applied sciences

Article Evaluation of Color Change and Biodeterioration Resistance of Gewang ( utan Lamk.) Wood

Dodi Nandika 1,*, Wayan Darmawan 1, Lina Karlinasari 1 , Yusuf Sudo Hadi 1 , Imam Busyra Abdillah 1 and Salim Hiziroglu 2

1 Forest Products Department, IPB University (Bogor Agricultural University), Kampus IPB, Darmaga, Bogor 16680, ; [email protected] (W.D.); [email protected] (L.K.); [email protected] (Y.S.H.); [email protected] (I.B.A.) 2 Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK 74078, USA; [email protected] * Correspondence: [email protected]

 Received: 28 September 2020; Accepted: 19 October 2020; Published: 26 October 2020 

Abstract: Gewang (Corypha utan Lamk.) is one of the endemic palm species which has been used as a building material for many years in Indonesia. The objective of this study was to enhance the overall resistance of gewang wood to biological deterioration by using smoke treatment. Samples taken from different parts of the trunks, namely bottom, middle, and upper parts in a longitudinal direction and outer and inner parts in a transversal direction, were exposed to the smoking process. Discoloration, dry-wood termite (Cryptotemes cynocephalus) and fungi (Schizophyllum commune) resistance of smoked samples were determined according to the Indonesian standard. Based on the findings in this work, discoloration of smoked specimens was more prominent than that of the unsmoked samples. Overall termite and decay resistance of smoked samples were enhanced and higher than those of unsmoked samples without any influence of longitudinal and transversal orientations within the trunks. It appears that smoking can be considered as a potential method to improve decay and termite resistances of gewang wood.

Keywords: gewang palm wood; decay fungus; dry-wood termite damage; smoke treatment

1. Introduction Log production for the Indonesian wood industry reached 47.9 million m3, with 85% of production being from plantation forests in 2018 [1]. The need for timber supply in the country significantly increased by 4 million m3/year, causing a serious shortage of high-quality timber in the last four years. This requires multiple approaches, including exploration of “new timber” resources, particularly from endemic species. One of the endemic tree species that grow in Nusa Tenggara Province is gewang (Corypha utan Lamk.) [2,3]. At a mature stage, gewang trunk could have 2.8 tons of biomass with an average density of 0.50 g cm 3. In terms of volume, such amount of lignocellulose material has a great potential as a · − source of building materials. People in East Nusa Tenggara Province have been using gewang wood as building materials for a long time. The outer part of the gewang trunk is also used for flooring to replace wooden parquet [4]. However, the inner part of the gewang trunk has significantly lower density, as well as modulus of elasticity (MOE) and modulus of rupture (MOR), compared to those of the middle and outer parts [5]. This leads to ineffective utilization of the inner part of gewang trunk as a building material. The inner part of gewang trunk is also very susceptible to biodeterioration [6]. It was reported that the damage due to biodeterioration in Indonesia, especially termite attacks, reaches approximately USD 1 billion on wood-based material in buildings [7]. It is expected that this value

