Characterization And Chemical Composition Of Epicuticular .

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Songklanakarin J. Sci. Technol.39 (4), 509-516, Jul - Aug. 2017 ArticleCharacterization and chemical composition of epicuticular waxfrom banana leaves grown in Northern ThailandSuporn Charumanee1*, Songwut Yotsawimonwat 1, Panee Sirisa-ard 1, and Kiatisak Pholsongkram21Department of Pharmaceutical Sciences, Faculty of Pharmacy,Chiang Mai University, Mueang, Chiang Mai, 50200 Thailand2Department of Food Science and Technology, Faculty of Sciences,Payap University, Mueang, Chiang Mai, 50000 ThailandReceived: 22 April 2016; Revised: 2 July 2016; Accepted: 16 July 2010AbstractThis study aimed to investigate the physicochemical properties and chemical composition of epicuticular waxextracted from leaves of Kluai Namwa, a banana cultivar which is widely grown in Northern Thailand. Its genotype wasidentified by a botanist. The wax was extracted using solvent extraction. The fatty acid profiles and physicochemical propertiesof the wax namely melting point, congealing point, crystal structures and polymorphism, hardness, color, and solubility wereexamined and compared to those of beeswax, carnauba wax and paraffin wax. The results showed that the genotype of KluaiNamwa was Musa acuminata X M. balbisiana (ABB group) cv. Pisang Awak. The highest amount of wax extracted was 274 g/cm2 surface area. The fatty acid composition and the physicochemical properties of the wax were similar to those ofcarnauba wax. It could be suggested that the banana wax could be used as a replacement for carnauba wax in variousutilizing areas.Keywords: epicuticular wax, banana wax, Kluai Namwa, Musa spp. carnauba wax1. IntroductionBanana (Musa spp.) is one of the most widelycultivated plants in Thailand. All parts of this plant are usedin daily life (Debabandya et al., 2010). Unripe and ripe fruitswhich can be harvested year-round are known as functionalfruits, providing nutritional and medicinal values (SampathKumar et al., 2013). Banana leaves are commonly used forfood wrapping and decoration because they are large, flexibleand waterproof. However, they are less frequently usednowadays and largely replaced by plastic. After harvestingthe crop, the mature leaves are considered as agriculturalwaste and they are often destroyed by burning that leads to* Corresponding author.Email address: pollution. However, it is interesting that, the outermostpart of banana leaf is covered with lipid substance, which isso-called the epicuticular wax. This wax is solid mixtures,composed of esters of long chain fatty acids and long chainfatty alcohols, free fatty acids, fatty dialcohols (diols),aldehydes and n-alkanes (Freeman & Turner, 1985; Yanagidaet al., 2005a). This surface wax serves as a mechanical barrierwhich protects the plant tissues against UV radiation andbacterial or fungal attacks and also reduces water loss insummer time (Riederer & Schreiber, 2001). Nowadays,carnauba wax is the most commonly used natural wax invarious industries especially, for polishing leathers, glasses,wooden furniture and automobiles. Interestingly, it is also acommon ingredient in pharmaceutical and cosmetic products.This point of view leads us to generate the idea of usingbanana leaves as a natural source of waxy substance. Fromthe extensive literature review, studies involving extraction

510S. Charumanee et al. / Songklanakarin J. Sci. Technol. 39 (4), 509-516, 2017and characterization of the epicuticular wax from bananaleaves have been scarcely reported. Those noteworthy oneswere reported by Freeman and Turner (1985), and Yanagidaet al. (2003; 2005b). According to Freeman and Turner (1985),epicuticular waxes from leaf, flower bracts and fruits of 12banana (Musa spp.) varieties were extracted and examinedtheir chemical compositions. Fruits gave higher wax contentfollowed by bracts and leaf respectively. The wax from leaf infield-grown banana was about 230 mg/cm2 was 60% higherthan those planted in a glasshouse. In addition, Thailand hasnumerous cultivars of banana, while the yield, characterization and chemical composition of epicuticular wax frombanana leaves grown in Thailand has never been investigatedThe