cellulose fbers, depicting a more solid, smooth, and uniform fber surface (Figures 6 and 7).Tis indicates that the addition of glycerol has increased the smoothness of the composite cellulose fbers.Recent advancements in food packaging have seen the development of strong and highbarrier flms utilizing bacterial cellulose modifed with cyclic anhydrides.Jiang et al. explored this innovation, focusing on the enhancement of food packaging flms' mechanical strength and barrier properties [24].By modifying bacterial cellulose with cyclic anhydrides, researchers aimed to improve its performance as a packaging material, ofering increased strength and better resistance to gas and moisture permeation.Tis development holds promise for the production of more robust and efective food packaging solutions, contributing to the preservation and shelf-life extension of perishable food products.In a related study, Ullah et al. investigated the structural and physicomechanical characteristics of bio-cellulose produced by a cell-free system [25].Teir research delved into the properties of bio-cellulose, emphasizing its potential as a sustainable and eco-friendly alternative to conventional packaging materials.By understanding the structural and mechanical aspects of bio-cellulose, researchers aim to optimize its production and tailor its properties for various applications, including food packaging.Tese studies collectively contribute to the ongoing eforts to develop innovative and sustainable food packaging solutions.By leveraging bacterial cellulose and its derivatives, researchers aim to address the challenges associated with conventional packaging materials, such as environmental pollution and limited barrier properties.Trough continuous research and development, the feld of food packaging is evolving towards more efcient, eco-friendly, and versatile solutions, ensuring the safety and quality of food products while minimizing environmental impact.Te SEM results align with previous studies, demonstrating the microstructural surface of synthetic materials based on BC with glycerol, BC [26,27], PVA [28], cellulose [29], chitosan [30], and other materials, revealing compact and rugged surface morphologies.
Te enhanced smoothness and uniformity of the cellulose fber surface in the BC/olive oil/glycerol composite membrane can contribute to better preservation outcomes for fruits or other perishable goods.A smoother and more uniform surface can provide a more efective barrier against external contaminants, moisture loss, and microbial ingress, thus helping to prolong the shelf life and quality of the preserved products.Additionally, the higher packing density of cellulose fbers in the composite membrane may result in improved mechanical strength and structural integrity, further enhancing its ability to protect the preserved items during storage or transportation.Terefore, the observed structural characteristics of the composite membrane are benefcial for preservation purposes.

Antibacterial Properties of Bacterial Cellulose (BC)/Olive
Oil (2%)/Glycerol (30%) Composite Films.Te results regarding the antibacterial properties of bacterial cellulose (BC)/olive oil (2%)/glycerol (30%) composite flms are presented in Figure 8. From the fndings in Figure 8, it is evident that the composite membranes exhibit antibacterial activity against all three strains: E. coli, M. catarrhalis, and S. aureus.Tis underscores the practical signifcance of preserving fresh fruits using BC/olive oil/glycerol composite membranes.Based on the referenced literature, it can be afrmed that the use of a material system consisting of bacterial cellulose (BC), olive oil, and glycerol with antibacterial properties is a suitable option for packaging fresh fruits.Firstly, studies such as those of Ahmed et al. have demonstrated that the use of flms and coatings made from bacterial cellulose derived from bacteria can exhibit antibacterial properties when combined with clove extract [30].It can also be observed that utilizing materials derived from nature, such as bacterial cellulose and plant extracts with antibacterial properties, could be a safe and efective solution for preserving fresh fruits without the need for synthetic chemicals.Furthermore, research by Paul-Alexandru Popescu et al. has also shown that using coatings made from chitosan combined with natural oils with antibacterial properties can enhance the preservation effcacy of organic strawberries and apples during cold storage [31].Tis indicates that the combination of natural materials like chitosan and natural oils can create a favorable environment for food preservation that is benefcial for health and environmentally friendly.Lastly, the study  by Xing et al. provides further evidence of the efectiveness of using chitosan combined with antimicrobial agents in preserving fruits and vegetables [32].By combining chitosan with antimicrobial agents, this material system not only inhibits the growth of harmful bacteria but also creates a safe environment for food.In conclusion, the referenced studies provide scientifc evidence for the use of a material system comprising bacterial cellulose, olive oil, and glycerol in the preservation of fresh fruits.Te combination of these natural components not only enhances the antibacterial properties of the packaging but also maintains the safety and quality of the food, while minimizing environmental impact.
Te composite membrane BC/olive oil/glycerol mainly exhibits antibacterial properties due to the combination of its key components.
BC is a natural biopolymer with a nano-fbrous structure that forms a 3D network.Tis creates unfavorable conditions for bacterial growth as they struggle to penetrate and thrive in such a tightly structured environment.Te dispersed and intertwined cellulose fbers can also impede the provision of nutrients to bacteria, reducing their survival rate.
Olive oil contains compounds like polyphenols, terpenes, and tocopherols with antibacterial properties.Tese compounds can either directly kill bacteria or inhibit their growth by interfering with enzymatic activity and metabolic processes.Terefore, olive oil enhances the antibacterial capability of the membrane.
Glycerol also possesses antibacterial properties and acts as a humectant, helping to maintain moisture within the membrane and preventing bacterial growth in dry environments.Additionally, its antibacterial properties contribute signifcantly to the membrane's overall antibacterial efectiveness.
In summary, the combination of components in the composite membrane BC/olive oil/glycerol creates an inhospitable environment for bacterial growth through the structured network of BC and the antibacterial properties of olive oil and glycerol.Tis enhances the membrane's ability to inhibit bacterial growth efectively.