Appl. Sci. 2020, 10, 7501; doi:10.3390/app10217501 www.mdpi.com/journal/applsci Appl. Sci. 2020, 10, 7501 2 of 12 will increase in the future if non-durable timber continues to be used in the building constructions without any particular treatment to increase their overall resistance. Appl. Sci. 2020, 10, x FOR PEER REVIEW 2 of 12 One of the most effective treatments to improve the durability of wood is smoke treatment. Suchvalue treatment will increase has long in been the usedfuture in if the non-durable food industry timber to continues extend product to be used shelf in life, the provide building flavor, and changeconstructions the color without of theany productparticular [ 8treatm]. Smokeent to fromincrease wood their contains overall resistance. a large number of polycyclic aromatic hydrocarbons,One of the most whicheffective are treatments predominantly to improve phenols, the durability aldehydes, of wood ketones, is smoke organic treatment. acids, Such alcohols, esters,treatment hydrocarbons, has long and been various used in heterocyclic the food industry compounds to extend [9]. Hadiproduct et al.shelf [10 life,,11] provide determined flavor, solid and wood and glued-laminatedchange the color oflumber the product specimens [8]. Smoke exposed from wood to wood contains smoke a large are number more resistantof polycyclic to subterraneanaromatic termitehydrocarbons, attack than which control are specimens, predominantly and phenols, two weeks alde exposurehydes, ketones, time toorganic smoke acids, increases alcohols, the esters, resistance hydrocarbons, and various heterocyclic compounds [9]. Hadi et al. [10,11] determined solid wood of sengon (Falcataria moluccana), manii (Maesopsis eminii) and mangium (Acacia mangium) also as a and glued-laminated lumber specimens exposed to wood smoke are more resistant to subterranean resulttermite of smoke attack treatment than control resistance specimens, level and of two the week samples exposure increased time to one smoke class increases based on the the resistance Indonesian standard.of sengon However, (Falcataria longer moluccana smoking), manii periods (Maesopsis are required eminii) and to reach mangium the higher (Acacia classmangium (or) very also resistant)as a levelresult of resistance. of smoke Smoke treatment treatment resistance with level a longer of the sample period increased lead to color one changesclass based in sengonon the Indonesian and mangium woodstandard. compared However, with untreated longer smoking wood periods [12]. There are requir is veryed littleto reach or nothe informationhigher class (or on very color resistant) change and biodeteriorationlevel of resistance. resistance Smoke of smokedtreatment gewang with a woodlonger asperiod a function lead to of color smoke changes treatment. in sengon and Therefore,mangium wood the maincompared objective with untrea of thisted study wood was[12]. toThere determine is very little the or color no information change and on resistancecolor of smokedchange gewangand biodeterioration wood specimens resistance from of smoked different gewang parts wood of theas a trunk,function longitudinally of smoke treatment. as well as transversally,Therefore, to dry-wood the main termite objective and of decaythis study fungus was attacksto determine when the they color were change exposed and resistance for three of weeks smoked gewang wood specimens from different parts of the trunk, longitudinally as well as to function smoke treatment. The resistance of the control and smoked treated wood specimens were transversally, to dry-wood termite and decay fungus attacks when they were exposed for three weeks also compared.to function smoke treatment. The resistance of the control and smoked treated wood specimens were also compared. 2. Materials and Methods Three2. Materials gewang and (MethodsC. utan) logs, 1.30 m in length and 30–40 cm in diameter, were obtained from Kupang, EastThree Nusa gewang Tenggara, (C. utan Indonesia.) logs, 1.30 m Each in length log had and a longitudinal30–40 cm in diameter, orientation were of obtained the trunk, from namely bottomKupang, part (B), East middle Nusa Tenggara, part (M), Indonesia. and upper Each part log (U).had a The longitudinal logs were orientation cut from of two the gewangtrunk, namely trees that had grownbottom inpart a lowland(B), middle community part (M), and forest upper at part the age(U). ofThe about logs were 30 years cut from (mature two gewang tree). After trees reachingthat air-dryhad condition, grown in a three lowland disks community with a thickness forest at the of age 15 cmof about were 30 then years prepared (mature tree). from After each reaching log, namely Bf, Bt,air-dry and Bd condition, (represent three bottom disks with part); a thickness Mf, Mt, of and 15 cm Md were (represent then prepared middle from part); each and log, Uf,namely Ut, andBf, Ud Bt, and Bd (represent bottom part); Mf, Mt, and Md (represent middle part); and Uf, Ut, and Ud (represent upper part) as shown in Figure1. (represent upper part) as shown in Figure 1.

Where: • Bf, Mf, Uf = Disks from bottom part, middle part, and upper part of gewang trunk as a source of wood samples for decay fungal test • Bt, Mt, Ut = Disks from bottom part, middle part, and upper part of gewang trunk as a source of wood samples for termite test • Bd, Md, Ud = Disks from bottom part, middle part, and upper part of gewang trunk as a source of wood samples for density test

Figure 1. Cutting pattern of gewang log to prepare wood specimens representing bottom part (B), Figure 1. Cutting pattern of gewang log to prepare wood specimens representing bottom part (B), middle part (M), and upper part (U) of the trunk. middle part (M), and upper part (U) of the trunk. Appl. Sci. 2020, 10, 7501 3 of 12 Appl. Sci. 2020, 10, x FOR PEER REVIEW 3 of 12

Bf, Mf,Mf, andand Uf Uf disks disks were were prepared prepared for for decay decay resistance resistance to wood to wood samples; samples; Bt, Mt, Bt, andMt, Utand disks Ut disks were preparedwere prepared for termite for termite resistance resistance wood samples;wood samples; and Bd, and Md, Bd, and Md, Ud and disks Ud were disks prepared were prepared for density for testdensity respectively. test respectively. Each disk Each was processeddisk was forprocesse flat-shownd for lumbers,flat-shown then lumbers, cut into then wood cut specimens into wood of 2.5specimens cm by 2.5 of cm2.5 incm a by cross-section 2.5 cm in a alongcross-section 1 m of the along trunk 1 m length of the (Figure trunk length2). (Figure 2).

Outer part

Inner part

1, 2, 3, …, 6 = wood specimens (2.5 cm x 2.5 cm x 15 cm) that were prepared for wood samples of particular tests.

Figure 2. Cutting pattern of each gewang discs to prepar preparee wood sample, representing outer part and inner partpart ofof gewanggewang trunk.trunk.