objectives of this study were to investigate andcharacterize the chemical composition and the properties ofwax isolated from leaves of Kluai Namwa, a banana cultivarwhich is widely grown in Northern Thailand and to compareits properties to those of other waxy substances includingcarnauba wax.2. Materials and MethodsThe following waxy substances were used to comparetheir physicochemical properties with the banana waxnamely, beeswax (S. Tong Chemicals Co. Ltd. Lot. P011814,Bangkok, Thailand), carnauba wax (Union Sciences Co. Ltd.Lot. 9776, Chiang Mail, Thailand) and paraffin wax (B. L. Hau& Co. Ltd. Lot. 7117L14, Bangkok, Thailand).2.1 Sample preparationKluai Namwa grown in Northern Thailand particularlyin Chiang Mai, Lampang, Pitsanulok and Tak provinces werecollected as samples for wax extraction. Fresh leaves wereused for wax extraction. After measuring their surface areas,banana leaves were hung in the air to keep them partiallydried and dust was removed using an air blower. All reagentsand chemicals used were of analytical grade.2.2 Extraction of epicuticular waxThe epicuticular wax was extracted from bananaleaves by sohxlet apparatus using n-hexane as a solvent andthe solvent was removed by using a rotary evaporator. Theextracted wax was purified and decolorized using activatedcharcoal. Briefly, 1% w/v of activated charcoal was added tothe hot hexane extract. The mixture was frequently stirred fora few minutes then filtered through filter papers (Whatman No. 5, Sigma-Aldrich St. Louis, MO, USA) using vacuumfiltration. The decolorization process was repeated 3-5 timesdepended on the color intensity of the hexane extract. Theresidual of hexane in the wax was quantified by gas chromatography. The codes were assigned to the extracted waxesaccording to their origins i.e., BNS, BNP, BNT, BNTk whichrepresented banana leaves cultivated in Chiang Mai,Pitsanulok, Lampang and Tak provinces, respectively.2.3 Identification of banana cultivarsKluai Namwa from different origins were identifiedand authenticated by the botanist at Queen Sirikit BotanicalGarden, Department of Forest, Ministry of Natural Resourcesand Environment in Chiang Mai.2.4 Verification and determination of chemical compositionsin the wax2.4.1 Thin layer chromatographyThin layer chromatography (TLC) technique was usedto verify the chemical composition of the wax. The stationaryphase was Silica Gel 60 F254 and the mobile phase was themixture of hexane: ethyl alcohol: acetic acid 50:50: Gas chromatographyFatty acid composition of the extracted wax wasdetermined by using gas chromatography (GC), ShimadzuGC 2010 equipped with DB-23 column and a flame ionizationdetector. The sample was injected in a split mode with a splitratio of 1:50 and an injector temperature of 250 C. Thetemperature program started with an initial temperature of80 C, increased at a rate of 10 C/min up to 180 C, hold for15 min, increased with a ramp rate of 4 C/min to reach a finaltemperature of 220 C with a final hold time of 7 min; theduration of the total temperature program was 42 min. Thedetector temperature was set at 300 C. Helium was used asa carrier gas at a flow rate of 62.9 ml/min.2.5 Acid number determinationThe acid value of the samples was determined usingthe method previously described (Suzanne, 2010). Briefly,the wax was dissolved in ethanol at 50 C. The mixture wastitrated with standardized solution of potassium hydroxideusing phenolphthalein as an indicator. A blank was alsoundertaken in the same manner. Acid value was calculatedfrom the amount of standardized solution of potassiumhydroxide used for wax and blank titration. The experimentwas performed in triplicate.2.6 Saponification number determinationThe determination of saponification number wasperformed according to the following procedures (Suzanne,2010); the wax was mixed with alcoholic 0.4 M KOH andrefluxed for 30 min. The resultant solution, after the additionof phenolphthalein, was titrated with standardized solutionof 0.5 M hydrochloric acid. A blank was also carried out.Saponification value was calculated from the amount ofstandardized hydrochloric acid solution used for sample andblank titration. The experiment was performed in triplicate.

