Optimization of chemical treatments on the mechanical properties of banana leaves

: Plant leaves, especially from bananas, have been used in food packing for a long time, and it has been proven that banana leaves possess the best attributes in developing bio-degradable packaging materials. The current study aims to determine the effects of four types of chemical treatments on the mechanical properties of banana leaves and to optimize the treatment conditions. Mature banana leaves were immersed in chemicals, namely glycerin (25%, 33%), citric acid (0.5%, 1%), calcium hydroxide (3%, 5%), and sodium chloride (5%, 10%) for seven days while drawing samples daily for testing. The treated samples were tested for mechanical properties such as hardness, tear resistance, and load-bearing capacity, using recommended protocols with slight modifications. The multi-response optimization was done using the statistical method named Grey Relational Analysis to select the best treatment setting. The results revealed that the treatments of citric acid solution (0.5%) for one day and two days, Glycerin (33.3%) for one day and two days, and NaCl solution (10%) for one day were among the first five in the Grey Relational Grades obtained for multi-response optimization and demonstrated a significant (p<0.05) increment for all the three mechanical properties. Hence, the selected chemical treatments positively affect the mechanical properties of banana leaves at their optimum treatment conditions.


INTRODUCTION
Single-use food packaging is exerting a substantial impact on our ecosystem.The accumulation of plastic bags, Styrofoam food containers, disposable coffee cups, and other materials in landfills and waterways indicates that the comfort of food packaging is overshadowed by the environmental damage it generates.Nevertheless, food packaging materials containing substances such as phthalates for plastic flexibility, perfluorinated chemicals for liquid containment in cardboard, and bisphenol linings in aluminium cans, poses risks to human health (Geyer, 2017).
Although all countries contribute to environmental pollution by releasing plastic waste, particularly Sri Lanka stands out as a significant contributor to plastic pollution.
Further, the country has drawn attention to the extensive harm inflicted by plastic waste as it is in the midst of the ocean.The deteriorating conditions profoundly affect the local ecosystem, residents, marine biodiversity, and the depletion of food resources.In the global context of plastic pollution, Sri Lanka ranks consistently among the top ten nations with heavy plastic pollution, impacting various forms of wildlife and posing threats to human well-being (Amarasinghe et al., 2020).
In the last few decades, many researchers have tried to find new packaging materials with better properties, most importantly nature-friendliness, that would be used in industry.Today, people are more concerned about green material consumption in the industry that could protect the delicate environmental balance (Kalina et al., 2024;Nongman et al., 2015;Baldwin et al., 2001) Studies focused on the fact that plant and tree leaves of various plant families are used as single-leaf plates, stitched dining leaf plates, food wraps, and food packing materials as they are biodegradable and amenable (Kalina et al., 2024;Kora, 2019;Sarin, 2017).Among the locally available resources, leaves from many different plant materials, including banana, teak, jack, banyan, kottamba, and the leaf sheath of areca nut, are amenable for commercial leaf plate making.Recent studies have proven that these materials have good physical properties, and those can be used by converting them into wrappers, plates, and cups (Kalina et al., 2022;Kora, 2019).
Banana (Musa spp.), which falls under the Musaceae family, represents a significant tropical and subtropical fruit crop that is grown across an estimated 9 million hectares globally (Mohapatra et al., 2010).Musa paradisiaca, on the other hand, is characterized as a herbaceous plant with a height potential of up to 9 meters, showcasing a sturdy treelike pseudo stem along with a cluster of sizable elongated oval deep-green leaves reaching lengths of up to 365 cm and widths of 61 cm, featuring a distinct midrib (Imam & Akter, 2011).Banana leaves are oval-shaped and have considerably larger surfaces, which makes them feasible in food packaging applications (Kalina et al., 2024).They have broad applications ranging from cooking, wrapping, and food serving in wide cuisines, especially in tropical and subtropical regions (Ng, 2015;Walia et al., 2017).