2.1. Smoking Procedure Kesambi ((SchleicheraSchleichera oleosaoleosa)) wood wood was was pyrolyzed pyrolyzed to to produce produce charcoal, charcoal, and and the the smoke smoke released released as a byproductas a byproduct was used was forused the for smoking the smoking process, process, for three for weeks. three The weeks. smoke The produced smoke fromproduced pyrolyzed from tankpyrolyzed flew totank another flew to tank another for catching tank for thecatching tar and the reducingtar and reducing the temperature the temperature and then and flew then to flew the smokingto the smoking chamber. chamber. The position The position of wood samplesof wood insamples the chamber in the was chamber set up randomly.was set up The randomly. temperature The insidetemperature the chamber inside the during chamber the smoking during the process smoking ranged process from ranged 18 to 36 from◦C, and18 to fluctuated 36 °C, and in fluctuated line with thein line day with and nightthe day ambient and night temperature. ambient temperature. After completion After of completion the smoking of process,the smoking the samples process, then the underwentsamples then conditioning underwent forconditioning 2 weeks under for 2 roomweeks temperature under room oftemperature 26 ◦C (min of 20.1, 26 °C max (min 31.1 20.1,◦C) max and average31.1 °C) relativeand average humidity relative of 83.4% humidity (range, 62.5–95.6%).of 83.4% (range, Five replications62.5–95.6%). were Five considered replications for were each typeconsidered of sample. for each type of sample.

2.2. Density Measurement of The Samples Wood densitydensity was was determined determined through through measuring measuring volume volume of wood of specimenwood specimen at air-dry at condition air-dry (Vcondition1), and oven-dry(V1), and weightoven-dry (W weight1), and (W the1), wood and the density wood was density calculated was calculated as follows: as follows:

  Density (g · cm3 ) = W /V (1) Density g cm− = W /1V 1 (1) · 1 1

2.3. Discoloration Measurement of The Samples The CIELabCIELab method method was was employed employed to determineto determin thee discoloration the discoloration of the samplesof the samples due to smoking due to influence.smoking influence. This method This involved method directlyinvolved measuring directly measuring the values the of L*, values a*, and of b*L*, from a*, and a photograph. b* from a Thephotograph. photo was The obtained photo was using obtained a scanner using machine a scanne (CanoScanr machine 4400F, (CanoScan from Canon, 4400F, Japan) from Canon, then analyzed Japan) withthen analyzed the Adobe with Photoshop the Adobe CS5 Photoshop application CS5 [13 applicat,14]. L*ion indicated [13,14]. L* lightness, indicated with lightness, a value with of 0 a to value 100 (blackof 0 to to100 white); (black a* to indicatedwhite); a* colors indicated from colors green fr toom red, green with to+ red,a* from with 0 +a* to 80 from corresponding 0 to 80 corresponding to red and a* from 80 to 0 corresponding to green; and b* indicated color from blue to yellow, with +b* from 0 −to red and− −a* from −80 to 0 corresponding to green; and b* indicated color from blue to yellow, with to 70 corresponding to yellow and b* from 70 to 0 corresponding to blue [15]. Each sample was +b* from 0 to 70 corresponding to −yellow and− −b* from −70 to 0 corresponding to blue [15]. Each sample was assessed at five points, and the average values were used for the analysis. The color change (ΔE) was calculated considering CIELab method [16], using the following equation:

ΔE = [(∆L*)2+ (∆a*)2+ (∆b*)2] (2) Appl. Sci. 2020, 10, 7501 4 of 12 assessed at five points, and the average values were used for the analysis. The color change (∆E) was calculated considering CIELab method [16], using the following equation:

qh ∆E = (∆L )2+ (∆a )2+ (∆b )2] (2) ∗ ∗ ∗ where, ∆E: color change; ∆L*: difference in L* values between compared samples; ∆a*: difference in a* values between compared samples; ∆b*: difference in b* values between compared samples. The color change can be classified as shown in Table1.

Table 1. Color change class [16,17].

Class Color Difference Color Change Effect 1 ∆E < 0.2 Invisible changes 2 0.2 < ∆E < 2.0 Very small changes 3 2.0 < ∆E < 3.0 Small changes (color changes visible by high-quality filter) 4 3.0 < ∆E < 6.0 Medium (color changes visible by medium-quality filter) 5 6.0 < ∆E < 12 Big (distinct color changes) 6 ∆E > 12 Different color

2.4. Dry-Wood Termites Resistance Test Specimens with a 2.5 cm by 2.5 cm cross section and measuring 5 cm in the longitudinal direction were prepared according to Indonesian National Standard 7207-2014 [18]. This standard has been recognized and improved by researchers from various countries in evaluating the resistance of wood against termite as well as fungi attacks including in Japan [19]. The individual sample was placed in the center of a glass tube (3 cm high by 1.8 cm in diameter), and 50 dry-wood termite workers (Cryptotermes cynocephalus Light) were introduced into the glass tube. The samples were then placed in a dark room for 12 weeks. At the end of the experiment, wood specimen weight loss and termite mortality percentage were determined with five replications. The wood resistance was classified according to the Indonesian National Standard described in Table2[ 18]. The weight loss and termite mortality percentage were determined using the following equations:

WL (%) = (W W )/W 100% (3) b− d b × Mortality (%) = (T T )/T 100% (4) b− d b × where:

WL: weight loss percentage of wood specimen.