S. Charumanee et al. / Songklanakarin J. Sci. Technol. 39 (4), 509-516, 20172.7 Characterization of physical properties2.7.1 Determination of melting point, congealing point andpolymorphism by DSCThe melting point and the congealing point of thewax was determined using differential scanning calorimeterDSC 7 (Perkin Elmer, USA). The sample weighed 3.0-3.5 mgwas placed in an aluminum pan with holes. The heatingexperiment was studied from 50 C to 100 C at a heating rateof 5 C/min and followed by the cooling experiment from100 C to 50 C under the same cooling rate. Nitrogen wasused as purge gas at a flow rate was 20 ml/min.2.7.2 Examination of internal crystal structureX-ray diffractometer (Siemens-D 500, Germany) wasused to examine the internal structure of the wax crystals atroom temperature using the following conditions: voltage,20 kV; current, 20 mA; time constant, 0.5 second; scan speed,4 q/min and scattering angle range (2q) of 5-30 .2.7.3 Examination of crystal modifications (Habits)The crystal modification of wax crystals was examinedusing scanning electron microscope (JSM-5910LV, Jeol,Japan).2.7.4 Hardness measurementThe hardness of wax was determined using TextureAnalyzer TA.XT2i (stable micro system). This method wasmodified from the standard method used for testing thehardness of waxes in industry (American Society for Testingand Materials International [ASTM] D1321, 2015). Thehardness was presented in terms of the force (Newton) actingagainst the penetration of the needle into the wax matrix atthe definite distance (in mm.) at a fixed temperature. Theexperiment was performed in triplicate.2.7.5 Color measurementThe color of the wax was examined using MinoltaColor Reader CR-10. The CIE color parameters of L*, a* andb* were recorded.2.7.6 Density and specific gravity determinationThe density of the wax was determined using thedensity factor, i.e., a ratio by weight of wax to water of anexactly known volume. The wax was melted and poured intothe suppository mold. After solidified, the excessive waxabove the mold surface was removed. The solid wax in themold was taken out and weighed. The volume inside eachsuppository mold was determined using purified water. Thespecific gravity was calculated by dividing the density value511obtained by the density of water at same temperature. Theexperiment was performed in triplicate.2.7.7 Solubility determinationThe solubility of the extracted waxes in varioussolvents was determined using the method previouslydescribed by Yanagida et al. (2003a) with some modifications.The solvents used were hexane, dichloromethane, chloroform,ethanol and methanol. The excess amount of wax sample wasplaced in a well-closed flask containing a specific solvent.After the mixture was stirred using a small magnetic bar for12 hours at room temperature, it was centrifuged to obtainclear supernatant. The known volume of the supernatant wassampling and the solvent was evaporated. The solid residueof the wax was weighed. The experiment was performed intriplicate.3. Results and Discussion3.1 Identification of banana cultivarsAll banana samples collected from different originswere identified as Kluai Namwa (Musa acuminata X M.balbisiana (ABB group) cv. Pisang Awak. The samples werekept as a voucher specimen at Queen Sirikit Botanical Gardenin Chiang Mai. Kluai Namwa is a diploid cultivar and acommon edible banana widely grown in Northern Thailandas well as all parts of Thailand.3.2 Extraction of banana waxThe yield of the wax extracted from Kluai Namwa’sleaves depended on cultivating areas. They were 273.8 g/cm2, 212.6 g/cm2, 167.4 g/cm2 and 129.1 g/cm2, fromChiang Mai, Lampang, Pitsanulok and Tak provinces respectively. The yield value of BNS (273.8 g/cm2) was higher thanthe values reported by Freeman and Turner (1985) with thehighest one found in field-grown banana (230 g/cm2) whichwas 60% higher than those planted in a glasshouse. Yanagidaet al. (2003b) reported the yields of wax extracted frombanana leaves of different species on dried weight basis i.e.,Ito bashou (Japanese name) or M. liukiuensis (0.58%),kluai Pa or M.acuminata (1.05 %) and kluai Roi Wee or M.chiliocarpa (1.41%). Based on the percentage of moisturecontent reported, the maximum yield of 1.41% from M.chiliocarpa can be calculated as only 0.15 g/100 g of freshleaves which was significantly lower than the result of ourstudy (0.92 g/100 g of fresh leaves). Thus, Kluai Namwa’sleaves are the most abundant source of banana wax reporteduntil now. According to the higher yield percentage, the BNSand BNT were selected to be the samples for characterizationand physicochemical properties determination.In order to obtain purified, white-colored wax, theextracted wax was subjected to decolorization process usingactivated charcoal. After decolorization, the color of banana

