applied sciences Article Evaluation of Color Change and Biodeterioration Resistance of Gewang (Corypha 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, Indonesia; [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).