Wb: gewang wood weight prior to the test at oven-dried condition. Wd: gewang wood weight after the test at oven-dried condition. Tb: the number of live termites before the test. Td: the number of live termites after the test.

Table 2. Classification of wood resistance against dry-wood termites.

Class Sample Condition Weight Loss (%) I Very resistant <2.0 II Resistant 2.0–4.3 III Moderate 4.4–8.1 IV Poor 8.2–28.1 V Very poor >28.1 Appl. Sci. 2020, 10, 7501 5 of 12

2.5. Fungus Decay Test Wood decaying fungus Schizophyllum commune was inoculated in the glass boxes using potato dextrose agar media for 10 days to allow the fungus grew adequately [20,21]. In the next step, wood samples with a cross section of 2.5 cm 1.5 cm and 5 cm in the longitudinal direction were placed × on the fungus isolate in the glass box for the test [18]. After 10 weeks of inoculation in an incubator at a temperature ranging from 22 to 28 ◦C and 80 to 90 percent relative humidity, wood weight loss percentage was determined. The average MC of the wood samples prior to the test was 12 3% and ± weight loss percentage was determined using the equation (3). The wood resistance was classified according to the Indonesian National Standard [18] described in Table3.

Table 3. Classification of wood resistance against fungal decay.

Class Sample Condition Weight Loss (%) I Very resistant <0.5 II Resistant 0.5–4.9 III Moderate 5.0–9.9 IV Poor 10.0–30.0 V Very poor >30.0

2.6. Analysis of the Data A 3 by 2 by 2 factorial completely randomized design was used to analyze the data where the first factor (A) is the longitudinal direction (bottom, middle, and upper part); second factor (B) is the transversal direction (inner and outer part); and third factor (C) is the treatment (unsmoked and smoked). A linear equation of mathematical model as follows:

Yijkl = µ + Aj + Bk + Cl + (AB)jk + (AC)jl + (BC)kl + (ABC)jkl + εijkl (5) where:

Yijkl: The observed value of the experimental unit i from the combination of jkl with factor A at the level to j, factor B at the level to k, and factor C at the level to l. µ: Grand mean parameter.

Aj: The influence of factor longitudinal direction at level j (j = 1, 2, 3). Bk: The influence of factor transversal direction at level k (k = 1, 2). Cl: The influence of factor treatment at level l (l = 1, 2). ABjk: The influence interaction between factor A at the level j and factor B at level to k. ACjl: The influence interaction between factor A at the level j and factor C at level to l. BCkl: The influence interaction between factor B at the level k and factor C at level to l. ABCjkl: The influence interaction between factor A at the level j, factor B at level k, and factor C at the level l.

εijkl: The effect of the error that arises the i-th from experiment combination in factor A at level j, factor B at level k, and factor C at level l. Duncan’s multiple range tests were used for further analysis if a factor was significantly different at p < 0.05.

3. Results and Discussion

3.1. Density of Gewang Wood It seems that smoke treatment did not affect the density of the samples because the precipitated smoke on the wood surface was very small which was not sufficient to influence the density increment [22]. The density values of unsmoked samples are illustrated in Figure3. Appl. Sci. 2020, 10, 7501 6 of 12 Appl. Sci. 2020, 10, x FOR PEER REVIEW 6 of 12

