WOOD TREATMENT

Determining of wood treatment methodology for timber pallEts produced for the food industry

Background

Pallets are basically structures either made of wood or plastic or even sometimes metal based for steerage of food, transportation or even preservation of food items (Fink, Filip, Oder, and Jevšnik, 2013). The wooden pallets are more traditional ways for the same and largely used due to its light weight and long lastingness and durability. However, wooden pallets tend to have risks of getting infected by moulds and eaten away by insects or even dampened by moist and air(Manu et. al., 2019). Therefore, these wooden pallets are treated using different methods, mainly chemical and organic methods. However, with increased awareness to become environmentally sustainable and protection of the stored and preserved food from chemicals used for treatment of the wooden pallets, organic treatment methods are used as well as alternative pallets made of plastics are used (Amin, Wu, and Karaphillis, 2018). Therefore, the main aim of the current study is to reviewdifferent organic wood treatment methods for wooden pallets used in food industry.The aim can be further categorised into the following objectives for better addressing the aim of the study. The objectives are;

  • To review the organic wood treatment methods used against moulds.
  • To find the organic wood treatment methods used against insects.
  • To compare the advantages and disadvantages of wooden pallets against plastic pallets in food industry.

The current study aims to review different organic wood treatment methods for wooden pallets used in food industry. In the recent years, the use of plastic pallets have increased due to various reasons like; low cost, durability, environmental reason, and low maintenance costs amongst others. Therefore, the scope of the study is to help to explore the advantages and disadvantages of using plastic pallets against wooden pallets. Again, it has also been found from literature that with awareness on food toxicity and environmental protection the use of organic treatment methods are more of a modern approach for protection against moulds and insects. The study will therefore identify different organic treatment methods used in cases of wooden or timber pallets especially in food storage, transportation and preservation.

Literature review

Risk factors of wooden pallets

Wood have risks from weathering, moisture and air, insects, rotting, fungi and a few others to name. Decay of wood by fungi is caused by exposure to cold, dark and moist places and the decay mainly takes place in the softer section of the wooden pallet (Zabel and Morrell, 2012). Wood pallets in location without ventilations and damp areas are the most preferred for germination of fungi. The decay from fungi is usually identified from the changed colourisation of the wood and the wood tends to be brittle. Similarly, in cases of timber pallets, the decay area is identified by softness of the wood and the colour of the wood also changes as well as the wood starts to shrink and also circular structure called moulds (Salem, Zidan, Mansour, El Hadidi, and Elgat, 2016). Again, fungi growth according to Salem et. al., (2016) is contributed by temperature, air and water contact. Under favourable conditions the fungigrow on sapwoods and then germinate leading to decay of the wood. Again, according to Querner, (2015) the risk of insects is high especially for insects that feeds on wood sap like termites, beetles, fungus feeders, ants, and moths amongst others. These insects mainly feed through the inner portion of the timber which is softer and highly nutritious for these categories of insects. The identification of the insect attacks are seen by small pin shaped holes and the formation of apowdery frass(Allen, Noseworthy, and Ormsby, 2017). Allen et. al., (2017) also indicated that some of the insects lay eggs in the softer sections of the wood and even feed on the fungus, and can be identified through certain sound and dryness of the wood. Apart from insects and fungi, wood is highly flammable when in contact with fire and even have risks from high weathering due to climatic conditions and moisture (Wang, Chen, Tsang, Poon, and Shih, 2016).

Wood treatment methods

Wood treatment is commonly termed as wood preservation techniques which mainly comprises of “oily type such as creosote”, “organic solvent type”, “non-fixed water soluble” and “fixed water soluble” (Richardson, 2002). Creosote oil mainly comprises of coal tar that has been proven to be a good preservative against “borers, termites, decay and marine organisms” and has been seen to be effective against leaching due to water contact and is mainly treated with a mix of pentachlorophenol. The process by which this method is used is called “pressure treatment processes” where the creosote is pressed into the untreated wood and the exposed to rain or moisture and pressed until the surplus creosote does not ooze out of the wood (Murphy and Brown, 2005). On the other hand, the technique of Water borne uses metallic salts and presses the wood so that the salts get fixed to the surface of the wood.

They are mainly classified as Non Fixed and Fixed, whereby, in case of non-fixed the common chemical preservatives comprises of borax and boric acid, mercuric chloride, and zinc sulphate (Jinzhen, 2006). Again, in case of fixed type, common chemical used are Copper-Chrome-Arsenic salts, salts of Chromated Zinc Chloride, Copper Chrome Phosphorous and others (González-Laredo et. al., 2015).Copper-Chrome-Arsenic salts are mostly found in crystalline powders or concentrates and treated on the cracks and the holes of the wood inspected with insect attacks or mould formation. The salts act on the holes and kill the fungus or the insects. This method has also been very effective in extreme condition like submerged wood and water cooling towers and the treatment method is known as “leaching” (Hingston, Collins, Murphy, and Lester, 2001).Again, for organic methods mainly uses plant enzymes and secondary compounds like; quinones, flavonoids, resins, tannins and others(Borges, Tonoli, Cruz, Duarte, and Junqueira, 2018).Various studies have used lindane and dieldrin to avoid the attack from insects and fungi as wood treatment plan and the system used is trough superficial application like alloying as paint on the surface and immersion in the solutions of “tributyl tin oxide (TBTO), copper 8-quinolinolate and copper napthenate.”