512S. Charumanee et al. / Songklanakarin J. Sci. Technol. 39 (4), 509-516, 2017wax became whiter as shown in Figure 1. Although loss ofwax content was observed, its main composition as revealedby TLC analysis did not change as shown in Figure 2 andthe melting point and congealing point determined by DSCdid not altered (data not shown).3.3 Chemical compositions of banana wax3.3.1 Chemical compositions of by TLC and GCTLC chromatogram shown in Figure 3 demonstratedthat the major compositions of the wax extracted from bananaleaves and carnauba wax were similar. This was alsosupported by the fatty acid profiles obtained by gaschromatographic technique after saponification as shown inTable 1. The saturated fatty acids presented in both waxeswere behenic acid (C-22), lignoceric acid, palmitic acid andstearic acid. For unsaturated fatty acids; linolenic acid,linoleic acid and oleic acid were found predominantly inbanana wax. These results were in agreement with thosereported by Yanagida et al. (2003a), which demonstrated thatC-22 fatty acid was the most abundant component of bananawax.Figure 2. TLC chromatograms of wax from banana leaves: (A), (B)- BNT, before and after decolorization; (C), (D) BNS,before and after decolorization respectively.Figure 1. Epicuticular wax extracted from banana leaves, BNT andBNS; (A) before decolorization, (B) after decolorization.3.3.2 Acid number and saponification numberThe acid number and/or saponification number ismeaningful parameters providing information about thechemical functionality of the wax that contains carboxylicgroups. As shown in Table 2, the acid number and saponi-Figure 3. TLC chromatograms of (A) carnauba wax (B) BNT, (C)BNS.Table 1. Composition of wax from banana leaves and the reference waxes.% compositionCompoundsMyristic acid (C14:0)Palmitic acid (C16:0)Stearic acid (C18:0)Oleic acid (C18:1)Linoleic acid (C18:2)Linolenic acid (C18:3)Arachidic acid (C20:0)EPA(C20:5)Behenic acid (C22:0)Lignoceric acid (C24:0)BNTBNSCarnauba 2.56ND0.1850.1440.86Note: ND (undetected); EPA: Eicosapentaenoic acid.

S. Charumanee et al. / Songklanakarin J. Sci. Technol. 39 (4), 509-516, 2017513Table 2. Physicochemical parameters (mean SD, n 3) of wax from banana leaves and those ofreference waxes.Wax samplesAcid numberSaponification numberHardness (N)Specific gravityBNTBNSBeeswaxCarnauba waxParaffin wax1.68 0.26a3.58 0.92a17-24*2-7*NS81.66 4.39a94.72 5.18a87-104*78-95*NS39.17 4.36b29.30 3.42 b,c35.35 2.1638.68 3.47c25.24 7.47 b0.9266 0.0173d0.9025 0.0101d,e0.9543 0.0022d,e0.9373 0.0010e0.9308 0.0039eNote: * Reference values specified in PhEur, USP; NS –not specified in USP. Significant differenceswere tested at p 0.05.fication number of banana waxes, BNT and BNS weresignificantly different; however, they were in the range ofcarnauba wax’s values specified in Pharmacopeias. Thissupported the similarity in terms of the componentscontaining carboxylic acids of the two natural waxes.3.4 Characterization of the physicochemical properties ofbanana wax3.4.1 Melting point, congealing point and polymorphismThe DSC thermogram of banana wax obtained fromdifferent sources; BNS and BNT were compared to that ofcarnauba wax as shown in Figure 4. The melting point (peaktemperature) and congealing point of BNT were 81.38 Cand 73.81 C and those of BNS were 79.01 C and 74.11 Crespectively. They were not much different. Whereas carnaubawax exhibited the major melting peak at 78.98 C and thecongealing point peak at 73.91 C. They were more similar tothose of BNS. However, these properties are more vital forwax utilization than chemical compositions. Despite of somedifferences in their chemical composition observed, thecomparable melting points of both waxes revealed the identical internal strengths of wax crystals. The measured meltingpoint of carnauba wax was in agreement with that specifiedin USP30 NF30, i.e., 80-86 C. The extracted banana wax was ofhigh purity as evidenced by a single sharp and approachingsymmetrical melting peak, whereas the thermogram ofcarnauba wax showed two distinct melting peaks. Moreover,the thermogram of banana wax did not signify the existenceof polymorphism3.4.2 Examination of internal crystal structureThe X-ray powdered diffractograms in Figure 5illustrated the internal crystal structure of banana wax ascompared to carnauba wax. The sharp peaks demonstratedthat banana waxes as well as carnauba wax were in crystallinestate. It also indicated that the internal structure of bananawax and carnauba wax were similar which denoted by thesame peak positions of Bragg’s angle (2q) at of 21 , 23 and19 respectively. These observations supported the similarityFigure 4. DSC thermograms wax from banana waxes; BNT-upper,BNS-middle and carnauba wax-lower.