Appl. Sci. 2020, 10, x FOR PEER REVIEW 6 of 12 1 1 0.8

) 0.8 -3 ) cm -3

∙ 0.6 cm

∙ 0.6 Inner part Inner part 0.4 Outer part 0.4 Outer part Density (g

0.2Density (g 0.2

0 0 Bottom part Middle part Upper part Bottom part Middle part Upper part Figure 3. Density of unsmoked samples. Figure 3. Density of unsmoked samples. Figure 3. Density of unsmoked samples. The summary of variance analysis regarding the effect of longitudinal and transversal parts on The summary of variance analysis regarding the effect of longitudinal and transversal parts on densityThe of thesummary samples of isvariance shown analysis in Table regarding4. It could the be effect mentioned of longitudinal that the and density transversal was significantly parts on density of the samples is shown in Table 4. It could be mentioned that the density was significantly influenceddensity of by the the samples longitudinal is shown and in transversalTable 4. It co directions,uld be mentioned and the that interaction the density between was significantly them was not influenced by the longitudinal and transversal directions, and the interaction between them was not significant.influenced It by appears the longitudinal that outer and part transversal (average di 0.69rections,0.09 and g cmthe interact3) hadion a higher between density them comparedwas not -3 − significant.significant. It Itappears appears that that outer outer part part (average (average3 0.690.69 ±± 0.09 g·cmg·cm· -3)) hadhad a a higher higher density density compared compared to to to the inner part (average 0.36 0.08 g cm− ) as shown in Figure3. A decrease in the density from the inner part (average 0.36 ± 0.08± g·cm-3-3·) as shown in Figure 3. A decrease in the density from bottom bottomthe inner towards part (average the upper 0.36 part ± 0.08 could g·cm also) as be shown responsible in Figure for 3.such A decrease findings. in the This density could from be due bottom to the towardstowards the the upper upper part part could could alsoalso bebe responsiblresponsible for suchsuch findings.findings. ThisThis could could be be due due to tothe the proportion of vascular bundles within the gewang trunk as well as the other palmae species which is proportionproportion of ofvascular vascular bundles bundles within within the the gewang gewang trunk as wellwell as as the the other other palmae palmae species species which which is is decreasing from the bottom part to the upper part of the trunk, and the same phenomenon was also decreasingdecreasing from from the the bottom bottom part part to to the the upper upper partpart of the trunk, andand the the same same phenomenon phenomenon was was also also observed from the outer part to the inner part, as described in Figure4[ 23]. The lower proportion of observedobserved from from the the outer outer part part to to the the inner inner part, part, asas described inin FigureFigure 4 4 [23]. [23]. The The lower lower proportion proportion of of the vascular bundles caused the lower density of the wood [5]. This finding was in line with Subyakto thethe vascular vascular bundles bundles caused caused the the lower lower density density ofof thethe wood [5].[5]. ThisThis finding finding was was in in line line with with Subyakto Subyakto et al. [4] who found that the outer part of gewang trunk has a higher density compared that of the et al.et al.[4] [4] who who found found that that the the outer outer part part ofof gewanggewang trunk hashas aa higherhigher density density compared compared that that of ofthe the inner part of the trunk. innerinner part part of ofthe the trunk. trunk. Outer Outer

Inner Inner

Bottom Middle Upper

Bottom Figure 4. Macroscopic imagesMiddle (20×) of gewang wood. Upper Figure 4. Macroscopic images (20 ) of gewang wood. × Figure 4. Macroscopic images (20×) of gewang wood.

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Table 4. Variance analysis summary of density, termite mortality, weight loss on termite test, and Tableweight 4. Variance loss on fungal analysis test. summary of density, termite mortality, weight loss on termite test, and weight loss on fungal test. Termite Parameter Density WL Termite WL Fungi Parameter Density TermiteMortality Mortality WL Termite WL Fungi Longitudinal Part (A) * Ns ** ** Longitudinal Part (A) * Ns ** ** TransversalTransversal Part Part (B) (B) ** ** * * ** ** ** ** TreatmentTreatment (C) (C) - - ** ** ** ** ** ** A A B× B Ns Ns Ns Ns Ns Ns Ns Ns × A A C× C - - Ns Ns Ns Ns ** ** × B C - * ** ** ×B × C - * ** ** A B C - Ns * Ns ×A × ×B × C - Ns * Ns ** Highly** Highly significant significant diff erencedifference (p (0.01);p ≤ 0.01); * = significantly * = significantly difference difference (p 0.05); (p ≤ 0.05); Ns = Nsnot = significantly not significantly different (p 0.05). ≤ ≤ ≤different (p ≤ 0.05). 3.2. Discoloration of the Samples 3.2. Discoloration of the Samples TheThe wood wood color color was was indicated indicated byby valuesvalues of L* ( (lightness,lightness, black black to to white), white), a* a* (redness, (redness, green green to to red),red), b* b* (yellowness, (yellowness, blue blue to yellow),to yellow), and and∆E Δ forE for the the color color change, change, which which is shownis shown in Tablein Table5. The 5. The color ofcolor the specimens of the specimens was shown was shown in Figure in Figure5. 5.

TableTable 5. 5.Color Color ofof unsmokedunsmoked and sm smokedoked wood wood specimens. specimens.

TreatmentTreatment L* L* a* a* b* b* ∆E ΔE UnsmokedUnsmoked 50.5 (4.7) 50.5 (4.7) 8.3 8.3(2.5) (2.5) 22.922.9 (1.5) (1.5) Smoked Smoked 25.0 (2.0) 25.0 (2.0) 6.5 6.5(1.8) (1.8) 8.4 8.4 (1.5) (1.5) 29.7 (3.7) 29.7 (3.7) t-test t-test 0.00 ** 0.00 ** 0.34 0.34 ns ns 0.00 0.00 ** ** ** Highly** Highly significant significant difference difference (p 0.01); (p ≤ ns0.01);= not ns significantly = not sign diificantlyfferent (pdifferent0.05), (numbers(p ≤ 0.05), in (numbers parentheses in are standard deviation values). ≤ ≤ parentheses are standard deviation values).