Banana leaves and sheaths were used in making biodegradable food packaging sheets by eco-friendly methods using the Xylanase enzyme, embedded in calcium alginate beads and the process involved bio-pulping, biobleaching, and layering using mould and deckle (Jeenusha & Amirthakumar, 2020).
Further, a recent study extended the shelf life of banana leaves by six months and enhanced thermal and mechanical strength through compression moulding followed by drying (Arumugam et al., 2023).Another study was performed to develop banana leaf fiber (BLF) reinforced thermoplastic cassava starch composites by incorporating fiber extracted from banana leaf and thermoplastic cassava starch formulated with 27% glycerol and 10% bee wax (Jumaidin, 2021).Similarly, laminated composites were made by laminating the binderless banana stem particle boards with banana leaf tapes using adhesive as a doublesided tape.The banana leaf tapes were produced by soaking in a solution of one-part glycerin in three parts of distilled water at 80 o C for 3 seconds, followed by heat pressing at 70 o C (Nongman et al., 2015).
Not only the leaves of bananas, but also other parts such as the stem, sheath, and fruit peels were also used in developing packaging films.Attempts have been made to synthesize biodegradable plastic material using banana peels by incorporating glycerol (Chandarana & Chandra, 2021;Beevi et al., 2020;Ramadhany et al., 2021;Shah et al., 2021).
Apart from banana, studies proved that cellulose extracted from lotus stalks by boiling in NaOH (10%) solution can be used to make containers, which was found to yield the best result in increasing the tensile strength, tear strength, and durability of the containers and food cans.Those were able to be stored longer than 24 hours in their original condition without adding preservative (Manoi et al., 2015).Another study disclosed that packaging sheets can be formed from cassava leaves after a conventional mercerization treatment with a mild concentration of NaOH (15%) solution while eliminating the toxic compound (HCN) (Sharif et al., 2014 andSharif et al., 2015).
Meanwhile, bio-based plastics are formulated from renewable sources like corn, wheat, potatoes, and vegetable oil through a chemical or biological modification that includes acidification, hydrolysis, microbial fermentation, etc. (Babu et al., 2013;Venkatachalam & Palaniswamy, 2020).Bio-based plastics produced from plant and animal biomass have exhibited good thermal and mechanical properties and high biodegradability, making an alternative way to reduce synthetic plastic and create an eco-friendly environment (Patel et al., 2019;Popa et al., 2011).Bioplastics from cassava starch and glycerol degraded completely on the ninth day of soil burial.The increased glycerol concentration would increase moisture, speed up the microbial degradation process, and extend the shelf life of bioplastics in a dry place (Wahyuningtyas & Suryanto, 2017).
Plastic is most widely used as a food packaging material due to its versatility, durability, flexibility, and lower price.Hence, recent and ongoing studies are thriving to find alternative raw materials with qualities equal to or better than plastic, while the material has to be nature friendly.To cope up with the current demand for biodegradable packaging materials and as a propelled search for better alternatives to plastic, this study analyzed the effects of various chemical treatments on the mechanical properties of banana leaves to be used as a compatible source in developing a cheap, sustainable, eco-friendly packaging material.

Materials
Fresh mature banana leaves were randomly collected from different regions of the Jaffna peninsula (9°40'6.42"N,80°0'26.71"E).The chemicals used for treatments were food-grade and obtained from Neochem International (Pvt) Ltd.

Sample Preparation
The collected banana leaves were cleaned with dechlorinated running tap water to remove dirt and foreign particles and reduced in size before being subjected to the following chemical treatments.

Experimental Design
A General full factorial design was used in performing the experiments to evaluate the response variables while employing 4 chemical treatments as given in Table 1.
Table 1: Treatment details and conditions used in the experiment.