514S. Charumanee et al. / Songklanakarin J. Sci. Technol. 39 (4), 509-516, 2017of the two waxes as previously demonstrated by thecomposition and DSC studies.3.4.3 Examination of crystal modifications (crystal habits)The SEM micrograph in Figure 6 illustrated the crystalhabits of banana waxes obtained from different sources,BNT and BNS. They habits were quite similar exhibited theaggregated plate-liked crystals of varying sizes. Despite ofthe irregular habits, the internal structure exhibited highdegree of crystallinity as shown by X-ray diffractogram.The thin and uniform thickness of these plate-liked habitscontributes to sharp melting point peak as demonstrated byDSC study.3.4.4 Hardness measurementAccording to the modified method by using Textureanalyzer TA.XT2i, the hardness of the wax presented in termsof the resistant forces (Newton) against the penetration of theneedle into the solid wax was shown in Table 2. The hardnessof BNT and carnauba were insignificantly different, whereasBNS was softer than BNT, beeswax and carnauba wax thelower hardness value of BNS was significantly different fromthose waxes at p Color measurementFigure 5. X-ray powdered diffractograms of wax from bananaleaves: BNT, BNS and carnauba wax.The color of the wax was determined according toCIE (International Commission on Illumination, 1976) colorparameters (L*, a*, b*). The L* value represents thelightness; the maximum L* value of 100 represents pure whitecolor whereas zero value indicates black color. Each a* andb* represents two color components. The positive value ofa* indicates red color whereas the negative value representsfor green color. For b* value, its positive value representsyellow color and the negative one represents blue color.As shown in Table 3, paraffin wax had the highest L* valuefollowed by banana wax (non-decolorized) and carnauba waxrespectively. This demonstrated the intensity of white colorof waxes in descending order. As banana wax was whiterthan carnauba wax, the decolorization process might not benecessary for some cases of utilization. In addition, when a*and b* values are considered altogether, the color of bananawax can be summarized as white with greenish yellow color,whereas carnauba wax had white color with slightly redyellow color tone.3.4.6 Density and specific gravity determinationFigure 6. SEM micrograph of banana waxes, BNT- left and BNSright.The specific gravity of banana wax and those of thereference waxes were shown in Table 2. Although the methodused was adopted from density factor determination, theresults obtained from the reference, beeswax was in agreement with that specified in the reference book (Rowe, 2012).The measured values of the samples were then reliable.

S. Charumanee et al. / Songklanakarin J. Sci. Technol. 39 (4), 509-516, 2017515Table 3. CIE Color parameters (L*, a*, b*) of wax from banana leaves(before decolorization) and the reference waxes.Color parameters (L, a, b)(mean SD)Wax samplesBNTBNSBeeswaxCarnauba waxParaffin waxL (white-black)a (red-green)b (yellow-blue)88.2 0.5685.9 0.6385.7 1.7077.9 0.3493.4 1.14-2.8 0.19-3.8 0.40-2.4 0.29 1.7 0.16-1.7 0.15 29.0 0.87 23.5 0.71 2.7 0.48 1.7 0.16 0.5 0.26The banana waxes from different origins had significantlydifferent specific gravity and they were significantly lowerthan that of carnauba wax (p 0.05).3.4.7 Solubility determinationThe solubility of wax from banana leaves, BNT andBNS in various solvents was shown in Table 4. The wax wassoluble in chloroform, hexane, dichloromethane, ethyl alcoholand methyl alcohol in descending order. According to USPdescriptive terms of solubility, the solubility of banana waxin all solvents can be classified as slightly soluble i.e., 1001,000 parts of solvent are needed to dissolve one part of thewax (USP 35/NF30). However, the significant differences inthe solubility of BNT and BNS in hexane and methanol wereobserved at p 0.05.4. ConclusionsAll Kluai Namwa samples collected from differentplanting areas in Northern Thailand were Musa acuminata