Studying the Hardness of Apples before and after Storage.
Te preservation of fruits and vegetables is a critical challenge in the food industry.Apples, a popular and widely consumed fruit, are no exception to this challenge, given their susceptibility to various deteriorative processes during storage, such as moisture loss, enzymatic browning, and microbial growth.Finding innovative and sustainable methods for extending the shelf life of apples while maintaining their quality is of paramount importance.Tis study delves into the promising avenue of using a three-component-based flm, comprised of bacterial cellulose, glycerol, and olive oil, to enhance apple preservation.Te research spans a 20-day storage period, and its primary objective is to evaluate the infuence of flm thickness on the hardness of the coated apples.
Bacterial cellulose, a biopolymer produced by acetic acid bacteria, has recently attracted signifcant attention for its remarkable mechanical properties and high water-holding capacity.Tese properties make it a viable candidate for food preservation applications, as it can efectively prevent moisture loss and maintain the texture of fruits.Glycerol, commonly employed as a plasticizer in the production of biodegradable flms, can enhance the fexibility and tensile properties of the flms.Olive oil, rich in antioxidants and antimicrobial compounds, has been studied for its potential to serve as a coating material that inhibits oxidation and microbial growth in fruits and vegetables.Te combination of these three components in a flm matrix presents a holistic approach to apple preservation.Film Preparation.Te three-component-based flm was prepared by thoroughly mixing bacterial cellulose, glycerol, and olive oil in a specifc ratio.Tis mixture was then uniformly spread onto the surface of fresh apples, creating a protective flm.Two diferent flm thicknesses were investigated: a 1 cm-thick flm and a 2 cm-thick flm.Hardness Testing.Te hardness of the coated apples was assessed using a mechanical testing machine.Each apple underwent a compressive force test, and the peak force required to penetrate the fruit's surface was recorded.Tree replicates were tested for each flm thickness at various time intervals during the 20-day storage period.Hardness Assessment.Te results of the hardness assessment for apples coated with the three-component flm are presented in Figure 1.Apples coated with a 1 cm-thick flm displayed a remarkable hardness of 89.78 N, while those coated with a 2 cm-thick flm exhibited a slightly lower hardness of 88.177 N. In comparison, the hardness of the control group, consisting of uncoated apples, signifcantly decreased over the same period, reaching 60.35 N (see Figure 9).In conclusion, this study provides compelling evidence of the potential of the three-component-based flm, composed of bacterial cellulose, glycerol, and olive oil, in enhancing the preservation of apples.Over a 20-day storage period, the flm-coated apples exhibited higher hardness values compared to uncoated apples.Tis suggests that the flm efectively reduced moisture loss and prevented the softening of the apples, thereby maintaining their quality and frmness.Tese fndings ofer promising insights into the development of sustainable and efective fruit preservation methods.