Chemical
Concentration Time period (No. of days)

Application of Chemical Treatments
The banana leaves were immersed in different concentrations of Sodium Chloride solution (5% and 10% W/V), Calcium Hydroxide solution (3% and 5% W/V), Citric Acid solution (0.5% and 1% W/V), and Glycerin solution (25% and 33.3 % V/V) for one week.The concentrations for each chemical treatment were selected, according to the findings of previous studies (Chung et al., 2020;Trisnawati et al., 2019;Akbas & Olmez, 2007;Megha et al., 2019 respectively).Also, preliminary trials were carried out to screen out and confirm the selected concentrations.During the immersing period of one week, S. Kalina et al. for a test condition repeated 'n' times. Step

2: Normalization of the S/N Ratios
The normalization values of the three output responses were calculated using Eq. ( 2) which is applied for the 'larger the better' case.
Z ij = Normalized value for the experiment for j th response Eq.( 2) (to be used for S/N ratio with larger -the better case) Step 3: Calculation of Grey relational co-efficient The Grey relational coefficients (GC ij ) of the three output responses were computed using Eq. ( 3).
Eq.( 3) Step 4: Calculation of Grey relational grades The Grey relational grades (G i ) of the three output responses were calculated using Eq.(4).
Eq.( 4) Where, m is the number of output responses. Step

5: Ranking based on Grey relational grades
Finally, all the experimental runs were ranked based on their Grey relational grades to identify the treatment setting (combination of concentration and time duration) in the order of optimum responses for mechanical strength.

Statistical Analysis
The data were collected as fifteen replicates for hardness and five for load-bearing capacity and tear resistance and analyzed using simple descriptive statistics, graphs, and computation of Grey Relational grade values in MS Excel 2016 and MINITAB 17 was used for further analysis.The effects of chemical treatments on the mechanical properties of leaves were studied using paired sample t-tests, where the means comparisons were performed using Tukey's test at P<0.05 significant level.
samples were drawn from each treatment every day, kept one day for ambient air drying, and evaluated changes that occurred in mechanical properties of banana leaves.

Hardness
The hardness of the banana leaves was measured at 15 random points using an analogue-type Shore durometer LXA-1 with a 0~ 100HA dial scale, needle pressure of 0.55 N-8.05 N, and a single pointer.The test scale and method used are ASTM D2240-Type A and ISO 868 (Kumar et al., 2021).

Tear Resistance
The tear resistance of samples was determined using a method designed in line with the method recommended by Defoirdt et al. (2010), Iewkittayakorn et al. (2020) and Elmendorf Tear method (ASTM D-1922) and with few modifications.A rectangular strip of banana leaf (15 × 5 cm 2 ) was cut and split longitudinally in the middle to halfway up to a depth of 2 cm.The left longitudinal edge was fixed without moving, and the other cut half was attached to a digital balance using paper clips.Then, the force required to tear off the leaf material into two pieces was recorded by dragging the other end horizontally at a uniform velocity (10 cm/s) on the right longitudinal edge using the balance.

Load Bearing Capacity
The load-bearing capacities of the banana leaves were evaluated using mass hangers following a method designed in line with the method recommended by Defoirdt et al. (2010) and Arifin et al. (2023) and with few modifications.Mass hangers were allowed to hang on a rectangular strip of plant material (15 × 0.5 cm 2 ) with the support of paper clips and a metal stand.Then, the weights in the mass hanger were increased at a rate of 1g/s until the strip of leaf material was broken apart.The maximum weight that the leaf material can bear was recorded.

Optimization of treatment conditions
Grey Relational analysis was used to select the optimum chemical concentration-time combination for the best treatment in terms of the enhancement of the stipulated three mechanical properties tested.The calculation of Grey Relational Grades was done by resorting the five steps given below according to the method explained by Krishnaiah and Shahabudeen (2012).
Step 1: Calculation of S/N Ratios The arithmetic mean of the three output responses in the matching experiments was calculated using S/N ratios while applying Eq. ( 1).As all three responses are positive indications of the mechanical strength of the tested material, the 'larger the better' case was applied to compute the S/N ratio.
Eq.( 1) Where Yi is the output responses of the matching treatment

RESULTS AND DISCUSSION
The purpose of food packaging is to preserve the quality and safety of the food it contains from the time of manufacture to when the consumer uses it.An equally important role of packaging is to protect the product from physical, chemical, or biological damage (Dallyn & Shorten, 1998).Synthetic materials are well-equipped to fulfil the aforementioned requirements.Similarly, the alternative materials under development should be on par with the above requisites.Hence, finding the most suitable processing techniques for transforming target materials to have equal or better properties than that of synthetic plastics is essential.