Plastic pallets

Plastic pallets are mainly constructed using recycled plastics and have been found to be lighter and more durable (Amin et. al., 2018). The use of plastic pallets have increased especially in cases of long distance food transportations hand have been found to have low maintenance costs unlike wooden pallets. The plastic pallets have been found to not require any type of chemical or organic treatments and can be designed in any forms. The use of plastic pallets is mainly seen in the meat industry, packaging units of water and beverages and a few other processed food companies (Bush and Araman, 1998). In many cases, plastic are mixed with resin and other materials to give attractive structures for application in wood storage and preservation and transportation. However, Boersig and ClIvER, (2010) indicated that the costs of plastic pallets are higher than wooden pallets and have issue with respect to recyclability of the same. However, with increasing changes in technology and the demand for more durable storage units have led to the use of plastic pallets and others.

Methodology

The current study main objectiveswere to review different organic methods used against fungi and insects. In addition, another objective was to differentiate between the plastic and timber pallets used in food industry. In this regard and exploratory study was conducted whereby the study design is based on qualitative framework. The qualitative framework relied on identification and synthesis of different papers to address the objectives of the study (Camic, Rhodes, and Yardley, 2003). Therefore, a systematic method was used to address the study objectives. Since a systematic method was used, the research methods mainly comprised of inclusion and exclusion of papers and systematically finding the paper and presenting the findings (Smith, Devane, Begley, and Clarke, 2011). In order to find the relevant papers for the study, the study used different libraries to find relevant papers.

However, the search was done in two segments, one for the organic treatment methods for timber pallets and the other for difference between wooden and plastic pallets. However, the libraries for both the aspects were the same where Google Scholar was used. Different keywords were used for both the sections (Smith et. al., 2011); in case of organic treatment methods the keywords; ‘organic wood treatment techniques’, ‘organic wood preservation techniques against insects and fungi PDF’, and ‘organic wood treatment techniques insects moulds fungi PDF.’ On the other hand, in case of differences, the keywords used were; ‘advantages and disadvantages of using plastic pallets PDF’, ‘advantages and disadvantages of using timber/wooden pallets PDF’ and ‘plastic pallets against wooden pallets PDF.’

The synthesis of the papers was based on the inclusion and exclusion criteria. The inclusion criteria were;

  • All papers published in English and can be review articles or analytical or even conference papers
  • Papers post 2000 will be included in the study
  • Papers only using organic compounds for the treatment and preservation of wood pallets or wood structures
  • Papers that define plastic as well as wooden/timber pallet advantages and disadvantages

The exclusion criteria were;

  • Any paper with only abstract and full paper not accessible
  • Any paper that mentions use of organic chemicals or any form of chemical compounds for preservation and treatment
  • Papers that do not discusses the advantages or disadvantages of plastic or wooden pallets

Results and discussions

Organic methods against insects and fungi

Based on the current table 1, it can be seen that various papers have described the efficacy of using organic compounds extracted from natural sources and tree or plant extracts as biocides against insect and fungi decay on wood pallets. Most commonly used compounds were TBTO, Flavonoids, Copper napthenate, Copper 8-quinolinolate, tree oils and others. The common method or technique used were mainly mixing with different compounds and then rinsing them as fumigant to gas the wood with biocides.

Table 1: Review of organic compounds used

ReferenceOrganic compound usedPreservation againstEffectivenessComment
Osman and van Loveren, 2012tributyl tin oxide (TBTO)Beetles, shipworms, termites, Bees, and FungiHigh“TBTO is used because they have low viscosities and are able to penetrate rapidly into dry wood and help to cause toxicity to insects.”
Ermeydan, Cabane, Masic, Koetz, and Burgert, 2012FlavonoidInsects and weatheringHigh“Flavonoids reduce the water uptake of the wood cell walls and increased the dimensional stability of the bulk spruce wood and helps to reduce the infestation by insects”
Sander, Beckers, Militz, and Van Veenendaal, 2003ResinsInsects and FungiModerate“Use of resin with mix of lignin-rich structures helps to protect the wood structurein the middle lamellas and cell corners against insects and fungi growth”
Yalcin and Ceylan, 2017TanninsFungi, insects, and termitesHigh“Tannins are very effective in preservation of wooden materials especially against wood decay from fungi, damp and insects”
Green III and Clausen, 2005Copper napthenateFungi (mainly brown-rot fungi)High“The organic compound prevented decay, and has efficacy of the co-biocides against copper tolerant fungi”
Freeman and McIntyre, 2008Copper 8-quinolinolateFungi and insectsModerate“The treatment method has shown efficacy against copper compounds and against the decay by algal, antifouling pigments, and crop fungicides”
Hsu, Chang, and Chang, 2007CinnamaldehydeFungiModerate“the used of the organic compound when mixed with octylgallate exhibited antifungal property and enhanced wood protection”

Conclusions

The current study used an exploratory study was conducted whereby the study design is based on qualitative framework. The qualitative framework relied on identification and synthesis of different papers to address the objectives of the study. The findings are categorised into two sections; one was for the organic methods and the other was differences. The wooden pallets are more traditional ways for the same and largely used due to its light weight and long lastingness and durability. However, wooden pallets tend to have risks of getting infected by moulds and eaten away by insects or even dampened by moist and air. The study also indicates that with increased awareness to become environmentally sustainable and protection of the stored and preserved food from chemicals used for treatment of the wooden pallets, organic treatment methods are used as well as alternative pallets made of plastics are used. The findings of the study were also that organic compounds used in wood preservation areTBTO, Flavonoids, Copper napthenate, Copper 8-quinolinolate, tree oils and others that help effectively against decay from insects, fungi, and the environment. Similarly, significant differences like low-cost, durability, maintenance costs and others were identified as the main differences between plastic and wooden pallets.

References

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