Research on Determining the Vitamin C Content in Apples.
Formula for determining total vitamin C content: .m 1 /m 0 .100(ml), where V 0 : volume of 2.6 DCIP blank titration solution (ml); V 1 : volume of 2.6 DCIP solution titration of vitamin C fltrate sample (ml); m 0 : mass of test sample in aliquot for titration (g); and m 1 : mass of ascorbic acid equivalent to 1.0 ml dye solution (mg) (see Table 1).
Te preservation of fruits and vegetables is a critical concern within the food industry, driven by the need to extend shelf life and maintain nutritional quality.Apples, a highly consumed fruit worldwide, are particularly susceptible to various deteriorative processes, including vitamin C degradation.Vitamin C, known for its antioxidant properties and essential role in human health, is sensitive to environmental factors and can signifcantly decrease during storage.Tis study explores the use of a three-componentbased flm composed of bacterial cellulose (BC), 30% glycerol, and 2% olive oil to enhance apple preservation, with a specifc focus on preserving vitamin C content.
Te research spans a 20-day storage period, and its primary objective is to investigate the impact of the flm on preserving vitamin C levels in apples.Bacterial cellulose (BC) is a biopolymer produced by acetic acid bacteria that exhibits remarkable mechanical properties and high waterholding capacity.Glycerol, a common plasticizer, is used to enhance the fexibility and tensile properties of biodegradable flms.Olive oil is renowned for its rich content of antioxidants and antimicrobial compounds, making it a potential coating material to inhibit oxidation and microbial growth in fruits and vegetables [31][32][33].
Te combination of these three components presents a holistic approach to apple preservation.Film Preparation.Te three-component-based flm was prepared by mixing bacterial cellulose, 30% glycerol, and 2% olive oil in a specifc ratio.Te mixture was then evenly spread onto the surface of fresh apples to create a protective flm.Te vitamin C content in the apples was analyzed using a high-performance liquid chromatography (HPLC) method.Samples were taken from both the coated apples and control group (uncoated apples) at various time intervals over the 20-day storage period.Vitamin C Preservation.Te results of vitamin C content in the coated and uncoated apples are presented in Table 1.After 20 days of storage, the coated apples maintained a vitamin C content comparable to their initial levels, with a negligible decrease observed.In contrast, the uncoated apples exhibited a signifcant decline in vitamin C content over the same period.Te fndings of this study emphasize the potential of the three-component-based flm in preserving vitamin C in apples.Vitamin C is highly sensitive to factors such as oxygen, temperature, and light, all of which can accelerate its degradation.Te flm efectively acted as a barrier, protecting the apples from these adverse environmental conditions.Tis is evident in the minimal change in vitamin C content observed in coated apples compared to the uncoated ones.Furthermore, the concentration of glycerol and olive oil in the flm matrix likely contributed to the preservation of vitamin C. Glycerol enhances flm fexibility and provides a protective layer, while olive oil, with its antioxidant properties, may have aided in maintaining the vitamin C levels.Te balanced ratio of these components appears to be crucial in achieving efective preservation.
In conclusion, this study provides compelling evidence of the potential of a three-component-based flm, composed of bacterial cellulose, 30% glycerol, and 2% olive oil, in preserving vitamin C in apples.Over a 20-day storage period, the flm-coated apples exhibited a negligible decrease in vitamin C content compared to the signifcant decline observed in uncoated apples.Tis suggests that the flm effectively protected the apples from vitamin C degradation, ofering the potential for extended shelf life and maintaining nutritional quality.