Effects on the Hardness
The selected chemical treatments, namely Glycerin, Citric acid, Ca(OH) 2 , and NaCl solutions, had varying impacts on the hardness of banana leaves as shown in Figure 1.
Glycerinization is the process of preserving botanical specimens using glycerol.By this method, the internal moisture within plant components is substituted with glycol, thus maintaining their original characteristics in terms of texture, shape, and colour.The treated plant parts exhibit a more authentic appearance than the leaves that had been air-dried, as they are less susceptible to breakage and physical damage (Leonard, 1973;White et al., 2007).
According to this study, the hardness of banana leaves has been significantly (P< 0.05) increased in the first day with both concentrations (25% and 33.3%) of Glycerin; however, this phenomenon did not differ significantly thereafter (Figure 1a).The trend of hardness change in banana leaves due to the two concentrations of Glycerin each day was almost similar.Further, the banana leaves immersed in 25% Glycerin solution for one day had the highest hardness value (24 ± 2 HA).
However, in the case of citric acid treatment with concentrations of 0.5% and 1% (Figure 1b), the hardness of banana leaves significantly decreased (p<0.05) against untreated (16 ± 2 HA) for both concentrations and reached near to 1 HA.After the treatment of day four (4), the decreasing pattern was higher in 0.5% than 1% (citric acid).Citric acid can modify the properties of plant tissues by altering hydrolysis, pectin gelation, and depolymerization of pectin, which improves the rate of water removal and provides tenderness to the tissues of the material which results in reduced hardness for dried food products (Liu et al., 2021;Sette et al., 2016).Meanwhile, there are possibilities to form cellulose nanocrystals when banana leaves are subjected to alkalization, acidified chlorination, and citric acid hydrolysis (Kumar et al., 2023).Citric acid has been extensively used for its anti-browning activity in minimally processed fruits and vegetables (Ahvenainen, 1996) and specifically on fresh lettuce (Altunkaya & Gökmen, 2008;Pace et al., 2020) because it is categorized as edible with a permitted concentration.
Calcium hydroxide (Ca(OH) 2 ) can be applied due to its capacity to reinforce the surface fruit tissues to maintain the fruits intact during the process of heating (Trisnawati et al., 2019).In the case of banana leaves treated with Ca(OH) 2 (Figure 1c), the re is a noticeable increment in the hardness from the first day of 3% (23 ± 1 HA) and 5% (25 ± 2 HA).However, thereafter, a gradual increment was observed in both concentrations, but the increment was significantly higher in the 5% concentration, where the observed maximum hardness value (30 ± 1 HA) was recorded on the fifth day of 5% Ca(OH) 2 treatment.
NaCl was an inhibitor of polyphenol Oxidase (PPO) activity in peaches.PPO activity could be inhibited by NaCl as well as ascorbic acid and citric acid (Demir & Kocacaliskan, 2001;Fan et al., 2005).Immersing the plant explants in NaCl not only effectively prevents the browning of petal explants but also displays positive synergistic effects when combined with polyvinyl pyrrolidone (PVP) in the growth medium (Cai et al., 2020).Moreover, the application of NaCl (50 mM) was shown to counteract the inhibitory impact of water deficiency on the photosystem II activity in the succulent zerophyte (Ma, 2012).Similarly, an osmotic treatment involving a high level (300mM) of CaCl 2 induces stomatal closure, thus reducing water loss and prolonging the shelf life of viola plants under conditions of water deficit stress.(Park et al., 2020).
The change in the hardness of banana leaves in NaCl solution (5%, 10%) follows a varying pattern (Figure 1d).The hardness values decreased on the first day of NaCl treatment for both concentrations and where there was a gradual increase after that.The maximum hardness value (22 ± 2 HA) was observed on day five (5) of 5% NaCl and the day seven (7) of 10% NaCl.