Unsmoked Smoked

●#937252* ●#49382f* color description: color description: mostly desaturated dark orange very dark desaturated orange

FigureFigure 5. 5.Discoloration Discoloration of of unsmoked unsmoked andand smokedsmoked specimens. * *Remarks: Remarks: the the color color description description defined defined byby ColorHexa ColorHexa [24 [24].].

BasedBased on on the the results results displayed displayed inin TableTable5 5,, unsmokedunsmoked andand smoked samples samples were were significantly significantly diffdifferenterent from from each each other other in in terms terms of of theirtheir L*L* andand b*b* values.values. Smoke Smoke treatment treatment resulted resulted in insamples samples withwith a darkera darker color, color, as as indicated indicated by by an an L*L* valuevalue of smoked wood wood that that decreased decreased to to become become half half of ofthe the valuevalue of of the the unsmoked unsmoked wood. wood. SmokeSmoke treatmenttreatment chan changedged the the b* b* value value blue blue to to yellow yellow color, color, and and the the averageaverage values values declined declined or or became became more more blueblue color. In terms terms of of a* a* value value green green to to red red color, color, unsmoked unsmoked and smoked were not significantly different, as indicated by the value changed was a small number. and smoked were not significantly different, as indicated by the value changed was a small number. These findings revealed that smoke treatment for samples resulted in different colors (ΔE more than These findings revealed that smoke treatment for samples resulted in different colors (∆E more than 12) compared with unsmoked samples. In a previous work, similar results for mangium and sengon 12) compared with unsmoked samples. In a previous work, similar results for mangium and sengon smoked woods were determined [12,22], Ishiguri et al. [25] also determined that wood samples smoked woods were determined [12,22], Ishiguri et al. [25] also determined that wood samples treated with smoke for 200 h showed significant discoloration having deeper color those of exposed of smoke for 100 h. Appl. Sci. 2020, 10, 7501 8 of 12

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3.3.treated Resistance with of smoke the Samples for 200 to hDry-Wood showed significant Termite discoloration having deeper color those of exposed ofTermite smoke for mortalities 100 h. of treated specimens are displayed in Table6, and analysis of variance is also presented in Table4. Regarding to analysis of variance, the factors of transversal part (direction), 3.3. Resistance of the Samples to Dry-Wood Termite treatment, and interaction of the both factors significantly affected termite mortality (p < 0.05). In terms of transversalTermite direction, mortalities the of outer treated part spec hadimens higher are displayed mortality in than Table the 6,inner and analysis part, because of variance the outeris also part hadpresented a much higher in Table density 4. Regarding than the to inneranalysis part. of vari Suchance, a finding the factors was of in transversal line with Hadi part (direction), et al. [26] who treatment, and interaction of the both factors significantly affected termite mortality (p < 0.05). In 3 found that untreated wood with a lower density (sugi, Cryptomeria japonica, with density 0.34 g cm− ) terms of transversal direction, the outer part had higher mortality than the inner part, because the· had a lower dry-wood termite mortality compared to higher density wood (mindi, Melia azedarach, outer part had a much higher density than the inner part. Such a finding was in line with Hadi et al. with density 0.43 g cm 3). [26] who found ·that− untreated wood with a lower density (sugi, Cryptomeria japonica, with density 0.34 g·cm−3) had a lower dry-wood termite mortality compared to higher density wood (mindi, Melia Table 6. Mortality rate of dry-wood termite. azedarach, with density 0.43 g·cm−3). Inner Part (%) Outer Part (%) Trunk Part Table 6. Mortality rate of dry-wood termite. Unsmoked Smoked Unsmoked Smoked Inner Part (%) Outer Part (%) TrunkBottom part part 66.2 (10.0) 100 (0) 71.2 (3.9) 100 (0) Middle partUnsmoked 65.2 (10.7) Smoked 100 (0) 70.4Unsmoked (1.7) 100 (0)Smoked BottomUpper part part 66.2 63.6 (10.0) (5.2) 100 (0) 68.4 71.2 (3.6) (3.9) 100 (0) 100 (0) Middle part Numbers 65.2 (10.7) in parentheses are 100 standard (0) deviation values.70.4 (1.7) 100 (0) Upper part 63.6 (5.2) 100 (0) 68.4 (3.6) 100 (0) Numbers in parentheses are standard deviation values. Regarding the smoke treatment of the samples, termite mortality of control samples ranged from 63.6 to 71.2%,Regarding while the smoked smoke specimenstreatment of had the completesamples, te termitermite mortality mortality. of control In the casesamples of kesambi ranged from samples exposed63.6 to to 71.2%, smoke, while acetic smoked acid was specimens produced, had followed complete by termite phenol, mortality. ketones, In amines the case and of benzene, kesambi and suchsamples chemicals exposed created to asmoke, toxic environmentacetic acid was for produced, the termite followed [22]. These by phenol, chemicals ketones, also could amines precipitate and on thebenzene, samples, and resultingsuch chemicals in their created discoloration. a toxic enviro Suchnment a conclusion for the termite was [22]. observed These inchemicals two of thealso past studiescould carried precipitate out Hadi on the et samples, al. [27,28 resulting]. Abdillah in their et al. discoloration. [29] found thatSuch wood a conclusion smoke couldwas observed penetrate in the two of the past studies carried out Hadi et al. [27,28]. Abdillah et al. [29] found that wood smoke low and medium density wood (jabon wood and pine wood) until 0.69 and 0.74 mm, respectively, could penetrate the low and medium density wood (jabon wood and pine wood) until 0.69 and 0.74 in smoking treatment. mm, respectively, in smoking treatment. WeightWeight loss loss percentage percentage value value and and resistance resistance class class as wellas well as variance as variance analysis analysis of dry-wood of dry-wood termite are displayedtermite are indisplayed Figure6 inand Figure Table 64 and, respectively. Table 4, resp Theectively. longitudinal The longitudinal part, transversal part, transversal part, treatment, part, andtreatment, interaction and of theinteraction three factors of the significantlythree factors sign influencedificantly the influenced percentage the percentage wood weight wood loss weight (p < 0.05). In termsloss (p of < longitudinal0.05). In terms direction, of longitudinal the wood direction, from the bottom wood part from had bottom a lowest part had weight a lowest loss weight and the loss values increasedand the toward values increased upper parts. toward Such upper results parts. were Such in re linesults with were the in termiteline with mortality the termite and mortality the correlation and couldthe be correlation explained could by the be explained fact that theby the highest fact that termite the highest mortality termite would mortality have would the lowest have the wood lowest weight loss,wood and viceweight versa. loss, and vice versa.