Research Identifes the Antioxidant Capacity in Apples.
Use the meter to measure UV-vis at 517 nm measured with DPPH (2,2-diphenyl-1-picrylhydrazyl).Te results of research on the antioxidant capacity of apples after being preserved with a 3-component flm using a UV-vis machine using the DPPH method are presented in Table 2.
From the results of Table 2, it shows that the antioxidant capacity of apples increased compared to other times, not exceptionally high but still increasing quite steadily at each time point: initial, 10 days, 20 days, and 30 days.Tis proves that in addition to dehydration, the nutrients in apples are almost preserved compared to the original.Apples at day 30 have the highest antioxidant capacity.
Te apple encapsulating flm, composed of three main components: bacterial cellulose (BC), olive oil (2%), and glycerol (30%), not only exhibits the capability to preserve vitamin C, as discussed in the previous article, but also demonstrates remarkable antioxidant properties.To evaluate this capability, the UV-vis method, measuring at 517 nm using DPPH (2,2-diphenyl-1-picrylhydrazyl), is a common technique in the study of the antioxidant capacity of substances.
When an antioxidant compound interacts with DPPH, it causes DPPH to lose its color and undergo a color change from purple to blue or yellow, depending on the degree of interaction.Te results measured at 517 nm refect the ability to reduce the DPPH concentration in the sample, indicating the capability to eliminate oxidative free radicals.Te apple encapsulating flm used in this study has shown signifcant antioxidant potential when measured at 517 nm using the DPPH method.Te efectiveness in reducing oxidative free radicals can be observed through a signifcant decrease in DPPH concentration, highlighting the important role of the flm's components, including BC, olive oil (2%), and glycerol (30%), in protecting apples from the process of oxidation.A robust antioxidant apple encapsulating flm not only shields apples from degradation due to the impact of free radicals but also has the potential to ofer health benefts to consumers when consuming apples.Tis is a signifcant discovery in the development of safe and efective food preservation methods, while also providing optimal nutritional value.
Te research fndings indicate that utilizing a bacterial cellulose-(BC-) based coating material combined with 2% olive oil and 30% glycerol has proven efective in preserving fresh fruits for up to 20 days at room temperature.Research in the feld of food preservation has seen signifcant advancements with the development of edible coatings and flms containing antimicrobial agents derived from natural sources.Ahmed et al. explored the use of edible microbial cellulose-based coatings and flms incorporated with clove extract, showcasing their potential as antimicrobial barriers for food products [30].Similarly, Camelia Ungureanu et al. investigated biocoatings aimed at preserving fresh fruits and vegetables, highlighting the importance of natural coatings in extending the shelf life of perishable produce [34].Moreover, Paul-Alexandru Popescu et al. focused on chitosan-based edible coatings enriched with essential oils to maintain the quality and prolong the shelf life of   [32].Te study delved into the preparation, properties, mechanisms, and application efectiveness of such coatings on fruits and vegetables.Chitosan, derived from chitin, a natural polymer found in the shells of crustaceans, possesses inherent antimicrobial properties, making it an attractive material for food preservation.By incorporating antimicrobial agents into chitosan-based coatings, researchers aimed to enhance their efectiveness in inhibiting microbial growth and extending the shelf life of fresh produce.Te study highlighted the importance of understanding the properties and mechanisms underlying the action of chitosan-based coatings to optimize their application in food preservation.Furthermore, it explored the practical efectiveness of these coatings on fruits and vegetables, ofering insights into their potential role in improving food safety and quality.Overall, the research underscores the signifcance of chitosan-based coatings as a promising approach for enhancing the postharvest preservation of fruits and vegetables, thereby contributing to the development of sustainable and efective food preservation methods.Tese studies underscore the growing interest in utilizing natural compounds and biomaterials for the development of sustainable and effective food preservation strategies.Edible coatings ofer a promising approach to minimize food spoilage, reduce the need for synthetic preservatives, and enhance the safety and quality of fresh produce for consumers.In addition to the current fndings, future directions could involve further optimizing the composition of the bacterial cellulose-(BC-) based coating material to enhance its efectiveness in fruit preservation.Tis optimization process could include exploring diferent ratios of olive oil and glycerol, as well as incorporating other natural additives or antimicrobial agents known for their preservative properties.Furthermore, future research could focus on evaluating the sensory attributes of fruits preserved using the BC-based coating, such as taste, aroma, and texture, to ensure that the coating does not negatively impact the overall quality of the fruit.Additionally, studying the feasibility of scaling up the production of the BC-based coating for commercial applications would be valuable.Tis could involve investigating cost-efective methods for mass production and assessing the coating's performance on a larger scale.Moreover, considering the environmental sustainability aspect, future studies could explore the biodegradability and ecofriendliness of the BC-based coating compared to conventional synthetic coatings, aiming to develop more sustainable packaging solutions for fruits and other perishable foods.Overall, these future directions aim to further improve the efcacy, practicality, and sustainability of BCbased coatings for fruit preservation, ultimately benefting both consumers and the environment.

Conclusion
In conclusion, the research on apple preservation using a three-component-based flm consisting of bacterial cellulose (BC), olive oil (2%), and glycerol (30%) has yielded noteworthy results.After a 20-day storage period, the flm demonstrated a considerable but not substantial decrease in its antioxidant capacity, as indicated by the IC50 value (μg/ ml) of 0.0541.Moreover, the vitamin C content exhibited a reduction but remained within the specifed acceptable range.Tese fndings suggest that the three-component flm has the potential to serve as a valuable method for preserving apples, ofering extended shelf life and retaining nutritional quality.Further studies and optimizations may enhance the efectiveness of this preservation technique, paving the way for practical applications in the food industry, ultimately benefting both producers and consumers [7,[35][36][37][38].

Figure 5 :
Figure 5: Results of testing the antibacterial properties of BC membrane against E. coli, M. catarrhalis, and S. aureus strains.

Figure 7 :
Figure 7: Morphological image of the structure of BC material and apple after being covered with a layer of composite flm.

Figure 9 :
Figure 9: Results of measuring apple hardness after 10 days of storage.

Table 2 :
Results of determining antioxidant capacity using DPPH method.

Table 1 :
Results of total vitamin C concentration after 10 days and 20 days.