Effects on Tear Resistance (TR)
When compared with the fresh banana leaf (Figure 2a), the tear resistance was significantly (P<0.05)higher on the first day and 1 st and 2 nd days of 25 and 33% Glycerin treatments respectively.Thereafter, TR gradually reduced back to original level during treatment period for both concentrations.The treatment of 33.3% Glycerin for one day had the highest TR (3.33 ± 0.26 N) for the banana leaf with a thickness of 0.3 mm.
Further, there is a significant increase (p<0.05) in the tear resistance of banana leaves after day one (1) and day one (1) and two (2) of 1 and 0.5% of citric acid treatment, respectively.Afterwards, the values of TR of leaves in both concentrations reduced remarkably, even beyond the value of the fresh leaves (Figure 2b).The highest TR value (3.50 ± 0.21 N) was recorded by 0.5% citric acid after treatment on the 2nd day of the treatment; however, this was not significantly different (p>0.05) from the effect of the day one treatment of 1% of citric acid (3.34 ± 0.11 N) and significantly (p <0.05) higher than the TR value (3.01 ± 0.11 N) after one (1) day treatment with 0.5% citric acid.
The packaging sheets formed from cassava leaves treated with a mild concentration of NaOH (15%) solution had good tear index value (784.7 mN•m 2 /g.), smooth sheet formation, low moisture uptake, and reasonable wetting time.The untreated cassava sheets had a tear index of 64 mN•m 2 /g.Further, the cassava leaf sheets impregnated with cassava starch acetate had an improved tear index value higher than 785 mN•m 2 /g (Sharif et al., 2014;Sharif et al., 2015).In addition, the tear strength of fabric tents ranges between 200N and 250N (Eltahan, 2018).In the case of Ca(OH) 2 (Figure 2c), the TR of treated banana leaves had significantly (P<0.05)increased for both concentrations (5% and 10%), and the maximum tear resistance value (2.84 ± 0.17 N) was observed on the sixth day of 5% Ca(OH) 2 treatment.
Similarly, with the NaCl solution (Figure 2d), the tear resistance of banana leaves significantly increased (p<0.05) after one day of both treatments.Thereafter, the TR of banana leaves gradually decreased, and on the seventh day, the 10% NaCl treated leaves reached the minimum TR value (2.50 ± 0.13 N).However, the maximum tear resistance value (3.44 ± 0.18 N) was observed on the second day of 10% NaCl treatment.