25

20

15 Bottom 10 Middle

Weight loss (%) Upper 5

0 Unsmoked Smoked Unsmoked Smoked

Inner part Outer part

Figure 6. Wood weight loss after 12 weeks exposed to dry-wood termite. Appl. Sci. 2020, 10, 7501 9 of 12

Regarding to the transversal direction, the samples taken from the inner part of trunks had a higher weight loss compared to those taken from the outer part. In other words, the inner part was more susceptible to dry-wood termite attack, because the inner part had a lower density than the outer part. These findings were in line with Arango et al. [30] who analyzed six hardwood species, and found a significant inverse association between percentage of mass lost and specific gravity; in other words, wood with a higher specific gravity has more resistance to Reticulitermes flavipes Kollar termites. Another factor of treatment, exposed smoke on the inner part could enhance the resistance of gewang wood to dry-wood termite attack, as indicated by smoked wood having a much lower percentage wood weight loss compared to unsmoked samples. Furthermore, when considering the resistance classes in Table7, unsmoked samples on the inner part of gewang wood belonged to class IV (poor resistance to dry-wood termite attack), but the smoked wood of inner part belonged to class III (moderately resistant). In other words, the smoked gewang wood of inner part had one class higher than unsmoked samples. Meanwhile, the exposed smoke did not affect the durability of the outer part of gewang wood, since this part already had moderate resistance to dry-wood termite attack (class III, the same class as the inner part of the smoked wood), and it had the utmost level of resistance against termite attack. This finding was in line with the findings of previous studies determined that smoke treatment could enhance the resistant of low density wood to be equal to high density smoked wood at the highest level of termite resistance in particular circumstances [12,27,28].

Table 7. Resistance class after exposed to dry-wood termite.

Inner Part Outer Part Trunk Part Unsmoked Smoked Unsmoked Smoked Bottom IV III III III Middle IV III III III Upper IV III III III

3.4. Fungal Decay Assay Results The weight loss value and analysis of variance of fungal test are shown in Figure7 and Table4. The percentage weight loss of the fungus test ranged from 4.86 to 18.12% for unsmoked samples. Smoked samples had a lower weight loss than those unsmoked specimens. Analysis of variance revealed that each factor had a highly significantly different (p < 0.01), but there was no interaction between the longitudinal with transversal part of the gewang trunk and three factors. Regarding the resistance class in Table8, smoke treatment increased the resistance to fungus decay of the samples taken from the inner and outer part of the trunk. Smoking process enhanced the resistance of the samples class to be two classes higher. Additionally, smoke treatment on the samples taken from outer and inner parts had the same resistance class, according to SNI 2014 [18]. It is known that smoke has toxic or carcinogenic compounds such as the polycyclic aromatic hydrocarbons (PAH) group that can cause permanent damage to living organisms [31,32]. The phenol group, as a constituent of smoke, can be used as a wood preservative [11,12,33]. These components were not only increasing termite mortality [33], but also can be considered as an environmentally friendly approach to enhance fungus resistance of the samples [34].