XM. balbisiana (ABB group) cv. Pisang Awak. The percentageyield and the physicochemical properties of the extractedwax depended on planting area. The sample which gave thehighest yield of wax was Kluai Namwa grown in Chiang Maiprovince (0.92 g/100 g of fresh leaves) whereas that grownTable 4. Solubility of wax from banana leaves in romethaneEthyl alcoholHexaneMethyl alcohol*(g/100 ml) (mean SD, n 3)BNTBNS0.64 0.180.34 0.030.15 0.030.50 0.11*0.10 0.02*0.69 0.100.38 0.080.14 0.040.80 0.05*0.15 0.01*Significant difference at p 0.05 (SPSS version 17).in Lampang province was more similar to carnauba wax.However, the reported yield of unpurified carnauba waxobtained from natural source was approximately five percent(Duke & duCellier, 1993). From extensive investigation byusing different characterized methods, we could confirm thatthe wax extracted from Kluai Namwa’s leaves grown inNorthern Thailand was similar to carnauba wax in terms ofchemical composition and physicochemical properties. Thiscould bring about the idea of replacing banana wax forcarnauba wax in pharmaceutical, cosmetic and the other waxutilizing areas.AcknowledgementsThe authors thank the National Research Council ofThailand (NRCT) for financial support. We also thankFaculty of Pharmacy, Chiang Mai University for providingfacilities and equipment to conduct the study.ReferencesAmerican Society for Testing and Materials International.(2015). Standard test method for needle penetrationof petroleum waxes, ASTM D1321-10. WestConshohocken, PA: Author. Retrieved from nal Commission on Illumination. (1976). Colorimetry- Part 4: 1976 L* a* b* colour space. Retrieved from ca id 485Debabandya, M., Sabyasachi, M., & Namrata, S. (2010).Banana and its by-product utilization: an overview.Journal of Scientific and Industrial Research, 69,323-329. Retrieved from uke, J. A., & duCellier, J. L. (1993). CRC Handbook ofalternative cash crops. London, England: CRC Press.Freeman, B., & Turner, D. W. (1985). The epicultcular waxeson the organs of different varieties of banana (Musaspp.) Differ in Form. Chemistry and Concentration.Australian Journal of Botany, 33(4), 393-408. doi:10.1071/bt.9850393

516S. Charumanee et al. / Songklanakarin J. Sci. Technol. 39 (4), 509-516, 2017Riederer, M., & Schreiber, L. (2001). Protecting against waterloss: Analysis of the barrier properties of plantcuticles. Journal of Experimental Botany, 52(363),2023-2032. Retrieved from, R. C., Sheskey, P. J., & Quinn, M. E. (2009). Handbookof pharmaceutical excipients (6th ed.) (pp.779-780).London, England: Pharmaceutical Press.Suzanne, S. N. (2010). Food analysis laboratory manual (pp.105-108). New York, NY: Springer.Sampath Kumar, K. P., Debjit, B., Duraivel, S., & Umadevi,M. (2013). Traditional and medicinal uses of banana.Journal of Pharmacognosy and Phytochemistry, 1(3),51-63. Retrieved from http://www.phytojournal.comUnited States Pharmacopeial Convention. (2011). USP35NF30, 2012: U.S. Pharmacopoeia National Formulary.Rockville, MD: Author.Yanagida, T., Shimizu, N., & Kimura, T. 2003. Properties ofwax extracted from banana leaves. Proceedings of theAmerican Society Agricultural Engineering (ASAE)Annual International Meeting. doi: 10.13031/2013.14121@2013Yanagida, T., Shimizu, N., & Kimura, T. (2005a). Extractionof wax and functional compounds from fresh and drybanana leaves. Japan Journal of Food Engineering,6(1), 79-87. doi: 10.11301/jsfe200.6.79Yanagida, T., Shimizu, N., & Kimura, T. (2005b). Extractionof wax from banana as an alternative way of utilizingagricultural residues. Japan Journal of Food Engineering. 6(1), 29-35. doi: 10.11301/jsfe200.6.29

The fatty acid composition and the physicochemical properties of the wax were similar to those of carnauba wax. It could be suggested that the banana wax could be used as a replacement for carnauba wax in various utilizing areas. Keywords: epicuticular wax, banana wax, Kluai Namwa, Musa spp. carnauba wax Songklanakarin J. Sci. Technol.

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