Effects on Load-Bearing Capacity (LBC)
Load-bearing capacity is a similar indication of a property named tensile strength, which is commonly evaluated for packaging materials to assess how they can bear the pulling (tensile) force.Composites made by laminating "banana stem particle boards" with banana leaf tapes treated with 25% glycerin had a maximum tensile strength of 2.2 MPa (Nongman et al., 2015).Biofilm made out of the starch of mature banana peels with 20% glycerol had the highest tensile strength values in the range of 4.18 MPa (Ramadhany et al., 2021).The values of edible films from tapioca, glycerol, and carrageenan ranged from 0.434 N/ cm 2 to 1,434 N/cm 2 (Kusnadi & Budyanto, 2015).
Compared with the fresh banana leaves (Figure 3a), the load-bearing capacity significantly increased (p<0.05) during the first day after treating them with 33.3% Glycerin.However, the LBC decreased afterwards.In the case of the banana leaf, which was treated with 25% Glycerin, LBC increased during the first three days' period, and subsequently, it decreased gradually.The treatment of 33.3% Glycerin had the highest LBC value (2.18 ± 0.08 N/ 1.64 ± 0.06 MPa) during day one.This LBC value was higher than the tensile values of biodegradable trays (0.012 to 0.024 MPa) made from cassava starch and corn husk, with glycerol, potassium stearate, and guar gum (Aguirre, 2023) and of an opaque film (0.07 MPa to 0.28 MPa) made out of starches of cassava and corn (Akmeemana et al., 2024).
Further, when the leaves were subjected to Citric acid treatment (Figure 3b), higher values for LBC were observed after one day with 1% citric acid as well as first two days with 0.5% citric acid.Thereafter, the LBC values of banana leaves treated with both solutions were progressively declined and subsequently those values gone behind the values of fresh leaves.The highest value of load-bearing capacity (2.58 ± 0.10 N/ 1.94 ± 0.08 MPa) was recorded by the leaves immersed in 0.5% citric acid solution for one day; however, which was not significantly different (p>0.05) from the effect after two days with 0.5% (2.45 ± 0.11 N/ 1.84 ± 0.08 MPa) and significantly higher (p>0.05)from the effect after one day with 1% (2.25 ± 0.10 N/ 1.69 ± 0.08 MPa) citric acid solutions.
Flexural palmyra palm petiole composites formed by treating fibers of palmyra leave petioles with 0.625 M NaOH had good mechanical properties, mainly tensile strength (56.69 MPa) and impact strength (97.07%) (Srinivasababu et al., 2014).In the case of Ca(OH) 2 (Figure 3c), LBC of banana leaves significantly increased from the first day for both concentrations (3 % and 5 %).The maximum tear resistance value (2.26 ± 0.11 N/ 1.70 ± 0.08 MPa) was recorded on the seventh day of 5% Ca(OH) 2 treatment, and which was, however, less than the research outcome of the semi-refined iota carrageenan films prepared by incorporating SiO 2 nanoparticles as filler using the solution casting method and which had a maximum tensile strength of 11.68 MPa (Aji et al., 2018).
Further, with the NaCl solution (Figure 3d), the loadbearing capacities of banana leaves remarkably increased after the first two days of 10% NaCl.Thereafter, they fall into the values of fresh banana leaves.Nevertheless, the higher LBC value (2.27± 0.20 N/ 1.70± 0.15 MPa) was observed for 10% NaCl on the first day of treatment.
According to the literature, paper made from pineapple leaf pulp had improved physical and mechanical properties when coated with bio-coating.The maximum tensile strength of the developed sheets was found to be 5.9 kN/ m 2 (Iewkittayakorn et al., 2020).The tensile strengths obtained for potato and yam starch-based bioplastic were 0.6 MPa and 1.9 MPa, respectively (Ismail et al., 2016).
Further, bioplastic films were developed using starch from jackfruit waste and sago mixed with lemon extract and water but with different cross-linkers such as polylactic acid, crude palm oil, and glycerol and the film made with polylactic acid and crude palm oil showed the best tensile strength (TS) of 5.24 MPa and the lower elongation at break (EAB) of 3.49% (Krishnamurthy & Amritkumar, 2019).On the other hand, the tensile strength of synthetic polypropylene was 3.8 MPa (Chiellini, 2008).
The selected chemical treatments improved the tensile strength of banana leaves; however, further improvement in the mechanical properties of banana leaves needed to be achieved by combining different physical and chemical treatments at their optimum level.