Table 8. Wood resistance class after exposure to decay fungi.

Inner Part Outer Part Trunk Part Unsmoked Smoked Unsmoked Smoked Bottom IV II II II Middle IV II III II Upper IV II III II Appl. Sci. 2020, 10, 7501 10 of 12 Appl. Sci. 2020, 10, x FOR PEER REVIEW 10 of 12

25

20

15 Bottom 10 Middle

Weight loss (%) Upper 5

0 Control Smoked Control Smoked

Inner part Outer part

FigureFigure 7. 7. WoodWood weight weight loss loss after after 10 10 weeks weeks exposed exposed to to decay decay fungus. fungus.

4. ConclusionsIt is known that smoke has toxic or carcinogenic compounds such as the polycyclic aromatic hydrocarbonsBased on (PAH) our findings, group that the can following cause permanent conclusions damage can be drawn:to living organisms [31,32]. The phenol group, as a constituent of smoke, can be used as a wood preservative [11,12,33]. These components werea. notThe only inner increasing part and termite upper partmortality of wood [33], from but thealso gewang can be trunkconsidered had lower as an densitiesenvironmentally than the friendlyouter approach part and to enhance bottom part,fungus respectively. resistance of the samples [34]. b. The color of smoked gewang wood differed in color from unsmoked samples. c. Unsmoked samplesTable of 8. gewangWood resistance wood fromclass after the innerexposure part to were decay more fungi. susceptible to attack by dry-wood termite and fungal attacks than the outer part. Inner Part Outer Part d. TrunkSmoke Part treatment was very effective for the inner part, enhancing resistance to dry-wood termite Unsmoked Smoked Unsmoked Smoked and fungal attacks. Bottom IV II II II Middle IV II III II AuthorUpper Contributions: Conceptualization,IV D.N., W.D.; DataII Curation, I.B.A., W.D.,III L.K.; Investigation Resources,II Y.S.H. and S.H.; Writing-review and editing, D.N., Y.S.H., S.H., I.B.A. All authors have read and agreed to the published version of the manuscript. 4. Conclusions Funding: Indonesian Ministry of Education and Culture through Priority Basic Research of the University Grant (PenelitianBased Dasaron our Unggulan findings, Perguruan the following Tinggi) conclusions Year 2020. can be drawn: Acknowledgments: This research was a part of Basic Research Year 2020 granted by the Deputy of Research and a.Development The inner Strengthening, part and upper Ministry part of of Research wood andfrom Technology, the gewang the trunk Republic had of Indonesia.lower densities than the outer part and bottom part, respectively. Conflicts of Interest: The authors declare no conflict of interest. b. The color of smoked gewang wood differed in color from unsmoked samples. c. Unsmoked samples of gewang wood from the inner part were more susceptible to attack by dry- References wood termite and fungal attacks than the outer part. d.1. SmokeMinistry treatment of Environment was very and effective Forestry. forStatistic the inner of Forestry part, Production enhancing in 2018resistance; Ministry to dry-wood of Environment termite and andForestry: fungal Jakarta, attacks. Indonesia, 2019. 2. Flach, M.; Rumawas, F. Corypha utan L.; Resources of South East Asia (PROSEA) Foundation: Author Contributions: Conceptualization, D.N., W.D.; Data Curation, I.B.A., W.D., L.K.; Investigation Bogor, Indonesia, 1996; pp. 169–170. Resources, Y.S.H. and S.H.; Writing-review and editing, D.N., Y.S.H., S.H., I.B.A. All authors have read and 3. Irawanto, R. Distribution study of Corypha utan Lamk. from Herbarium Bogorienses specimens and the agreed to the published version of the manuscript. conservation areas in East Java. In Proceedings of the 4th International Conference on Global Resource Funding:Conservation Indonesian & Ministry 10th Indonesian of Education Society and Culture for Plant throug Taxonomyh Priority Congress, Basic Research Proceeding of the ICGRC, University Brawijaya Grant (PenelitianUniversity, Dasar Malang,Unggulan Indonesia, Perguruan 7–8 Tinggi) February Year 2013; 2020. pp. 135–144. Acknowledgments:4. Subyakto, S.; Prasetiyo, This research K.W.; was Subiyanto, a part of B.;Basic Naiola, Research B.P. PotentialYear 2020 biomass granted of by Gewang the Deputy (Corypha of Research utan Lamk.) and Developmentfor biocomposites. Strengthening, In Proceedings Ministry of of Research the 6th International and Technology, Woods the Science Republic Symposium: of Indonesia. Towards Ecology and Economy Harmonization of Tropical Forest Resources, Bali, Indonesia, 29–31 August 2005; p. 58. Conflicts of Interest: The authors declare no conflict of interest.

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