Optimization of Treatment Conditions
The results of grey relational analysis (Table 2) indicated that the highest response in all three tested mechanical properties (Grey Relational Grade, GRG) = 0.839) was obtained after the treatment with 0.5% citric acid for one day and which is followed in order by citric acid (0.5%) two days, Glycerin (33.3 %) for one day and two days, NaCl solution (10%) for one day.Meanwhile, out of all the experimental runs, the lowest GRG was obtained for the treatment with 1% citric acid for seven days (GRA = 0.333).The best-selected treatments not only enhanced the mechanical strength but also were previously proved to have beneficial contributions to the plant materials when treated. S. Kalina et al.The first two treatments in the optimization order were citric acid (0.5%).In a study evaluating citric acid-treated natural fibres as sustainable additives for improving soil performance in highway construction, 5 % citric acid was used to treat rice husk and sawdust fibre to enhance their durability (Fadugba et al., 2024).Citric acid has been utilized as a chemical fixing agent in textile finishing processes to enhance textile properties such as antiodour, low-shrinkage capabilities, wrinkle resistance, and antimicrobial characteristics.Following degumming with citric acid, the tensile strength of silk fiber demonstrated an increase to 507 MPa (Natarajan & Thilagavathi, 2023).
The third and fourth best treatment was Glycerin (33.3%).Glycerin, a chemical humectant, can penetrate plant tissue through transpiration stream uptake or by submerging the trimmed foliage in the solution.It aids in the preservation of foliage by substituting the inherent moisture in the leaf with glycol, thereby maintaining the form, texture, and color of the leaf (Bale, 2006).Glycerin drying is the most suitable method for drying foliage as the leaves absorb enough liquid and look soft and pliable (Megha et al., 2019) and 10%-30% glycerol solution in water gives best results on actively growing foliage (Dilta et al., 2011;Yeptho et al., 2023).
A study was conducted to evaluate the impact of glycerin on the drying process of cut foliage of Polystichum squarrosum.The study revealed that the highest level of quality parameters, such as textural quality, shape retention, brittleness, and overall acceptance, was observed when the leaves were subjected to a 40% glycerin solution using the full-dip method.This same concentration of glycerin also led to an increase in leaf weight, minimal changes in leaf area, and a low percentage of leachate (Priya et al., 2018).
Further, NaCl treatment was ranked fifth among the ten best treatments selected.According to a study, when the leaves of astringent persimmon at the tender stage were treated with NaCl solutions of different concentrations (1, 5, 10, 15, and 25%) for 30 days at 10°C, higher NaCl concentrations could help maintain a darker green colour (Chung et al., 2020).
The Ca(OH) 2 treatment was also ranked among the order from fifth to tenth best treatments.The Ca(OH) 2 can act as a moisture scavenger, destroying microorganisms that may be present in the air within the packaging environment.It can also prolong freshness by preventing the packaging contents from spoiling for 1-4 weeks.Preferably, the Ca(OH) 2 can be used at a concentration of 5% to 50% W/V (Meade, 2016).Moreover, the packaging materials for Kimchi packaging containing the adsorption powder impregnated with calcium hydroxide and porous medium showed improved mechanical properties.They exhibited chemical and physical reactions, producing strong adsorbent power and reusability (Lee et al., 2019;Jeong et al., 2024).

CONCLUSION
Based on the results, most of the chemical treatments significantly affected the mechanical properties of banana leaves.Among them, 0.5% citric acid was optimum in all three mechanical properties.Hence, it is feasible to transform banana leaves into versatile packaging material while applying simple chemical treatments, especially citric acid, at optimum concentration and time duration.However, combining different treatments would result in further improved properties of raw materials for developing packaging materials.Further studies are underway to transform banana leaf to the optimum form, proceeding the provision of optimal treatments.

Figure 1 :Figure 2 :
Figure 1: Changes in the hardness values of banana leaves after the treatments with (a) glycerin, (b) citric acid, (c) Ca(OH) 2, and (d) NaCl for seven days

Figure 3 :
Figure 3: Changes in the load-bearing capacity values of banana leaves after the treatments with (a) glycerin, (b) citric acid, (c) Ca(OH) 2, and (d) NaCl for seven days

Table 2 :
The ten best chemical treatment conditions for banana leaves given in the rank order of their Grey Relational Grades (GRG) obtained through the optimization technique of Grey Relational Analysis.